Big Bang simulated in metamaterial shows time travel is impossible

Apr 13, 2011 by Lisa Zyga report
In the toy Big Bang model, light rays spread out as a function of time, similar to the expansion of spacetime in a diagram of the real Big Bang. Image credit: Smolyaninov and Hung.

(PhysOrg.com) -- By observing the way that light moves inside a metamaterial, researchers have reconstructed how spacetime has expanded since the Big Bang. The results provide a better understanding of why time moves in only one direction, and also suggest that time travel is impossible.

In their study, electrical engineers Igor Smolyaninov and Yu-Ju Hung from the University of Maryland have built a metamaterial by patterning plastic strips on a gold substrate, which they then illuminated with a laser. Because the of electromagnetic spaces (which describe the metamaterial) is similar to the mathematics of (which describe spacetime), the way light moves in the metamaterial is exactly analogous to the path - or “world line” - of a massive particle in (2+1)-dimensional Minkowski spacetime.

As the researchers explained in their study, a Big Bang event occurs in the metamaterial when the pattern of light rays expands relative to the time-like z-dimension. This instance marks the beginning of cosmological time, which moves forward from the Big Bang in the direction of the Universe’s expansion. After the Big Bang event, the light rays expand in a non-perfect way, scattered by random defects in the plastic strips until they reach a high-entropy state. This behavior represents the thermodynamic arrow of time, showing that entropy tends to increase in an isolated system.

The significance of these observations is that the cosmological and the thermodynamic arrows of time coincide, with both of them pointing “forward” (just as we perceive them). While most scientists theorize that the statistical and the cosmological arrows of time are connected in this way, this experiment is one of the few ways in which scientists can “replay the ” and experimentally demonstrate the connection.

The researchers also showed that this novel model of time could provide insight into that involves closed timelike curves (CTCs). CTCs are world lines of particles that form circles so that they return to their starting points.

At first, the researchers thought that, if they could build a metamaterial in which light could move in a circle (and so that its mathematical description were identical to particles moving through spacetime), then they could create CTCs.

But when further analyzing the situation, they found restrictions on how light rays could move in the model. Although certain rays could return to their starting points, they would not perceive the correct timelike dimension. In contrast, rays that do perceive this timelike dimension cannot move in circles. The researchers concluded that Nature seems to resist the creation of CTCs, and that time travel - at least in this model - is impossible.

Explore further: CERN makes public first data of LHC experiments

More information: Igor I. Smolyaninov and Yu-Ju Hung. "Modeling of Time with Metamaterials." arXiv:1104.0561v1 [physics.optics]

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Fausttt
3.5 / 5 (10) Apr 13, 2011
This is flawed simply in the fact that it applies mathematics "similar" to relativity as we currently understand it. Based on observations of how we perceive the universe to behave. So it makes sense that the behavior of this experiment would behave similar to the expansion of the big bang as we currently understand it. It doesn't prove that it describes the actual big bang precisely.
kevinrtrs
1.5 / 5 (40) Apr 13, 2011
Good point. The big bang is just Model. Nothing more. So to create this particular toy and equate it to the big bang is preposterous at the least.
In any case, the big bang has been falsified at so many points that it's farcical but scientist still adhere to it. Simply adjusting the model to fit their new understanding of the real observations into it. Take for instance the totally surprising discovery that there are older looking galaxies at what is supposed to be a much younger time in the start of the big bang. Does that cause them to wonder if the big bang is wrong? No, it's just that these things "happened much earlier than expected". And so it goes on ad-infinitum.
hush1
5 / 5 (16) Apr 13, 2011
All analogies (or "models") are "flawed". Or, if you will, "the map is not the territory". The study's 'conclusion starts and stops with the toy model. No "proof" of anything was sought by the researchers. Science begins where similarity stops.
Bob_Kob
3 / 5 (2) Apr 13, 2011
Expansion of space causing time to move forward. I wonder however how it would feel once space contracts again. How would somebody know that time has reversed directions? What we perceive as reality now might not be the 'proper' direction of time.
Skeptic_Heretic
5 / 5 (17) Apr 13, 2011
Kevin is a turing machine.
Magnette
5 / 5 (9) Apr 13, 2011
Kevins post has been duplicated by the advertising machine...even they're getting in on the act, perhaps hoping that the god of whatever will increase sales for them.
Kingsix
not rated yet Apr 13, 2011
I'm not so certain that the big bang theory has been falsified, however I feel when any theory moves to a point where scientists just accept it without question, it becomes a possible problem for moving forward. Anyway what was said about the toy emulating the model, I would accept that.

