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Physics students learn the speed of light, c, is the same for all inertial observers but no one has ever actually measured it in one direction. Thanks to Kiwico for sponsoring this video. For 50% off your first month of any crate, go to 🤍kiwico.com/veritasium50 Huge thanks to Destin from Smarter Every Day for always being open and willing to engage in new ideas. If you haven't subscribed already, what are you waiting for: 🤍ve42.co/SED For an overview of the one-way speed of light check out the wiki page: 🤍ve42.co/wiki1way The script was written in consultation with subject matter experts: Prof. Geraint Lewis, University of Sydney 🤍ve42.co/gfl Prof. Emeritus Allen Janis, University of Pittsburgh Prof. Clifford M. Will, University of Florida 🤍ve42.co/cmw The stuff that's correct is theirs. Any errors are mine. References: Einstein, A. (1905). On the electrodynamics of moving bodies. Annalen der physik, 17(10), 891-921. (English) 🤍ve42.co/E1905 (German) 🤍ve42.co/G1905 Greaves, E. D., Rodríguez, A. M., & Ruiz-Camacho, J. (2009). A one-way speed of light experiment. American Journal of Physics, 77(10), 894-896. 🤍ve42.co/Greaves09 Response to Greaves et al. paper — 🤍arxiv.org/abs/0911.3616 Finkelstein, J. (2009). One-way speed of light?. arXiv, arXiv-0911. The Philosophy of Space and Time - Reichenbach, H. (2012). Courier Corporation. Anderson, R., Vetharaniam, I., & Stedman, G. E. (1998). Conventionality of synchronisation, gauge dependence and test theories of relativity. Physics reports, 295(3-4), 93-180. 🤍ve42.co/Anderson98 A review article about simultaneity — Janis, Allen, "Conventionality of Simultaneity", The Stanford Encyclopedia of Philosophy (Fall 2018 Edition), Edward N. Zalta (ed.) 🤍ve42.co/janis Will, C. M. (1992). Clock synchronization and isotropy of the one-way speed of light. Physical Review D, 45(2), 403. 🤍ve42.co/Will92 Zhang, Y. Z. (1995). Test theories of special relativity. General Relativity and Gravitation, 27(5), 475-493. 🤍ve42.co/Zhang95 Mansouri, R., & Sexl, R. U. (1977). A test theory of special relativity: I. Simultaneity and clock synchronization. General relativity and Gravitation, 8(7), 497-513. 🤍ve42.co/Sexl Research and writing by Derek Muller and Petr Lebedev Animations by Ivy Tello VFX, music, and space animations by Jonny Hyman Filmed by Raquel Nuno Special thanks for reviewing earlier drafts of this video to: Dominic Walliman, Domain of Science: 🤍ve42.co/DoS Henry Reich, Minutephysics: 🤍ve42.co/MP My Patreon supporters Additional music from 🤍epidemicsound.com "Observations 2"
C is the same in all directions in vacuum or your antennas wouldn’t resonate at their fundamental frequency c/f=lambda
The time needed to deliver our signals to Curiosity for example, doesnt it prove we measured the speed of light properly? I mean we know the distance between Earth and Mars but mb I misunderstand something
Could we use sound to synchronise the clocks? We have already measured the speed of sound, and it goes at the same speed both ways, so if we place two clocks 1km apart and a sound source in the middle, play a sound and when the clocks hear the sound, they start at the same time and synchronise perfectly. We could then probably measure the speed of a one way trip of light?
Lmk if this is false btw
This is great news. This means Earthlings can watch the latest movies and shows from outer space, but the aliens will have to settle for old radio and b&w tv. 👌🏼
Can we not use astronomy as evidence (not proof mind you) for the Einstein Convention? If you look very far into space you see past states of things because of the time it takes for their light to reach earth. So if C is different in different directions we should, when looking at objects that are the same distance from earth, see different moments in time depending on the direction. Thus, if we look in all directions and we see similar cosmological development (the presence and state of nebulae, stars and such) at the same distance in all directions it seems to me we have pretty good evidence that at least C is not hugely different in different directions.
It can never give certain proof but surely it seems like convincing evidence? Unless, of course, our knowledge of cosmological development is based on the Einstein Convention. And thinking about it it probably is.
The only way to tell is to go 65,000,000 ly away and get a really really high powered telescope look at earth and see if you can see the dinosaurs
i have a headache
While we are considering why our measurement of the speed of light might be wrong, and since it can only be measured with a mirror, do we know that mirrors reflect light instantaneously? Maybe there is a delay of a few nanoseconds in the mirror, meaning our accepted value of c might be even further off.
Me shae licht move fast
it's too fast to catch it
simple way to messure the speed of light have the beem of light start on clock and then travel x distance and then hit a senser that starts another clock then stop boths clocks at the exact same time and subtract clock a from clock b to get the time it ook light to travel x distance in conclusion we can measure the speed of light we just have not done so
Just measure the shape of the observable universe... Oh, you do it with light? It will appear like a sphere!? This is the most fascinating and brain-hurting video I've seen! Great Video! ❤
Why cant we just do the 2 way speed of light and divide it by 2?
2 years ago I stated that I may have a solution to test the speed of light... Is nobody at your channel even curious?
Im still confused as to why a third light coupdnt be used to test..though im sure theres a reason. A big giant light (bgl) amd two light trancievers (tc) move a 1.xxxxx light second away from each other. Bgl flashes and when they detect the flash each shoots a laser to the other. Each records the time dif between flash and laser reciept. if the intervals are different light has directional speed. and even if theyre in different frames it doesnt matter. 1 is at 1201. 2 is at 1202. as long as their distance isnt exactly one light second it still works. I seriously would like someone to explain why this wouldnt work because reality would literally have to rearrange itsels to stop it
Quantum entanglement: allows two objects to observe a change with no known limit to the distance… Find a Particle that’s position is changed with exposure to light… the time the light leaves vs the time the light changes the position of the particle…. Finds a 1 way trip of that time…
Why not measure the time between a timer sending a pulse through a kilometre long wire to itself? Am I dumb or something thinking about this idea or-
Why No One Has Measured The Speed Of Light ? Well, The speed of light in a vacuum, commonly denoted c, is a universal physical constant that is exactly equal to 299,792,458 meters per second. Then again, The universal physical constant is somewhat of a misnomer like the other universal constants, there is evidence and they remain controversial due to the fact they have been found to be different by others, some extremely minutely but not constant nonetheless.
Why limit yourself to two clocks that you need to separate? If you have infinite clocks in series that you start all at the same time, then fire a beam of light from one end to the other, couldn’t you see the delay between the first and last clock by looking at the clocks in between?
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