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If the expansion of the universe is due to dark energy and the expansion is faster than the speed of light, does that imply that the expansion of the universe is infinite? Space is created as the universe expands – but does dark energy increase in the expansion? Are there any “brakes” in the process or does it just go on ad infinitum?

How much faster than the speed of light does dark energy move? Does it vary from place to place or is it uniform?

originally posted by: Phantom423
If the expansion of the universe is due to dark energy and the expansion is faster than the speed of light, does that imply that the expansion of the universe is infinite?

Not necessarily. Flatness measurements do more to imply an infinite universe but they aren't conclusive. The universe could be finite or infinite.

Space is created as the universe expands – but does dark energy increase in the expansion? Are there any “brakes” in the process or does it just go on ad infinitum?

We don't know enough about dark energy to say conclusively. If the zero energy hypothesis of the universe is correct, the increases in dark energy may be offset by the increasing distances between masses, which according to Alan Guth is a form of negative energy.

Zero-energy universe

A generic property of inflation is the balancing of the negative gravitational energy, within the inflating region, with the positive energy of the inflaton field to yield a post-inflationary universe with negligible or zero energy density.[5][6] It is this balancing of the total universal energy budget that enables the open-ended growth possible with inflation; during inflation, energy flows from the gravitational field (or geometry) to the inflaton field—the total gravitational energy decreases (i.e. becomes more negative) and the total inflaton energy increases (becomes more positive). But the respective energy densities remain constant and opposite since the region is inflating. Consequently, inflation explains the otherwise curious cancellation of matter and gravitational energy on cosmological scales, which is consistent with astronomical observations.

How much faster than the speed of light does dark energy move? Does it vary from place to place or is it uniform?

I don't think of dark energy as moving, and really I don't even think of the galaxies as "moving" due to inflation, rather, space is expanding. This is my favorite paper on superluminal expansion:

Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe

The recession velocity of all galaxies with z>∼ 1.5 exceeds the speed of light in all viable cosmological models

If you plot where z=1.5 that's roughly a sphere, and generally inside that the recessional velocities will be less than c, outside that recessional velocities will tend to be larger than c, though there may be exceptions due to local motions unrelated to inflation. The further away the greater the recessional velocity, and at larger distances the relationship becomes non-linear. For redshift of z=10 it looks like the average recessional velocity was something like 2.5 times the speed of light, where ~13 billion year old light from galaxies represents a current distance of ~32 billion light years.

Redshift


Such distant objects are hard to spot but this might be a z=10 object:
www.nasa.gov...

a reply to: Arbitrageur

Thanks for the detailed reply.

I thought that inflation occurred after the Big Bang and at the end of the inflationary period, the universe continued to expand. So Zero point energy means that the energy from inflation was transferred to expansion such that the amount of energy in the universe remains that same?
Inflation energy is supposed to be balanced by the negative gravitational energy. But does that suggest there was some sort of mass generated by inflation? How did they calculate the amount of mass present during the inflationary period? And if it was balanced, why would expansion continue? Wouldn't energy be net zero with no expansion possible?

I was reading this brief explanation, but it doesn't make sense to me, particularly the last sentence about "cancelling matter....)

Free-lunch interpretation
A generic property of inflation is the balancing of the negative gravitational energy, within the inflating region, with the positive energy of the inflaton field to yield a post-inflationary universe with negligible or zero energy density.[5][6] It is this balancing of the total universal energy budget that enables the open-ended growth possible with inflation; during inflation, energy flows from the gravitational field (or geometry) to the inflaton field—the total gravitational energy decreases (i.e. becomes more negative) and the total inflaton energy increases (becomes more positive). But the respective energy densities remain constant and opposite since the region is inflating. Consequently, inflation explains the otherwise curious cancellation of matter and gravitational energy on cosmological scales, which is consistent with astronomical observations.[7]

en.wikipedia.org...

a reply to: Phantom423
In the early universe, we call the rapid expansion "inflation" related to the hypothetical inflaton field and particle, and after that ended we refer to the metric expansion of space caused we think by expansion leftover from inflation plus acceleration caused by dark energy (which may be vacuum energy).

The creation of matter called nucleosysntesis and other phases of the universe are discussed in this interesting link:
Chronology of the universe
Note the diagram at the top showing both types of expansion and the section 3.5.1 on nucleosynthesis

I was reading this brief explanation, but it doesn't make sense to me, particularly the last sentence about "cancelling matter....)

OK let's use an analogy. A young man who just graduated from high school has been working a short time and he runs short of money and goes to a payday loan center to ask for $500 so he won't be broke until his next payday.

He walks out of the loan center with positive $500 cash in one hand, and a contract in the other hand saying he owes them $500, so it has a value of negative $500. If you add the two together, his worth is still zero, they cancel each other out.

