How is theory of relativity used today

But strangely enough, relativity plays a key role in a multi-billion dollar growth industry centered around the Global Positioning System GPS. When Einstein finalized his theory of gravity and curved spacetime in November , ending a quest which he began with his special relativity, he had little concern for practical or observable consequences.

He was unimpressed when measurements of the bending of starlight in confirmed his theory. Even today, general relativity plays its main role in the astronomical domain, with its black holes, gravity waves and cosmic big bangs, or in the domain of the ultra-small, where theorists look to unify general relativity with the other interactions, using exotic concepts such as strings and branes.

But GPS is an exception. The system is based on an array of 24 satellites orbiting the earth, each carrying a precise atomic clock. Using a hand-held GPS receiver which detects radio emissions from any of the satellites which happen to be overhead, users of even moderately priced devices can determine latitude, longitude and altitude to an accuracy which can currently reach 15 meters, and local time to 50 billionths of a second.

So, even if two particles of light carry very different amounts of energy, they will travel at the same speed. This has been shown experimentally in space. It is responsible for the civilian space program, as well as aeronautics and aerospace research.

It's vision is "To discover and expand knowledge for the benefit of humanity. They both came from a high-energy region near the collision of two neutron stars about 7 billion years ago.

A neutron star is the highly dense remnant of a star that has exploded. A formation of galaxies appear to form a smiling face. Two yellow-hued blobs hang atop a sweeping arc of light.

The lower, arc-shaped galaxy has the characteristic shape of a galaxy that has been gravitationally lensed — its light has passed near a massive object en route to us, causing it to become distorted and stretched out of shape. Just like the Sun bends the light from distant stars that pass close to it, a massive object like a galaxy distorts the light from another object that is much farther away.

In some cases, this phenomenon can actually help us unveil new galaxies. Entire clusters of galaxies can be lensed and act as lenses, too. When the lensing object appears close enough to the more distant object in the sky, we actually see multiple images of that faraway object. In , scientists first observed a double image of a quasar, a very bright object at the center of a galaxy that involves a supermassive black hole feeding off a disk of inflowing gas.

Map of dark matter made from gravitational lensing measurements of 26 million galaxies in the Dark Energy Survey. When a massive object acts as a lens for a farther object, but the objects are not specially aligned with respect to our view, only one image of the distant object is projected.

This happens much more often. Weak lensing is very important for studying some of the biggest mysteries of the universe: dark matter and dark energy. Dark matter is an invisible material that only interacts with regular matter through gravity, and holds together entire galaxies and groups of galaxies like a cosmic glue.

Dark energy behaves like the opposite of gravity, making objects recede from each other. It's primary mirror will be 2. By surveying distortions of weakly lensed galaxies across the universe, scientists can characterize the effects of these persistently puzzling phenomena.

As an exoplanet passes in front of a more distant star, its gravity causes the trajectory of the starlight to bend, and in some cases, results in a brief brightening of the background star as seen by a telescope. The artistic animation illustrates this effect. This phenomenon of gravitational microlensing enables scientists to search for exoplanets that are too distant and dark to detect any other way. While microlensing has so far found less than confirmed planets, WFIRST could find more than 1, new exoplanets using this technique.

This is the first picture of a black hole. Using the Event Horizon Telescope, scientists obtained an image of the black hole at the center of the galaxy M Credit: Event Horizon Telescope Collaboration.

The very existence of black holes, extremely dense objects from which no light can escape, is a prediction of general relativity. The inset shows a close-up view of the shockwaves created by the two jets. This Spitzer image shows the galaxy Messier 87 M87 in infrared light, which has a supermassive black hole at its center.

Around the black hole is a disk of extremely hot gas, as well as two jets of material shooting out in opposite directions. One of the jets, visible on the right of the image, is pointing almost exactly toward Earth. The details of how such jets work are still mysterious, and scientists will continue studying black holes for more clues.

Until recently, this was only theoretical. To shoehorn the odd behavior of light into Newton's framework for physics scientists in the s supposed that light must be transmitted through some medium, which they called the "luminiferous ether.

That was a tall order. Researchers set about trying to detect that mysterious ether, hoping to understand it better. Michelson and chemist Edward Morley calculated how Earth's motion through the ether affected how the speed of light is measured, and unexpectedly found that the speed of light is the same no matter what Earth's motion is.

If the speed of light didn't change despite the Earth's movement through the ether, they concluded, there must be no such thing as ether to begin with: Light in space moved through a vacuum. According to Einstein, in his book " Autobiographical Notes " Open Court, , Centennial Edition , the budding physicist began questioning the behavior of light when he was just 16 years old.

In a thought experiment as a teenager, he wrote, he imagined chasing a beam of light. Classical physics would imply that as the imaginary Einstein sped up to catch the light, the light wave would eventually come to a relative speed of zero — the man and the light would be moving at speed together, and he could see light as a frozen electromagnetic field. But, Einstein wrote, this contradicted work by another scientist, James Clerk Maxwell, whose equations required that electromagnetic waves always move at the same speed in a vacuum: , miles per second , kilometers per second.

Philosopher of physics John D. Norton challenged Einstein's story in his book " Einstein for Everyone " Nullarbor Press, , in part because as a year-old, Einstein wouldn't yet have encountered Maxwell's equations. But because it appeared in Einstein's own memoir, the anecdote is still widely accepted. 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.

One gram of uranium or plutonium 0. This energy can power cities, but as the Manhattan Project proved, it can also be harnessed for a weapon.

We know the universe and jiggling Jell-O have a lot in common thanks to Einstein and gravitational waves. Ok, special relativity is great, but what about technology inspired by the theory of general relativity? Three hundred years ago, Isaac Newton observed that small objects in the universe are drawn toward larger objects, and he discerned that strength of this attraction depended on their mass.

More massive objects — like Jupiter — have a stronger pull than smaller bodies like Mercury. Enter Einstein and general relativity. His theory proposed that massive objects can physically bend space. When the marble lands, the Jell-O will press downwards and the adjacent areas will slant like a ramp toward the marble. Using his field equations, Einstein explained that gravity is actually the curving of this Jell-O, which in the real universe is made from space and time.

It twists and turns and bends in response to the motion of matter and energy. We perceive that stretching and distortion of the fabric of spacetime as the force of gravity. This means that large sources of gravity — for instance, the Earth — can alter time. This is also considered time dilation. Relativity was a roadblock during the early days of GPS.

GPS satellites must be in sync with your phone or car receiver in order to pinpoint your location. When engineers initially blasted GPS satellites into outer space, they assumed that the effects of relativity would be too small to alter the highly precise atomic clocks onboard.

They were wrong. That sounds marginal, but it would have thrown off your location by as much as seven miles. Experiments with atomic clocks have measured gravity-based shifts in spacetime over extraordinarily short distances, such as a study from the National Institute of Standards and Technology that measured the effect over the length of a foot. The difference is small — 90 billionths of a second over 79 years — but this subtle shift in relativity means you age faster than a friend if she is standing a couple of stairs below you on a staircase.

Also, if space can bend, then general relativity argues that gigantic collisions between stellar objects can send shockwaves through outer space. The same thing happens if you wave your hand through the air, though on a much smaller scale.

If it spots these waves, the event could be illuminating, Dijkgraaf said. Photo by NASA. People who spend lengthy spells on space stations have actually moved forward in time relative to folks stuck on Earth.