RMweb Premium Physicsman Posted April 25, 2015 Author RMweb Premium Share Posted April 25, 2015 So, as an analogy, if (say) Jeff, Henry V, an ancient Egyptian and Fred Flintstone were standing together by the buffers at platform 8 at KX, and say "The Plough" was situated at Edinburgh Waverley, would Fred Flintstone be seeing the light at say York, the ancient Egyptian at Grantham, Henry V at Stevenage and Jeff at the buffers at KX. And would it be the same light? Ok, we'll play your game using some assumed figures.... Let's assume that Alioth, the brightest star in The Plough, is 200 light years away from Earth. We'll also assume that Fred lived in 100000BC, the Egyptian in 3000BC, Henry in 1400AD and me in 2015. We are ALL stood at KX. Light from Alioth takes 200 years (by our clock) to reach the Earth. So the light each person saw left Alioth, respectively in: 100200BC, 3200BC, 1200AD and 1815AD. Each person sees light from the star that was emitted at a different time, but for each of them the light then took 200 years to travel from the star to Earth. It is not the same light for each. Jeff Link to post Share on other sites More sharing options...
RMweb Premium Sasquatch Posted April 25, 2015 RMweb Premium Share Posted April 25, 2015 Jeff, here's a question that might leave you stumped. If it were possible to travel at the speed of light or even faster (the closing velocity of two sources of light is twice that speed), when light speed is passed would it cause a huge flash (or a blackout or both, one from the travelers point of view and the other from the observers) as when the speed of sound is broken? I've always been baffled by the ideas that we're gonna find other life and alien visitors are here because if we could travel at one million miles an hour it would take nearly 7000 years to reach Proxima Centauri (which isn't even visible with the naked eye). The Voyager probes are traveling at about 38000mph and will take 182000 years to reach the distance of the Alpha-Beta-Proxima, Centauri system. It took us 5-6 times longer than that to put a hand axe on a stick! Hard to contemplate huh! Link to post Share on other sites More sharing options...
Peter Kazmierczak Posted April 25, 2015 Share Posted April 25, 2015 Thanks Jeff, So the light I might see tonight from the stars is the same that my great great grandparents saw, but not from generations further back than approx. 200 years. Link to post Share on other sites More sharing options...
RMweb Premium Physicsman Posted April 25, 2015 Author RMweb Premium Share Posted April 25, 2015 Thanks Jeff, So the light I might see tonight from the stars is the same that my great great grandparents saw, but not from generations further back than approx. 200 years. No. If you look at a star that's 200 light years away your eyes are responding to light that left the surface of that star 200 years ago, eg. April 25, 1815. If your great-grandfather looked at that same star in 1932, his eyes are responding to light that left the star in 1732, ie. 200 years earlier. We couldn't see the same light anyway because the instant the light photons are absorbed by the cell in your retina it's gone forever. Everyone sees their own batch of photons. Two people standing side by side, looking at the same star at the same instant will see light photons that left the star at exactly the same time, but from a slightly different place on the stars surface. Those photons travelled alongside each other until they were gobbled up by you and your friend's eyes. A way of visualising the situation is to think of the light photons as a continuous queue stretching from the star to us. You see the one at the front of the queue tonight, your son - who looks 20 years from now, sees the photon that's currently 20 light years behind tonights and won't get here for another 20 years. Hope that makes sense. Shaun, I'm thinking about your post. One thing to bear in mind, though, is that if we could travel at light speed then our own onboard clock wouldn't change and we wouldn't age. However, an external observer watching us make a journey would still record the passage of time by their own clock. So using our star Alioth, a clock moving at light speed would register zero passage of time for the 200 light year journey. An outside observer would start their clock and measure 200 years passage before the journey was complete. To give another example. The highest energy cosmic ray protons, moving at 0.9999 times the speed of light, perceive their journey time across the Milky Way galaxy to be around 30 seconds. The stationary, non-accelerating observer, on Earth would (if they lived long enough) measure the time for the crossing at just over 100,000 years. There is no evidence that faster than light travel (in a vacuum/space) is possible for material objects. However, particles can be fired through water, glass etc to travel faster in the material than light does (eg. light may travel at 0.9 x vacuum speed in glass, a proton from an accelerator may be fired at 0.95 x light speed in the same material - not breaking the "ultimate" top speed). When this happens, a "light boom"/"shock wave" is generated and makes the material glow a blue colour - called Cerenkov radiation. This is frequently observed in storage tanks adjacent to nuclear reactors. Jeff Link to post Share on other sites More sharing options...
