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New Clues About the Nature of Dark Energy
Jim Mansfield writes "With the Hubble space telescope no longer being serviced by NASA, it's good to see one of their hardest working and most famous satellites in the news again. According to their press release on the nature of dark energy, Einstein may have been right after all - and even if he turns out to have been wrong, it seems that dark energy is not going 'to cause an end to the universe any time soon' ... whew, that's a relief." See also a space.com story.
I wouldn't worry about the Hubble, it will just end up drifting off into space only to return 300 years later as H'ble, the super intelligent sentient telescope of the future, bent on destroying the human race.
Ok, so maybe there is reason to worry....
The restaurant at the end of the universe must be really far...
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If the repulsion from dark energy is or becomes stronger than Einstein's prediction, the universe may be torn apart by a future "Big Rip," during which the universe expands so violenty that first the galaxies, then the stars, then planets, and finally atoms come unglued in a catastrophic end of time.
This is quite a shift from the implosion theory that results in pre-'Big Bang' conditions causing a loop in time.
"Now you see that evil will always triumph, because good is dumb!"
- Dark Helmet
After we have all (I assume that doesn't include any creationsists) adhered to the scientific theory of The Big Bang and the beginning of the Universe as we know it, I can only think that we can begin to accept the fate of the Universe.
As dark matter destabalizes, essentially matter is pulled apart at the atomic level. Some thing tells me The Big Rip, is what we are in for.
The universal constant is a nice theory and would be the better, happily-ever-after option, but in reality it seems a little far fetched if the expansion of the Universe is accelerating. It means that eventually speed will over come matter and every thing disintegrate and get ripped apart.
Before it gets to that stage, stars will become a rare occurance. The chain of star birth and death results in smaller stars, and once stars get small enough they become like our Sun -- too small to undergo the explosive death that would provide enough mass for future stars. Eventually there won't be enough clouds of hydrogen massive enough to start nuclear fusion.
Given enough time, current theories suggest that the universe seems to be screwed either way.
Of course, 2x (near-as-dammit-zero-certainty) is pretty much the same as (near-as-dammit-zero-certainty)...
A lot of new physics does seem to be increasingly theoretical and "out there" on the proverbial limb. It would be good for the practical lot to catch up with the theoretical lot... unfortunately, trying to verify these out-there hypotheses seems to involve larger and larger atom-smashing accelerators. Lets just hope they don't need to find the 'Higgs Boson' (hint: ohhh WAAAY ohhh, ummm barrray
Simon
Physicists get Hadrons!
I think dark matter doesn't exist. It can be useful in the models, like ether could, but nothing more than that.
"And in the end of days, God shall eat Mexican food and several beers and ye verily shall His mighty thunder rend the Heavens."
You're wrong. Aether was thought to be a physical fluid whose ripples were the basis of the wave-like nature of light. This was proven not to be so by Michelson and Morely, who showed that the speed of light was the same no matter if it were going with or against the aether (which was presumably flowing past the moving Earth). Dark energy is a field, like light or gravity, which presumably has no preferred frame of reference (like light or gravity).
This line no sig
It wasn't the introduction of the cosmological constant per se that Einstein thought of as his greatest blunder, it was the failure to realize and predict that the Universe is expanding. The cosmological constant he had there to get a static universe, and that's bad. Also, the cosmological constant isn't Evil, it comes rather naturally from solving the equations. I never got as far as actually doing that, but I followed a back-of-envelope solution once, and it comes out sort of like an integration constant. I think of it as a natural parameter that should be constrained by observations just like any other parameter, and I see no particular reason why it should be 0.
Employee of Inrupt, Project Release Manager and Community Manager for Solid
I doesn't take an Einstein... oh wait. Nevermind.
Are you Corn Fed?
From the article:
"Riess' team uses Hubble to find stars that exploded when the universe was about half its present age. A certain type of these supernovas, as they are called, shine with a known brightness."
Supernovas, you say? Wow, what a fascinating new concept for readers of Space.com!
I mean, come on!
The Humblest Mollusk on the Net
I get the feeling that we are trying to fill ..explosions and ever
a gap but with what???
Observer: Look at those galaxies..they are moving appart.
Braniac: Yes, that's because the big-bang long long time ago.
Observer: They look very old and they appear to move slower as they drift compared to the young galaxies.
