Over Spring Break, physicists from the Harvard-Smithsonian Center for Astrophysics made an announcement that has been reverberating throughout the scientific community ever since. The discovery came from a small telescope known as BICEP2 located less than a mile from the geographic South Pole. From this location, scientists were able to glimpse much more than space through the telescope; they were able to see ripples formed at the very beginning of the universe.
Albert Einstein first theorized the existence of these ripples, known as gravitational waves, in his 1916 general theory of relativity. On March 17, however, it was announced that direct images of gravitational waves were detected for the first time.
Einstein’s general theory of relativity is currently our best model for gravity. It beautifully unites the dimensions of space and time, describing it as a fabric known as space-time that permeates throughout the cosmos.
General relativity describes the gravitational force as a curvature of space-time.
The more massive an object, the more the object warps the space-time surrounding it. Think of what happens to the fabric of a trampoline when someone stands in the middle. If you were to roll billiard balls around that person, they would ride along this curvature and begin to orbit like planets around a star.
Einstein’s equations of general relativity predict that large accelerations of mass in space-time create gravitational waves, not unlike the waves traveling through a bed sheet when you make your bed. For the most part, these waves are so absurdly small that they are nearly impossible to measure.
In the first fractions of a second after the big bang, however, the theory maintains that the universe accelerated so rapidly that the ripples that were sent through space-time then are still detectable now.
The effects of these primordial ripples are exactly what the BICEP2 telescope detected.
This period of incredible expansion at the beginning of the universe is known as inflation, and the gravitational waves detected from the early universe are the most compelling evidence of inflation theory to date.
I had the opportunity to talk with Bowdoin professor Thomas Baumgarte, of the physics and astronomy department, about the recent discovery. Baumgarte specializes in a field known as numerical relativity, where he uses computers to solve Einstein’s equations and to model astrophysical systems.
On the significance of the discovery Baumgarte said, “It’s the first time that the imprint of gravitational waves is measured in the cosmic microwave background and it’s also the firmest confirmation of the phase known as inflation.”
He went on to say, “It’s amazing that [we] can actually detect the effect of gravitational radiation from the first tiniest fractions of seconds of the beginning of the universe.”
Baumgarte is very familiar with gravitational waves due to the nature of his numerical relativity models. He has focused on modeling what the gravitational radiation would look like if two black holes or two massive stars known as neutron stars orbited each other in a binary system.
As for the reward for this incredible insight into the early inflationary universe, Baumgarte agreed that the Nobel committee will have quite a headache picking three out of the dozens of ingenious scientists behind this extraordinary discovery.