×

注意！页面内容来自https://nineplanets.org/speed-of-light/，本站不储存任何内容，为了更好的阅读体验进行在线解析，若有广告出现，请及时反馈。若您觉得侵犯了您的利益，请通知我们进行删除，然后访问 原网页

Home » General » Speed of Light

The speed of light’s exact value is defined as 299.792.458 meters per second or approximately 300.000 km / 186.000 mi per second in a vacuum.

We know that nothing can surpass the speed of lightat least in theory. If you’d have the power to move with the speed of lightyou could go around the Earth 7.5 times in one second.

Light is a type of energyand early scientists believed that it must have traveled instantaneouslyunaware of its motion. As measurements of these wave-like particles became more precisewe now understand that the speed of light is a theoretical limit.

Currentlywe know that light-speed is unreachable by anything with mass. It is how telescopes work since most celestial objects are so far away from us; we actually see them in the past. Though we haven’t reached the speed of lighthere are some interesting facts about it.

The speed of light isn’t necessarily constant

Like soundlight travels in waves and can be slowed depending on what it is moving through. In a vacuumnothing can outpace light; howeverif a region contains mattereven the tiniest bits of it such as dustlight can bend when it comes in contact and results in a decrease in speed.

The light which travels through Earth’s atmosphere moves as fast as light in a vacuumwhile light passing through a diamond is slowed to less than half that speed.

Faster than the speed of light?

Whenever someone puts a limit on somethingwe tend to want to break that limit somehow. Fantasizing about moving faster than the speed of light is quite common in SCI-FI shows such as Star Trek.

Something as warp speed may be possible; howeverthe practicality of traveling faster than the speed of light renders the idea pretty farfetched.

If we take Einstein’s theory of general relativity into accountan object’s mass increases as it moves faster while its length contracts. At the speed of lightsuch an object would have infinite masswhile its length would be rendered 0 – or an impossibility.

Thus nothing can reach the speed of lightas the theory states. Howevermany still believe that the idea of warp speed is possibleand one day in the futureusable.

Some propose that a spaceship that could fold a space-time bubble around itself could exceed the speed of light. One thing is clearspace itself is not susceptible to our current lawsand our current understanding of the universe dictates that space itself is moving faster than the speed of light. In theoryit might be possiblebut we still have much to learn.

Light-year / Distant Past

You might have heard about the term light-year. Essentiallyit is the distance that light travels in the course of a yearand it is a measurement of both time and distance.

Take it this way; light travels from the Moon to our eyes in about 1 second. The light from the Sun takes about 8 minutes to reach our eyesand as suchthe Sun is eight light-minutes away. 

The nearest star system to usAlpha Centauriis 4.3 light-years away from usand thus we would get there in around 4.3 years. Many celestial objects are light-years away from us.

Some of them are even billions of light-years away. As suchwhen we study a celestial object which is more than one light-year awaywe are seeing it as it existed at the time that light left it. Thusalmost everything we see in the universe is literally history.

This principle guides us in our understanding of the universe after the Big Bang. The more distant a celestial object isthe earlier we see the beginning of our universe.

A Danish astronomer measured the speed of light

Olaus Roemer was the first astronomer to measure the speed of light successfully. This happened in 1676 when he observed a time interval between successive eclipses of the moons of Jupiter. 

It was about seven minutes greater than when the observations were carried out when the Earth in its orbit was moving away from Jupiter. Roemer argued that when the Earth was moving away from Jupiterthe observed time between eclipses was increased above the true value by about 3.5 minutes.

This was due to the extra distance that light had to travel from each successive eclipse to reach our planet. Converselywhen our planet was moving towards Jupiterthe observed interval decreased by about 3.5 minutes due to the smaller distance.

Roemer estimated the speed of light remarkably good considering the method employed. Ever since thennumerous scientists have made different attempts to measure the speed of light more accurately.

Image sources: