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### Author Topic: Why do people think Relativity predicts event horizons?  (Read 19213 times)

#### jeffreyH

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #25 on: 20/11/2013 03:17:26 »
Oh dear it's controversy time. I do believe in the frozen star hypothesis and for this reason. The matter at the surface of a star that is collapsing towards the schwarzschild radius will itself undergo time dilation as it nears this point. The total gravitation below the surface will be increasing and must induce time dilation on matter nearer the surface. Otherwise time dilation just fails totally. As this matter at the surface approaches the horizon it to will take an ever longer time to get there. You can't have one rule for matter off the surface and another for the infalling surface itself. It too is effected by the gravitation from its own centre of gravity.

As an update, you can take this dilation all the way to the centre of the mass. If you take as your measurement half the radius of the collapsing mass then as this collapses internally it will also approach its own event horizon. As before the mass at its assumed surface will also take an infinite time to reach its own event horizon.

I have been asking questions such as what will fit inside a Planck volume to see if anyone else was thinking along these lines but few took that one up. There is usually a reason for the strange questions I ask.

Right. I imagine a neutron star on the verge of collapse to a black hole having that last little bit of matter dropped onto it like the straw that broke the camel's back. The nucleation point (where the collapse begins) will be at the surface, where gravity is most intense. As the matter begins falling together and approaches the Schwarzschild limit, spacetime stretching will hold it apart, almost frozen.

Well the original question was too vague. The better one is at the surface of the earth under gravitation how many planck volumes would be needed to contain a proton? If we calculated this then from that we worked out say how many planck volumes would be needed to contain 1kg of a mass. If we then work out what the schwarzschild radius for the 1kg mass would be and calculated how many planck volumes would contain it we may find the absolute mass-energy density ratio. As this would be an absolute just as the speed of light and absolute zero are we would resolve the breakdown in relativity. This would also rid physics of the singularity. The big bang would then be simply caused by quantum fluctuations of the collapse of a previous universe to cause the expansion by simply ejecting enough mass over a very long period of time so that the mass expands away from its schwarzschild radius.

#### yor_on

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #26 on: 20/11/2013 12:03:18 »
Android, the thing about infalling past a event horizon is that it also is about frames of reference. If you have a far observer, as well as a observer falling past then the far observer will see what you speculate about. The infalling observer 'stopping' before it ever reach past that event horizon, alternatively 'fading out' for him as the redshift should quench the light, the redshift comes from the light paths having to propagate 'uphill', away from a black holes gravitation. If we turn it around the observer infalling might at some point, see a 'infinite blue shift', assuming him able to stay still (which actually means him 'accelerating') just before a event horizon, looking out at a universe. I'm not sure what you mean by writing "The simplest is to drop a mirror into the black hole and shine a beam of light off of it and observe the reflection. Because the beam retraces its path into the gravity well, any gravitational redshift is eliminated." The beam does not get the redshift eliminated by 'retracing itself' as far as I know, it's about gravity that one, and about a direction/vector/velocity relative that center of 'infinite mass'. There is no way it can retrace its light path either, as we have a dynamic SpaceTime, in where ones local arrow always 'moves', even if assuming everything else (matter and its motion) to be 'static/unmoving' in a SpaceTime. As for lowering anything to a event horizon? That one is tricky and I've seen a lot of takes on that one :) as have you I guess.

So two observers do not need to agree on a time taken, that is what relativity is about. The infalling observer will find light moving at, 'c' as will the far observer', and splitting 'c' you can get to a local arrow. That becomes a 'shared global background/constant' of time keeping as I see it, always locally defined though. And as the infalling observer find 'c' the universe acts as usual for him, his arrow of time ticking. What happens inside a event horizon with the room/time should be any-body's guess, it depends on mass, angular momentum, and what frame of reference you use/imagine to measure it by.

