A Question For The Lone Ranger

[LadyShea]

That's them! They grow wild all over the place here. The color is really, really stunning. They are aptly named.

[Qingdai]

We have a different beauty berry, same color different berry distribution.

[MonCapitan2002]

I have a question for the Lone Ranger. There was an episode of Star Trek: Voyager, where Chakotay encounters and a pair of aliens from a culture called the Voth. The pair that he encountered were attempting to discover the origins of their species.

The aliens were researchers who proposed a distant origin theory that claimed they originated from a distant world that happened to be Earth during the time of the dinosaurs. Now the episode had made some questionable assumptions about science that would never hold water to any kind of critical scrutiny but it did have me thinking.

If a dinosaur species did develop sapience during that time and reached a technological level of development that had parity with our own, is it possible for there to be some evidence left behind that could lead to their existence being discovered? For instance, if they had heavy industry, would it be possible to detect such in the fossil record?

Please note that I am not claiming that it is possible that such a species existed. What I am interested in is if it is possible to find evidence for their existence if such a precursor civilization evolved on Earth. To ask the question in another way, if a meteor hit Earth and wiped us out, would we leave any evidence of our existence behind that could be detected 50 to 75 million years from now?

[ceptimus]

Originally Posted by MonCapitan2002

To ask the question in another way, if a meteor hit Earth and wiped us out, would we leave any evidence of our existence behind that could be detected 50 to 75 million years from now?

I think there would be some evidence left on Earth. We have plenty of evidence of dinosaurs and they only left bones, footprints, poo and such. We would leave the same things too, but also buildings, mines, roads, etc. I'm not saying they'd last for millions of years, but the fossilised evidence of some of these things should still be present.

The best preserved evidence would likely not be on Earth though. The landers on the moon would likely still be in excellent shape and those artificial satellites that have been placed in high Earth orbit would still be orbiting, even though they'd have stopped working for millions of years. We've also put some spacecraft into solar orbit, and the voyager probes are on their way to the stars...

[Ensign Steve]

That last one's coming back, though.

V'Ger - Memory Alpha, the Star Trek Wiki

[The Lone Ranger]

It's odd: an awful lot of the things that we take for granted as "permanent" would disappear in just a few thousand years. But other things (including plenty of stuff that we think of as worthless and so thoughtlessly throw away) almost-certainly would be easily detectable tens of millions of years into the future.

Let's start with how we've altered the makeup of the atmosphere and the soil – and hence, the biosphere. I'm not just talking about increasing amounts of CO2; I'm talking about injection of strontium into the atmosphere from nuclear tests and the like. As these isotopes gradually fall out of the atmosphere, they are incorporated into sediments – and into the tissues of living things.

I'm not talking about strontium radioisotopes – most of those have half-lives short-enough that they would have all but completely disappeared over millions of years. I'm talking about the stable isotopes of strontium. Since strontium is so similar to calcium chemically, it is readily absorbed by vertebrates and incorporated into their bones.

And if humans went extinct tomorrow, we’d almost-certainly leave behind an excellent fossil record, for two reasons. First, even though fossilization is generally an incredibly rare process, there are a lot of humans. By most accounts, Homo sapiens is easily the most abundant large land animal on the planet – and by a very large margin. Second, quite a lot of us insist on burying our dead. So even 50 million years or so into the future, there should be plenty of reasonably well-preserved human remains available for study.

And if these future paleontologists know enough about the chemistry of strontium, they’ll likely notice that, just before the species Homo sapiens went extinct, there was a sharp increase in the strontium content of their bones. (If they notice that, they’ll doubtless also notice that the same is true of all other contemporary vertebrates.) They’ll probably wonder why this happened. They might well conclude that there can be no “natural” explanation, and that this alone suggests a technological society.

Any paleontologist examining the remains of a human would immediately conclude that we were certainly brainy creatures; our brains are far larger than you would expect for an animal of our size. And while this by itself doesn’t mean that we had any kind of technological society, it might at least make the paleontologists wonder.

And with all of those fossilized humans, there would be plenty of evidence of some degree of technology. Lots of the fossils would have gold teeth, for example. If they were to dig up enough fossils, they might discover that some of them had glass eyes, and some had metallic/plastic devices (pacemakers) implanted into their chest cavities. Some would have bits of metal and plastic where the hearts used to be (mechanical heart valves). Some of them would have metal and/or plastic joints – especially hip and knee joints.

In short, with a large-enough sample size, examination of human remains would make it clear that we were a technological society.

