The Paradoxes That Threaten To Tear Modern Cosmology Apart

KentuckyFC writes Revolutions in science often come from the study of seemingly unresolvable paradoxes. So an interesting exercise is to list the paradoxes associated with current ideas in science. One cosmologist has done just that by exploring the paradoxes associated with well-established ideas and observations about the structure and origin of the universe. Perhaps the most dramatic of these paradoxes comes from the idea that the universe must be expanding. What's curious about this expansion is that space, and the vacuum associated with it, must somehow be created in this process. And yet nobody knows how this can occur. What's more, there is an energy associated with any given volume of the universe. If that volume increases, the inescapable conclusion is that the energy must increase as well. So much for conservation of energy. And even the amount of energy associated with the vacuum is a puzzle with different calculations contradicting each other by 120 orders of magnitude. Clearly, anybody who can resolve these problems has a bright future in science but may also end up tearing modern cosmology apart.

Comments

"inescapable conclusion"

[Anonymous Coward]

> What's more, there is an energy associated with any given volume of the universe. If that volume increases, the inescapable conclusion is that the energy must increase as well. So much for conservation of energy.

???
Why cant the energy just be less dense?

Re:"inescapable conclusion"

[Anonymous Coward]

The vacuum seems to have energy, so if space itself expands, the vacuum left has to either not have any energy whatsoever or drain the energy from nearby space. And since the energy of the vacuum seems to be constant, the conclusion is that the expansion is creating vacuum with its own energy

Re:"inescapable conclusion"

[Strangely Familiar]

I think it is because vacuum energy is calculated on the basis of the field theory, which in turn depends on constants like the charge of the electron. I am pretty certain that calculations of the vacuum energy do not depend on the size of the universe. Puzzles like these are really important so that people can think of new questions to ask based on problems they didn't previously realize existed. These puzzles challenge our notions of space and time, which to me, are pretty tenuous notions.

Re:"inescapable conclusion"

[BarbaraHudson]

void that killed the ether theory, explain why there is a limit to the speed of anything and would provide a medium of propagation for the forces without falling back to "magic" fields.

Any sufficiently advanced universe is indistinguishable from magic :-)

Re:"inescapable conclusion"

[Baloroth]

> What's more, there is an energy associated with any given volume of the universe. If that volume increases, the inescapable conclusion is that the energy must increase as well. So much for conservation of energy.

??? Why cant the energy just be less dense?

The FLRW metric (which is what the equation that governs the cosmological expansion of spacetime) has a cosmological constant term in it, initially placed there by Einstein to maintain a steady state universe, but which we now know drives an accelerating expansion of the universe. This constant term is exactly that: a constant (negative) energy per volume of space. More space means more total energy.

However, TFS and TFA (I've only scanned the referenced paper, but that looks much more reasonable) are absolutely wrong about why this is a problem. It is a problem, but only in the sense of figuring out where it comes from (i.e. what exact mechanism drives the creation of this energy). The fact that energy is not conserved violates no law of physics: in fact, general relativity doesn't conserve energy anyways, and the expansion of the universe certainly does not (even without the non-conservative nature of gravity).

See, the conservation of energy is a result of Noether's theorem, which states that for any differentiable symmetry of the action of a physical system, there is a corresponding paired conservation law. For time symmetry, this is the conservation of energy. However, time on the scales of the universe is not symmetric. There was a beginning to the universe (which alone breaks the symmetry: you can't shift backwards in time more than ~13 billion years), and the universe as it is now looks nothing like it did 10 billion years ago. So we don't expect energy to be conserved in the universe as a whole (even if it is on local scales).

Re:"inescapable conclusion"

[Anonymous Coward]

in fact, general relativity doesn't conserve energy anyways,

GR does conserve energy, but in a very messy way with a lot of subtleties that means it gets skipped over in the grad level intro courses. Especially when dealing with an expanding metric, it is possible to formulate a contrived analogy to potential energy.

There was a beginning to the universe (which alone breaks the symmetry: you can't shift backwards in time more than ~13 billion years), and the universe as it is now looks nothing like it did 10 billion years ago.

The beginning of the universe does not need to conserve energy, but things as far as we can tell are conserved after that. The fact that things look different doesn't contradict the type of symmetry needed by Noether's theorem, just as Noether's theorem applies just fine in classical mechanics despite the second law of thermodynamics.

