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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."
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.
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."
Black holes are the brightest objects in the universe. As far as we know nothing escapes the event horizon, but plenty of things get thrown out at very high energy from the accretion disk.
Not a sentence!
It would not be possible to detect gravity waves (or anything else) from a source inside a black hole. Here we are talking about gravity waves created when two black holes interact.
Imagine to non-black holes - say neutron stars colliding (boom!). As they collide the gravitational field around them varies rapidly ( changes from 2 sources to a single source). Those variations send "ripples' (gravity waves) through space. The ripples aren't just from inside of the neutron stars, but from the fields which extend outside. If you now collide black holes, the same thing happens, gravity (and curvature of space) near the black holes changes radically as they collide and some of that is emitted as gravity waves.
The above is of course a hand-wave. The *real* answer is that you can simulate the Einstein field equations as the black holes collide, and they show the radiation of gravitational wave.
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.