Andrew P Posted April 25, 2015 Share Posted April 25, 2015 No. If you look at a star that's 200 light years away your eyes are responding to light that left the surface of that star 200 years ago, eg. April 25, 1815. If your great-grandfather looked at that same star in 1932, his eyes are responding to light that left the star in 1732, ie. 200 years earlier. We couldn't see the same light anyway because the instant the light photons are absorbed by the cell in your retina it's gone forever. Everyone sees their own batch of photons. Two people standing side by side, looking at the same star at the same instant will see light photons that left the star at exactly the same time, but from a slightly different place on the stars surface. Those photons travelled alongside each other until they were gobbled up by you and your friend's eyes. A way of visualising the situation is to think of the light photons as a continuous queue stretching from the star to us. You see the one at the front of the queue tonight, your son - who looks 20 years from now, sees the photon that's currently 20 light years behind tonights and won't get here for another 20 years. Hope that makes sense. Shaun, I'm thinking about your post. One thing to bear in mind, though, is that if we could travel at light speed then our own onboard clock wouldn't change and we wouldn't age. However, an external observer watching us make a journey would still record the passage of time by their own clock. So using our star Alioth, a clock moving at light speed would register zero passage of time for the 200 light year journey. An outside observer would start their clock and measure 200 years passage before the journey was complete. To give another example. The highest energy cosmic ray protons, moving at 0.9999 times the speed of light, perceive their journey time across the Milky Way galaxy to be around 30 seconds. The stationary, non-accelerating observer, on Earth would (if they lived long enough) measure the time for the crossing at just over 100,000 years. There is no evidence that faster than light travel (in a vacuum/space) is possible for material objects. However, particles can be fired through water, glass etc to travel faster in the material than light does (eg. light may travel at 0.9 x vacuum speed in glass, a proton from an accelerator may be fired at 0.95 x light speed in the same material - not breaking the "ultimate" top speed). When this happens, a "light boom"/"shock wave" is generated and makes the material glow a blue colour - called Cerenkov radiation. This is frequently observed in storage tanks adjacent to nuclear reactors. Jeff I agree Jeff, :no: Link to post Share on other sites More sharing options...
RMweb Premium Sasquatch Posted April 25, 2015 RMweb Premium Share Posted April 25, 2015 Makes sense! Water slows the photons correct! Looking at your feet in the pool the light appears bent. Anything moving fast than the light around it would reflect he light faster, thus appearing brighter than the existing photons? Mind boggling! Link to post Share on other sites More sharing options...
RMweb Premium Physicsman Posted April 25, 2015 Author RMweb Premium Share Posted April 25, 2015 On a more mundane, but probably more interesting note, today's weather front passed through Willington leaving behind a crystal clear evening sky. I've just been outside looking at the Moon, Venus and the planet Mercury, twinkling about 8 degrees above the WNW horizon. Blackbirds singing, no breeze. Just beautiful. Jeff Link to post Share on other sites More sharing options...