Now apply that analogy to the zero energy universe hypothesis, where mass plus dark energy is the positive energy, and gravitational energy between the masses is negative energy, and the two cancel each other out, resulting in zero total energy. Does that analogy help?

Sean Carroll wrote this piece on the topic and I'm not sure if it will increase or decrease your understanding, as it may appear somewhat ambivalent, but that's because some of the terms and concepts are not so clear cut as he explains:

Energy Is Not Conserved
Basically he says the zero energy universe hypothesis which may be true from a certain perspective, may not be true from another perspective, so, the article is ambivalent, though the ambivalence may not be the author's fault but rather results from the complexity of the concepts and how they are communicated.

a reply to: Arbitrageur

Question: what do the terms circled in the jpeg mean? They appear in the Expanding Confusion article but are not defined. Thanks.

originally posted by: Phantom423
a reply to: Arbitrageur

Question: what do the terms circled in the jpeg mean? They appear in the Expanding Confusion article but are not defined. Thanks.

The standard unit of distance measurement used by astronomers is the "parsec" which is about 3.26 light years.

Mpc is a million parsecs (Megaparsec) and Gpc is a billion parsecs (Gigaparsec).

Yr is of course year so Gyr is Gigayear or a billion years

originally posted by: Phantom423


I thought that inflation occurred after the Big Bang and at the end of the inflationary period, the universe continued to expand. So Zero point energy means that the energy from inflation was transferred to expansion such that the amount of energy in the universe remains that same?
Inflation energy is supposed to be balanced by the negative gravitational energy. But does that suggest there was some sort of mass generated by inflation? How did they calculate the amount of mass present during the inflationary period? And if it was balanced, why would expansion continue? Wouldn't energy be net zero with no expansion possible?

I was reading this brief explanation, but it doesn't make sense to me, particularly the last sentence about "cancelling matter....)

Free-lunch interpretation
A generic property of inflation is the balancing of the negative gravitational energy, within the inflating region, with the positive energy of the inflaton field to yield a post-inflationary universe with negligible or zero energy density.[5][6] It is this balancing of the total universal energy budget that enables the open-ended growth possible with inflation; during inflation, energy flows from the gravitational field (or geometry) to the inflaton field—the total gravitational energy decreases (i.e. becomes more negative) and the total inflaton energy increases (becomes more positive). But the respective energy densities remain constant and opposite since the region is inflating. Consequently, inflation explains the otherwise curious cancellation of matter and gravitational energy on cosmological scales, which is consistent with astronomical observations.[7]

en.wikipedia.org...

There are different ideas. One is that gravity acts in reverse near the beginning of the big bang.
I don't think there was any mass during inflation, it supposedly happened when the universe was about the size of an atom and blew up quickly to the size of a basketball. Quicker than it should have been expanding which was probably around the speed of light.
The temperature when the universe was atomic size was too high for mass to form. The question is at what temp does quark-gluon soup melt into weird quantum energy? Quark-gluon soup is the last type of matter that will remain when temperatures get to extreme levels. But when an entire universe is crunched to an atom, or less, there is probably a point when even that must disintegrate into whatever ball of super-energy first existed.
The 4 forces are thought to be unified at this point also, all one force. But what exactly does that force do?
Does it have just one function? Like keep a ball of super-energy stable (for a while)?

There is also the problem of quantum strangeness that may effect the entire universe at that point?

There is probably some energy in that "zero point field" concept but metaphysics writers have totally taken advantage of it. The way to get energy from that would be to break space-time. We don't know how to do that or even what that means really

originally posted by: [post=20013468]joelr There is probably some energy in that "zero point field" concept but metaphysics writers have totally taken advantage of it. The way to get energy from that would be to break space-time. We don't know how to do that or even what that means really

Know ye not this has been achieved already

originally posted by: Nochzwei

originally posted by: [post=20013468]joelr There is probably some energy in that "zero point field" concept but metaphysics writers have totally taken advantage of it. The way to get energy from that would be to break space-time. We don't know how to do that or even what that means really

Know ye not this has been achieved already

Considering creating a symmetry break in space time is probably impossible love to see the proof of that one. If it were to be possible you would need negative energy. But even with that predictions say you would be a space time but not break it. Problem is simple if you broke space time what ever was there just wouldn't be any longer. Think of the ultimate disappearing trick. It would no longer be part of our universe and you could say ceases to exist.

There are no known predictions to break space time but even if you did it would be doubtful you could even tell. Say we had a symmetry break on earth if the object didn't disappear it's quite possible for it act normally because the violation would be so small as to be undetectable.I won't go into this now but a symmetry break at the subatomic level would be to small for us to measure. Bottom line is if you did violate symmetry either the object disappears or you can't detect it did either way you would be wrong.

