The movie Interstellar explores wormholes and black holes and crosses the boundaries of time and space. But what does the movie have to say about Einstein’s theory of relativity? Let’s explore the core of relativity through the scientific concepts in the movie.
Interstellar is a movie about the search for a habitable planet in space to overcome the problem of food shortage on Earth. The movie was a box office hit because of its spectacular visuals and the timeless love between a father and daughter, but the most important key was that it contained real science. Unlike other science fiction movies, this movie was made according to scientific principles, allowing viewers to learn about science through entertainment and imagine that it could happen in real life. Let’s take a closer look at the scientific content in Interstellar that made people interested in physics, even those who were not interested in physics at all.
In the movie Interstellar, the main character, Cooper, spends so much time on a star with a high gravity that he loses track of time on Earth. While only a few minutes have passed on the planet, decades have passed on Earth, and Cooper’s distress at seeing his son and daughter grow old so quickly made the moviegoers sad. The dramatic reunion of daughter Murphy with her father, Cooper, just before he dies of old age, is arguably the most moving scene in the movie. Here, many people find it difficult to accept that time passes at different rates on Earth and other planets in the universe, and wonder how it works. Einstein’s theory of relativity explains this. Relativity is divided into special relativity and general relativity, with special relativity dealing with the inertial coordinate system and general relativity dealing with the accelerated coordinate system.
An inertial coordinate system is a coordinate system in which momentum is conserved because no external force acts on an object. Therefore, an object remains at rest or moves at constant speed, and only in this case, Newton’s first law, the law of inertia, is established, so it is called an inertial coordinate system. The law of inertia states that in the absence of an external force, an object in motion will continue to maintain its shape, and an object at rest will remain at rest. When a bus suddenly starts moving forward, our body tries to stay still, causing us to lean backward, and when the bus stops moving forward, our body tries to keep moving forward, causing us to lean forward. In this system of inertial coordinates, an object moving forward appears faster to a person moving backward than it does to a stationary person looking at it. However, Einstein realized that the speed of light is constant whether you’re traveling backwards or standing still, and he theorized that all motion is relative to each other. This means that absolute space and absolute time do not exist, but that time and space are defined by the observer. Light doesn’t travel 300,000 kilometers in one second, it takes one second for light to travel 300,000 kilometers. If a spacecraft is traveling very fast and you shoot a beam of light perpendicular to the direction of travel of the spacecraft, the light will travel a greater distance when seen by a stationary person outside the spacecraft than when seen by a person inside the spacecraft. Since it is the speed of light, not time, that is absolute, an event that occurs in one second to a person inside the spacecraft will appear to take longer than one second to a stationary person outside the spacecraft. This leads to the conclusion that time passes slower for an object that is moving at a faster rate than it does for an object that is stationary.
Unlike an inertial coordinate system, an accelerated coordinate system is a coordinate system in which the velocity of an object changes due to an external force. In this accelerated coordinate system, there is a force called inertia. When an object undergoes accelerated motion, it tends to fall to one side, which an observer in an inertial coordinate system can understand as the law of inertia, but an observer in an accelerated coordinate system does not know the source of this force and calls it an inertial force. Examples of this are when a bus starts and accelerates, the handle leans backward, or when an elevator accelerates and becomes heavier as it goes up. However, if an observer is in an enclosed box in an accelerating coordinate system, the observer cannot tell whether the forces on him or her and the object are due to gravity or inertia. This means that dropping a ball from the ground and releasing it as it accelerates upward in zero-gravity space will appear to be the same phenomenon. This inability to distinguish between inertial and gravitational forces is called equivalence principle.
General relativity describes gravity as a warping of space-time. It explains the universal attraction caused by gravity as a curvature of space that brings objects closer together, like a marble rolling on a rainbow. Similarly, the slower passage of time in places with strong gravity can be explained by the warping of time by gravity.
Gravity causes time to stretch. The stronger the gravitational force, the greater the degree to which time slows down. In fact, even on Earth, differences in altitude cause differences in the strength of gravity, so there is a difference in the speed at which time passes, but the difference is so small that it is imperceptible. This is why in the movie Interstellar, a few minutes on a star with a large gravitational field is equivalent to a few decades on Earth.
In addition to relativity, which drives the main flow of the story, there are other scientific concepts in the movie, such as parallel universes, black holes, and more, and many people were able to learn about them. I realized how much interest a single medium can arouse in a large number of people, and if there are more movies and other entertainment media that treat science in a simple and interesting way like “Interstellar”, professional disciplines, including physics, will be able to attract a large number of people.
