An international team of researchers using data from a radio telescope at the South Pole recently announced they had found the first evidence of gravitational waves created during the birth of the universe, also known as primordial gravitational waves. Dr. Joe Jones, associate professor of physics at the University of North Georgia, explains what the waves are and how their discovery may impact science.
What are gravitational waves, and how are they created?
Einstein's General Theory of Relativity (GR) is currently the best description of gravity that we know. In GR, the universe is described as a four-dimensional space-time, and the effects of gravity are mediated by how mass and/or energy curves or "warps" this space-time fabric. Einstein's equations predict that if a region of mass or energy is accelerating it can produce a "ripple" in space-time that propagates away at the speed of light, the fastest any effect can propagate through space-time.
Why has it taken so much time for researchers to find direct evidence of the primordial waves?
Direct detection of gravity waves remains elusive, and the many gravity wave observatories around the world continue to refine their instrumentation in hopes to be the first to directly detect a passing gravity wave.
The observations of the BICEP2 (Background Imaging of Cosmic Extragalactic Polarization 2) microwave radio telescope at the South Pole has provided direct evidence of the effects of primordial gravitational waves generated by a period of extreme expansion of space-time, theorized to have occurred during the first fraction of a femtosecond of time. Strictly speaking, it did not directly detect gravity waves. The evidence itself is a pattern of polarization, impressed on slight variations in the Cosmic Microwave Background (CMB). These variations in the CMB have only become directly detectable over the last 10 to 15 years, but their detection and analysis has revolutionized our knowledge of the universe. The more subtle patterns of polarization promise to push the frontiers of cosmology even closer to the beginning of time.
How will knowledge of the waves and their behavior impact sciences such as astrophysics and others?
Up until now, our observations "outward," such as in the CMB at the edge of the observable universe, and "inward," such as the discovery of the Higgs boson particle, have pushed our knowledge beyond the first few seconds of time. These new observations involving primordial gravitational waves should allow scientists to glimpse the universe during its first 10-36 second of existence.