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Testing General Relativity

Everyone seems to want to take shot at discrediting Einstein and his theories. I used to volunteer to answer questions for an Ask an Astrophysicist service, and nearly every week I would get a question or two that started with, “I have a new theory…” And at least half of those “new theories” were trying to take down Einstein.

Here’s the deal about general relativity and Einstein: over the past 100 years armchair physicists aren’t the only ones who have tried to poke holes in Einstein’s theories. But no one has succeeded.

Einstein proposed three tests of his own tests of general relativity when he first published it in 1915: the precession of Mercury’s orbit, the bending of starlight near the Sun, and the gravitational redshift of light. These represented just the beginning of a long list of tests which could be performed to bolster the case for GR.

There are a number of other tests, from the existence of black holes to gravitational lensing. Every major prediction of general relativity that can be tested with current technology has been tested. And every one of those predictions has been proven correct. For 100 years.

We are not done testing general relativity, either. If you are a regular NASA Blueshift reader, you should have seen Ira Thorpe’s post last week, Doing Astronomy With Our Eyes Closed where he talked about gravitational waves, which are one consequence of Einstein’s theories. We know that gravitational waves exist through indirect measurements, but we have yet to observe them directly. Read Ira’s post to see how scientists are going to do that.

Curious about other tests of general relativity over the past century? The timeline below gives some of the big ones. It is by no means all of the tests that have been done, but shows that no one is simply taking Einstein at his word.

General Relativity Timeline

Tests of general relativity (GR) require strong gravity, massive objects and/or high-precision measurements—conditions we don’t readily find on Earth. This timeline below shows a sampling of tests which have confirmed GR’s predictions over the past century, with a preference for astronomical tests. Credit: NASA

Want to learn more about what GR is and why it’s important in your life? Read my post on the 100 years of GR from earlier this week.

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