No matter your major, interests, or educational background, there’s a good chance you’ve heard of Albert Einstein. He’s a famous scientist whose messy, white hair and picture with his tongue sticking out have made him an iconic figure not only in science but also in pop culture. What exactly was he famous for?
Einstein has become well-known thanks to his theories of relativity. Here, we’ll only focus on the special theory of relativity, which is based on two key ideas we must assume to be true – called postulates – that lay the groundwork for special relativity.
Einstein’s first postulate states that the laws of nature are the same in every frame of reference. The second identifies the speed of light as a constant, the ‘c’ in E = mc^2, that moves at the same speed of about 3*10^8 m/s, independent of other motion.
The Famous Equation
E = mc^2 is the basis of special relativity; therefore, understanding it is crucial to understanding special relativity. In Einstein’s famous equation, the ‘E’ represents all the energy in a system. The ‘m’ is mass and the ‘c’ is the speed of light, which you now know to be a constant number everywhere. Knowing this, the equation is a way of expressing the relationship between energy and mass, since energy is equal to mass times the speed of light squared.
What does special relativity tell us?
We don’t use special relativity in our everyday lives because the theory is used to explain what happens when objects move near the speed of light. Special relativity tells us that an object’s velocity – its speed in a given direction – is not absolute, meaning it isn’t constant from every perspective.
For example, in the recent Disney movie Lightyear, Buzz’s mission early in the movie caused him to travel at speeds close to the speed of light. Each time he returned from traveling at high speeds, he returned to the planet below, only to find that everyone around him had aged, while he had not. The closer he got to the speed of light, the older people on the planet became. At such high speeds, time seemed to slow down from Buzz’s perspective. After 100 years had passed on the planet, Buzz was still the same age because of how special relativity messed with time.
“Time is Relative”
When people use the phrase “time is relative,” they imply that time moves differently for different people. However, given that none of us are traveling near the speed of light, time remains the same for all of us. While time may be relative, the saying only makes sense at incredibly high speeds. Now that you understand Einstein’s postulates and the ideas behind the particular theory of relativity, you know exactly why that is.