What’s more, if these paleontologists did a sufficiently detailed study, they’d surely note that human remains are far from randomly scattered around the planet. They tend to be concentrated in certain places. What’s more, where you find concentrations of human remains, they tend to be associated with stones that look suspiciously like they have been machined.

Exposed to the elements, headstones will be eroded away relatively quickly. But if a graveyard were to be buried under sediment that eventually hardens into rock – as is likely in the event of an extinction-causing asteroid impact – the decay of the headstones would be greatly retarded. It would certainly be evident to any future paleontologist that these stones which happened to be associated with the human remains were not formed at the same time or in the same place as the surrounding sedimentary rock. Nor even by the same processes; marble is a metamorphic rock, and does not – indeed cannot – be formed in fossil-bearing sediments. In short, if a future paleontologist were lucky-enough to uncover the reasonably well-preserved remains of a single graveyard, that alone might easily provide enough convincing evidence to show that ours was a technological species.


For that matter, the sheer number of human remains scattered around the globe – from literally every inhabitable continent – would imply to any remotely competent paleontologist that Homo sapiens had an enormous population size. Even large animals that we think of as abundant tend to have populations measuring only a few million at most. A study of our remains would convince any paleontologist that our population was simply enormous – far too large to be capable of feeding itself without some sort of technology.


Speaking of those buried remains, it would be obvious that they had been buried, even if it weren’t for the headstones. Even if a graveyard isn’t buried in sediment and preserved along with intact headstones, we still insist on burying our dead. And so there’s an excellent chance that quite a few of these millions and millions of dead bodies will wind up being fairly well-preserved, and later discovered. And the future paleontologists would note that many of these remains had been placed into metal boxes (many coffins are made of metal) or had obviously-machined metal structures associated with them. (Even wooden coffins generally have machined fittings of brass or other metals – and brass is an alloy, not a “naturally-occurring” substance.)


Oddly enough, it’s not at all obvious that much of our architecture would survive. Unless they were buried under anoxic conditions, wooden structures wouldn’t survive for long. Stone and concrete structures that were exposed to the elements would be eroded away to nothing over a few thousand years’ time. Even most metals would corrode and become unrecognizable if exposed to the air.


But . . . we insist on burying huge volumes of refuse in dumps. Many of these are enormous, and the buried trash is simply not decaying, because conditions at the bottoms of these trash heaps are more or less anoxic. (Archeologists sometimes go excavating in trash dumps. It’s not unusual for them to find newspapers that are 40 or 50 years old and still perfectly legible.) So it’s entirely possible – indeed, very likely – that a lot of this stuff will eventually become incorporated into sedimentary rock.

If the event that takes us out manages to even partially bury a few cities (a la Pompeii), it seems entirely likely that future paleontologists would recognize the preserved metal, worked stone, asphalt, and glass as monuments of a technological society.

But even if no cities are buried and preserved, we’ve already buried and so inadvertently preserved plenty of stuff that will almost-certainly still be around in 50 million years or so. I’m not just talking about things like glass and perhaps stone; I’m talking about plastics.

Any future paleontologists digging in the sediments that correspond to 20th-century/21st-century Earth will inevitably find plenty of plastics. And I’m reasonably certain they’ll conclude that even if these plastics are too degraded for their original purpose to be divinable, the mere fact that they exist will be solid evidence for a technological civilization.


And if these future paleontologists have the means and desire to survey the Moon, they’ll discover our abandoned lunar landers, still pretty-much intact. Since the Moon has no atmosphere and is not geologically active, the only things that will have any real effect on the artifacts we’ve left on the Moon are solar and cosmic radiation – short of meteor impacts, that is. Additionally, some of our satellites will doubtless still be in orbit for tens of millions of years into the future.



So, the short answer is that unless they’re buried somehow, most of our cities will have eroded and degraded to almost nothing within a few thousand years. But we’ve buried so very many bodies – and so much worked metal, worked stone, glass, and plastics – that I’m guessing paleontologists 50 million years into the future will have no trouble figuring out that a technological society once existed. What’s more, if they’re paying attention, they’ll be able to note the drastic alteration in distribution and abundance of various plant and animal species over the past 1,000 years or so. And they’ll probably notice that it happened at roughly the same time that a superabundant, technologically-advanced primate species came to dominate the planet.

There’s probably very little they could infer about our society and technology other than that it existed, I would guess. (And that we really seemed to have a thing for plastics.) But it seems to me that any future paleontologists who do enough digging will find abundant evidence that our species existed, that it was extremely abundant and widespread, and that it had some degree of technology. At the very least, it should be clear that we were capable of metallurgy, and manufacture of plastics – and that we had a sophisticated agricultural system that was capable of supporting a very large population.


