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Gravity Probe B

Testing Einstein's Universe

Special & General Relativity Questions and Answers

What can you learn from studying gravity waves?

Gravity waves can travel through things that block ordinary light and even neutrinos because gravity waves are so weak. They interact 10^42 times less strongly than electromagnetic radiation, and 10^35 times less strongly than neutrinos. This is an advantage in two areas of astrophysics:

The cores of stars about to go supernova are opaque to neutrinos, and gravity wave signals can be used to probe the details of the last few seconds of the supernova implosion of the core to a neutron star of black hole.

The universe was opaque to neutrinos about 1 microsecond after the Big Bang, and cosmological gravitational radiation ought to be present that could tell us what the Big Bang was like during its first microsecond. Currently, the famous cosmic background radiation discovered in the early 1960's and studied by the NASA/COBE satellite can only give us a view back to 300,000 years after the Big Bang because at earlier times, the universe was so dense and hot that it was opaque to electromagnetic radiation. Astronomers would like to know if there were any black holes forming or evaporating during this very ancient time, and just how smooth the universe was after the first second.

In principle, a study of gravity waves could tell us some of this, but they are so weak we have to go to great lengths just to detect them from nearby supernovae!

Return to the Special & General Relativity Questions and Answers page.

All answers are provided by Dr. Sten Odenwald (Raytheon STX) for the NASA Astronomy Cafe, part of the NASA Education and Public Outreach program.