Re:"inescapable conclusion"

[david_thornley]

Pure logic gives us tautologies and nothing more. (They can be very complicated, interesting, and useful tautologies, of course.) Since tautologies hold no matter what the state of the Universe, they can't tell us anything about the state of the Universe.

The idea of synthetic a priori knowledge comes, I think, from geometry and arithmetic. Way back when, these were recognized as pure logic, but they were also believed to be descriptions of reality. There was also metaphysics, which AFAICT was based largely on grammar: if you describe the world with nouns and adjectives, it's natural to think of substances with attributes. Eventually, we figured out that arithmetic and geometry aren't universally applicable in their classical forms. They're still extremely useful in describing reality, but we have to know what parts of reality to describe how. Near black holes, for example, geometry gets really weird, but for many purposes the old Euclidean geometry is adequate.

Sure some theories will change but...

[crioca]

The only thing that's tearing cosmology apart is the gradual expansion of space.

I don't get it

[slashmydots]

If there are no particles moving at all, how does empty space have energy? It's the textbook definition of lack of energy. Empty space cannot impart energy on matter and it can't spontaneously create matter. There's some theory about virtual particles but their net energy is zero when they combine so that's not it. Can anyone explain why empty space has energy?

Re:I don't get it

[smooth wombat]

how does empty space have energy?

That was my question as well until I read Brian Greene's explanation in his book, The Fabric of the Cosmos.

In short, the Higgs Field. Long answer, think of what we call space as a fabric (hence the title of his book). The Higgs Field is the fabric upon which everything else "sits". Even if there are no particles in a given unit of space, it is not empty because the Higgs Field is still there.

Start on page 254 of his book and work your way through as he describes the field and how it (supposedly) permeates everything.

Re:I don't get it

[duke_cheetah2003]

Start on page 254 of his book and work your way through as he describes the field and how it (supposedly) permeates everything.

This just instantly makes me think of "The Force."

Since when did unknown == paradox??

[khchung]

Perhaps the most dramatic of these paradoxes comes from the idea that the universe must be expanding. [...] yet nobody knows how this can occur.

Since when did "paradox" became a synonym for "unknown"?

Yeah, nobody knows how space expands, but how does that make it a "paradox"?

Re:Since when did unknown == paradox??

[Dastardly]

Paradox - "a statement or proposition that, despite sound (or apparently sound) reasoning from acceptable premises, leads to a conclusion that seems senseless, logically unacceptable, or self-contradictory."

The paradox is that energy is supposed to be conserved, but space has energy and is increasing. So, we have a logically unacceptable a conclusion.

Just because it is a current paradox doesn't mean it can never be resolved. We find an energy source, or figure out the laws of physics which in this case allow for the creation of energy and is stops being a paradox.

Quantum physics calculations say the vacuum energy is one value while measurements of the curvature of the universe say it is a different value. That is a paradox especially when both Quantum physics and the physics involved in measuring the curvature of the universe seem to both be right in other respects such that making changes to resolve this paradox causes them to stop describing other things accurately. So, we have logically unacceptable conclusion.

The red shift thing doesn't look like a paradox, but a really cool test of our understanding of cosmological red shift.

And, the homogeneity problem could be a paradox linearity of expansion says the universe is homogenous, observations say it is not. But, they don't mention whether observations have done a reasonable job of determining the dark matter distribution of the universe.

There are paradoxes in the article, but it does drift into one topic that is not a paradox and another that is borderline.

Re:Since when did unknown == paradox??

[Strangely Familiar]

If an unknown paradox fell on top of a tree falling in the woods, but no philosophers could debate the paradox since it was unknown, would it affect whether the tree makes a sound?

Re:Since when did unknown == paradox??

[phantomfive]

Yeah, investigating the paradoxes is one of the most fruitful methods of scientific inquiry and new understanding.

The counterpoint to that is, speculation about paradoxes is one of the most fruitful methods for nutcases and weirdos.

Re:Since when did unknown == paradox??

[david_thornley]

There are things called paradoxes in relativity, which tend to be people thinking in Newtonian terms part of the time.

The twin paradox: Harold stays on Earth, while George (separated at birth) travels at relativistic speeds for a while and then turns around and comes back. Despite the fact that from George's point of view Harold and the Earth went away and came back, George is nevertheless younger. (Harold's using the same frame of reference all the time, being unaccelerated - and we ignore general relativity here, because its effects are minor. George uses two different reference frames, one going out in which Harold is younger, and one coming back where Harold is older, and changes between the two while turning around.)

