Physics ppl

[Vigilante]

In theory...light has no mass so I guess you could make it go a little faster but not much faster probably around 0.0000000001km/s faster...but still it's faster.

a light photon does have mass, but it's basically negligeable.

 

[Neutrino]

I really dont understand what you mean by light speed not being relative..can you explain it?

I can try.

When you look at normal everyday objects they all have a velocity that is relative to everything else. For example consider two cars traveling on the road. The speed of both cars differ depending on what frame of reference you use. Say they are traveling toward eachother at 60mph. To a third party on the road they are both traveling at 60mph. But seen from inside the cars each one is traveling at 120mph. Both speeds are correct depending where you are. This is pretty intuitive as we experience this kind of thing all the time.

However, the speed of light is different. It's not very intuitive at all. Let's use a parallel to the car example abovel. Consider two spaceships that are traveling toward each other at a very high speed. Now say both ships shine a light at one another. So what happens when you measure the speed of the light from different frames of reference? Let's say your in one of those spacehips and have a device to measure the speed of the light coming from the other space ship. Using your normal intuition developed on earth you would expect the light to be traveling light speed plus the speed of the oncoming ship. Right? But actually that's not what happens. You will actually measure the light to be going exactly at light speed. Same thing if the other ship was traveling away from you. You'd expect the light to be going slower than light speed then, but it wouldn't be. You would still measure it going light speed.

That's what is meant by saying light speed (C) is a constant. It cannot change. No matter what frame of reference you measure it from it will alwasy have the same speed.

I just found an explantion on wikipedia as well:

Constant in all reference frames

It is important to realize that the speed of light is not a "speed limit" in the conventional sense. An observer chasing a beam of light will measure it moving away from him at the same speed as a stationary observer. This leads to some unusual consequences for velocities.

Most individuals are accustomed to the additive rule of velocities: if two cars approach each other, each travelling at a speed of 50 kilometres per hour (31 miles per hour), one expects that each car will perceive the other as approaching at a combined speed of 50 + 50 = 100 km/h (62 mph) to a very high degree of accuracy.

At velocities approaching or at the speed of light, however, it becomes clear from experimental results that this additive rule does not apply. Two spaceships approaching each other, each travelling at 90% the speed of light relative to some third observer between them, do not perceive each other as approaching at 90 + 90 = 180% the speed of light; instead they each perceive the other as approaching at slightly less than 99.5% the speed of light.

This last result is given by the Einstein velocity addition formula:

u = {v + w \over 1 + v w / c^2}

where v and w are the speeds of the spaceships relative to the observer, and u is the speed perceived by the observer.

Contrary to one's usual intuitions, regardless of the speed at which one observer is moving relative to another observer, both will measure the speed of an incoming light beam as the same constant value, the speed of light.

The above equation was derived by Albert Einstein from his theory of special relativity, which takes the principle of relativity as a main premise. This principle (originally proposed by Galileo Galilei) requires physical laws to act in the same way in all reference frames. As Maxwell's equations directly give a speed of light, it should be the same for every observer—a consequence which sounded obviously wrong to the 19th century physicists, who assumed that the speed of light given by Maxwell's theory is valid relative to the luminiferous aether. But the Michelson-Morley experiment, arguably the most famous and useful failed experiment in the history of physics, could not find this aether, suggesting instead that the speed of light is constant in all frames of reference.

Although it is uncertain whether Einstein knew the results of the Michelson-Morley experiment, he took the speed of light being constant as a given fact, understood it as reaffirming Galilei's principle of relativity, and deduced the consequences, now known as the theory of special relativity which includes the counter-intuitive addition formula above.

a light photon does have mass, but it's basically negligeable.

Hmm, not exactly. It has a rest mass of zero, though it get's a little fuzzy as it is never at rest. So basically it doesn't have mass but it does have momentum.

Here's another site that explains it better than I could:

http://www.physlink.com/Education/AskExperts/ae180.cfm

 

[Vigilante]

I understand that now..thats a lot neutrino. I never thought about the 2 cars coming at each other and them be traveling at 120 mph to you...weird

 

[Phisionary]

there's another thread in OT where we are discussing the reasons for the light speed limit and how it affects physics.

 

[Vigilante]

there's another thread in OT where we are discussing the reasons for the light speed limit and how it affects physics.

that came out of this thread. did you notice how dreams post in this one is the same as his first post the the "Why you can't travel at the speed of light" ?