# The Theories of Albert Einstein Explained

Have you ever found yourself in a conversation at a party, stuck talking about theoretical physics? Yeah, us too. If you need to sound smart in a flash, here are three of Einstein’s best theories condensed into party-friendly soundbites.

It’s Einstein Week at Gizmodo. But who is the man behind the mind? Genius, a 10-part drama series starring Geoffrey Rush, reveals the untold story of Albert Einstein from Monday April 24 on National Geographic.

## General Relativity

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Isaac Newton originally — in his First Law Of Motion — posited that an object will stay in uniform motion unless acted on by another force. That is: you’ll stay still (at rest) unless someone pushes you, or you’ll be constantly moving in a weightless environment unless some other force acts on you. Newton’s first law adequately explained the concept of inertia, which perplexed scientists until 1687. The issue with Newton’s first law was that it assumed gravity was a constant force at any point in space, rather than having less effect over increasing distances. The maths also didn’t work out as you got closer to the speed of light.

Einstein expanded upon Newton’s laws with his theory of special relativity, which maintained that Newton’s laws were broadly accurate, but only for any object being acted on in the same reference frame as the observer. In Einstein’s postulates, concepts that were thought of as constants — like gravity and mass — change as the observer’s frame of reference approaches the speed of light. There’s only one thing that’s constant between all reference frames: the speed of light.

Einstein landed on another paradox, however: if you’re free-falling, your body feels no force: only the Earth’s gravity pulling you down to the ground despite the fact that gravity is accelerating you — at a rate of 9.8 metres per second per second, if you want to impress your friends. If you’re not feeling a force, why do you travel faster? Einstein posited that Earth’s gravity was in fact warping space time around the moving body — meaning that light can do the same thing when acted upon by different forces.

## Gravitational Waves

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Gravitational waves are ripples in the universe caused by some of the most energetic cosmic events, from exploding stars to supermassive black hole mergers. Every object with mass creates gravitational waves. As they propagate through space and time, gravitational waves cause tiny tremors in atoms that make up matter — but we only really care when it comes to massively dense objects like stars and black holes, because that’s when we can detect them.

Einstein came up with this explanation for gravitational waves after his theory of general relativity, which explained that gravity exists as a result of the curvature of spacetime, and that spacetime curves when acted on by the mass of objects. Planets have gravity because planets are massive — get it? Because planets are massive — and stars moreso, and black holes even moreso again — we can measure their gravity by the effect that they have on the objects around them, but also on the effect that they have on light itself as it travels past.

While Einstein predicted them in his general theory of relativity in 1916, and their existence was indirectly demonstrated in the 1980s, it wasn’t until the LIGO detector came online in 2002 that the hunt for elusive spacetime ripples started to get serious. Gravitational waves explain what scientists refer to as gravitational lensing, where the light we observe from far-off galaxies and stars actually bends on its route to our eyes and telescopes, due to the extremely massive and gravitational presence of objects like black holes.

## Wormholes

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You’re damn right Einstein helped theorise wormholes! A wormhole is the idea that vast distances in space can be covered in an instantaneous — or at least very short — amount of time. Here’s where it gets even more complicated, though: wormholes can enable travel through time itself, too — remember how we were talking before about how Einstein connected space and time through his concepts of special and general relativity and that ol’ chestnut we call gravity? Yep, because everything is inextricably linked a wormhole could enable travel of a billion light-years in an instant, or through time by altering the speed of time itself.

Even though it’s been used as a bit of a get out of jail free card for schlocky sci-fi screenwriters over the years, a wormhole actually has a solid grounding in theoretical physics. The Einsteinian theory of gravity — actually the Einstein–Cartan–Sciama–Kibble theory, if you can rattle those off in a list — suggests that if two black holes of sufficient mass were to collapse in on themselves in, they could cause something called an Einstein–Rosen bridge to pop into existence between the two. That bridge could allow for instantaneous travel between those two points, no matter the distance between them, through a wormhole.

To learn more about Albert Einstein, check out the trailer for Genius below. Starring Geoffrey Rush, it tells the untold story of Albert Einstein. Premiering on April 24th on National Geographic.