What can travel faster than the speed of light?


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Message 1084668 - Posted: 7 Mar 2011, 15:38:13 UTC
Last modified: 7 Mar 2011, 15:39:07 UTC

I have read that the expansion of the universe is expanding faster than the speed of light. Also, as time goes on the expansion of the universe is speeding up.

Question is what is it expanding into?

My thoughts are that space is falling into some kind of abyss and it is speeding up as it falls. Much in the way gravity pulls down an object and its speed increases as it falls.

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Message 1084685 - Posted: 7 Mar 2011, 17:21:38 UTC


In my mind, there's a problem with the expanding Universe vs SOL.

The theory states the Unvierse is expanding in all directions, as observed from Earth. That means that the farther away something is from where we are, the faster it is receding from us. I think everyone agrees on that.

Now, let's change our point of reference. Let's call Earth's current location point A and suppose for a minute that Earth has been re-located to one of those far distant galaxies (call it point B) at the very edge of our vision, and we are looking back towards the Milky Way Galaxy (point A).

Now what's happened? The MWG (point A) appears to be receding from us (at point B) faster than the nearer objects. Just the same as it is now, without any relocating involved. But, are we really moving at near lightspeed? Are the distant galaxies? Is all the matter we see or detect moving near SOL?

The problem is, THOERETICALLY, we can see 13 billion ly in any direction, no matter if we are at point A or B, and the local objects we see are not moving faster than the SOL.

Otherwise, the Earth appears to be centrally located in the Universe! OMG, maybe Copernicus was only partially correct!

Martin


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Message 1084687 - Posted: 7 Mar 2011, 17:55:20 UTC - in response to Message 1084685.
Last modified: 7 Mar 2011, 17:56:35 UTC

... The problem is, THOERETICALLY, we can see 13 billion ly in any direction, no matter if we are at point A or B...

Otherwise, the Earth appears to be centrally located in the Universe! ...


It's all relative.

We are in the centre of our observable universe. That doesn't mean to say that there is nothing beyond what we can observe. It's just that we cannot 'see' it.

Also, there's an awful lot of history that has already happened before we get to see some of the starlight. We glibly speak of 'light-years'. Note that describes 'how long ago' aswel as 'how far away'.

But also note that with relativity we cannot know any absolute measure of position or time.

Keep searchin',
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Message 1084854 - Posted: 8 Mar 2011, 3:27:53 UTC - in response to Message 1084685.
Last modified: 8 Mar 2011, 3:28:28 UTC

There is no preferred reference point in the universe. A is moving away from B is the same as B moving away from A on the reverse vector. Who is the one moving--if A were a rocket you might say the A is doing the moving and B is standing still. It's all relative however when the space itself expands. We are moving away from a point 15 billion light years away at the speed of light or faster. The universe is 56 billion light years across--(figure that one out for yourself) even if it has been in existence only 15 billion years.

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Message 1084861 - Posted: 8 Mar 2011, 3:46:48 UTC

I really bruise my brain with this stuff. I have a feeling I am not alone.

If the rock I am standing on is moving one direction at 60% of the speed of light in one direction, and another rock is moving the opposite direction at 60%of the speed of light the other direction.. Will I not see where the rock WAS?

assuming I have great eyes and a really good telescope....
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Message 1084991 - Posted: 8 Mar 2011, 13:51:33 UTC - in response to Message 1084861.

you should be able to see where it was but not where it is.
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Message 1085211 - Posted: 9 Mar 2011, 4:08:20 UTC - in response to Message 1084854.

The universe is 56 billion light years across--(figure that one out for yourself) even if it has been in existence only 15 billion years.


So, what's beyond the 'edge'? Another universe?

C'mon, we're all just guessing. Spock would not approve.

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Message 1085222 - Posted: 9 Mar 2011, 5:37:31 UTC - in response to Message 1085211.

The universe is 56 billion light years across--(figure that one out for yourself) even if it has been in existence only 15 billion years.

So, what's beyond the 'edge'? Another universe?

As I read it, here “the universe” refers to the observable universe, centred on us. The “edge” is just the surface of our light-cone, outside of which nothing is in causal contact with us. So in answer to your question I’ll say: more of the same. ;)

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Message 1085226 - Posted: 9 Mar 2011, 5:58:01 UTC

I see your brains are about as messed up as mine is thinking about this subject. ;)

Just imagine being on a planet in a galaxy that is located just to the edge of the expanding universe. They have a front seat view of everything. They can see where we are going.








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Message 1085303 - Posted: 9 Mar 2011, 14:18:57 UTC - in response to Message 1085226.

I see your brains are about as messed up as mine is thinking about this subject. ;)

Just imagine being on a planet in a galaxy that is located just to the edge of the expanding universe. They have a front seat view of everything. They can see where we are going.


Wouldn't they just see darkness? Bet for someone that flew out into the darkness the return would look awesome...
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Message 1085314 - Posted: 9 Mar 2011, 14:59:13 UTC - in response to Message 1085303.
Last modified: 9 Mar 2011, 14:59:43 UTC

I see your brains are about as messed up as mine is thinking about this subject. ;)

Just imagine being on a planet in a galaxy that is located just to the edge of the expanding universe. They have a front seat view of everything. They can see where we are going.


Wouldn't they just see darkness? Bet for someone that flew out into the darkness the return would look awesome...