Does anyone know a website or something that can accurately and in understandable language explain the scientific explanation of time? My feeble mind is unable to comprehend what I have heard, and I am stuck with what I experience.
Which is of course that time is not something that is simply experienced and is relative to the individual.
CHollman82
4 / 5 (17) Apr 13, 2011
I'm not so certain that the big bang theory has been falsified, however I feel when any theory moves to a point where scientists just accept it without question


Why exactly do you think scientists accept it without question? They accept it currently because they, unlike you, understand the evidence in favor of it, and they question it CONSTANTLY.

Does anyone know a website or something that can accurately and in understandable language explain the scientific explanation of time?


Time is a measurement of change. Things change, ergo time passes. Time is a concept invented by humans, it has no physical referent in reality to studied. All of our units of time are based on observable change... but what if everything slowed down or sped up uniformly? We wouldn't even notice it... Our perception of reality is relative not absolute, and if the rate of change of everything changed equally it would be equivalent to nothing happening at all.
kaasinees
1 / 5 (4) Apr 13, 2011
The articles does not mention quark-gluon plasma so i will consider this experiment incorrect.
Royale
4 / 5 (1) Apr 13, 2011
Well said CHollman82. And Skeptic, I'm glad to see you posting again.
I think it's a little ridiculous to say that time travel is impossible based on anything that can be done in 3-dimensional space. 3D can help you imagine 4D, but you shouldn't use it to model 4D. At least that's the way I see it...
jscroft
3.8 / 5 (6) Apr 13, 2011
@kaasinees: This experiment is not "incorrect". NO experiment is incorrect, as an experiment measures PRECISELY what it measures... nothing more, nothing less. If there is an error, it is perhaps in our PRECISION in making the actual experiment conform to the experimental protocol, and our EXPECTATIONS regarding any isomorphism between the experimental protocol and something else in the Universe.

While this experiment doesn't definitively prove anything--which is awfully rare anyway--it DOES (probably) somewhat constrain the mathematical space within which an answer to the CTC question might be found. How much does the experiment constrain this space? Why, pretty much exactly to the degree with which the relevant dynamics of the experimental medium conform to those of the nascent Universe.

In other words, nobody knows EXACTLY how much, but probably some. More analysis will tighten that up a bit.
CHollman82
1 / 5 (2) Apr 13, 2011
Thanks Royal.

Consider this... assuming a "time" is defined solely by the state of existence at that time then to travel back in time requires nothing more than saving some state of reality and then later restoring that state.

Of course you cannot save a state of the entire universe... so you cannot truly travel back in time using this method, but if you were to do so for an isolated system, such as this solar system, then the effect would be roughly equivalent.

Say I develop some technology that can instantly gather the data of the entire solar system, right down to every last fundamental unit of matter/energy, and record that data in some manner. I could store complete "snapshots" of the solar system. Say I also had the ability to instantly modify the state of the solar system to match one of those snapshots... would that not be roughly equivalent to traveling back in time? Of course the person performing this must be outside of the system being modified...
DavidMcC
not rated yet Apr 13, 2011
As I described in another thread, I think the BB model is not so much wrong as incomplete. The loop quantum gravity hypotheses of Ashtekar and Smolin can, in the versions that do not discard the hyperspace continuum, provide a good framework for demistifying otherwise strange results, such as inflation and dark energy (that otherwise requires a temporally-and spatially dependent cosmological "constant"), and dark matter (that otherwise requires still undiscovered particles like WHIMPS or MACHOS!).
This is the earlier thread:
http://www.physor...ans.html
Dynamicp
1 / 5 (3) Apr 13, 2011
We are trying to understand what constraints and forces act upon the Nature of Time/Space (TS). There are many experiments with each cutting a miniscule of understanding TS. It is too vast of a Notion for "WE" humans to grasp. We are stuck thinking with a Tunnel vision approach, disregarding all factors of the TS. "quark-gluon plasma", Dark Matter, M-Theory, String Theory, 3D-4D-5D, Gravitational forces, theory of Relativity, CTC..and such. It was an attempt to move closer to TS distortion loophole. We can only make assumption and experiment ..and yes with "TOYS" Keep up the experiments..it will one day surface!
Skeptic_Heretic
5 / 5 (9) Apr 13, 2011
We are trying to understand what constraints and forces act upon the Nature of Time/Space (TS). There are many experiments with each cutting a miniscule of understanding TS. It is too vast of a Notion for "WE" humans to grasp
If everyone thought the way you do we'd be naked in the jungle picking berries and struggling to find clean water.
El_Nose
not rated yet Apr 13, 2011
Hey guys i have a QUESTION...

Is is possible to move faster than the expansion rate of the universe?

The universe ( to me this means space ) is expanding at a rate or at an accelerating rate, can a particle or energy or information move faster than this rate and how close is this rate to c ( speed of light) ??

If you decide to tackle this question please send me a PM with either your answer or a PM telling me you posted an answer in the comments.

