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Big Bang or Cosmic Crunch?
BrianGa writes: "Yahoo news is reporting on Princeton University physicist Paul
Steinhardt suggesting that the universe never began and will never end,
driven forever to expand in a series of monster explosions and contract every
eon or so in a cosmic crunch. This is directly contradictory to the
big-bang
theory. The model of the universe envisioned by Steinhardt sees the
big bang as merely a turning point on an infinite road."
Hobbes: "Well what would *you* call the creation of the universe?"
Calvin: "The Horrendous Space Kablooie!"
Quidquid latine dictum sit, altum sonatur.
then perhaps Nietzsche was right after all, as I've said infinitely many times before.
This is hardly a new theory. The only thing which I see that makes it distinct from the age-old theory with the same outline is that it invokes dark matter as part of the mechanism. Hopefully, if presented in scientific language rather than yahoo-interview, it has some interesting new twist, but I'm just not seeing it here.
Also, he says "When it's changing slowly, it's gravitationally self-repulsive and when it's changing fast, it picks up speed, it's gravitationally self-attractive". It's slow and repulsive now. What is supposed to ever make it speed up in the future since it's own existance is what is making it slow now?
I agree that we should definately continue looking for answers for this old question (the origins of the universe), but the fact of the matter is that any conclusion we come up with is more or less assumed from postulated data. This includes yesterday's post regarding the age of the universe. We can examine the universe from our position in it, but its impossible to make 100% factual judgements about certain things such as the mass of the universe, etc since there is a great deal we cannot see, and whatever is hiding behind what we can't see is included. Our data pool is limited due to our lack of ability to leave our planet or solar system in any 'real' sense. Again, we should not stop for that would be foolish, but we must remember that these findings are not fact, but theory and should be thought as such.
"What can a thoughtful man hope for mankind on Earth, given the experience of the past million years? Nothing." -Bokonon
The universe will expand and contract.. but what force is causing the expansion and contraction? Is it a natural extension of some force that we've yet to appropriately measure?
Well because there is a gravitational force between all matter within the universe, no matter how far. So eventually all matter will form into massive clumps. Even if the last 2 remaining clumps are really really really really far away (really) from eachother, there will still be a small gravitational attraction toward eachother. It will take eons for them to come together again, but it will happen... at the center of the universe.
We are the dust of long dead stars.±
Excerpts from interview of Sir Martin Rees, Astronomer Royal of England by Claudia Dreifus, New York Times, April 26, 1998
but it appears Stars are the dust of long, long dead us?
but these gravity theories apply mostly to matter, don't they? how does this apply to time and other "variables"?
There's a lot of theories about alternatives to the big bang besides the one mentioned in the Yahoo article. The main one that is getting a lot of interest in scientific circles isn't this new one in the Yahoo article. Instead, it's the so called Ekpyrotic theory, with the name coming for the Greek word for fire. It is so intresting because it brings together two disparate areas of physics: inflation and M branes. Inflation is a weird concept that says the universe expanded from the diameter or an atom to the size of a grapefruit almost instantly - required to explain the way galaxies are clumped and clustered in the sky we see today and first postulated by a guy named Alan Guth. M branes are an offshoot of string theory postulated by Ed Whitten. There's tons of stuff on these topics on the web; all of it is facinating, enter any of these terms in a search engine and keep reading. Next stop, Google...
Here's a summary. I don't have the book any more so I can't quote, but notice in the summary of chapter 10 where the summary reads "When shrinkage to below the Planck length is attempted, the crunch becomes a bounce."
I've believed exactly this for quite some time now.
Secondly, this doesn't go directly against the big bang theory. the big bang created _this_ universe, yes, but before it were an infinite amount of "big bangs" and "big crunches."
doesn't conflict, just tells the whole story.
What comes first, finding a teacher or becoming a student?
Lee Smolin talks about an evolutionary model in The Life of the Cosmos which has the great advantage, for those who can get their head around it, of not requiring any assumptions about special conditions just arising out of nowhere, which is to my mind indistiguiushable from always having been there.
Because we can't really escape them here, we have a lot of trouble contemplating anything at all which does not involve space, time, energy nor matter. An evolutionary universe gets us past this, not because it is concerned about survival, but about fecundity of the production process whereby black holes rebound to form disconnected big (and maybe sometimes little) bangs, then extrapolating this process back till when there was truly nothing except the possibility.
Granting William of Occam an oversized razor, it would surely favour Smolin's idea of evolution from a state where the only certainty is that nothing is unstable to the world we find ourselves in; rather than Ekprotic Theory, any of the many attempts to revive the steady state corpse, the quantum theorists' many world interpretation or "intelligent design".
Cycles never truly come back to their starting point.
-- Our systemic servants do not good masters make.
