A Brief History of Light

One nit pick about "no matter what frame of reference you happened to be measuring it from." You have to be using an INERTIAL frame of reference, which means some care is required when doing large-scale experiments on the earth.

Thanks! A great explanation on that weird thing that is light.

Great post, Matt! A succinct yet clear example of the difficulties involved in trying to answer someone who says, "just tell me what it really is already".

For some reason I feel the need to nit-pick whenever I read one of your (otherwise excellent) articles on photons. This time the misstep that caught my eye was just a bit of trivia.

Re: "It's something much more mathematically complicated that has certain particle-like or wave-like properties. It wasn't until Feynman and colleagues developed the full quantum electrodynamic description of light that this was all figured out."

I'm pretty sure that the electromagnetic field was quantized long before Feynman's work in QED. In fact, I'd wager it was done back sometime in the late 20's.

" But in 1887, Albert Michelson and Edward Morley were able to do a very careful experiment to measure the speed of light as the earth moved through the aether as it orbited in space. Their experiment came up negative. There just wasn't any aether."

Thats not true actually. Michelson Morely was not consistent with Einstein. But it rather was more consistent with the doctrine of the partially-entrained aether. Whatever the aether is, it appears to entrain itself in a bodies gravitational field.

To see what light is we have to look with fresh eyes at the peculiarity of its characteristics, without getting bogged down by current dogma.

" Light was a wave, if a special one that didn't require a medium to wave."

There is just no reason to believe this. And Einstein himself didn't believe this, but this is neither here nor there, since science isn't about belief or the cult of personality. As soon as someone assumes there is no medium, arbitrarily, they have lost any capacity to then try and figure out what light is.

The idea of a volley of particles, being consistent with wave motion, makes no sense. It cannot be reproduced by some sort of animation to help one comprehend what is going on.

Everytime someone looks like coming up with a wave motion, without a medium, a whole bunch of people should shout out "Don't go there" or "Don't even go there". Its logical and its caused all this confusion.

The question "what is light?" always gets what I tell students is my favourite physics answer - "it depends" - in this case, on how you choose to test it.

It's an answer that becomes a lot more common as we get to the quantum physics unit.

But that cannot be right magista. A thing is what it is independent of testing. This is modern science not wanting to backtrack and so giving up. Yes and I know the slit experiments. But this really doesn't change matters.

What we ought to do is take the question seriously. Find out what light is. What its medium is. And so forth. Once we start pretending that light is two different things at once, and that it is waves with no medium, we've given up finding out what light really truly is in reality.

I think you are a little unfair to Newton. He understood that there was a wave-like element to the particles that he thought comprised light. In Optiks , he wrote of "fits of easy reflection and refraction" were were some sort of periodic characteristics that led to interference.

And, of course, we know about his experiments with prisms and who gave the name to Newton's rings.

Put in modern words, Newton understood that a pure particle model did not explain light, but he didn't develop a model that combined particle and wave models the way 20th century quantum theory did.

Chuck

On the photoelectric effect, there is one important detail you omitted: if the incident light is below a certain minimum frequency (what that frequency is depends on the substance the light is shining on), you get no photoelectrons. Einstein showed that the quantization formula that Planck (1901) had introduced in order to resolve the ultraviolet catastrophe also explained the existence of this minimum frequency.

Yeah, I'm with Graeme Bird! You physicists should stop pretending that light is two different things and answer the question seriously! Grrr, how can you say light doesn't have a medium? (other than that goddamned evidence you "science" types keep pushing).

Seriously GB, what you understand about science could fill a, well, moderately-sized pamphlet (large type). "It cannot be reproduced by some sort of animation to help one comprehend what is going on." Yes, because if you can't do a cartoon about it, you can't understand it. Wait, I guess that's true, YOU can't understand it. The rest of us on the other hand . . .

"A thing is what it is independent of testing." Yes, brilliant. So no matter what we actually find, ya know, EVIDENCE for, the "thing" remains unchanged. Good thing you weren't around when the germ theory of disease was being tested, we'd still be convinced illness was the result of witchcraft (BURN HER!) or other such nonsense.

