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Special effect image of spaceships flying through outer space with the Earth visible in the background on the right. Fotopic/ Miles Simons/Newscom. Find it at Newscom.com: pttmedical007916
If you’re a science fiction nerd like me and have ever read any of the sequels to Ender’s Game by Orson Scott Card, then you know it tells the story of a man who is nearly 3,000 years old. No, he isn’t a science experiment gone wrong. Instead his body has been kept young by his time spent traveling at close to the speed of light. Its a crazy anti-aging regimen, and even though the book is fiction the idea of aging slower when traveling at high speeds is a real physical concept that is described by Einstein’s Theory of Special Relativity.
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Einstein, Albert Physicist, Ulm 14.3.1879-Princeton (N.J.) 18.4. 1955. Portrait photograph, 1895. akg-images/Newscom. Find it at Newscom.com: akgphotos007040.
We all know at least a couple things about Einstein. His equation, e=mc^2, is probably the most famous equation out there. His wild hair is legendary. And his theories about the nature of the universe brought a major paradigm shift not just to physics, but to many other disciplines. And it all started with a little something called Special Relativity. In order to understand why Special Relativity was such a big deal, we have to understand reference frames and one simple, easy equation.
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Passengers on airplane. ColorBlind Images/Blend Images/Blend Images LLC/Newscom. Find it at Newscom.com: biphotos001931
The concept of reference frames isn’t too difficult to understand. Imagine that you decide to take a vacation to Hawaii. In order to get there, you have to fly. So you pack your sunscreen, hop onto an airplane, it takes off, and soon you are on your way to the dream getaway. This is where reference frames come into play. To you, everything inside the plane, ie your frame of reference, is behaving normally. You could get up and walk around, play catch with the guy across the aisle, basically anything goes as long as you don’t act like a terrorist. But what do you look like to an observer on the ground? From their reference frame you are booking it across the sky at 500 miles per hour, even though you yourself have no concept of the motion from within your own reference frame. That’s the basic concept of reference frames- things moving at different velocities will have different reference frames. Pretty easy right?
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Speed limit 55 sign with traffic on the interstate in Idaho. David R. Frazier / DanitaDelimont.com “Danita Delimont Photography”/Newscom. Find it at Newscom.com: ddpphotos266959
Now for the math. I understand most people balk at anything that remotely resembles an equation, but this one is super simple and we use it every day. If you’re driving down a freeway where the speed limit is 65 mph, how do you figure out how far you will have traveled in ten minutes? You multiply 10 by 65 of course! And that is all the math you need in order to understand very basic Special Relativity. The explicit equation is distance = velocity x time, or d=vt for simplicity’s sake.
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A Police Officer measuring speed with a Laser Gun. Christian Prandl Image Broker/Newscom. Find it at Newscom.com: ibpremium181733
In order to explain what reference frames and d=vt have to do with each other, lets go back to the airplane scenario. Pretend that for some reason you thought it would be awesome to pack a speed gun in your carry on and that you didn’t get arrested by the TSA for doing so. (After all, it does have the word “gun” in the name, so it must be dangerous.) And also imagine that the observer on the ground has a speed gun as well. Now say one of the flight towers on the runway decides to shoot off a light beam in the direction opposite your plane is moving, and both you and the observer on the ground measure its speed with your respective speed guns. What do you expect to find?
To the ground observer, the light should be traveling at 3 x 10^8 meters per second- the recognized speed of light you will find in any textbook. No worries there. But think of how the light looks in your airplane reference frame. Because you are moving away from the beam of light your, own speed should add to what you measure the speed of light to be. Basically, in the d=vt equation you would expect that different reference frames measure different velocities for light. But this just simply isn’t the case in actual experiments.
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Einstein, Albert; physicist; 1879-1955. Work: Relativity Theory.-Manuscript by Einstein “�ber die Relativit�tstheorie”, developed in Z�rich a.Prague 1912:Einstein’s Relativity Formula.-Section from fol.39 recto. New York, Sotheby’s, 16th March 1996. akg-images/Newscom. Find it at Newscom.com: akgphotos159971.
This confounded physicists for a long time. How is it that the speed of light is the same for two reference frames moving at different velocities? And, finally, this is where Einstein came in with his revolutionary ideas we call Special Relativity. What Einstein did was say, “Ok. We know that in two separate reference frames the d=vt equation can’t be the same. So if v is the term that stays the same, that means both distance and time are experienced differently in different reference frames. And the faster a reference frame is traveling, the more pronounced the difference is.” Basically, any object that is moving experiences time slower and measures a shorter distance between point A and point B. This is called time dilation and length dilation.
The twin paradox is the classic thought experiment to show what time dilation is like. Imagine two twins, Jason and Rob. Jason is the adventurous type so he decides to take off in a space ship and tour the universe while traveling close to the speed of light. Rob, however, is content to stay at home with his wife and kids. 40 years go by on Earth, and finally Jason returns home. By this time Rob is something like 70 years old, but because Jason’s reference frame as been traveling extremely fast for the past 40 years (as experienced on Earth) he is still a young man thanks to the effects of time dilation.
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Vintage 1937 Buick Century car, Waterloo, Quebec, Canada. David Chapman / Design Pics/Newscom. Find it at Newscom.com: depvantage000705.
Length dilation is a little bit trickier to explain. Pretend that you are standing in a barn with two large doors right across from each other and 5 feet apart. You want to be able to fit a 10 foot car into this space. Sounds impossible right? Well, thanks to Special Relativity and length dilation it isn’t! All you would need to do was rig the doors to quickly open and close when you hit a button. Then you would have your friend drive the car at close to the speed of light. The length of the 10 foot car would decrease to the point where it could, indeed, instantaneously fit into the 5 foot barn. So basically if you want to store anything in a compact way, make it move at close to the speed of light!
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running time concept with rolling clocks. Ingram Publishing/Newscom. Find it at Newscom.com: ipurestockx123782
There are many other mind blowing and weird paradoxes associated with Special Relativity, and that is why it was one of my favorite things to learn about. Its eye opening to the know other people truly do experience fundamental things like time and distance differently than I might. And who knows what sort of crazy application for the future this theory might have? Only time will tell…depending on your reference frame of course.
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