But locally there are no weird things happening, only when you start comparing your frame of reference to another will time dilations, Lorentz contractions (and expansions) become noticeable. So the infalling observer must pass that event horizon, locally defined.
=

You may have spagettifications etc, naturally, caused by tidal forces, But what I mean is that there is nothing strange about any of it, they are perfectly explainable phenomena. And the infalling observer, inside a black box, ignoring tidal forces, will pass that event horizon, never noticing anything out of order locally.
==

Try this one http://www.universetoday.com/1605/
« Last Edit: 20/11/2013 12:56:07 by yor_on »

#### Bill S

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #27 on: 20/11/2013 18:15:03 »
Quote from: AndroidNeox
Question: How long will it take to accelerate the object to the speed of light?

Question: How much energy will be required to accelerate the object to the speed of light?

"Infinitely long" = you can't get there.

"Infinite energy" = you'll never have enough energy.

Infinity cannot be established by experiment; it is always a conjecture.

#### AndroidNeox

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #28 on: 20/11/2013 23:57:48 »

Sometimes infinity really is infinity. Relativity has some. For example, if you apply some finite acceleration to an object with non-zero rest mass, like a bowling ball or a proton:

Question: How long will it take to accelerate the object to the speed of light?

That position sounds all well and good but what about the inflationary period following the big bang? It is surmised that during this event, the speed of light was exceeded, and it didn't take eternity or infinitely long to reach.

The limitation of c is a matter of the geometry of spacetime. But, superluminal inflation is allowed by Relativity because nothing's moving through spacetime faster than c. Rather, spacetime itself is stretching and 'pulling' along the matter within it.

#### yor_on

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #29 on: 21/11/2013 16:46:23 »
Don't know why people keep arguing that ftl is relativity too? Relativity builds on 'c', nothing other. As soon as you discuss ftl you go away from relativity. It's like saying that as relativity builds on comparing frames of reference, from a 'inside' of a universe, it also state that there is a 'outside'. Relativity is defined from a inside, and has a limit of communication related the speed of light in a vacuum. FTL is something different, and also outside the borders of relativity.
=

The expansion is a additive thing as I get it, over long empty stretches a 'accelerating expansion of a vacuum' will be able to expand faster than a light beam can propagate.

"The Hubble constant tells us that - for every megaparsec of distance between two galaxies-, - the apparent speed at which the galaxies move apart from each other is greater by 71 kilometers per second -.

Since we know that the speed of light is around 300,000 kilometers per second, it is easy to calculate how far away two galaxies must be in order to be moving away from each other faster than the speed of light. The answer we get is that the two galaxies must be separated by around 4,200 megaparsecs (130,000,000,000,000,000,000,000 kilometers). " http://curious.astro.cornell.edu/question.php?number=575

The speed of light is defined as a distance light propagate in a vacuum, relative a defined time. About 300.000 km per second. Light does not do FTL. An expansion is neither a 'thing' propagating ftl. It's a distance widening, consisting of nothing at all classically.

Easiest to see if you imagine a acceleratingly expanding vacuum, in where you is the only thing existing observing that 'expansion'. Feel free to show me how to do that.
« Last Edit: 21/11/2013 17:14:26 by yor_on »

#### AndroidNeox

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #30 on: 26/11/2013 06:11:33 »
Don't know why people keep arguing that ftl is relativity too? Relativity builds on 'c', nothing other. As soon as you discuss ftl you go away from relativity.

You're right. I haven't responded sooner because I hadn't fully considered this. I've been intellectually sloppy and let the statements of others slide past without questioning. But, you're right. If there are any conditions under which something can exceed c, no matter the mechanism, relativity is violated.

I think I have a model that would both satisfy this most conservative interpretation of relativity and the observed smoothness of the cosmos but I need another day or so to think about it.

Thank you for your posting. You make a very good point.

#### Pmb

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #31 on: 27/11/2013 11:14:19 »
Quote from: AndroidNeox
Don't know why people keep arguing that ftl is relativity too? Relativity builds on 'c', nothing other. As soon as you discuss ftl you go away from relativity.
That's incorrect. Particles which can travel faster than the speed of light can exist and is consistent with special relativity.

