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History of the Speed of Light

The speed of light was first discovered by Galileo in 1667 when he determined that light travels at least 10 times faster than sound. Then, in 1675, Roemer furthered this research by observing the ellipses of Jupiter's moons and Earth's position and reasoning that light must travel at least at the speed of 200,000 km/second. Later in 1728, by using stellar aberration (ratio of earth's orbit to the speed of light), English physicist, James Bradley, determined that the speed of light in a vacuum is 301,000 km/sec. More than 100 years later, French physicist, Fizeau used wheels, mirrors, and light to determine that the speed of light is 313,300 Km/sec. Soon after, French physicist, Foucault also used mirrors. However, Foucault instead shined light on rotating and reflecting mirrors to determine the speed of light to be 299,796 km/sec. This then leads to current day as we know that the speed of light in a vacuum is 299,792 km/second. Examine the timeline below for a visual representation.

external image speed_of_light_street_sign_2.jpg


Cern

Geneva, Switzerland is home to CERN or the European Organization for Nuclear Research. At CERN, there is the LHC, or the Large Hadron Collider that is nearly 100 meters underground acting as a particle accelerator to create particle collisions at speeds close to the speed of light.
At CERN, the LHC accelerator reaches 99.99% the speed of light. It accelerates the protons 11,245 times per second around the LHC ring. Then, these two beams of protons collide with each other to make approximately 600 million collisions that particle physicists examine and analyze.


LHC.jpg
LHC cavity module

How was Light Speed Measured?

Is the speed of light too fast to be measured? No, today we now how fast it moves. But before technology was as advanced as it is now however, it was a little more difficult. Galileo had an idea of how to measure it. In the middle of the night, he stood on one hill and his partner stood on a faraway one. Everytime Galileo shone his light, his partner was supposed to shine his light when he saw it. Galileo would then divide the deistance between himself and his partner by the time that it took his partner to see the light. Unfortunately for Galileo, light is too fast for this method.
In the 1670s Ole Roemer, a Danish astronomer realized something funny about Jupitor's moon Io. Sometimes during the year Io would be ahead of its rotation path and sometimes behind. Roemer realized that the moon's orbit didn't speed up and slow down, but rather the speed of light only made it appear that way. He reasoned that he was actually seeing the moon in the past because of the time its took the light rays to get from Io to Earth. When Io was closest to Earth, the light rays got from the moon to Earth faster because they traveled over a shorter distance and he saw Io at a point that was closer in time to when the light rays had first hit it compared to when the moon was far away from the Earth and the rays had to travel farther and he saw Io further into the past. This proves that light does not travel infinately fast, because if it did, it wouldn't matter how far Earth was from Io, we would be able to see it when the rays first hit it, rather than waiting for them to take time to get all the way to Earth. By knowing how far Io was from Earth and where he thought the moon was in real time, compared to where he saw the moon, Roemer was able to calculate the speed of light to be about 300,000 km per second, which is about what we use today.

How is the Speed of Light Measured?

Now, we use a method much light Galileo's, we however, have much more acurate techniques. Austronauts attached a mirror to a rock on the moon so that we can aim a laser at it from earth and time it's two and a half second trip there and back. We have also calculated the speed of light to be almost 300,000 km per second. So, are our methods really that much better than those of the scientists before us?

external image retroflector_lg.gifexternal image laser_beam_lg.gif

Electromagnetic Radiation v. Light

There is strong conjecture that electromagnetic radiation and light are the same because it has been proven that the speed of electromagnetic radiation is 300,000 km per second. Does this number sound familiar?


Is it possible to accelerate matter to the speed of light?


No! It is impossible to accelerate matter to the speed of light. In order for this to be possible, either the object needs to have zero mass or it must have an infinite energy source (according to special relativity). Because the object is matter, it will have mass, and there are no infinite energy sources. Because of these two facts, accelerating matter to the speed of light is impossible. However, it is possible to accelerate matter 99.999…% the speed of light, but never exactly the speed of light.



What could happen if we could accelerate matter to the speed of light?


If we could accelerate matter to the speed of light, the whole universe would skrink so that it would appear to be a few billion kilometers across. Also, time would slow down so much that the universe would age trillions of years, but you would only age a couple seconds. Because of this time difference, new galaxies would appear and stars would be born and explode in the blink of an eye. (This doesn’t sound too appealing to me!)


Videos

Short Clip on the Speed of Light
CERN and the LHC



Pick-Up Lines...

Warning: Do not use if you don’t want to get slapped…
  1. "As I approach you at near the speed of light, I hope I can experience the time dilation of seeing you for eternity."
  2. "My love for you is like the speed of light in all reference frames: it'll remain constant in all circumstances."
  3. "If beauty were sunlight, you'd shine from a million light-years away."




Cartoons

7547_flying_cartoon[1].gifgwan649l[1].png
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References

History:
http://www.speed-light.info/measure/speed_of_light_history.htm#speed_of_light_today

Images from Timeline:
http://image.absoluteastronomy.com/images/topicimages/j/ja/james_bradley.gif
http://upload.wikimedia.org/wikipedia/commons/thumb/b/b0/Galileo-sustermans.jpg/650px-Galileo-sustermans.jpg
http://upload.wikimedia.org/wikipedia/commons/thumb/f/f6/Ole_roemer.jpg/225px-Ole_roemer.jpg
http://www.lyceeflaubert-lamarsa.com/public/IMG/jpg/Hippolyte_Fizeau_1_.jpg
http://www.scientific-web.com/en/Physics/Biographies/images/Foucault01.jpg

Cern:
http://public.web.cern.ch/public/en/LHC/LHC-en.html
http://public.web.cern.ch/public/en/LHc/Facts-en.htmlhttp://cdsweb.cern.ch/record/1221488

Measurement:
http://www.colorado.edu/physics/2000/waves_particles/lightspeed_evidence.html
http://www.lpi.usra.edu/lunar/missions/apollo/apollo_15/experiments/lrr/

Acceleration to the speed of light information:
http://startswithabang.com/?p=1176

Pick-Up Lines:
http://www.pickuphelp.com/
http://www.physicsforums.com/showthread.php?t=87195

1st Cartoon:
http://www.mchumor.com/00images/7547_flying_cartoon.gif

2nd Cartoon:
http://www.cartoonstock.com/newscartoons/cartoonists/gwa/lowres/gwan649l.jpg

3rd and 4th Cartoon:
http://www.cartoonstock.com/directory/s/speed_of_light.asp