hodgepodge Posted September 23, 2011 Share Posted September 23, 2011 You can easily measure the speed of light yourself, it's not so fast as to be unmeasureable. With a couple of mirrors and a cheap laser, you can DIY like this: http://upload.wikimedia.org/wikipedia/commons/4/46/Speed_of_light_%28foucault%29.PNG Don't forget to put a stop watch on your shopping list Link to comment Share on other sites More sharing options...
PeteMorris Posted September 23, 2011 Share Posted September 23, 2011 Could anyone explain to a simpleton who managed a grade 5 cse in physics (and still doesn't know how), in words he might have a chance of understanding, how the speed of light is determined (in other words, how do we know how fast it goes?) I read somewhere (on the BBC I think) that it was something to do with the theory of relativity - if so, isn't a theory, by it's very definition, unproven? Gallileo first tried to measure it by setting up lanterns on nearby hills, and tried (in vain) to measure how long it took from one fella opening the lantern, and him seeing it, and then opening his latern. However it's much easier these days with satelites and space travel. Basically, the longer the distance the more accurate the measurement is. Here's the tail end of an article about it.....In the years that followed, as better equipment and techniques were developed, many other people were able to measure the speed of light more accurately. With the resources of today's technology, we can measure it to an incredibly high precision. For instance, astronauts have attached a mirror to a rock on the moon; scientists on earth can aim a laser at this mirror and measure the travel time of the laser pulse--about two and a half seconds for the round trip. (The idea behind this experiment is not so different from Galileo's, if you think about it...) And anyone who measures the speed of light, at any time, using any method, always gets the same result: just slightly less than 300,000 kilometers per second. Link to comment Share on other sites More sharing options...
barleycorn Posted September 23, 2011 Share Posted September 23, 2011 Could anyone explain to a simpleton who managed a grade 5 cse in physics (and still doesn't know how), in words he might have a chance of understanding, how the speed of light is determined (in other words, how do we know how fast it goes?) I read somewhere (on the BBC I think) that it was something to do with the theory of relativity - if so, isn't a theory, by it's very definition, unproven? I don't think you quite understand what is meant by theory in a scientific context. Maybe you should read this. http://badphysics.wordpress.com/2010/04/09/just-a-theory/ jb Link to comment Share on other sites More sharing options...
ampersand Posted September 23, 2011 Share Posted September 23, 2011 Thank you for all of those - I learnt more in the last 5 minutes than I did in a full school year of Physics lessons - anyone know where I can get a cheap laser and a stopwatch? (I once bought a "laser" at Ingoldmells market, but I don't think it would have reached the moon) So why was it concluded that nothing can travel faster than light? Link to comment Share on other sites More sharing options...
SiSiSi Posted September 23, 2011 Share Posted September 23, 2011 "Ye cannae change the laws of physics!" He used to annoy the Hell out of me! Every episode I hoped that Spock would give him a Vulcan death chop, or whatever it was that Vulcans used to do. Link to comment Share on other sites More sharing options...
PeteMorris Posted September 23, 2011 Share Posted September 23, 2011 Thank you for all of those - I learnt more in the last 5 minutes than I did in a full school year of Physics lessons - anyone know where I can get a cheap laser and a stopwatch? (I once bought a "laser" at Ingoldmells market, but I don't think it would have reached the moon) So why was it concluded that nothing can travel faster than light? That's the scientific theory that's just been brought into question. Einstein theorised that you would require an infinite amount of energy in order to travel beyond the speed of light. This new discovery brings into question that theory. (the theory of relativity, and special relativity) Link to comment Share on other sites More sharing options...
Alcoblog Posted September 23, 2011 Share Posted September 23, 2011 A good way is to bounce a laser off the moon and measure how long it takes to return. (1/2 a million miles) John X Erm ... I think your experiment may prove a tad inaccurate as the average distance from the Earth to the Moon is 233,900 miles. Link to comment Share on other sites More sharing options...
John X Posted September 23, 2011 Share Posted September 23, 2011 Erm ... I think your experiment may prove a tad inaccurate as the average distance from the Earth to the Moon is 233,900 miles. OK, just short of 1/2 a million miles! Pedant! John X Link to comment Share on other sites More sharing options...
Nagel Posted September 23, 2011 Share Posted September 23, 2011 Wasn't Einstein against quantum physics because it already allows for things to travel faster than the speed of light? Link to comment Share on other sites More sharing options...
Uptowngirl Posted September 23, 2011 Share Posted September 23, 2011 A policeman once claimed that I had exceeded it on my motorcycle. Link to comment Share on other sites More sharing options...
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