The type of particles that can travel FTL are called tachyons. These are particles that are created moving faster than the speed of light. What SR says can’t happen is that  a particle with real and finite proper mass cannot be accelerated from v < c to a speed v > c. Otherwise there's nothing wrong with particles (aka tachyons) being created which are moving faster than the speed of light. G. Feinberg showed this to be true and called that class of particles tachyons.

The original article which postulates the existence of FTL particles and which coins the term tachyon is Possibility of Faster-Than-Light Particles, Feinberg, G. (1967), Physical Review, 159 (5): 1089–1105. You can download and read the article from here -- http://www.relativitycalculator.com/images/superluminal_velocities/possibility_faster_than_light.pdf

Quote
We consider the possibility of describing, within the special theory of relativity, particles with spacelike four-momentum, which therefore have velocities greater than that of light in vacuum. The usual objections to such particles are discussed, and they are found to be unconvincing within the framework of relativistic quantum theory. A quantum field theory of noninteracting, spinless, faster-than-light particles is described. The field theory is Lorentz-invariant, but must be quantized with Fermi statistics. The associated particle theory has the property that the particle number is not Lorentz-invariant, and the no-particle state is not Lorentz-invariant either. Nevertheless, the principle of relativity is satisfied. The Lorentz invariance implies a relation between emission and absorption processes, in contradiction to the usual case. Some comments are made about the problem of introducing interactions into the field theory. The limiting velocity is c, but a limit has two sides.

Please note the important part in that abstract – The usual objections to such particles are discussed, and they are found to be unconvincing within the framework of relativistic quantum theory.

Quote from: AndroidNeox
But, you're right. If there are any conditions under which something can exceed c, no matter the mechanism, relativity is violated.
That is incorrect. It’s a not uncommon error based on a misunderstanding of special relativity.

Quote from: AndroidNeox
Thank you for your posting. You make a very good point.
Nope. He’s normally spot on but on this point he’s quite wrong.

Here’s a much more recent paper on the subject of tachyons. Faster-than-light speeds, tachyons, and the possibility of tachyonic neutrinos by Robert Ehrlich, Am. J. Phys., 71(11), Now. (2003)
Quote
Faster-than-light speeds and hypothetical FTL particles known as tachyons are exciting subjects for students, given their speculative and controversial nature. This article presents an overview of these subjects and their role in special relativity and examines the possibility that one or more of the three neutrinos is a tachyon. The paper also describes several low tech demonstrations useful for teaching about faster-than-light speeds and tachyons in intermediate and advanced introductory college-level physics courses.
« Last Edit: 27/11/2013 16:26:18 by Pmb »

#### Pmb

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #32 on: 27/11/2013 11:21:51 »
Quote from: yor_on
Don't know why people keep arguing that ftl is relativity too?
Because the existance of particles which always move faster than the speed of light (known as a tachyon) is not inconsistent with special relativity (SR). All SR says is that you can't accelerate a particle (with real, non-zero proper mass) from a speed less than the speed of light to a speed equal to or greater than the speed of light. It doesn't say that a tachyon can't exist or that it's inconsistent with their existance. Where did you get the idea otherwise?

Quote from: yor_on
Relativity builds on 'c', nothing other. As soon as you discuss ftl you go away from relativity.
Nope.

Quote from: yor_on
FTL is something different, and also outside the borders of relativity.
Nope.

#### AndroidNeox

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #33 on: 27/11/2013 19:46:42 »
"The Hubble constant tells us that - for every megaparsec of distance between two galaxies-, - the apparent speed at which the galaxies move apart from each other is greater by 71 kilometers per second -.

Since we know that the speed of light is around 300,000 kilometers per second, it is easy to calculate how far away two galaxies must be in order to be moving away from each other faster than the speed of light. The answer we get is that the two galaxies must be separated by around 4,200 megaparsecs (130,000,000,000,000,000,000,000 kilometers). " http://curious.astro.cornell.edu/question.php?number=575

This distance works out to be the radius of the observable universe, 13.8 billion light years.

