Universe Expansion Speed: Einstein's Theory Impacted?

[Stonefeather]

How fast is the universe expanding? I have heard it is near light speed. If this is the case does it throw a monkey wrench into Einstiens theorys? What I am really asking is if the Earth is acctually moveing at near lightspeed say this . is earth. and this 0 is the sun, also say that the universe is expanding this way <- Would not light move faster with the Earth in this position .0 than with it in this position 0. ?

 

[Blistering Peanut]

I don't think the universe would be expanding in only one direction but equally in all directions.

 

[Kurdt]

It doesn't throw a spanner in special relativity because with the Earth in both positions the light from the sun would be measured as exactly c.

 

[selfAdjoint]

How fast is the universe expanding? I have heard it is near light speed. If this is the case does it throw a monkey wrench into Einstiens theorys? What I am really asking is if the Earth is acctually moveing at near lightspeed say this . is earth. and this 0 is the sun, also say that the universe is expanding this way <- Would not light move faster with the Earth in this position .0 than with it in this position 0. ?

The stars and planets, including sun and earth, are not actually moving through space at the expansion speed. Rather space itself is expanding. The galaxies are getting farther apart without moving. And that increase can go faster than light, and it does. They can measure it using doppler effect on the spectra of distant objects.

 

[Erring Flatley]

The universe may not be expanding. The theory of expansion is based on the red shift observed in the light from distant galaxies. If the red shift is caused by an energy shift from wavelength to photon numbers instead of a Dopler shift, then the universe is not receeding from us, but rather standing in a stationary pattern. This kind of an energy shift could expain the comic microwave background radiation, which is found everywhere. [/color]

 

[Nereid]

The universe may not be expanding. The theory of expansion is based on the red shift observed in the light from distant galaxies. If the red shift is caused by an energy shift from wavelength to photon numbers instead of a Dopler shift, then the universe is not receeding from us, but rather standing in a stationary pattern. This kind of an energy shift could expain the comic microwave background radiation, which is found everywhere. [/color]

Welcome to Physics Forums Erring Flatley!

Do you have a reference to this idea that "the red shift [of galaxies] is caused by an energy shift from wavelength to photon numbers instead of a Dopler shift"? Or more details of what this is, including some equations and numbers?

 

[Mike2]

The stars and planets, including sun and earth, are not actually moving through space at the expansion speed. Rather space itself is expanding. The galaxies are getting farther apart without moving. And that increase can go faster than light, and it does. They can measure it using doppler effect on the spectra of distant objects.

Then wouldn't it appear that we are moving faster than light if we are simply being carried by space as space expands FTL?

What is there to hinder the expansion, especially during inflation? It would seem that there must be some quality of space itself that prevents an infinite expansion rate.

 

[selfAdjoint]

Then wouldn't it appear that we are moving faster than light if we are simply being carried by space as space expands FTL?

What is there to hinder the expansion, especially during inflation? It would seem that there must be some quality of space itself that prevents an infinite expansion rate.

Moving faster than light relative to what? We are in our own rest frame, and it includes much of what we see locally; we aren't speeding much with respect to the nearer stars or the milky way. We have a very small proper motion with respect to the CMB. Study up the Lineweaver site or some other resource on cosmology.

The universe has expanded in the past by size orders of 10^{30} in a very short time (inflation), amd may well do so again. It's wrong to think of space, or spacetime as a physical membrane.

 

[Erring Flatley]

It is my own idea. It is based on my idea of photon-photon interaction under the unified field equation. Most assume that photons do not interact as they contact each other but they do! Coherence could not occur if they did not. (Please excuse me, I must sign off now, be back latter.)[/color] [/color]

 

[Mike2]

Moving faster than light relative to what? We are in our own rest frame, and it includes much of what we see locally; we aren't speeding much with respect to the nearer stars or the milky way. We have a very small proper motion with respect to the CMB. Study up the Lineweaver site or some other resource on cosmology.

The universe has expanded in the past by size orders of 10^{30} in a very short time (inflation), amd may well do so again. It's wrong to think of space, or spacetime as a physical membrane.

If we are still with respect to our local space (that's expanding) and some far away galaxy is still wrt it's local space, then if space itself is expanding FTL, then the two galaxies are speeding away from each other FTL. Although there is probably no such thing as still wrt local space, still the point is made. If there is an expansion of space, then there is a frame relative to that expansion, right?

Is there some topological property where the connectedness of space with time would require a maximum speed of expansion? Would that require a metric? As I've argued before, space must have the topological property of being connected if anything is going to propagate through it. And likewise, time must be connected or there is no propagation through it. So propagation itself implies a connected property of both time and space. But how is time connected to space?