The following hypothesis has been thoroughly vetted at many cocktail parties, so its' credibility and clarity of concept is unassailable: ..stuff.. by a mechanism that we don't understand yet, then the aggregate mass (infinite with a big I) at tremendous distances from us would be sufficient to bend space time in such a way so as to make it *appear* that everything is else is moving away from us. No matter where you went, when looking out to the 'edge' you'd see red shift all the way down to infinitely long wavelengths. :)
Here's the deal.
There _was no big bang_. The universe is _not_ expanding.
"Huh? I hear you say. "But, but what about red shift? The hubble constant?"
Simple. Two words: General Relativity.
If the universe stretches out infinitely in all directions, is of a density similar to here everywhere, and somehow replenishes matter lost to black holes and
The universe, in effect would appear to have an 'event horizon'.. a 'Black Sphere', if you will, beyond which nothing would be visible.
Oh, this idea would explain all that pesky 'background radiation" too.
Of course, measuring distances gets to be a real bear, but that's outweighed by being able to learn cool stuff about time-space geometries by playing around with the red-shift data viewed in a new analytical framework.
So there you have it.
When do I get my grant
Brak: What's THAT?
Thundercleese: A light switch.. of TOTAL DEVASTATION!
He also seems to think he has an alternate solution to the flatness problem. This is the puzzle that according to gravitational theory, the curvature of space could be anything, but observationally, the curvature is zero. Seems like an odd coincidence. Guth came up with the inflation theory to explain this -- Steinhardt has another theory.
So you're right, it's not contradictory to big bang theory. But it's not really part of it either.
Not necessarily. The term escape velocity is exactly the opposite of what you are saying. Escape velocity is the velocity an object needs relative to another to never fall back into it. The more gravitational attraction there is, the higher the velocity is needed to escape. This is why the amount of mass in the universe is so closely related to wether the universe will expand forever or collapse again. If there isn't enough mass, there won't be enough attraction to slow the expansion to a stop and reverse it.
"Big Bang" "Cosmic Crunch" "M Brains" Is it just me, or are many astrophysicists hanging out far too long in the candy aisle while trying to think up names for thier pet theroies.
"Your superior intellect is no match for our puny weapons!"
If the universe stretches out infinitely in all directions, is of a density similar to here everywhere, and somehow replenishes matter lost to black holes and ..stuff.. by a mechanism that we don't understand yet,
...aaaand, stop right there.
Matter isn't lost when it goes into a black hole; it ends up in the black hole's singularity, an infinitely dense point of matter in the center.
Black holes are also thought to "leak" material in the singularity back out over time.
(Disclaimer: IANAP, although I'm enamoured with the topic.)
It's not just subatomic particles that slow down, which is Einstein's true stroke of brilliance. Einstein began down the road of Special Relativity by postulating that Newton's Principle of Relativity -- no matter where you are in the universe, the laws of physics are the same for all inertial (constant velocity) frames -- is correct. One of the laws of physics, courtesy of Maxwell's Equations, requires that the speed of light in a vacuum, c, is a constant. So, if both of these postulates are correct, then everyone will agree on the value of c in all inertial frames.
This deserves some illustration. Suppose you're on a hypothetical train traveling at a constant velocity of 0.5c towards a friend, and you point a flashlight straight forward and turn it on. You perceive the beam of light as traveling toward your friend at speed c; however, your friend sees the beam of light as traveling toward him at speed c, and not speed 1.5c. How can this be?
The answer that Einstein came up with, and the only known set of physical laws of motion that is consistent with both Maxwell's Equations and the Principle of Relativity, requires that your friend sees you as flowing through time at a slowed rate, whereas you see him as the one who is slowed down. With some extra geometry not far beyond a high school math student, it's not hard to prove that the length of (you|your friend) must contract; also, some modifications to Newton's Laws are required in order to make the laws of inertia and momentum self-consistent, making (you|your friend) appear to have more mass.
It is an inescapable conclusion of Special Relativity that the actual flow of time slows down -- General Relativity, the theory which tied SR and gravity together while introducing time as a 4th dimension, is not even required to prove this result. The very CRT that you're using to view this article right now could not possibly exist if Maxwell's Equations were grossly wrong, meaning the only way to prove SR grossly wrong about the flow of time would be to disprove the Principle of Relativity -- by demonstrating that the laws of physics vary depending on where you are in the Universe!
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This makes perfect logical sense to me. Why would time have a beginning OR ending? Just because human lives have them?
Maybe "baby bangs" would be a better description.
