The speed of light
Discussion
Following on from reading these threads:
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
http://pistonheads.com/xforums/topic.asp?h=0&f...
I understand the fact that it took a while before light formed, which is why we can look back at an older part of the Universe but before reading the threads I would have also said, us also moving/expanding was also a factor. If we're moving apart from the stars we're looking back at, it would take longer still for the light from those stars to reach us, as where moving away as the light is travelling towards us. This meaning we can look back further still, than what we could if we were just stationary. Put it this way, if car A (earth) is travelling at 55mph and Car B (light from a star) is travelling at 60mph it's going to take car B longer to get to car A, than what it would do if Car A was stationary.
However this doesn't seem to be the case with light, as Einstein seems to have explained that the speed of light is constant to all observers. Could someone please explain to me why this is.
From the bit of research I've done the Doppler effect is mentioned too. I mean, I know what that is when it comes to sound, you get that distinctive noise of a race car approaching you and then trailing off when it's gone passed. However I can't understand how light and seeing something does the same thing.
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
http://pistonheads.com/xforums/topic.asp?h=0&f...
I understand the fact that it took a while before light formed, which is why we can look back at an older part of the Universe but before reading the threads I would have also said, us also moving/expanding was also a factor. If we're moving apart from the stars we're looking back at, it would take longer still for the light from those stars to reach us, as where moving away as the light is travelling towards us. This meaning we can look back further still, than what we could if we were just stationary. Put it this way, if car A (earth) is travelling at 55mph and Car B (light from a star) is travelling at 60mph it's going to take car B longer to get to car A, than what it would do if Car A was stationary.
However this doesn't seem to be the case with light, as Einstein seems to have explained that the speed of light is constant to all observers. Could someone please explain to me why this is.
From the bit of research I've done the Doppler effect is mentioned too. I mean, I know what that is when it comes to sound, you get that distinctive noise of a race car approaching you and then trailing off when it's gone passed. However I can't understand how light and seeing something does the same thing.
Edited by TheTurbonator on Sunday 17th June 12:01
TheTurbonator said:
Following on from reading these threads:
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
http://pistonheads.com/xforums/topic.asp?h=0&f...
I understand the fact that it took a while before light formed, which is why we can look back at an older part of the Universe but before reading the threads I would have also said, us also moving/expanding was also a factor. If we're moving apart from the stars we're looking back at, it would take longer still for the light from those stars to reach us, as where moving away as the light is travelling towards us. This meaning we can look back further still than what we could if we were just stationary. Put it this way, if car A (earth) is travelling at 55mph and Car B (light from a star) is travelling at 60mph it's going to take car B longer to get to car A, than would it would do if Car A was stationary.
However this doesn't seem to be the case with light as Einstein seems to have explained that the speed of light is constant to all observers. Could someone please explain to me why this is.
From the bit of research I've done the Doppler effect is mentioned too. I mean, I know what that is when it comes to sound, you get that distinctive noise of a race car approaching you and then trailing off when it's gone passed. However I can't understand how light and seeing something does the same thing.
The doppler effect is caused by variations in the FREQUENCY of the waves. It doesn't matter whether the waves are sound waves or light waves.http://www.pistonheads.com/gassing/topic.asp?h=0&a...
http://pistonheads.com/xforums/topic.asp?h=0&f...
I understand the fact that it took a while before light formed, which is why we can look back at an older part of the Universe but before reading the threads I would have also said, us also moving/expanding was also a factor. If we're moving apart from the stars we're looking back at, it would take longer still for the light from those stars to reach us, as where moving away as the light is travelling towards us. This meaning we can look back further still than what we could if we were just stationary. Put it this way, if car A (earth) is travelling at 55mph and Car B (light from a star) is travelling at 60mph it's going to take car B longer to get to car A, than would it would do if Car A was stationary.
However this doesn't seem to be the case with light as Einstein seems to have explained that the speed of light is constant to all observers. Could someone please explain to me why this is.
From the bit of research I've done the Doppler effect is mentioned too. I mean, I know what that is when it comes to sound, you get that distinctive noise of a race car approaching you and then trailing off when it's gone passed. However I can't understand how light and seeing something does the same thing.
Frequency depends on how often the wave passes the observer. Since all light waves are travelling at the same speed, i.e. 186,000 miles per second, the doppler shift is not caused by differing speeds of light waves. It is caused by differing gaps between the peak and the roughs of the light wave. In other words, high frwequency waves will be bunched closer together. Lower frequency waves will be spread further apart.
