The “Big Bang” has been trending on social media this week. For a medium obsessed with tracking real-time events, a 13+ billion year-old celestial happening is pretty over, am I right? But it turns out that all the chatter was the result of an exciting scientific discovery that’s giving us insight into the earliest moments of the universe.
I tried to grasp the science behind this story, I really did, but then I got lazy and contacted a real-life astrophysicist named Katherine J Mack (AKA Katie Mack or @AstroKatie on Twitter) to spell out why this discovery is so huge.
We're hearing so much this week about a scientific breakthrough and how it relates to the big bang theory. How do you explain this week's discovery to a layperson like me?
The big bang theory is really just the theory that the early universe was hotter, denser, and smaller than it is today. Have you heard of the "primordial fireball?" (It wasn't necessarily actually a ball, but that's not really the point.)
The universe at the beginning was completely full of incredibly hot plasma, and then it expanded and cooled as it expanded. That's called the hot big bang. This new discovery relates to what happened just before the fireball stage, when the expansion started. We think the expansion was set in motion by a process called cosmic inflation, when the universe was expanding faster than the speed of light. When inflation ended, the universe was still expanding, but more slowly, constantly being slowed down a bit by the gravitational pull of everything inside the universe.
So what is a gravitational wave?
A gravitational wave is a ripple in spacetime -- it's basically travelling gravity. If you think about space and time as sort of woven together in a fabric, gravitational waves are like ripples in that fabric. Since Einstein first came up with his theory of gravity, we've thought that gravity probably travels in waves (and those waves travel at the speed of light). If the Sun were to suddenly disappear, the Earth would keep orbiting it until the disturbance in the gravitational field reached us -- about eight minutes later.
In space, we think gravitational waves are usually produced when big masses move around. We've seen evidence for them from the motions of super-dense stars called pulsars that are locked in tight orbits. But, during inflation, gravitational waves might have been produced by quantum mechanical fluctuations in gravity. All particles have a bit of uncertainty in their positions due to quantum mechanics -- a bit of fuzziness, you could say. If gravity can act as a wave and also as a particle (like light can), quantum fluctuations in the gravitational field could cause gravitational waves, and those would produce a characteristic light pattern in the afterglow of the primordial fireball. That's what we think we've just seen!
A bunch of people were sharing this video this week, showing scientis Andrei Linde being surprised with the news that confirms his years of theoretical work. it's so touching. What kind of rewards does one get for this kind of discovery?
Andrei Linde is one of the physicists who developed the idea of inflation, but he wasn't the first to propose it. That was Alan Guth, a physicist now at MIT. I wouldn't say this is necessarily a solid confirmation of the theory -- it still has to be tested by other experiments, and we have to figure out if inflation is the ONLY thing that could cause this signal -- but if inflation is confirmed, it's virtually certain someone will get a Nobel Prize. Guth is a prime candidate, but I'm not sure who else would be in the running. Many people (including Linde) tweaked and redeveloped the theory of inflation, and there's also the BICEP2 team, so it would be an interesting decision process.
What does this new discovery mean for science and study?
It means a lot for theoretical physics, if it's confirmed. It is strong support for the theory of inflation, which would give us a huge insight into how the early universe worked and what caused the expansion we see today.
It's also a glimpse at a MUCH earlier time in the universe's history than we've ever seen before. That primordial fireball time that I mentioned happened about 380,000 years after the big bang, and that's the earliest light we can see. These gravitational waves come from a time that was less than a billionth of a billionth of a billionth of a second after the big bang -- a major improvement!
What kind of research do you do? What does it mean for your line of work?
The work I do relates to a different mystery of the universe -- that of dark matter. We know that more than 80% of the matter in the universe -- the stuff that has gravity -- is totally invisible. It even passes right through us! But we don't know what it is, and I'm trying to figure that out by calculating how it would have affected the first stars and galaxies in the universe. This primordial gravitational wave stuff doesn't really affect that work of mine, but it's super exciting anyway. I couldn't sleep the night after the announcement came out -- it was just too big and exciting and potentially revolutionary to everything we know about the big bang!
Is there anything else we should know about this discovery? How are you geeking out on it?
This primordial gravitational wave signal (if it holds up) is a MUCH bigger signal than we ever dreamed it might be. We thought that we'd have to search for YEARS to get a hint of these waves, so we're all surprised that we might have seen them already. It really cuts down a lot of early universe theories that we thought would work just fine. And there'll be way more experiments looking for this signal and for other related signals in the next few years, so we should know more soon!
I've been geeking out on Twitter a lot (@AstroKatie
), and on Facebook
, and talking to all the physicists I know, and enthusing to all my friends. I've also done a bit of TV and I'm signed up to continue enthusing on the radio. It's a lot of fun. :-)