Another Science Quiz

[The Lone Ranger]

Inspired by the “Could You Pass 8th Grade Science?” thread, I’ve made up some questions that are (hopefully) designed to test one’s understanding of some basic scientific principles. I don't like “tests” that test your test-taking ability rather than whether or not you actually understand the subject.

I’m not aiming at 8th-graders here, by the way; I figure these are concepts that should be understood by any “scientifically-literate” adult.



Having said that, this is just off the top of my head, so I’m not in any way pretending that this is a very good test. It’s just some things I came up with after a few moments’ thought; I’m sure plenty of people can think of better questions to add to the list. If, in my haste, I’ve worded something poorly or asked what seems like an unfair question, please feel free to say so, and I’ll see if I can correct it.

There is, of course, a good deal of overlap. The answer for one question may be closely-related to the answer for a different question.

I can, of course, post detailed answers to the questions later if anyone likes – though I doubt it’ll be necessary.



Questions Regarding Understanding of General Scientific Concepts:

Scientific inquiry usually involves generating and testing theories and hypotheses. Explain what a “hypothesis” and a “theory” are, and the differences between them. For extra credit, explain why the word “theory,” as used in the sciences, does not mean the same thing as it does in common usage.


Explain why the temperate and polar regions of the Earth have distinct seasons – and why seasonality is so much less pronounced in equatorial regions.


Explain the difference between nuclear fission and nuclear fusion. For bonus points, explain why each produces energy. For extra bonus points, explain why fusion of elements heavier than Iron does not produce energy.


Explain what is meant by radioactivity.


Explain the First Law of Thermodynamics and the Second Law of Thermodynamics. For bonus points, describe how it is that these two principles explain why we have to eat.


Describe the basic structure of an atom.


Explain the differences between elements, compounds, and mixtures.


Explain the three main processes by which rocks form on Earth.


Explain the basic tenets of Darwin’s theory of Evolution through Natural Selection.


Describe the principle differences between the cells of plants and animals. For extra credit, compare and contrast the cells of plants and animals with those of fungi.


Explain the theory of Plate Tectonics, and how it relates to the Earth’s continents. For extra credit, describe how it explains the existence of volcanic chains and mountain ranges.


Explain what energy is, and in particular, the difference between kinetic energy and potential energy.


Explain the difference between prokaryotic cells and eukaryotic cells.


What process powers the Sun?


Explain the difference between covalent chemical bonds and ionic chemical bonds.



Some Thought Questions:

Assume you’re on a spaceship with a mass of 1,000 tons. The spaceship accelerates to 99.9% the speed of light. Explain what, if anything, happens to the mass of the spaceship (and everything inside it), and why. For extra credit, can you accelerate the spacecraft the remaining 0.1% to the speed of light? Why or why not?


Assume you have an identical twin. You are a passenger on the spacecraft in the question above, but your twin remains behind on Earth. If you travel at 99.9% the speed of light for 10 years by your reckoning, then return to Earth, are you and your twin still the same age? Why or why not?


You see a lightning strike in the distance. Why don’t you hear the thunder at the same moment?


Explain why large storms such as hurricanes rotate. Also, why do they rotate counterclockwise in the northern hemisphere, and clockwise in the southern hemisphere?


The planet Mercury has a great many craters on its surface, as does our Moon. The planets Venus and Earth have very few visible craters. Mars has an intermediate number of visible craters. Explain the origins of these craters, and why the number of visible craters differs from one body to another.


If you have a mass of 80 kilograms, you weigh about 176 pounds when standing on the surface of the Earth. Explain what would happen to your mass and weight if you were standing on the surface of the Moon.


Imagine an ecosystem that contains just one species, called a Snoggle. Female snoggles give birth to numerous baby snoggles, each of which has a large yolk sac that provides it with food as it grows. Of course, another way to get food is to catch and eat other snoggles. Is this a workable ecosystem? Why or why not?


Imagine a bomb is sitting on your kitchen table. At the moment, it isn’t moving relative to you, so its momentum is 0. Then it explodes. Since you happen to have superhuman speed and reflexes, not to mention very precise measuring equipment, you have the ability to measure the momentum of each fragment of the exploding bomb. When you add up their total momentum, what is it?


If you go into any terrestrial ecosystem and add up the total mass of living matter in that ecosystem (the biomass), you’ll find that the plants greatly outweigh the animals. Why must this be true?


Suppose you’re floating in outer space, far from any source of gravity. An evil villain has disabled the thruster jets on your spacesuit, and you’re floating 100 meters away from your spaceship. Your air supply is running out. Fortunately, you happen to have a rubber ball in your pocket. How can you use it to reach your spaceship?


Giraffes are famous for their long necks. One explanation is that the ancestors of modern giraffes had short necks, which they stretched in order to reach leaves. Consequently, the offspring of these proto-giraffes had slightly longer necks than did their parents. Each generation, giraffes stretched their necks to more efficiently reach tasty leaves, and so each generation, giraffes had longer necks, eventually leading to modern, long-necked giraffes. Explain why this explanation fails.


You’re standing on a tower on the surface of the Moon. You drop a steel ball-bearing and a steel cannonball at the same time. Which hits the ground first, and why? Now you repeat the experiment, but you substitute a feather for the ball-bearing. Which hits the ground first, the feather or the cannonball, and why?


I’ve designed a machine. The way it works is that a sloped ramp supports a heavy steel ball. Atop a tower, a powerful magnet attracts the ball, pulling it up the ramp. When the ball reaches the top of the ramp, it falls through a hole in the ramp. As the ball falls, it turns a rotor, generating energy. When the ball falls to the bottom of the machine, it lands on the ramp again. Because the ramp supports the ball, the magnet can pull it back to the top of the ramp. Can this machine work, and can it generate usable energy? Explain why or why not.


A solar eclipse occurs only when there is a new moon. A lunar eclipse occurs only when there is a full moon. Explain why this must be true.


When you observe a star or distant galaxy through a telescope, you are not seeing it as it is now. You’re seeing it as it was in the past. Explain why this is necessarily so.


Suppose you’re standing on the surface of the Moon and you have a rifle. You orient the rifle so that it’s parallel to the surface and exactly 1 meter above the surface. In your left hand, you’re holding a bullet exactly 1 meter above the surface. You pull the trigger of the rifle at exactly the same moment you drop the bullet you’re holding in your left hand. Which bullet hits the ground first, and why? [Yes, a standard rifle will fire in a vacuum; it’s not a trick question. Gunpowder contains its own oxidant, and does not require surrounding air in order to burn.]


Suppose you live on the west coast of a continent. A range of high mountains extends down the coast, just a few miles inland. You notice that west-facing slopes of the mountains are lush and green, but the east-facing slopes are much drier. Why is this so?


Moss plants dry out easily, and can be killed by direct exposure to intense sunlight. Also, mosses can reproduce only when wet. How does this explain why you’re more likely to find moss growing on the north-facing side of a tree than the south-facing side? Hint: Is this true in the Southern Hemisphere?



Cheers,

Michael

[Dingfod]

I don't know how you wanted this done, as a discussion, or as individual entries like this or by PM to you for grading (heh-heh).

1. Scientific inquiry usually involves generating and testing theories and hypotheses. Explain what a “hypothesis” and a “theory” are, and the differences between them. For extra credit, explain why the word “theory,” as used in the sciences, does not mean the same thing as it does in common usage.
A hypothesis is a plausible explanation for observed phenomenon or a correlation between phenomenon. A theory is a logically testable or falsifiable explanation of an observed phenomenon. In common usage theory is just speculation or opinion.

2. Explain why the temperate and polar regions of the Earth have distinct seasons – and why seasonality is so much less pronounced in equatorial regions.
The rotational axis tilt of the earth causes shorter daylight periods during winter and longer ones during summer. During equinoxes daylight and darkness periods are equal. This is less pronounced the closer one is to the equator because the differences are less the closer you are to the equator and none at the equator.


3. Explain the difference between nuclear fission and nuclear fusion. For bonus points, explain why each produces energy. For extra bonus points, explain why fusion of elements heavier than Iron does not produce energy.Nuclear fission is when an atom's nucleus is split into two smaller nuclei, fusion is when two nuclei are fused into one. Fission is exothermic, emitting electromagetic radiation, photons, free neutrons, and other subatomic particle byproducts in the process. Fusion requires energy to take place, but in lighter elements more energy is released by the displacement of protons in the nuclei than is required, the lighter the element, the more energy produced.


4. Explain what is meant by radioactivity.
Energy in the form of subatomic particles is emitted by elements, if these particles in the form of waves react with other atoms it is commonly known as radiation.


