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Big Bang's Smoking Gun Found
astroengine writes "For the first time, scientists have found direct evidence of the expansion of the universe, a previously theoretical event that took place a fraction of a second after the Big Bang explosion nearly 14 billion years ago. The clue is encoded in the primordial cosmic microwave background radiation that continues to spread through space to this day. Scientists found and measured a key polarization, or orientation, of the microwaves caused by gravitational waves, which are miniature ripples in the fabric of space. Gravitational waves, proposed by Albert Einstein's General Theory of Relativity nearly 100 years ago but never before proven, are believed to have originated in the Big Bang explosion and then been amplified by the universe's inflation. 'Detecting this signal is one of the most important goals in cosmology today,' lead researcher John Kovac, with the Harvard-Smithsonian Center for Astrophysics, said in a statement."
Pretty damn cool.
My hat's off too all the hard-working, dedicated cosmetologists that made this possible.
A direct detection of a gravitational wave moving the mirrors of a large scale interferometer is up next. In the next few years, Advanced LIGO (US), Advanced Virgo (Italy) and KAGRA (Japan) will come online with the hope of directly detecting gravitational waves from sources such as supernovae and coalescing binary star systems. With this kind of network, it will then be possible to coordinate both electromagnetic and gravitational searches of our sky. This is useful for many reasons, one of which is that it lets us listen to the sound of black holes colliding where no light escapes.
Exciting times!
Einstein's theories continue to astound.
We already have plenty of direct evidence for the expansion of the universe. See redshifting of galaxies etc.
This announcement is about inflation - a particular period of rapid expansion immediately after the big bang.
There are three problems in cosmology that inflation solves: flatness: the universe is very close to its critical density, the horizon problem: the universe looks like it is in thermal equilibrium for no good reason, and absence of magnetic monopoles.
Note that this the second indirect evidence for the existence of gravitational waves, the first one was the orbital decay of a binary system that included a pulsar, discovered by Hulse and Taylor (Nobel Prize 1993). Today's result, if confirmed, seems pretty spectacular, and might be rewarded with a second Nobel Prize. For a first direct detection of gravitational waves, we have to wait for first detections by LIGO, Virgo and eLISA.
karma police: arrest this man, he talks in maths; he buzzes like a fridge, he's like a detuned radio. [radiohead]
Some interesting perspective from Matt Strassler, who's a particle physicist at Harvard.
He points out that this is still an *indirect* observation of gravitational waves (and not the first one) and that the results look sensibly in line with some predictions from inflation. And that while this is a tremendous experiment, it's not any kind of "smoking gun", and we really need to wait for replication to get properly excited.
All opinions expressed herein are not my own; I haven't had free will since last year when aliens ate my brain.
I think you have it wrong. You see, these creationists...they have a book which describes exactly how the world was created. It is called the Bible and it states pretty clearly how it happened. The problem here is that this so called "evidence" contradicts the very strong evidence they have...namely, their book.
Since it contradicts their book by claiming to take billions of years, it must (by very definition) be wrong. So what you really have is the Big bang is a bad interpretation of the natural world.
Now excuse my while I go wash my hands for typing that.
"I opened my eyes, and everything went dark again"
Gravitational waves are a prediction of general relativity and not related to gravitons (assuming that's what you meant) that are theorized to be the carrier of gravity in quantum gravity theories.
"Give me six lines of C++ code written by the most competent programmer, and I will find enough in there to hang him."
Perhaps if the Bible said '7 units of time' then there wouldn't be such a big emotional fuss over such a meaningless argument.
Technically, you're there, since the "first inch of expansion" contains the entire universe... literally.
This was the old news...
Basically sifting through information gathered from older CMB detectors, they discovered a statistical B-mode in the data that could have come from gravitational wave that occurred during inflation, but the data was really too noisy to be sure.
The new news is they used a new detectors which are capable of making cleaner measurements to convince themselves that the detected B-mode was unlikely to come from gravitational lensing after the big-bang. The current evidence apparently is consistent with the B-mode coming from a gravitational waves that are predicted to occur during the inflationary period of the universe.
Remarkably, the oldest baryons in the* universe are in your head.
* From your reference frame. And only by a nanosecond or so.
I met a guy from Sri Lanka once who had the best comment yet on "Prayer in schools":
"I am perfectly ok with prayer in schools, and I would encourage it but it seems a bit impractical if they don't already have an altar to catch the blood."
"I opened my eyes, and everything went dark again"
I don't know why you need to go arguing about all these fancy foreign words; if English was good enough for Jesus then it should be good enough for us to understand his teachings. You think if he wanted us using Hebrew words, he would have written the bible in it.
"I opened my eyes, and everything went dark again"
"A viable alternate theory is that light gives up some energy while traveling extremely long distances, which shows up as red-shift. Where does the energy go? It could be the source of energy for the CMBR. It could go somewhere else. In any case, as a theory, it explains the red-shift just as well as expansion."
Excellent! Now repeat the rest of the predictions of the Lambda CDM model. Ah, no, you'll have trouble with that one.
"Another viable alternate theory is that the absorption/emission spectra of atoms differs with space/time. Perhaps atoms farther away or longer ago created and absorbed light at lower frequencies, this making older light appear red-shifted by current frequency comparisons. This theory is even harder to test, but just as good at explaining the observations. "
Even better! Now repeat the rest of the predictions of the Lambda CDM model. I think you'll have problems with that one, too.
Actually, I'll give you a bye -- all I want to see is the position of the first peak on the CMB *and* the wavelength of the oscillations in the large-scale structure, with one predicted consistently from the other. Once you've done that, if you can further get out supernovae 1a redshift/distance plots I'll give you extra credit, but since the progentiors aren't fully understood I'll give you a bye on that one, too.