At every step of this history one would notice that the logical inference drawn is reasonable but not full-proof. One tends to think of the reasons given as inescapable consequences, whereas they are historical and not logical reasons for the theory of light to have taken that step.

"Put in modern words, Newton understood that a pure particle model did not explain light, but he didn't develop a model that combined particle and wave models the way 20th century quantum theory did."

That was no failure. The failure is the modern interpretation. They should have three or more separate models until one wins out comprehensively. Instead they have turned theological. Unable to work out what is the real deal, they've made up an idea less scientific then the idea of the trinity.

This is a terminal failure if it is continued. To take a shortcut and to come up with an unscientific model, rather than to maintain several models until the matter is resolved, is to bring progress to a grinding halt.

Its 2010 and we still don't know what light is. This is the public service, not doing its job.

"Still, you should always keep when I or anyone else talks about light as a wave or particle, it's an approximation. Nature is more subtle."

That is not the attitude to take. This is akin to saying "The Lord moves in mysterious ways." If you assume rather that the public service has gone down the wrong path and failed, there is at least a chance the situation can be repaired.

"You physicists should stop pretending that light is two different things and answer the question seriously!"

We have to stop this idea that science is about the cult of personality. "Physicists" have managed to grab unquestioned seniority over the other scientists, and even over the philosophers. But they aren't really physicists any more. They aren't interested in the scientific method. They are public servants and not natural philosophers. We are talking about the public service with all the dysfunction that implies.

The problem with pretending you can have wave motion without a medium, is it stops you from finding out what that medium is. So there is no mystery at all why the public service has run into a brick wall and failed utterly.

Well GB, I would say you jumped the shark, but that would be assuming you started at a position not flat in the middle of insanity. "We have to stop this idea that science is about the cult of personality." Um, the only person who thinks that is you, and uneducated jackasses like you. Science is about being RIGHT, not just acting like you're right (for examples of that, see politics, religion, and just about everything else in the world). You have to prove your successes, and every time you do, there's a line of people ready to disprove your ideas should you be sloppy. It's like capitalism without the evil overtones.

In the end, why don't you just apply to grad school and achieve massive success in your new proofs of the aether? You get a cool million bucks for Nobel prizes, and I'm sure overthrowing Einstein, et al, would pretty much write your ticket to a cushy job. So why not put your money where your mouth is? Oh, right, because if you did that, your money would be mired in corn-laden shit, just like your comments.

"sure overthrowing Einstein, et al,"

You see this? Science on the basis of the cult of personality. But science is not about consensus, peer review, the cult of personality, or any of that dysfunctional priesthood stuff.

Science is about evidence, reason and the scientific method. The priesthood is in a rebellion against science.

"In the end, why don't you just apply to grad school and achieve massive success in your new proofs of the aether?"

Its not a new proof. Its the same old proof. Just by the way, Einstein always believed in the aether. That puts your cult of personality epistemology into unresolvable conflict surely.

Light moves in waves, Hence some sort of medium. Simple as that. We want to find out what that medium is or the public servants will never be able to tell us what light is. Simple as that.

There was never any logical reason to abandon the fact that waves require a medium. Suggesting that this is the case puts you on the opposing side to Einstein, which is of course neither here nor there.

When I see one of the scientists saying that he's taking an extreme point of view and he thinks that electrons (for example) are just a wave, and no particle at all .... well he may be wrong or he may be right. But at least he's being a scientist. Once you decide these particles are wavicles, or both a wave and a particle, or that it depends on how you test it, you've taken a shortcut, subverted the search for the truth of it, and you've ceased being scientific.

The proof is in the result. 2010 and the public service are still completely stuck on this poser. They don't know what light is. Have no idea what gravity is. And are in utter denial of the fact that gravity propagates much faster than light. So therefore they cannot follow the implications of what this instantaneous propagation means. Actually it is probably a clue to what the missing medium truly is.

gravity propagates much faster than light? say what?

