How do scientists measure the speed of light if it's faster than anything else? :o?

Question

If light is indeed the fastest of anything we know,.. how do scientists actually calibrate it? Like,.. do they measure the speed of it bewteen two 'markers',.. or do they use something else entitirely? I know it's said to be 135,000miles per sec,.. but HOW do they know this?

Answer 1

It is large but not infinitely large. So, by using sensitive time measuring instruments and long distances, they could measure it. See Michelson and Morley's experiments on velocity of light.

Answer 2

My concept is that when the universe replaced into created via the large Bang the Universe began increasing outward (on the fee of light). If we've been waiting to get closer this expanditure (14 billion easy years from the middle), and tried to moved previous that increasing, the "nothingness" could dissolve us in a fashion that we weren't killed, yet in no way have been. that's a close-by that hasn't been created yet, and subsequently the universe ought to have a failsafe for such issues. Like going backin time and assembly your self. i do no longer think of the Universe could enable that paradox. As for the guy awnsering. He reported that for the duration of 50 years Einstein would be shown incorrect. I heavily doubt which will ever ensue. on each occasion I pay attention information approximately Einstein, that's often relaying that computers are proving his equations (on a chalkboard no much less!) remarkable a hundred years later!

Answer 3

Well, it's actually a very interesting experiment, kind of complicated. As I remember it, a tiny wheel with many many many notches is turned in front of a mirror. A beam is sent between two of the notches, and reflected off the mirror, which is a long distance away, and then the notch through which the beam comes back is noted. Using the distance to the mirror and the time taken for the wheel to turn, the speed of light is measured.
Sorry I can't be more exact in my wording here. Wikipedia will probably provide a picture to elucidate things if you're curious.

Answer 4

The speed of light in vacuum c is not measured. It has an exact fixed value when given in standard units. Since 1983 the metre has been defined by international agreement as the length of the path travelled by light in vacuum during a time interval of 1/299,792,458 of a second. This makes the speed of light exactly 299,792.458 km/s. Since the inch is defined as 2.54 centimetres, the speed of light also has an exact value in non-metric units. This definition only makes sense because the speed of light in vacuum is constant; a fact which is subject to experimental verification.

The first successful measurement of c was made by Olaus Roemer in 1676. He noticed that the time between the eclipses of the moons of Jupiter was less as the distance away from Earth is decreasing than when it is increasing. He correctly surmised that this is due to the varying length of time it takes for light to travel from Jupiter to Earth as the distance changes. He obtained a value equivalent to 214,000 km/s which was very approximate because planetary distances were not accurately known at that time.

In 1728 James Bradley made another estimate by observing stellar aberration, being the apparent displacement of stars due to the motion of the Earth around the Sun. He observed a star in Draco and found that its apparent position changed during the year. All stellar positions are affected equally in this way. This distinguishes the effect from parallax which affects nearby stars more noticeably. A useful analogy to help understand aberration is to imagine the effect of motion on the angle at which rain falls. If you stand still in the rain when there is no wind it comes down vertically on your head. If you run through the rain it appears to come at you from an angle and hit you on the front. Bradley measured this angle for starlight. Knowing the speed of the Earth around the Sun he found a value for the speed of light of 301,000 km/s.

The first measurement of c on Earth was by Armand Fizeau in 1849. He used a beam of light reflected from a mirror 8 km away. The beam passed through the gaps between teeth of a rapidly rotating wheel. The speed of the wheel was increased until the returning light passed through the next gap and could be seen. Then c was calculated to be 315,000 km/s. Leon Foucault improved on this a year later by using rotating mirrors and got the much more accurate answer of 298,000 km/s. His technique was good enough to confirm that light travels slower in water than in air.

Answer 5

i had a footrace around the block with some light last summer an won!!!!!