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TaurusSteve
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- Speed Of Light Formula
What is the equation/formula for the Speed Of Light? E=mc²? I thought it would be simple to find in a search.
TaurusSteve said:Summary:: Speed Of Light Formula
What is the equation/formula for the Speed Of Light? E=mc²? I thought it would be simple to find in a search.
Ah ok cheers!Ibix said:It's defined. There's no formula for it.
Historically it was measured by timing its flight over a known distance, just as you'd measure the speed of anything else. But modern understanding lead to the idea that you measure time and define the speed of light to be a specific value. Then distance units are defined in terms of how far light travels in a certain time.
Ibix said:for any wave, its speed is its wavelength times its frequency
True. But it's a distinction without a difference for light in vacuum as far as I'm aware, so I glossed over it in a B level thread.PeterDonis said:More precisely, its phase velocity is its wavelength times its frequency.
Physics just describes how things are. c is a constant as far as we know. That's all. No equation.TaurusSteve said:Summary:: Speed Of Light Formula
What is the equation/formula for the Speed Of Light? E=mc²? I thought it would be simple to find in a search.
Correct.PeroK said:The speed of light is, nowadays, defined to be exactly 299,792,458 metres per second; hence defining the metre.
This is correct in a sense of theoretical physics but it is not correct in the sense of measurement technology. ##\epsilon_0## or ## \mu_0## are meanwhile things we have to measure. They aren't given anymore as defined constants.You can also get it from the electromagnetic constants: ##c = \frac{1}{\sqrt{\epsilon_0 \mu_0}}##
Omega0 said:This is correct in a sense of theoretical physics but it is not correct in the sense of measurement technology. ##\epsilon_0## or ## \mu_0## are meanwhile things we have to measure. They aren't given anymore as defined constants.
Mister T said:I was under the impression that μ0\mu_0 has the exact value of 4π×10−7 N/A24 \pi \times 10^{-7}\ \mathrm{N/A^2},
A nice thing for you to read (written in German) is the following: https://www.ptb.de/cms/presseaktuel...taebe/massstaebe-heft-14-masse-fuer-alle.htmlvanhees71 said:In fact the electrodynamic quantities got the "largest" redefinition. If I remember right units like the Ohm got redefinitions at the order of ##10^{-9}##. If needed, I can try to find the citations for this. I think it can be found at NIST and other national metrological institutes.
The speed of light is a physical constant that represents the maximum speed at which all matter and information can travel in the universe. It is denoted by the letter "c" and has a value of approximately 299,792,458 meters per second in a vacuum.
The speed of light was first accurately measured by Danish astronomer Ole Rømer in 1676. He observed that the timing of eclipses of Jupiter's moon Io seemed to vary depending on the distance between Earth and Jupiter, which he attributed to the finite speed of light.
According to Einstein's theory of relativity, the speed of light is considered a constant because it is the same for all observers, regardless of their relative motion. This means that no matter how fast an observer is moving, they will always measure the speed of light to be the same value.
The speed of light is a crucial component in many scientific theories and equations, including Einstein's famous equation E=mc². It is also used in various fields such as astronomy, physics, and telecommunications to calculate distances, measure the age of the universe, and transmit information.
According to the currently accepted laws of physics, nothing can travel faster than the speed of light. As an object approaches the speed of light, its mass increases infinitely and would require an infinite amount of energy to continue accelerating. Therefore, it is considered impossible for any object with mass to reach or exceed the speed of light.