Enlarge (credit: NASA)
A key feature of scientific theories is that they make successful predictions, which we can use to determine whether they’re likely to be right.

For general relativity, one of its key predictions had to wait for an eclipse of the Sun. Relativity predicted that the mass of the Sun should distort space enough to bend the light arriving from distant stars. We needed an eclipse in order to be able to see the stars, rather than ending up blinded by pointing telescopes toward the Sun.
That historic eclipse was front page news nearly a century ago. Now, researchers have managed to repeat the experiment, but upped the degree of difficulty considerably by tracking the distortion of space produced by a white dwarf over 18 light years away. Not only was relativity confirmed yet again, but the result cleared up a potentially awkward possibility, namely that the star was older than the Universe itself.
Twisted space
An optical lens works because light takes different paths through a material.

According to relativity, space itself is distorted by the presence of large masses, and these distortions can also cause light to take different paths between their origin and Earth.

This gravitational lensing has turned into a powerful tool in astronomy. Researchers have used it to magnify distant objects and to identify concentrations of dark matter by the distortions they produce.

The temporary brightening gravitational lensing produces has even been used to identify a handful of planets.
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