5. Explain the First Law of Thermodynamics and the Second Law of Thermodynamics. For bonus points, describe how it is that these two principles explain why we have to eat.
Don't kill me for this one.
I'm not real clear on laws of Thermodynamics, only that you can't get more heat out of something than is put into it.
I have to eat because my stupid cells outnumber my smart ones and they're always hungry.

6. Describe the basic structure of an atom.
Protons and neutrons in the nucleus, electrons in orbit around the nucleus. The number of protons in an atom determine it's atomic number. Protons and neutrons represent most of the mass of an atom.


7. Explain the differences between elements, compounds, and mixtures.An element is a type of atom, defined by its atomic number, the number of protons in its nucleus, hydrogen is one. A compound is atoms chemically bonded, such as calcium carbonate (CaCO3). A mixture is any mixture of elements and or compounds, such as salt water, H2O and NaCl.


8. Explain the three main processes by which rocks form on Earth.
Volcanic eruptions (igneous), sedimentary (layers upon layers upon layers of sediments so thick pressures create rock from them), and rocks that are changed in form by pressure and temperature (metamorphic).

9. Explain the basic tenets of Darwin’s theory of Evolution through Natural Selection.
Extremely basic: the fittest survive conditions pass on the genes for whatever enabled them to survive on to succeeding generations.

More later. Mind you, I'm educated only by the public school system of a small city in the Texas Panhandle and whatever I've learned on my own with only a casual interest over the ensuing 30+ years.

[Julie]

I'm in...but will give my answers later tonight when I don't have kids around!

[Dingfod]

10. Describe the principle differences between the cells of plants and animals. For extra credit, compare and contrast the cells of plants and animals with those of fungi.

I need further education on this. I don't know.

11. Explain the theory of Plate Tectonics, and how it relates to the Earth’s continents. For extra credit, describe how it explains the existence of volcanic chains and mountain ranges.
Plate Tectonics is the theory that the solid crust of Earth and the upper more solid portion of the mantle floats on more viscous mantle below. It is solid by any definition, but viscous enough to allow movement on a geological time scale. These movements explain some evidence that the continents, or plates, have drifted over millions or billions of years to their present position.


12. Explain what energy is, and in particular, the difference between kinetic energy and potential energy.
Forgive my mental rust. Energy is the ability to do work. Kinetic energy is the energy or momentum of a moving object. Potential energy is the energy required to move an object at rest.

13. Explain the difference between prokaryotic cells and eukaryotic cells.

:shrug: More biology needed.


14. What process powers the Sun?
Atomic fusion of hydrogen.


15. Explain the difference between covalent chemical bonds and ionic chemical bonds.
Covalent bonds are when there are when pairs of electrons are shared between atoms. Ionic bonds are more of a magnetic bond, atoms held together by electrons of opposite charges.

[Dingfod]

Some Thought Questions:

Assume you’re on a spaceship with a mass of 1,000 tons. The spaceship accelerates to 99.9% the speed of light. Explain what, if anything, happens to the mass of the spaceship (and everything inside it), and why. For extra credit, can you accelerate the spacecraft the remaining 0.1% to the speed of light? Why or why not?

Mass would not change, but you would experience length contraction and time dilation. You cannot accelerate the spacecraft the remaining 0.01% because it would take an infinite amount of energy.

Michael, for my and other's edification, explain why lab experiments that show laser beams fired through Cesium atoms go faster than the speed of light, up to 300*c.


Assume you have an identical twin. You are a passenger on the spacecraft in the question above, but your twin remains behind on Earth. If you travel at 99.9% the speed of light for 10 years by your reckoning, then return to Earth, are you and your twin still the same age? Why or why not?
Theoretically I would be younger than my earth-bound twin. It's that time dilation thing.


You see a lightning strike in the distance. Why don’t you hear the thunder at the same moment?
The speed of light far exceeds that of sound.


Explain why large storms such as hurricanes rotate. Also, why do they rotate counterclockwise in the northern hemisphere, and clockwise in the southern hemisphere?[/quote]
The Coriolis Effect imparts a rotation on the storm because of the rotation of the earth. The westward winds near the equator and the eastward winds more toward the poles impart an opposite rotation of the cyclones north or south of the equator.


The planet Mercury has a great many craters on its surface, as does our Moon. The planets Venus and Earth have very few visible craters. Mars has an intermediate number of visible craters. Explain the origins of these craters, and why the number of visible craters differs from one body to another.
Craters on planetary bodies are damage to the planet or moon surface from impacts from asteroids, meteors, and comets. Mars, Earth and Venus have atmospheres, the latter two much thicker atmospheres, which cause many of the approaching objects to burn up before striking the surface, the moons do not and show all impact craters that have ever occurred except where volcanic activity has covered them up. Additionally, Venus and Earth have plentify liquid precipitation erosion that mask or fill in impact craters, making them less visible than those on Mars.


If you have a mass of 80 kilograms, you weigh about 176 pounds when standing on the surface of the Earth. Explain what would happen to your mass and weight if you were standing on the surface of the Moon.
My mass would remain the same 80 kg, but my weight would only be 1/6th that of on earth, about 29 pounds. This is primarily due to the smaller mass of the moon exerting less gravitational pull on my mass than the mass of Earth would.

Imagine an ecosystem that contains just one species, called a Snoggle. Female snoggles give birth to numerous baby snoggles, each of which has a large yolk sac that provides it with food as it grows. Of course, another way to get food is to catch and eat other snoggles. Is this a workable ecosystem? Why or why not?
I would imagine not, and I bet it has something do to with some law of thermodynamics.

Imagine a bomb is sitting on your kitchen table. At the moment, it isn’t moving relative to you, so its momentum is 0. Then it explodes. Since you happen to have superhuman speed and reflexes, not to mention very precise measuring equipment, you have the ability to measure the momentum of each fragment of the exploding bomb. When you add up their total momentum, what is it?

I can't wait to hear the answer to that one.


If you go into any terrestrial ecosystem and add up the total mass of living matter in that ecosystem (the biomass), you’ll find that the plants greatly outweigh the animals. Why must this be true?
Again with the conservation of energy.

Suppose you’re floating in outer space, far from any source of gravity. An evil villain has disabled the thruster jets on your spacesuit, and you’re floating 100 meters away from your spaceship. Your air supply is running out. Fortunately, you happen to have a rubber ball in your pocket. How can you use it to reach your spaceship?
Throw the ball as hard as possible in the opposite direction of the spaceship, you will then move toward the space ship at a speed relative to the ratio of your mass to the mass of the rubber ball.


Giraffes are famous for their long necks. One explanation is that the ancestors of modern giraffes had short necks, which they stretched in order to reach leaves. Consequently, the offspring of these proto-giraffes had slightly longer necks than did their parents. Each generation, giraffes stretched their necks to more efficiently reach tasty leaves, and so each generation, giraffes had longer necks, eventually leading to modern, long-necked giraffes. Explain why this explanation fails.

God created giraffes to eat the leaves the other animals couldn't?


You’re standing on a tower on the surface of the Moon. You drop a steel ball-bearing and a steel cannonball at the same time. Which hits the ground first, and why? Now you repeat the experiment, but you substitute a feather for the ball-bearing. Which hits the ground first, the feather or the cannonball, and why?In a vacuum all objects would fall a the same speed (or close enough for government work*). *The mass of the objects would have an extremely minute impact on the moon's attraction to them.


I’ve designed a machine. The way it works is that a sloped ramp supports a heavy steel ball. Atop a tower, a powerful magnet attracts the ball, pulling it up the ramp. When the ball reaches the top of the ramp, it falls through a hole in the ramp. As the ball falls, it turns a rotor, generating energy. When the ball falls to the bottom of the machine, it lands on the ramp again. Because the ramp supports the ball, the magnet can pull it back to the top of the ramp. Can this machine work, and can it generate usable energy? Explain why or why not.
Due to frictional losses and electrical generation inefficiencies the machine could never generate more energy than it uses.


A solar eclipse occurs only when there is a new moon. A lunar eclipse occurs only when there is a full moon. Explain why this must be true.
The moon is at it's closest to the sun every new moon, that is why we only see a sliver of a reflection of the moon from Earth. When the moon's orbit gets between the sun and Earth it casts a shadow on Earth. A full moon occurs when the moon is at it's furthest point from the sun in its orbit, exposing the full reflection of the sun to viewers on Earth. When the moon falls into Earth's shadow you have a lunar eclipse.


When you observe a star or distant galaxy through a telescope, you are not seeing it as it is now. You’re seeing it as it was in the past. Explain why this is necessarily so.
Because of the time it takes for light to travel from there to here.


