If I stand in a small room and rotate a laserpointer 360 degrees in 1 second, the dot of light on the walls covers a distance of 30 metres, ie 30 metres per second. If I then go into a bigger room and do the same thing, the dot of light on the wall covers a greater distance of 100 metres, ie 100 metres per second. If the speed of light is 300 million metres per second, and I stood in a room who's walls were 47'746'483 metres away in all directions and rotated the laserpointer 360 degrees in 1 second, would the dot of light on the wall break the speed of light? , ie, would the dot on the wall travel more than 300'000'000 metres per second?
(maths; circumference of a cirle is 'diameter x pi'. If circumference is 300'000'000 then 300'000'000 divided by pi, ie, 3.14159265 = diameter of 95492965.964254. Diameter is 2 x radius, so radius is 95492965.964254/2 = 47746482.982)
2006-07-04 13:11:34 · 20 answers · asked by Anonymous in Science & Mathematics ➔ Other - Science
Quote; "it would travel the speed of light because it is light". With the maths I have supplied, the dot of light would have to travel faster than the speed of light in order for the dot to make it back to the original position after the 360 turn. If it cannot go faster than the speed of light, how long would the dot take to travel the distance?
2006-07-04 13:32:25 · update #1
no
2006-07-04 13:15:29 · answer #1 · answered by Anonymous · 0⤊ 0⤋
First of all, the only real speed is the one of the laserpointer - 1 rps (revlution per second). The light, in described case, travels in many ways: from the pointer to the wall, from the wall to the watcher's eye and around the room. Since it travels so many distances, it may appear reasonable to assume that it travels at the speed of light, or even faster.
BUT, closing to the speed of light over the wall, You will notice the DELAY, i.e. the discontinuity between the laser beam at it's source and it's reflection on the wall. Since there would be almost 48000 km from the source to the "wall", the delay is inevitable and it would look like the point is slowing down, instead of reaching the speed of light.
Due to the "laziness" of the eye, only a line could be seen on the wall. That's because, at such a distance, a point would strech to a line, which has bigger length, which would cause the effect of delay.
By use of vector analysis, it can be seen that the time delay produces lower speed than the speed of light (longer time for the same trajectory). Thus the fact that the speed of light can't be reached in macroscopic world is proved.
And stop thinking about stupid things.
2006-07-10 02:32:50 · answer #2 · answered by Vlada M 3 · 0⤊ 0⤋
Think of it this way: observer stands at the centre of a very large room. He projects a spot on a very distant curved wall C/2pi metres away. The light he observes on the wall takes a certain time to leave the projector and get back to the observer. In fact C/pi (where C= speed of light in seconds), i.e. something a little less than a third of a second. This would be large enough to result in an observable delay, between switching the projector and receiving the light back from the wall. But I think that this is besides the point.
You then start the projector rotating. Assuming it would be possible to see the reflected light, what you would probably observe is a stripe of light around the wall (caused by persistence of vision), which would cut off about 1/3 of a second after the projector went out. You would in my view not be able to observe a point moving faster than C, even though theoretically it would seem to have to have moved faster than C.
The question raises another question, who would be able to observe the point of light moving faster than C?
And finally what is it that moves faster than C?
Each observer around the wall would see a sudden extremely brief flash of light 1/C secs long.
Only somebody in a spaceship travelling close to the speed of light could keep up with the point, but the person on board the spaceship would experience a relative slowing of time. So this observer too would only experience seeing the light for one second of time.
Hope this helps, and pleases the teacher.
2006-07-04 13:48:59 · answer #3 · answered by Augusta B 3 · 0⤊ 0⤋
In a circular room with a radius of 47 million meters, the dot on the wall would not be continuous. The laser pointer beam would be moving in a circle faster than the photons can strike the wall so relativity would come into play.
2006-07-04 14:23:17 · answer #4 · answered by jeff g 1 · 0⤊ 0⤋
No matter how big the room was,the speed of light would remain constant at 186,000 miles per second,or as you say 300,000,000 metres per second.This is its fastest speed so it would be impossible to go faster,and besides,you would never find a room with walls over 47 million metres apart
2006-07-04 13:20:21 · answer #5 · answered by Mick H 3 · 0⤊ 0⤋
The dot of light on the wall isn't travelling at all; the dot itself does not have physical existence. The light is travelling from the laserpointer to the wall, then reflecting off the wall. Our language refers to the dot on the wall as a convenient way of saying "all the photons from the laserpointer that are bouncing off the wall at any time."
2006-07-04 13:16:51 · answer #6 · answered by Tim 4 · 0⤊ 0⤋
look at it this way
imagine a fairground ride, a carousel. if it was sufficiently large enough, the centre could be travelling at a sensible speed, but someone on the outer edge would be travelling at what could be calculated as being the speed of light.
mathematically they could exceed the limit. but in reality? noone will really know what will happen until we are able to accelerate something up to the speed of light, with the potential to go past it.
and as for the speed of light being an absolute maximum? imagine you are in a car going a the speed of light. then you turn on your headlights. what speed would the light waves/photons coming out of the lights be going? twice the speed of light?
to answer your question, mathematically, yes it does. but is that how the universe operates? we'll have to wait and see.
2006-07-05 08:03:48 · answer #7 · answered by top_cat_1972 2 · 0⤊ 0⤋
As the radius of the reflector wall increases, the report (reflection that you see) will start to lag the angle of the laser pointer as you rotate. As the wall recedes, the dot will continue to increase this lag, eventually, the report will not bear any correlation to the pointer. Nothing will exceed the speed of light in free space.
Sorry, you did not invalidate all of currently accepted physics.
2006-07-04 13:39:54 · answer #8 · answered by none2perdy 4 · 0⤊ 0⤋
No. The light would not reach the wall until a latter point in time. Just because you are rotating it at that speed does not mean that the light is constantly connecting with the wall.
2006-07-04 13:18:11 · answer #9 · answered by pw 2 · 0⤊ 0⤋
technically the "dot" would break the speed of light, however it's not really a dot... its a beam of light. Its only until the beam hits somethin gsolid that you see it. Shine the laser outside in the fog and you;ll see what I mean. Its kinda like a squirter gun... its squirting light, not moving a dot...
But yes the visible part of the light would move faster than the speed of light.
2006-07-04 13:17:08 · answer #10 · answered by Anonymous · 0⤊ 0⤋
No...light is light. It travels at the speed of light no matter what you do to your pen. You would simply experience the dot being slightly behind where you would expect it to be.
Light takes time to travel and cant travel faster than the speed of light funnily enough.
2006-07-05 04:24:24 · answer #11 · answered by BigBoy 3 · 0⤊ 0⤋