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Originally Posted by thedoc
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Originally Posted by Spacemonkey
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Originally Posted by thedoc
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Originally Posted by davidm
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Originally Posted by thedoc
But the Sun is moving through space very fast ...
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But the earth is moving with it. Therefore the sun is stationary with respect to the earth -- which is the whole key to understanding this. |
Yes, the Sun and everything in the solar system, including the Earth, are moving together through space, but the Earth is rotating on it's axis, and the position of the Sun appears to move in the Sky of the Earth. Photons emitted at one time from the Sun will arrive after the Earth has rotated on it's axis. |
The photons from the Sun move in straight lines outwards from the Sun within the reference frame in which the Sun is not moving. Hence the observer moves onto a new radial along which the received photons have always been moving, which puts the Sun exactly where it appears to be. You have the photons hopping off from the Sun and moving outwards from a point the Sun has only appeared to leave behind, like students jumping off a moving bus and heading towards a house directly from the point on the road where they left the bus. That is not what actually happens. |
It has been repeatedly stated on this forum, in this thread, that the sun is not in the sky where we see it. It has been stated that we see the Sunset 8.5 minutes after the Sun has actually disappeared below the horizon. Has that opinion changed in the last few days? |
If this has been stated, it's wrong. Hell, I may have stated it myself.
But, who raised this whole issue that started this current discussion, admits he got it wrong earlier until he thought about. It's an easy mistake to make. It just conflates apparent motion with actual motion. When you separate the two out, you get the right answer.
At sunset, we see the sun as it was 8.5 minutes in the past, but its apparent location and actual location are the same. You can actually pretty easily demonstrate this with a diagram.
But this is a special case and does not change the fact that apart from the sun, the apparent and real locations of other celestial bodies, with respect to earth,
are different because of the light speed delay. The sun is a different special case because its motion is apparent and not actual.
If the sun were
actually setting on the horizon; i.e., if it were
moving with respect to earth, then, yes, by the time the light got to us on the horizon, the actual sun would be below the horizon. The apparent and real locations would be different. But the motion of the sun is not actual with respect to earth, so this is not the case.