Can we ever truly understand the concept of infinite speed?

[renerob]

Is it possible to conceive of a universe which had a beginning but is spatially infinite?

 

[marcus]

Is it possible to conceive of a universe which had a beginning but is spatially infinite?

I have trouble with the beginning part. I find it difficult to imagine a universe with a beginning (whether spatial finite or infinite doesn't matter.) Difficult but not altogether impossible.

If I can get past that, and imagine a universe with a beginning (somehow springing into existence in a state of infinite density) then it is not much harder to go further and picture it as spatially infinite at that moment when it jumps into existence.

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Among cosmologists who think of the universe as having a beginning it is not unusual for them to picture it as beginning with infinite spatial extent. The standard LambdaCDM model that cosmologists use can be either spatial finite or spatial infinite, and the spatial infinite version has space be infinite all the way back in time, for as long as time has meaning.
That is the most common model. So there has got to be no problem conceiving of it! It is the default version!

===================

Personally I prefer a recently developed variation on the standard model which has a bounce instead of a singularity. So there is no beginning in the picture. Before our expanding phase there was a contracting one, which reached a very high (but not infinite) density, stopped contracting, and began expanding. It fits the data as well as the version with a singularity. One reason I find it easier to picture is that I don't have to imagine a beginning of time. The model results from quantizing the classical cosmology model---quantizing gets rid of the singularity. But that is just my personal preference.

====================

A lot of cosmologists still use the classic unquantized LambdaCDM model, which hits a singularity as you go back in time, and you can't evolve back any further. And of them most still use the flat (infinite space) version. So they are conceptualizing exactly as you said! A beginning to time, and a spatial infinite universe as soon as time begins ticking.
So the answer to your question has got to be YES it is definitely conceivable.

Which is not to say that one personally one has to like it. There are alternatives.

 

[renerob]

Thank you, Marcus.
If that is the case, then could one also think that past a certain point the current universe is completely empty? And could that point be thought of as the "edge" of the universe?

 

[Garth]

Is it possible to conceive of a universe which had a beginning but is spatially infinite?

Yes, the standard GR model when the average density is not above the critical density, \Omega_{total} \leq 1, is infinite and unbounded and would have expanded from a Big Bang.

In pure unadulterated GR theory this would have been a singularity and may be described as a 'beginning'.

Garth

 

[LoreSpade]

Sorry guys i don't mean to but in here. but It seems that the universe is simply an illusion of time itself.

Lets just go into a little disscussion of how time works, and we will have a better understanding of how the universe was created, and the paridox of how it is impossible to have a start point or an end point for that matter. Due to human perception of time of working in a (Time-Frame) manner. We only preceive movment through time by movement of an object covering distance within a certain frame of time.
When the reality of time is not the movement within a frame, but the movement and counter movement of the present frame of time.

The Past is not a second ago, nor is it billions of years ago. The Past is not what has happened in a (Frame) of time before the (Present) Frame we currently are in. But the past is the sum total of everything that has happened within any present frame of time all at once. all in one frame. In other words Everything that has happened in the past happened at the same time. Even your life growing up up to the point where you read these words. they all happened In the start of time when the big bang happened.

By the time you complete the reading of the words i type the universe in the future time frame has ended all at once, with as much activity of everything that has happened in the past and the present. It give many infinite outcomes resulting in everything that can possibly happen, However, the probility of nothing happining in the future, is impossible even if everything has been done once twice, or an infinite number of times.

Making the present the most infinite possible. Time may move into the future, but the present is always the frame time remains in. Even if A particle is completely destroyed in the present it exsisted in the past, and also in the anti-future. Oh yes the anti-future... Time's Evil twin. think of Anti-Time as time moving in reverse just as Time moves into the future, Anti-Time moves into the past. They are two different forces. Yes Time is a force, The movement of anti-time works to keep everything in possibility to remain in the (Present/anti-Present) Frame of time.

Every Action has an equil and opposing reaction, this does not just apply to movement but to Time as well. And through this results in even more possibilitys in the production of matter, and the destrustion of it also. And who knows the movement of time and anti-time might very well explain the highly active nature of the electron. that funny little massless particle that seems to be everywhere all at once.

