#SPEED OF LIGHT IN METERS PERSECOND SERIES#

With all those pieces in place, we should be able to predict the length of time it takes for a beam of light to make it from the earth outwards (and probably back again, if we’re testing the speed of light).

With the mass of the earth, and the length of a month, we can figure out the mass of the moon, so we can tell the exact shape of the space between the earth and the moon. We can do tests of the strength of gravity on Earth, and given Newton’s equations, we can calculate the mass of the Earth. There’s another way to test the speed of light, a bit further from home. The experiment's accuracy was limited by geological instability and condensation problems, but in 1935 a result of 299,774 ± 11 km/s was obtained, the most accurate measurement of the speed of light to that date.

#SPEED OF LIGHT IN METERS PERSECOND SERIES#

Michelson died in 1931 with only 36 of the 233 measurement series completed, but Pease and Pearson carried on. The tube is evacuated to a pressure of about 10 Torr. The apparatus measures this angle, which is proportional to the time of flight of the beam. During the light beam's ten-mile journey the mirror rotates through a small angle, so the reflected beam has a small angle to the outgoing beam. Inside the vacuum chamber a beam of light from an arc lamp is reflected from an eight-sided mirror spinning at 512 revolutions per second, then makes ten passes through the tube, after which it returns and reflects again from the same face of the mirror. It consists of a mile long 3 ft diameter vacuum chamber in a Southern California valley containing an optical system with two large concave mirrors at either end. Michelson, Fred Pease and astronomer Francis Pearson's 1930-35. However, if you know the masses and locations of the gravitationally weighty objects, you can calculate the exact shape of space that light will have to pass through, and therefore how long it should take to travel between any two points.Īpparatus used in physicist Albert A. The more gravitationally weighty objects between the light source and your detector, the longer a path your light must travel. Gravity changes the shape of the space surrounding an object, and since light always travels in locally straight lines, light is affected by this warping. That’s not to say that the presence of an object with a strong gravitational field won’t affect light - it certainly does, but the way that a strong gravitational field influences light is a bit different from the slowing down you get from going through a thick substance. Outside of our atmosphere’s region of influence, you are very rapidly in a vacuum. But it’s dense with matter, the physical pieces of you and me and rocks and the atmosphere. The solar system is dense, but it’s dense with material in very specific locations - to extend your metaphor a bit, compared to interplanetary space, the planet is very dense. There’s no material in a vacuum, quite by definition, for the light to encounter. ajizaiīut if you’re in a vacuum, the index of refraction is precisely 1 there is no change to the speed of light in a vacuum. Image credit: public domain, via wikimedia user. If you have a sufficiently dense material, light can slow down really considerably.Ī ray of light being refracted in a plastic block. Light in water goes even slower - water’s refractive index is 1.33, so the speed of light in water is slowed by 74,384,595 meters per second. That’s a slowdown of 89,911 meters per second, which looks like a lot but is only three ten-thousandths of the speed of light. Light in air is 1.0003 times slower than light in a vacuum, which slows it all the way down from 299,792,458 meters per second to 299,702,547 meters per second. So, light going from air to water has a certain bend to it, which we can measure, and that bend tells us how much slower light will move through water. This slowdown is related to the index of refraction of the material, which is the technical term applied to how much light bends when it enters that material.

Now, if light is indeed travelling through a dense material (for instance, air or water), light does slow down. However, it sounds as though you’re thinking of gravitational field strength (which is certainly correlated with the density of matter) like an atmosphere of material that light must make it through. You’re right that our galaxy represents a much denser population of stuff than intergalactic space, and that our solar system is similarly a more dense collection of stuff than the space between stars within our galaxy.

Speed of light in meters persecond