If you achieve anti gravity effect wrt time, you are progressively breaking space time symmetry wrt time. Yes at the point of levitation off the ground, the object or anti gravity machine would/may disappear
a reply to: dragonridr

originally posted by: Nochzwei
If you achieve anti gravity effect wrt time, you are progressively breaking space time symmetry wrt time.

Didn't you have an older thread where that was allegedly confirmed by measuring the pH of two tomatoes, or am I thinking of someone else?

a reply to: dragonridr

thank dragonridr,

although, I understand that the nuclei moves with the direction of magnetic field, but it does not happen instantly, me thinks. Field (or part of it in case of distortion) first, nuclei follows. Just like you would move one magnet on a table against another magnet. Second magnet reacts with delay to your moving first magnet with your hand. We can disregard the friction factor, effect still there.

Other wise you conclude that an atom is absolutely rigid. Movement would not be possible as kinetic energy has to be assumed somehow by the atom that was hit.

I might be wrong but will look into it more when free time allows.

I have a question about gravity process.

Say, the Moon gets closer to Earth. It is predicted that the Moon will start falling apart due to gravitational 'forces'.

The reason I put word forces in quotation marks is that to me still, gravity is not a force. Well, from QM pov it is. But GR says gravity is not a force.

What if we place instead of the Moon a rubber sphere with equal mass. Now as getting closer to Earth what would we see?
Right, the rubber ball will lose it round form and become elongated, distorted.

From GR perspective how this could be explained?

Not sure if my writing is delivering the content of the question hehe)) Hopefully some one understands it.


cheers)

No I am still referring to the Ark Video
a reply to: Arbitrageur

a reply to: Arbitrageur

If the universe is flat, isn't the Hubble sphere really an ellipse or a curve on a plane? The volume of the Hubble sphere is calculated as c/Ho. Volume for an ordinary sphere is v =4/3 pi r(cubed). Is "sphere" a misrepresentation of what the shape is - or maybe we don't know the shape?

originally posted by: greenreflections
Right, the rubber ball will lose it round form and become elongated, distorted.

From GR perspective how this could be explained?

You're exaggerating the difference between relativity and Newtonian mechanics, because at non-relativistic conditions they make approximately the same predictions. The Roche limit was calculated in 1848 and nobody needed to re-calculate that when General Relativity appeared in 1915 though one could apply GR corrections if they were significant, but I think in typical applications of the Roche limit they're not significant.

The Roche limit applies to objects with no tensile strength, held together only by gravity. If a satellite has tensile strength it can orbit inside the Roche limit, however I think you'd have better luck with a more rigid giant ball less stretchy than a giant rubber ball.

It's actually tidal forces that pull objects apart inside the Roche limit, so think about what that means for an object that stretches. When it stretches, tidal forces increase, causing it to try to stretch more, causing tidal forces to increase more...and so on. Even rubber bands can break if you keep stretching them. UV radiation from the sun would eventually break down the stretchy properties of the rubber so I think this would cause the eventual destruction of the rubber ball inside the Roche limit via tidal forces and degradation of tensile strength.

originally posted by: Nochzwei
No I am still referring to the Ark Video
a reply to: Arbitrageur

If that wasn't you then you have a doppelganger who makes exactly the same claims about relativity having time dilation backwards, and who similarly presents flawed evidence in support of that claim. Even the writing style was similar to yours. If that wasn't you (I suspect it probably was) then you should hook up with that guy so you'll finally have someone who can agree with your anti-relativity claims. I think he went by AngelicResurrection or something like that.

originally posted by: Phantom423
a reply to: Arbitrageur

If the universe is flat, isn't the Hubble sphere really an ellipse or a curve on a plane? The volume of the Hubble sphere is calculated as c/Ho. Volume for an ordinary sphere is v =4/3 pi r(cubed). Is "sphere" a misrepresentation of what the shape is - or maybe we don't know the shape?

The shape of the Hubble sphere is a sphere, and the geometry of the universe appears to be flat though there are of course caveats to this such as the citation below and others.

We can't see the whole universe so we don't know the shape of the entire universe, nor whether it's finite or infinite. So all we can observe is the observable universe and it's a spherical region of the larger universe. The Hubble sphere is a smaller sphere (radius a little over 14 billion light years) inside the sphere of the observable universe (radius a little over 46 billion light years). The irony in the wiki article for Hubble sphere is incredible since they say Hubble sphere is often confused with observable universe and they add to the confusion by showing an illustration of the observable universe instead of an illustration of the Hubble volume:

Hubble Sphere

However, the term is also frequently (but mistakenly) used as a synonym for the observable universe; the latter is larger than the Hubble volume.

