Does big rip have an acceleration gradient?

[tommac]

This is a question about big rip.

Lets assume that big rip was the fate of our universe ( I understand that evidence does not suggest this ), would there be an SR gradient that would be similar to the gravitational gradient of a BH?

Lets say that the the cosmic expansion got to the point that it was accelerating the sun away from the earth at hte speed of light. Could we look at the difference in acceleration as a gradient, as where the further you go away from the observer ( or the closer you got to the past singularity/EH ), the faster you would be accelerated. Wouldnt that be the same or similar to a gravitational/ GR gradient near an event horizon? If not what is the difference to the forces?

[tommac]

like if an observer was in an elevator, would they be able to differentiate being ripped apart by black hole tidal forces or being ripped apart by the big rip? Wouldnt even the radial components be similar?

[Cougar]

like if an observer was in an elevator, would they be able to differentiate being ripped apart by black hole tidal forces or being ripped apart by the big rip? Wouldnt even the radial components be similar?

Being spaghettified and being big-ripped would be quite different ways to go. One is mono-directional; the other is omni-directional.

[tommac]

Being spaghettified and being big-ripped would be quite different ways to go. One is mono-directional; the other is omni-directional.

No one is "fan in" the other is "fan out".

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The net result is similar except you getting elephantified instead of spaghettified. In other words, the tidal forces at work would pull your head away from your feet, but instead of the radial forces pushing inwards -> <-, it would push outwards. <- ->

[tommac]

Being spaghettified and being big-ripped would be quite different ways to go. One is mono-directional; the other is omni-directional.

How is spaghettification one directional? The whole point of spaghettification is that it is omni-directional. Think about it.

You have a bh ... as you FREE FALL into the black hole, you are semi weightless, however as you get closer there is a difference in the pull, a gradient persey. So that you feer ( if you are falling feet first, are pulled faster than your head. The net effect that you notice is that your feet are being pulled away from your head ... or your head is being pulled away from your feet ...

the force is:
<-H..T->

That is in the one direction ... BUT there is also something else that is going on, since there is a sphere of spacetime being collapsed into a circle ... the angle forces push inwards laterally. Like this

->h<-
->.-<
->t<-

this is what I am calling fan in.

The best illustration I have seen of this is in black holes and time warps by thorne, page 104 in my book under the sub topic tidal gravity and spacetime curvature

Note: if you were falling straight down, OR if the BH is sooooo big that the there isnt much tidal forces, to the point that they could get ignored, then you would not have any lateral forces acting on the body. However for smaller black holes, the tidal forces are significant .. thus the spagettification

[Andrew D]

like if an observer was in an elevator, would they be able to differentiate being ripped apart by black hole tidal forces or being ripped apart by the big rip? Wouldnt even the radial components be similar?

Think about this:

to avoid falling into a black hole, one must accelerate on a radial vector away from the singularity.

to avoid 'accelerating' due to cosmic expansion, along which direction must one accelerate?

[tommac]

Think about this:

to avoid falling into a black hole, one must accelerate on a radial vector away from the singularity.

to avoid 'accelerating' due to cosmic expansion, along which direction must one accelerate?

It is not that simple. The cosmic expansion is caused by co-moving variants as is as you are pointing out much more complex that a point of gravity. It is sort of like asking which direction should the raisin travel in the raisin bread. The deal is that it all is moving, and in that movement everything is moving away from everything else, in all directions. It is like asking if a gang of people are going to attack you, which way do you run? Away from them, right? Now you are asking, which way do you run if they have you totally surrounded.

[tusenfem]

What on Earth would be a "SR gradient?"
How can you have a gradient of a theory SR or GR?
Maybe you could google first a bit, and read up on stuff, and then if you don't understand it ask a question here, that is better worded that what you produce here.

[tommac]

What on Earth would be a "SR gradient?"
How can you have a gradient of a theory SR or GR?
Maybe you could google first a bit, and read up on stuff, and then if you don't understand it ask a question here, that is better worded that what you produce here.

Who knows ... but it seems to be important for Wayne.

The question I was trying to ask is about is really about tidal forces.
If an observer was in an elevator, and was approaching the EH of a Black Hole would the tidal forces be similar to another observer in an elevator being accelerated by an expanding universe with a scale factor that is approaching infinity?