I've been considering the excellent point you make, that not even spacetime expansion allows for FTL, and how that relates to cosmological models based on rapid (FTL) inflation of space in the early universe. Rather than take this thread off-topic it might be more appropriate to start a different thread. Because it's my own theory, I've put it in the Theories forum under the Lighter section: Causality, the Big Bang, and the Shape of the Cosmos.

#### Pmb

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #34 on: 27/11/2013 20:16:54 »
Quote from: AndroidNeox
I've been considering the excellent point you make, that not even spacetime expansion allows for FTL, ..
Since when? Two galaxies can be traveling away from each other faster than the speed of light as a result of the epxasion of space. What are you referring to?

#### yor_on

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #35 on: 28/11/2013 12:48:47 »
It's not relativity Pete, not as I think of it. It may be consistent with an assumption of what may exist outside 'c', but it's a mathematical hypothesis to me. 'c' is relativity to me, with the equivalence principle becoming its extension to gravity. I suspect I will continue to argue that 'c', as a limit, is correct for all frames of reference, as long as we do not involve weird definitions of ftl, as defining a expansion as being ftl. Or lights propagation in matter proving ftl. You can define both without involving ftl as I think.
=

I have a different take on it as I expect 'c' and a arrow of time to be locally equivalent. Using scales and that definition a arrow seems to disappear under Planck scale. And how do I define any speed, without a arrow?
« Last Edit: 28/11/2013 13:12:06 by yor_on »

#### yor_on

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #36 on: 28/11/2013 13:07:01 »
Did Einstein really consider tachyons?
Not as I get it? Did he?

https://en.wikipedia.org/wiki/Tachyon

As far  as I get it this is a term created by "Gerald Feinberg (27 May 1933, New York City – 21 April 1992, New York City)" and he thought of it in terms of analyzing their quantum field properties. "In the 1967 paper that coined the term, Feinberg proposed that tachyonic particles could be quanta of a quantum field with negative squared mass. However, it was soon realized that excitations of such imaginary mass fields do not in fact propagate faster than light, and instead represent an instability known as tachyon condensation. Nevertheless, negative squared mass fields are commonly referred to as "tachyons", and in fact have come to play an important role in modern physics."

#### Pmb

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #37 on: 28/11/2013 15:10:40 »
Quote from: yor_on
It's not relativity Pete, not as I think of it.
Actually it is relativity as the physics community thinks of it.

Quote from: yor_on
It may be consistent with an assumption of what may exist outside 'c', but it's a mathematical hypothesis to me.
Here you've taken a tangent to the conversation. What are you talking about when you say exist outside 'c'?  Also, there are no mathematical hypotheses in SR, only physical ones.

Quote from: yor_on
'c' is relativity to me, …
That’s fine but irrelevant since we’re not talking about particles moving at the speed of light here. And even if we were we all know that SR let’s particles move at the speed of light. A particle that always moves at the speed of light is called a Luxon.

Quote from: yor_on
I suspect I will continue to argue that 'c', as a limit, is correct for all frames of reference, as long as we do not involve weird definitions of ftl, as defining a expansion as being ftl.
I simply don’t understand why you brought “c”: into this discussion? Why? Where does it fit into it?

Quote from: yor_on
And how do I define any speed, without a arrow?
Only velocity requires an “arrow,” not speed since speed is the magnitude of the velocity vector.

Quote from: yor_on
Did Einstein really consider tachyons?
No. However relativity isn’t defined strictly by the applications he mentioned in that article.

Quote from: yor_on
As far  as I get it this is a term created by "Gerald Feinberg (27 May 1933, New York City – 21 April 1992, New York City)" and he thought of it in terms of analyzing their quantum field properties. "In the 1967 paper that coined the term, Feinberg proposed that tachyonic particles could be quanta of a quantum field with negative squared mass. However, it was soon realized that excitations of such imaginary mass fields do not in fact propagate faster than light, and instead represent an instability known as tachyon condensation. Nevertheless, negative squared mass fields are commonly referred to as "tachyons", and in fact have come to play an important role in modern physics."
I don’t know what …that excitations of such imaginary mass fields do not in fact propagate faster than light[/quote] means since its conceivable that tachyons exist and if they do their mass will be imaginary.

