In high school you learn that space and time are two rigid magnitudes that do not change from one place to another. A second is a second, and a meter is a meter, here and on Jupiter. But, on November 25, 1915, Albert Einstein presented an innovative and revolutionary mathematical formula that could change everything.
In the midst of World War I, and only three years after the "unsinkable" Titanic sank, he presented the General Theory of Relativity. His main task was to describe how space and time were not rigid entities, but were alive. Specifically, Einstein argued that they constituted a new entity known as space-time, and that this could be deformed by gravity and speed. The more intense these magnitudes were, the more that space-time could be deformed. For this reason, seconds and meters no longer measured the same everywhere, but were relative (to speed and gravity).
“This formula was the culmination of a decade of work. In 1905 he had invented the concept of space-time (in the Theory of Special Relativity). But in 1915 he said how gravity could deform it (In the Theory of General Relativity) », explains José Luis Fernández Barbón, a researcher at the Institute of Theoretical Physics of the CSIC.
Today, Einstein's revolutionary postulates have passed many tests, and have relevance for various everyday applications, as Fernández Barbón explains:
A GPS with kilometers of error
"If the GPS did not take into account the relativity of time, due to the speed of the satellites and their height in the Earth's gravitational field, the atomic clocks inside would lose their calibration," says Fernández Barbón. "After a day, they would accumulate an error of kilometers and they would stop being useful."
The reason is that time and space on the Earth's surface and on a satellite are subjected to different speeds and different intensities in the gravitational field. Therefore, they are not the same and the GPS is out of adjustment.
Old televisions that accelerate particles
“Old televisions, which use cathode ray tubes, are small particle accelerators that cause electrons to crash into a screen. These electrons go very fast (at 30% of the speed of light), so you have to design magnets to direct them that take into account the formulas of relativity," according to the scientist. Without Einstein, these TVs wouldn't work.
"The properties of heavy atoms such as gold and mercury have to do with the fact that their electrons are very close to the nucleus and move very quickly," explains the CSIC researcher. Therefore, the reason why gold is so pure and does not oxidize is related to a relativistic effect..
«Everything that has to do with nuclear energy, such as atomic bombs, nuclear reactors or radioactivity, is related to the famous Einstein equation (E=mxc2). These processes imply changes in the mass of the nuclei that translate into energy changes”, the scientist maintains.
Magnetic and relative
“Everything that has to do with magnetic fields is explained by a relativistic effect. These fields had already been described before, but later we understood that it is relativity that really explains magnetism.
Journey to the future in the palm of your hand
«In the upper layers of the atmosphere, galactic cosmic rays generate particles called muons, they are like electrons but heavier. If you held one in the palm of your hand, you would see it disintegrate in a microsecond. From the top of the atmosphere they would take longer to reach sea level, so in theory they would have disintegrated before they got there. And yet muons are detected. The reason is that they are going so fast that their internal clock stretches time, so the muons travel to the future."
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