Big news hit the space-geek scene on Monday, when an astronomy team announced the first direct, physical evidence supporting cosmic inflation theory. And if that sentence fried your brain, try this one:
The Big Bang, which until now was just an elegant hypothesis of how our universe came into existence, has just been kicked across the goal line.
Of course, the results must be replicated for this discovery to be confirmed, but still, this is a hugely big deal. As in, Nobel Prize big. But it’s also really tough physics to explain, and I can attest to that personally because after reading the first article about it, I said, “Huh?” After the second article I said, “Okay, yeah, but…huh?” After the fifth article I felt I had a pretty decent layperson’s grasp of it, which is all any of us who aren’t physicists can expect.
The Big Bang hypothesis (known professionally as cosmic inflation theory) says that way back in the beginning, the entire universe as we know it was packed into a tiny point less than the size of a single atom. Then it went kaboom. Starting a fraction of a second after that kaboom, and lasting for only another fraction of a second, the universe expanded so rapidly that it left the speed of light in the dust. This was the inflation period, a technical name for an event of brain-melting magnitude. In a time period so small that I hardly have enough zeroes to express it, the universe expanded at a rate so unthinkably fast that there are hardly enough zeroes to express that, either.
Phil Plait tried:
Some models show it increased in size by a factor of 10 to the power of 50 (some say even more)—that’s 10 trillion trillion trillion trillion times bigger, all in a time frame so small that analogies fail me.
Later that day he came up with an analogy, which is short and worth a read.
So how do we find evidence of something that started, and ended, in much much much much less than a single second of time?
We look for swirlies.
If inflation happened, then the rapid expansion would create gravitational waves, which are ripples in space-time. The waves would not be directly observable, at least by any tools we’ve yet conceived of, but their effect on light would be.
Now, we already know gravitational waves exist, and have already found evidence of them (which was another Nobel Prize event), but finding such evidence specifically from the inflation period was a whole different ballgame. The inflation model predicted that gravitational waves would polarize light in the exploding universe in a very specific way, called B-mode polarization. (For a great explanation of the concept of polarized light, go here and scroll down to the image of the picket fence.) This B-mode would curve the direction of polarization into a swirly pattern. And to find it, astronomers would have to look at the cosmic background radiation — the light left over from the birth of the universe. As you can imagine, this light is really, really faint and hard to detect, so the team of astronomers searching for swirlies went to the best place on Earth to look for ultra-faint light: the South Pole.
And they found what they were looking for. In fact, they found more than they were looking for. The B-mode polarization signal they detected was so unexpectedly strong that they spent three years analyzing the data to be absolutely certain they hadn’t screwed something up before making their announcement. According to the official Harvard press release:
“This has been like looking for a needle in a haystack, but instead we found a crowbar,” said co-leader Clem Pryke (University of Minnesota).
Here is what they saw:
The black lines show the direction of polarization, and they are clearly outlining…swirlies. To put it in the parlance of a detective novel, this is a smoking gun. These are gravitational waves in the light from the birth of the universe. They prove that gravitational waves did indeed exist during the inflation period, that infinitesimal fraction of a second when the universe was expanding faster than the speed of light.
As of now, the scientific field of cosmology has been turned on its collective head. Not only that, but this data ties together quantum mechanics and general relativity, two separate fields of study that everyone just knew ought to fit together, but nobody could prove it.
For me, the best part of the whole story is the human impact. Stanford University released a video of one of the Principal Investigators of this study, Chao-Lin Kuo, making a surprise visit to the home of physicist Andrei Linde, who is called “the founding father” of cosmic inflation theory. He knocks on the door and says, without any prelude, “So I have a surprise for you. It’s five sigma, at 0.2.”
Here’s the layperson translation: “So I have a surprise for you. You know that theory that you never thought you’d see proven in your lifetime? We have evidence of it, and the probability that our data is not merely from random chance is about a billion percent.”
Okay, so the billion percent might be an exaggeration. But five sigma is a way of expressing probability, and the number quoted here — 0.2 — takes it far past “probable” and straight into the category of “confirmed discovery.” In fact, that’s what Renata Kallosh, a professor of physics and Linde’s wife, says in response. “Discovery?” she asks in shock.
“Yes,” replies Chao-Lin.
What a wonderful day in the life.
(Video hat tip to Paulo.)