Suppose you’re standing on the surface of the Moon and you have a rifle. You orient the rifle so that it’s parallel to the surface and exactly 1 meter above the surface. In your left hand, you’re holding a bullet exactly 1 meter above the surface. You pull the trigger of the rifle at exactly the same moment you drop the bullet you’re holding in your left hand. Which bullet hits the ground first, and why? [Yes, a standard rifle will fire in a vacuum; it’s not a trick question. Gunpowder contains its own oxidant, and does not require surrounding air in order to burn.]
If there's no change in elevation the bullet fired from the gun will strike the surface of the moon at exactly the same time as the bullet dropped the same 1 meter, providing it isn't imparted with orbital velocity when it's fired. Ignore that last part. I've asked this same question about bullets fired on Earth.


Suppose you live on the west coast of a continent. A range of high mountains extends down the coast, just a few miles inland. You notice that west-facing slopes of the mountains are lush and green, but the east-facing slopes are much drier. Why is this so?
The mountains cause much of the moisture to fall out, leaving the leeward side with much less precipitation. That is because as the air rises over the mountains it loses pressure, which means it also loses temperature and its ability to hold water in its vapor state. [see also: Chinooks]


Moss plants dry out easily, and can be killed by direct exposure to intense sunlight. Also, mosses can reproduce only when wet. How does this explain why you’re more likely to find moss growing on the north-facing side of a tree than the south-facing side?
Because the north side of the tree remains in the shade for more of the day than the south side.
Hint: Is this true in the Southern Hemisphere?
Yes, except it would be on the south side.

[Kyuss Apollo]

Yes!

Very cool, but if I answer these now I'll probably still be here when my wife gets back from the YMCA rather than meeting her there.

I'll be back! :term:

[JoeP]

Great stuff Michael, but I wanted a multiple choice quiz! And a fancy logo to put on my web page with my score! And a pony!


Well, I couldn't get all of them, but I hope I got enough to pass:

Questions Regarding Understanding of General Scientific Concepts:

Scientific inquiry usually involves generating and testing theories and hypotheses. Explain what a “hypothesis” and a “theory” are, and the differences between them. For extra credit, explain why the word “theory,” as used in the sciences, does not mean the same thing as it does in common usage.

A "hypothesis" is flat-out wrong, and a "theory" is something which has not been proven yet and therefore should not be taught in schools.


Explain why the temperate and polar regions of the Earth have distinct seasons – and why seasonality is so much less pronounced in equatorial regions.

The earth's orbit takes it closer to the sun at some times of the year, which causes the seasons. They are less pronounced at the equator because of the extra cloud there.


Explain the difference between nuclear fission and nuclear fusion. For bonus points, explain why each produces energy. For extra bonus points, explain why fusion of elements heavier than Iron does not produce energy.

Pass


Explain what is meant by radioactivity.

Political lobbying via radio programmes, traditionally a left-wing thing in 20th-C Europe, but now dominated by the American right-wing.


Explain the First Law of Thermodynamics and the Second Law of Thermodynamics. For bonus points, describe how it is that these two principles explain why we have to eat.

The first law: You can't win, you can only break even.
The second law: You can only break even at the absolute zero of temperature.
After all that gambling in the cold, of course we have to eat!


Describe the basic structure of an atom.

Atoms have a spherical nucleus like a ping-pong ball and six electrons like ball-bearings that whizz round in elliptical orbits arranged in a six-pointed star.


Explain the differences between elements, compounds, and mixtures.

Compounds are sold in reputable pharmacies, while mixtures are made at home.


Explain the three main processes by which rocks form on Earth.

Carving, moulding and terms in political office.


Explain the basic tenets of Darwin’s theory of Evolution through Natural Selection.

The existence of tenets has never been proven.


Describe the principle differences between the cells of plants and animals. For extra credit, compare and contrast the cells of plants and animals with those of fungi.

Plant cells are made of wood and animal cells are made of meat.

Fungal cells are the same but rotten.


Explain the theory of Plate Tectonics, and how it relates to the Earth’s continents. For extra credit, describe how it explains the existence of volcanic chains and mountain ranges.

Each time a volcano erupts, or a mountain is formed, or a coastline changes, a commemorative plate is created. Science has no explanation for why people collect these plates.


Explain what energy is, and in particular, the difference between kinetic energy and potential energy.

Kinetic energy is energy you have actually used. Potential energy is the amount the power company needs you to use to make up their numbers, and thus charges you for anyway.


Explain the difference between prokaryotic cells and eukaryotic cells.

Prokaryotic cells are used before trial, unless your lawyer can get you into one the plush eukaryotic cells.


What process powers the Sun?

Duracell.


Explain the difference between covalent chemical bonds and ionic chemical bonds.

Ionic bonds have a simple disc-like appearance while covalent bonds are decorated with floral patterns.



Some Thought Questions:

Assume you’re on a spaceship with a mass of 1,000 tons. The spaceship accelerates to 99.9% the speed of light. Explain what, if anything, happens to the mass of the spaceship (and everything inside it), and why. For extra credit, can you accelerate the spacecraft the remaining 0.1% to the speed of light? Why or why not?

The mass is reduced by the amount of fuel use to do it. The mass of the occupants is reduced by sweating (and vomiting and ...) due the stress, because this has never been done before.


Assume you have an identical twin. You are a passenger on the spacecraft in the question above, but your twin remains behind on Earth. If you travel at 99.9% the speed of light for 10 years by your reckoning, then return to Earth, are you and your twin still the same age? Why or why not?

The twin has spent the entire time on TV shows as a celebrity and on Oprah talking about his abandonment, and has sun-damaged skin due to his unaccustomed jet-setting lifestyle, plus plastic surgery. It's no longer possible to tell what age he is.


You see a lightning strike in the distance. Why don’t you hear the thunder at the same moment?

This could be due to various factors. You could have the sound turned down, or there could be a fault in the broadcasting equipment.


Explain why large storms such as hurricanes rotate. Also, why do they rotate counterclockwise in the northern hemisphere, and clockwise in the southern hemisphere?

It's a coincidence.


The planet Mercury has a great many craters on its surface, as does our Moon. The planets Venus and Earth have very few visible craters. Mars has an intermediate number of visible craters. Explain the origins of these craters, and why the number of visible craters differs from one body to another.

They were always like this.


If you have a mass of 80 kilograms, you weigh about 176 pounds when standing on the surface of the Earth. Explain what would happen to your mass and weight if you were standing on the surface of the Moon.

You would be much heavier because you'd need a spacesuit.


Imagine an ecosystem that contains just one species, called a Snoggle. Female snoggles give birth to numerous baby snoggles, each of which has a large yolk sac that provides it with food as it grows. Of course, another way to get food is to catch and eat other snoggles. Is this a workable ecosystem? Why or why not?

It would not be workable, because some yolk sacs would inevitably used to make fried eggs, cake and other products.


Imagine a bomb is sitting on your kitchen table. At the moment, it isn’t moving relative to you, so its momentum is 0. Then it explodes. Since you happen to have superhuman speed and reflexes, not to mention very precise measuring equipment, you have the ability to measure the momentum of each fragment of the exploding bomb. When you add up their total momentum, what is it?

Some of the bomb would turn to gaseous matter (rather than solid fragments), which you don't have the equipment to measure, so you run very fast to the ice-cream parlour instead.


If you go into any terrestrial ecosystem and add up the total mass of living matter in that ecosystem (the biomass), you’ll find that the plants greatly outweigh the animals. Why must this be true?

The plants have eaten most of the animals.


Suppose you’re floating in outer space, far from any source of gravity. An evil villain has disabled the thruster jets on your spacesuit, and you’re floating 100 meters away from your spaceship. Your air supply is running out. Fortunately, you happen to have a rubber ball in your pocket. How can you use it to reach your spaceship?

You rub the ball energetically on a fabric part of your spacesuit. This creates static electricity. You hold it the direction of the spaceship. The small electrostatic force differential tugs you towards your ship.


Giraffes are famous for their long necks. One explanation is that the ancestors of modern giraffes had short necks, which they stretched in order to reach leaves. Consequently, the offspring of these proto-giraffes had slightly longer necks than did their parents. Each generation, giraffes stretched their necks to more efficiently reach tasty leaves, and so each generation, giraffes had longer necks, eventually leading to modern, long-necked giraffes. Explain why this explanation fails.

The giraffes that stretched their necks this way would be quite sore, and would be saying "Not tonight dear, I have a neck-ache" more often than the others, and would thus die out relative to the other giraffes.


You’re standing on a tower on the surface of the Moon. You drop a steel ball-bearing and a steel cannonball at the same time. Which hits the ground first, and why? Now you repeat the experiment, but you substitute a feather for the ball-bearing. Which hits the ground first, the feather or the cannonball, and why?