Might be darkness or might be something else.

Hopefully after we communicate with other civilizations we will connect a network of civilizations. Eventually leading us to the very edge to a planet that might enlightened us to the answer.

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Message 1085328 - Posted: 9 Mar 2011, 15:44:16 UTC - in response to Message 1085222.

The universe is 56 billion light years across--(figure that one out for yourself) even if it has been in existence only 15 billion years.

So, what's beyond the 'edge'? Another universe?

As I read it, here “the universe” refers to the observable universe, centred on us. The “edge” is just the surface of our light-cone, outside of which nothing is in causal contact with us. So in answer to your question I’ll say: more of the same. ;)



If William meant "observable", then maybe I can explain.

The farthest back we can 'see' now is ~14bn lys. That means the BIG U has had 14bn years to expand beyond where it was then, when that light started out on its long journey to us. If the diameter of the U was (14bn lys+14bn lys) 28bn lys then, it should now be (28bn lys+28bn lys) 56 bn lys in diameter.

And, 14bn years from now, the light from the current 'edge' will be observable here on Earth (I know, I know, but, just imagine it will be!).

William, is that about it??

Quoting from http://www.nasa.gov/audience/foreducators/5-8/features/F_How_Big_is_Our_Universe.html

So how big is the universe? No one knows if the universe is infinitely large, or even if ours is the only universe that exists. And other parts of the universe, very far away, might be quite different from the universe closer to home. Future NASA missions will continue to search for clues to the ultimate size and scale of our cosmic home.

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Message 1085384 - Posted: 9 Mar 2011, 20:18:30 UTC - in response to Message 1085328.

OK OK. We've made a huge human error again with the Universes age thing. Remember reading how the Church declared earth as the center of the universe. We aren't astronomers doing the same thing still? If we can see 14 Billion light years in every direction that would probably double the age of the universe right there. Again, we have to assume we are not the center of the universe so there are probably galaxies further away than we already can see.
If we can see things that are billions of light years in all directions doesn't make us the center it just means we can't see any further away.
I have trouble assuming this age. When an astronomer says they've seen a supernova from 14 billion light years away in a primordial galaxy. But if that galaxy started for the same point in the big bang then it would either have to be much older than we think or even more distant than we assume.

This leads me to think that the Big bang theory may be more like a lot of big bangs theory instead.
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Message 1085431 - Posted: 9 Mar 2011, 22:07:18 UTC

I don't think we can see 14 billion light years in every direction. It is only stated that there are objects that we can see that are ~14 bn lys away.

However, it would seem that we are indeed the center of the universe if that was true. :)



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Message 1085445 - Posted: 9 Mar 2011, 22:25:42 UTC - in response to Message 1085431.



True, not necessarily 14bn lys in all directions. I used that number only for reference as it was the oldest light detected at the time of the article (2006).

We are centered in what we can see around us. Like the glow of a camp fire in the woods.

Where we are in the entire universe is unknown, AFAIK.

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Message 1085456 - Posted: 9 Mar 2011, 22:44:25 UTC - in response to Message 1085226.
Last modified: 9 Mar 2011, 22:53:21 UTC

I see your brains are about as messed up as mine is thinking about this subject. ;)

Just imagine being on a planet in a galaxy that is located just to the edge of the expanding universe. They have a front seat view of everything. They can see where we are going.


Yes.

However, they could not communicate to us what they see any faster than for us to see for ourselves. Whatever communication they might use, that communication cannot fly any faster than the light they might want to tell us about!


Keep searchin',
Martin
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Message 1085460 - Posted: 9 Mar 2011, 22:52:38 UTC - in response to Message 1085211.
Last modified: 9 Mar 2011, 22:54:12 UTC

So, what's beyond the 'edge'? Another universe?


Wrong question. Note that there is no 'edge'.

Trying to give a down to earth example: It's like comparing the view of the flat-earthers who believed that you could sail or walk off the edge of our planet to be lost into some unknown oblivion vs Sir Francis Drake who sailed around it in a single direction to return to his start place.


Keep searchin',
Martin

ps: For the sake of completeness, also note Notable circumnavigations
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Message 1085463 - Posted: 9 Mar 2011, 23:02:36 UTC - in response to Message 1085431.

Ned Wright’s cosmology tutorial has a relevant article: Where was the center of the Big Bang? See also the FAQ If the Universe is only 14 billion years old, how can we see objects that are now 47 billion light years away?

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Message 1085475 - Posted: 9 Mar 2011, 23:29:11 UTC - in response to Message 1085460.
Last modified: 9 Mar 2011, 23:32:44 UTC

So, what's beyond the 'edge'? Another universe?


Wrong question. Note that there is no 'edge'.



I don't believe there is an edge, either. I was asking William after he asserted that the Universe is 56 bn lys across. See his post.

The question was only relevent in response to his post.

Martin
[edited...]

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Message 1085510 - Posted: 10 Mar 2011, 1:20:13 UTC - in response to Message 1085475.

A sphere has an "Edge" in the third dimension.
So we have the usual questions.

What is the topology of the universe. Is it a sphere, a torus, a mobius strip, a Klein Bottle. What is the expanding universe expanding into ?

Is space curved back upon itself due to the matter it contains?

All interesting and hard to fathom.

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