See, the word "viable" has certain caveats. It has to satisfy the observations it's been built to explain *at least* as well as the theory it's replacing. Second, it has to -- self-consistently -- predict further observations that fit *at least* as well as the theory it's replacing. I'm no fan of Lambda CDM but its successes should convince anyone who's actually looked seriously at them that there's something close to reality there, even if ultimately it's a phenomenology close to reality (which it is; I can prove it's phenomenology -- rigorously -- but I can't demonstrate how wrong it actually is, and neither can anyone else at present, but I can at least assert that up until very recent times it's so close as to be indistinguishable and no that I fit all observations, and even very recently it's exceedingly good).
Did you hear that? That was the sound of millions of religious zealots pressing their palms harder against their ears and screaming LA LA LA even louder.
I'll bite. I'm sure you'd consider me a "religious zealot." I believe in God. I believe in the Bible for what it is---a religious text that has suffered at the hands of multiple translations, compilations, and shenanigans, but that still has managed to retain the essential doctrines of man's relationship to God. It is not, and was never intended to be, a scientific text. The account in Genesis merely says that in six "days" (the original Hebrew word means "time periods") God instructed that the earth should be created, and that this creation was carried out through some unspecified agency. I don't believe God has thrown in CMB and dinosaur bones to deceive us, because I believe that he is a God of truth. My faith certainly doesn't drive me to deny science, because science is (or at least should be) ultimately a search for truth, and all truth brings us closer to the God of truth. The Bible is an excellent spiritual resource that has enhanced my relationship with God, but it tells me very little about physics, engineering, and biology.
So please tell me how your faith---which I assume dictates that the universe is a convenient sequence of coincidences, each individually of staggering improbability, and all of them taken together forming something at least as incomprehensible as the most convoluted beliefs about God---is inherently more reasonable than my faith, which is that there is a creative genius operating in all the majesty of creation.
Today's Sesame Street was brought to you by the number e.
"if I'm allowed to make stuff up whenever I want to make my theory fit the model, I can do at least as well as the Lambda CDM"
Go ahead - you're more than welcome to. Empty assertions don't show much but new cosmological models are welcomed. *I* welcome them, anyway; I've never liked Lambda CDM much and it's obviously a phenomenological model. But they have to be predictive, and founded on firm principles.
I didn't actually want to suggest you're an idiot because I think it's apparent you're not, but this type of post at the same time implies that *cosmologists* are idiots and brainwashed into a model that doesn't really make much sense. And in some cases that's actually true -- there are more and more cosmologists trained into cosmology rather than general relativity and it's a bit dangerous -- but on the whole I don't think many people *like* LCDM. There are too many unanswered questions in it, and everyone is looking to answer those. Just some people work more tightly within its framework than others.
"is there a point where you would ever consider reexamining the questions of the assumptions? Why haven't we reached that point yet?"
Oh, don't misunderstand me -- I *constantly* question and re-examine the assumptions. At some point, if you're genuinely interested, flip back through my posts on Slashdot; I've made my position I think fairly clearly. Boiling it down and putting it in bullet form it goes something like this:
* The "big bang theory", and Lambda CDM in particular, is an astonishingly successful theory, particularly when attached to an inflationary period in the early universe or something that mimics its observational results closely
* The successes of Lambda CDM -- such as the predicted abundances from Big Bang nucleosynthesis, the *prediction* of the angular power spectra of the CMB (temperature auto-correlation, temperature/E mode cross correlation, E mode polarisation auto-correlation and now the B mode polarisation auto-correlation) from a simple early primordial power spectrum, the direct mapping between the wavelength of the sound horizon at last scattering as seen on the CMB and that same wavelength imprinted on large-scale structure and *observed* as the baryon acoustic oscillations, and their ilk -- are far too numerous and significant to be ignored.
* Any alternative absolutely has to preserve these, and they're all extremely sensitive
* Lambda CDM is wrong. It is dead wrong. It is wrong in principle. It is questionable from a particle physics perspective, particularly where it comes to dark energy, but far more importantly, it cannot be justified with general relativity.
Lambda CDM rests on a few main assumptions:
* The universe is on average isotropic around the Earth. OK, fine, we can't argue that; the CMB is proof enough.
* Since the Earth is nowhere special, the universe is on average isotropic around every point: homogeneous. Well, this is debatable since the Earth *is* in a particular position, but on the whole this is probably at least approximately true.
* Gravity is best described on large scales (ie > mm) by a metric theory. This is currently practically unquestionable; metric-based theories of gravity are vastly more succesful than any alternative.
* Gravity is described by general relativity. OK, now we're entering questionable territory but GR remains our best example of a metric-based theory and is yet to be seriously challenged (though there are many, myself among them, who point out that the appearance of dark matter on galactic scales, and the addition of dark energy on cosmological scales, may very well imply that actually we cannot apply gravity on such scales or else that it simply doesn't act this way on large scales)
* GR can be applied directly on large scales. This is extraordinarily shaky. Actually, it's unjustifiable. We've got two main objections here: firstly, there is no reason to assume that gravity actually obeys GR on large s
Thank you for sharing your perspective like a gentleman. I respect that.
I think the core of our disagreement is with your expectation that all the things explained by LCDM must be explained by other theories. I believe it's perfectly fine for the answer to be that some things aren't connected. If we no longer assume we know the age of the universe, then predictions of element ratios no longer need to agree with observations of CMB, which may be totally disconnected from galaxy supercluster clumpiness. If red shift is seen to have some cause other than just expansion, then no unified theory has to predict how the universe got from a near-singularity to the observed state. Once you take a fixed finite timeline out of the picture, there can be different causes for different phenomena.
-Jaborandy
(Last post from me on this thread.)