The cannonball. The feather lands on top of the ball-bearing from the first experiment and technically never hits the ground at all.


I’ve designed a machine. The way it works is that a sloped ramp supports a heavy steel ball. Atop a tower, a powerful magnet attracts the ball, pulling it up the ramp. When the ball reaches the top of the ramp, it falls through a hole in the ramp. As the ball falls, it turns a rotor, generating energy. When the ball falls to the bottom of the machine, it lands on the ramp again. Because the ramp supports the ball, the magnet can pull it back to the top of the ramp. Can this machine work, and can it generate usable energy? Explain why or why not.


A solar eclipse occurs only when there is a new moon. A lunar eclipse occurs only when there is a full moon. Explain why this must be true.


When you observe a star or distant galaxy through a telescope, you are not seeing it as it is now. You’re seeing it as it was in the past. Explain why this is necessarily so.

Only telescopes owned by the major satellite networks show objects in real time, and as a scientist you're not able to afford one. Other telescopes have a delay built in.


Suppose you’re standing on the surface of the Moon and you have a rifle. You orient the rifle so that it’s parallel to the surface and exactly 1 meter above the surface. In your left hand, you’re holding a bullet exactly 1 meter above the surface. You pull the trigger of the rifle at exactly the same moment you drop the bullet you’re holding in your left hand. Which bullet hits the ground first, and why? [Yes, a standard rifle will fire in a vacuum; it’s not a trick question. Gunpowder contains its own oxidant, and does not require surrounding air in order to burn.]

For 99% of the population it is impossible to coordinate opening the fingers of the left hand while squeezing the trigger of a rifle - you tense up expecting the recoil. Precisely what happens depends on the individual, of course!


Suppose you live on the west coast of a continent. A range of high mountains extends down the coast, just a few miles inland. You notice that west-facing slopes of the mountains are lush and green, but the east-facing slopes are much drier. Why is this so?

The eastern slopes have been denuded by logging and/or intensive commercial grazing, whereas the western slopes are protected because all the well-connected and well-off dudes have their luxury house on the ocean-facing side.


Moss plants dry out easily, and can be killed by direct exposure to intense sunlight. Also, mosses can reproduce only when wet. How does this explain why you’re more likely to find moss growing on the north-facing side of a tree than the south-facing side?

The moss on the southern side has been scraped off by deer and other animals rubbing on the warmer, drier side of the tree.

Hint: Is this true in the Southern Hemisphere?

Trick question - mosses do not grow in the Southern Hemisphere!



Cheers,

Joe

[davidm]

I’ve no idea what Dingfod is on about. Joe P’s answers look pretty good, but I noticed a few howlers.

Explain what is meant by radioactivity.

Political lobbying via radio programmes, traditionally a left-wing thing in 20th-C Europe, but now dominated by the American right-wing.

A widespread misconception. “Radioactivity” is a technical term meaning that one’s radio is both (a) turned on; and (b) in good working order. You have confused “radioactivity” with radioactivism.

Explain the basic tenets of Darwin’s theory of Evolution through Natural Selection.

The existence of tenets has never been proven.
I’ve no idea where you’re getting this. Tenets certainly exist; I, myself, am a tenet, because I can’t afford to buy a home. Large-scale housing projects where tenets congregate are technically known as tenetments.

Granted, the question as phrased is a bit obscure; I didn’t know that Darwin’s theory had rental units, so I’ve no clue what its tenets are like.
Explain why the temperate and polar regions of the Earth have distinct seasons – and why seasonality is so much less pronounced in equatorial regions.

The earth's orbit takes it closer to the sun at some times of the year, which causes the seasons. They are less pronounced at the equator because of the extra cloud there.

You seem confused here. Polar food — stuff like pierogies, kielbasa and cabbage — just automatically lends itself to plenty of salt, pepper and other seasons. By contrast, Equatorials, residents of Equator, eat spicy tacos and such that are already pre-seasoned, and hence they don’t need to add seasons.

:shiftier:

Anyway, later on I’ll take a crack at Question 1, since, curmudgeon that I am, I have doubts about the usual scientific description of hypothesis and theory; or rather, I think these descriptions don’t capture the complexity of the matter. But before I address this, my injured hand will have to heal, so I can type better. :sadcheer:

[The Lone Ranger]

<snipped for brevity>

:foocl:


Don’t sell yourself short, Dingfod! You’ve done quite well!

I’ll go ahead and post some explanations myself. If you want to take the test for yourself, don’t click on the spoilers!





Questions Regarding Understanding of General Scientific Concepts:

Scientific inquiry usually involves generating and testing theories and hypotheses. Explain what a “hypothesis” and a “theory” are, and the differences between them. For extra credit, explain why the word “theory,” as used in the sciences, does not mean the same thing as it does in common usage.
Both hypotheses and theories are testable explanations for observed phenomena. The difference is that hypotheses are basically “educated guesses” that have had little or no testing. A theory has been thoroughly-tested and has (so far) passed all of the tests thrown at it – thus it’s very likely to be a correct explanation. Technically, you can never prove a theory correct, but the more thoroughly it has been tested, the more confident we are that it is an accurate explanation.

In common parlance, as Dingfod so succinctly put it, a theory “is just speculation or opinion.”


Explain why the temperate and polar regions of the Earth have distinct seasons – and why seasonality is so much less pronounced in equatorial regions.
This is due to the fact that the Earth’s axis is tilted 23.5˚ from the perpendicular, relative to the Sun. Because of this, during the winter months, the Northern Hemisphere is pointed away from the Sun and so has shorter days and receives less sunlight. During the summer months, the Northern Hemisphere is pointed toward the Sun and so receives more sunlight. [Of course, this situation is exactly reversed for the Southern Hemisphere.]

On the equinoxes, the day/night lengths are equal. The vernal equinox marks the beginning of Spring, when the days start getting longer than the nights. The autumnal equinox marks the beginning of Autumn, when the nights start getting longer than the days.

The tropical regions do have varying day lengths and so they do have seasons, but because the Sun is always high overhead at midday, the seasonal variation is far less pronounced than it is in the temperate regions (regions more than 23.5˚ north or south of the equator) or the polar regions (regions less than 23.5˚ from either the North Pole or the South Pole), and the days and nights don’t vary much in length.

Seasonality has little to do with how close we are to the Sun. In fact, the Earth is closest to the Sun during the Northern Hemisphere winter.

Here’s a neat video illustrating the concept: link (http://sealevel.jpl.nasa.gov/gallery/tiffs/videos/seasons.mov)



Explain the difference between nuclear fission and nuclear fusion. For bonus points, explain why each produces energy. For extra bonus points, explain why fusion of elements heavier than Iron does not produce energy.
Nuclear fission occurs when an atomic nucleus is split into 2 or more smaller nuclei. Nuclear fusion occurs when two or more atomic nuclei are fused together.

For every element up to Iron (Atomic Number 26), the element in question is slightly less massive than are its component atoms. That is, I can make an atom of Beryllium (Atomic Number 4) by fusing together two Helium (Atomic Number 2) nuclei. But the beryllium atom that results weighs slightly less than the two helium atoms that made it up. As Einstein taught us, energy can be converted to matter and vice-versa (E=mc2), and so the “missing” mass is converted into energy and released. That’s why fusion reactions release energy – so long as the end result is an atom that’s less massive than is iron.

In the case of atoms heavier than iron, the succeeding atomic nuclei are more massive than their component atoms. So if, for example, I were to fuse a Helium nucleus (Atomic Number 2) to a Platinum nucleus (Atomic Number 78) to form a nucleus of Mercury (Atomic Number 80), the mercury atom would weigh more than the weights of the helium and platinum atoms. So, the reaction can only proceed by absorbing energy and converting some of it to matter.

This also explains why fission of heavy elements releases energy, but not fission of light elements. If you try to split a relatively light element, the atomic nuclei that result weigh more than the original nucleus, and so the reaction can proceed only if it absorbs energy and converts it to matter.

If you split a heavy atom – Uranium (Atomic Number 92), for example – depending upon what, exactly, you wind up with, the resulting atomic nuclei weigh less than the original nucleus, and so the “excess” mass is released in the form of energy.


Explain what is meant by radioactivity.
Radioactive atomic nuclei are unstable and prone to spontaneously lose energy in the form of particles and/or electromagnetic radiation. Usually, the loss of particles changes the atom to one of a different element – for instance, uranium undergoes radioactive decay that ultimately transmutes it to lead. This is true because it’s the number of protons that determines an atom’s identity. If the radioactive decay involves loss of protons (or, more rarely, gain of protons), the atom will change identities.

