Studying the Speed of Light “All light travels through empty space at the same speed – the speed of light…which is about 300,000 kilometers per second” (Bennett, Donahue, Schneider & Voit). While this is fact, it has not always been known. Many early scientists and philosophers, including Aristotle, believed that the speed of light was infinite, or instantaneous (Fowler). It was thought that light could travel any distance in no time at all. It wasn’t until the 17th Century that scientists began to question the speed of light and explore it further. To accurately measure the speed of light, several early attempts were made. The efforts of Galileo, Roemer, Fizeau, and Foucault are some of the most notable early attempts at determining the speed of light. Galileo Galilei (1564 – 1642) is one of the most noted astronomers of all time (Hutchins and Adler). He was also one of the first researchers to question Aristotle’s view of light’s speed. Galileo’s experiment involved two participants standing at two hilltops one mile apart. Each participant held a covered lantern. One participant uncovered his lantern, allowing light to be emitted. As soon as the other participant observed the light from the lantern, he uncovered his own lantern and allowed its light to shine. The time it took for the light to “return” to the first participant was recorded. This was repeated several times at a distance of one mile, and an average time was documented. The participants then moved to hilltops that were ten miles apart and the entire process was repeated. Having documented the average times for both one mile and ten miles apart, Galileo expected to see a significant difference between the average times. However, he was unable to detect any time difference. Therefore, he concluded that either light is infinite and takes absolutely no time to travel from one point to another, or that light travels so quickly that it could not be measured with the tools and methods to which he had access. “Most likely he [Galileo] used a water clock, where the amount of water that empties from a container represents the amount of time that has passed. Galileo just deduced that light travels at least ten times faster than sound.” (History of Speed of Light: Historical Measurements) Olaus Christensen Roemer (1644 – 1710) was a Danish astronomer who made the first successful estimate of the speed of light (Hathaway). Roemer was interested in the planet Jupiter and its moons and made many observations concerning their orbits and eclipses. Based on calculations of Roemer, as well as previous astronomers, Io, one of Jupiter’s moons, makes a revolution around Jupiter every 42 hours, 28 minutes, and 34 seconds (A Case History in Astronomy and Physics: The Speed of Light). This observation led Roemer to believe that he could accurately predict the eclipses of Io. Contrarily, his predictions were not so accurate. “Actually, Roemer found, for several months the eclipses lagged more and more behind the expected time, but then they began to pick up again.” (Fowler) He soon realized that, during times when the Earth was closer to Jupiter, the eclipses were occurring at closer intervals, and while the Earth and Jupiter were farther apart, the intervals of eclipses were farther apart. Roemer presumed that the interval difference must be because of the extra time it took for light to travel when the Earth and Jupiter were father apart. “Using the commonly accepted value for the diameter of the Earth's orbit, he came to the conclusion that light must have traveled at 200,000 kilometers per second.” (History of Speed of Light: Historical Measurements) Armand Hippolyte Louis Fizeau (1819 – 1896) was a French physicist who also made a contribution to the study of the speed of light (Singer). Fizeau designed an apparatus in which a beam of light shone between the teeth of a rapidly rotating toothed wheel. Unlike a “second lantern” of Galileo,
equation describes how energy and mass are related. This equation unifies energy (E), mass (M) and the speed of light (C). What is implied by this is that mass and energy are the same physical entity and can be converted into each other. On top of this, modern physics also states that it is physically impossible to travel faster than the speed of light. Just the thought of exceeding the speed of light creates much controversy while simultaneously opening up many other scientific possibilities. If Einstein’s…
to break through the enemy trench lines.
The first discourse on the topic of the speed of light appears to originate from the ancient Greek society of philosophers. Aristotle, a highly regarded philosopher at the time contradicted a fellow philosopher Empedocles on the speed of light. Empedocles argued that because light moved; some time to travel must be present. Aristotle however was under the impression light was to travel instantaneously. This later led to further discussion and further experiments…
Something ‘Snells’ Fishy
How do we, as humans, see something? Simply put, through light! Without light, nothing that is visible would be visible at all! This is because the things that we see truly are material things, but they are visible because of the light that bounces off of them to hit our eyes. This then makes the image appear in our brains and from there, it’s all up to the doctors. According to Tulane University, “Our eyes interpret these wavelengths as different colors. If only a single…
relativity in order to explain a perplexing observation: the speed of light is always observed to
be the same, regardless of the motion of the observer or the light source.
We will use the letter “c” to represent the speed of light.
The speed of light is 3 108 m/s, or 186,000 miles/second.
The speed of light is so fast that it can make about 40 round trips across the USA in one second!
In order to explain how the speed of light can stay the same Einstein developed an idea called time…
travel while remaining in one place in space. This is because we travel through time as well as space. Time does not stop unless an object travels at the speed of light.
3. Light travels through space; however, it does not travel through time. Light and time are one and the same: light determines the speed of time and time determines when light will reach a certain place.
4. Time dilation is the process of starching time. It occurs when the rate of moving into the future is altered.
5. The first…
frames of reference that are not accelerating. The idea of relative motion is useful in comparing
airspeed with ground speed for an airplane or the speed of a boat relative to the water with the
speed of the boat relative to the shoreline. Therefore, it was natural to assume light also had
differing speeds depending on the frame of reference. In the late 1800s, physicists assumed light
was a wave and needed a medium in which to travel. This assumed medium was referred to as
ether and was attached to…
Gatso speed cameras use radar technology to measure how fast a vehicle is traveling. If a motorist is driving above the speed limit for that road then several photo are then taken of the vehicle. The Gatso uses a powerful flash to show the rear of the vehicle, its registration plate, and calibration lines on the road. Gatso speed cameras are always rear facing. The reason for this is that the speed cameras 'flash' will not blind oncoming motorists. However, this also means that the speed camera…
(b) 877 ft.
(c) 377 ft.
a 13. What is the meaning of a flashing yellow light?
(a) slow down and proceed with caution
(b) be prepared for the light to change red
c 14. What is the meaning of a flashing red light?
(b) stop and wait for the light to change green
(c) stop and proceed when safe
a 15. What is the meaning of a flashing red traffic signal light at an intersection?
(a) Stop completely as at a stop sign and proceed when safe.
would they reject such an intelligent man? But they did and in 1902 he was hired as a patent examiner in Berne. In 1905 his intelligence came out of the dark. He invented the theory E=mc2 that means (energy equals mass times the speed of light squared) and the theory of light.
Einstein was born in 1879 in Germany. When he was a small child he didn’t show any high intelligence. In fact he even took a while to learn how to speak. He was a smart kid but it took a while for people to notice his intelligence…
how light influence actors in the film. Shutter Speed
1. On YOUR camera what is the fastest shutter speed you have? (You might need to look at the manual.)
On my Nikon D5200 camera, the fastest shutter speed I have is 1/4000
2. On YOUR camera what is the slowest shutter speed you have?
The slowest shutter speed on my Nikon D5200 camera on the other hand is 1/1.3.
3. If you are shooting a fast motion scene and want to "freeze" the action, would you use a fast or slow shutter speed?