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Author Topic: Is the universe expanding faster than the speed of light?  (Read 3836 times)

Offline chris

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The Universe is presumably expanding faster than the speed of light, but how, if light is the fastest thing that there is?

Chris


 

Offline Soul Surfer

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Is the universe expanding faster than the speed of light?
« Reply #1 on: 04/07/2008 10:24:35 »
Because it is the space itself that is expanding and not things that are moving quickly.  On our scale this expansion is incredibly tiny and is completely unmeasureable.
 

Offline Madidus_Scientia

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Is the universe expanding faster than the speed of light?
« Reply #2 on: 04/07/2008 10:51:04 »
Wouldn't that be the same as if you flash 2 lasers in opposite directions, the distance between the photons would be expanding at twice the speed of light (relative to the observer in the middle of the lasers)
« Last Edit: 04/07/2008 10:59:22 by Madidus_Scientia »
 

Offline lightarrow

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Is the universe expanding faster than the speed of light?
« Reply #3 on: 04/07/2008 13:31:52 »
Wouldn't that be the same as if you flash 2 lasers in opposite directions, the distance between the photons would be expanding at twice the speed of light (relative to the observer in the middle of the lasers)
But that quantity is not a physical velocity, just a mathematical one (it's not the same).
 

Offline Alan McDougall

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Is the universe expanding faster than the speed of light?
« Reply #4 on: 04/07/2008 16:24:23 »
Space has no mass so the expansion of it must be infinite.
 

Offline DoctorBeaver

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Is the universe expanding faster than the speed of light?
« Reply #5 on: 04/07/2008 16:51:35 »
Chris - you really should do a search of the forum before you ask a question  :P

This was asked very recently
 

Offline Alan McDougall

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Is the universe expanding faster than the speed of light?
« Reply #6 on: 04/07/2008 17:15:43 »
But if the red shift ratio is correct the outer part of the universe is expanding at speeds that exceed C
 

Offline chris

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Is the universe expanding faster than the speed of light?
« Reply #7 on: 05/07/2008 13:33:55 »
Chris - you really should do a search of the forum before you ask a question  :P

This was asked very recently

Sure Eth, I appreciate your attention to detail! However, the question is asked in a slightly different way and therefore useful to help people find the answer; your link to the other thread is extremely valuable in helping people to do this...

Cheers

Chris
 

Offline Soul Surfer

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Is the universe expanding faster than the speed of light?
« Reply #8 on: 05/07/2008 18:34:10 »
Putting the expansion of the universe into context

It is important always to remember that it is the space itself that is expanding and not things that are moving quickly.  On our scale this expansion is incredibly tiny.

Let me do some simple calculations 

The Hubble constant or expansion coefficient of our universe is  about 70km/sec per megaparsec in astronomers units.

Let us now put it into more familiar units and relate it to distances in our solar system. A parsec is about 3.26 light years or 206,265 times the distace of the earth from the sun.

So over a distance of  206,265,000,000 the distace of the earth from the sun the expansion velocity is 70,000,000 millimeters per second  (remember there are a million millimetres in a kilometer)

So the expansion of space between the earth and the sun is   70,000,000/206,265,000,000  millimetres per second.

This is about .00034 millimetres per second in about 150 million Km 

let us give this velocity a bit longer to show itself, say one year

there are 365x24x60x60  = 31,536,000 seconds in a year

so in a year the space equal to the distace from the earth to the sun the space expands by  31,536,000x  0.00034 millimetres  10,722 mm or about 10 metres.

But surely I hear you say  if the earth got ten metres further away from the sun every year over many millions of years this would have a significant effect?  the answer is no! because the expansion of space does not significantly push the earth away from the sun because the energy of the attraction of gravity between the earth and the sun is so much greater that it completely overwhelms this effect and no change takes place.

It is only on the vast scales of distances between clusters of remote galaxies that the effect of the expansion of space can be measured.  To measure it in the laboratory would be totally impossible.
« Last Edit: 05/07/2008 18:37:36 by Soul Surfer »
 

Offline Alan McDougall

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Is the universe expanding faster than the speed of light?
« Reply #9 on: 05/07/2008 21:03:14 »
Chris,

Quote
The Universe is presumably expanding faster than the speed of light, but how, if light is the fastest thing that there is?

Chris

How about this answer from a puny mortal like me.

The universe "IS' expanding now at greater than light speed because it is embedded is "massless space" that has no speed limit.

Chris I know you posed this question because you know many people are puzzled by this. I know you knew the answer before you created the thread. You want to keep the forum fresh.

Regards

Alan
 

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Is the universe expanding faster than the speed of light?
« Reply #9 on: 05/07/2008 21:03:14 »

 

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