Rumours swirl over credibility of big bang ripple find
newscientist.com
newscientist.com
People have tried for quite some time to measure them and so far no experiment has succeeded. On the other hand that's not surprising for such an elusive phenomenon, so the jury is still out.
There is literally no news content in this story. The story is "some guy says they did it wrong, BICEP says they did it right". It is not news that they used preliminary conference slides to subtract foregrounds, they have been open about that from the get-go. People are axious about the result, as it certainly will change when Planck drops their full dataset in October. It's likely that their measured value of r=0.20 will be lowered (although actually that can be cosmologically preferable). But I don't much expect that the difference will be large enough to invalidate their r=0 exclusion, which is the really ground-breaking result.
And by the way, scientists are human; they make mistakes. If that happens, then you can expect BICEP2 to retract their results. But until the _BICEP2_ team (not some guy who wan't involved with the analysis) makes a statement that they did something wrong, there's simply no news here.
[1] http://news.sciencemag.org/physics/2014/05/blockbuster-big-b...
It was news to me, though, to read that there is an asterisk of uncertainty about the BICEP2 result, because the original flurry of press lost that asterisk. ("5 sigma"!).
I happened to be talking with someone from the Planck team yesterday, and they mentioned the seriousness of these reservations. He was not pre-judging one way or the other, just saying it's not obvious at present how it's going to shake out.
Are there any theories of gravity that don't include gravity waves?
We are currently far, far away from that point. We're just at the beginning of a long, statistics-driven process.
If gravitational waves remain elusive, that would mean there is something profoundly wrong with the way we understand relativity. To be fair, there is arguably a lot about gravity which we don't yet understand - but gravitational waves are pretty much a required feature in many respects.
For example, without them our understanding of the orbital mechanics of massive objects would have to be revised. It would mean that massive bodies orbiting each other do not lose energy due to gravitational radiation.
> Are there any theories of gravity that don't include gravity waves?
Not any credible ones that I know of, maybe someone else can present one?
I guess I'm saying, if gravity waves conclusively didn't exist, how would information about gravity travel?
If early-universe gravitational waves aren't found, then some major theories of inflation and cosmology will require adaptation. In the grand scheme of things, this is still a big deal, but less-so than shattering a core prediction of GR.
BICEP2 is looking for B-mode polarization on large scales in the CMB because it is believed that gravity waves created in the early universe are the only possible source.
Before that revelation my expectations where that gravitational waves would be detected after the next supernova in the milky-way galaxy. That would require a lot less ingenuity.
I would take discovery by any method during my lifetime, in fact the less expected the better.
The energy loss rate from it and similar systems is in agreement with the gravitational wave predictions of General Relativity at the ~0.3% level or so.
The detection method by which BICEP has made its claim is somewhat indirect, too, as they see very weak distortions of CMB polarization made by the aftereffects of said waves.
Direct detection on earth is likely to come from a neutron-star binary merger. If we're lucky enough to get a local supernova in our lifetimes, it will be a huge deal for gravitational waves and many other branches of physics and cosmology. Our observational powers have increased by orders of magnitude since 1987A.