S10 Measure the Speed of Light

S10 Measure the Speed of Light - Measure The Speed of Light...

Info icon This preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Measure The Speed of Light With Chocolate and a Microwave http://physics.about.com/mbiopage.htm From Joseph Andersen ,Your Guide to Physics . Nothing travels faster than light - it only takes 8 minutes for it to reach the Earth from the nearest star, the Sun, which is 150 million kilometers away. This means that when you see the sun (remember do not look directly at the sun), you’re really seeing light that left the sun 8 minutes ago – you’re seeing the sun as it was, and where it was, 8 minutes earlier. One of the first to try to measure the speed of light was Galileo. In the early 17th century, the general belief amongst scientists (or natural philosophers as they were often called then) was that the speed of light was infinite; that is, light could travel any distance in no time at all. Just as with many other important discoveries made by Galileo, he disagreed with most of his contemporaries. One of Galileo’s great strengths as a scientist was his ability to conceive experiments to test his theories. To measure the speed of light, he and his assistant each took a shuttered lantern to hilltops one mile apart. Galileo flashed his lantern, and the assistant was supposed to open the shutter to his own lantern as soon as he saw Galileo's light. Galileo would then time how long it took before he saw the light from the other hilltop. Then, he could divide the distance by the time he measured to get a speed. Unfortunately for Galileo, this time he had not conceived an experiment sufficiently clever to measure the extraordinary speed with which light traveled. We now know that light travels at approximately 3x10 8 m/s (that is approximately 1100000000 km/Hr), so it would travel the one mile (1.6 km) between the hills in 0.000005 s (5 microseconds), whereas, even if Galileo could time such a short trip, the assistant could not possibly unshutter his lantern fast enough that Galileo could tell what part of his measurement was the travel time! In fact, due to the extraordinarily high value of c (c is the standard symbol physicists use for the speed of light), there was nowhere on earth any two people could stand so that they could conduct this experiment. In order to make such a direct measurement of the speed of light, one needed a laboratory much larger than the earth! Remarkably, Galileo had effectively created such a Laboratory with another of his discoveries – the moons of Jupiter.
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern