The Big Bang's Last Great Prediction 80
StartsWithABang (3485481) writes "Even with the add-ons of dark matter, dark energy and inflation, the Big Bang still thrives as the most successful scientific model of the Universe ever constructed. It not only accounting for phenomena like the abundance of the light elements, the cosmic microwave background, and the Universe's large-scale structure, but it's led to observable predictions about their details that have since been verified. But there's one thing the Big Bang has generically predicted that we haven't been able to test: a cosmic background of low-energy, relic neutrinos."
Relic Hunter (Score:5, Funny)
We must collect the low-energy neutrinos before the neo-Nazis find them!
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And yet... (Score:1)
The humble banana disproves this all.
Re:only a blog post? (Score:5, Funny)
Bloggers are the new journalists in the hipster era, soon to be known as the Stupid Ages.
Theory as it stands is wrong (Score:5, Interesting)
For instance, the Hercules–Corona Borealis Great Wall [wikipedia.org]
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Re:Theory as it stands is wrong (Score:5, Informative)
No.
Look up inflation.
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Nope; because of metric expansion, objects whose light we are now receiving can be further away than the product of the speed of light and the age of the universe.
Re:Theory as it stands is wrong (Score:5, Interesting)
To explain further... metric expansion is the central premise of the big bang theory. SPACE is growing larger... the matter within it is not moving away from each other. (well they might be but that's not relevant) So if you and I were standing next to each other and not moving, the distance between us would still be growing. On small scales the effect isn't even measurable it's so small. But the effect increases with the more distance between us. When you get to galactic scales the effect is enormous. The speed of light limit is a result of the geometry of space-time. Think of it like a right triangle... you change one line, and that affects the angles and lengths of the others. Expansion is like changing the size and shape of the paper the triangle is drawn on.
Or at least that's always been my understanding. Physicists feel free to correct me. Time Cube guys, stay out of it. :-)
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And gravity still affects the mass in space as it expands, so that items that are strongly gravitationally bound remain so. Yet items that are weakly bound can grow apart.
Bonus question: how does this expansion affect the orbits of planets around stars and the orbits of stars in a galaxy?
Re:Theory as it stands is wrong (Score:4, Funny)
Nope; because of metric expansion, objects whose light we are now receiving can be further away than the product of the speed of light and the age of the universe.
So in the US they have imperial expansion? Of course, that explains a lot!
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It doesn't, as far as I can tell; the citation given in the article doesn't actually mention any of the assertions made in that section. What the Great Wall does cause problems with is the "cosmological principle": that the universe is largely isotropic, i.e. smooth.
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Re:Theory as it stands is wrong (Score:5, Informative)
The issue is that the big bang implies the universe is fairly isotropic; it can be clumpy to a certain degree, and the exact degree of clumpiness depends on the exact model you use. Although this Great Wall is a bigger clump than current models allow, you can imagine that there could be other big bang models where the allowed clumpiness is a bit larger. (In fact we know from other observations that we will have to come up with slightly different big bang models than the ones we currently use anyway.)
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Well don't I feel silly now.
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Yeah, the current flavour of big bang if you like. The idea of a big bang itself is pretty robust at this point, but while we've spent a good long time figuring out exactly what happened, the existence of this Great Wall implies that we're off track.
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Indeed, it might imply that the whole cosmology is wrong in some way and we need a new one, although that's less likely than some little tweak to the existing one.
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Re:Theory as it stands is wrong (Score:4, Insightful)
Essentially, all models are wrong, but some are useful.
-- George E. P. Box
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Because it's "lumpier" than the universe should be based on our current understanding. At sufficiently large scales, any one section of the universe should look basically like any other section. The Hercules-Corona Borealis Great Wall (and other features of similar size) are above the "sufficiently large" scale so we don't expect to see organized structures but we do, so our understanding isn't complete (which is hardly surprising).
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Depending on who you talk to, evidence either contradicts or makes the Big Bang incomplete.
Wikipedia Big Bang [wikipedia.org] mentions these 3 problems:
* the horizon problem,
* the flatness problem,
* and the magnetic monopole problem.
The typical kludge is "Cosmic Inflation [wikipedia.org]", but that hack creates even more problems. (" inflation is the expansion of space in the early universe at a rate much faster than the speed of light temporarily.") Paul J. Steinhardt, one of the founding fathers of inflationary cosmology, has recently
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Correction: I meant 1/137.03597 = 0.00729735411805, NOT e = 0.08542455
1/137.03597 with about an uncertainty of about 2 in the last decimal place gives us:
* max 137.03599 = 0.0072973530... still too large
* min 137.03595 = 0.007297355... WAY too large
The modern a = 0.00729735257, looks like Fenyman should of said with about an uncertainty of about 3 in the last decimal place.
