# Thread: Galaxies Travelling Faster Than the Speed of Light?

1. There seems to be some controversy on this video after reading the comments making claims that some information is not true https://www.youtube.com/watch?v=XBr4GkRnY04 and I was hoping you guys could critique any invalid points in this video.

Thanks! It just seems impossible that the galaxies would move away from us FASTER than the speed of light

2.

3. I can't watch videos at the moment (and I find them to be waste of time usually) however...

There is obviously no conflict here:

1. The limit on things moving faster than light is a local restriction from the theory of relativity.
2. The model of expanding space (which means that objects sufficiently far apart will be separating at greater than light speed) comes from ... the theory of relativity.

4. Originally Posted by Strange
I can't watch videos at the moment (and I find them to be waste of time usually) however...

There is obviously no conflict here:

1. The limit on things moving faster than light is a local restriction from the theory of relativity.
2. The model of expanding space (which means that objects sufficiently far apart will be separating at greater than light speed) comes from ... the theory of relativity.

I see thank you, ok so about Light if object 1 is earth and object 2 is some light emitting source travelling away from us greater than the speed of light what is the outcome of the following questions.

If object 2 just hit 1 light year away and emitted some light, would it take just 1 year for that light to reach object 1? Or would the speed of object 2 make the time greater? I don't seem to have a full understanding on how light travels after watching this video.

I would assume that it would only take 1 year, because light will always travel at the speed of light.

Or would it take longer, not because light is travelling slower due to object 2 travelling faster, but the physical distance between the two is increasing due to space itself expanding.

Is the expansion of space itself what causes galaxies to move away from us faster than the speed of light? I thought it was due to the explosion of the big bang sending energy out in all directions.

Sorry for all the nooby questions, I think I am now starting to understand the big picture

5. Originally Posted by ScienceNoob
I see thank you, ok so about Light if object 1 is earth and object 2 is some light emitting source travelling away from us greater than the speed of light what is the outcome of the following questions.
These objects would have to be billions of light years apart. If they are sufficiently far apart, then the light from one will never be able to reach the other. That is the cosmological horizon: Cosmological horizon - Wikipedia, the free encyclopedia

After that it gets quite complicated...

Is the expansion of space itself what causes galaxies to move away from us faster than the speed of light? I thought it was due to the explosion of the big bang sending energy out in all directions.
The big bang was not an explosion. It is a description of the way space expands.

Speed of separation is proportional to distance. This is just a simple consequence of this expansion being the same everywhere, the amount of expansion is proportional to distance. For example, two objects are X distance apart and their distance increases by 0.1X; then two objects that are 2X apart will increase by 0.2X in the same time. In other words their rate of separation is twice as great. If two objects are sufficiently far apart, their rate of separation will be greater than the speed of light. But they are not really moving through space relative to one another; there is just more space between them due to expansion.

6. Originally Posted by ScienceNoob

If object 2 just hit 1 light year away and emitted some light, would it take just 1 year for that light to reach object 1? Or would the speed of object 2 make the time greater? I don't seem to have a full understanding on how light travels after watching this video.

I would assume that it would only take 1 year, because light will always travel at the speed of light.

Or would it take longer, not because light is travelling slower due to object 2 travelling faster, but the physical distance between the two is increasing due to space itself expanding.

Is the expansion of space itself what causes galaxies to move away from us faster than the speed of light? I thought it was due to the explosion of the big bang sending energy out in all directions.

Hi ScienceNoob. As Strange has mentioned there are two things to consider here.

Locally (that means in the immediate vicinity of an observer) all observers agree that the speed of light (in a vacuum) is constant (a value referred to as c). That means that at small scales such as in the vicinity of our immediate galaxy, irrespective of the relative velocities of different observers carrying around light sources, they will all agree on the same speed of light for each light source. To get a better grip on this you will need to spend some time understanding special relativity. What this does is put a speed restriction on all things travelling THROUGH space. You will then find out that in 4 dimensional spacetime, ALL things travel through spacetime at this finite speed limit of c. What does vary however for different moving things with mass is what component of their motion is spent travelling through space or time. For all massless particles such as the photon, all their motion is directed through space (hence the notion of the timeless photon) and hence the full value of c is reached travelling through space......anyway this applies to all things travelling through spacetime.

