Einstein’s theory of relativity incorporates two components: special relativity and general relativity.
Special relativity involves how the basic particles of the universe interact with one another. It describes what happens in the physical world, with the exception of gravity.
That’s where general relativity comes to help. It is an explanation of how gravitation laws relate to the other forces that occur in nature.
All realms are included in this theory, including cosmology, astrophysics, and astronomy.
Einstein’s Special Relativity Simplified
The theory of special relativity gives structure to the concept of time. It is based on two ideas that seem to be at odds with one another.
The first is that the laws of physics are the same for every observer who is in relative motion to one another. The second is that the speed of light, when placed in a vacuum environment, is the same for all observers, no matter what their relative motion may be or where the source of light originated.
Imagine that you’re sitting in a dark theater. You are on one side of it and someone else is on the other side. You’re sitting further away from the stage. The light then moves up and down, crossing back and forth across the stage.
Both you and the other person watching will see the light movement. Your perspective is different, but the laws regarding that movement remain the same.
Now if that theater were in outer space, the time it took for the light to reach you would be slightly longer than the other person, but the speed at which it reached both of you would be the same.
That is how distance is calculated spatially. If a star is 4 light years away, the total distance is the amount of time it takes light to travel the distance from its source to our planet.
Einstein’s General Relativity Simplified
The theory of general relativity describes how gravity affects the universe. When we take a walk outside, it is the gravity of the planet which keeps us from floating off into the sky. The surface of the Earth rotates at a speed that is roughly 1,000 miles per hour at the equator, but because of gravity, we do not sense this motion.
At the same time, our planet orbits the sun at 67,000 miles per hour. We don’t feel that movement either. Because of gravity, we feel like we are still.
Yet, when there is no gravity present, the tendency of free fall is to move downward when no force is exerted on the inertial motion. That means gravity fields are present because of how the various physical objects in the universe interact with one another.
Because of this interaction that gravity has on physical objects, changes occur to the elemental structures of the universe. A clock, if it were placed into a gravity well, would run slower than a clock outside of that gravity well.
Rays of light can be bent when there is a gravitational field present. If a large enough gravitational mass were to rotate, it could drag the structures of space and time from the theory of special relativity with them.
What Does This Mean for the Universe?
The theory of relativity lets us see how gravity interacts with what we perceive to be the physical world. When there are changes to gravity, the structure of time can be altered. This effect has been studied in astronauts as they age slower. It’s also why if you wear a watch on your ankle, it will be slower than one on your wrist eventually.
The effects, however, are small compared to the larger effects of the universe. If you live in a basement, your aging would only be a fraction of a second slower than those on a mountain.
On a larger scale, what it means is that the universe is expanding faster than light can travel at its outer components. That means there are secrets waiting there in the vastness waiting to be discovered because the speed of light, which is a fixed rate, hasn’t been able to fully penetrate the expansive area.
To summarize: relativity involves laws of physics that do not change, even if there is constant movement. Special relativity involves the physical components, while general relativity involves gravity.
When put together, we discover that space and time are unified. Although your observations may be different than someone else, both observations are valid, even when made in real-time.