The pole-in-barn paradox: Fred has a twenty-foot pole, and is running at relativistic speeds towards a ten-foot-wide barn. From the barn observer, Fred's pole shrinks to ten feet, and thus fits into the barn, while Fred sees the barn shrink to five feet wide and his twenty-foot pole can't possibly fit. (Having the pole fit inside the barn means that its front end fits into the barn at the same time the back end does. With Special Relativity, "at the same time" isn't really meaningful, so Fred sees the front end of the pole at the far end of the barn before he sees the back end of the pole at the near end of the barn, while the barn cat sees the timing differently.)

So, paradoxes happen when we're thinking about something in the wrong way. The current problem we've got is that we have two ways of looking at the Universe, both with very large amounts of precisely corroborating evidence, and at least one of those is the wrong way to look at certain things.

Re:"Light drag?"

[Dastardly]

This does happen, although I am not sure if it is seen in red shifts. It is definitely seen in the Cosmic Microwave Background where large cold spots are thought to be due to voids along the line of sight that the CMB photon traveled. I presume a similar effect would apply to any photon crossing that void.

Re:Slashdot, byebye!

[Anonymous Coward]

Yet you continue to visit, click, AND post.On almost every article!

How do you do it?

And you reply to your own post too...

I know the answer, you are a robot, I mean, I am a robot, oh god.... NO CARRIER...

If the universe is a simulation energy is variable

[Paul Fernhout]

http://www.simulation-argument...

But, that does not make it any less real-seeming to all of us being simulated...

And of course, the universe simulator could be simulated, etc....

It might be simulated turtles all the way down. :-)

Re:"Light drag?"

[megahurts.gr]

I am not a physicist myself, but physics is a very interesting topic for me. A long time ago I theorized along these lines, and when I spoke about it with physicists, they told me that my hypothesis has already been considered, and it has a name, and that name is "tired light".

See "tired light" on Wikipedia: https://en.wikipedia.org/wiki/...

Maybe the created "energy" is really entropy

[Burz]

As entropy in the universe increases, so does the amount of space.

Energy is not conserved in General Relativity

[As_I_Please]

It has been known for quite some time that energy is difficult to define rigorously in General Relativity. A good explanation can be found in this post by CalTech physicist Sean Carroll. Key point:

The point is pretty simple: back when you thought energy was conserved, there was a reason why you thought that, namely time-translation invariance. A fancy way of saying “the background on which particles and forces evolve, as well as the dynamical rules governing their motions, are fixed, not changing with time.” But in general relativity that’s simply no longer true. Einstein tells us that space and time are dynamical, and in particular that they can evolve with time. When the space through which particles move is changing, the total energy of those particles is not conserved.

As a simple example, imagine a photon traveling through an expanding universe in a region with no other matter or energy (dark or otherwise). The expansion of space stretches the wavelength of the photon (cosmological redshift, which is distinct from Doppler redshift), causing it to lose energy. The photon loses energy with nothing around it gaining. Energy is lost because spacetime itself is changing, so Noether's theorem doesn't apply.

Re:Energy is not conserved in General Relativity

[Anonymous Coward]

When the photon's wavelength is integrated over the entire, expanding volume, is the energy still non-conserved? Sure, the kinetic energy depends only on the wavelength, but doesn't the photon also have a gravitational field whose source (energy) now occupies more space? Is the associated gravitational energy the integrated deformation of the space-time in which it resides? The deformation density has decreased with decreased kinetic energy density, but the deformation now exists over a larger region of space-time.

Seems... facile

[fyngyrz]

How can we definitively tell if the vacuum over there has the same energy density as the vacuum over here?

Further, how can we tell if the energy we think we find in vacuum here isn't energy that arises from particulate contamination? Or, for that matter (ha) is coming from somewhere else? Has someone managed to (a) create a perfect vacuum and (b) measure its energy and (c) determine that whatever was measured as appearing at X, definitely hadn't disappeared from all the possible Ys? Somehow, I doubt it. If for no other reason than our access to some of the other Y (say, around Andromeda) is... limited. As well as non-contemporaneous -- if something disappeared from that region, to appear here, we wouldn't have any indication it had happened for about 2.5 million years. And even then, our ability to measure vacuum precisely at that distance... not so good.