RMweb Premium Sasquatch Posted April 25, 2015 RMweb Premium Share Posted April 25, 2015 Sounds wonderful Jeff, I miss the black birds! Link to post Share on other sites More sharing options...
robmcg Posted April 26, 2015 Share Posted April 26, 2015 Hi Rob, The Jubilee does it for me (check out my avatar!), although we didn't have any on the roster at Hurlford 67B, we saw plenty in for service or repair as they were well used on the Nith valley line! Thanks for sharing the pics, I actually had a couple of footplate rides on the Standard tanks which replaced some of the 2Ps we had - real luxury in the cab by comparison but oddly, the drivers seemed to prefer the more archaic loco! Kind regards, Jock. Thanks Jock, the relationship between man or woman and machine certainly is interesting, especially when its character is so important in a working day. Here are some more portraits of my locomotive-de-jour the Fowler tank with long travel valves.... photons notwithstanding Think of the LMS (2308 this time) banking on Shap and it all comes together... not sure what shed 42322 was at. I'm repeating myself but the paintwork on the LMS version in particular is stunning. Rob Link to post Share on other sites More sharing options...
robmcg Posted April 26, 2015 Share Posted April 26, 2015 ..and today I did the pic below, recalling how some of the most dramatic and spirited steam performances came from stop-start semi-fast class one trains, often they had very tight scheduling. LMS 2-6-4T 4P No. 2308 on one such train, with atmospheric style... Link to post Share on other sites More sharing options...
robmcg Posted April 27, 2015 Share Posted April 27, 2015 and running light over a West Yorkshire bridge... (I succumbed and bought DCC-ready 2308 today...) The crew will be staying warm. I like the basic pic too... Link to post Share on other sites More sharing options...
RMweb Premium southern42 Posted April 27, 2015 RMweb Premium Share Posted April 27, 2015 Thanks Jock, the relationship between man or woman and machine certainly is interesting, especially when its character is so important in a working day. Here are some more portraits of my locomotive-de-jour the Fowler tank with long travel valves.... photons notwithstanding Think of the LMS (2308 this time) banking on Shap and it all comes together... not sure what shed 42322 was at. 2308_LMS_Fowler_2a_r1200.jpg 42322_BR_Fowler_portrait1_1ab_r1200.jpg 42322_BR_Fowler_portrait5_2abc_r1200.jpg I'm repeating myself but the paintwork on the LMS version in particular is stunning. Rob You can look it up here, Rob. Just put the number in the search box. http://www.brdatabase.info/ Link to post Share on other sites More sharing options...
RMweb Premium Physicsman Posted April 27, 2015 Author RMweb Premium Share Posted April 27, 2015 I've been looking at a number of threads over the last couple of days, in areas right across the Forum. Some of them are well-"policed" - often needing no control at all. Some, from my point of view verge on anarchic and most-certainly disrespectful. One thing in particular has been irritating me: When an ongoing discussion/theme is "turned" by the interruption of a totally different subject - WITHOUT any kind of "pardon me" lead in. Strikes me as pig ignorant that some people just HAVE to get their own viewpoint in, even if it's at a tangent to what's ongoing in the thread. Have others noticed this? Rant over. Jeff Link to post Share on other sites More sharing options...
RMweb Gold Anotheran Posted April 27, 2015 RMweb Gold Share Posted April 27, 2015 Oh dear, I suspect my interruption of the females in modelling discussion with my spotting of the tender on the M6 was something like that. It just seemed a suitably amusing thing to post in the lounge, so I posted it as soon as I got home with no thought as to the surrounding conversation. So here's a very belated "pardon me" for the quick aside... but it really was very shiny... Neil Link to post Share on other sites More sharing options...
freebs Posted April 27, 2015 Share Posted April 27, 2015 I saw an Ostrich this morning... Link to post Share on other sites More sharing options...
RMweb Premium Physicsman Posted April 27, 2015 Author RMweb Premium Share Posted April 27, 2015 Oh dear, I suspect my interruption of the females in modelling discussion with my spotting of the tender on the M6 was something like that. It just seemed a suitably amusing thing to post in the lounge, so I posted it as soon as I got home with no thought as to the surrounding conversation. So here's a very belated "pardon me" for the quick aside... but it really was very shiny... Neil No, Neil, you were terribly excited and wanted to tell us your news. No problem with that! Actually, Lee - it was an emu (bird, that is - not EMU!!!!!). It was pulling Rod Hull's son behind it and Michael Parkinson was taking cover! Sorry folks, I'm not trying to make any of you feel guilty. It's just that there are some stridently ignorant people who contribute to the Forum as a whole and it annoys me. So much so that I'd even consider leaving the whole thing alone. Lunesters are generally categorised by having a good sense of humour, wide-range of interests and an empathy with others. Jeff Link to post Share on other sites More sharing options...
freebs Posted April 27, 2015 Share Posted April 27, 2015 I think I must just be lucky to follow the "good" threads Link to post Share on other sites More sharing options...