Braniac: Of course, they are loosing momentum. But don't be deceived, at some point all universe is going to loose cohesion and become rippi-bits!
Observer: Howbout that cluster over-there? Those galaxies are quite old and they are driftin faster than the young ones! What gives??
Branica: Er ur..is dark energy pushing them appart, dark energy is spreading the galaxies.
Observer: And the big bang.
Braniac: yes, that too
present dark-energy.
Observer: Far out!
Braniac:(scratching her head and punching madly
at her calculator and giving a big sight of
frustration)yeah, riveting.
- these are not the droids you are looking for -
Whats more likely? This mysterous dark energy exists and compromises 70% of the mass/enery of the universe even though we can't see it anywhere locally, or our theories are wrong?
I suggest reading www.ebtx.com on the nature of dark energy. This guy is right, or at least close.
Matter attracts matter; this we know. The rest of the theory explains that space attracts space, and matter repels space. Matter and space are polar opposites (as well as logical opposites).
Einstein wasn't relative enough in his theories. He declares C as constant and bases all other observations off it, when in fact you can change all the physical constants continuously and arrive at the same results. If C changed, as long as h, G, and about 18 other 'constants' also changed, we couldn't tell, from our point of view.
Is the universe expanding, or are we all shrinking? From a relative point of view there is no difference.
If you fear things involving physics, skip the rest of this post. Alright, for those who are interested, it seems like 70% of the current energy density of the universe is in some form of "dark energy", as was previously stated. The Universe is currently 13.7 billion years old. We say that every component in the universe has an energy density and a pressure. Dark energy is different from things like normal matter and light, because these have positive pressures. (Normal matter has a very small pressure). But dark energy has a negative pressure, which means it works opposite to gravity. Everything that has a pressure that we can physically think of (well, that I can physically think of) has a pressure between (-1)*energy density and (+1)*energy density. A big rip will only occur (and it will only occur in the very distant future) if the dark energy has a pressure that is outside this range, such that pressure is less than (-1)*energy density. This is, of course, possible, but unlikely in my view.
The fact that the universe is accelerating is not the same as the "big rip". The accelerating universe, as we understand it now, sort of means that the space between everything and everything else is getting bigger all the time. However, in order to discover this (and the expansion of the universe in general), we have to look at very distant galaxies - we don't see our own galaxy flying apart, and some other galaxies bound together in our local galaxy cluster are orbiting or moving toward ours. In general, objects that are in bound states - whether gravitational bound states (like solar systems and galaxies) or other bound states (atoms, etc.) will remain held together even as the distant galaxies which are not tightly bound to us zoom away. Our own situation on earth would be completely unaffected - you'd need a big telescope to even tell the difference. The idea of the "Big Rip" is that this condition that "bound things stay bound" (the dominant energy condition) might be violated, that dark energy might be so extreme that not even bound objects could keep from eventually dissipating. That idea is HIGHLY theoretical - there's no particular evidence for it, and until recently most theorists thought it was ridiculous. But, of course, this is science - we have to think about even the weird possibilities.
You're right, the natural step when we learn that the universe doesn't obey Newton's laws should be to try to modify Newton's laws, not to imagine that there is a magic 95% of the universe with funny unobserved properties. The thing is that this isn't the only evidence for dark matter. There are a number of different lines of evidence which lead to the same conclusion - the orbital behaviors of galaxies and their clusters, the adundances of various light elements in the universe, the behavior of the cosmic microwave background, x-ray emission from clusters, etc. It turns out that no matter how hard we try, we can't modify Newton's laws to get the right answer to all of these. Gravitational lensing (the bending of light by the mass of distant galaxies and clusters) is really impressive in this regard - modifying Newton's laws (and general relativity) in the desired ways should have essentially no effect on it, and it definitely looks like there's dark matter (and even allows us to map its distribution). Dark matter really seems like the SIMPLEST answer, from the point of view of someone who knows the data! Dark energy was the subject of the article, however, and that's quite a bit different. As of right now, I'd say that we DON'T have very convincing evidence that this isn't just a modification of general relativity. All of our particle physics-related ideas seem far too complicated. Oh, and chaotic systems still obey the laws of classical physics - the systems are just so complicated that knowing how the individual atoms are behaving is not very helpful for predicting the behavior of the macroscopic system.