~Thanks in advance
axemaster
5 / 5 (1) Apr 13, 2011
Time is a measurement of change. Things change, ergo time passes. Time is a concept invented by humans, it has no physical referent in reality to studied. All of our units of time are based on observable change... but what if everything slowed down or sped up uniformly? We wouldn't even notice it... Our perception of reality is relative not absolute, and if the rate of change of everything changed equally it would be equivalent to nothing happening at all.

Sure, but then you have to say that space is also a meaningless "human" invention for exactly the same reasons. Either way, you are making an entirely pointless statement.

Space and time are coordinate systems used by mathematicians and physicists to describe physical systems. Calling them "human inventions" is pointless, because scientists don't think of them in your terms to begin with (at least not competent scientists).
Tuxford
1.8 / 5 (17) Apr 13, 2011
The universe is not expanding. It is the interpretation of the red-shift as cosmological distances that is wrong. High red-shift quasars have been found in nearby galaxies. No galactic rotation has ever been directly measured, other than interpreting red-shift. Standard candle explosions may not be so standard afterall. The Big Bang is a math model gone wild.
Skeptic_Heretic
4 / 5 (12) Apr 13, 2011
The universe is not expanding.
Not this again...
It is the interpretation of the red-shift as cosmological distances that is wrong. High red-shift quasars have been found in nearby galaxies.
Tuxford. Red-shift is the delta in frequency between measurements over a period of time. red-shift is a measure of speed. A fast moving object very close to us would exhibit a greater delta red-shift than an exact copy of that object moving away at a slower speed. That object's total shift in frequency will be less, but the delta in the shift will be higher. Using delta red-shift one can determine distance based on the matter content of an object for comparison against a non-moving object.

This may be why each paper on stellar distance appears to confuse you.
Moebius
1.9 / 5 (9) Apr 13, 2011
As I've said before and received low marks for:
Time travel is impossible. Physics understanding of time leaves much to be desired and is probably wrong. Now is simultaneous everywhere, and there is only now. The passage of time is purely perceptual and relative, measured by benchmarks. Ours are the speed of chemical reactions and any changes we perceive in the passage of time anywhere is just a change in the speed of our benchmarks, not a change in time.

This article shows that physics is starting to learn a bit about time.
CHollman82
2.8 / 5 (4) Apr 13, 2011
Sure, but then you have to say that space is also a meaningless "human" invention for exactly the same reasons.


Agreed, if you define "space" as "empty space" and "empty space" as nothing... then yes space is nothing.

Either way, you are making an entirely pointless statement ... Calling them "human inventions" is pointless, because scientists don't think of them in your terms to begin with (at least not competent scientists).


It's not pointless if my statements lead more people to consider these things in the way scientists do, as you are describing, rather than as physical things that actually exist to be discovered...
gwrede
3.7 / 5 (3) Apr 13, 2011
The title says
Big Bang simulated in metamaterial shows time travel is impossible
and the ingress says
The results provide a better understanding of why time moves in only one direction, and also suggest that time travel is impossible.
If the editors had a university degree, they'd never even think about mixing up "shows" and "suggests".

I am disappointed.
Tuxford
1.6 / 5 (16) Apr 13, 2011
Red-shift frequency difference is assumed to represent speed-differential at galactic distances. It has not been confirmed (at these distances), saved for assumed standard candles. It has ONLY been confirmed (largely) at stellar distances. The Pioneer Anomaly is a symptom of these assumptions. Do some homework, Skeptic.
Skeptic_Heretic
4.1 / 5 (14) Apr 13, 2011
Red-shift frequency difference is assumed to represent speed-differential at galactic distances.
No, it is a well understood quality of electromagnetic emission. It has been measured and quantified on all scales except for the very small. One can infer that over galactic distances, without the 'assumption' of a material unknown to science (aether) that the mechanic would apply equally. Since your'e an aether hypothesist (read: wack job), it is assumed that you would disregard the facts in favor of your own aether hypothesis 9read: nonsense).
The Pioneer Anomaly is a symptom of these assumptions.
The Pioneer anomaly was the result of heat radiation and solar partial pressure.
Do some homework, Skeptic.
Did enough for the both of us, unfortunately I'm the only one who demonstrably benefitted from such work.
Tuxford
1.4 / 5 (18) Apr 13, 2011
Careful Skeptic. Your mental illness is showing. Like to 'Assume' you have it all figured out, eh. Egomania is a worldwide disease.
PS3
1.8 / 5 (10) Apr 13, 2011
wormhole will be the key to time travel.
Skeptic_Heretic
4.3 / 5 (13) Apr 13, 2011
Careful Skeptic. Your mental illness is showing. Like to 'Assume' you have it all figured out, eh. Egomania is a worldwide disease.

