Question for Physics Buffs...(Theory of Relativity?)

[kerrywins]

If there were 2 flashlights setup pointing in the same direction at a person in front of them with some type of made-up divice in his hand that could accurately measure the exact moment the light hit it. And one of the flashlights was 10 ft. away from the person and one of the flashlights was 15ft away from the person....
would the light hit the device in the person's hand at the same time? Or would the flashlight closer to the person hit the device first?

[trotsky]

1. The speed of light is finite.

So the light from the closer flashlight would register first.

[Dookus]

2. this has nothing to do with relativity...

the light from the closer flashlight would hit first, albeit by an extremely small margin.

[kerrywins]

3. does light travel in waves or photons or both?

Did Einstein say light could travel in both?

[jdonaldball]

7. That's more like quantum physics, which Einstein essentially rejected

[Dookus]

8. try this

http://www.thespectroscopynet.com/Educational/wave_particle_duality.htm

Is light a wave or a particle? The apparent dual nature of light is easily demonstrated:

Stand outside in the sun. The shadow your body makes in sunlight suggests that light travels in straight lines from the sun and is blocked by your body. In this, light behaves like a collection of particles fired from the sun.

Place two sheets of glass together with a little water between them. With care, you will see fringes. These are formed by the interference of waves.

In 1925, our understanding of light seemed to have come to an impasse. Particle theory could explain reflection and refraction, and recent experiments in radiation (such as the radiation from hot bodies and the Compton experiment with X-rays). And wave theory could explain the interference and polarization of light which particle theory could not. Thus simple and sophisticated experiments both indicated that light could be a particle sometimes and a wave at others.

Albert Einstein (1924) expressed the dilemma:

There are therefore now two theories of light, both indispensable, and - as one must admit today in spite of twenty years of tremendous effort on the part of theoretical physicists - without any logical connections.(1)


The dilemma prompted Neils Bohr (1928) to offer his 'complementarity principle': that particle theory and wave theory were equally valid. Scientists should simply chose whichever theory worked better in solving their problem. While it got physics out of its immediate hole, coming from someone as important in modern physics as Bohr, it gained a dominance in physics teaching probably never intended.

Over the succeeding years, the currently accepted solution came in the form of the 'quantised electromagnetic field theory', i.e. 'quantum electrodynamics' (QED). The theory merges particle and wave properties into a unified whole. Despite this, the undergraduate physics of light is still often taught as separate chapters on particles and waves with little or no attempt to give an overall understanding of how this can be so. The complementarity principle is still used in books on optics to justify the use of wave theory to explain interference, polarization, diffraction, etc. The student is then left with the impression either that we do not really understand the true nature of light or that physics is simply a collection of tools for solving problems.

[jdonaldball]

13. Well, Einstein rejected Heisenberg's recognitions

and I think Einstein was mistaken to do so.
Einstein: "I believe in Spinoza's God who reveals himself in the orderly harmony of what exists, not in a God who concerns himself with the fates and actions of human beings." Quoted by Felix Gilbert in "Historische Zeitschrift" number 233 (1981), and in other sources.
So much for Einstein the "Humanist."

[GCP]

4. They'd both hit the device at the same time

It's the same kind of question that Einstein used to pose: would light from a flashlight on a train travel any faster or slower depending on whether the light was pointing toward the front of the train or the back. The answer is there's be no difference - can't explain why, it's to do with relativity.

On edit - "never mind" - Emily Litella voice!

[kerrywins]

6. you don't know why?

I wonder why?

[Dookus]

9. No, that is wrong

by that reasoning, light from Alpha Centauri would get to Earth as quickly as light from the Sun. That is not the case.

[htuttle]

5. You would need an extremely accurate measuring device

But the one closer would hit first. Here, it should be basic Newtonian physics.

I think the relativistic effects would sort of fit in if one person were moving quickly toward the target, and hit their light when they were the same distance from the target as the stationary person. They'd both hit at the same time, although in the same situation, but at sublight speeds, the one moving would hit first (such as with bullets or arrows, etc...). I think.

[Endangered Specie]

10. Assuming you also have a device that can turn on the lights at the

exact same time, the light from the 10ft away would hit first than the 15ft away light.

[Endangered Specie]

11. This has nothing to do with relativity, this is basic Netwonian mechanins.

[slutticus]

12. The speed of light is constant and finite (within a specific ref. frame)

Since everything (the flashlights and the person) are stationary, the light from the closer flashlight would hit first.