Alright so I’ve heard of this annoying thing called the speed of light and all, but still the above seemed like a cute quote. Now given that one isn’t going to be going faster than the speed of light, does that necessarilly mean that one can’t be going fast enough to distort light? Is there any vehicle we’ve invented capable of going fast enough to distort our perception of light sufficiently to make it seem like a different color?
You’d have to be going at relativistic speeds, which, IIRC, are upwards of 90%+ the speed of light. So pick a car that does at least 170,000 miles per second, and you’ll notice some blue shift, I suppose.
neato!
After a good deal of googling I still can’t figure out just what relativistic speeds are? Why is it that this anomoly would occur?
Its’ called doppler shift.
“Relativistic” refers to speeds that approach the speed of light, i.e. your speed relative to the speed of light.
Why does blue shift happen? For some of the same reasons that the Doppler effect happens, i.e. light will look differently depending on your speed in the same way a car sounds differently as it approaches, passes, and moves away from you. This analogy is simplistic and will probably be panned, but gives you an easy way to think about.
Ultimately, the whole color shift thing occurs because the speed of light is not a constant. It changes depending on how fast you are going. I recall that time is the actual constant but then I also recall reading something indicated that time isn’t constant either.
This is all clear blue right?
cjfinn
Actually, you’ll need to search for the relativistic doppler shift. The plain old doppler shift generally refers to sound waves in air.
It’s like a Doppler Shift. From howstuffworks.com’s article on relativity:
To sum, the frequency of the light wave (or sound wave) will change if you (or the source) is moving towards or away from the other.
If you drove very, very fast at a red light, the color would shift towards blue as Qadgop said. Similarly, if the red light were to move very, very fast towards you, the color would shift in the same manner.
This is incorrect. The speed of light is constant, no matter how fast one is moving–it is in fact one of the few true constants in the universe. The fact that the speed of light is constant is what causes time to be not constant.
try this site: http://www.arachnoid.com/sky/redshift.html
But, I thought the light shift would be red if you’re headed towards a light source and blue if away,no?
/hijack
Also, is it true that you can see these effects star-gazing?(stars twinkling from white/blue or white/red)
/lojack
No, it’s red for away and blue for toward. Although these things are very useful in astronomy, you will not see the effect visually in stars in our galaxy; this sort of thing is measured with a spectrometer.
One of my old physics texts had a problem that used this idea. A motorist stopped for speeding appeals because the blueshift made the light look green to him. The judge drops the light-running charge and immediately charges him with speeding, one dollar per MPH over the speed limit he was going at the tmie. The problem was to figure out what his fine was. IIRC it was on the order of $100 Million.
This page describes the very situation in the OP, and you only need to be going about .17c to observe red as green.
The formula for the frequency shift is :
f[sub]obs[/sub] / f[sub]0[/sub] = [ 1 / (1 + v/c[sub]0[/sub]) ] * sqrt ( 1 - v / c[sup]2[/sup] )
where f is the frequency observed, f[sub]0[/sub] is the frequency emitted, and v is the speed of the observer or transmitter (the formula can be restated with both moving). c[sub]0[/sub] is the speed of the wave in the medium ( since this applies to any wave, such as sound), but c is the universal constant speed of light in vacuum.
So for low-speed waves like sound or water, the relativistic correction term is small (v/c is small), but for light, c[sub]0[/sub] => c and the formula simplifies to the one shown in the linked page.
Hmmmm, panamajack’s link says that the guy was driving at 31875 MPH, but 0.17c is actually 114,004,827 MPH, I think. But it’s still pretty cool.
The 114 million MPH is right; it makes it 31,875 miles per second, an error on their part.
I made a mistake in my formula, too : the sqrt term should have (v/c)[sup]2[/sup], not v/(c[sup]2[/sup]).
I remember a comic strip (for a college newspaper) that showed a guy taking a test. The question was what the Doppler Effect was; he wrote, “The Doppler Effect is what makes the lights on cars look white when they’re coming toward you, and red when they’re moving away.”