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Physics + Math

Physicists Detect Gravity Waves, Lifting the Veil on the Beginning of the Universe

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Cosmologists have detected gravitational waves in the cosmic microwave background radiation that echo from the beginning of the universe.

We now have a glimpse of what gravity looks like. And it’s giving us a direct look at the beginning of the universe.

This is perhaps the greatest discovery of the century. Cosmologists are deeming it Nobel Prize-worthy—as exciting and groundbreaking as the 2012 Higgs boson announcement, if not more so.

The finding comes out of the BICEP2 experiment, which has been measuring the polarization (or direction) of the photons that have been rushing toward our telescopes ever since the universe cooled enough to let light flow uninhibited.

This radiation is called the cosmic microwave background (CMB), and the ripples in its polarization are called gravitational waves—evidence that light was bent by the gravitational influence of massive objects accelerating through the fabric of spacetime. Ripples are predicted in Einstein’s general theory of relativity, but they’ve never been directly observed… until now.

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Here’s Adam Mann, writing for Wired Science :

What they detected is known as primordial B-mode polarization and is important for at least two reasons. It would be the first detection of gravitational waves, which are predicted to exist under Einstein’s theory of relativity but have never before been seen. But the thing that has scientists really excited is that it could provide the first direct evidence for a theorized event called inflation that caused the universe to exponentially grow just a fraction of a fraction of a second after it was born.

In other words, these warped photons could have come from a period of time in the universe’s infancy called inflation. Here’s Lisa Grossman, writing for New Scientist :

[Alan] Guth [of MIT] and his colleagues first proposed the idea of inflation in the 1980s to explain a wrinkle in the CMB: the temperature variations we see are too uniform for matter to have expanded slowly from a tiny point. Instead, they say, space-time ballooned in size by more than 20 orders of magnitude in a fraction of a second after the big bang. Then the expansion slowed to a more sedate pace.

And inflation should have stretched those first gravitational waves created during the Big Bang, “taking them from imperceptible wavelengths to a size we can detect in the CMB,” writes Grossman. And that’s what happened: BICEP saw them, and now other teams will surely hope to replicate and confirm the result within a few weeks, or a few years at the most. In the meantime, Tom Levenson takes a look at what this data means for us, cosmologically speaking:

At the very least: that we now understand in previously unattainable detail how our current habitat emerged from nothing (or better, “nothing”). That the idea of a multiverse — other patches of space time that underwent an inflationary episode to form island universes of their own — has now gained a boost (if one patch of space-time can inflate, so could others)….

…or to put in mythic terms: there is grandeur in this view of life (the cosmos). Paraphrasing an old friend, astronomer Sandra Faber, with this new, richer, more fully realized picture of the birth of the universe we have once again enriched that creation story that only science tells, the one that connects the earth we inhabit today with a process of cosmic evolution that we now can trace back all the way to just the barest instant this side of the point of origin.

A good day.

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Tweets of note:

The #BICEP2 discovery may 'go down as one of the greatest in the history of science' says @MIT physicist Max Tegmark: http://t.co/2OcmXQVZdG

— Curtis Brainard (@CBrainard) March 18, 2014

On the possibility of a multiverse:

Andrei Linde: “If inflation is there, then the multiverse is there.” Hard to build models that have inflation and no multiverse #BICEP2

— Lisa Grossman (@astrolisa) March 17, 2014

On the idea that quantum gravity might be a reality if BICEP data is confirmed :

. @tcross81 The gravitational radiation probably comes from quantum fluctuations in the gravitational field! Therefore quantum gravity!

— Katie Mack (@AstroKatie) March 17, 2014

More resources:

Dennis Overbye’s excellent report in The New York Times

Scientific American’s coverage , which has two long paragraphs detailing what BICEP2’s r value means and what it says about inflation

Some technical explanations from Sean Carroll , Liam McAllister , and Matt Strassler