This month marks 100 years since Albert Einstein came up with his theory of general relativity. And in honor of the scientific centennial, none other than David Tennant has teamed up with Einstein 100 to teach us what the hell it’s all about.

In 1905, Albert Einstein came up with his theory of special relativity, which introduced a new way to interpret motion between objects that are moving relative to each other. Through his research, he concluded that space and time must be interwoven into a single continuum, known as “space-time.” But there was a problem: the theory only held true in (wait for it) special circumstances, when the objects involved were moving at a constant speed. This stipulation didn’t meld well with what Sir Isaac Newton taught us about acceleration effects – most notably, the acceleration due to gravity.

So Uncle Albert went back to the drawing board, and spent the next ten years trying to figure out how to include accelerating objects in his calculations. The result was his theory of general relativity. Einstein concluded that gravity was not some innate force, but rather the result of warps in spacetime, caused by massive objects in the universe.

One of the ways this manifests is with so-called “gravitational lensing,” where light coming from behind a solid object can be viewed on the other side. Einstein’s theory predicts that something huge like a star cluster could bend spacetime with its enormous mass and gravitational field. That bend causes everything, even mass-less light to bend about the curve. A great example of this is the Hubble space smiley:

It’s a lot to take in if you’re not a physicist, and you might be surprised to find that many are still trying to find a better explanation for the way of the cosmos. But in the meantime, who better to break it down than a Time Lord?

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IMAGES: Einstein 100, BBC, NASA