I'm not the one who said:
The universe is not expanding. It is the interpretation of the red-shift as cosmological distances that is wrong.
Then went on to denegrate mathematicians and scientists of all stripes.
Like to 'Assume' you have it all figured out, eh.
I prefer to assume than to state unequivocally.
Norezar
4 / 5 (3) Apr 13, 2011
I'm not sure I can picture how shining a laser pointer at a glorified piece of tinfoil accomplishes anything, let alone disapproves something we know and can prove very little about.
Kingsix
3.7 / 5 (3) Apr 13, 2011
side thought here. We hav all heard of alternate dimensions in theories. So I propose that if it is possible to move from one dimension (reality) to another, then there should be an alternate dimension available which happens to be ahead or behind in (our perceived) time. Of course that relies on alternate dimensions and the possibility of moving from one to another, and of course you could not change the other dimension based on your actions. However you also would have none of the problems with killing your ancestors etc.
CHollman82
4 / 5 (8) Apr 13, 2011
wormhole will be the key to time travel.


Hey I watch star trek too!
ekim
not rated yet Apr 13, 2011
The mathematics of general relativity is only half the equation as we currently understand it. Quantum physics, being the other half, may alter our understanding of the results of this experiment.
Transudationist
1.5 / 5 (12) Apr 13, 2011
Why is it assumed that the Big Bang was an event analogous to an "explosion"?

It is respectfully submitted that the Big Bang was not an unguided expansion of space-time matter-energy (i.e., it was not an event analogous to a bomb exploding); rather, it was an ordered ex­pansion of space-time matter-energy (i.e., it was an event analogous to a seed sprouting): therefore, it did not explode it sprouted. As to who or what planted it, there is no way to know. Nevertheless, Aristotles notion of the unmoved Mover (or God, if you prefer) is a sound hypothesis. Therefore, adherence to a theistic-spiritualistic-teleological paradigm is just as, if not more, sound than is adherence to an atheistic-materialistic-evolutionist paradigm; note please the use of the term evolutionist: evolution of course is true, scientific, and undeniable. Evolutionism, on the other hand, is the philosophy of nihilism: evolutionism is nothing more than atheist metaphysics.
soulman
4.4 / 5 (9) Apr 14, 2011
Why is it assumed that the Big Bang was an event analogous to an "explosion"?

It isn't. Certainly not by anyone who has even basic knowledge of cosmology.

It is respectfully submitted that the Big Bang was not an unguided expansion of space-time matter-energy (i.e., it was not an event analogous to a bomb exploding)

Yes, sure, but no one is arguing that, so why are you trying to dispel it?

it was an ordered ex­pansion of space-time matter-energy (i.e., it was an event analogous to a seed sprouting): therefore, it did not explode it sprouted.

Ugh, the universe SPROUTED into existence? LOL that's the first time I heard that one. I think I prefer the explosion straw-man.

As to who or what planted it, there is no way to know.

Then how do you know someone planted it?

Nevertheless, Aristotles notion of the unmoved Mover (or God, if you prefer) is a sound hypothesis.

Sure, if you're a nutjob.

more...
soulman
4.3 / 5 (12) Apr 14, 2011
Therefore, adherence to a theistic-spiritualistic-teleological paradigm is just as, if not more, sound than is adherence to an atheistic-materialistic-evolutionist paradigm

Off with the fairies...

Evolutionism, on the other hand, is the philosophy of nihilism:

No such thing as evolutionISM, just plain, simple evolution. And it isn't a philosophy, but observable fact. Also, it's the opposite to nihilism, as it's the mechanism through which life perpetuates.

evolutionism is nothing more than atheist metaphysics.

As opposed to an invisible gardener shitting out seed universes? You gonna troll some more?
soulman
5 / 5 (4) Apr 14, 2011
Is is possible to move faster than the expansion rate of the universe?

Nothing with mass can move faster than light in a vacuum.

The universe (to me this means space) is expanding at a rate or at an accelerating rate, can a particle or energy or information move faster than this rate and how close is this rate to c?

Again, no. The max speed of information is c and nothing with mass can exceed this.

Expansion is a tricky thing. It's defined as the increase of distance between distant objects with the passage of time. This does not mean that distant objects themselves are moving THROUGH space at ever increasing rates.

