It’s the most brilliant idea of all time – and certainly also one of the least understood.
In 1905, the brilliant German physicist Albert Einstein claimed that time and space are relative and deeply intertwined. Sound complicated? Well, the idea is sophisticated, but, contrary to popular belief, relativity is not a rocket ship.
The main insight is to see time as a kind of path that we are obliged to follow. Even though you are now standing still reading this, you are still moving through time. After all, the seconds are ticking by, like a train rushing into the future at a steady pace.
So far, no bombastic news. What Einstein found surreal is that this “time train” can be accelerated or slowed down – going faster for some and slower for others. And that, to make time go slower, just move around.
If you are walking, for example, the hours will be slower for you than for someone who is standing still. But, as the speeds we experience on a daily basis are very small, the difference in the passage of time is negligible.
The effect is noticeable when we kick the bucket: if you spent a year inside a spaceship moving at 1.07 billion km/h and then returned to Earth, the people who stayed here would be ten years older than you!
As they were practically stationary in relation to the ship’s movement, time passed ten times faster for them – but that’s from their point of view. For other Earthlings, it was you who had the experience of feeling time slow down.
In this way, time ceases to be a universal value and becomes relative to each person’s point of view – hence the name “relativity”. Still according to Einstein’s studies, time passes more and more slowly until it reaches the speed of light, 1.08 billion km/h, the maximum possible value in the Universe.
At that speed, the most astonishing thing happens: time simply stops passing! It’s as if the speed of space (that of the ship’s speedometer) removed everything possible from the speed of time. At the other extreme, for someone standing still, speed is all concentrated in the dimension of time.
“Einstein postulated this based on the experiences of other physicists and worked with the wonderful consequences of this fact”, says physicist Brian Greene, from Columbia University, in the United States, author of the book The Elegant Universeone best seller which explains in simple language the ideas of the German physicist.
But the discoveries of Relativity do not stop there. As late as 1905, Einstein concluded that matter and energy were as intertwined as space and time. Hence the famous equation E = mc2 (energy = mass x the speed of light squared), which reveals that a crumb of matter can generate an absurd amount of energy.
a genius discovery
Einstein showed that space, time, mass and gravity are closely linked
1 – According to Einstein, everything in the Universe moves at a speed distributed between the dimensions of time and space. For a stationary body, time runs at maximum speed. But when the body starts to move and gains speed in the dimension of space, the speed of time decreases for it, passing more slowly. At 180 km/h, 30 seconds pass in 29.99999999999952 seconds. At 1.08 billion km/h (the speed of light), time simply does not pass.
2 – A consequence of this change in the speed of time is the contraction in the length of bodies. According to the Special Theory of Relativity – the first part of Einstein’s theory, elaborated in 1905 –, the faster something is, the shorter it becomes. For example: someone who saw a car moving at 98% of the speed of light would see it 80% shorter than if they observed it standing still.
3 – In the so-called General Theory of Relativity (the second part of the study, published in 1916), Einstein used the previous finding to redefine gravity. He came to understand it as the distortion that a body causes in the fabric of space-time. The force that holds people to the ground is the curvature created by the Earth in the space around it. By table, bodies with a lot of gravitational attraction also make time pass very slowly.
5 – A practical application of Relativity is the calibration of GPS satellites, which guide planes and ships. By Special Relativity, it is known that the speed of 14 thousand km/h of the satellites causes their internal clocks to delay 7 millionths of a second per day in relation to Earth clocks. But, according to General Relativity, they feel gravity less (since they are at an altitude of 20,000 km) and advance 45 millionths of a second per day. Adding the two variables gives an advance of 38 millionths per day, which needs to be set on the satellite clock. So if it weren’t for Einstein’s theory, the system would accumulate a location error of about 10 kilometers per day.