The most common byproducts of radioactive decay are alpha particles, beta particles, and gamma rays. Alpha particles are helium nuclei. Since each alpha particle consists of 2 protons and 2 neutrons, the atom’s atomic number goes down by 2 whenever it emits an alpha particle. Alpha particles are not too dangerous – they can be stopped by a sheet of paper. Beta particles are electrons. Release of electrons occurs when a neutral-charged neutron in the atom’s nucleus spontaneously changes to a positively-charged proton, releasing a negatively-charged electron in the process. (You’ve no-doubt noticed that beta decay causes the addition of a proton to the atom’s nucleus, so the atomic number goes up by one.) Beta particles are a bit more dangerous; they can penetrate clothing and skin, but are stopped by most metals or a concrete wall. Gamma rays are very high-energy electromagnetic radiation (photons), and are quite dangerous, since you need something like a thick sheet of lead to stop them.



Explain the First Law of Thermodynamics and the Second Law of Thermodynamics. For bonus points, describe how it is that these two principles explain why we have to eat.
There are a lot of ways to express them, but very basically, the two laws tell us how energy behaves. The First Law of Thermodynamics states that energy can be neither created nor destroyed; it can only change form. This means that the amount of energy in a closed system is constant, and energy is conserved. The Second Law of Thermodynamics tells us that whenever energy is transformed from one kind to another, some of the usable energy is always lost in the form of heat, etc. So, the amount of usable energy in a closed system always decreases over time (until it reaches zero, of course), even though the total amount of energy in the system is a constant.

These two laws are of supreme importance to living things, because it requires energy to build and maintain body tissues. But, since you lose energy (in the form of heat) when building and maintaining tissues, you must replace the lost energy in order to survive – so, you must eat. (Food supplies both the raw materials for building tissues and the energy used to assemble those raw materials into proteins, etc.)


Describe the basic structure of an atom.
An atom consists of a central, tightly-packed nucleus consisting of uncharged neutrons and positively-charged protons. The number of protons is the atom’s Atomic Number and determines its identity. For example, every atom with 6 protons in its nucleus is an atom of carbon, regardless of how many neutrons are present.

Surrounding the nucleus in “shells” or “orbitals” are the negatively-charged electrons. Each electron is relatively tiny (less than 1/1,800 the mass of a proton or neutron). Nonetheless, it’s the electrons that determine the chemical properties of the atom – virtually all chemistry boils down to interactions between the electrons associated with atoms.


Explain the differences between elements, compounds, and mixtures.
An element is a substance that contains one and only one kind of atom. The atoms may be chemically bonded – for example, oxygen atoms normally bond to each other to form molecules (O2) – but since there is only one kind of atom, it’s an element.

A compound is a substance made up of two or more different kinds of atoms that are chemically bound. Water (H2O) is a common example.

A mixture is a substance that contains more than one element and/or compound, but the different compounds/elements are not chemically bound. For instance, saltwater is a mixture; it contains salt and water, but the salt (NaCl) molecules are not chemically bound to the water (H2O) molecules.


Explain the three main processes by which rocks form on Earth.
Igneous rocks form from hardened magma or lava. Sedimentary rocks form when sediments laid down by wind, water, etc. are compressed and eventually harden into rock. Metamorphic rocks from when preexisting rocks are buried deep in the Earth; there, subjected to intense heat and pressure, they undergo chemical and/or physical changes into different forms of rock.


Explain the basic tenets of Darwin’s theory of Evolution through Natural Selection.
As Dingfod pointed out, the basic theory is extremely simple – which makes me wonder, at times, why Creationists seem to have such difficulty understanding it. Basically, the theory states that those organisms which happen to have been born with traits that make them well-suited to their environments are more likely to survive and reproduce than those organisms which happen to be born with less-advantageous traits. So, over time, the makeup of populations changes as advantageous traits become more common and disadvantageous traits become less common.

The fact that those individuals with advantageous traits are more likely to pass those traits on is called “natural selection.” The change in genetic makeup of populations that occurs as a result of natural selection is called “evolution.”


Describe the principle differences between the cells of plants and animals. For extra credit, compare and contrast the cells of plants and animals with those of fungi.
Plant cells are surrounded by rigid cell walls made of cellulose. In the vast majority of species, plant cells have green organelles called chloroplasts that contain the molecule chlorophyll, which they use to capture solar energy in photosynthesis. Their cell walls make plant cells more or less incapable of movement, which helps explain why trees are rarely seen running marathons.

Animal cells lack cell walls, which makes them capable of movement. They also lack chloroplasts, which makes them incapable of producing their own food.

Fungal cells are superficially similar to plant cells in that they’re surrounded by cell walls. However, the cell walls of fungal cells are made largely of chitin instead of cellulose. Internally, fungal cells are more similar to animal cells; like animal cells, they lack chloroplasts, and so fungi cannot make their own food.


Explain the theory of Plate Tectonics, and how it relates to the Earth’s continents. For extra credit, describe how it explains the existence of volcanic chains and mountain ranges.
Dingfod put it with admirable clarity: “Plate Tectonics is the theory that the solid crust of Earth and the upper more solid portion of the mantle floats on more viscous mantle below. It is solid by any definition, but viscous enough to allow movement on a geological time scale. These movements explain some evidence that the continents, or plates, have drifted over millions or billions of years to their present position.”

Convection currents in the mantle are thought to provide the force that causes the plates to move. When two plates are forced together, one of two things can happen. If one plate is forced under the other, it is subducted. (Since oceanic plates are denser than are continental plates, when an oceanic plate and a continental plate collide, the oceanic plate is usually subducted.) The subducted plate partially melts, and the molten material may make its way back to the surface in the form of volcanic eruptions. That’s why there are volcanic chains where oceanic plates and continental plates are colliding, such as along the West Coast of North America, for instance.

If neither plate is subducted, then both plates crumple, kind of like the crumpling of fenders in an immense, very slow-motion car crash. (This usually happens when two continental plates collide; neither subducts, and so both crumple.) Where the plates crumple like this, mountain ranges are formed. For instance, the Himalayas are the result of the collision of the India Plate with the Asia Plate.


Explain what energy is, and in particular, the difference between kinetic energy and potential energy.
Energy is defined as the ability to do work – that is, to move matter.

Anything that is in motion has kinetic energy. Potential energy is energy that is stored somehow. For instance, chemical bonds are potential energy (it takes energy to make chemical bonds; that energy is stored in the chemical bonds; when the bonds are broken, that energy is released). When you lift something (say, a baseball) against the force of gravity, you’re doing work; the energy you provide the baseball as you lift it is stored as potential energy. When you let go of the baseball, the potential energy stored in it is converted to kinetic energy, and it falls.


Explain the difference between prokaryotic cells and eukaryotic cells.
Prokaryotic cells lack nuclei or other well-defined organelles. Consequently, they’re relatively simple and small. Most prokaryotic organisms are bacteria.

Eurkaryotic cells have nuclei and other well-defined organelles, such as mitochondria, for instance. Eukaryotic cells are typically much larger than prokaryotic cells, and are much more complex. Protists, Fungi, Plants and Animals all have eukaryotic cells.


What process powers the Sun?
Nuclear fusion – specifically, fusion of hydrogen nuclei into helium nuclei.


Explain the difference between covalent chemical bonds and ionic chemical bonds.
Covalent bonds are formed when atoms share pairs of electrons. Water, for instance, forms when an oxygen atom shares electrons with 2 hydrogen atoms.

An ionic bond forms when one atom takes one or more electrons from another atom. The atom that has “stolen” an electron is now a negatively-charged ion (because electrons are negatively-charged, and it now has more electrons than protons), and the atom that lost an electron is now positively-charged (because it now has more protons than electrons). Since opposite charges attracted, the ions stick together. Table salt (NaCl) is a common example of an ionic compound. The chlorine takes an electron from the sodium, forming a sodium ion (Na+) and a chloride ion (Cl-); the sodium ion and the chloride ion then stick together because of their opposite charges.



Some Thought Questions:

Assume you’re on a spaceship with a mass of 1,000 tons. The spaceship accelerates to 99.9% the speed of light. Explain what, if anything, happens to the mass of the spaceship (and everything inside it), and why. For extra credit, can you accelerate the spacecraft the remaining 0.1% to the speed of light? Why or why not?
As you approach the speed of light, the spaceship becomes more massive. This is necessarily true because of E=mc2. Remember that it takes energy to move matter, but as you add energy to the spacecraft to make it move faster, it gains mass because energy is matter. (If the spacecraft isn’t accelerating, the occupants wouldn’t notice the additional mass, no matter how fast the spaceship was moving – even if it was moving at 99.9999% the speed of light.)

