E mc2 why speed of light

Deepak Chopra - Dr. Stephen Covey - Dr. This is an older page, prepared from only hearing Einstein's theories second-hand. In part, the page builds up one of my favourite fundamental questions: "The speed of light is constant relative to Now, more up-to-date dissertations on this subject can be found on some of our more recent pages: New for November 6, How well do modern scientists really know their Einstein?

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.

For example, when astronaut Scott Kelly spent nearly a year aboard the International Space Station starting in , he was moving much faster than his twin brother, astronaut Mark Kelly, who spent the year on the planet's surface. Due to time dilation, Mark Kelly aged just a little faster than Scott — "five milliseconds," according to the earth-bound twin. Since Scott wasn't moving near lightspeed, the actual difference in aging due to time dilation was negligible.

In fact, considering how much stress and radiation the airborne twin experienced aboard the ISS, some would argue Scott Kelly increased his rate of aging. But at speeds approaching the speed of light, the effects of time dilation could be much more apparent. Imagine a year-old leaves her high school traveling at When the year-old got back to Earth, she would have aged those 5 years she spent traveling. Her classmates, however, would be 65 years old — 50 years would have passed on the much slower-moving planet.

We don't currently have the technology to travel anywhere near that speed. But with the precision of modern technology, time dilation does actually affect human engineering. GPS devices work by calculating a position based on communication with at least three satellites in distant Earth orbits. Those satellites have to keep track of incredibly precise time in order to pinpoint a location on the planet, so they work based on atomic clocks. In order to maintain pace with Earth clocks, atomic clocks on GPS satellites need to subtract 7 microseconds each day.

When something is moving four times as fast as something else, it doesn't have four times the energy but rather 16 times the energy—in other words, that figure is squared. So the speed of light squared is the conversion factor that decides just how much energy lies within a walnut or any other chunk of matter. Here's an example. 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 18 kilotons of TNT.

That's roughly the size of the bomb that destroyed Hiroshima in On Earth, however, there is no practical way to convert a paper clip or any other object entirely to energy.