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Originally Posted by Ceptimus
For example, in a total solar eclipse, when the last sliver of sun can still be seen just before totality, the sun has already been totally obscured. Light takes about 1.3 seconds to travel from the moon, so we see the moon in the position it was 1.3 seconds ago.
There is no doubt at all that we do this - when we send rockets to land or pass close by other planets or their moons, the rockets would all miss their targets if we didn't aim the rockets allowing for the fact that the targets are all in front of their apparent positions.
The scientists are smart enough to say, 'We see Jupiter's moon Io there, but we know that light from IO has taken 43 minutes to travel to us so Io will really have moved on and be there at this moment.'
Because we see Io as it was, and in the position it was, 43 minutes ago, we can sometimes be still observing Io when we know that it has actually moved out of our line of sight, behind Jupiter.
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Originally Posted by peacegirl
That's the theory.
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No, that has been observed numerous times, and as was pointed out, we have launched unmanned spacecraft that made it to the outer reaches of our solar system without crashing into moons and planets because we knew this.