At normal speeds, the increase in mass with increased speed isn’t noticeable, but when your speed approaches the speed of light, the increased mass becomes a serious issue. As the craft speeds up, it becomes more massive. Since it’s more massive, it requires more energy to get any additional speed out of it. This becomes a vicious circle as you approach lightspeed.

As the craft approaches lightspeed, its mass approaches infinite. Obviously, it would require an infinite amount of energy to accelerate an infinitely massive object, and so it is not possible to accelerate any object that has mass to the speed of light – not even something as tiny as an electron. Only things like photons which have a “rest mass” of zero can travel at the speed of light.

***

There are instances in which something can appear to travel faster than light, but so far, no one has found an example of anything that actually does. Physicists are pretty sure that no one ever will.

Imagine a lighthouse with a rotating lamp. It projects a “beam” of light that appears to be rotating. In reality, though, the “beam” is made up of photons that are moving in straight lines. No photon, obviously, is moving faster than light. But, if the beam extends far-enough, it can look like the beam is moving faster than light.

How so? Suppose it takes the lamp in the lighthouse 1 second to complete a revolution. Now suppose you were standing at a point exactly 1 light-minute from the lighthouse (that would put you in interplanetary space, not too far from the orbit of the planet Venus, but I digress), and you have extremely sensitive eyesight, so that you can actually see the beam from the lighthouse. [One light-minute is the distance light travels in a minute, approximately 11,176,920 miles.] Suppose you have a friend with equally acute eyesight standing 1 light-minute from the lighthouse in the opposite direction.

Okay, when you see the beam of the lighthouse, your friend will see it only ½ second later. This creates the illusion that the beam is moving much faster than the speed of light, even though the photons that make it up are poking along at only the speed of light. But it is only an illusion. Nothing is actually moving faster than the speed of light, and there’s no way you could use this phenomenon to communicate information between you and your friend at faster-than-light speeds, because it would take a minimum of 2 minutes to get information between you. [For instance, it wouldn’t do you any good to radio a message to the lighthouse keeper for him to relay to your friend via alteration of the lighthouse beam. It would take 1 minute for the lighthouse keeper to receive your message, and even if he instantly altered the lighthouse beam upon receipt of your message, it would be another minute before your friend saw the alteration.]



I bring all of this up because when we talk about “the speed of light,” we’re really talking about the speed of light in a vacuum. When light moves through a medium (air, for instance), it appears to slow down. It doesn’t slow down, in reality, but it appears to. A photon always moves at c, the speed of light.

Why does light usually appear to slow down when moving through a medium such as air or water? Because, when you shine a beam of light through a medium, the molecules of the medium absorb the photons of light. Some time after it absorbs a photon, the molecule will release it. This delays the progression of the photons through the medium and creates the illusion that the photons are moving slower than c. (The more dense the medium, the more often the photons are absorbed and then re-released, and so the more slowly light will propagate through it.)

A really neat example of this sort of thing happened in 1987. In that year, a supernova became visible in the Large Magellanic Cloud, one of the two “dwarf galaxies” that orbits our own Milky Way Galaxy. The neat thing is that neutrinos produced by that supernova explosion were detected 3 hours before the light from the explosion became visible. How can this be? Neutrinos have mass (not much mass, but some, nonetheless), and so must travel slower than light (not much slower, though). Well, neutrinos are almost completely unreactive; they scarcely ever interact with normal matter. So, the neutrinos released by the supernova flew through space, completely unaffected by the occasional atom and molecule floating in interstellar space – until a handful of them happened to strike neutrino detectors here on Earth. The photons released by the explosion, though traveling faster, would occasionally get absorbed by a stray atom or molecule, and so their passage was delayed such that they arrived on Earth after the slower-moving neutrinos.



Just as absorption and then re-emission of photons by atoms can create the illusion that photons are moving slower than c, there are circumstances in which it can create the illusion that photons are moving faster than c.

I don’t pretend to really understand this, but I’ll try to explain it as a physicist explained it to me. (He assures me that at no point does anything move faster than c, and the “faster than light” illusion is just that – an illusion. Therefore, this trick could not be used to exchange information between points at faster-than-light speed any more than the “faster than light” lighthouse beam could be used to exchange information at FTL speeds.) Maybe one of our resident physics types can do a better job of explaining this phenomenon.

Weird things happen at the quantum level, including “instantaneous” changes in quantum state. Under the right circumstances, you can get a bunch of atoms into the same quantum state and shine some light into one end of the group of atoms. The absorption of photons by atoms at one end of the group will initiate a change in quantum state that “instantly” propagates through the atoms and ultimately results in the emission of photons by atoms at the other end of the group. The result is that this phenomenon can create the illusion that a photon traveled from one end of the clump of atoms to the other at faster-than-light speeds – the reality, of course, is that no photon ever traveled from one end of the clump of atoms to the other.

Such is my – admittedly limited – understanding of how light can appear to move through certain substances at FTL speeds.



Assume you have an identical twin. You are a passenger on the spacecraft in the question above, but your twin remains behind on Earth. If you travel at 99.9% the speed of light for 10 years by your reckoning, then return to Earth, are you and your twin still the same age? Why or why not?
As you approach the speed of light, you experience time dilation. You wouldn’t notice anything, of course, but time slows down as you approach the speed of light. (This phenomenon produces some interesting results. Tests with very precise clocks have demonstrated the phenomenon. If you take two clocks and synchronize them, then put one on a very fast jet, they will no longer be synchronized. When the jet lands and you compare the clocks again, you’ll find the one that has been on the jet will have lost a fraction of a second.) In theory, if you could accelerate something to the speed of light, it would experience no passage of time. (This is another reason why you can’t accelerate any material object to c – it would literally take an infinite amount of time to do so, since, as you approach c time moves slower and slower.)

If you could keep in constant radio contact with the Earth as you were zipping along at 0.999c, you’d notice a very weird phenomenon – everything would seem to be speeded up. People would grow old and die right before your eyes. The people back on Earth would see just the opposite – to them, you’d appear to be moving much more slowly in time. Well, sort of. In reality, the Doppler-shifting of the electromagnetic waves used for communication would mean that each twin saw the other appearing to age at the same rate. If they could somehow communicate via a medium that didn't experience Doppler-shifting, say by some sort of magical "psychic" means, the Earthbound twin would indeed see his twin as experiencing the passage of time much more slowly than he did, and the twin on the spacecraft would see the other as experiencing a greatly-accelerated passage of time.

Regardless, when you got back to Earth after a prolonged trip at near-light speed, you would indeed be younger than your twin – perhaps much younger.


You see a lightning strike in the distance. Why don’t you hear the thunder at the same moment?
As Dingfod said, “The speed of light far exceeds that of sound.” Therefore, you’ll see the flash before you hear the sound of the thunder.


Explain why large storms such as hurricanes rotate. Also, why do they rotate counterclockwise in the northern hemisphere, and clockwise in the southern hemisphere?
Because the Earth rotates, and because it is more or less rigid, any point on its surface must complete a rotation in the same amount of time – 24 hours. Since the Earth is (roughly) a sphere, its diameter at the equator is larger than its diameter elsewhere (declining to 0 at the poles). This means that a point on the equator must move faster than a point north or south of the equator as the Earth rotates, because it must travel a greater distance in those 24 hours.

The rotational velocity at the equator is about 1,000 miles per hour, dropping to 0 at the poles. The Earth rotates from West to East.


Consider a large, more or less homogenous mass of air somewhere in the Northern Hemisphere. The southern portions of that air mass, being closer to the equator, will be moving west-to-east faster than the northern portions, which will impart a counterclockwise spin to the air mass. In the Southern Hemisphere, the situation is precisely reversed – the northern portions of the air mass will move faster than the southern portions, so imparting a clockwise spin.

Your sink and bathtub are far too small for this effect to be noticeable, by the way. It’s a myth that bathtubs drain in opposite directions in the northern and southern hemispheres.


NASA and other space agencies take advantage of this phenomenon, known as the Coriolus Effect. If you launch a rocket in a west-to-east direction, the closer you are to the equator, the faster will be its initial velocity because of the Earth’s rotation – and therefore, the less fuel you’ll need to get it into orbit. That’s why NASA has launch sites in Florida and Texas, rather than Maine and Alaska.


The planet Mercury has a great many craters on its surface, as does our Moon. The planets Venus and Earth have very few visible craters. Mars has an intermediate number of visible craters. Explain the origins of these craters, and why the number of visible craters differs from one body to another.
Dingfod put it quite well. “Craters on planetary bodies are damage to the planet or moon surface from impacts from asteroids, meteors, and comets. Mars, Earth and Venus have atmospheres, the latter two much thicker atmospheres, which cause many of the approaching objects to burn up before striking the surface, the moons do not and show all impact craters that have ever occurred except where volcanic activity has covered them up. Additionally, Venus and Earth have plentify liquid precipitation erosion that mask or fill in impact craters, making them less visible than those on Mars.”