My (admittedly not very deep) understanding of vacuum is that it is defined by a lack of content, and that a perfect vacuum would be defined by a perfect lack of content -- and were that simplistic idea correct, then I don't see why how much perfect vacuum there is has any bearing at all upon the total amount of energy.

And, if vacuum is indeed empty when perfect, but we think there is energy detected in what we consider a perfect vacuum, then perhaps we're simply misinterpreting the goings-on within an imperfect vacuum. Perhaps there is more to get rid of than the molecules and particles we know of at present.

Or, perhaps space is infinite and at least somewhat plastic to start with, and our situation (going with the idea that the space we can observe seems to be expanding) is more like adding a thimble of water to a planetary ocean (let the ocean conceptually be infinite for the sake of an example.) Perhaps space over there is contracting, while space over here is expanding.

My own position is that any cosmological proposal that includes the phrase "arose from nothing" or similar is probably better filed under astrology until actual evidence is found of the idea -- not possible precursors or echos, but an actual example of what is being described. We seem to be pretty clear on the idea that matter and energy are essentially interchangeable, and we have no experimental data that proves stuff arises from non-stuff, so at least at this point, I see no reason to take an assertion of "arose from nothing" seriously.

Re:Seems... facile

[Anonymous Coward]

How can we definitively tell if the vacuum over there has the same energy density as the vacuum over here?

Measurements of expansion rate from distances and from the CMB closely match models that have a constant energy density per unit volume. That is about as simple as it gets for the moment. Until there is good justification for why we would expect the energy to be different at different places, whether from large scale measurements, or theories about small scale things like QFT, there is no basis to assume things are different. But there is always the possibility things are more complicated than they seem.

Re:Seems... facile

[Anonymous Coward]

There's also no evidence that energy is being created.

This!

Given how quantum non-locality appears to work, we can in some cases be forced to consider that the energy in question is distributed until it becomes "not distributed" by some process that collapse it's superposition. Examination by most physical measurement processes does this.

Even though Einstein abhorred the implications of quantum theory, his own general approach to working out relativistic theory stands, which is to base our examinations of the universe on 2 things:

1- That which we observe and can confirm by experiment and
2- The implications of what we observe and can confirm by experiment which then must be observed and confirmed by experiment.

I do agree that there is a point where each explanation ceases to function to explain the whole, newtonian physics functions to explain how macroscopic objects behave to a certain precision and it breaks down when the curvature of spacetime is altered by extreme amounts of mass in a small place or limited masses being accelerated to such speeds that they require descriptions of how they alter spacetime by effect to be described properly. This description breaks down when we attempt to explain objects existing at the sub atomic level and a whole other set of rules come into play that exist in between the frames of the macroscopic and relativistic linear framework we are used to using to describe things. Beyond this we are at the point where we do not have the tools yet to perform experiments we need to test the implications of the things which we have observed at that level.

Sometimes analogies can be helpful, sometimes they can just confuse the issue. In the case of expanding space, I prefer to think of it as something analogous to plate tectonics, We know the Earth is not expanding, but we know that the floor of the Atlantic ocean is getting wider and wider across geologic time scales, matter is not being created, but the distance between the coastlines of the eastern United States and Western Europe gets a little larger each century. When considering vacuum energy I think of the plate tectonics analogy and remember that even though it seems like the vacuum energy should be becoming more vacant, the implications of what we observe in the Hadron collider confirms that when taken altogether, the total amount of energy in the universe balances out to zero and comparing different sized slices of this pie to one another confuse the issue.

Re:Seems... facile

[fyngyrz]

The energy of the vacuum HERE would be decreasing over time,

You can't assume that everything everywhere behaves the same. You can't assume that energy drawn from one location will show up as a deficit in another (you find running water in the street's gutter... you learn Joe's pool is draining. Assuming Mark's pool is also draining doesn't follow.) You can't measure anywhere but (very) locally, which also means you can only measure data very near temporally -- and so you really have no bloody idea what is going on without resting your conclusion on assumptions made entirely free of supporting data.

What you're claiming is equivalent to saying you know exactly what's going on on a planet orbiting some star in Andromeda because you've done some observations as to what is going on here. Evidence is utterly insufficient to your claim.