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"they like to remember it as the inverse of its _square_" (emphasis mine). You need to take the square root of your 0.007... to get the comparable number. sqrt(0.0072973530) is .085424557359 and sqrt(0.007297355) is .085424545652, each of which, rounded to the proper number of figures, matches Feynman's figure.
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Or, going the other way, 0.08542455 ^ 2 => .007297353742, and 1/0.007297353742 => 137.035977061724
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Yes, thanks, I already corrected that mistake 3 hours earlier.
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Ah, gotcha. You appeared to be comparing 0.08 to 0.007 and I missed the e vs a part.
Bothered (Score:2)
IANA astro-physicist - but something bothers me about the big bang theory (or at least what I know about it). Why just one? Why aren't we able to detect other big bangs elsewhere? And another thing - we theorise based on what we are able to measure and observe. While we seem to have a theory that fits the data available, surely it is quite possible that our data are just unique to our locality. Seems like we are looking into someone's CA backyard and trying to say something about volcanic action in Iceland.
Re:Bothered (Score:4, Funny)
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well if you could somehow transport yourself to outside of this universe you might be able to observe the other big bangs.
hoooowever there's some significant problems with doing that. some people believe that if you jump from a bridge into concrete you get outside though(they base this on a lucid revelation given to someone else than them).
really though you don't need to be an astrophysicist to understand the basis for why your question sounds very misinformed. volcanic action in iceland is observable from
Re:Bothered (Score:5, Interesting)
That's a legitimate question, and in fact cosmologists are curious about the idea of whether the big bang is a unique event or something that can happen spontaneously. The hope is that advanced physics will provide some answers.
As for the "locality" issue: cosmologists address issues related to the entire observable universe. Speculations on regions that are unobservable aren't really a topic for scientific investigation, except where a good model implies certain (untestable) things about unobservable areas.
Re:Bothered (Score:4, Interesting)
In "eternal inflation," inflation is seen as something like the natural state of the universe, with little nodes from time to time budding off of the inflationary stream, and forming universes like our own, with inflation continuing elsewhere (from our standpoint, very very far away, much beyond any distance we could reach, even if we traveled at the speed of light). In such theories, the big bang is not the time of the birth of the universe, it is the time of the cession of inflation here, in our part of this bigger universe. This is one type of what Max Tegmark calls a Level I Multiverse (as there would be other "big bangs" elsewhere).
It may be that the recent detection of cosmic acceleration (aka "dark energy") indicates that our universe may (if the acceleration itself starts to accelerate into something like a "big rip") return to this natural state of inflation in due course, and that might be the typical fate of "normal" universes like ours.
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I was under the impression that the big bang needed conditions that would no longer exist in our post-bang universe (absence of time or something...), which would preclude further big bangs in our light cone. Although presumably they could still happen "outside" the universe?
Neutrino temperature (Score:5, Interesting)
The orginal article keeps quoting the temperature of 1.96K as the neutrino background temperature, as found in most textbooks on the topic. This is a relic of the time people were assuming massless neutrinos. The confusion is maintained by people using the temperature as a synonym of energy. Actually the non-zero rest mass energy must be subtracted, providing the real kinetic energy of these particles (moving now at 100-1000 km/s) that would be exchanged with a super large thermometer (in view of the tiny interaction cross section). The effective neutrino temperature would then be measured in the milliKelvin range.
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Has an actual lower bound been placed on neutrino masses?
Yes, on two of the three neutrinos because we have measurements of the difference in their masses. The lightest could still be pretty light, but knowing there has to be a certain difference between them means the other two can't be lighter than the difference.
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Sorry, but Scientology isn't a theory - at best it's a wacky hypothesis. A hypothesis must make definite useful predictions and withstand many and varied attempts to disprove it before it gets promoted to a theory (which is, roughly, synonymous with a scientific law)
As for the story changing - absolutely, that's called "learning", a concept you may be familiar with. I'd bet your own story as to where babies come from, or what women want (or men,as appropriate) has changed considerably since you first aske
Not quite (Score:5, Interesting)
No, not quite. These neutrinos also interact gravitationally with ordinary matter, which, of course, the author knows, but just doesn't think of. That introduces two possible means of detecting them, either gravitationally [arxiv.org], or by using the Sun or other bodies to focus them [arxiv.org] on a detector, thereby greatly amplifying their signal.
