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These posts make more sense when read in order. Please click here for the first article in this series to enter the rabbit hole.
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| Albert Einstein holding an Albert Einstein marionette around 1931. He joked that the puppet wasn’t fat enough, so he crumpled up a letter and stuffed in under its jacket. |
If you say the word “genius”, most people think of Einstein. He is one of the world’s most famous scientists, if not the most famous. Following the publication of his strange theories, he quickly became a celebrity—particularly in America, perhaps partly because of his resemblance to America’s great literary genius, Mark Twain.
When Einstein was about four or five years old, someone showed him a compass and he was fascinated by the fact that the needle always points north. He wondered what the invisible force was that kept the needle steady. It was like magic and he wanted to know how such a thing was possible. As he grew older he focused on learning all about electromagnetism, which led him into physics.
At the young age of 26, he published his special theory of relativity which revolutionized our understanding of the universe. That was in 1905 and at that time physicists knew that the speed of light travels at a defined speed from the work of James Clerk Maxwell forty years earlier. Einstein took this and Galileo’s rule that the laws of physics are the same in all non-accelerating frames of reference and—casting other assumptions aside—showed how these two things raised some rather strange implications.
Here are the basics. Special relativity deals with objects in uniform motion relative to those that are considered stationary and insists that the results of experiments performed in both situations will match. In the order that I will discuss them, the implications are:
- Mass and energy are equivalent (E = mc2). Material objects can approach, but not reach, the speed of light.
- Time is not absolute and depends on the observer’s frame of reference. Two people may experience the passage of time as the same, but they would no longer be in sync. This is time dilation.
- Space is not absolute and depends on the observer’s frame of reference. Two people can measure an identical distance, but to each observer, the other’s will appear to be shorter. This is called length contraction.
- For two simultaneous events, one may be seen before the other by one observer, and in reverse order for another observer. This is failure of simultaneity at a distance.
- Time and space are not separate things, but are a unified spacetime.
Let’s take a closer look at these, but we’ll skip over how they arose from the special theory of relativity. Instead we’ll look at what these things mean.
One of the results that came out of this was his famous equation, E = mc2. Energy equals mass multiplied by the speed of light squared. Einstein’s formula means that matter is a concentrated form of energy. Fortunately it’s not easy to release it. If the average person could release all the energy packed away in his or her body, the resulting explosion would equal that of more than 66,000 nuclear bombs like the one the United States used to destroy Nagasaki, Japan. Going the other way, it also means that photons of light can create matter, and physicists have accomplished that.[1]
Nuclear fission and fusion can release or absorb energy depending on which elements are involved. Nuclear fission splits heavy elements into lighter ones by dividing an element’s nucleus into two or more smaller nuclei. Fission is used in atomic bombs, while fusion is used in hydrogen bombs.
During fusion, the sun, for example, fuses lighter elements into slightly heavier ones, which releases energy that comes to us as sunlight. Plants turn the sunlight back into mass to form their leaves and such. After eating the plants, we convert it back into energy to run our bodies. Energy is converted into mass and mass into energy. It is just a temporary change in its state.
Both mass and energy come in different forms. Mass can be inertial mass or gravitational mass. Common forms of energy include nuclear, electrical, kinetic, elastic, thermal, chemical, radiant, gravitational, and potential. But the overall amount of energy and mass in a closed system never changes. That’s the First Law of Thermodynamics—the conservation of energy. Einstein added mass to that law, since he showed that energy and mass are equivalent. The difference is in its state, and that is temporary.
[1] Jeffrey Winters, “Let There Be Matter”, Discover Magazine, December 1997, p. 40, https://www.discovermagazine.com/the-sciences/let-there-be-matter, November 30, 1997.
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