Timeline for Home experiments to derive the speed of light?
Current License: CC BY-SA 3.0
20 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Feb 27, 2017 at 18:30 | comment | added | Yashas | I removed my downvote but this method gives unpredictable answers. Someone might measure the speed to be 100 miles per second too, someone else might measure it to be 10,000 miles per second. | |
| Feb 27, 2017 at 18:24 | history | edited | DanielSank | CC BY-SA 3.0 |
Point out that this is a lower bound
|
| Feb 27, 2017 at 18:18 | comment | added | Frédéric Grosshans | @YashasSamaga: These fibres are single-mode fibres. In such fibres, the usual image of a “bouncing ray of light” is wrong, and light indeed propagates along the fibre. | |
| Feb 27, 2017 at 18:16 | comment | added | Frédéric Grosshans | @YashasSamaga : Of course the packets don’t take the shortest paths and errors are induced by the computers (avoid wireless). It might be seen as a lower bound. But, having the right order of magnitude with a cheap (basically free) home experiment like this is far from unacceptable. It’s way better than Galieo’s 138 bound, but indeed worse than Rømer’s 1675 estimate. | |
| Feb 27, 2017 at 18:14 | comment | added | Yashas | Moreover, the waves in fiber optics aren't moving in a straight line. They are bending. | |
| Feb 27, 2017 at 18:03 | comment | added | Yashas | -1 You need to study networking. The packets don't take the shortest path. It goes through hundreds of routers before reaching the destination. This isn't even an approximate. The computers are a lot slower. An error of 50% is unacceptable. | |
| Jan 23, 2017 at 10:18 | comment | added | AndaluZ | The experiment will fail here. When sending a ICMP package, it goes through several steps, each involving in processing the package. A modem that converts digital signal into modulated wave signals to transfer the data. Than it passes through several routers and switches and computers each processing the data, depending on concurrent connections, it take more or less time. So this won't work. | |
| Apr 23, 2011 at 20:13 | comment | added | Martin Beckett | @Frédéric - although to be fair, he only had dialup | |
| Nov 19, 2010 at 11:44 | comment | added | Frédéric Grosshans | @sigoldberg1 : OK, but this lower bound is way better than Galileo's. | |
| Nov 19, 2010 at 3:51 | comment | added | sigoldberg1 | But suppose we didn't know the correct result, and got various different results with different cables. We would have to be somewhat careful before declaring an answer "final" | |
| Nov 18, 2010 at 17:57 | comment | added | Frédéric Grosshans | @sigoldberg1 : yes, but a lower bound happening to be within 33% of the correct value. If done with fiber, admitting the fiber to be glass, one can then easily measure the index of refraction of glass to be 1.5 and we have the correct result... | |
| Nov 18, 2010 at 17:24 | comment | added | sigoldberg1 | +1 for referencing "Speed of light measurement using ping" at arxiv.org/abs/physics/0201053 , although as a real experiment this would likely only give a lower bound to c. | |
| Nov 18, 2010 at 11:22 | comment | added | Joe Fitzsimons | @Frédéric: At each hop there is routing overhead. When a packet expires at that hop the processing is different. | |
| Nov 18, 2010 at 11:08 | comment | added | Frédéric Grosshans | @Joe : If I understood traceroute correctly, the overhead is propagated to the next node. I'm more afraid of statistical fluctuations . | |
| Nov 18, 2010 at 10:58 | comment | added | Joe Fitzsimons | @Frédéric: I'm not sure you can simply take the difference of two times in traceroute. It neglects the processing overhead which may be substantially different at each node. | |
| Nov 17, 2010 at 17:43 | comment | added | nibot | Reminds me of Cliff Stoll's book, the Cuckoo's Egg, in which he (an astronomer) uses the ping time to estimate how far away an intruder in the computer system might be. | |
| Nov 17, 2010 at 17:25 | history | edited | Frédéric Grosshans | CC BY-SA 2.5 |
added 238 characters in body
|
| Nov 17, 2010 at 17:13 | comment | added | Frédéric Grosshans | Surprisingly: the Paris-London-Amsterdam traject bove (8-9-10) seems pretty accurate : roughly 3ms, i.e 300 km each, which is the real distance | |
| Nov 17, 2010 at 10:52 | comment | added | Pratik Deoghare | Yes. This could work :) I have done delay calculations in my Computer Networks course. But never thought about as a way to calculate the speed of light. | |
| Nov 16, 2010 at 11:58 | history | answered | Frédéric Grosshans | CC BY-SA 2.5 |