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kottke.org posts about Einstein

Gravity is the new light

posted by Tim Carmody   Jun 16, 2016

Gravitational waves from two colliding black holes were first detected last September and announced in February. This week, the same science team announced a second wave detection of two smaller black holes in December.

If the first one confirmed the long-held predictions of general relativity, the new detections are a signal to get started on some all-new science.

A black hole’s gravity is so strong that even light can’t escape, so black holes are essentially impossible to see with telescopes. But they do give off gravitational waves.

“Light’s always been how we do astronomy,” Professor Jo Dunkley, an astrophysicist at Oxford University who didn’t work on the experiment, told BuzzFeed News. “Everything we know about space, we’ve got from light. This can show the stuff you can’t see with light.”

Counting black holes, combining telescope with gravitational measurements to better understand neutron stars, all the usual origin-of-the-universe stuff.

If gravitational waves don’t require cataclysmic collisions between enormous black holes for us to measure them, but can be detected on the regular, we can use them to try to figure out a whole lot more than just whether or not Einstein was totally right. That is a very nice tool to have in your pocket.

We Work Remotely

Einstein was right. Again.

posted by Tim Carmody   May 05, 2011
Spacetime.jpg

NASA’s just finished an impressive experiment designed to test Einstein’s general theory of relativity — specifically the “mass distorts spacetime” part:

Put a spinning gyroscope into orbit around the Earth, with the spin axis pointed toward some distant star as a fixed reference point. Free from external forces, the gyroscope’s axis should continue pointing at the star—forever. But if space is twisted, the direction of the gyroscope’s axis should drift over time. By noting this change in direction relative to the star, the twists of space-time could be measured.

Gravity Probe B’s experiment was 47 years in the making, helped spawn 100 PhD theses, and required the invention of 13 brand-new technologies, including a “drag-free satellite.” The four gyroscopes in GP-B are “the most perfect spheres ever made by humans… If the gyroscopes weren’t so spherical, their spin axes would wobble even without the effects of relativity.”

NASA finished collecting the data in 2005; now they’ve crunched the numbers. And yes, Einstein was right. The gyroscopes wobble in just the way general relativity predicts.

The first and most famous empirical experiment testing Einstein’s theory was performed in 1919 by Arthur Eddington during a full solar eclipse. Photographs showed that the sun’s mass caused starlight to bend around it.

(Image by James Overduin, Pancho Eekels, and Bob Kahn via NASA.)