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The thing is gravitational interactions are so minute as to be useless (for now) for detecting individual neutrinos in a laboratory environment - the sort of situation which lets you conclusively state the things actually exist and aren't just a flawed theoretical construct used to help explain things we see halfway across the observable universe.
The focussing thing sounds like it has promise though, though I wonder just how much good focussing something so far beneath our current detection thresholds can d
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I misspoke, that should have been "for detecting individual slow neutrinos"
For measuring the neutrino mass perhaps - but is anything directly related to detecting slow neutrinos from the cosmic neutrino background radiation? My impression was that detecting such neutrinos is still well outside our current abilities, the energies involved are just too small.
It still does not answer the biggest question... (Score:4, Funny)
Will Sheldon finally find a way to communicate with Penny?
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E = M C2
That's about all there is to it.
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Re:ROFL (Score:5, Insightful)
" the Big Bang still thrives as the most successful scientific model of the Universe ever constructed."
Really? Then give us proof where all of that matter came from so the big bang could happen. If it already existed to allow the big bang to occur, then where did it come from before that?
A degree in cosmology takes years of study and research. A degree in cosmetology can be obtained in six months. Your girlfriend will laugh and ridicule your opinions in cosmetology, but you feel fully qualified to comment on the current questions being studied in cosmology.
Re: ROFL (Score:2)
Well played. I'll have to remember that response.
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Your girlfriend will laugh and ridicule your opinions in cosmetology
Guys with degrees in cosmetology don't have girlfriends, no matter how many chicks you see them hanging out with.
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Nobody knows. Although we know that it was there, and it was in a hot dense state.
Note that "nobody knows" does not mean "whatever pet theory you have is right".
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Go watch Primer [wikipedia.org] a couple times and then come back and see if you still want to ask that question.
I suspect why everyone gets pissed at this question--assuming it's not just a knee-jerk anti-creationism reaction--is that the question doesn't really "mean" anything. It's like asking someone, "Who was phone?" There's at least one model [wikipedia.org] that posits that ball or some version of the universe has "always been there."
Plus, isn't talking about "before the big bang" paradoxical since time itself technically didn't ex
Origin of mass-energy (Score:2)
You're obviously trolling, but what the hell:
One of the current theories with some traction is that inflationary energy was self-replicating, capable of "separating" flat space into more inflationary energy and the corresponding gravitational well (negative energy potential), for net zero change in total energy. The inflationary energy then later decayed into what we today call mass and energy.
That is to suggest that the entire universe contains a net mass-energy of approximately zero - all positive mass-e
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My understanding of the Big Bang Theory, from Hawking's books, is that the theory doesn't try to address what came before the big bang. Or what set it in motion. How how this something came from nothing or if there was a "nothing."
All it attempts to explain is, once it starts, how does it proceed?
Quantum fluctuations (Score:2)
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They are, have been, and ever shall be.
We know that today various so-called "virtual particles" spontaneously pop into existence for a brief moment before annihilating with the antiparticle that spawned along with them - the theory stands up and we can measure their effects in the lab. And there's no reason to assume the same thing hasn't been happening throughout eternity.
And I mean actual eternity - not just the paltry 14 billion years since the big bang. For all eternity virtual particles could have be
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It was probably turtles.
It not only accounting for phenomena (Score:2)
... but it be good too!
Obvious troll is obvious (Score:2)
Come on, DICE: If you're going to troll us with articles, at least try to make it a bit more subtle. This one basically reads as "Evolution is best science EVARRRR!!"
It not only accounting for phenomena
Glad to see the editors we know and love are still living up to the high standards we set for them, too.
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The most successful scientific model is found in Genesis chapter 1. It begins with the creation of light.
Well, yes. That's what the Big Bang Theory is in a nutshell, and it was after all originally developed by Georges Lemaitre, a Belgian Catholic Priest.
It's notable that all of the planet's major religions endorse the BBT and consider it to not be at odds with their faith including Christianity, Islam, Hinduism, Buddhism, & Judaism.
Actually, a really nice article... (Score:3)
That was really lovely, and thank you for posting it.
You assert that one problem with detection is the difficulty of accelerating entire neutrino detectors to GeV energy scales. I'm not sure that I agree. Muons, as we know, decay into electrons and two kinds of neutrino/antineutrino. Electrons moving at GeV scales have more than enough energy to be transformed into muons in the inverse reaction -- if they happen to hit an electron antineutrino -- or more properly, they have a chance to be transformed into a W- boson which can then decay into several things -- lepton/neutrino pairs or quark pairs, one of which produces muons
Muons are easy to detect. Electrons with "suddenly" shifted energy are also easy to detect (another possible outcome). Finally, quark-antiquark "jets" are easy to detect.