If you read the theory as described by the guy
in the National Geographic story (linked from
the yahoo site), he basically says that cosmic
acceleration (the fact that, apparently, not only
is the universe expanding, the rate of that expansion
is increasing) makes everything spread so far
apart that you basically have new vacuum that can
spawn new big bang. I guess "big bangs"? I don't
know, it was short on details. He calls this state
of everything being spread so thin a "crunch"--it
seems to me more like, well, butter scraped over
too much bread (ok, that was just for fun). But
"crunch" seems to me like everything collapsing back
in on itself, where what he is saying is that things
are just spread so far apart that you have the conditions
for (a? many?) big bang(s?).
Liberty uber alles.
I read this book by Hawking some time ago; I make no claims about understanding it. He mentioned several logical possibilities, which should summarize what everyone else has been saying in spurious posts...
.sig you've ever seen.
1. A beginning with no end. Our universe began from the big bang and, if the gravitational pull of the center is not large enough to overcome the momentum of the explosion, will continue to expand though infinity.
2. A beginning with an end. The gravitational pull of the center can overcome the momentum of the explosion, resulting in a big crunch.
These two only describe our observable universe. Time begins with each explosion and ends with each contraction. If the gravitational pull, which grows as the universal spheroid becomes more massive, can pull the mass smaller than infinitesimal (mathematically speaking, I guess) then a bounce occurs, resulting in another explosion.
3. If the ratio of energy/mass remains constant with each explosion, then THE universe (not OUR universe) continues from -infinity to +infinity, as the article states.
4. If the ratio increases every time, the explosion will eventually provide enough momentum to overcome the pull of gravity (case 2). We may be in this state now, or we may not.
5. If the ratio decreases every time, then eventually the universe will be pulled into a point, with just enough energy to keep it there. Our universe may have this finite end, or it may not.
This is the greatest
They've even collected good evidence that the speed of light has changed over time...
Umm... Please back that statement up.
ok then your [sic] infringing on my copyright! Could you as [sic] me next time before STEALING my comments for your own?
That's why I mentioned that c is the speed of light in a vacuum. The speed of light in a non-vacuum medium is slowed down, to c divided by the refractive index of the medium (1.33 for water, for instance). Basic optics, known well before Einstein's time.
Citations, please?
I'm not the one missing the obvious. Unfortunately, Slashdot won't let me draw some ASCII art to explain, but I'll try and describe it in terms that you'll understand... remember that airspeed is speed relative to the air, and that air is essentially stationary compared to the ground when you're talking about Mach speeds.
From the perspective of the SAM site, the plane is moving at speed Mach 2 angle 0 with respect to the ground, then launches a missle that quickly assumes a path in which it is traveling at speed Mach 5 angle 315, which happens to be perfectly aimed such that it will impact the SAM site.
From the perspective of the plane, the SAM site is zooming underneath at speed Mach 2 angle 180. It launches the missle (let's presume it's guided), then observes as the missle fires up and assumes a path of travel with speed Mach 3.57 angle 293.5. The missle looks like it will fall short, except that the SAM site rushes underneath the missle just in time to be hit. Stupid SAM site!
In the train example, we have a train traveling at speed 0.5c angle 0. You are standing on the train, and your friend is directly in front of the train by a safe enough distance that he'll be able to sidestep the train when it gets close. So, from your perspective, your friend is rushing toward you at speed 0.5c angle 180, and the beam of light is rushing away from you at speed c angle 0. What does your friend see? According to Newton's mechanics, he should see you rushing toward him at speed 0.5c angle 0, and the beam of light should be traveling at speed 1.5c angle 0 (simple trigonometry -- you add two vectors with the same angle by adding their magnitudes). In reality, as confirmed by countless experiments, the most famous of which are known as as the Michelson-Morley experiments, your friend perceives the beam of light as traveling at precisely c. If you fire a railgun from the train with a slug that travels at speed 0.5c angle 0 relative to you, then your friend will see the slug traveling toward him at speed 0.8c angle 0. These results have been confirmed by many, many experiments, so the burden of proof is on Einstein's doubters to show -- using repeatable and accurate experimental methods -- that an alternative explanation can exist. The physics department at the University of California at Riverside has an excellent site introducing physics, including these two pages that explain why the ether theory from the late 19th and early 20th centuries is thoroughly debunked and cannot be modified to fit the facts without becoming an unfalsifiable hypothesis (i.e. a matter of faith).
Again, see the above links for an explanation of why ether theory cannot be falsified if it is modified to be consistent with our existing knowledge.
The statement assumes that relativity is true, but it's a testable and falsifiable statement that, if it were false, should be trivial to debunk. Despite multitudes of measurements and experiments, especially by the people who passionately desired to show it to be false, that very statement has not been found untrue even once.
Yes and no. He understood math quite well, but due to dyslexia he couldn't deal very well with the rote memorization and mechanized learning required of him by the school system. He eventually learned to deal with it well enough to get excellent grades.
Range Voting: preference intensity matters
Heh, nice. You would have made a fine ancient greek scientist. Pity we have moved on since then.
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