Albert Einstein's special mark on the universe

Story highlights

  • It has been 100 years since Albert Einstein presented his theory of general relativity to the world
  • Jeffrey Bennett: Relativity is necessary to comprehend the universe as we know it; we should all know it

Jeffrey Bennett is the author of "What is Relativity? An Intuitive Introduction to Einstein's Ideas, and Why They Matter" (Columbia University Press, 2014). His 2015 Relativity Tour has taken him to 25 cities to an audience of 10,000 people. He is the author of six children's books that are being read by astronauts aboard the International Space Station for the Story Time From Space program. The opinions expressed in this commentary are solely those of the author.

(CNN)It has been exactly 100 years since Albert Einstein presented his theory of general relativity to an audience of scientists on November 25, 1915. While virtually everyone has heard of Einstein and his theory, very few people have any idea of what the theory actually is.

This is a shame, not only because there is a great public thirst for understanding of it, but also because relativity is important, for at least four major reasons.
Jeffrey Bennett
General relativity provides our modern understanding of space, time and gravity -- which means it's crucial to almost everything we do in physics and astronomy. For example, you cannot understand black holes, the expansion of the universe or the Big Bang without first understanding the basic ideas of relativity. Though few people realize it, Einstein's famous equation E = mc2 is actually part of the theory of relativity, which means that relativity also explains how the sun shines and how nuclear power works.
    A second reason everyone should know about relativity lies in the way it changes our perception of reality. Relativity tells us that our ordinary perceptions of time and space are not universally valid. Instead, space and time are intertwined as four-dimensional space-time.
    In our ordinary lives, we perceive only three dimensions—length, width and depth—and we assume that this perception reflects reality. However, in space-time, the four directions of possible motion are length, width, depth and time. (Note that time is not "the" fourth dimension; it is simply one of the four.)
    Although we cannot picture all four dimensions of space-time at once, we can imagine what things would look like if we could. In addition to the three spatial dimensions of space-time that we ordinarily see, every object would be stretched out through time. Objects that we see as three-dimensional in our ordinary lives would appear as four-dimensional objects in space-time. If we could see in four dimensions, we could look through time just as easily as we look to our left or right. If we looked at a person, we could see every event in that person's life. If we wondered what really happened during some historical event, we'd simply look to find the answer.
    To see why this is so revolutionary, imagine that you met someone today who deeply believed that Earth is the center of the universe. You would probably feel sorry for this person, knowing that his or her entire world view is based on an idea disproven more than 400 years ago.