Distant galaxies and galaxy clusters have relatively low peculiar motions through space. It's just that more space is being created between objects, which becomes cumulative the farther out you go, and so it APPEARS that the galaxies are traveling at c or above at the observable edge of the universe.
unknownorgin
1 / 5 (1) Apr 14, 2011
Time travel is a question of can matter survive outside of the event horizon or are there multiple event horizons? When an object is moving near the speed of light time slows down for it but to a stationary observer the object is still in the event horizon because it can still be observed.
frajo
5 / 5 (6) Apr 14, 2011
Since your'e an aether hypothesist (read: wack job), it is assumed that you would disregard the facts in favor of your own aether hypothesis 9read: nonsense).
I think Tuxford is from the "Electric Universe" faction.
Rodrigo_Castro
not rated yet Apr 14, 2011
At speed of light time stops and whatever light is moving with respect to, lives it's whole lifecycle so fast it is just an unnoticible flash for it to reach maximun entropy. Light never goes old...it fills up the universe..."we" (the "material" universe light travels with respect to) are just quick fizzes maybe provoqued by light itself ramdomly in the universe of universes. Light is "god". It has always been there.(I am an atheist, please don't missunderstand me)
CHollman82
3.9 / 5 (7) Apr 14, 2011
it was an ordered ex­pansion of space-time matter-energy (i.e., it was an event analogous to a seed sprouting): therefore, it did not explode it sprouted.


The only difference between an explosion and a seed sprouting is the energy and time involved... if you compressed the time it took for a seed to sprout down to 1/10,000th of a second it would look very much like an explostion. Both follow the laws of physics.

Aristotles notion of the unmoved Mover (or God, if you prefer) is a sound hypothesis.


There is no such thing as an unsound hypothesis...

Therefore, adherence to a theistic-spiritualistic-teleological paradigm is just as, if not more, sound than is adherence to an atheistic-materialistic-evolutionist paradigm


Not even close... A hypothesis is a proposed idea to explain observed phenomena. An idea merely being called a hypothesis says NOTHING about how likely that idea is to being accurate. Theories are what you should be concerned with, not hypotheses.
CHollman82
3 / 5 (4) Apr 14, 2011
it was an ordered expansion of space-time matter-energy (i.e., it was an event analogous to a seed sprouting): therefore, it did not explode it sprouted.


The only difference between an explosion and a seed sprouting is the energy and time involved... if you compressed the time it took for a seed to sprout down to 1/10,000th of a second it would look very much like an explostion. Both follow the laws of physics.

Aristotles notion of the unmoved Mover (or God, if you prefer) is a sound hypothesis.


There is no such thing as an unsound hypothesis...

Therefore, adherence to a theistic-spiritualistic-teleological paradigm is just as, if not more, sound than is adherence to an atheistic-materialistic-evolutionist paradigm


Not even close... A hypothesis is a proposed idea to explain observed phenomena. An idea merely being called a hypothesis says NOTHING about how likely that idea is to being accurate. Theories are what you should be concerned with, not hypotheses.
CHollman82
3.4 / 5 (5) Apr 14, 2011
I'm sorry, I must correct myself. In my haste I wrote that there is no such thing as an unsound hypothesis. I wrote this because a hypothesis is merely an idea, it does not have to stand up to any scientific scrutiny to be a hypothesis nor does a hypothesis give any indication as to the likelihood of the idea being correct.

I forgot one thing though, a scientific hypothesis must be able to be tested and falsified.

Therefore I was wrong, and the notion of the "unmoved mover" or "God" that you mentioned is indeed invalid. You cannot falsify the existence of a being described to be omnipotent.
frajo
5 / 5 (5) Apr 14, 2011
I forgot one thing though, a scientific hypothesis must be able to be tested and falsified.

Therefore I was wrong
No, you were right, there is no unsound hypothesis. The notion of an "unmoved mover" is not an unsound hypothesis. Instead it is no hypothesis at all; it's speculation.
Justin_Calkins
not rated yet Apr 14, 2011

Again, no. The max speed of information is c and nothing with mass can exceed this.


Quantum effects have shown information that as exceeded C. Quantum entanglement is 1 example.

Also the guy you were quoting asked if you can travel faster than the expanding of the universe not faster then speed of light
CHollman82
3.4 / 5 (5) Apr 14, 2011
Quantum effects have shown information that as exceeded C. Quantum entanglement is 1 example.


No it is not.

Also the guy you were quoting asked if you can travel faster than the expanding of the universe not faster then speed of light


Yes, and the expansion of the universe must have been faster than the speed of light, if it never was how do you reconcile the observations of stars that are billions of light years away with the big bang theory?
soulman
5 / 5 (4) Apr 14, 2011
Quantum effects have shown information that as exceeded C. Quantum entanglement is 1 example.

That is incorrect. No information can be transmitted by quantum entanglement or teleportation. To send actual information, you always need a data channel at or slower than c.
cisb
not rated yet Apr 15, 2011
I know one of you smart guys can answer this:

If all matter in the big bang is moving outward
and logicaly we are not the last bit of matter in
the big bang.
That would mean there is matter behind us, following us.
when we look in this direction,
would matter appear to be standing still or gaining on us?
Why have I never heard about this from any of you?

soulman
5 / 5 (5) Apr 15, 2011
If all matter in the big bang is moving outward and logicaly we are not the last bit of matter in the big bang. That would mean there is matter behind us, following us.