Past Present Future and Anti-past, anti-present, anti-future. They are those funny little dimintions of string theory, that when combined make the universe we know and love. Just have fun thinking that Travel through time is possible, becouse it is not going to happen, unless you can break the law of time. or the law of movement. and even if you could. travel back into the past be it 1 sec ago or a million years ago. will result in the same reaction. the present. now. right now in fact. same with the future. you will always end up right back where you started.

On the flipside. oddly enough you can pull from the future into the present, or from the past into the present. but that might not be so plesent to pull from the past. Unless it is from the anti- past you might be ok there. but this is just speculation. I really don't know what the hell i am talking about.

 

[Dmitry67]

Poetry is in another section of this forum I believe.

 

[LoreSpade]

Poetry is in another section of this forum I believe.

sorry, i guess i can't explain things very well :D

I bet you can't prove me wrong.

 

[Dmitry67]

Correct. There is nothing to prove.
Start from putting a list of experimentally verifiable predictions.
Otherwise it is just pure lyrics.

 

[LoreSpade]

Correct. There is nothing to prove.
Start from putting a list of experimentally verifiable predictions.
Otherwise it is just pure lyrics.

Let me work on that and get back to you.

 

[DevilsAvocado]

Poetry is in another section of this forum I believe.

10 points

(Hi Dmitry, I will get back to you on the Schwarzschild solution, but my brain is right now parallel processing the Hubble volume + FTL + N-body simulations, so it’s kinda 'system overload' right now...)

 

[DevilsAvocado]

... Past Present Future and Anti-past, anti-present, anti-future. ...

Italian antipasti is delicious, the rest I don’t know...

I think you’ve been watching Julian Barbour one (anti?)time to many.

https://www.youtube.com/watch?v=<object width="480" height="385"><param name="movie" value="http://www.youtube.com/v/WKsNraFxPwk&hl=en_US&fs=1&rel=0&color1=0x006699&color2=0x54abd6"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/WKsNraFxPwk&hl=en_US&fs=1&rel=0&color1=0x006699&color2=0x54abd6" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed></object>

When Barbour launches his 'drying rack' as a scientific proof of Eternity – every red lamp in my universe starts flashing.

Take an egg and throw it on the wall – In Julian Barbour’s world this egg can now be boiled for breakfast. In most other worlds – you take a new egg for breakfast, instead of waiting for the egg for ∞ time, to reassemble and bounce back into your hand.

At the macroscopic level where we live the second law of thermodynamics guaranties the arrow of time. At the microscopic level there is definitely more freedom for bouncing eggs, but lack of throwers at this level make it hard to discuss... as a breakfast topic...

 

[LoreSpade]

Well i must ask you if time was only in affect to move forward. could that same time move backwards while moving forwards? I don't think something can move forward and backwards in time at the same time. So how is the concept of a different force that governs time moving backwards?

the way i see it. and please forgive me. but Standard forward movement of time affects space, but a backwards movment could affect gravity. We have not found a particle for gravity. and i don't think a particle for space has been found.

If Anti Time did in fact exsist. then it would govern the force of gravity. An example could be.

The amount of movement needed moving forward in time to leave the Earth's gravity, would have to exceed the pull of gravity. And if anti-time does in fact govern gravity then the only way to move faster than anti time is to gradualy increase acceleration until you leave the area where Anti time is in effect. Becouse if you traveled at a constant speed that is not exceeding the natural Anti-time gravity, then Anti time would pull you back down. Law of motion every action has a = and opposite reaction.

So how fast would one have to travel without accelerating to leave the pull of Earth's gravity?

Sorry If This still sounds philosloppycal

 

[DevilsAvocado]

We have not found a particle for gravity. and i don't think a particle for space has been found.

The Graviton is in the http://lhc.web.cern.ch/lhc/News.htm" . Space is not a particle/energy/force – it’s just space.

So how fast would one have to travel without accelerating to leave the pull of Earth's gravity?