#### yor_on

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #38 on: 28/11/2013 16:57:00 »
Then you can direct me to where Einstein discuss tachyons? I looked for it but couldn't find it Pete. As far as I can see it seems to be a later addition to relativity? Ahh, okay. Saw you write he didn't. Well, if the physics community thinks it to exist :) I don't.

#### yor_on

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #39 on: 28/11/2013 16:58:20 »
How do you get to the "magnitude of the velocity vector." without a arrow?
=

As for why I don't think about it that way (ftl existing) has a lot to do with how I think of indeterminacy, instead of virtual particles (of such short 'time sequences' that they doesn't 'exist') too. It's something not having to do with how we define as a speed at all, to me that is. A indeterministic property that you can use statistics and probability for, but not a speed.

I've wondered about the definition of 'virtual particles before Pete. In Are virtual particles exclusively virtual, or do some exist in reality too?

And the link I have there is still good, as I think. http://www.mat.univie.ac.at/~neum/physfaq/topics/virtual

I can put it this way too, as a reason. Scaling something down we meet statistics and probability, quantum entanglements and lights duality. But I can't see how it would change the measurements we make macroscopically, scaling a universe up instead of down, from where we find ourselves at a daily basis. It's when scaling down I meet those 'new' QM phenomena, as far as I know that is. Scaling up 'c' will be 'c', scaling down we meet Planck scale.
=

look at : Aharonov, Y.; Komar, A.; Susskind, L. (1969). "Superluminal Behavior, Causality, and Instability". Phys. Rev. (American Physical Society) 182 ({5},): 1400–1403. Bibcode:1969PhRv..182.1400A. doi:10.1103/PhysRev.182.1400 for "However, it was soon realized that excitations of such imaginary mass fields do not in fact propagate faster than light." You can find direct links to it in https://en.wikipedia.org/wiki/Tachyon
« Last Edit: 28/11/2013 17:57:04 by yor_on »

#### Pmb

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #40 on: 28/11/2013 22:49:17 »
Quote from: yor_on
Well, if the physics community thinks it to exist :) I don't.
Yes. We know that you don’t think so. Therefore you don’t have to keep repeating it.

Also, nobody said that the physics community thinks tachyons exists. That article I quoted only states that they haven’t ruled out one of he neutrinos as being a tachyon. All that I said was that the physics community knows that the existence of a tachyon does not contradict the principles of relativity.

Tell you what. To demonstrate this I recommend that you attempt to prove that the existence of tachyons proves SR is wrong. You’ll find that it’s impossible to do so.

#### Pmb

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #41 on: 28/11/2013 22:51:16 »
Quote from: yor_on
How do you get to the "magnitude of the velocity vector." without a arrow?
=

As for why I don't think about it that way (ftl existing) has a lot to do with how I think of indeterminacy, instead of virtual particles (of such short 'time sequences' that they doesn't 'exist') too. It's something not having to do with how we define as a speed at all, to me that is. A indeterministic property that you can use statistics and probability for, but not a speed.
They have nothing to do with each other.

#### AndroidNeox

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #42 on: 03/12/2013 18:09:30 »

Sometimes infinity really is infinity. Relativity has some. For example, if you apply some finite acceleration to an object with non-zero rest mass, like a bowling ball or a proton:

Question: How long will it take to accelerate the object to the speed of light?

That position sounds all well and good but what about the inflationary period following the big bang? It is surmised that during this event, the speed of light was exceeded, and it didn't take eternity or infinitely long to reach.

The only justification for the idea that the cosmos underwent a period of superluminal inflation immediately after the Big Bang is the homogeneity of matter through space. That's it. It's just a means to explain uniformity.

#### AndroidNeox

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #43 on: 03/12/2013 18:20:30 »
Quote from: AndroidNeox
I've been considering the excellent point you make, that not even spacetime expansion allows for FTL, ..
Since when? Two galaxies can be traveling away from each other faster than the speed of light as a result of the epxasion of space. What are you referring to?

No such thing is observable. To quote a phrase, "What are you referring to?"

