What is Relativity? Time to ask

At the speed of light, time stops, mass becomes infinite and distances become zero

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Relative to what?

An hour long lecture feels like an hour, an hour long videogame session feels like a minute. That’s relativity. That’s it, bye!

Just kidding. Relativity, as the name suggests, is the idea that change in something you’re observing is always relative to something else. 2 hours is a lot of time to take a shower, but not enough time to take a flight from say, China to Germany. The sufficiency of the time is relative to the task. Usain bolt runs pretty fast relative to a snail, but really slow relative to a car. If you choose a snail as the “frame of reference,” your reference is almost static compared to Bolt, but if you pick the car as your frame, it’s way faster than the guy and thus, Bolt’s speed is lower in comparison. So we have always understood relativity.

Here’s a meme about relativity.

In fact, Isaac Newton’s laws of physics accounted for relativity as well. Speed was always measured relative to something else, a train’s travelling speed is measured relative to Earth which itself is an object moving at a very high speed, we can also measure the same train’s speed relative to a bird flying over the train or another train travelling adjacent to it. The rotation of Earth is measured relative to our galaxy, which itself is moving. The point is, we perceive any movement in space, relative to something else.

Getting Einstein into the picture

But that’s not it. It can’t be that simple. We just told you about simple relativity; something humans, animals and birds understand and have understood for centuries. What about all that beautiful Einstein shit that blows people’s minds.

That’s where the twist comes in the story:

Remember that we just said that every movement is measured relative to something else. Well, there’s ONE exception to the rule. And no, it doesn’t involve Einstein … yet.

James Maxwell is the person who discovered that light’s speed is the same no matter how you measure it, travelling at the speed of sound might make you perceive a plane also travelling at the speed of sound as static or immobile, but you will always perceive light’s speed to be the same, precisely 299,792,458 m/s. It doesn’t matter whether you’re viewing this light while standing, running or flying at the speed of sound. Light literally doesn’t care about how you look at it.

Ok … we can bring Einstein to the party now. See, we just gave you two opposite facts. Everything travelling in space is relative to something else, but light completely defies this rule. Why? If that confuses you, you’re feeling the same confusion Albert Einstein once felt. The only difference is that you can just read up the answer in this article rather than obsessing over it like him, which is part of why he understood these concepts so well.

Anyway, Einstein was faced with a question: why do two people who are at different speeds themselves perceive light’s speed to be the same? This would either mean that Newton’s laws were wrong or the speed of light was not constant. So Einstein proposed “time-dilation,” an advancement to Newton’s laws that broadened the application of relativity. We normally think that time always passes at the same rate; if you call an astronaut in a space ship travelling at a very high speed and asked them the time, they’ll you the same time that’s on your watch in your room. The fact that this guy is travelling really fast and you’re sitting in your chair has no effect on how the two of you observe time.

            But that’s not true.

It is time to redefine time

In fact, if that guy in the space ship was travelling at extremely high speeds, they would tell you a very time. Their clock would be ticking much slower and if he left 30 days ago, hardly a few seconds would’ve passed on the clock they were carrying. This is due to time dilation. It’s not a very complicated concept. We already explained how Usain Bolt feels faster to a snail and slower to a car – similarly, this guy is travelling at Usain Bolt speed but this time, you’re the snail. You’re the one who feels like a lot of time has passed and he’s the one who feels that very little time has passed. This was shown in the movie, “Interstellar” as well; by the time you come back after 2 hours on a planet that’s moving extremely fast, several years have passed on Earth and many people you knew are now old or deceased.

Essentially, Einstein had simply proposed that just like speed is relative, time is also relative. He didn’t refute Newton’s laws, he added another layer of explanation on top of those laws.

This theory of time dilation is called the special theory of relativity. It also has a formula; you can see it. The formula simply says that the faster you travel, the slower you experience time. Your current speed v, divided by a much higher speed of light c, is a value between 0 and 1. When you subtract it from 1, you get a value that is also between 0 and 1; and it stays smaller between 0 and 1 when you take a squared root of it. So your current time gets divided by a value smaller than 1, in the denominator and as a result, your answer t’ is higher than your current time t. It simply means that if you were travelling with a very high speed and your friend was at rest at v=0, your friend would feel like a year has passed while you would’ve felt like a few seconds had passed – just like movies. You can also see that if your speed is equal that of light, the change in time or t’ is infinite. Time literally stops when you travel at the speed of light; you could go around the universe doing anything you want at the speed of light and you could experience billions and billions of years without aging one bit.

