13.7: Cosmos And Culture
Tue March 18, 2014
A New Window On The Big Bang Has Been Opened
Originally published on Tue March 18, 2014 10:49 am
It's not every day that a new window on the birth of the universe is thrown open. It's not every day that human beings get the chance to leap into the void and have their conceptions of space and time stretched to the limits. It's not every day that we see the wildest dreams of scientists realized, written into the fabric of space and time and light.
Today appears to be one of those days.
The Big Bang has been the dominant theory explaining the history of the universe for more than a half-century. But puzzles inherent in the idea (and in the data) led to a major addition to the theory in the 1980s: inflationary cosmology. Since then inflation, as it is called, has been a sometimes contentious but stalwart pillar of our cosmic understanding. To get inflation on solid scientific ground however meant finding ways to see farther back in time than ever before.
And that is what has been announced today.
To understand the importance of today's discovery (Nobel worthy?) you are going to have to think small ... very, very small. You must wrap your mind around the most tiny, itsy-bitsy, sliver-o-licious, hyper-minuscule fraction of a second you have ever considered in your whole life.
Try saying this out loud: One hundred million, billion, billion, billion-th of a second after the moment of creation.
That's what we are talking about. That's what the kind folks at BICEP2 may have given us (it will need to be confirmed, of course).
It is an indirect view of the universe at approximately one hundred million, billion, billion, billion-th of a second after it was born. Written mathematically, that is 10-35 of a second or a decimal point with 34 zeros after it, which looks like this:
T = 0.00000000000000000000000000000000001 second
For comparison, when it you mistakenly grab a hot tea kettle it takes a full 0.01 second for the electrical signal screaming "DROP IT!" to run from your hand to your brain.
We are talking about a very, very, very young universe.
Which finally brings us back to the importance of today's monumental discovery. In the 1980s, Big Bang theory got a major upgrade with the addition of inflation. Back then paradoxes and puzzles kept popping up which threatened to topple the Big Bang. Scientists like Alan Guth realized that, in order to make the idea work, there must have been a brief moment very early in cosmic history when a little sliver of post-Big Bang space-time began expanding much faster than its surroundings. Like an inflating balloon blown up by a high-powered compressor, this tiny "pocket" of space-time stretched very, very quickly to become our entire observable universe.
But almost as rapidly as it began, this period of inflation ended and left us with what we have now: the leisurely expansion we see today. In spite of its brevity, this brief period of Inflation was all-important. It was inflation that set us on the trajectory for everything that has happened afterward: galaxies, stars, planets and us.
But inflation was a contentious idea from start. No one had a firm handle on what the universe was like at such a ridiculously early point in time. The densities and temperatures of cosmic matter were so high that its physics could only be drawn in outlines. While inflation cured many problems for cosmologists, it seemed to lots of researchers like wishful thinking written in advanced math.
Where was the proof?
Over the last few decades a slim kind of proof for inflation arrived via tiny bumps and lumps in the ancient cosmic gas that can be directly observed through what's called the Cosmic Microwave Background (CMB) radiation. The CMB is made of fossil photons left over from the period just 300,000 years after the Big Bang. Lumps and bumps in the density of gas can be traced all the way back to quantum mechanical burps that occurred during inflation. But there are many versions of inflation theory and the proof that came from the density wiggles did not tell us which version was correct or provide many details about the early, early universe. In other words the density wiggles were a blunt instrument.
Space-time wiggles, though, are another story entirely.
The violence of the early universe was so extreme that it would leave space-time itself ringing like a bell. Almost as soon as inflation was proposed some scientists predicted that it would leave a "gravity wave" signature.
Ripples in the fabric of space-time are an essential prediction of Einstein's theory of relativity. While we have never captured a gravity wave directly, we already have indirect proof of their existence by watching how pairs of orbiting pulsars (dead hyper-dense stars) spiral around each other.
Thus more than two decades ago physicists were predicting the existence of a gravity wave signature for the inflationary epoch. Even more important, by looking at which gravity waves got the most energy scientists could cut through different versions of inflation theory. They could even tell if inflation itself was entirely wrong since there are alternative models for the early universe that don't involve inflation and make different predictions for the gravity wave spectrum.
So gravity waves are the key. If we could see them (directly or indirectly, as BICEP has done) they would represent a way to distinguish between different models for the early universe. And comparing data with models — that is what science is all about, after all.
Even on its own, finding new evidence for Einstein's much-sought-after gravity waves is a major achievement. But finding evidence for them from the early universe means we have a new tool for exploring the most extreme, mind-blowing event that ever occurred: the birth of everything. Today it seems that evidence may have been found.