Astronomy & Space Exploration

Does anyone else find it a little unnerving that about 50% of the stars and galaxies we see through any way of viewing probably don't even exist anymore, even though we can see them?

Speed of light and shit I know, but feck man, I can see something that probably isn't even there.
 
Here's one for you. If when we do those deep field scans and we're looking at the universe a few million years old, could we actually be looking back at ourselves?
 
Gambit said:
Here's one for you. If when we do those deep field scans and we're looking at the universe a few million years old, could we actually be looking back at ourselves?
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I love this thread.
 
Gambit said:
Here's one for you. If when we do those deep field scans and we're looking at the universe a few million years old, could we actually be looking back at ourselves?
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I'm afraid not. For that to happen we would have had to be moving away from the spot we're looking at at the speed of light, or something like that.
 
Tomalonge said:
Does anyone else find it a little unnerving that about 50% of the stars and galaxies we see through any way of viewing probably don't even exist anymore, even though we can see them?

Speed of light and shit I know, but feck man, I can see something that probably isn't even there.
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I don't think that's quite accurate. The general feeling is absolutely true, but the numbers aren't quite as "bad". For example, the stars we can see with our eyes are nearly all still around. When we start doing things like Hubble Deep Field or Ultra Deep Field, then the odds are higher. Stars generally go on for a long time, though.
 
Silva said:
Going back to this, if Earth was travelling faster than the speed of light, would it not have the effect of the light just getting stuck on earth, meaning that we'd see nothing from our trail anyway?
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That's where it gets weird, because according to Einstein light would still escape our planet at the speed of light, even if we were already going the speed of light. That doesn't mean the light would travel twice the speed of light, though, for some mathemathicsy reason I couldn't begin to explain.
 
That means it's going at the speed of light in relation to us (I think), but I was wondering what happens when we're going faster than light, would it be like tapping a football lightly then running at it and taking it in again, or would the light still manage to escape?
 
Silva said:
That means it's going at the speed of light in relation to us (I think), but I was wondering what happens when we're going faster than light, would it be like tapping a football lightly then running at it and taking it in again, or would the light still manage to escape?
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It would be teh same, the light would still travel away from us at the speed of light, regardless of our own speed. The speed of light in a vacuum is always the speed of light in a vacuum.
 
Well, you see. I wasn't just being contrary (part of it though, haha)

The only reason that light can travel so fast is that it has no mass. Therefore to travel faster than the speed of light you'd have to have less than just no mass. No light/heat/anything. It would just be dark antimatter (no idea if it would be antimatter, but I typed matter and with the whole "no mass" thing it didn't look right at all.)

Also. Silva, I think I get that bit. If the planet was travelling at the speed of light time would have a much, much slower effect on us. So we'd perceive it different to our current speed anyway. Light only travels one speed in space, so if the earth were travelling the speed of light then the earth would be keeping up with it's own light. As for what the experience would be like; nobody can answer that.

And in your scenario where we're travelling faster than light, we'd experience nothing, as we'd have no mass and therefore would be a little bit dead.
 
Tomalonge said:
Well, you see. I wasn't just being contrary (part of it though, haha)

The only reason that light can travel so fast is that it has no mass. Therefore to travel faster than the speed of light you'd have to have less than just no mass. No light/heat/anything. It would just be dark antimatter (no idea if it would be antimatter, but I typed matter and with the whole "no mass" thing it didn't look right at all.)

Also. Silva, I think I get that bit. If the planet was travelling at the speed of light time would have a much, much slower effect on us. So we'd perceive it different to our current speed anyway. Light only travels one speed in space, so if the earth were travelling the speed of light then the earth would be keeping up with it's own light. As for what the experience would be like; nobody can answer that.

And in your scenario where we're travelling faster than light, we'd experience nothing, as we'd have no mass and therefore would be a little bit dead.
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Technically, if we were travelling at the speed of light time wouldn't pass at all for us, as space and time are part of the same equation. Still, according to Einstein (I think!) in the example we would not be keeping up with our own light. There is that old example of two men who both fire guns at the same time and from the same distance, yet one is standing still and the other is on a train moving away from the target. The one who is on the train would hit the target slightly after the one standing still. Now, consider the same scenario except they are using flash lights. Assuming they are the same distance from the target, it doesn't matter whether one is moving away from it or not. The light beams would hit at the exact same moment.

At least I think that is relevant to the Earth example. It's a pretty theoretical example, what with time not passing at that point and all.
 