But thay are all travelling at the same speed, no matter what the frequency is.
I am busy today, so have only a little time, Eric has answered your question adequately.
But there is in your post a clue that perhaps you don't fully appreciate what exactly 'relativity' means.
You need really to read up on that to properly grasp its true meaning, because although the word has become common parlance it is remains misunderstood at its core by almost all who use it outside of the discipline.
I am always seeking ways to convey the truth in ways that are easily assimilated, I'll use the following one to convey just how relativity works... I've only just thought of it so bear with me.
Two people stand 20 mtrs apart, they each have a 1 mtr long ruler and they both hold them up vertically,each knows that the other ruler is one meter long yet to each other the other ruler is much shorter, we call this perspective and we are used to it, unless you are in a Father Ted sketch.
Time has perspective too, but it is so peculiar that we call it 'relativity' to distinguish it.
All four dimensions have perspective, we just call the one in time a different name because it is so odd, if the xyz dimension had the same level of perspective of time we would be able to see detail with the naked eye of the surface of all the planets around us and probably be able to see planets orbiting nearby suns.
Not a perfect analogy but it does convey a greater truth.
Hope that helps.
Gene.
But there is in your post a clue that perhaps you don't fully appreciate what exactly 'relativity' means.
You need really to read up on that to properly grasp its true meaning, because although the word has become common parlance it is remains misunderstood at its core by almost all who use it outside of the discipline.
I am always seeking ways to convey the truth in ways that are easily assimilated, I'll use the following one to convey just how relativity works... I've only just thought of it so bear with me.
Two people stand 20 mtrs apart, they each have a 1 mtr long ruler and they both hold them up vertically,each knows that the other ruler is one meter long yet to each other the other ruler is much shorter, we call this perspective and we are used to it, unless you are in a Father Ted sketch.
Time has perspective too, but it is so peculiar that we call it 'relativity' to distinguish it.
All four dimensions have perspective, we just call the one in time a different name because it is so odd, if the xyz dimension had the same level of perspective of time we would be able to see detail with the naked eye of the surface of all the planets around us and probably be able to see planets orbiting nearby suns.
Not a perfect analogy but it does convey a greater truth.
Hope that helps.
Gene.
Gene Vincent said:
But there is in your post a clue that perhaps you don't fully appreciate what exactly 'relativity' means.
You need really to read up on that to properly grasp its true meaning, because although the word has become common parlance it is remains misunderstood at its core by almost all who use it outside of the discipline.
You're probably right, I don't. Is there any books you could recommend or anyone could recommend that would explain all this.You need really to read up on that to properly grasp its true meaning, because although the word has become common parlance it is remains misunderstood at its core by almost all who use it outside of the discipline.
I like to sit down with a book or books until I understand something. I suppose I need to start with one that explains Einstein's theories and the behaviour of light and the universe.
Edited by TheTurbonator on Sunday 17th June 13:25
wormburner said:
Read Hawking's A Brief History of Time. It is a completely wonderful book, bringing some real 'proper' science to life, without patronising, dumbing-down or over-complicating.
Masterpiece, and one of the best books I've ever had the privilege to read.
You are probably the only person on the planet, apart from Hawking himnsself, who understood it.Masterpiece, and one of the best books I've ever had the privilege to read.
Eric Mc said:
wormburner said:
Read Hawking's A Brief History of Time. It is a completely wonderful book, bringing some real 'proper' science to life, without patronising, dumbing-down or over-complicating.
Masterpiece, and one of the best books I've ever had the privilege to read.
You are probably the only person on the planet, apart from Hawking himnsself, who understood it.Masterpiece, and one of the best books I've ever had the privilege to read.
Also give A Breifer Historty of time a try ,updated and a little less Academic
UKIP voters will do better with "Where's Wally?"
Eric Mc said:
wormburner said:
Read Hawking's A Brief History of Time. It is a completely wonderful book, bringing some real 'proper' science to life, without patronising, dumbing-down or over-complicating.
Masterpiece, and one of the best books I've ever had the privilege to read.
You are probably the only person on the planet, apart from Hawking himnsself, who understood it.Masterpiece, and one of the best books I've ever had the privilege to read.
I haven't encountered a better attempt to make astrophysics accessible to muggles like me though.
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