Concerning the speed of light and space travel

[Backstop]

Concerning the speed of light and space travel:

When looking at the idiot box, the image is moving from the screen to my eye at the speed of light.

There is an amount of time - albeit infinitesimal - that it takes the image to get from the tube to me.

When we’re looking at, for instance that new earth-like planet, what we’re actually seeing is an image - or snapshot of time - from 20 years ago.

Whatever we see actually happened 20 years ago. Assuming the planet is 20 light years away.

So it is not incomprehensible in my mind that one day we’ll look at that planet and see the launch of a spacecraft. Directly next to the launch pad, we’ll also see a large neon sign that says, “A delegation from our planet will arrive at your door in 3, 2, 1...”

This may seem jocular in nature, and it is. But I’m seriously wondering if I have the theory correct.

[Luke]

Your theory seems correct to me, not so sure about the neon sign though.

I should think that using the old Hubble Telescope we are actually looking farther back in time, however I would also have thought that by now we would have seen sometype of spacecraft headed somewhere.

[American Patriot]

Mostly correct.

With some caveats.

First of all, you're looking at a television - the old version (not HDTV) and you see actually TWO images per second. Well, two halves of an image ever .5 seconds.

Television scans an electron beam across a phosphor screen at 18525 hertz (cycles per second) in a set of scan lines of 525.5 lines.

Ok... all of that said (there's a lot more to it, but that's close enough for government work) the light still travels practically instantly from the screen to your eyes. It takes another... oh 1/3d of a second to process and you're seeing things.

Now... as for putting up a neon sign, I doubt that visual astronomy will EVER be that good.

On the other hand.

A radio signal travels at the speed of light.

A space ship traveling at the speed of light and a radio wave leaving at the same time should arrive at roughly the same time.

On the other hand..... wow.... just thinking about this gives me a headache, relativity does something to all of this, and anything reaching there in say, 50 years will be "normal", but life on Earth will be... oh 50,000 years along.