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When you write a science article for non-technical people, you have to choose your topics wisely. It has to be both interesting, and something that can be easily explained.
This week we’re going to tackle a topic that’s somewhat difficult, but is incredibly interesting; special relativity.
While special relativity was discovered by Albert Einstein in 1905, the idea of relativity has been a fundamental part of Physics for hundreds of years.
The idea is simple, certain measurements are only meaningful when you describe it relative to something else. Location is an example. Being 5 miles North by itself doesn’t make any sense, but being 5 miles North of Arrowhead Stadium does.
In this case “Arrowhead Stadium” is what’s called a reference point. Basically just the point from which you’re measuring from.
Velocity is another measure that’s relative, although this is a bit more counterintuitive, but makes sense when you think about it. Right now I’m sitting in my office writing this and not moving. But I actually am moving, because I’m on Earth and the Earth is going around the Sun.
So it depends what your reference point is. If your reference is the Earth, I’m not moving. But if your reference is the Sun, I am.
Since velocity is relative, like location, it doesn’t make sense by itself. It only makes sense relative to something else.
Keep that in mind.
The 1800’s were a boon for Physics, at least for what’s now called classical Physics (which is refers to the ideas that existed before Einstein blew everything up). In particular the equations describing electricity and magnetism were being discovered.
But as they were discovering these equations a problem arose. They found that these equations used the speed of light as a variable (which is denoted by “c”). But according to relativity there is no “the” speed of light, it depends on your reference point (which is actually called a reference frame in special relativity).
Think about it, imagine you’re in space and there’s a particle of light (called a photon) in front of you headed away from you, and you’re following it at half the speed of light. The from your frame, the speed of light is half of what it would be for somebody else standing on the sidelines.
An early idea was that there was an ether that filled the universe that provided a universal reference frame, but this idea had all sorts of problems.
But then Einstein came along and had an idea that’d be pretty stupid if it didn’t turn out to be right. Einstein said “What if these equations were right, and the speed of light is not relative, but the speed of everything else is?”
Think back to our two guys looking at that particle of light (a.k.a. the photon). One guy is standing still and says it’s moving away from him at 300,000 miles per second, and the other guy is also saying it’s moving away from him at 300,00 miles per second.
The second guy who’s moving is going to be 150,000 miles away from the first guy who’s standing still after one second, yet according to Einstein that photon will be 300,000 miles away from both of them at the same time.
That means that if Einstein wants the speed of light to be the same for everybody, then distances have to be relative. Two people who are moving at different speeds won’t agree on how far away stuff is from each other!
It’s crazy! It’s ridiculous! But it’s 100% correct.
But it doesn’t stop there. It turns out time is also relative. That means that if you go fast enough it’s possible to travel thousands of years into the future after just a couple years.
Brian May, the lead guitarist for Queen, has a PhD in Physics and actually wrote a song about this phenomenon.
You can see why the old way of thinking is called classical. This, combined with quantum mechanics (which Einstein also was a major contributor to) changed Physics forever. Everything that came before is just an approximation.