Big Bang's Smoking Gun Found 269
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."
Next up: a direct detection (Score:5, Interesting)
Exciting times!
Re:Next up: a direct detection (Score:5, Interesting)
It's not contradictory. The black holes will dump a metric giga-fuckton of energy as gravity waves before merging (it's science, so we have to use these new-fangled metric units). Once they merge, well, the established theory is that no energy could escape but that's being challenged more often these days. AFAIK, no one every actually detected Hawking radiation and everything predicted about black hole decay is untested, so having any detector that can observe a black hole merger will tell us a bunch!
Re:Creationists (Score:4, Interesting)
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."
Re:Don't Be So Cock-Sure You Know The Answer (Score:5, Interesting)
"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
Re:Don't Be So Cock-Sure You Know The Answer (Score:3, Interesting)
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.)