I would add that the Earth and Venus are larger than Mercury, Mars, or the Moon, and hence more geologically active, because their larger sizes mean that they have relatively less surface area and so don’t lose heat as rapidly – meaning that their insides are warmer. (The tidal effect caused by Earth’s large Moon also contributes to internal heating, thus making the Earth more geologically active than it would be otherwise.) Geological activity on the Earth and Venus further reduces the length of time that craters survive.


If you have a mass of 80 kilograms, you weigh about 176 pounds when standing on the surface of the Earth. Explain what would happen to your mass and weight if you were standing on the surface of the Moon.

Dingfod:“ My mass would remain the same 80 kg, but my weight would only be 1/6th that of on earth, about 29 pounds. This is primarily due to the smaller mass of the moon exerting less gravitational pull on my mass than the mass of Earth would.”

Your mass is how much of you there is. That won’t change just because you relocate. Your weight is the force generated by the pull of gravity on your mass. Since the Moon is much less massive than is the Earth and generates only 1/6 the surface gravity, you would weigh only 1/6 as much on the Moon’s surface as you do on the Earth’s surface.



Imagine an ecosystem that contains just one species, called a Snoggle. Female snoggles give birth to numerous baby snoggles, each of which has a large yolk sac that provides it with food as it grows. Of course, another way to get food is to catch and eat other snoggles. Is this a workable ecosystem? Why or why not?
Such an ecosystem cannot possibly work; a more straightforward violation of the Second Law of Thermodynamics would be hard to imagine.

In this ecosystem, the only source of energy for a snoggle is another snoggle – either directly (if it eats one of its fellows) or indirectly (if it’s subsisting on yolk supplied by its mother). As energy is transferred from one snoggle to another, some is inevitably lost (in the form of heat, etc.), and so the amount of usable energy in this ecosystem will inevitably decline until there is only one snoggle left – and it will starve.


Imagine a bomb is sitting on your kitchen table. At the moment, it isn’t moving relative to you, so its momentum is 0. Then it explodes. Since you happen to have superhuman speed and reflexes, not to mention very precise measuring equipment, you have the ability to measure the momentum of each fragment of the exploding bomb. When you add up their total momentum, what is it?
It might not seem obvious at first, but the momentum of the bomb before and after the explosion is the same – zero. Conservation of Momentum is one of the very best-established of physical principles.


To see why this is so, let’s simplify the system somewhat. Suppose the bomb consists of only 2 pieces, each of exactly the same mass. When the bomb explodes, each of them shoots off in opposite directions with the same speed, and therefore equal (but opposite) momentum. They do not have the same velocities, however!

Momentum = mass x velocity. Most people imagine that velocity is the same thing as speed, but it isn’t – and the difference is absolutely critical here. Velocity is speed plus direction of travel. So, if “Piece 1” of the bomb shoots off to the left at a given speed and “Piece 2” shoots off to the right at the same speed, their velocities are equal but opposite. Because one has a positive velocity and the other has a negative velocity, if you add up the momentum of the two pieces, it sums to 0. (Which direction of travel you designate as “positive” and which you designate as “negative” is arbitrary.)


So, if you could somehow measure the momentum of the various fragments of a stationary bomb a fraction of a second after it exploded (before air resistance slowed the fragments), they would total to 0.

That’s something that they almost always get wrong in Sci-Fi movies. If a spaceship is traveling at velocity “X” and is hit by a laser beam, causing it to explode, the explosion (which is just the pieces of the spaceship) will not come to a halt. It will continue moving at velocity “X”. [The reason a moving explosion in the Earth’s atmosphere soon comes to a relative halt is because of air resistance.]


If you go into any terrestrial ecosystem and add up the total mass of living matter in that ecosystem (the biomass), you’ll find that the plants greatly outweigh the animals. Why must this be true?
This, again, is due to the first and second laws of thermodynamics. Plants get their energy by capturing sunlight. Animals get their energy from plants – either directly (in the case of herbivores) or indirectly (in the case of carnivores).

When an animal eats a plant, most of the energy in the plant’s tissues is lost in the form of heat, excreted metabolic wastes, etc. So, the amount of energy available to support animals is considerably less than is actually contained in the tissues of the plants. So, there must be a much smaller mass of animals than of plants in the ecosystem.


Suppose you’re floating in outer space, far from any source of gravity. An evil villain has disabled the thruster jets on your spacesuit, and you’re floating 100 meters away from your spaceship. Your air supply is running out. Fortunately, you happen to have a rubber ball in your pocket. How can you use it to reach your spaceship?
Dingfod: “Throw the ball as hard as possible in the opposite direction of the spaceship, you will then move toward the space ship at a speed relative to the ratio of your mass to the mass of the rubber ball.”

Exactly so. For every action, there is an equal and opposite reaction. When you throw the ball, the ball exerts a force on you that is equal to (but opposite) the force you exert on it – because momentum is conserved. Before you threw, the ball the total momentum of the system comprising you and the ball was 0. After you throw the ball, the ball/person system still had a total momentum of 0. This means that if the ball travels in one direction with a given momentum, you must travel in the opposite direction with the same momentum. If you aim the ball correctly, you can get back to your spaceship this way. [Supposedly, there was an episode of Doctor Who in which The Doctor used this trick to get to the Tardis after being stranded in space, though I haven’t seen it.]


Giraffes are famous for their long necks. One explanation is that the ancestors of modern giraffes had short necks, which they stretched in order to reach leaves. Consequently, the offspring of these proto-giraffes had slightly longer necks than did their parents. Each generation, giraffes stretched their necks to more efficiently reach tasty leaves, and so each generation, giraffes had longer necks, eventually leading to modern, long-necked giraffes. Explain why this explanation fails.
This explanation could work only if giraffes passed on acquired characters to their offspring. Years of experimentation have shown that organisms do not pass on acquired characters (except under very limited circumstances), so this explanation cannot be true.


You’re standing on a tower on the surface of the Moon. You drop a steel ball-bearing and a steel cannonball at the same time. Which hits the ground first, and why? Now you repeat the experiment, but you substitute a feather for the ball-bearing. Which hits the ground first, the feather or the cannonball, and why?
The Moon has no atmosphere to speak of, so there is no air resistance to worry about. All objects fall with the same acceleration in a vacuum.

To a first approximation, anyway. If the object in question is really massive, it actually falls a bit faster than you’d expect, because you have to account for the fact that it has gravity, too, and so you have to factor in the acceleration caused by its gravity. For instance, if you could somehow hold a mountain in your hand and measure how fast it fell on the Moon when you let go of it, you’d find that it falls slightly faster than, say, a feather, because it actually pulls the Moon toward itself.

On the Apollo 15 moonwalk, Commander David Scott dropped a feather and a hammer at the same time, to illustrate this principle. Here’s a video of the demonstration: link (http://nssdc.gsfc.nasa.gov/planetary/image/featherdrop_sound.mov)


I’ve designed a machine. The way it works is that a sloped ramp supports a heavy steel ball. Atop a tower, a powerful magnet attracts the ball, pulling it up the ramp. When the ball reaches the top of the ramp, it falls through a hole in the ramp. As the ball falls, it turns a rotor, generating energy. When the ball falls to the bottom of the machine, it lands on the ramp again. Because the ramp supports the ball, the magnet can pull it back to the top of the ramp. Can this machine work, and can it generate usable energy? Explain why or why not.
This is a straightforward violation of the First and Second Laws of Thermodynamics.

Dingfod:“ Due to frictional losses and electrical generation inefficiencies the machine could never generate more energy than it uses.”

What’s more, any magnet strong-enough to pull the ball up the ramp would necessarily be strong-enough to prevent it from falling once it reached the top.


A solar eclipse occurs only when there is a new moon. A lunar eclipse occurs only when there is a full moon. Explain why this must be true.
A full moon occurs when the Moon is opposite the Sun in the sky, and so is fully illuminated from our perspective. A new moon is the opposite; it occurs when the Moon is between the Earth and the Sun, and so we see only its shaded side.

A solar eclipse occurs when the Moon is directly between the Earth and the Sun, and so its shadow falls on the Earth, blocking the Sun. So, it can occur only during a new moon.

A lunar eclipse occurs when the Earth is directly between the Moon and the Sun, and so the Earth’s shadow falls on the Moon. Since the Moon must be directly opposite the Sun from the Earth’s perspective for this to happen, it can only occur during a full moon.

