How fast light

Empedocles thought that light, whatever it was made of, must travel and therefore, must have a rate of travel. Aristotle wrote a rebuttal of Empedocles' view in his own treatise, On Sense and the Sensible , arguing that light, unlike sound and smell, is instantaneous. Aristotle was wrong, of course, but it would take hundreds of years for anyone to prove it. Each person held a shielded lantern.

One uncovered his lantern; when the other person saw the flash, he uncovered his too. But Galileo's experimental distance wasn't far enough for his participants to record the speed of light. He could only conclude that light traveled at least 10 times faster than sound. 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.

Fields, an Heuristic Approach. The Irrationality of. The Number i i. The Transcendentality of. A traveler, moving at the speed of light, would circum-navigate the equator approximately 7. By comparison, a traveler in a jet aircraft, moving at a ground speed of mph, would cross the continental U.

Calculating the Energy from Sunlight over a 12 hour period. Calculating the Energy from Sunlight over actual full day. If you take baths, you may have noticed how water rushes out of the nozzle and begins to fill the tub. It's fun to watch the first waves of water reach the end of the bathtub and splash up along the sides. Now think about something even faster. What are we talking about?

Light , of course! When you flip the light switch, does light act like water? Do you see it shoot out of the light bulb and splash over the walls like a wave? Light fills the room everywhere instantaneously. It's super fast! But exactly how fast is light? You certainly can't measure it with your eyes. As we already mentioned, the flick of a light switch instantaneously fills a room with light. Early scientists had noticed this same phenomenon. In fact, many early scientists thought light didn't travel at a fast speed.

Instead, they believed it was either instantaneously present or not. Over short distances, it's impossible to sense the movement of light with the naked eye. To measure the speed of light , scientists would learn that they needed large distances to work with. He did this by studying the apparent motion of Jupiter's moon Io , which is hundreds of millions of miles from Earth.

It would be a couple hundred more years before James Clerk Maxwell would hypothesize that light was an electromagnetic wave when developing his theory of electromagnetism. Other scientists, including Albert Einstein, developed many other theories about the nature of light and began to develop more and more precise measurements of its speed.

Today, the speed of light in vacuum , known by the mathematical symbol c , is exactly ,, meters per second. So how fast is that, exactly?

Really, really fast! In terms you might be more familiar with, light travels at about , miles per second or approximately million miles per hour!

If you could travel at the speed of light , you could circle the entire Earth over seven times in one second. According to Einstein's theory of relativity , the speed of light is the maximum speed at which all energy, matter, and information in the universe can travel.

The speed of light is an important constant in the study of physics and other advanced scientific disciplines. It has also given rise to an important measurement in astronomy : the light -year, which is defined as the distance light can travel in one year.

The light Earth receives from the Sun takes about eight minutes and 30 seconds to arrive. The light from the next closest stars in our galaxy takes over four years to reach Earth! Light from the farthest stars in distant galaxies could take billions of years to reach Earth.

Some of the most distant galaxies are billions of light -years away. When scientists see light from these distant galaxies, they're literally seeing history, since what they see today doesn't necessarily resemble what those stars would look like today if you were to land on one! If today's Wonder of the Day went by too fast for you, don't worry!

You can keep the learning going at supersonic speed by exploring the following activities with a friend or family member:. Great question--be sure you add it to the Wonder Bank! We're sorry you feel that way, ayden. OMG, I'm just like you. I have no idea lets try to discover this together, wait never mind, I will search it up and reply to you very soon.

That would be a great question for our Wonder Bank --you should submit it! We're love when we're learning and having fun at the same time!

Hi, Carter! We're sorry you didn't like the video. There is so much to learn in the text, too. We hope you still had fun exploring this Wonder! Hi, elyse! Thanks for sharing what you learned. Great, Izzy! We're glad you're having fun exploring Wonderopolis. Hi, owen! You're right, light is extremely fast. So fast it seems automatic. We're glad to hear you liked this Wonder.

There are many other Wonders you can explore on Wonderopolis. Click on "Explore Wonders" at the top! It seems that nothing can be faster than the speed of light. However, if our spacecraft would be traveling at the speed of light, we would reach the Sun in only 8.

If you traveled around the Earth with the speed of light, you would make a complete tour of our planet 7. In theory, it seems that nothing is faster than the speed of light, or is there?

It appears that nothing is faster than the speed of light, but the Universe , as always, eludes our perception once again. Scientists have demonstrated that the Universe is expanding, and this expansion is even faster than the speed of light. If you were to hold a torch and run with it, the speed of its light would still travel at the same rate.

Some galaxies are moving away from our Milky Way faster than the speed of light, and this is happening because space itself is moving along with them. If there were something more efficient than traveling with the speed of light, it would be traveling through wormholes.