What does einsteins theory of relativity mean

When a direct current DC of electric charge flows through a wire, electrons are drifting through the material. Ordinarily the wire would seem electrically neutral, with no net positive or negative charge. That's a consequence of having about the same number of protons positive charges and electrons negative charges. But, if you put another wire next to it with a DC current, the wires attract or repel each other, depending on which direction the current is moving.

Assuming the currents are moving in the same direction, the electrons in the first wire see the electrons in the second wire as motionless.

This assumes the currents are about the same strength. Meanwhile, from the electrons' perspective, the protons in both wires look like they are moving. Because of the relativistic length contraction, they appear to be more closely spaced, so there's more positive charge per length of wire than negative charge.

Since like charges repel, the two wires also repel. Currents in the opposite directions result in attraction, because from the first wire's point of view, the electrons in the other wire are more crowded together, creating a net negative charge. Meanwhile, the protons in the first wire are creating a net positive charge, and opposite charges attract. In order for your car's GPS navigation to function as accurately as it does, satellites have to take relativistic effects into account.

This is because even though satellites aren't moving at anything close to the speed of light, they are still going pretty fast. The satellites are also sending signals to ground stations on Earth. These stations and the GPS unit in your car are all experiencing higher accelerations due to gravity than the satellites in orbit. To get that pinpoint accuracy, the satellites use clocks that are accurate to a few billionths of a second nanoseconds.

Add in the effects of gravity and the figure goes up to about 7 microseconds. If a person could, theoretically, catch up to a beam of light and see it frozen relative to their own motion, would physics as a whole have to change depending on a person's speed, and their vantage point? Instead, Einstein recounted, he sought a unified theory that would make the rules of physics the same for everyone, everywhere, all the time.

This, wrote the physicist, led to his eventual musings on the theory of special relativity, which he broke down into another thought experiment: A person is standing next to a train track comparing observations of a lightning storm with a person inside the train.

And because this is physics, of course, the train is moving nearly the speed of light. Einstein imagined the train at a point on the track equally between two trees. If a bolt of lightning hit both trees at the same time, the person beside the track would see simultaneous strikes.

But because they are moving toward one lightning bolt and away from the other, the person on the train would see the bolt ahead of the train first, and the bolt behind the train later. Einstein concluded that simultaneity is not absolute, or in other words, that simultaneous events as seen by one observer could occur at different times from the perspective of another. It's not lightspeed that changes, he realized, but time itself that is relative. Time moves differently for objects in motion than for objects at rest.

Meanwhile, the speed of light, as observed by anyone anywhere in the universe, moving or not moving, is always the same. They are, in fact, just different forms of the same thing. But they're not easily exchanged. Because the speed of light is already an enormous number, and the equation demands that it be multiplied by itself or squared to become even larger, a small amount of mass contains a huge amount of energy. For example, PBS Nova explained, "If you could turn every one of the atoms in a paper clip into pure energy — leaving no mass whatsoever — the paper clip would yield [the equivalent energy of] 18 kilotons of TNT.

That's roughly the size of the bomb that destroyed Hiroshima in One of the many implications of Einstein's special relativity work is that time moves relative to the observer. An object in motion experiences time dilation, meaning that when an object is moving very fast it experiences time more slowly than when it is at rest.

As a result, Earth and the other planets move in curved paths orbits around it. This warping also affects measurements of time. We tend to think of time as ticking away at a steady rate. But just as gravity can stretch or warp space, it can also dilate time. Subsequent experiments proved that this indeed happens. Special relativity is ultimately a set of equations that relate the way things look in one frame of reference to how they look in another — the stretching of time and space, and the increase in mass.

The equations involve nothing more complicated than high-school math. General relativity is more complicated. From her perspective, the light from the two strikes also has to travel equal distances, and she will likewise measure the speed of light to be the same in either direction. But because the train is moving, the light coming from the lightning in the rear has to travel farther to catch up, so it reaches her a few instants later than the light coming from the front.

Since the light pulses arrived at different times, she can only conclude the strikes were not simultaneous—that the one in front actually happened first. Once you accept that, all the strange effects we now associate with relativity are a matter of simple algebra. Einstein dashed off his ideas in a fever pitch and sent his paper in for publication just a few weeks later. Einstein kept obsessing on relativity all through the summer of , and in September he sent in a second paper as a kind of afterthought.

It was based on yet another thought experiment. And now imagine that it spontaneously emits two identical pulses of light in opposite directions.

Now, said Einstein, what would this process look like to a moving observer? From her perspective, the object would just keep moving in a straight line while the two pulses flew off. With a little more algebra, Einstein showed that for all this to be consistent, the object not only had to lose energy when the light pulses departed, it had to lose a bit of mass, as well.

Or, to put it another way, mass and energy are interchangeable. Einstein wrote down an equation that relates the two. All rights reserved. Share Tweet Email. Read This Next Wild parakeets have taken a liking to London. Animals Wild Cities Wild parakeets have taken a liking to London Love them or hate them, there's no denying their growing numbers have added an explosion of color to the city's streets. India bets its energy future on solar—in ways both small and big.