![]() Also known as Einstein-Rosen bridges or white holes, as opposed to black holes, speculation about wormholes abounds. ![]() Wormholes are theoretical "tunnels" through the fabric of space-time that could connect different moments or locations in reality to others. But the physical reality of those time-travel methods is no piece of cake. General relativity might also provide scenarios that could allow travelers to go back in time, according to NASA. If it can communicate with the satellites whizzing overhead, your phone can nail down your location in space and time with incredible accuracy. This kind of time travel may seem as negligible as the Kelly brothers' age gap, but given the hyper-accuracy of modern GPS technology, it actually does matter. (We did the math: If you estimate a blink to last at least 100,000 microseconds, as the Harvard Database of Useful Biological Numbers does, it would take thousands of days for those 38 microsecond shifts to add up.) Given those numbers, it would take more than seven years for the atomic clock in a GPS satellite to un-sync itself from an Earth clock by more than a blink of an eye. The atomic clocks onboard don’t tick over to the next day until they have run 38 microseconds longer than comparable clocks on Earth. Department of Defense, a military drone - engineers must account for an extra 38 microseconds in each satellite's day. This means that in order to maintain the accuracy needed to pinpoint your car or phone - or, since the system is run by the U.S. Combined with the negative 7 microseconds from the special relativity calculation, the net result is an added 38 microseconds. So, because the GPS satellites are much farther from the center of Earth compared to clocks on the surface, Physics Central added, that adds another 45 microseconds onto the GPS satellite clocks each day. Then, according to general relativity, clocks closer to the center of a large gravitational mass like Earth tick more slowly than those farther away. Read more: Could Star Trek's faster-than-light warp drive actually work? For GPS satellites with atomic clocks, this effect cuts 7 microseconds, or 7 millionths of a second, off each day, according to the American Physical Society publication Physics Central. The satellites circle the planet from 12,500 miles (20,100 kilometers) away, moving at 8,700 mph (14,000 km/h).Īccording to special relativity, the faster an object moves relative to another object, the slower that first object experiences time. The Global Positioning System, or GPS, helps us know exactly where we are by communicating with a network of a few dozen satellites positioned in a high Earth orbit. The difference that low earth orbit makes in an astronaut's life span may be negligible - better suited for jokes among siblings than actual life extension or visiting the distant future - but the dilation in time between people on Earth and GPS satellites flying through space does make a difference. This not-to-scale image shows the constellation of GPS satellites whizzing around the Earth in distant orbits. "Now I've got that over his head." General relativity and GPS time travel "So, where I used to be just 6 minutes older, now I am 6 minutes and 5 milliseconds older," Mark Kelly said in a panel discussion on July 12, 2020, previously reported. The difference in the speed at which they experienced time over the course of their lifetimes has actually widened the age gap between the two men. Scott Kelly spent 520 days in orbit, while Mark logged 54 days in space. Astronaut Scott Kelly was born after his twin brother, and fellow astronaut, Mark Kelly. While we don't accelerate humans to near-light-speed, we do send them swinging around the planet at 17,500 mph (28,160 km/h) aboard the International Space Station. An observer traveling at high velocity will experience time at a slower rate than an observer who isn't speeding through space. And third, nothing can go faster than the speed of light.įrom those simple tenets unfolds actual, real-life time travel. It stays the same no matter what, and no matter where it's measured from. First, all things are measured in relation to something else - that is to say, there is no "absolute" frame of reference. The short version of the theory is deceptively simple. Special relativity describes the relationship between space and time for objects moving at constant speeds in a straight line. ![]() Along with his later expansion, the theory of general relativity, it has become one of the foundational tenets of modern physics. (Image credit: Getty)Įinstein developed his theory of special relativity in 1905. Twin brothers Scott and Mark Kelly are both astronauts, and have both participated in landmark studies about the effects of space on the human body.
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