By Shayan Ali Nassabi, Erfan Alireza and Sam Majidi.
A theory that changed the way we view the universe forever. The theory of relativity. A scientific discovery that was introduced to us almost a decade ago but is still the root of countless experiments and astronomical observations. A theory that debunks many of Isaac Newton’s claims about physics. The theory of relativity. You might be wondering what this ‘theory of relativity’ is all about by now.
How has it changed everything?
What is so special about it? To really understand what it’s all about, let’s take a look back in history to see how it all began.
A 16 year old Einstein was conducted a thought experiment where he rode on a ray of light while observing another ray of light moving parallel to him. On the basis of classical physics, it can be said that the ray of light that Einstein was looking at has a relative speed of 0. However this contradicts Maxwell’s equations that state that light always travels at the same speed of 186,000 miles per second. Another great issue with this is that it goes against the laws of electromagnetism, which also contradicts the rules of classic physics which said the laws of physics are the same for everyone.
This sparked something new in Einstein’s brain, which he called the ‘Special theory of relativity’.
The theory of relativity is split into two parts: "special" theory of relativity and "general" theory of relativity.
The first applies to frames of reference (vantage points) which are in constant, unchanging motion, while the latter applies to frames that are accelerating with regards to each other. With regards to the special theory of relativity, Einstein concluded that events that might be simultaneous for one observer may not be for another. He also added that time flows differently according to the state of motion, and concluded that distance is also relative. All that might sound a bit too complicated at first so let’s take a look at an example of where it might be applied, from Einstein. Imagine a person standing next to a moving train, comparing observations with a person sitting inside the train. The train is at a point where it is equidistant from two trees. If a bolt of lighting strikes both of the trees at the same time, the person standing still would see both of the strikes occurring simultaneously, whereas the person in the train (due to the motion of the train) would see one strike take place before the other. This example greatly simplifies one of the biggest theories of physics- the special theory of relativity.
E = MC^2
Now let’s talk about the formula. The formula that pops up into everyone’s minds when they start thinking about Einstein, E = MC^2. To break it down, it means that energy (E) is equal to mass (M) times the speed of light (C) squared.
This means that mass and energy are interchangeable.
It also leads to the idea that as the speed of an object increases, so does its mass. Sorry sci-fi fans, but this means that instantly warping through space in a supersonic ship might not be possible. The speed of light is the fastest velocity at which an object can travel in vacuum. At least theoretically. The problem is that as an object approaches the speed of light, its mass increases simultaneously to the point where it equals to infinity.
If an object has a mass of infinity, then it will require infinite energy for it to move.
Let’s take the equation of kinetic energy: energy = 0.5 times mass times velocity squared. Hence, if the mass is infinity, so is the energy. Achieving this might be impossible. The reason why light is able to travel this fast is because photons (the things that light is made of) have a mass of 0. Before Einstein’s theories, it was believed that light needs to travel through a medium. Due to this, people claimed that in space, light travels through a substance called luminiferous aether. However, it has now been proven that light does not require a medium for transmission, and that it can travel through vacuum.
Space-Time
The theory of special relativity also tells us that space and time are linked. Einstein referred to this phenomenon as space-time. He believed that space and time are connected for objects that are moving at a constant speed, and together it forms space-time. This is also related to how time is related to motion.
For example, if a 15 year old astronaut travels at almost the speed of light for 5 years (from his perspective), he would be 20 years old after the trip, whereas his classmates would be around 65 years old.
This shows that time moves slower for a moving object compared to a non moving object. This can really be observed with objects moving at extremely fast speeds, like the example mentioned earlier. It also tells us that time travel is real, so hold on tight sci-fi fans.
Gravity and Bending light
Gravity was once considered only a force, but Einstein’s theories and space-time prove that claim wrong. Instead, he claimed that gravity exists due to large masses in space. Imagine a trampoline, with a heavy ball placed in its centre. The heavy ball creates a dimple which makes anything else around it on the trampoline move towards it. That is how gravity works in space; it is a consequence of the curvature of space-time caused by the uneven distribution of masses. Gravity is also responsible for another great scientific phenomenon- gravitational lensing.
If a ray of light travels close to a large mass (like a star) then the gravitational force of the star can lead to the bending of the ray of light.
This is called gravitational lensing. Einstein claimed that no matter how strong the gravitational effect is in an area, it will affect light as well. This was quite difficult to experiment with at the time so many scientists disagreed with Einstein’s claim. However, in 1919, scientists did get a chance to test the theory during a very long eclipse. And, as expected, the results proved his theory to be correct. It has also withstood further experiments that have been conducted overtime.
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Well there you have it. The theory of relativity. A breakthrough in science. This is of course not the entirety of the theory, but is a mere brief of what it is mainly about. Einstein’s work has impacted us dramatically in almost all fields of science. If it weren’t for him, we would still think that there is some invisible substance in space that allows light waves to travel, or that gravity is just a force that exists as it is. Nature truly is quite complicated if you try to understand it very closely and observe, like Einstein did. Who knows, there might be another Einstein coming up that comes up with even more ideas and theories that change our lives.
You can never predict what’s coming. You can only wait and see how history unfolds.
Written by Shayan Ali Nassabi
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