Most people think that time is constant. They think that time will tick at the same speed wherever they go in the universe. According to Albert Einstein, this is false. Einstein proved that gravity and acceleration are actually able to change the way in which time travels. For example, with the warping of time due to gravity, people who are on the space station are actually aging slower than everyone else on Earth! This is due to the idea of general relativity. 

 

In simple terms, the theory of general relativity is the basic idea that, instead of being an invisible force that attracts objects to one another, gravity is a curving or warping of space. The more massive an object, the more it warps the space around it. This is able to change the way in which time warps as well. To explain further, one needs to understand relativity and how time works.

To start off, one needs to understand the effects of gravity on objects. Gravity is the reason humans are stuck to the face of the Earth and it is the force preventing us from floating away into the abyss of space. Gravity isn’t something that just exists either. Gravity is formed by any massive object in the universe. For example, every planet makes its own gravity. The planet pulls space in towards itself, getting it to accelerate at ever increasing speeds. It also depends on the mass of the object. For example, a pencil will create its own gravitational field, but the gravitational pull will be so miniscule and small that it simply could not be detected with modern technology. On the other hand, the acceleration of gravity on the surface of the Earth (at sea level) is -9.8m/s/s. As one gets farther and farther from the center of mass of the object, the gravity decreases more and more. To put this in perspective, if one were to go to the beach and weigh themselves and then go weigh themselves on top of mount Everest, they would be slightly less heavy on the top of Everest. This is because they are farther from the center of gravity. It is also important to note that gravity only affects weight, not mass. Mass is how much matter something is composed of, and weight is how much gravity affects the mass.

 

The next concept is that acceleration and gravity are essentially the same thing. This is dubbed the equivalence principle. Consider someone weighing themselves on a scale at the beach and they weigh 80kg. Then consider someone in outer space riding a spaceship accelerating at 9.8m/s/s. (remember the acceleration of gravity at sea level is -9.8m/s/s) Would the person weigh the same amount on the spaceship in outer space as they would on Earth? The answer is yes, and only because the acceleration of the rocket matches the acceleration of the gravity on Earth. This proves that acceleration and gravity can act in replacement of one another.

 

Let’s relate these concepts to a physical example, like light in an elevator. If a person were to stand in an elevator and shine a laser at the wall opposing them parallel to the floor of the elevator, the laser and the laser’s point on the wall should be at the same height. Now let’s assume the elevator is accelerating upwards extremely fast. In this scenario, the laser and its corresponding mark would be at different heights. The mark on the wall of the elevator would actually be lower!

 

One of the common principles in the universe is that light will always take the straightest path, or the shortest path. In the stationary elevator, this path is straight across from the laser onto the wall. In the moving elevator, the path is not actually a straight line. This is confusing because physicists had always figured that the straight line was the shortest path. This idea can further be visualised by thinking about the fastest way to get from the north pole to the south pole. The true fastest way would be through the core of the Earth in a straight line, but that isn’t possible. Since humans cannot go through the core of the Earth, they go around the curve of the Earth. This is an example of how the shortest possible path isn’t always the straightest one. 

 

Time follows the same pattern as light does in this scenario. As the gravity warps the fabric of space around a massive body, time warps as well. To explain this, it is important to know that light has been proven to travel at the same speed in the presence of gravity and in the absence of gravity. Now remember that the shortest path for light to travel isn’t always a straight line. With this information we can use the formula for speed (s=d/t) to determine how time warps. Consider light traveling from point A to point B with a set distance. The speed of light is always constant, and the distance is fixed, so time equals distance divided by speed. Now consider light traveling from point C to point D but in a curved line due to gravity. The speed is constant, but the distance is longer than before. This means that the numerator is bigger than the previous equation. With a bigger numerator, this means that the time it takes for the light to travel the exact same distance is longer. Therefore time has just been warped.

To sum it all up: gravity affects the accelerations that the universe is subject to. The accelerations are responsible for the compression and decompression of space and that affects the distance at which light travels. Since light travels at a constant speed, the difference in distance outputs a change in time. That’s all there is to it!