Scientists are developing a proposed technique to use gravitational waves to study the beginning of time. Gravitational waves might provide clues about the state of the very early universe that existed just after the Big Bang.
Massive object generate gravitational waves as “ripples” in the fabric of the universe as they move through spacetime. These waves provide clues about some of the most energetic and violent events in the cosmos like the fusing of two neutron stars.
These waves are typically difficult to detect by the time they reach Earth due to the distance of objects big enough to create detectable gravitational waves. Scientists currently use sensitive instruments like the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo interferometer to detect them.
They anticipate that more sensitive gravitational wave detectors will become available in the 2030s. Until then, scientists often use gamma rays as a proxy to observe events that can generate powerful gravitational waves.
The researchers behind the new technique for studying the early universe say that looking more closely at gravitational waves can provide a proxy for existing scientific instruments’ limited ability to observe the early universe. When gravitational waves interact with matter, they produce light with characteristics that depend on the matter’s density. This can produce clues about the properties of objects that are millions of light-years away.
“We can’t see the early universe directly, but maybe we can see it indirectly if we look at how gravitational waves from that time have affected matter and radiation that we can observe today,” said Deepen Garg, lead author of a paper reporting the results in the Journal of Cosmology and Astroparticle Physics.
Garg is a graduate student working with the Princeton Program in Plasma Physics, which is supported by the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL). He and his advisor, Ilya Dodin, adapted the new technique from Dodin’s work on fusion energy. The Department of Energy is sponsoring the work on fusion energy as a way to generate electricity without emitting greenhouse gases or producing long-lived radioactive waste.
While studying the ways that electromagnetic waves move through plasma, Garg noticed that they move in a way similar to gravitational waves.
“We basically put plasma wave machinery to work on a gravitational wave problem,” Garg said.
Complex? You bet. It started with the researchers expecting something that would be easy to solve and ended with them developing formulas to describe the new technique.
“I thought this would be a small, six-month project for a graduate student that would involve solving something simple,” Dodin admitted in a statement announcing the new technique. “But once we started digging deeper into the topic, we realized that very little was understood about the problem and we could do some very basic theory work here.”
Time might have been meaningless before the Big Bang. Everything was scrunched together in a space not much bigger than the head of a pin and the laws of physics as we know them now may not have applied. However, with this new technique, it might be possible to get a better idea of what went on when time was just getting started.