Other than the "fan in" vs "fan out" effect is the tidal forces the same.

[Andrew D]

It is not that simple. The cosmic expansion is caused by co-moving variants as is as you are pointing out much more complex that a point of gravity. It is sort of like asking which direction should the raisin travel in the raisin bread. The deal is that it all is moving, and in that movement everything is moving away from everything else, in all directions. It is like asking if a gang of people are going to attack you, which way do you run? Away from them, right? Now you are asking, which way do you run if they have you totally surrounded.

The question was rhetorical. To answer your question, The observer in the elevator would definitely be able to tell the difference between gravitational tidal forces and big rip expansion forces, because tidal forces stretch/compress along specific axes. Big rip forces, on the other hand, would act symetrically on all axes.

[tommac]

The question was rhetorical. To answer your question, The observer in the elevator would definitely be able to tell the difference between gravitational tidal forces and big rip expansion forces, because tidal forces stretch/compress along specific axes. Big rip forces, on the other hand, would act symetrically on all axes.

Yes you are right ... but wouldnt this just be a 3d version of fanning out? Like lets take a giant that is much taller than wide ... whatever direction his head was pointing in would be pulled away from his toes ... his body would be what I am calling elephantified. But because of his height, there would be a bigger net force pulling his head and toes apart. Please correct me if I am wrong.

If the same thin giant was to fall into a black hole, he would experience the exact same tidal forces pulling his head and toes apart, but his body instead of being elephantified, is of course spaghettified.

Now as you have stated directly or indirectly previously, the giant would have to be perfectly aligned ( either head first or feet first ) falling into the black hole , while with the big rip ... it doesnt matter what direction his head is in.

But the differences are only 3-d fan in vs 3d fan out. i believe. Do you agree?

[Cougar]

But the differences are only 3-d fan in vs 3d fan out. i believe. Do you agree?

No. You seem to be counting only two directions -- up-down and left-right. Of course, there's forward-backward, too, but the main point is, with big rip expansion, you've got to count every direction in between. And every point in space acts equally, so the "forces" on your head are going to be no different than those on your feet, as well as the rest of your body.

It's like you're trying to equate the number 1 with infinity.

[Andrew D]

Yes you are right ... but wouldnt this just be a 3d version of fanning out? Like lets take a giant that is much taller than wide ... whatever direction his head was pointing in would be pulled away from his toes ... his body would be what I am calling elephantified. But because of his height, there would be a bigger net force pulling his head and toes apart. Please correct me if I am wrong.

No. there is no directionality to cosmic expansion. You can't switch the signs on the axes of gravitational tidal forces and call it cosmic expansion.

Now as you have stated directly or indirectly previously, the giant would have to be perfectly aligned ( either head first or feet first ) falling into the black hole , while with the big rip ... it doesnt matter what direction his head is in.

But the differences are only 3-d fan in vs 3d fan out. i believe. Do you agree?

His orientation is indeed arbitrary, but because the distances between the atoms in his body are growing. While they maintain their position relative to eachother. His body is the same shape after expansion, it's just that the particles that make him up are more diffuse because of the expansion. It's really a very simple concept.

[tommac]

Also, as a slight tangent here. Do we agree that the big rip would be able to split all virtual pairs if the universal scale factor approached infinity?

[WayneFrancis]

Tusenfem, blame me for that term. I use the term gradient when talking about gravitational wells. I like the word better then slope or...well can't think of another term right now. I first used it to try to explain to tommac why the early universe was not a black hole even though its energy density was very high.

I fear tommac wants to believe that with cosmological expansion there is a transfer of energy and momentum. He desperately wants the cosmological red shift to be a result of SR motion through space time. He refuses to learn the differences between the 3 types of red shifts and wants to use them interchangeably.

[tommac]

Tusenfem, blame me for that term. I use the term gradient when talking about gravitational wells. I like the word better then slope or...well can't think of another term right now. I first used it to try to explain to tommac why the early universe was not a black hole even though its energy density was very high.

I fear tommac wants to believe that with cosmological expansion there is a transfer of energy and momentum. He desperately wants the cosmological red shift to be a result of SR motion through space time. He refuses to learn the differences between the 3 types of red shifts and wants to use them interchangeably.

