General Relativity And The Einstein Myth
'Einstein' and 'genius' are synonyms. This isn't so for any other geniuses. How has this happened? How can one man represent our intellectual history? There are many possible theories. The complete answer likely consists of a melting pot of many, including:
His job as a patent clerk while becoming a scientific pioneer makes him relatable. We often feel unappreciated at work, and think that our passions will lead to greatness
It's reassuring to see him as Earth's wise grandparent. He battles questions most of us can't even ask, let alone answer
It's convenient to have a single name for referencing scientists in general
However it happened, Einstein now holds a similar position in our culture to Kleenex or Q-Tips. He is the 'name brand' scientist.
These reasons for Einstein's niche have nothing to do with his work. They are based on relatability, comfort, and convenience. Maybe we could learn why we make certain people famous or popular. However, they are silent on why Einstein deserves his place atop our academic ladder.
We need to address his major discoveries. Whatever the reason for his relevance, his findings more than qualify him for the job. While his career is filled with brilliance, his crowning achievement is the theory of general relativity. It reshaped our understanding of the universe, and brought physics into a radical and strange frontier.
The History of Gravity
Einstein published the theory of general relativity in 1915. It explains not only how gravity works, but also why it works. This was Einstein's main insight. In 1687, Isaac Newton published his universal law of gravitation. What he accomplished was showing that the force causing the planetary orbits, and the force that made things fall to earth, were the same force.
Newton was dissatisfied with his great theory. He had united these two phenomena. He also gave mathematical laws for how gravity affects objects. What he didn't explain was how the sun influenced Earth from 150,000,000 kilometres away. Newton called this 'action at a distance.' Enter Einstein, and general relativity.
General Relativity Basics
Einstein showed that the universe is a far more exotic place than had been previously imagined. He discovered that:
Space and time aren't separate. They are part of a single 'fabric' of 'space-time'. Spacetime consists of four dimensions: our three familiar spacial ones, plus a time dimension
Gravity is caused by huge bodies (stars, planets, etc.) curving spacetime with their enormous masses. All objects have some gravity, but it's proportional to their mass
The gravitational motion Newton discovered is due to objects taking the shortest path through curved spacetime. We see this in planetary orbits and the arc of a tossed ball
Curved spacetime due to gigantic masses solved Newton's 'action at a distance' issue. Gravity is a result of these distortions directly affecting the path of objects through spacetime. The mass of stars and planets reshape spacetime like a bowling ball on a trampoline. Smaller balls are drawn towards the bowling ball, if they are close enough to be within its 'gravity.' Luckily for us, the reason the planets don't fall into the sun is because of angular momentum, which keeps them moving around the sun. This combats the gravity, and maintains a steady orbit instead of a free fall.
It's natural and even healthy to find this unusual. We view space as emptiness, with nothing happening in it. To find out that empty space curves and causes gravity can make you skeptical about Einstein's famous theory.
What makes us confident that general relativity isn't a joke at our expense? The mark of a good scientific theory is that it produces testable predictions. General relativity's most famous prediction? Black holes.
Black Holes
Black holes are an example of the result of pushing a theory to its extremes. We yawn at watching an apple fall to the ground, and assume gravity is boring. But at its peak, gravity is responsible for one of the universe's most incredible objects.
A black hole is the result of a collapsed star. This collapse is key to black hole weirdness. Whether a collapsing star becomes a black hole depends on its mass. To end up a black hole, the collapsing star must weigh about five times the mass of the sun. While collapsing, all of the dead star's mass compacts into an unbelievably dense ball. If we were able to measure a teaspoon of black hole material, it would weigh many times more than everyone on Earth combined.
Black holes got their name because their gravity is so strong that not even light can escape it. This means that they are invisible to normal telescopes. We have to detect them by looking for the intense gravity they assert on other stars and planets. People were incredibly skeptical of the existence of black holes after they were predicted by Einstein's theory. However, this technique of detecting black holes by gravitational influence has proven their existence. This is one of general relativity's many correct predictions.
General Relativity vs. The People of Earth
Where do we fit into this talk of warped spacetime and black holes? I would argue that the main human consequence of understanding general relativity is that it shows us how interwoven we are with the cosmos. Under Newton's gravity, we viewed the world as a theatre stage. Humans were the actors and actresses. Deep space sat quietly in the audience. It shared a set of gravitational rules, but didn't affect the plot of human history.
General relativity shows the huge impact that the cosmos has on us. We are still the leads in our production, but the literal stars weigh on us like relentless stage coaches. While this can seem daunting, it teaches us about the intimate place we hold in our galactic community. Einstein brought the universe into a massive group hug. This is more than enough reason to honour his name, work, and memory.