I doesn't work like that. The BB wasn't an explosion at a point in space out of which matter and energy were flung. You cannot think of it in terms of thrown projectiles.

The BB marked the creation of space-time and it happened everywhere. Matter only came on the scene afterward when the universe had cooled enough and various phase transitions occurred to enable matter to form and ultimately coalesce into stars and galaxies.

when we look in this direction, would matter appear to be standing still or gaining on us?

There is no preferred direction to look in. The universe has no center.

Why have I never heard about this from any of you?

Probably because your understanding of the BB is incorrect. There are plenty of good references on the net. Start with google and wikipedia.
DavidMcC
not rated yet Apr 15, 2011
Soulman is correct in terms of the space we exist in and measure. However, the loop quantum gravity-based black-hole cosmology (which makes some kind of sense of all the strange phenomena in cosmology, such as dark matter and even inflation, and gives a new perspective on dark energy, as being the effect of a black hole, feeding from its "mother"), postulates a 4-D space-like hyperspace continuum which supports finite but unbounded, quantized spaces such as ours. In this "hyper-space", which has zero energy density of its own, a universe does have a centre and an edge.
frajo
5 / 5 (1) Apr 15, 2011
Soulman is correct in terms of the space we exist in and measure. However, the loop quantum gravity-based black-hole cosmology (which makes some kind of sense of all the strange phenomena in cosmology, such as dark matter and even inflation, and gives a new perspective on dark energy, as being the effect of a black hole, feeding from its "mother"), postulates a 4-D space-like hyperspace continuum which supports finite but unbounded, quantized spaces such as ours. In this "hyper-space", which has zero energy density of its own, a universe does have a centre and an edge.
When talking about alternative, as yet non-falsifiable cosmology models I'd like to mention the Ekpyrotic/Cyclic model of Steinhardt and Turok which is the most beautiful as it does away with the mind-twisting concepts of a "beginning of space and time" (no need of a creation singularity), of inflation, and of Dark Matter while being compatibel with all observational data.
DavidMcC
1 / 5 (1) Apr 15, 2011
Frajo, I'm glad you accept that the Ekpyrotic model is non-falsifiable, unless you want to wait for billions of years. The BH-based LQG cosmology at least has the advantage that it allows for an extension of such principles of physics as conservation of total energy to the multiverse, avoiding the embarassment of the "breakdown of physics in black holes, and the non-sensical mathematical singularity" of classical black holes. The problem is how to show that complete gravitational collapse is mearely converting gravitational energy into new space, when we can only see the contents of the new space with gravity, and not also light. To me, LQC just seems to require less of a leap of faith than other cosmologies, especially brane cosmologies.
DavidMcC
not rated yet Apr 15, 2011
Also, although LQC implies that our own universe had a beginning ("big bang", or more properly, common-or-garden, dirty LITTLE bang, as I prefer to call it), it does not imply that the multiverse itself did, because a zero-energy-density hyperspace does not need its own big bang.
soulman
5 / 5 (1) Apr 15, 2011
However, the loop quantum gravity-based black-hole cosmology (which makes some kind of sense of all the strange phenomena in cosmology, such as dark matter and even inflation, and gives a new perspective on dark energy, as being the effect of a black hole, feeding from its "mother")

I was unaware that LQG was based on 'black-hole cosmology' or that it explained inflation and dark matter. Can you provide a link to a reference where this is explained?
frajo
5 / 5 (2) Apr 15, 2011
Frajo, I'm glad you accept that the Ekpyrotic model is non-falsifiable, unless you want to wait for billions of years.
That's not right; I wrote "as yet non-falsifiable".
In fact, Ekpyrosis makes predictions about certain patterns in the WMAP which will be measurable in the current century. LQG has nothing comparable to offer, AFAIK.
DavidMcC
not rated yet Apr 15, 2011
Soulman, I didn't say that LQG was based on BH cosmology, quite the other way around.
DavidMcC
not rated yet Apr 15, 2011
Frajo, I missed the chance to predict the failure of GR to explain accelerated expansion of the universe correctly (ie, without a spatio-temporarily varying cosmological "constant"). If you like, LQC could have predicted the effect called quintessence, as our universe feeding from its mother universe. Of course, this is only a philosophical point, because there is no way of measuring how much "food" (ie matter in the mother universe) is (or rather, WAS at the time represented by the observation of distant galaxies) available.
However, I prefer a philosophy that doesn't require arbitrary bolt-ons for every strange phenomenon discovered by astronomers.
Interestingly, LQG wasn't actually proposed to explain a multiverse (only to unify quantum theory with gravity), and yet it does, without any strange add-ons, because it included the concept of "linked loops" (ones between which an excitation - ie, particle - can move) from the start, and , by implication, unlinked ones as well.
6_6
1 / 5 (3) Apr 15, 2011
this random scattering of matter idea is hogtossle. All the variables are too perfect to be a cosmic accident. the universe, including our planet, Earth, was in existence for an indefinite time before creation began. astronomers calculate that the universe may be as much as 15 billion years old. why is that not hard to believe and other more obvious answers staring you in the face?
DavidMcC
not rated yet Apr 15, 2011
Eh? You contradict yourself at least twice, 6_6. And who is "you"?
Certainly, the universal constants seem to be the product of lots of universes, so that at least one gets them right to support complex biochemistry, but it is absurd then to refer to the 4bn-ish years that earth has existed as "an indefinite time before creation began", ie "as much as 15bn years".
BTW, creation in this sense means when our universe began, not when any other one did.
DavidMcC
not rated yet Apr 15, 2011
Oh, I see! You (6_6) are railing against an imaginary creationist, I suspect. So, you define creation as circa 6000 years ago, right?
Nobody was talking about that, 6.
Qnoiz
5 / 5 (1) Apr 15, 2011