Then we need to consider the context through which these things are travelling, namely spacetime itself which 'globally' is expanding (meaning at all points in spacetime) and it appears that this expansion is currently accelerating. The reason for this expansion is still unclear but it is mathematically understood in general relativity as being attributed to the Cosmological Constant. Many believe the cause is associated with dark energy (which may or may not be associated with Zero Point Energy) which is a quantum effect embedded at all points in spacetime. This expansion of spacetime is intrinsic to spacetime itself and is not observed locally as local objects are bound gravitationally together. When dealing with measuring the seperation of objects over large scales however, observations conclude that in addition to local movement through space, you need to also take account of the fact that their is an intrinsic expansion going on of the entire spacetime area within which things move.

So in a nutshell when comparing distances between objects seperated over large scales you need to consider the movement of these objects THROUGH spacetime and also include the effect of the expansion OF spacetime itself.

EDIT: Now this does not contradict Einstein as Special Relativity is a local theory. So the universal speed limit of c is valid for things moving through spacetime but for things spatially sperated over large scale distances the addition of spatial seperation from spacetime expansion over time means that indeed all distant galaxies (which are not graviitationally bound) appear from observations to be travelling faster than the speed of light away from us and this rate of acceleration from current observations appears to be accelerating, hence the terminology currently used by many of an accelerating universe.

7. Originally Posted by Strange
Speed of separation is proportional to distance. This is just a simple consequence of this expansion being the same everywhere, the amount of expansion is proportional to distance. For example, two objects are X distance apart and their distance increases by 0.1X; then two objects that are 2X apart will increase by 0.2X in the same time. In other words their rate of separation is twice as great. If two objects are sufficiently far apart, their rate of separation will be greater than the speed of light. But they are not really moving through space relative to one another; there is just more space between them due to expansion.
That was worth a 'like'.....but it's broke I tells ya :-))

8. Ahh I see now that completely makes sense, check this thread expanding on some of these ideas please.

Thank you for the enlightenment that was a great explanation that makes me completely understand the expansion to our current knowledge. Current explanations also make sense if the expansion is true.

9. One of the reasons why NASA - 'specially Harold G "Sonny" White think it is possible to supercede the speed of light is because space itself we think can warp. Space is not necessarily bound by general relativity. Space is really in my opinion a special mystery.

10. Originally Posted by Mayflow
One of the reasons why NASA - 'specially Harold G "Sonny" White think it is possible to supercede the speed of light is because space itself we think can warp. Space is not necessarily bound by general relativity. Space is really in my opinion a special mystery.
Rubbish.

11. Up to her usual standards..

12. Well think as you wish - but if you actually have something to say, do so, not just calling others rubbish and then thinking you are smart and cool for doing so, because you are not.

13. still just whining when your crap gets called out...

14. Originally Posted by Mayflow
One of the reasons why NASA - 'specially Harold G "Sonny" White think it is possible to supercede the speed of light is because space itself we think can warp. Space is not necessarily bound by general relativity. Space is really in my opinion a special mystery.
Please stop posting woo about Harold G. Sonny White, and do not imply that NASA thinks a warp drive is possible. None of his work on this has been peer reviewed. Stop cluttering up the physics forum.
Harold Sonny White warp drive: Faster than light secret physics debunked.

15. One day humans will have nuclear fusion at personal use and we will also learn to use space as a medium of faster than light transportation.

White works for NASA and has real time high achievment awards from NASA, and that means something to me. White was awarded the NASA Exceptional Achievement Medal by the Administrator for his role in getting the Thermal Protection Systemrobotic inspection tools during the Space Shuttle's return to flight.[9] White has also received the Silver Snoopy Award for discovery and disposition of critical damage to the robotic arm prior to the Space Shuttle STS-121 mission.[

16. The Silver Snoopy Award. Now I'm impressed. He sounds like your kind of tech.

17.

18. Originally Posted by Mayflow
One day humans will have nuclear fusion at personal use and we will also learn to use space as a medium of faster than light transportation.
I asked you to stop posting woo on the physics forum. Now I'm going to have to give you a few days off.

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