 

[Mike2]

If the universe expanded from a singularity, then to begin with so much space was added with so much time. If each point of spacetime always has this same rate of expansion, then doesn't this imply an exponential growth in the expansion? And isn't this what we are told about inflation? Comments please?

 

[billy_boy_999]

space-time is expanding at the speed of light, this is why light and gravity propagate at such constant, certain speeds...

 

[Mike2]

If the universe expanded from a singularity, then to begin with so much space was added with so much time. If each point of spacetime always has this same rate of expansion, then doesn't this imply an exponential growth in the expansion? And isn't this what we are told about inflation? Comments please?

In other words, the rate is proportional to the size, more points contributing at the same rate, then the more points there are, the faster the overall rate of expansion. Does this make sense?

 

[Erring Flatley]

Welcome to Physics Forums Erring Flatley!

Do you have a reference to this idea that "the red shift [of galaxies] is caused by an energy shift from wavelength to photon numbers instead of a Dopler shift"? Or more details of what this is, including some equations and numbers?

According to my reading, many decades ago when Hubble first demonstrated the cosmic red shift and gave a rate of expansion, which gave an age to the universe, Hubble's age for the universe was less than the accepted geological age of the Earth. Many astrophysicists proposed a theory called "the tired light" theory, to account for the shift to red. It was of course not a theory based on Dopler shift. But no one was able to find an explanation for light shifting its wavelength other than by Dopler shift. Other astronomers revised Hubble's estimate to be greater than the age of the Earth and with that the tired light hypothesis died. But, my study of the unified field equation would say that a shift from wavelength to photon numbers is possible and that reawakens the tired light hypothesis. The big bang theory rests heavily on the cosmic red shift being Dopler. If I am right that only leaves observations from the Hubble space telescope ultra-deep field photos of galaxies as being "young" in support of the big bang theory. And that is up to personal interpretation with so little seen so far. [/color]

 

[AntiMagicMan]

Whenever you look at expanding spacetime you have to use General Relativity. And it is a little known fact that in the General Theory spacetime can expand faster than light.

 

[Nereid]

According to my reading, many decades ago when Hubble first demonstrated the cosmic red shift and gave a rate of expansion, which gave an age to the universe, Hubble's age for the universe was less than the accepted geological age of the Earth. Many astrophysicists proposed a theory called "the tired light" theory, to account for the shift to red. It was of course not a theory based on Dopler shift. But no one was able to find an explanation for light shifting its wavelength other than by Dopler shift. Other astronomers revised Hubble's estimate to be greater than the age of the Earth and with that the tired light hypothesis died. But, my study of the unified field equation would say that a shift from wavelength to photon numbers is possible and that reawakens the tired light hypothesis. The big bang theory rests heavily on the cosmic red shift being Dopler. If I am right that only leaves observations from the Hubble space telescope ultra-deep field photos of galaxies as being "young" in support of the big bang theory. And that is up to personal interpretation with so little seen so far. [/color]

You may find the
Ned Wright cosmology website of some interest, in particular his discussion of the 'tired light' hypothesis (in a word, observations of distant supernovae are inconsistent with the tired light hypothesis), as well as http://math.ucr.edu/home/baez/RelWWW/wrong.html#bang , which summarises the observational results which support the big bang theory (in four words: the Hubble expansion, the cosmic microwave background, the primordial abundance of light nuclides, and large-scale structure).

 

[Mike2]

Whenever you look at expanding spacetime you have to use General Relativity. And it is a little known fact that in the General Theory spacetime can expand faster than light.

So if that expansion were unhindered by mass or whaterver, is there something in GR that predicts an expansion at an exponential rate?

I'm told GR requires initial conditions to predict how fast expansion takes place. What if the universe started from a singularity in the infinite past (no t=0, no initial conditions)?

 

[selfAdjoint]

First of all, the expansion is not indifferent to mass. If there was sufficient mass the universe would reach a max and then contract. But mass is only a couple of percent of the total energy budget.

The GR explanation for the acceleration is the cosmological constant, that is, the form of Einstein's equations, not just the initial conditions. As Nereid has said, we don't know what the initial conditions were.

 

[Blueplanetbob]

Is the dark energy density moving faster than light speed?

 

[Nereid]

Is the dark energy density moving faster than light speed?

Welcome to Physics Forums Blueplanetbob!

I'm not sure I understand your question ... 'dark energy' is just a shorthand for either a) whatever may be causing the acceleration of the expansion of the universe (i.e. a mystery), or b) one of several ideas that are NOT the cosmological constant (a la Einstein). In the former, your question has no meaning (what is the density of a mystery?); in the latter, 'dark energy density' would probably be a bulk property, so it wouldn't make sense to ask how fast it was moving!

 

[Blueplanetbob]

So dark energy is not a property of spacetime and is not affected by spacetime accelerating faster than light speed?