Oddly enough, I can’t decide whether I think of that as uplifting or depressing.


Cheers,

Michael

[Megatron]

TLR,

How the fuck is it that you know literally everything?

I'm serious here. I've asked you questions, and I've seen plenty others do the same, and you always know the answers to everything ever.

How do I even get 1/100th as smart as you?

I'm like, Real Dumb and I'd like to at least be A Little Smart. Maybe you can help me.

[erimir]

Maybe he spends 4 hours meticulously researching every answer he gives on here to give an illusion of scientific omniscience.

[The Lone Ranger]

I'm a fairly voracious reader, and I seem to have been blessed with a decent memory. So it has often been the case that if I don't know the answer right off the top of my head, I can recall reading something that touched on the subject, and so start from there.

As a rule, if I don't know the answer to a question, I can usually figure out how to find it.

In the case of MonCap's question, it happens that paleontology is one of my particular interests. So naturally, I've pondered the question of whether anything of our civilization would be detectable 65 million years into the future. It's an interesting thought experiment.



For good or ill, I'm a terrible insomniac. I literally can't remember the last time I had a decent night's sleep. Most nights, I lie awake thinking about stuff. I've never really been able to figure out how to shut my brain off.


Some of it is training, too. For instance, I'm quite familiar with most plant and animal families. So if you show me some plant or animal, if I don't know it, I can probably tell you what family it belongs to more or less at a glance. After that, it's just a process of elimination to narrow it down to the correct species.

Cheers,

Michael

[Dragar]

He even had an answer to the question of how he has an answer to every question!

[Nullifidian]

Originally Posted by Dragar

He even had an answer to the question of how he has an answer to every question!

Bertie Wooster: You bally well are informed, Jeeves! Do you know everything?
Jeeves: I really don't know, sir.
—Jeeves and Wooster, "Jeeves Takes Charge"

You can hear this line and Hugh Laurie and Stephen Fry singing "Minnie the Moocher" in this clip:

Minnie the Moocher - Jeeves & Wooster

[Qingdai]

I, on the other hand, know how to shut my brain off.

[SharonDee]

Originally Posted by The Lone Ranger

For good or ill, I'm a terrible insomniac. I literally can't remember the last time I had a decent night's sleep. Most nights, I lie awake thinking about stuff. I've never really been able to figure out how to shut my brain off.

Having just re-watched the film recently, this reminds me of John Travolta's character in Phenomenon. Seen any lights in the sky lately? Are you learning Portuguese in 20 minutes? Been hacking government stuff? Inventing a better fertilizer?

Watch out for the FBI!

[Ymir's blood]

The only thing that keeps me from waking up in the middle of the night, mind running full blast, is staying up too late before bed.

[thedoc]

Originally Posted by The Lone Ranger

For good or ill, I'm a terrible insomniac. I literally can't remember the last time I had a decent night's sleep. Most nights, I lie awake thinking about stuff. I've never really been able to figure out how to shut my brain off.
Cheers,

Michael

A friend of mine had that problem, and he told me that at night he would focus on a frame from a movie film and imagine the film has stuck and the heat from the bulb slowly melted and burned up the film till there was just a blank screen, and continuing to focus on that he would fall to sleep.

I occasionally have difficulty falling to sleep, so I get up and do something or read till I can no longer keep my eyes focused on the page and then put the book down and go to sleep. I can also wake up at any time I choose without an alarm clock, and I usually wake up and listen for a few minutes for my wife's alarm to go off.

[MonCapitan2002]

Originally Posted by Dragar

He even had an answer to the question of how he has an answer to every question!

It's clear he's omniscient. Now all we need to find out is weather he's omnipotent and all seeing as well.

[MonCapitan2002]

I have another question for The Lone Ranger.

George Carlin - The Environment and Nature -...

In the above clip from George Carlin's Jammin in New York HBO special he did in 1992, he makes the claim that 25 species go extinct a day. Is that true? The claim is made around the one minute 40 second mark.

[The Lone Ranger]

Sadly, he's off by quite a bit.

While it's difficult to know for sure what the true figures are, the UN Environment Programme has compiled various estimates, and figures that 150 - 200 species go extinct every day.


This is estimated to be about 1,000 times the "natural" or "background" rate of extinction.

There have been 5 "mass extinction events" that we know of in the history of life on Earth. Most specialists in biodiversity believe that we're currently in the sixth -- and that this one is almost entirely due to human activities.

[MonCapitan2002]

I have a new question for you, Lone Ranger. One thing I have read about in astrophysics is a concept of a goldilocks zone around a star where planets that form there can have liquid water.