Dammit, why didn't us scientists think of the name "wavicles?" Ooh, that's good! Ok, well, I guess I'm done feeding the troll, he got spanked well enough at PZ's place that I don't need to bother. Try education sometime douchebag, it's harder than ignorance, but worth the trouble.

"gravity propagates much faster than light? say what?"

How fast did you think gravity propagated? And why? What made you think that? You will find that you assumed it from doctrine.

"Dammit, why didn't us scientists think of the name "wavicles?"

1. Clearly you are not a scientist Rob. Don't fool yourself.

2. A science-worker did come up with the name wavicle.

3. Don't bring up the liar PZ Myers. Liar said I was anti-evolution and anti-vax. This is the leftist nutjub approach to science. Tell lies. Reject the scientific method. Start calling people trolls. PZ could never beat me in any sort of debate. So he gets his people to swarm.

So what is light? Rob? What is light? You've given up on the subject have you not?

Rob Monkey. Surely you ought to reverse the order of your name. You are not a scientist Rob.

that actually sounds like a decent introductory physics post topic, for those of us laypeople too lazy to bother googling it up ourselves: what is the propagation speed, if any, of gravity? how do we know it?

i know (well, let's rather say i "know") relativity treats gravity as an aspect of space itself, and that almost makes it sound like an intrinsic property that likely changes instantaneously if at all. but what i really know of relativity could easily fit into a small pamphlet using large type. and i've also heard that quantum mech isn't nearly so clear on what gravity is and how it works, so who knows what it might have to say on the matter.

intuitively, i'd guess that astronomy and astrophysics could probably provide an estimate of the speed. more intuition tells me that if that speed was very much different from the speed of light, astronomers would have been tearing their hair out over their observations for a century now, so it's likely c. but i don't really know any of that.

Nomen its very important that the laity like you keep the public service honest. After all if you are a taxpayer they are working on your time.

The propagation speed of gravity is essentially instantaneous. We know this or else the orbits of planets would unravel. Unfortunately special relativity is a religion. While numerous examples of superluminal speeds are known, and in fact repeatable in the lab, it is a heresy for the benefactors of the public service to talk about this or suggest this as a refutation to some of their sacred cows. In unmixed company this knowledge is spoken of confidently.

This means that gravity too is held to propagate at that speed. Which is ridiculous. If we were to find the angle of the suns pull on us we would find it is coming from the suns true position. Not from where the sun was 8 minutes ago.

Now what does this mean? Well consider the doctrine of the photon. This photon is alleged to be created ex-nihilo. We can call this photon Forrest Gump. Or Forrest for short. No matter where this photon is created it doesn't like where it is. It starts running away from us at the speed of light in this story. "Where are you going little photon" and "Why are you running so fast".

I want you to consider the utter strangeness of this behaviour.

Now the next thing is that when calculations have been attempted for the propagation speeds of GRAVITY the public servants have essentially taken two approaches to the matter.

1. The Monty Python "Are you a virgin?" approach. This is where they claim that gravity propagates at the speed of light. And they say "It does you know." "It must do". When further prodded they will go into incredible evasive action. The usual. Bombing you will links. Ridicule. Arguments from authority. All the normal gear.

2. Actual attempts to calculate how fast gravity particles would need to move to produce a push-gravity version of the force of gravity wind up coming out at 20 billion times the speed of light. I don't know the assumptions behind this. Essentially gravity is instantaneous, and certainly in the single galaxy context.

Now consider again how odd it is for a Forrest Gump particle to be created ex-nihilo and to race off at the speed of light? No reason is given for this utterly bizzare behaviour. If this is not bizarre enough at the speed of light, then how more implausible is it to suppose that we can have gravity particles which exhibit this same inexplicable strangeness, but at 20 billion times the speed of light?

So we find from this analysis that we have but one conclusion to make. That all objects that exhibit mass are permanently attached either directly or indirectly to eachother.

EACH PROTON IS ATTACHED TO EVERY OTHER.