3 types of redshifts? Look red shift is red shift. There may be different causes of red shift but if light is red shifted it doesnt matter how it shifted.

Look at the big rip.

The Big Rip is a cosmological hypothesis first published in 2003, about the ultimate fate of the universe, in which the matter of the universe, from stars and galaxies to atoms and subatomic particles, are progressively torn apart by the expansion of the universe at a certain time in the future.

How is that much different than a Black Hole? If an observer was in an elevator, could he differentiate between being torn apart from a Black Hole's tidal forces or from the acceleration of the cosmos?

The tearing apart, Wayne, is from your "gradient", it is very similar to a black holes "gradient".

[WayneFrancis]

3 types of redshifts? Look red shift is red shift. There may be different causes of red shift but if light is red shifted it doesnt matter how it shifted.

Yes 3 different causes of red shift and their implications are not all the same. Your failure to listen to anyone that tries to explain the differences is very telling.

Light being red shifted is just like a symptom. Many things can cause a sore arm but tennis elbow is a lot different then a heart attack.

Look at the big rip.


How is that much different than a Black Hole? If an observer was in an elevator, could he differentiate between being torn apart from a Black Hole's tidal forces or from the acceleration of the cosmos?

The tearing apart, Wayne, is from your "gradient", it is very similar to a black holes "gradient".

Hmmm can a human that is killed almost instantly tell how they are being killed?
As others have pointed out a black hole spaghettification is very different then being from what a big rip would do.
Don't pin your misunderstanding of one concept on terms I use for a different one.

[captain swoop]

Tommac. Once again you ask a question and follow up the answers you are given by replying with a 'what if ATM' and then your own musings on the subject.
If your question has been answered then say thank you and move on. If it hasn't been answered then ask for clarification, don't put your own ideas.

[tommac]

Tommac. Once again you ask a question and follow up the answers you are given by replying with a 'what if ATM' and then your own musings on the subject.
If your question has been answered then say thank you and move on. If it hasn't been answered then ask for clarification, don't put your own ideas.

how is that possibly atm ? think about it ... it is not a question ... it is how it is ... if not please explain why it is wrong.

What would fan out act like?

[Tensor]

how is that possibly atm ? think about it ... it is not a question ... it is how it is ... if not please explain why it is wrong.

Are you saying a giant one light year long and one meter wide isn't ATM? Proof of this one I gotta see.

[tommac]

Are you saying a giant one light year long and one meter wide isn't ATM? Proof of this one I gotta see.

Funny

[WayneFrancis]

how is that possibly atm ? think about it ... it is not a question ... it is how it is ... if not please explain why it is wrong.

What would fan out act like?

Perhaps you should read what people have been telling you instead of ignoring their answers. It has been explained to you, you just refuse to accept it.

[tommac]

I drew something up quickly to show you what I was talking about:



http://www.spacetimeandtheuniverse.c...e-universe.jpg


Here you have 4 scenerios,
1) pancake-ification head toe acceleration compressing lateral acceleration expanding
2) spaghettification head toe acceleration accelerating lateral acceleration compressing
3) pea-ification ( pointification ) head toe acceleration compressing lateral acceleration compressing
4) elephantification head toe acceleration expanding lateral acceleration expanding

For #2 we have the BH ...
For #4 we have an expanding universe
#1 and #3 I am not sure .... I guess for #1 it would something like a negative mass black hole where acceleration diminished with distance for #3 ... not sure ... but maybe a contracting universe.

Please let me know if I got this right.

[WayneFrancis]

Does anyone want to wager me that tommac comes back and still won't admit that his view of tidal forces and cosmic expansion are not related in the way he's implying.

I'll guess he'll keep telling us we don't get it, latch onto something we've said and distort it and claim that someone is in agreement with him when in actuallity no one is.

[PetersCreek]

I'll guess he'll keep telling us we don't get it, latch onto something we've said and distort it and claim that someone is in agreement with him when in actuallity no one is.

He may do that in the ATM forum in the process of defending a new theory. But arguing mainstream answers in the Q&A forum on ATM priciples? Nope.

Thread closed.