I have watched programs that mention Venus is around the hot end of the liquid water zone. So here is my question. If Venus had a day / night cycle and atmospheric composition similar to Earth, would it be Earth like?

[The Lone Ranger]

The "Goldilocks Zone" for our Solar System is estimated to be between 0.725 - 3.0 astronomical units. (As I'm sure you know, an AU is the mean distance from the Earth to the Sun, so the Earth's mean distance from the Sun is 1.0 AU.)

At aphelion, Venus is 0.728 AU from the Sun, just within the estimated Goldilocks Zone. But for most of its orbit, it's too close to the Sun. Theoretically, even if it had an Earth-like atmosphere and rotational period, it would be too hot for most of each orbit for liquid water to exist.

[MonCapitan2002]

Well, that sucks. In any case, it's a non-issue considering the runaway greenhouse effect on Venus. I do wonder what will happen to the planet once it becomes geologically inactive. Since it doesn't have a magnetosphere from what I have read, it's thick atmosphere is credited to outgassing from within the planet. Once the core cools, that outgassing will be greatly reduced. At that point, Venus atmosphere would likely be stripped away.

Here is an additional question. If Jupiter had drifted inward and ended up with a final, stable orbit where Earth is, how would that affect any moons orbiting Jupiter? Also, if Earth was captured* into a stable orbit around Jupiter, would life have evolved? Last question, if Earth still has its moon when this happens, would it be wrenched away by Jupiter's gravity?

One other question. Would Jupiter look any different if it was at Earth's orbital location? I do have to wonder what the sky would look like if Earth were a Jovian moon, though. Also of interest would also be any mythologies that might develop in our culture.

*Let's ignore for the moment, the greater probability that Earth would either be slingshot out of the solar system, crash into Jupiter, or flung into the Sun.

[The Lone Ranger]

Jupiter itself would change substantially if it were brought to where the Earth is. Jupiter is mostly hydrogen and helium. It's able to hang onto all that hydrogen and helium because it's so far from the Sun, and thus so cold. Bring it to the Earth's orbit, and thus heat it, and a lot of its mass would escape to space.

Of course, what was left would probably still be much more massive than is the Earth. Still, from what I've read, most astronomers think that a hydrogen/helium gas giant like Jupiter simply couldn't exist as close to the Sun as the Earth is. This doesn't mean that a planet with the mass of Jupiter couldn't exist so close to the Sun (indeed, we know of such planets in orbit around other stars), but such a planet wouldn't consist almost entirely of hydrogen and helium, like Jupiter.

Uranus and Neptune have much greater concentrations of heavier compounds making up the bulk of their masses than do Jupiter or Saturn. A Uranus-type gas giant could probably exist much closer to the Sun than could a Jupiter-type gas giant.



But for now, let's ignore the problem that Jupiter would lose much of its mass if you brought it to the Earth's orbit. If you could bring Jupiter to the Earth's orbit without disturbing its satellites, what would happen to them? Europa, of course, is well-known for being covered by water ice. If you brought it to the vicinity of the Earth, that ice would surely melt.

But here's the problem: Europa is less massive than is the Earth's Moon, and its surface gravity is lower. So, like our own Moon, Europa would not be able to hold on to an atmosphere if it were as warm as it would be in Terran orbit. With zero atmospheric pressure, the oceans would boil away. So, alas, bringing Europa to the Earth's orbit wouldn't make it a suitable place for life.

In fact, exactly the opposite might be the case. Because of the tidal forces exerted on it by Jupiter's massive gravity, Europa gets flexed. A lot of astronomers think that the frictional heating is sufficient that under all that surface ice is an ocean of liquid water. If so, it's at least conceivable that Europa could support life now. But if you heated it up enough for the surface ice to melt, the oceans would then boil away.




So yes, Jupiter would necessarily look a lot different if brought to the Earth's orbit. How much mass it would lose I don't know. It's entirely possible that it would still retain enough mass that the Earth could become a satellite of Jupiter though, given that Jupiter is one really massive planet.

Of course, as you pointed out, it would be all but impossible to move Jupiter to Earth's orbit without Jupiter's gravity either ejecting the Earth from its orbit or causing the two planets to crash together.

But if you could somehow bring Jupiter to Earth's orbit without disrupting the Earth's orbit in the process, and if you could somehow retain most of Jupiter's mass, I don't see why the Earth/Moon system couldn't orbit Jupiter.

