Why No One Has Measured The Speed Of Light

My bank uses the same theory, but vice versa. When the money leaves my debit card, it goes really fast. When something is to be repaid, it takes much longer.

Light: "My speed is immeasurable, and my time is ruined"

I am an engineer and was working on time synchronization between two devices on the same network. We encountered cases where network delay from A to B is higher than from B to A and such cases resulted in inaccurate synchronization. I was working on solving this problem and after watching your video I realized it’s essentially the same concept- sending signals from earth to mars is like sending network packets from A to B. So the conclusion was, without the help of any external device it’s impossible to accurately sync time! Thanks a lot for your video :))

If the speed of light were different in different directions, wouldn’t we see more distant stars in that direction since the light was able to travel to us faster from that direction? Also Earth and Mars don’t remain traveling parallel like that so at a certain point, mars would be sending messages in a different direction and make the speed different.

This was a very fun present to unwrap. When you called me and told me to turn the camera on I knew something weird was going to happen and you certainly delivered. As long as I’ve known you Derek you’ve been destroying assumptions. Thank you for this friendship. It’s certainly enjoyable from my perspective.

Great video. Despite getting a physics degree and teaching physics for years, I never came across this or thought about it. I was treating the video mostly as a 'fun to think about' sort of video, but your point at the end is really intriguing.

Wouldn’t red shift be different in different directions if light traveled faster in one direction than another? Unless we make another huge assumption that the universe is lopsided?

Derek, you have blowed my mind today. Great video and even greater attitude into science mystery.

"So someone has measured the speed of light...or have they?" Huge Vsauce moment right there

"We've invented an FTL drive but you can only turn left."

My kids and I love your channel and I love the conversations induced afterwards. This video covers a topic that I’ve wondered about for quite some time. How can an object like the andromeda galaxy that is 200,000 light years across “appear” as a single object instead of a smear? Especially since it is also moving through space? These are the things my sons and I ponder. Thanks again for the great content!

Wouldn't redshift and blueshift disprove the c/2 and ∞. I mean sure we can't know if it's the same in both directions but I guess we can know that it cannot be instantaneous. Or if it doesn't work this way please explain why.

My real takeaway is that two clocks, regardless of precision, will never be truly synchronized. This explains why I am frequently late.

"so someone has measured the speed of light... or have they?" Hey, Vsauce... Michael here

What about using quantum entanglement to measure the speed of light? Fire the light, it sets off the entangled particle, and when the light reaches the end, the entangled particle there would immediately send the info back to the first one.

Another idea… set your 2 clocks at the vertices of an equilateral triangle, and a light source at the 3rd vertex. The light source sends out a single light burst traveling in a spherical wavefront which initializes the 2 clocks to t=0 & starts the experiment. Clock A immediately sends out another spherical light burst which travels to both Clock B, the receiver, and Clock C, the initializer. Both clocks B & C record the time from initialization to the receipt of clock A’s burst, & then clock B immediately sends out its burst to clocks A & C upon receipt of burst A. Both A & C record this burst from B. Assuming you have all your light sources & clocks precisely positioned, & other factors such as electrical paths from the sensors to the clocks are the same & accounted for, clock A will measure 2c, clock B will measure 1c, and clock C will measure 2c & 3c. If all the c measurements are the same within a small degree of error, then this is your 1-way speed of light within that error. Of course to verify, you’d rerun the experiment again with B sending out the first burst after initialization so that clock A measures 1c in the other direction, & you could repeat the experiment 4 more times with each vertex being initiator, sender, & responder in turn and in both directions. Then you summarize all the data, calculate the maximal %error, & this would be the limit, within a calculated level of confidence, say 99.99999%, that the speed of light could vary without us knowing it. QED.

I swear this channel is a gold mine for educational and entertaining content

Should have wrote this in my physics exams, "It is neither a supposition, nor a hypothesis, but a stipulation that I can make of my own free will"

Fascinating as are all of your videos even though I am no Physicist but just a humble sailor and safari guide. I think I better have a drink now or sleep is out of the question tonight. Thank you

What about Ole Roemer measuring Io transiting Jupiter? Way back in 1676 he wanted to make a celestial clock, and couldn't because Io appeared to slow down and speed up. He had the insight that the problem was the speed of light combined with the changing. distance because of the orbits of Earth and Jupiter. Huygens helped out with the math to get a pretty good approximation. How's about you repeat the experiment?