At the densities of thermal neutrinos asserted, it seems reasonably probable (without, admittedly, doing the computation) that GeV scale electrons will encounter free neutrinos and undergo the inverse reaction and produce muons along a freely moving beam track and indeed that places like SLAC and the Duke FEL would be producing a small but detectable flux of muons all along the straight legs of their beams that would then either exit sideways (where they could be detected lots of ways) or continue along the collision frame of reference and be moderately separable at the next bending magnet. Yes, there would likely be some auxiliary production near the actual beam from electron collisions with beam pipe metal outside of the beam envelope, but one would expect to be able to put a vacuum pipe along the frame of reference of the collision a kilometer long or thereabouts PAST a a bending magnet (at the right angle) at the end of a long straight leg and run it into a detector, which would then detect all/mostly muons produced by neutrino scattering. Or so it seems.
Is this wrong?
rgb
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I think you are overestimating the scattering cross section of even GeV neutrinos. An electron neutrino with 10 GeV in the rest frame of an electron has a scattering cross section of about 2e-44 m^2. There are about 112 electron neutrinos per cm^3, so the (lab frame) scattering rate is about 2e-44 m^2 * c *112/cm^3 = 6.7e-28/s per electron. The number of protons per beam in LHC is about 1e14. Assuming the number of electrons per beam in SLAC etc. is roughly the same, we get about 1e-13/s scatterings total i
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Thanks, you are probably right -- as I said, I wasn't doing the math, but was just thinking that an accelerated beam IS a rapidly moving detector. I was also assuming that it was the lack of collision frame energy in the huge neutrino detectors that was the limiting factor in detecting thermal neutrinos -- to create a W boson requires order of 100 GeV, and of course this just isn't available (outside of Heisenberg uncertainty and extremely suppressed virtual processes) which mutually thermal atoms and neut
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Yes, the accelerated beam is a rapidly moving detector. My point is that it is a rapidly moving detector with a woefully tiny volume. I'm no expert on this - I used this page [cupp.oulu.fi] for neutrino cross sections. Both inelastic and elastic scattering seems to be proportional to collision energy.
Neutrinos of several PeV/c^2 are regularly observed in neutrino observatories. At these energies, the Earth is able to act as a somewhat effective neutrino shield, resulting in a significant deficiency in high-enery (>60 T [arxiv.org]
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Interesting article. Things really do get complicated at those energy scales...:-)
They're using Cerenkov detectors, though, for very very high energy events. I wonder how sensitive they are to muons with much lower energies. The scales on the figures in the article, for example, don't actually go down to 100 GeV -- the left hand edge (log scale) appears to be 1 TeV. But the cross sections are indeed pretty small and it is difficult to get rates to rise above the background cosmic ray muon flux (which I
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The scales on the figures in the article, for example, don't actually go down to 100 GeV -- the left hand edge (log scale) appears to be 1 TeV.
Sorry, my third link was to the wrong article. It should have been this one [arxiv.org]. That's the one that covers the whole energy range, and which shows the magnitude and location of the W-boson resonance.
SLAC is apparently capable of generating 1/2 an ampere of beam current. That's basically 10^19 electrons/second, which knocks five orders of magnitude off your estimate of 1 event per 300000 years to one per 3 years.
Wow, I was off by a lot! I don't know how noisy environments accelerators are, but I think one would need many times more events per year to be able to detect this. It would be really nice.. But I'm skeptical.
That seems as though it is low enough that IF there were any sort of actual resonance, it might knock another order of magnitude off and get one at least several events per year, maybe more.
From the figure on page 3 in the article, it seems like the W resonance is at 6 PeV/c^2 for a stationary ne
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Unless I've missed something crucial here. But perhaps we'll have a breaktrough in accelerator technology that will let us reach these levels at some point. If we hit the resonance, the scattering rate will be of the order 1e-31, 13 orders of magnitude higher than what I used in my back-of-the-envelope calculation. But we aren't likely to hit those energies soon, I think.
Oops (blush). I haven't done relativistic kinematics for a very long while either, but I forgot about momentum conservation altogether.
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Oops, I mistakenly used the same link twice. The last link was supposed to be this:
http://arxiv.org/pdf/1305.7513v1 [arxiv.org]
It is well worth a look through.