Now going back to this question of lights medium:

If all particles that are affected by gravity are attached to every other, directly or indirectly....... why ought this network of attachments not form the medium that light is traveling through?

If you have a peg on either end of a tight clothesline and you hit that peg, you will note that the peg at the other end moves almost immediately. Now we have an explanation for the strange behaviour of light and gravity. And this is really the only contending explanation. All other explanations are essentially voodoo.

Graeme,

The problem with your claim "All other explanations are essentially voodoo" is that these other explanations have been tested to extreme accuracy. QED is our quantum mechanical theory of photons, it's built on the assumptions of special relativity, and has made several new predictions, all of which have turned out to be true to remarkable precision.

If you have an idea you think is better, that's awesome! Use it to make some new predictions and test them empirically. If the experiments work out, you'll have data to back up your claims.

As far as instantaneous gravity is concerned, I'm not convinced we can measure the direction of the sun's gravity accurate enough to do the experiment you mentioned. I do know that in the theory of General Relativity, changes to the gravitational field propagate at the speed of light, and this theory again has made remarkable and verified predictions. Can your instantaneous gravity explain the rate at which Mercury's orbit precesses?

You're very right in that it seems strange that photons instantaneously rocket off at the speed of light the moment they're created. I can only say that, who are we to deem what's strange? There's no a priori reason to assume the subatomic world acts in a way that is intuitively familiar to us. We are used to dealing with complicated objects composed of trillions of trillions of protons and electrons all interacting with each other; we only see the overall effect, and there's no reason to suppose the subatomic world obeys the exact same rules we do.

Kudos to Geoff.

Its important to remember that the wave nature of light is not special. All particles have a wave nature. It is just more visible in light because they are lower energy.

No the other explanations haven't been tested Geoff. Don't be silly. What you mean surely is that the formulas check out within limits, from a narrow mathematical point of view. Why one earth would they not? Thats what the formulas are for. They are for doing the calculations. But note. The formulas do not work outside certain limits. They do not work for the universe or for the rotation of galaxies.

So for example if we take the orbit of Mercury. Well we already knew the orbit of Mercury prior to special relativity. So special relativity isn't confirmed by the orbit of Mercury. The maths of special relativity is okay for the orbit of Mercury. Why wouldn't it be. It was formulated that way. But this is not evidence for special relativity. It just means that they've refined the maths.

We would have been better off with a set of tables, if we were going to go fooling ourselves.

See when you make up a formula to help you out with the calculations, you must not up and let these formulas fool you and dictate to you.

"As far as instantaneous gravity is concerned, I'm not convinced we can measure the direction of the sun's gravity accurate enough to do the experiment you mentioned"

Come off it. You cannot seriously suggest they could screw a straight maths problem like that up would you? Thats what these people are good at.

"ts important to remember that the wave nature of light is not special. All particles have a wave nature. It is just more visible in light because they are lower energy."

A wave is not what something IS. A wave is what a whole bunch of things DO.

It is not possible for something to be both a particle and a wave. To suggest such a thing and then dogmatically demand it (not you but the priesthood, and general science maffia) is to put a permanent roadblock in front of the public servants, finding out WHAT ACTUALLY IS going on.

"If you have an idea you think is better, that's awesome! Use it to make some new predictions and test them empirically. If the experiments work out, you'll have data to back up your claims."

I'm not paid to work out what is going on. My beef is that other people are, and they refuse point blank to do their job.

We see a breakdown in science and a rebellion against the scientific method. This is why we get to 2010, and the public service cannot tell us what light or gravity is and refuses point blank to find out.

These are very basic questions and they cannot answer them coherently or reasonably.

"I can only say that, who are we to deem what's strange?...."

HAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHA

What gets me about you bully-boy advocates of obstruction, and never finding out anything new, is you so much lack culture. I don't mean that in some small way. But in a very big way. Surely if you were well-educated, in the broad sense, you would have realised what a priesthood statement that was. The Lord moves in mysterious ways. "I can only say that, who are we to deem what's strange?" Who are we to enquire into the mysteries of the Lords motivations?