Well we would be keeping up with our light in our experience. Time stopping and shizz. To all others concerned it'd just be a insanely quick but immensely groovy light show I assume?

I realize what I said, but I was addressing Silva's question more. I should have quoted, apologies.

EDIT: He says, forgetting to quote the post he was replying to. :lol: ffs
 
The discussion on the Earth 'travelling at the speed of light' is based on a bit of a misconception.

For instance, if you were lying by the pool, dozing off the effects of the Christmas turkey, and spotted a ray of light flying past the Earth heading towards the outer solar system, and, having nothing better to do, jumped into your super fast spaceship, and took off in pursuit, quickly accelerating to 99.99% of light speed, and thought to yourself: 'I'm going to stay on this little sucker's tail till it reaches the nearest star', and then calculated the speed at which it was moving away, you'd find, to your chagrin, that it was receding from you at light speed. If you then gave up in disgust, turned the ship around, and headed back to Earth at 99.99% of the speed of light, and took one last grudging measurement of the light ray, it would still be moving away from you at light speed, even though you were now headed in the opposite direction.

The Earth, being a material object (object with mass), cannot travel with respect to any other material object at the speed of light, but it is moving at light speed with respect to the photons which are now striking your retina, and enabling you to read this text.
 
One thing none of you have taken into consideration. Back then when the deep field scan images occur our solar system wouldn't have existed. Neither would our Sun. Whose to say what particles we're looking at and how the universe expands. ( Yes I know light speed/mass blah blah blah but I also believe in Santa).
 
Gambit said:
One thing none of you have taken into consideration. Back then when the deep field scan images occur our solar system wouldn't have existed. Neither would our Sun. Whose to say what particles we're looking at and how the universe expands. ( Yes I know light speed/mass blah blah blah but I also believe in Santa).
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And :confused:
 
At a guess, since the original question was "could we be looking back at ourselves?", his point was that for all we know we are looking at things that eventually formed our galaxy, since those galaxies existed billions of years before ours and the shape of the universe and its mode of expansion aren't particularly well nailed down yet. I'm sure I've read theories that if you travelled in one direction in space for long enough, you'd end back where you started. Who knows?
 
We're now pretty sure we're not in that kind of universe, though. We couldn't really be looking back at ourselves either, since no information can travel faster than the speed of light. I know we talk a lot about looking "into the past", but we're also looking in a direction. What we're seeing is both far into the past and far away. Actually, it's even further away than it is "old", because of the expansion of space.
 
I believe this is where the Santa aspect of the argument makes its noisy entrance.
 
Relativity fecks with me... I remember I was once listening to an audiobook trying to explain certain fundamentals of science, and when it got to Einstein and the clock on the train station vs the clock on the train travelling close to the speed of light, and the torches and all that nonsense, I had to re-wind again and again because I felt sure I'd missed something. It just does not compute...

...but apparently it calculates right, and so I'm out of the discussion, being a complete tard in all things mathematical :(
 
Eriku said:
Relativity fecks with me... I remember I was once listening to an audiobook trying to explain certain fundamentals of science, and when it got to Einstein and the clock on the train station vs the clock on the train travelling close to the speed of light, and the torches and all that nonsense, I had to re-wind again and again because I felt sure I'd missed something. It just does not compute...

...but apparently it calculates right, and so I'm out of the discussion, being a complete tard in all things mathematical :(
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Relativity is so yesterday news.

Quantum mechanics and string theory is the real deal. That makes relativity somehow looks simple.
 
Revan said:
Relativity is so yesterday news.

Quantum mechanics and string theory is the real deal. That makes relativity somehow looks simple.
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String theory hasn't gotten itself away from being entirely speculative in all its years of imminent paradigm shift. And Quantum mechanics is tricky and alien, but relativity pertains to things that one would think our intuitions should be somewhat suited for by comparison.
 
Eriku said:
String theory hasn't gotten itself away from being entirely speculative in all its years of imminent paradigm shift. And Quantum mechanics is tricky and alien, but relativity pertains to things that one would think our intuitions should be somewhat suited for by comparison.
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Agree about string theory. Despite that is the best explanation we can come at the moment, it is based very much on speculation so it could be entirely wrong.

Quantum mechanics is definitely more counter-intuitive than the special theory of relativity. The double slit experiment is the most strange experiment that has ever happened. And that is only the beginning of quantum mechanics.
 
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