#### Pmb

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #44 on: 04/12/2013 02:32:55 »
Quote from: AndroidNeox
No such thing is observable. To quote a phrase, "What are you referring to?"
A well known and widely accepted part of the Big Bang theory is that some galaxies recede from us faster than the speed of light due to what is known as universal expansion. See http://en.wikipedia.org/wiki/Faster-than-light#Universal_expansion
Quote
The expansion of the universe causes distant galaxies to recede from us faster than the speed of light, if comoving distance and cosmological time are used to calculate the speeds of these galaxies.

Quote
Question: How Can Galaxies Move Away Faster Than Speed of Light?

Answer: Einstein’s Theory of Relativity says that the speed of light – 300,000 km/s – is the maximum speed that anything can travel in the Universe. It requires more and more energy to approach the speed of light. You could use up all the energy in the Universe and still not be traveling at light speed.

As you know, most of the galaxies in the Universe are expanding away from us because of the Big Bang, and the subsequent effects of dark energy, which is providing an additional accelerating force on the expansion of the Universe.

Galaxies, like our own Milky Way are carried along by the expansion of the Universe, and will move apart from every other galaxy, unless they’re close enough to hold together with gravity.

As you look at galaxies further and further away, they appear to be moving faster and faster away from us. And it is possible that they could eventually appear to be moving away from us faster than light. At that point, light leaving the distant galaxy would never reach us.
Such rapidly moving galaxies are said to have a high value of cosmological redshift. z . If z is large enough then that galaxy is moving FTL as reckoned by observers at rest in one of the two galaxies.

#### AndroidNeox

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #45 on: 09/12/2013 19:53:10 »
Quote from: AndroidNeox
No such thing is observable. To quote a phrase, "What are you referring to?"
A well known and widely accepted part of the Big Bang theory is that some galaxies recede from us faster than the speed of light due to what is known as universal expansion. See http://en.wikipedia.org/wiki/Faster-than-light#Universal_expansion
Quote
The expansion of the universe causes distant galaxies to recede from us faster than the speed of light, if comoving distance and cosmological time are used to calculate the speeds of these galaxies.

Using the Hubble "constant", the recession rate of matter at the observable horizon is the speed of light. Everything in our universe seems to be within this bubble of space.

Comoving distances have no real justification in science and certainly not in Relativity. The comoving distance is a value based on a godlike perspective outside of spacetime. While it might have value as a way of speculating how things might work, it's unobservable and has no real physical consequence.
Quote
Quote
Question: How Can Galaxies Move Away Faster Than Speed of Light?

Answer: Einstein’s Theory of Relativity says that the speed of light – 300,000 km/s – is the maximum speed that anything can travel in the Universe. It requires more and more energy to approach the speed of light. You could use up all the energy in the Universe and still not be traveling at light speed.

As you know, most of the galaxies in the Universe are expanding away from us because of the Big Bang, and the subsequent effects of dark energy, which is providing an additional accelerating force on the expansion of the Universe.

Galaxies, like our own Milky Way are carried along by the expansion of the Universe, and will move apart from every other galaxy, unless they’re close enough to hold together with gravity.

As you look at galaxies further and further away, they appear to be moving faster and faster away from us. And it is possible that they could eventually appear to be moving away from us faster than light. At that point, light leaving the distant galaxy would never reach us.
Such rapidly moving galaxies are said to have a high value of cosmological redshift. z . If z is large enough then that galaxy is moving FTL as reckoned by observers at rest in one of the two galaxies.

The current interpretation of Relativity is that nothing can exceed c within spacetime but that spacetime can be deformed or stretched at any rate. Maybe, maybe not. I only noted that yor_on had made a valid point, that no matter what the mechanism, no superluminal effects can be observed.

Again, the only justification for suggesting a period of rapid inflation immediately after the Big Bang is the uniformity of the distribution of matter throughout the observable universe.

I think it's much more likely that we are NOT in a unique period in the history of the cosmos. It seems more likely to me that most of the facts discounted as coincidences are in fact consequences of rules we don't fully appreciate.