No you see we are just talking about stuff that is bigger or smaller. We are not attempting to see ultraviolet in our minds eye or anything like that. Mathematicians and sycophants really come a cropper when they pretend to be philosophers.

So if something is very small, we have to ask ourselves if it is an object, or if it is not an object. Is it a collection of objects held together by bungy ropes? Or in any case, just what is its physical make up and behaviour? Just what is it and can we make an animation of it?

If we cannot even so much as make an animation of what is going on with the small stuff then we have no decent explanation at all. Its not time to lock in half-knowledge with probability, formulas and voodoo at that point. We want to know and explain clearly what is actually going on.

Is Graeme Bird an April-1st-related phenomena?

You just cannot comprehend what I'm saying can you Anonymous? Do you have an explanation as to why a photon would want to appear out of nowhere, and beat it, scram, high-tail it, out of where it is now, at the speed of light?

Its not April 1st where I am. An explanation which doesn't tell us why a photon would act in this way is not explanation at all.

@31: i wish he were. he's apparently a genuine kook, hailing from australia, who got attached to scienceblogs through stumbling on one of P.Z. Myers' posts. he's already made himself quite infamous on pharyngula, and is now apparently branching out.

Goodness me Nomen you ignorant kook. And here I was expecting you to keep these guys honest. Yet apparently, like the liar Myers, you think you know it all already.

I wish I had the leftist gift of second sight like you people. I could just see and believe. I wouldn't need to think at all. You are in cloud cuckoo-land man. I suppose you think that space stretches and warps right? The faith-based approach to science hey Nomen?

oh, and just because i don't think it's been posted here before: there is a way to read sB (and many other web-based discussion fora) while selectively filtering out commenters you would rather not read. it's a bit eggheaded, but not too very badly so.

first, you must use Firefox as your web browser. at least, i don't know if anything similar is available for any other one. Chrome might perhaps have something, but i couldn't swear to it.

second, you must have the greasemonkey plug-in installed in firefox. this is an infrastructure improvement that makes it possible for people to add custom javascript code to any web page displayed, which makes programs easier to write.

and third, you must have the killfile script installed in greasemonkey. this is a bit of custom javascript that gets added to web pages of certain blogs (the most common ones, including scienceblogs) which adds some "don't bother showing me this comment / this person's comments" links to every comment. and it remembers which people you don't want to see, too.

fortunately, once you're using firefox, adding the other two ingredients is a matter of two or three mouse clicks each. easy. also makes certain discussion threads much shorter and easier to read.

"oh, and just because i don't think it's been posted here before: there is a way to read sB (and many other web-based discussion fora) while selectively filtering out commenters you would rather not read. "

So thats how you got that ignorant. At the first sign of a new idea, incurious leftist kooks employ technology to block it out. I've just given you a more or less full-proof explanation that all particles that exhibit mass are connected to every other. Somewhere along the line you've learnt to merely believe the public sector, and that logic and reason are not part of science.

Why didn't you just say you were a kook up front?

oaky, okay:

you're a kook.

Woah, I step out for a day and everything goes nuts. But hey, even wacky discussion is a place to learn something.

I would like to comment about this:
A wave is not what something IS. A wave is what a whole bunch of things DO.

This isn't really right. "Wave" is just a shorthand for mathematical formalism that can describe all kinds of things. There's no requirement that we interpret it in terms of physical objects "doing" things. You can take an abstraction like the moving average of stock prices and express it in terms of a Fourier series - a wave. It's not possible to predict the market of course, but the mathematical formalism works fine as a description of the data. Nothing's actually "waving".

And there's no requirement that light do so either.

No no. Wave is not any shorthand for mathematical formalism. Its a real EVENT involving movement through a great many discrete objects. Waves would exist if mathematics was never developed.

Modern physics has a religious overlay to it. Partly because of two sins against logic. One logical error is to reify a concept into an object. But you've just committed another error, in that you've demoted a real object, or in this case an event, into a mathematical concept.

You don't want to play mix and match like this. Or you will lose your sense of what is real and what isn't. We must distinguish between concepts and objects.