Re:Seems... facile

[fyngyrz]

Nah, I just bought one from Dyson. Works great!

Re:Seems... facile

[mattpalmer1086]

IANAP, but my admittedly also very shallow understanding, is that when we're talking about the energy of the "vaccuum", we mean "energy associated with space itself".

A vaccuum is typically defined by the absence of matter in a volume of space (but not necessarily light or other energy). But let's exclude those too - there is no matter or electromagnetic radiation at all.

Even with those exclusions, at a fundamental level space appears to be a seething maelstrom of quantum particles popping in and out of existence. There seems to be some energy associated with "empty" space.

  Some people posit that the vaccuum (i.e. space as we know it) may be "unstable" - that the particular energy it possesses could be lower than it is - and that we're just caught on a local bump in the energy landscape. If the vaccuum ever "fell off" that bump to a lower level, it would apparently spread at the speed of light across the entire universe from wherever it started, destroying everything that currently exists, and leaving behind... I don't know what. More vaccuum, but with a much lower energy associated with it, and with lots of new matter and energy created by the release of the vaccuum energy. Probably.

Anway, happy for a real physicist to correct me on some or all of the above - that's just my very lay understanding of what is meant by vaccuum energy.

Re:Seems... facile

[Methadras]

Well, there are Cassimir effect experiments done in a vacuum that show energy is coming from somewhere. Someplace we can't see. Is it from repository universes that contain the building block materials for this universe that leak through the aether/ether of space? Is that what dark matter/energy really is? Is it's radiation the fundamental particles we see now? I don't know, but what I do know is that it isn't facile.

Re:avogadro's constant and particle density in spa

[iluvcapra]

Even professional physicists like some good numerology sometimes.

Also, just so we're clear, you took a number e-26, multiplied it by a number e+23, and you ended up with a number e+0?

How did this get modded up?

[Anonymous Coward]

I remember something like this vaguely coming up in a comment before on Slashdot, and I hope it was not you making the same mistake, as comments spelled out in those cases clearly that it was a case of density * avogadro's constant / number of atoms gives you the average atomic mass, which is pretty close to 1 for deep space.

so... i went... density = 7 * 10e-26, avogadro's const = 6.023 * 10e23, multiply the two together you get 4.2154. just for fun take the cube-root and oo! you get 1.6153982

No, you multiply those two numbers together, and you get 0.042, which is also a meaningless value because you now have kg/m^3/mol... and it is not like deep space is anywhere near a constant density, as there is a large variation in density and temperature (read about warm intergalactic medium vs. hot intergalactic medium).

I don't know how this got modded up. Not saying it should have been modded down, but you just took two random numbers, one of which doesn't even have that deep of a connection to space as you imply, and multiplied them together incorrectly, and tried to draw vague conclusions from that.

Re:How did this get modded up?

[david_thornley]

A mole is a certain number of particles, not a physical unit in its own right. Multiplying the density times avogadro's constant (assuming you're allowing for molecular weights, which is about 1 gram for a mole of monoatomic hydrogen) is the right way to find the number of particles.

Of course, (a) OP got his or her decimal place screwed up, (b) density does vary widely, and (c) given an arbitrary number, if you try enough ways to manipulate it, you're going to come up with something reasonably close to an interesting number eventually.

I can offer a solution to the cosmology problem

[hAckz0r]

The answer to the cosmological problem can be found in thermodynamics, and the same solution simultaneously removes the need for Dark Matter, Dark Energy, and explains the origin of the vacuum energy. By partially defining the photon in physical terms Gravity becomes simply a emergent property of spacetime given the existence of vacuum energy and it's interaction with the spacetime curvature. In my paper I logically present an argument for the thermodynamics as a conclusion, and present a theory based on first principals. I defer the complete definition and the photon and structure of spacetime/matter for a later paper, so I apologize in advance for trying to keep the paper small enough to be readable.

.
On The Thermodynamics Of General Relativity.
http://vixra.org/abs/1412.0270

I have been looking for constructive feedback on these new ideas, so please do so if you have the time. I published this paper simply to get these new ideas out on the table for discussion by the community while I turn my attention to my next paper on solutions to the paradox of Special Relativity, and later the structure of matter and spacetime. The same solution fits all the open issues I know about.
Thermodynamic Unification Theory https://plus.google.com/u/0/+S...