RMweb Gold Anotheran Posted April 27, 2015 RMweb Gold Share Posted April 27, 2015 Lunesters are generally categorised by having a good sense of humour, wide-range of interests and an empathy with others. I disagree with everything you say in that sentence. Link to post Share on other sites More sharing options...
RMweb Gold Donw Posted April 27, 2015 RMweb Gold Share Posted April 27, 2015 No. If you look at a star that's 200 light years away your eyes are responding to light that left the surface of that star 200 years ago, eg. April 25, 1815. If your great-grandfather looked at that same star in 1932, his eyes are responding to light that left the star in 1732, ie. 200 years earlier. There is no evidence that faster than light travel (in a vacuum/space) is possible for material objects. However, particles can be fired through water, glass etc to travel faster in the material than light does (eg. light may travel at 0.9 x vacuum speed in glass, a proton from an accelerator may be fired at 0.95 x light speed in the same material - not breaking the "ultimate" top speed). When this happens, a "light boom"/"shock wave" is generated and makes the material glow a blue colour - called Cerenkov radiation. This is frequently observed in storage tanks adjacent to nuclear reactors. Jeff Now that is something I haven't heard . The blue glow is caused by the speed exceeding that of light in the medium and not just the particle's presence The light arrivial is like a conveyor belt all the lumps (photons) are travelling at the same speed Don Link to post Share on other sites More sharing options...
RMweb Gold PeterBB Posted April 27, 2015 RMweb Gold Share Posted April 27, 2015 Hi Guys, Just in case you do not know Happy Birthday Andy . If he hadn't retired already he would have done so today. Andy we look forward to your next shunting blog. Peter and the gang! Link to post Share on other sites More sharing options...
RMweb Premium Physicsman Posted April 27, 2015 Author RMweb Premium Share Posted April 27, 2015 Well said, Peter. Some of us have already been privy to details regarding what he's going to spend his extra pension-income on! We promised not to tell Dee!.... (Right Andy, HOW MANY class 57s was it???!!) Jeff Link to post Share on other sites More sharing options...
emt_911 Posted April 27, 2015 Share Posted April 27, 2015 Thanks Peter Happy Birthday Andy :locomotive: Link to post Share on other sites More sharing options...
Andrew P Posted April 27, 2015 Share Posted April 27, 2015 Hi Guys, Thanks for the Birthday wishes Peter and Jeff. EDIT = To add Duncan. Cheers Guys. PENSION, according to the letter from the DWP I will be about £140 a Month worse off now than I have been. Don't know how, but that's the way it works with a Joint Pension apparently. So no 57's and selling the rest to fund my Retirement. I have purposely kept out of the Sky at night debate as I know sweet sod all about it, but admire it greatly. I didn't want to start another discussion as it would as Jeff has said, have interrupted the most impressive information that has come from many learned Scholars amongst us. Re Women modellers, there are some really good ones like Maggie Gravett and Polly for example but they are exceptions to the rule. Maybe Jason can prove us all wrong in 15 years. I wont interrupt with pics of my bare Bu* baseboards again, ahhaha Link to post Share on other sites More sharing options...
RMweb Premium southern42 Posted April 27, 2015 RMweb Premium Share Posted April 27, 2015 Happy Birthday Andy Link to post Share on other sites More sharing options...
RMweb Gold ChrisN Posted April 27, 2015 RMweb Gold Share Posted April 27, 2015 Andy, Happy Birthday, well what's left of it. Link to post Share on other sites More sharing options...
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