Albert Einstein is essentially the dictionary definition of a genius. His ideas still permeate the world of modern physics, providing our best known model of gravity and laying the foundations for numerous pieces of modern technology such as GPS. The wild-haired physicist is still such a famous name because he essentially revolutionised the world of physics, with such cognitive ability that his preserved brain has been studied by neurologists. He still generates this amount of fuss because his core contributions to physics not only accurately describe nature, but are absolutely mind-blowing.
Light is also a particle
The photoelectric effect puzzled physicists of the late nineteenth century. When a beam of light was fired at a zinc plate, it lost electrons – the light basically generating an electric current. The behaviour defied the school of thought that light was just an electromagnetic wave, and they were particularly confused by the fact that longer wavelengths produced the same effects, no matter how intensively they were applied,. Einstein explained this idea in 1905, writing a paper which explained that light was actually composed of particles (now known as “photons”). The energy of these particles rose in proportion to the frequency of the light wave, and a certain energy level is required to create the effect. This idea spawned the field of quantum mechanics, showing that light somehow behaves as both a particle and a wave simultaneously.
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Mass is just concentrated energy
The equation E=mc-squared is Einstein’s most well-known and least widely understood contribution to physics. What it actually shows is the special relationship between energy “E” and mass “m” (“c” is the speed of light) – or that mass (the “stuff” you are made of) is simply a concentrated form of energy. The big bang was therefore a cacophony of energy, so much so that it coalesced into matter and made everything in the entire universe. It also means, sadly, that smashing two atoms together can release a mind-boggling amount of energy – which is what happened at Hiroshima and Nagasaki.
Time is woven into space
Classical physics saw time as a separate entity, something that is continuous and reliable, unaffected by anything that happens in our realm. In his Special Theory of Relativity (from 1905 – the same year as the photon explanation), he linked the concepts of time and space, forming the fabric which underlies our reality – spacetime. This also means that time only exists with space, and it could consequently be argued that there was no time before the big bang. If you’ve always wondered what caused the big bang, some argue that nothing could possibly have caused it, because without time there is no such thing as causality, and without space there is no time.
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Time is relative
Einstein’s ideas about the relative nature of time mean some very unusual things are in fact true. Time actually changes depending on how fast you are moving and the distance you are from a gravitational source. So if one twin got on a spaceship flying at 99 percent of the speed of light for a full year, starting on his 30th birthday, he’d return at 31 whilst his twin (who’d remained on earth) would be 37. To test this, scientist got two atomic clocks (the most precise form available), set one on the earth and sent the other around the earth at 600 miles per hour on a jet plane. In line with Einstein’s predictions, the clocks showed different times – with the flying clock being a few billionths of a second behind the stationary one. In the same way, your head is younger than your feet, because it’s further from a gravitational source.
Only light has “absolute” motion
Consider this scenario: a train is approaching and you have to measure how fast it’s moving. If you know the length of the train, it’s simple. You measure how long it takes for the train to go past you, and you know that it covers its own length in that period of time, giving you a starting point for your calculations. However, if you were to move at half of the speed the of train in the same direction, it would take twice as long for the train to pass you. You might say that the train is still moving at the original speed and the slower speed is just relative to you, but it’s important to remember that the earth is moving around the sun at 67,000 miles per hour. Should you add that to the speed of the train too?
Einstein realised that all motion is relative to who is taking the measurement, except for the motion of light. If you could travel at light-speed (somehow), and raced a beam of light, the result would depend on who was watching. If there was a third observer, he would see you and the light arrive at the same time, but you would see the light zip past you and make it to the observer first. Light is the only thing we know of with “absolute” motion, so it doesn’t apparently slow down if you’re moving in the same direction like a train would.
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Gravity is Not a Force
Mass warps spacetime. The earth, a significantly massive object, sits on spacetime like a bowling ball in the centre of a trampoline. Just like the trampoline, spacetime gets warped by the massive object sitting on it. If you were to roll a smaller ball across the trampoline, it would either fall into the bowling ball or be flung out to the side because of the distorted surface. This is how the Theory of General Relativity describes gravity. It isn’t really a force in the same way electromagnetism is, it’s actually just the effect of being on a warped portion of spacetime.
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- Boscobel Area Schools: Einstein's Ideas
- Space: Einstein's Theory of General Relativity
- California Institute of Technology: Spacetime 101
- The Big View: Spacetime
- Walter Fendt: The Photoelectric Effect
- The Physics Hypertextbook: Photoelectric Effect
- The Big View: Time Dilation
- Einstein Jahr: Einstein's Legacy