Gravity Waves vs Gravitational Waves

bicep2

The tell-tale twisting pattern in the polarization of light from the CMB, caused by the ripple of gravitational waves a tiny fraction of a second after our Universe came into existence.

 

Today I would just like to clear something up in case any of you were confused by some of the media coverage of yesterday’s thrilling result from the BICEP2 experiment. The result appears to show the fingerprints of gravitational waves imprinted on the cosmic microwave background (CMB) radiation. However, many news sources (including The Guardian and CNN) reported this as the first observational evidence for gravity waves.

Now this might just sound like astronomer nit-picking but I can assure you there is a big difference. Gravitational waves are ripples in spacetime that were first predicted by Einstein in 1916, as part of his theory of general relativity, but have never been directly detected. Whereas gravity waves are waves in a fluid for which gravity is the restoring force. For example, the waves caused on the surface of water by wind. We’ve known about them for some time, and you can detect them easily every time you go to the beach! Now you can go and impress your friends by telling them the difference 🙂

Anyway, yesterday’s results are a huge step forward in our understanding of our Universe and they show the origins of the largest structures we know about today; like the ones you can find at www.galaxyzoo.org