But time isn’t the only thing that changes relative to speed. Mass changes relative to speed as well. It works just like time dilation. The faster you go, the heavier you get. You actually weigh a bit more when you’re travelling really fast.

Similarly, the perception of length or distance changes with speed as well, but it works opposite to mass and time. The faster you go, the shorter distances appear to you. You will find the distance between two places to be much smaller when you’re travelling really fast.

It's time to discuss the speed of light

You can already see from these formulas that at the speed of light, time stops for you, your mass becomes infinite and your distances become zero – this means that you can be present everywhere at the same time – you can be omnipresent. But all of this raises a big question: what if you exceed the speed of light. All of these formulas fail at speeds greater than that of light. They give you imaginary values that are not possible in reality.

And that brings us to the elephant in the room. I can already feel some of you thinking, “wHaT soRtA eQuaTioN iS diX? I wAnTeD e=mC^2.” Well, here it is.

E = mc^2

You’re probably familiar with E=mc^2. You can clearly that the simple equation states that everything with a mass has an energy E, and a small amount of mass can have a very large amount of energy because it’s multiplied by c^2, an relatively large value (pun intended). Just 500 grams, which is roughly the weight of your smart phone, can create enough heat to destroy an entire city if taken to the speed of light. This is what happens in an atomic bomb. It converts a small amount of mass into extremely large amounts of energy that causes catastrophes. And this is how Einstein solved the absurdity of what would happen if something exceeded the speed of light. The equation for mass dilation told you that mass increases with speed. E=mc^2 tells you that it can’t exceed the speed of light because as soon as it hits the speed of light, all of it gets converted into energy and energy travels at the speed of light.

            That’s how the special theory of relativity works.

  • Speed is relative to a frame of reference (eg. a slowly moving snail) – we’ve always known this
  • Time, mass and distance are relative to speed
  • Speed of light is the highest speed a particle can have

If you read through the article and reached here, we have a surprise for you: It is possible to go over the speed of light. It happens all over the universe in something called “quantum entanglement” that involves quantum particles interacting at speeds faster than the speed of light. We’d offer to explain this to you but it’s a bit … well … how do I put it, weirdass shit. Anyway, if you want to know more about it, let us know in the comments.

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I'm a Mechanical Engineer, and an entrepreneur. I believe that science and engineering is a way of communicating with nature and reality. Unfortunately, our education system fails to incite 'intrigue' and 'curiosity,' we are flooded with information we don't understand. I write to educate students and to help them love the reality around them.

5 Responses

  1. I liked tour expalination.
    Can you elaborate on these?
    What do you mean by experiencing time? How it feels like experiencing time slower? Can it be faster than normal time?

    1. There is no such thing as “normal time.” Everything is relative to something else; and time is relative to speed. What you’re calling “normal time” is time observed on Earth on slow speeds. At even slower speeds, yes, time is faster. This means that if you were on a planet moving slower than Earth, you will age much faster. At higher speeds, time is slower. If you were in a really fast rocket, you will age slower.

  2. I would like to know more about quantum entanglement.
    Usama, I love that you write to educate students and you appreciate the value of intrigue and curiosity.
    I believe all mass, has an energy which on a molecular and subatomic level is moving at different rates, different speeds and these orbits of electrons and general movement, when colliding, when causing interference, create quantum entanglement and this is how matter is created. I have had a theory for some time, that everything is light – the effects or aftermath – essentially light. If you go deep enough in the matrix of a rock, you find lava and then deeper, you find light. Light is captured as it refracts and collides and bursts into fractals the shapes of which depend on what seed or crystal or element it has come into contact with and this works on a microscopic level as well and across distances, creating patterns in space matter as well. Over time light resonates into the form of matter. The more time involved depending on the integrity and properties of the element, the harder the matter is. This is so rudimentary and I do not claim to be cracking a code of the universe, I am just fascinated by phenomenon. I have studied a bit in the area of the history of science. I am not a scientist and I’m sure I sound like I am spouting sudo-science, but it is very fun to talk about and visualize.

    1. Thank you for the compliment 🙂
      … You remind me of myself. I used to theorize about everything essentially being mass that got converted into forms of energy when the universe was created. Guess what? We’re both absolutely (ehm … relatively) right – and that brings us to mass-energy duality. The truth is that everything is simultaneously energy and mass, a topic for another day.

    2. Oh, and have a look at the mass dilation and time dilation formula. If you look close enough, you’ll see that these formulae also talk about your theory.

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