The Moon does not orbit the Earth in the same plane that the Earth orbits the sun. So just because the Moon is opposite the Sun in the sky (and thus full) does not mean there will be a lunar eclipse. Similarly, just because the Sun and Moon are on the same side of the sky (and thus the Moon is new) does not mean there will be a solar eclipse. An eclipse can occur only when all three bodies happen to be directly lined up, so that the Moon’s shadow falls on the Earth (a solar eclipse) or the Earth’s shadow falls on the Moon (a lunar eclipse). Such a direct alignment is a rare event.


When you observe a star or distant galaxy through a telescope, you are not seeing it as it is now. You’re seeing it as it was in the past. Explain why this is necessarily so.
Light is fast, but it’s not infinitely fast. Therefore it takes time for light to travel the distance from a star to the Earth. It takes about 8.5 minutes for light to reach us from the nearest star, the Sun. So, theoretically, the Sun could have exploded 8 minutes ago, and we wouldn’t know about it for another 30 seconds or so. Light from the next-nearest star takes about 4.3 years to reach us.

The distance light travels in a year (about 5,865,696,000,000 miles) is a light year. It’s an often-used measure of astronomical distances.


Suppose you’re standing on the surface of the Moon and you have a rifle. You orient the rifle so that it’s parallel to the surface and exactly 1 meter above the surface. In your left hand, you’re holding a bullet exactly 1 meter above the surface. You pull the trigger of the rifle at exactly the same moment you drop the bullet you’re holding in your left hand. Which bullet hits the ground first, and why? [Yes, a standard rifle will fire in a vacuum; it’s not a trick question. Gunpowder contains its own oxidant, and does not require surrounding air in order to burn.]
If we don’t have to worry about air resistance mucking up our calculations, the rate at which an object falls is independent of its forward velocity. Therefore, assuming the bullet was fired parallel to the ground, it will hit the ground at the same time as the bullet that was dropped from the same height.


Suppose you live on the west coast of a continent. A range of high mountains extends down the coast, just a few miles inland. You notice that west-facing slopes of the mountains are lush and green, but the east-facing slopes are much drier. Why is this so?
Dingfod: “The mountains cause much of the moisture to fall out, leaving the leeward side with much less precipitation. That is because as the air rises over the mountains it loses pressure, which means it also loses temperature and its ability to hold water in its vapor state. [see also: Chinooks]”

This is known as the rain shadow effect. High mountains cast a “rain shadow” and are much drier on the leeward side. As moisture-laden air hits the near slopes and is forced upward, it cools. As it cools, it loses ability to hold water, and so you get lots of rain (and snow) on the near slopes. As the air crests the mountains and moves downward, it warms again. It has already lost much of its moisture and if anything, the warm, relatively arid air will tend to absorb moisture from the surroundings. So the leeward side of the mountains will be much drier.

This is why the coastal areas of Washington, Oregon, and much of California are so moist. After the air coming in from the Pacific crosses the Coast Ranges and Cascades, it has lost most of its moisture, so the inland regions are much drier. Air that continues eastward soon reaches the Rocky Mountains and loses yet more moisture, which is why the interior of the continent is so much drier than the coastal regions. (The effect is far less pronounced in the East, because the Appalachians aren’t as high or as extensive.)



Moss plants dry out easily, and can be killed by direct exposure to intense sunlight. Also, mosses can reproduce only when wet. How does this explain why you’re more likely to find moss growing on the north-facing side of a tree than the south-facing side? Hint: Is this true in the Southern Hemisphere?
For those of us living in the Northern Hemisphere – specifically, those of us living more than 23.5۫ north of the equator, the Sun is always in the southern portion of the sky. The north-facing side of a tree therefore receives less sunlight than does the south-facing side and so is better-able to support moss. (Don’t depend on this as a survival aid if you’re lost in a forest; in a forest, where sunlight is muted, moss grows on all sides of the trees.)

This phenomenon is why, in semi-arid regions, you’ll find trees growing on the north-facing slopes of hills and mountains much more than on the south-facing slopes. The north-facing slopes receive less direct sunlight, so they’re cooler and don’t dry out as much – so they can support trees better than the hotter, drier south-facing slopes.


The same phenomenon occurs in the Southern Hemisphere, of course, but it’s exactly reversed. There, the Sun is always in the northern part of the sky, so moss is more likely to grow on the south-facing side of a tree.



Cheers,

Michael

[JoeP]

davidm: :blush: I'd completely overlooked those factors. Shows what happens when you rush a a quiz.

TLR: :blush2: I see what I did wrong. My answers were not long enough!

[BDS]

Extra Credit: How many neutrinos can fit on the head of a pin?

[davidm]

My rambling response to Question One:

Long before we learned for sure that the world was more or less spherical, many people believed it was flat. Yet, some people hypothesized that it was round. So, a hypothesis seems to be in the nature of a guess, or a supposition made, perhaps, for the sake of argument. It seems we could end there without trying to find a way to test the hypothesis — we could say, for example, that assuming the world is round (and for that matter, assuming the world is flat) each might yield interesting and useful predictions — for navigation, maybe. If these predictions really were useful, even if different, would it actually matter whether the world were round or flat or something else? Thus, it seems that even if a hypothesis, or theory, were wrong, it still might be useful.

Alternatively, we might wish to test the hypothesis that the world is round. One way to do this would be to observe boats as they sail to the horizon. We might reason like this: If the world is flat, we should expect to see the boat getting smaller and smaller until it vanishes from view. But if the world is round, we should expect to see the boat slowly vanish from the bottom up, as it sinks over the curve of the horizon. Since we see the latter, we conclude the world is round. The hypothesis is verified, and from this we might proceed to construct theories (explanatory frameworks or conceptual schemes) to explain why the world is round; schemes that can be tested or falsified, and in addition, it is hoped, make additional predictions that generalize the theory (the way that theories of gravity generalize the behavior of falling apples and orbiting planets, phenomena that might otherwise seem unrelated).

Unfortunately it doesn’t seem to be that simple. The idea that if the world is round, we should expect to see the boat vanish from the bottom up as it sails over the horizon, itself carries some unstated assumptions: such as, for example, that the light coming from a distant boat behaves the same as the light coming from a nearby one. It would be a fairly simple matter to modify the underlying assumption in such a way as to show that a boat seeming to sink over the curve of the world actually demonstrates — because of postulated changes in the behavior of light over long distances — that the world is flat, not round.

Moreover, it seems that all the things normally associated with theories — verifiability, falsifiability, making novel predictions that can be checked, etc. — are conventional constructions of scientists. To see why, one need only look at string theory. Is string theory a scientific theory, or not? Lee Smolin doesn’t think so. There seems to be no way to check, verify, or falsify string theory — and this may be true forever. There is no empirical evidence for it! So how is string theory a scientific theory? And if it is, then what is the general “theory of theories” that would subsume string theory and, say, the theory of evolution under the same banner? Probably there is none!

Another interesting question is whether theories tell us about the way that the world is, or simply give us instrumentally useful answers to questions that we are cognitively capable of posing. And, since throughout history our best theories are constantly being overhauled, subsumed or discarded, it seems it’s best not to put too much faith in our current theories, even the ones that seem well-supported.

Problems, problems! :sadcheer:

[BDS]

Both hypotheses and theories are testable explanations for observed phenomena. The difference is that hypotheses are basically “educated guesses” that have had little or no testing. A theory has been thoroughly-tested and has (so far) passed all of the tests thrown at it – thus it’s very likely to be a correct explanation. Technically, you can never prove a theory correct, but the more thoroughly it has been tested, the more confident we are that it is an accurate explanation.

The way I learned it is that a theory is a set of statements -- generally a hypothesis and postulates supporting the hypothesis.

For example: All A are B is a hypothesis.

All A are C
All C are B

All A are B is a theory. (Consisting of a hypothesis and postulates)

This is quite similar to Lone Ranger's answer, but not identical. Perhaps it's a mathematical definition of theory and hypothesis, rather than a scientific one. According to this definition, it's not the extent to which the hypothesis has been tested that changes it into a 'theory', but the logical framework in which it is contained. IN other words, you could have an utterly faulty theory, as long as it is stated properly. (In fact, the history of science is replete with such theories.)

Of course, the tests that Lone Ranger mentions BECOME postulates consistent with the hypothesis, which, when placed in a logical framework as postulates supporting a hypothetical conclusion, turn it into a theory.

[Dingfod]

I’ve no idea what Dingfod is on about. Neither do I. I should've gone for the cheap laugh too.

[JoeP]

I'll have you know a lot of agonising effort went into my answers. Some I couldn't even think of responses to. :P