Yes, and the expansion of the universe must have been faster than the speed of light, if it never was how do you reconcile the observations of stars that are billions of light years away with the big bang theory?


When talking about the distance of a moving object, we mean the spatial separation NOW, with the positions of both objects specified at the current time. In an expanding Universe this distance NOW is larger than the speed of light times the light travel time due to the increase of separations between objects as the Universe expands. This is not due to any change in the units of space and time, but just caused by things being farther apart now than they used to be.

What is the distance NOW to the most distant thing we can see? Let's take the age of the Universe to be 14 billion years. In that time light travels 14 billion light years, and some people stop here. But the distance has grown since the light traveled.
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Qnoiz
5 / 5 (1) Apr 15, 2011
The average time when the light was traveling was 7 billion years ago. For the critical density case, the scale factor for the Universe goes like the 2/3 power of the time since the Big Bang, so the Universe has grown by a factor of 22/3 = 1.59 since the midpoint of the light's trip. But the size of the Universe changes continuously, so we should divide the light's trip into short intervals. First take two intervals: 7 billion years at an average time 10.5 billion years after the Big Bang, which gives 7 billion light years that have grown by a factor of 1/(0.75)2/3 = 1.21, plus another 7 billion light years at an average time 3.5 billion years after the Big Bang, which has grown by a factor of 42/3 = 2.52. Thus with 1 interval we got 1.59*14 = 22.3 billion light years, while with two intervals we get 7*(1.21+2.52) = 26.1 billion light years. With 8192 intervals we get 41 billion light years. In the limit of very many time intervals we get 42 billion light years.
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Qnoiz
5 / 5 (1) Apr 15, 2011
Another way of seeing this is to consider a photon and a galaxy 42 billion light years away from us now, 14 billion years after the Big Bang. The distance of this photon satisfies D = 3ct. If we wait for 0.1 billion years, the Universe will grow by a factor of (14.1/14)2/3 = 1.0048, so the galaxy will be 1.0048*42 = 42.2 billion light years away. But the light will have traveled 0.1 billion light years further than the galaxy because it moves at the speed of light relative to the matter in its vicinity and will thus be at D = 42.3 billion light years, so D = 3ct is still satisfied.

If the Universe does not have the critical density then the distance is different, and for the low densities that are more likely the distance NOW to the most distant object we can see is bigger than 3 times the speed of light times the age of the Universe. The current best fit model which has an accelerating expansion gives a maximum distance we can see of 47 billion light years.
Rameses_ii
not rated yet Apr 15, 2011
Time travel is not possible; at least not in the traditional line of thinking. The finite matter in the known universe would have to exist in parallel in two different states. New matter cannot be created but only rearranged. So, for example, to go back to 1947 one would have to create a device that would reconfigure all matter in the known universe to be a previous version of how it was configured in 1947. You could consider this time travel I guess, but our present would cease to exist and be replaced with our past. But then wouldn't we be in an endless loop forever? I suppose you could localize the time travel to a specific area, say Earth. However, before you could revert matter back to a previous state exactly wouldn't you have to have some sort of backup to restore from?
Skeptic_Heretic
3.7 / 5 (3) Apr 16, 2011
I always enjoy watching people make absolute statements about unknowable outcomes without a shred of evidence without explicitly stating that it is an opinion.
Raygunner
not rated yet Apr 16, 2011
No time - only a "now". Time is a human illusion caused by memories of the past, imagining the future, clocks, schedules, daily habits, circadian rhythms, day/night cycles, etc etc. What we see are changes in the now - nothing more. Drop space/time and replace with space/inertia or space/inertial-mass-energy (or something that ties mass movement/velocity and its energy changes through space - but I'm way out of my knowledge area here) and I bet the grand unified theories start to work. I am convinced there is no time and human time models can't force it down the universe' throat. I'm a layman when it comes to this but a "now" seems or feels - truthful - for lack of a better word. Strip away all of the illusions and it just makes more sense.
Bitflux
1 / 5 (1) Apr 16, 2011
Your perception tells you what is an illusion and what is not - the question is, can you trust your mind? How can we establish a shared understanding when we dont share the same perception of things? How can anyone judge if timetravel is possible - with this extremely narrow perception of the universe?
TheGhostofOtto1923
1 / 5 (1) Apr 16, 2011
Your perception tells you what is an illusion and what is not - the question is, can you trust your mind? How can we establish a shared understanding when we dont share the same perception of things? How can anyone judge if timetravel is possible - with this extremely narrow perception of the universe?
If you jump off a building your personal 'perception' -cognition that is- might tell you you're flying. Until you hit the ground that is. Does that make any sense to you?

