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History of the Development of the Speed of Light - Coggle Diagram
History of the Development of the Speed of Light
1879 - Albert Michelson
ran a series of experiments between 1877 and 1931
used Foucaults's method with improvements
in 1879 he achieved a value of 299944 +- 51 km/s
0.05% off the modern value
HIs 1926 experiment incorporating even more refinements
achieved a values of 299796 +- 4 km/s
4km/s off todays modern value
1862 - Leon Foucault
used an improved version of Fizeau's equipment
his equipment had the added advantage that the space that the light passed through could be filled with various substances
speed of light could be measured through these substances
recommended to him that he consider using Wheatstone's idea of a rapidly revolving mirror, and that he replace the rotating cogwheel with a rotating mirror
light shone into the rotating mirror which reflected it onto a fixed mirror
the fixed mirror reflected it back onto the rotating mirror, which in turn reflected it back to the source, having first rotated through a slight angle
measuring the slight angle let Foucault determine how far the mirror had rotated
permitted the calculation of the speed of light
c = 2dω/θ
arrived at the value of 298000km/s for c
1848 - Alfred Marie Cornu
last experiment used a light path almost three times as long as Fizeau's
yielded a value of 300400km/s
2% off the modern value
1848 - Hippolyte Fizeau
experiments
used a method similar to Galileo but with better technology
generated light that was reflected from a distant mirror, giving a total path length of about 19km
light was focused by lenses coming and going , and shone through a wheel with 720 teeth evenly placed around its rim
the gaps between the teeth were the same width as the teeth themselves
wheel was capable of rotating at hundreds of times per second
light would shine out through a gap and the rotational speed of the wheel was adjusted until no light shone back through the gap
allows the time for the light's round trip to be measured
based on the distance the wheel had rotated at the set speed
determined the speed of light to be about 315000km/s
1728 - James Bradley
worked with Samuel Molyneux to try to determine the parallax of the star Gamma Draconis
allows them to work out the distance to the star
although did not succeed thereby showing that the stars were much further away than was thought at the time
discovered an unexplained circular motion of the star's apparent position
Bradley realised how the phenomenon came about
the aberration of light
from Earth's POV the stars move
the fact that Earth's journey around the sun is the cause of this apparent motion makes no difference
except to changes the direction of a star's apparent motion - yielding a circular pattern
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discovered that the angles involved are very small and depend only on v/c
v = Earth's velocity
c = speed of light
Bradley calculated that the speed of light was 301 00km/s
1677 - Christiaan Huygens
said that "I have seen recently, with much pleasure, the beautiful discovery of Mr. Romer, to demonstrate that light takes time in propagating, and even to measure this time."
made the first calculation for the speed of light
based on Romer's observations and studies
210824 km/s
1675 - Ole Romer
danish scientist
Observations
observed that the variations in times of the eclipses coincided with times that Jupiter was closer to, or further away from Earth
followed Galileo's proposal
maximum of 16.6 minutes
due to their different orbital speeds around the sun
explained the time variations as being mostly caused by light having to cross the diameter of Earth's orbit
in 1676, he mad a rough estimate of the time it would take light to travel the distance from the Sun to Earth of about 11 minutes
about 214000km/s
first person to suggest that light travelled at a finite speed
1638 - Galileo
experiments
him and his assistance each had covered lanterns and stood on hilltops with a known distance between them
uncovered that his light and his assistant upon seeing Galileos light - immediately opened the shutter on his own
he noted to time of the return light using a water clock
concluded that that the speed of light was at least ten times the speed of sound
correctly concluded that light speed was too fast to be measured bu this method
he also realised his results were most likely inaccurate due to:
small time interval, human reaction time, and limitation with equipment
proposed a method based on observing Jupiter's moon Io going into and coming out of eclipses caused by Jupiter's shadow