9.81 m/s² = at free fall the speed increases by about 9.81 meters per second every second = you must accelerate, or else you go down.


The only reason for time is so that everything doesn't happen at once -- Albert Einstein

 

[Dmitry67]

LoreSpade,
Just FYI

SR and GR strongly suggest the so called Block time, which is the same as Eternalism: http://en.wikipedia.org/wiki/Eternalism_(philosophy_of_time )

I believe most of the physicists believe in Block Time, except the minority, like Smolin. So, first of all, there is no "flow of time", anti-blah blah, pulling to something.

 

[DevilsAvocado]

... I believe most of the physicists believe in Block Time, except the minority, like Smolin. So, first of all, there is no "flow of time", anti-blah blah, pulling to something.

Does Block Time violate the thermodynamic arrow of time and/or the causal arrow of time? If so – what happens if I travel back in Block Time (4-dimensional spacetime) and kill my grandmother when she is 10 years old?

Will I be dead before I travel back to kill grandma, or alive and then die when grandma dies? Or will grandma & I be stone dead all the (block) time?

 

[Dmitry67]

Does Block Time violate the thermodynamic arrow of time and/or the causal arrow of time?

No.
Why do you think so?

The only non-trivial case is closed time curve, in such cases Novikovs self-consistency principle should apply:

http://en.wikipedia.org/wiki/Novikov_self-consistency_principle

 

[DevilsAvocado]

... The only non-trivial case is closed time curve, in such cases Novikovs self-consistency principle should apply ...

Well... I don’t know, but the Novikovs self-consistency principle seems a little too 'magical' in my taste...

"The Novikov Principle does not allow a time traveller to change the past in any way, but it does allow them to affect past events in a way that produces no inconsistencies—for example, a time traveller could rescue people from a disaster, and replace them with realistic corpses seconds before it occurs. Providing that the rescuees do not re-emerge until after the time traveller first journeyed into the past, his/her motivation to create the time machine and travel into the past will be preserved."​

If we apply this on my grandma: I could go back in time, kill my grandma, and just seconds before she dies – I replace here with a 'living copy'!? Where should I get a living copy of my grandma from...?? I’m no magician...!?

And furthermore; suppose someone is filming this event! When I come back to 'today', grandma is dead and that’s ok. But, in the family archive there’s a new film proving that grandma was replaced by a 'magic clone' at the age of 10 – and I myself is responsible for not being the 'real me'??! HELP!

Okay, maybe CTC’s are even more 'magical', so this is really not a big question...

 

[Dmitry67]

Novikov principle tells that for some weird reason you won't be able to kill your grandpa if someone was filming the event so everybody would know that the murder was fake.

 

[Peter Watkins]

Re. #2. If our universe is the result of a collapsing previous universe, then that universe had sufficient gravity to occasion the collapse. If that universe did not come into being in it's expanded form, then it too must have expanded outward. Therefore, collapse of our own universe is inevitable, preceded by slowing, which will cause the galaxies to move apart at an accelerating rate.

 

[DevilsAvocado]

... for some weird reason you won't be able to kill ...

Killing is not my favorite hobby, so this maybe doesn’t matter much...? Anyhow, Novikov principle feels a little like a Brand Unique Stunning Theory (BUST)...

From my local horizon it looks like we have 3 options:

A) Block Time is real and there is absolutely no difference between Past Present & Future in the 4-dimensional spacetime, but time travel is forbidden by the laws of physics.

B) Block Time is real and there is absolutely no difference between Past Present & Future in the 4-dimensional spacetime, and time travel is possible.

C) Block Time is not the whole answer to what time is. We have misunderstood some parts in SR & GR (which also explains why GR <> QM). Time travel is not possible.

My personal favorite is C and then A.

If B is true, it must lead to completely new physics, including mind control on time travelers (I never liked KGB or CIA ). And where is Occam's razor in this case...?

 

[Dmitry67]

Re. #2. If our universe is the result of a collapsing previous universe, then that universe had sufficient gravity to occasion the collapse. If that universe did not come into being in it's expanded form, then it too must have expanded outward. Therefore, collapse of our own universe is inevitable, preceded by slowing, which will cause the galaxies to move apart at an accelerating rate.