If the universe has "flat geometry" we would expect two parallel laser beams to remain parallel forever. Geometry in this context refers to four-dimensional space-time so if you try to visualize it in three dimensions, you don't get the concept. We can't really visualize this type of four-dimensional curvature accurately, but we can measure and calculate it.

What is the geometry of the universe?

In a perfectly flat universe, two laser beams aimed parallel to each other would remain parallel forever. If the universe were not flat, then the laser beams would eventually diverge or converge...

We see evidence of this flatness in the cosmic microwave background (CMB). Overall, the temperature of the CMB is very uniform. There are small variations in its temperature, but those small variations average out. This is exactly what we would expect with if the universe is (on average) flat....

But recently we've found that there is a bit of an anomaly in the CMB. ...

While many proposals to explain this anomaly invoke exotic ideas such as multiverses, a recent paper in Physical Review Letters shows that the anomaly could be explained entirely by cosmic curvature. The team has demonstrated that the observed anomalies (if real) can be accounted for by a universe with a saddle shaped universe, seen as the left figure in the image above.

If the universe has "flat geometry" we would expect two parallel laser beams to remain parallel forever. Geometry in this context refers to four-dimensional space-time so if you try to visualize it in three dimensions, you don't get the concept. We can't really visualize this type of four-dimensional curvature accurately, but we can measure and calculate it.

a reply to: Arbitrageur

Yes, I can't say I understand, but I get the point. But to say that you can't visualize something, but yet you can measure and calculate it leaves me somewhat puzzled. It's probably a poor analogy, but I can't imagine synthesizing a chemical compound or isolating an unknown compound without being able to measure it, calculate bond energies, determine its chemical structure, etc. A thousand questions like how do you know the measurements are accurate - what are the standards that you compare them to?

Thanks for the links. They'll last a long time reading them a hundred times

originally posted by: Phantom423
Yes, I can't say I understand, but I get the point. But to say that you can't visualize something, but yet you can measure and calculate it leaves me somewhat puzzled. It's probably a poor analogy, but I can't imagine synthesizing a chemical compound or isolating an unknown compound without being able to measure it, calculate bond energies, determine its chemical structure, etc.

I said we can't visualize it accurately, I didn't say we can't visualize it at all. With the shape of the universe we only need to take a 2D surface of the Earth versus 3D volume of the Earth, which we can visualize, and add one more dimension. We know if we take two points on the Earth's equator 90 degrees apart, and a third point at the north pole and draw a triangle, that all three 90 degree angles add up to 270 degrees, not 180 degrees like a triangle would on a flat surface, so this shows the Earth's surface is curved. Likewise if triangles in space have angles that add up to less or more than 180 degrees we know space isn't flat. If the angles add up to exactly 180 degrees it's flat.

A thousand questions like how do you know the measurements are accurate - what are the standards that you compare them to?

I thought the CMB example was straightforward, you're just comparing one part of the sky to other parts of the sky to see if it looks the same everywhere, or if you see distortions. Of course the accuracy of measurements can be in question and they certainly are in the article I cited. We're not sure if that's even a real anomaly and even if it is, we're not sure if it's caused by the curvature of the geometry of the universe or something else.

Yes your chemical compound example is an even bigger disaster if you try to visualize what happens according to quantum mechanics, because we have to visualize in six dimensions instead of four and we can't visualize over three dimensions.

www.eng.fsu.edu...

For multiple-particle systems like the electrons of the hydrogen molecule, showing the magnitude of the wave function as grey tones no longer works since it is a function in six-di­men­sion­al space. You cannot visualize six-di­men­sion­al space.

We can still make accurate measurements and predictions. How? Because unlike humans who are unable to visualize more than three dimensions, mathematics has no such limitations and it's no big deal to add extra dimensions in mathematics. We can also make measurements to validate what the predictions predict, and they generally do, even for things like "spooky action at a distance" which is another quantum mechanical effect that occurs in space we can't visualize. I still don't know how to visualize that, but we do have some admittedly inaccurate visualizations of chemical bonds in three rather than six dimensions.

Lo as I recall we were on about breaking space time symmetry and you cherry picked one line from that post to go into wild speculationn. Besides any engineer in this world worth his salt will phoo phoo GR and actually feel like drumming those who embrace it
a reply to: Arbitrageur

originally posted by: Nochzwei
Lo as I recall we were on about breaking space time symmetry and you cherry picked one line from that post to go into wild speculationn. Besides any engineer in this world worth his salt will phoo phoo GR and actually feel like drumming those who embrace it
a reply to: Arbitrageur

Really that's surpRising since countless engineers rely on its equations. I think what you mean to say is engineers with little understanding of science. Like say a janitorial engineer.