For example, anything emitted at time = zero and travelling at the speed of light would be within our observable horizon. Since matter was probably dense and hot enough to be opaque then, we couldn't receive light from there/then. But, we should still receive light from the surface of last scattering. Contemporary thought has it that accelerating spacetime inflation will push that outside of our observable horizon. Maybe, but there are other possibilities.

The instantaneous appearance of the observable universe satisfies (to within 3%) the requirements for a Schwarzschild black hole: zero spin, zero charge, and radius/mass = 2G/c2. If this is a requirement and not a coincidence then one requirement would be that matter would accelerate apart at an increasing rate. This is because the radius and mass would be directly proportional but, because the observable universe is a spherical volume, the mass density would have to drop off in proportion to (age of universe)2.

#### yor_on

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #46 on: 09/12/2013 21:13:30 »
The idea behind a inflation is not a 'speed' per se, not to me at least. If I want to give a inflation a speed I first have to define some origin from where I can use a clock and ruler to measure that 'speed' with. Inside a vacuum, without reference points, that should be a impossibility as I think. Also it is so that if there is no center to a universe, neither it should be to inflation or a expansion, meaning that inflation should be in all 'points', to make sense to me. to call it ftl presumes a ruler and a clock to measure it by, with reference points.
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So, using my own arguments here, you might be able to call a accelerating expansion for 'ftl' :) but a 'ftl' is defined by a locally measured 'infinite blueshift' (and redshift depending on 'motion') at least as we move uniformly relativistically close to light, relative some reference point . Earth should also be doing 'ftl', or just under then, depending on what possible reference star we want to use to measure that 'speed' relative. Do we find a local infinite blueshift in some direction? And a infinite redshift in the opposite?

And one also have to remember that we can pick any reference point (as a star) we want, to get to different uniform 'speeds', depending on the distance measured between our reference points. The only measurable way to relate a speed to a uniform motion is relative some other object, as a star, or the CBR, or just measure incoming light. But it's all dependent on your reference points as it seems to me.
« Last Edit: 09/12/2013 21:27:14 by yor_on »

#### Pmb

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #47 on: 11/12/2013 00:37:01 »
Quote from: AndroidNeox
Comoving distances have no real justification in science and certainly not in Relativity.
Wow! Where did this from? Nobody mentioned them in this thread I can see so I don’t understand why you raised the subject? Please explain.

By the way, there’s no such thing as a commoving distance. I was talking about commoving coordinate. The justification in relativistic cosmology is their usage. That usagage is as an identifier of the location of the galaxy, i.e. as a sort of “address” of the galaxy.

The comoving distance is a value based on a godlike perspective outside of spacetime.
[//quote]
The same can be said of your house.

Quote from: AndroidNeox
While it might have value as a way of speculating how things might work, it's unobservable and has no real physical consequence.
Their physical reality is their use as a way to locate a galaxy in the cosmos relative to the established coordinate system.

Quote from: AndroidNeox
The current interpretation of Relativity is that nothing can exceed c within spacetime but that spacetime can be deformed or stretched at any rate. Maybe, maybe not.
In the wonderful world of physics, in this case the branch known as relativistic cosmology, it’s the way it is according to current theory and as verified by observation. Outside that theory I have no interest in discussing. First publish it and then I’ll talk to you about it. I don’t do “new theory” here.

#### AndroidNeox

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #48 on: 11/12/2013 19:14:52 »
The idea behind a inflation is not a 'speed' per se, not to me at least. If I want to give a inflation a speed I first have to define some origin from where I can use a clock and ruler to measure that 'speed' with.
Redshift. Identify the spectrum of some common element, like hydrogen, and look for it redshifted.

#### AndroidNeox

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##### Re: Why do people think Relativity predicts event horizons?
« Reply #49 on: 11/12/2013 19:21:14 »
Quote from: AndroidNeox
Comoving distances have no real justification in science and certainly not in Relativity.
Wow! Where did this from? Nobody mentioned them in this thread I can see so I don’t understand why you raised the subject? Please explain.