When you are talking about a wave in stock prices you are talking by analogy towards real things in nature. In this case a wave.

So consider the unlogic. You've taken an anlogy of a wave, said that this analogy is not a real wave, and then tried to say that real waves in nature are merely mathematical constructs. But you can surf on some of them, and without a calculator in sight.

"And there's no requirement that light do so either.

Once again this is impossible. All authentic waves in nature require a medium. An analogous wave in stock prices is something else again, because its a wave in things that are already at one or two levels of abstraction.

So we know that light must have a medium. Many things in physics are in grave doubt. But not this. A girls smile is not possible without the girls face. No evidence has ever emerged that light waves, or any real waves in nature, lack a medium.

The first step to finding out what light is, consists of finding out what its medium is. The reason why we haven't found out what light is, is that we abandoned the search for lights medium. Clearly this was an unjustifiable mistake. And look at the extreme consequences of this mistake??? The proof really is in the pudding. We abandon finding out what lights medium is, so why are we surprised to find out, that in 2010 we don't know what light is. The result follows the logical error like night follows day.

Aww. Graeme is posting his woo here, too. At least here he won't have the power to continually delete comments with which he disagrees, and edit others' posts to his liking.

Still, he'll continue to insist there's no evidence for relativity, that the aether exists (and Einstein believed in it), and various of other silly claims.

Oh -- but vote for his disingenuous ass!

Its not WOO. In fact the existing theories of light and gravity would be WOO. If any of the PZ MYERS blockheads had it together to define what the hell WOO is.

The idea of space warping is woo. Its the idea of there being such an entity as "space-time" that is an occult idea.

And most specifically its the PZ Myers school for dopes epistemology that also is occult. All his mindless sycophants think they can know stuff without evidence, reason or good methodology. So you come here you moron, and you have no argument to make. You have no reasoning. No evidence. And yet still you think you know stuff that you cannot possibly know.

Thats occult epistemology. Or WOO if you like. You being too stupid to understand the phrase "occult epistemology."

Occult epistemology: the study of the knowledge of hidden things.

Thus far, your evidence of relativity being wrong and gravity (and light!) propagating at anything other than 'c' -- indeed, any evidence that you have any clue what you're talking about, Graeme, is occult. Your reasoning on your blog, such as "Well, all natural waves are something moving mechanically, therefore the aether exists!" is occulted, too.

You know, I posted Einsteins original views on the aether, which you disingenuously deleted, and then cherry-picked incomplete quotes from, to make it seem as though you had some evidence. THEN you whine about revealed knowledge and arguments from authority.

I urge anyone close to Mr. Bird to recognize that he's probably not very well. I'm serious about this. He very likely needs some medical attention. If you happen to know him personally, please take whatever steps you can to help him out.

Special Relativity cannot be proved wrong since its not science its religion. There are some relativistic effects. Special relativity gets in the way of us finding out and proving the reason behind them. Alternative theories that are out there don't stand a chance while the public servants are committed to their religion and are fulltime against other peoples religions, as well as against science and the scientific method.

What you posted about Einstein confirmed what I said about him. He stayed a believer in some sort of ether until the day he died. But this is neither here nor there, since science isn't about the cult of personality. Nor is it about what anyone believes nor doesn't believe.

"Thus far, your evidence of relativity being wrong and gravity (and light!) propagating at anything other than 'c' -- "

This is just straight lying and drooling idiocy on your part. As I pointed out all our orbits would unravel were gravity not instantaneous. Further, the force exerted from our sun comes from where it is now, and not where it was eight minutes ago.

Since you are a kook and a religious nut the only way to get you to understand this is with a good length of hickory or a blowtorch.

@16:
Compton Effect. Waves cannot explain the angular distribution, but photons can.

@46:
Someone is yanking your chain.

Mr. Bird,

I don't get the blowtorch thing.

And does it have to be hickory, or will ash work equally well?

Just for the record, I always believed in the aether, albeit a non static one, until the day I died in 1955.