No.
You logic is correct for oscillating Universe.
It is not applicable for a single Big Bounce event.

 

[Dmitry67]

In Block Time time travel is just a trajectory in curved spacetime. It is not really a 'travel' in a way it is shown in movies.

 

[DevilsAvocado]

... just a trajectory in curved spacetime ...

You mean like the twin paradox? But what about CTC’s in the Gödel spacetime? And why is Novikov putting this much effort on something like the 'twin paradox'? The twin paradox can never cause a temporal paradox, or can it?

 

[Dmitry67]

CTC is also a trajectory.

 

[DevilsAvocado]

I’m completely lost in space...

Wikipedia - Closed Timelike Curve
"This possibility was first raised by Kurt Gödel in 1949, who discovered a solution to the equations of general relativity (GR) allowing CTCs known as the Gödel metric, and since then other GR solutions containing CTCs have been found, such as the Tipler cylinder and traversable wormholes. If CTCs exist, their existence would seem to imply at least the theoretical possibility of time travel backwards in time, raising the spectre of the grandfather paradox. Some physicists speculate that the CTCs which appear in certain GR solutions might be ruled out by a future theory of quantum gravity which would replace GR, an idea which Stephen Hawking has labeled the chronology protection conjecture."​

 

[Dmitry67]

What I wanted to say, "time travel" in movies is a machine where you chose destination, press big red button, and go there, changing the past.

CTC is timespace formation, so you can make loops there, meeting past or future copies of yourself (it is allowed), but the choice of destination is very limited and the accessible past must be (from the very beginning) a part of CTC

 

[DevilsAvocado]

Okay, but there’s always a theoretical risk of bumping into your "CTC-grandfather", right?

If I understand this correctly, the paradoxical complexity is valid in the case of B?

 

[Dmitry67]

In case B the Novikovs principle should apply.
So if you meet your grandfather then you won't be able to kill him

 

[DevilsAvocado]

I’m with you brother! Back to square one!

"If B is true, it must lead to completely new physics, including mind control on time travelers (I never liked KGB or CIA ). And where is Occam's razor in this case...?"

= Novikovs principle

 

[LoreSpade]

So basicaly physics (on time) currently is in fact based from a philosopy. yet it still rubs special relativity the wrong way?

but i must ask once more.

And i do realize that space is not a force, But i preceive space to be a byproduct or time moving forward. And gravity of time moving backward.

I know it seems odd. but when Einstine said "Time keeps everything from happining all at once." This has some merit.

So i must ask. If time moves forward, and a particle can move its place in space and time. If there was not a negitive Time moving backwards, what would keep that particle from being lost in the future, I am well aware that there is a speed limit and nothing we know of can move faster than light. But if it take X amount of light years for light to travel from a distant galaxy, and we do in fact get a glimpse of the past becouse of this. while the light was en route, it was in the present frame of time even if it was moving forward in time and space. becouse it had to be in the present that is what took it so long to be visable to us.

Sorry for all the typing and reading. but i think it can in a way provide some kinda of reason for the exsistance of the concept of Anti-time.

Becouse without something keeping things from being lost in the future, by in a way what is sent into the future, is shot back out into the present, in a different place in space,

It is a concept i urge you to at least think about. If i am not mistaken at the LHC they indeed saw a particle that seemed to come from the future and was destroyed. upon arrival. That is if i understtod correctly what he was explaining.

But just to add if that is indeed the case, if movement of any particle couses a particle to come from the future, what would happen if for some reason that particle was not destroyed everytime? Would this mean that the universe if finite, yet growing at an infinite rate, but at the same time sometimes the growth is slowed decouse the particle from the future is destroyed. in effect creating more distance between success and failure of the particles to stay?

Furthermore if the past started with just one particle, and it moved into the future to be shot out by an Anti Future, the particle was lost but replaced by 2 new particles move still moving and once not moving. but the forces of two particles, could have made the 2nd particle move in a way repeating the process.