The barycenter for the Earth/Moon system is actually inside the Earth. So, if you put the Earth into a very wide orbit of Jupiter, it should be possible for the Earth to retain gravitational dominance over the Moon. The Earth/Moon system would have to be in a wide-enough orbit that Jupiter's tidal effect wouldn't pull the Moon out of the Earth's orbit, however. It wouldn't be like Avatar, where Jupiter dominated our sky -- if we were anything like that close to a planet with Jupiter's mass, I should think that the gravity of the Giant Planet would easily disrupt the Moon's orbit.


I'm sure it would be possible for the Earth to be in a fairly close orbit of a planet with Jupiter's mass. But it surely wouldn't be possible for the Earth to retain "control" of the Moon while in close orbit of a Jupiter-mass planet.

[MonCapitan2002]

Here's a question for you. How large can a rocky planet get? Is there a physical limit to the amount of mass a rocky planet can have?

[The Lone Ranger]

How big a terrestrial planet can get is a subject of some serious debate amongst astronomers. The consensus seems to be that yes, there is a limit on how big a terrestrial planet can be.

How big a terrestrial planet can be will be determined mostly by how close it is to its star -- and, therefore, how warm it is.


We already mentioned that a Jupiter-like gas giant couldn't exist as close to the Sun as the Earth is, because it'd lose much of its hydrogen and helium. You'd still have a pretty-danged-big planet, but it wouldn't be the Jupiter we know and love.


But let's look at it from the opposite perspective. What if we took 10 or so Earth-sized planets and collided them at slow-enough velocities that they coalesced instead of shattering. So you'd wind up with a "Super Earth" 10 times the mass of our Earth. We'll stipulate that this takes place where the Earth is now.

The resulting planet would not be 10 times larger than the Earth, because the greater gravitational attraction would mean that the matter making it up would be more compressed. The larger, denser planet would therefore not just have a larger gravitational field, it would have a higher surface gravity.

That means it would hold onto gas more effectively than the Earth does.

In other words, make a rocky planet that's big-enough, and you will get a gas giant, because it will have enough surface gravity to hang onto enough gas that the planet would be considered a gas giant.


In theory, it's simply a question of how much rock and metal (the Earth is mostly made of iron and nickel, not rock) you'd need to put together. Theoretically, at any given distance from a star, there's a minimum amount of matter you'd need to accumulate before you'll get a gas giant. Of course, the closer the planet is to the star, the warmer it will be, and so the more matter that would have to accumulate before you'd get a gas giant.


This is complicated by the fact that a star apparently ignites before the matter in its accretion disk has condensed into planets. So the heat of the young star will "clear" most of the lighter stuff like hydrogen and helium out of the inner part of the system, leaving mostly rocks and metals out of which planets can form.


So, in short, it doesn't appear to be that there's a real limit on how large a rocky planet could get, though a sufficiently large one would have an atmosphere so thick that it might well be called a gas giant.


That having been said, there's another important factor to consider. This is the fact that the cloud of gas and dust that ultimately condenses to form a solar system consists almost entirely of hydrogen and helium. The heavier elements that make up the bulk of a rocky planet are a tiny portion of the original nebula.

There does appear to be a practical limit on how large a star will be. After all, once the hydrogen and helium have condensed to the point that it's hot-enough and dense-enough in the protostar's core for fusion reactions to occur, the stellar wind will tend to blow away any nearby hydrogen and helium that has not yet been incorporated into the young star.

This means that there's a practical limit on how large a star is likely to be. And the bigger the star is, the brighter it will be. And the brighter the star is, the more intense will be its stellar wind, and the more effectively it will clear material away from its surroundings.

What this means is that there's necessarily going to be a limit to how much material is going to be available for formation of planets of any sort, but especially rocky planets. The metals and silicates that make up the bulk of a rocky planet are in short supply to begin with, and the brighter the star, the more effectively it will clear these materials out of its vicinity. (And we wouldn't expect smaller, dimmer stars to support very large rocky planets either. That's because small stars are small due to the fact that the nebulae from which they formed were relatively small -- and so would necessarily contain relatively little matter from which planets could form.)

With that in mind, I've read speculation that no star is likely to support a rocky planet that's more than about 15 - 20 Earth-masses in size, because there simply wouldn't be enough suitable material near the star for a larger rocky planet to form.

If that's the case, then really big planets will always be gas giants of some sort.




So: long story short. In theory, there's no limit to how large you could make a terrestrial planet. But in practice, a sufficiently-large planet will inevitably hang onto enough gas that it's likely to be considered a gas giant. And the limited amount of material in the accretion disk of a star that could be used for building rocky planets places a practical limit on how large any rocky planet around that star could possibly be.

Apparently, the limiting factor isn't how much mass you can put together, but in how much matter will be available for making a "Super-Earth."

[erimir]

How many licks does it take to get to the center of Tootsie pop?