This verified the prediction of special relativity to one part in 1, While such accuracy may strengthen the status of Einstein's theory, it won't relieve the perplexity of those who wonder who, after all, does the traveling?
Since the motion is relative, the astronaut could consider that her sister did the traveling while her spaceship remained at rest. Why wasn't her sister the younger one? This seeming paradox, which has sparked much puzzlement over time warps, involves a misconception.
The motions of the twins are not strictly relative. The spaceship must decelerate, turn around, and reaccelerate to return home. In the language of relativity theory, the astronaut changes her reference frame while her twin does not. This is an absolute difference between them. It unambiguously picks out the space traveler as the twin who will be younger. As with other effects of special relativity, time dilation only shows up when relative speeds are close to that of light or when high precision is involved.
That is why it is counterintuitive enough to puzzle even some scientists. Nevertheless, relativistic effects do have practical consequences. Particle accelerators are designed to take account of them. Together with gravitational time effects predicted by Einstein's general theory of relativity clocks run slower under stronger gravity , special relativity's time dilation is important for the new United States military navigational system, which also is available for civilian purposes. The system uses satellite-carried atomic clocks.
Its precision is such that, were relativity neglected, navigational errors of several miles could accumulate within a day. The Gravity Probe B mission was launched in to study two aspects of Einstein's theory about gravity : the geodetic effect, or the warping of space and time around a gravitational body; and frame-dragging, which describes the amount of space and time a spinning objects pulls with it as it rotates.
GP-B confirmed two of the most profound predictions of Einstein's universe, having far-reaching implications across astrophysics research. Gravity Probe B used four ultra-precise gyroscopes to measure the two gravitational hypotheses. The probe confirmed both effects with unprecedented precision by pointing its instruments at a single star called IM Pegasi. If gravity did not affect space and time, the probe's gyroscopes would always point in the same direction while it was in polar orbit around Earth.
Knowing these stories helps us understand that the universe is constantly exhaling and inhaling new energy, in new stars and in the death of old ones. This cycle has been happening for billions of years. But as new stars are forged from an abundance of hydrogen lingering from the Big Bang, those stars convert the hydrogen to other elements.
The same cyclical disorder is happening here on Earth. Species appear, they live, they go extinct, and we study them believing we are exempt from their fate.
We are a future-facing species. Even our memories are designed to help us predict the future. We have storage of past experiences that are, on a biological level, designed to inform our decisions. If you once touched a hot stove and burned yourself, you know not to do it again. This goes against how we understand our memory.
We think of it as something that belongs solely to the past, or perhaps the present. But our memories, above all, are not about the past; they are for our future. Our brains know to do anything we can to stay alive, while also planning out the next steps. This time spent largely inside messes with our internal clocks, which is why March felt like it was a year long and how it is also suddenly December but it was only just April and somehow today is Wednesday and also seems like Monday, but who even knows.
So retrospectively, that creates the subjective experience of time flowing quickly. This is hyperbole, but instead of trying to predict where we might find plants and food, humans began planting seeds knowing that it was not for instant gratification but for long-term survival.
Our nature is to create the future. It is one of our most inherent skills and desires, and in this moment, it has been snatched from us all. Humans are notoriously resilient. Before modern humans had the ability to count past 10, age did not exist. While humans have always observed the movement of planets in the sky and the changing seasons to help understand the passing of time, for the majority of human history our modes of relating to it were different.
In the late 18th century, people began making timelines. They started to map the scale of the Roman Empire and measure the spread of disease. Suddenly, time became incredibly important, as train operators needed to ensure that it was the same time in London as in Glasgow so that departure and arrival schedules were accurate.
People started carrying pocket watches and were newly acutely aware of how the minutes passed in the day. No matter how far back we look in human history, there has always been room for us to forge new relationships with this most valuable, most mysterious, and most fundamental thing. Just as it has always been and will always be, time is a paradox. And third, nothing can go faster than the speed of light.
Read more: Hidden in Einstein's math: faster-than-light travel? From those simple tenets unfolds actual, real-life time travel. An observer traveling at high velocity will experience time at a slower rate than an observer who isn't speeding through space. Astronaut Scott Kelly was born after his twin brother, and fellow astronaut, Mark Kelly. Scott Kelly spent days in orbit, while Mark logged 54 days in space. 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.
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. Read more: Can we stop 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.
According to special relativity, the faster an object moves relative to another object, the slower that first object experiences time. For GPS satellites with atomic clocks, this effect cuts 7 microseconds, or 7 millionths of a second, off each day, according to American Physical Society publication Physics Central. Read more: Could Star Trek's faster-than-light warp drive actually work? Then, according to general relativity, clocks closer to the center of a large gravitational mass like Earth tick more slowly than those farther away.
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. Combined with the negative 7 microseconds from the special relativity calculation, the net result is an added 38 microseconds. 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.
Department of Defense, a military drone — engineers must account for an extra 38 microseconds in each satellite's day.
0コメント