Movement of Light
May. 12th, 2006 @ 09:10 am
I think someone in some journal may have acknowledged this... but physics seems to occasionally still have this debate about light. Specifically, "Is it a particle or is it a wave?" is the common question.
Keep in mind, I know nothing about this... but I can't help but ask, why can't it be both? Why can't it be a particle that moves in a wave pattern? There might be some inquiry required as to WHY it moves in a wave-like pattern (standard physics would say that unless something very interesting is going either in the particle or on the particle, it should go in a straight line).
Here's my reasoning:
First to prove it's a wave, there's the trick of poking a small hole in a large piece of cardboard or paper, and putting two light sources on one side, and seeing the pattern that is created on a solid surface (aka, wall) as the light passes through the hole. With two light sources, most would say "two dots would appear... one for each light source." However, what actually happens is (if done right) THREE dots are created... one for each light source, and then a third in the middle created by the interference of the two waves of light particles with each other, cancelling out their own wave, and creating a third more direct light spot in the middle. If there weren't a wave of some form, this interference pattern wouldn't be created.
Second to prove it's a particle, all you have to do is create a perfect vaccuum within a transparent container. Such an environment would be completely empty of any particles, including photons, that could propogate any wave-like activity (in order for a wave to exist, there must be particles present to put into a wave-like motion). Then shine a light through the transparent box-vaccuum. Light will still go through. If light were strictly a wave, the light wouldn't be able to pass through the vaccuum since there are no particles to propogate the wave through. So, the light must be providing it's own particles that can pass through the vaccuum.
So... light does things that are both particle-like and wave-like. I just don't get why science needs an either/or scenario here. I say it's both, and if we can accept that and stop wasting time talking about it, we might be able to focus our energies on actually doing something with it instead.
true, assuming space is really the vast empty vaccuum we like to think of it is... and true, it may be devoid of a lot of the common atoms and molecules we think of... but there may be a ton of electrons, photons, quarks, etc., flowing through space to allow all of those things to travel just fine. It may be a vaccuum from our perspectives... but it's not a perfect vaccuum. There's a lot of "stuff" out there... it's just either not something we detect, or so widely dispursed that it doesn't come up in a detectable way. Further, if light is both a particle and a wave, it can ride the vastness of space just fine since it has everything it needs to get around.
Indeed, you are correct.
The theory on electromagnetic waves (forgetting about the particulate properties of light for a moment) does not require a medium in which to propagate. It's a bit unintuitive, but the waving is caused by the interaction between the electric and magnetic components of the wave. A varying electric field gives rise to a magnetic field (similar to an electomagnet), and a varying magnetic field gives rise to an electic field (similar to a generator). These field variations self-propagate through space, continuing on the "waving" though their mutual interaction.
cosmic radiation is also just another form particle wave. light, microwaves, cosmic radation....they're all made from particles that act like waves.
besides, i don't think physicists get too bent out of shape over this debate anymore. start talking about string theory though, and you've got trouble...
modern science doesn't have this debate as far as i am aware. the advent of quantum mechanics earlier this century quasi resolved this issue ... light IS both a particle and a wave, as is everything. it's called wave-particle duality. check it out on wikipedia
In practice, there is no such thing as a perfect vacuum. Even if you pumped all the matter out of a sealed box, there would be virtual particles generated from the zero-point potential.
My favorite wave-nature experiment is the double-slit. Put two small slits in a board, send a single photon at the board, and it will pass through BOTH slits, interfering with itself. What's even cooler is that will work for alpha particles (helium nuclei) too. Just what is matter that it behaves that way? Maybe all matter is as much a wave as a particle. Oh yeah, that's what quantum mechanics is all about.
I think the issue about particle-wave duality is how to characterize the fundamental things in the universe. While humans can easily hold a paradox in mind, mathematics isn't as accomodating. If light exhibits properties of both particles and waves, then we don't understand something about particles, waves, or light. Gaining that understanding is what science is all about.
It's really not that bizarre. Everyone has a conception of a macroscopic wave and a macroscopic particle, and these two categories are generally mutually exclusive. Instead of trying to figure out how an object can be both, realize instead that the object is neither. Quantum mechanics is itself a complete description of nature. Yes, it *shares* some properties of wave physics and it *shares* some similarities with discrete mechanics, but isn't a subset of either. Everyday macroscopic experience just isn't applicable to the quantum mechanical world. Humans just don't have an intuitive understand of reality on that level, even though we can predict and quantify the effects.