(Cue Kick-ass trailer)
Bitflux
not rated yet Apr 16, 2011
How do you know if you even feel, that you hit the ground? Your sensory system is crushed on impact and cannot relay the information to the brain which is also being crushed at the moment
The last info your mind will recieve is "im flying", nothing else will ever reach your consciousness - say what if you survived, but all sensory input was cut off due to damage, then you would still be flying, but in a dark silent universe, how would time feel like there?
DJ101
not rated yet Apr 17, 2011
How can they argue that "time travel is impossible" when it happens every day? The clocks on certain satellites in space, due to speed, are recalibrated because they "travel in time." One of the cosmonauts (Sergei Krikalev?) is considered a "time traveler" because he flew around the earth for many years at a high rate of speed, which made his age younger by micro-seconds.

Are these "physicists" aware of Einstein's work? Are they aware of the relationship between time and velocity?

I'm not even a physicist and I know that these guys are off!
beelize54
1 / 5 (1) Apr 17, 2011
I'm not even a physicist and I know that these guys are off!
Of course, you're right - the problem is in definition of the time-travel concept. The problem with time definition by people is, they're taking it in implicit, self-referencing way. If some process appears reversed in time, the people are not flapping - but they're grumbling, instead: "Hey, this process reversal still occurs in normal time - so what? Show us some real time machine!"

If I would arrange some better experiment devotedly, showing them a hologram of their grandfather, they could always say: "But this... and that distant star in Hubble deep field is still rotating in its original direction during your demonstration. This is not, what the traveling in time is supposed to be - you're just cheating us, again! Go to the hell with your silly party tricks! We want our money back!" Actually it's not so difficult to violate time arrow locally, especially if we define it with entropic time arrow.
beelize54
1 / 5 (1) Apr 17, 2011
Many processes (including the life formation) are of negentropic nature. I can remove the heat from the gas in the refrigerator - which is what the gases never do spontaneously - under dispersal of much larger amount of heat into atmosphere at the price. Is this local time arrow violation or not? Where is the exact criterion of actual time travel during such an experiments, after then? You can always say, some artificial arrangement of experiment, leading into local entropy arrow violation is in fact a quite natural consequence of spontaneous entropy increasing during preparation of experiment - it's just the question of the definition of scope of "isolated system".

The memo is, here is as many local time arrows, as many local space-times (a various density gradient of material environment). Some of them are much larger, than the others - but they're still many of them. It's not possible to determine, what the absolutely global, universal time means.
TheGhostofOtto1923
1 / 5 (1) Apr 17, 2011
The last info your mind will recieve is "im flying", nothing else will ever reach your consciousness -
No, probably on the way down your cognitive disconnect would have cleared and you might wish you hadnt jumped off that building.
say what if you survived, but all sensory input was cut off due to damage, then you would still be flying, but in a dark silent universe, how would time feel like there?
No, you would still be regretting your decision to jump off the building. Or you would be completely insane. Just a guess. Sensory deprivation has been studied. People do not like it.
http://www.youtub...a_player
skitterlad
not rated yet Apr 18, 2011
Interesting, I've come to the same conclusion by doing the calculations in my head using abstract thought and deductive reasoning with proven physics as a reference.

That's how they did it in the old days (Ancient Greeks).
shams
1 / 5 (1) Apr 20, 2011
really interesting, and i agree.I am not a qualified physicist but do have a bit of knowledge to say that, we can actually travel to a point in space in a different time-past or future,we will not be travelling in time but through the space time fabric, gravity is the key.That time is relative though to the time in hyperspace, which is stretched by the mass of the planet.

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