Active 6 years, 10 months ago. Viewed 1k times. Improve this question. Add a comment. Active Oldest Votes. Improve this answer. John Rennie John Rennie k gold badges silver badges bronze badges. It seems that our time should be increased for the astronaut. That's why the astronaut returns younger. When you say the astronaut returns younger I assume you're talking abut the twin paradox but that involves accelerated motion.
In , Einstein published his theory of special relativity, which put forth a startling idea: There is no preferred frame of reference.
Everything, even time, is relative. Two important principles underpinned his theory. The first stated that the same laws of physics apply equally in all constantly moving frames of reference. The second said that the speed of light -- about , miles per second , kilometers per second -- is constant and independent of the observer's motion or the source of light.
According to Einstein, if Superman were to chase a light beam at half the speed of light, the beam would continue to move away from him at exactly the same speed.
These concepts seem deceptively simple, but they have some mind-bending implications. According to this equation, mass and energy are the same physical entity and can be changed into each other. Because of this equivalence, the energy an object has due to its motion will increase its mass.
In other words, the faster an object moves, the greater its mass. This only becomes noticeable when an object moves really quickly. If it moves at 10 percent the speed of light, for example, its mass will only be 0. But if it moves at 90 percent the speed of light, its mass will double. As an object approaches the speed of light, its mass rises precipitously.
If an object tries to travel , miles per second, its mass becomes infinite, and so does the energy required to move it. For this reason, no normal object can travel as fast or faster than the speed of light. Intermediate What do I need to do to become an astronomer?
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Beginner Are there telescopes that can see the flag and lunar rover on the Moon? To create an astronomical clock, he recorded the precise timing of the eclipses of Jupiter's moon , Io, from Earth. He noticed that the eclipses appeared to lag the most when Jupiter and Earth were moving away from one another, showed up ahead of time when the planets were approaching and occurred on schedule when the planets were at their closest or farthest points — a rough version of the Doppler effect or redshift.
In a leap of intuition, he determined that light was taking measurable time to travel from Io to Earth. Since the size of the solar system and Earth's orbit wasn't yet accurately known, argued a paper in the American Journal of Physics , he was a bit off. But at last, scientists had a number to work with.
In , English physicist James Bradley based a new set of calculations on the change in the apparent position of the stars due Earth's travels around the sun. Two new attempts in the mids brought the problem back to Earth.
French physicist Hippolyte Fizeau set a beam of light on a rapidly rotating toothed wheel, with a mirror set up 5 miles 8 km away to reflect it back to its source. Varying the speed of the wheel allowed Fizeau to calculate how long it took for the light to travel out of the hole, to the adjacent mirror, and back through the gap. Another French physicist, Leon Foucault, used a rotating mirror rather than a wheel to perform essentially the same experiment.
Another scientist who tackled the speed of light mystery was Poland-born Albert A. Michelson, who grew up in California during the state's gold rush period, and honed his interest in physics while attending the U. Naval Academy, according to the University of Virginia. In , he attempted to replicate Foucault's method of determining the speed of light, but Michelson increased the distance between mirrors and used extremely high-quality mirrors and lenses.
In his second round of experiments, Michelson flashed lights between two mountain tops with carefully measured distances to get a more precise estimate. And in his third attempt just before his death in , according to the Smithsonian's Air and Space magazine, he built a mile-long depressurized tube of corrugated steel pipe.
The pipe simulated a near-vacuum that would remove any effect of air on light speed for an even finer measurement, just slightly lower than the accepted value of the speed of light today. Michelson also studied the nature of light itself, wrote astrophysicist Ethan Siegal in the Forbes science blog, Starts With a Bang.
The best minds in physics at the time of Michelson's experiments were divided: Was light a wave or a particle? Michelson, along with his colleague Edward Morley, worked under the assumption that light moved as a wave, just like sound.
And just as sound needs particles to move, Michelson and Morley and other physicists of the time reasoned, light must have some kind of medium to move through. This invisible, undetectable stuff was called the "luminiferous aether" also known as "ether". Though Michelson and Morley built a sophisticated interferometer a very basic version of the instrument used today in LIGO facilities , Michelson could not find evidence of any kind of luminiferous aether whatsoever.
Light, he determined, can and does travel through a vacuum. The equation describes the relationship between mass and energy — small amounts of mass m contain, or are made up of, an inherently enormous amount of energy E.
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