Tuesday, February 28, 2012

What Hertz taught us about nothingness



I'm embedding this YouTube video here, but if you really want the full effect, skip that and try the Flash animation here. It was created by 14-year-old twins, Cary and Michael Huang, which I'd say is nothing short of astonishing.

The video shows you the basic idea, but with the Flash animation, you can control things yourself. It's really neat.

Anyway, I got the link from a fascinating article in, of all places, the Christian Science Monitor. (Yeah, I know that's a respected publication, but I still find it odd to read about real science there.)

Last week was the 155th birthday of Heinrich Rudolf Hertz, and this article is about Hertz's contribution to the "science of nothingness." I think it's a great example of how science advances.
"Horror vacui," goes the phrase, usually attributed to Aristotle's fourth book of Physics. Nature abhors a vacuum. True or not, it's certainly the case that those studying nature have long struggled with the concept of empty space. Aristotle thought that, because space empty of all matter offers no resistance, objects moving within it would move infinitely fast. Thus the objects surrounding any void would instantly fill it before it could form. Emptiness, he concluded, was therefore impossible. Every part of the universe must be filled with something, even if we can't detect it.

Aristotle's arguments persuaded scholars for a good 1,500 years or so. Medieval Christians were enjoined from entertaining the possibility of a vacuum, until the Catholic Church's Condemnations of 1277 broke Aristotle's monopoly on the natural sciences by admitting that, at the very least, a vacuum would not be beyond the powers of an omnipotent God.

Funny, isn't it? As long as the church's position held that a vacuum was impossible, scientists would be risking their lives to question it. Of course, this was more Aristotle than Jesus, but you could not question church teachings.

Note that Galileo was threatened with torture and death for claiming that the Earth revolved around the Sun. Even after recanting his claims, he spent the rest of his life under house arrest.

The Inquisition refused to even look at his evidence. Why should they? They knew he was wrong. If the evidence contradicted the Bible, it was wrong. If it went against church teachings, it was wrong. They had faith, so what did they need with evidence?

So I think it's ironic that the argument that "God" could do anything was required before scientists could seriously question Aristotle.

Aristotle himself was a great thinker, but he was a philosopher, not a scientist. Of course, there weren't any scientists back then. The scientific method hadn't been invented. But the problem with philosophy is that reasoning, even by brilliant thinkers like Aristotle, is not enough. You have to ground your beliefs with evidence.

No matter how smart you are, no matter how reasonable something seems to be, it has to be backed up with good evidence. Only evidence-based thinking can bring smart people to a consensus, and only evidence-based thinking can create a firm foundation for future advances.

But it took us a long time to learn that. Well, the scientific method might be the greatest invention ever made.
But even though contemplating empty spaces became theologically permissible, the idea of nothingness still proved troubling to early modern thinkers,... who... embraced a philosophy known as plenism, which left no space for emptiness.

The plenists arguments were persuasive. Sure, they argued, you might be able to remove all the air from a glass tube, but how is it that, say, two magnets inside the tube will still attract one another, if there really is nothing at all between them? How is it that electric fields can pass through the tube?

In the 19th century, after scientists firmly established that light travels in waves, scientists wondered how waves of light from the stars could ever reach the earth after traversing millions of miles of allegedly empty space. A wave, after all, needs something to ripple through, right?

Again, that seems reasonable, doesn't it? These weren't stupid people, far from it. They were trying to discover something unknown, something brand new.

But these people were scientists. They tested their ideas. They tested each other's ideas. (None of us wants to be wrong, and that can make us less than enthusiastic in disproving our own hypotheses. But we never have a problem with proving someone else wrong, do we? That's one reason science advances.)
Hertz initially complicated the picture even further, but his work also foretold a way out. While attempting to demonstrate the theories of Scottish physicist James Clerk Maxwell he conclusively demonstrated the existence of electromagnetic waves, and then caught a glimpse of how these waves act in very un-wavelike ways. ...

The Monitor's Chris Gaylord describes Hertz's famous experiment

I can't post the entire article here, so I'm not going to describe the experiment itself. You can read the article for that, or click on that link for a slightly different explanation of it.

The point is that, instead of just deciding what seemed reasonable to him, Hertz created an experiment which would provide evidence, one way or the other. That evidence would not just help convince himself, but other scientists, too. After all, they could duplicate his experiment. And they could build on it.

Again, that's how science progresses.
Later on, Hertz measured the speed of electromagnetic radiation, confirming Maxwell's calculations that it was the same as that of light.

To Maxwell, this was more than a coincidence. "We can scarcely avoid the conclusion," wrote Maxwell, "that light consists in the transverse undulations of the same medium which is the cause of electric and magnetic phenomena."

But what medium, exactly, is doing the undulating?

To answer this, scientists borrowed an idea from the ancient Greeks. Empty space, they reasoned, must be completely filled with a transparent, non-dispersive substance. This substance had to be fluid enough so that the Earth could travel through it without slowing, but rigid enough to vibrate at high enough frequencies to carry light waves. Maxwell dubbed this mysterious stuff the "luminiferous aether."

Again, this seemed perfectly reasonable. It just wasn't true. How did scientists discover that it wasn't true? Through experimentation:
But just after Hertz was using the luminiferous aether to link together the seemingly disparate phenomena of light, electricity, and magnetism, others were busy undermining it. Working in the 1880s at what is now Case Western Reserve University the American scientists Albert Michelson and Edward Morley reasoned that, if the Earth was moving through an aethereal substance, we should be able to detect an "aether wind," which would cause light waves to travel at slightly different speeds, depending on the time, season and the direction of the light waves. But, after a set of careful measurements, the pair found that the speed of light was unaffected by these factors.

But if there was no aether, then how did electromagnetic waves propagate?

A satisfactory answer wasn't put forth until 1905, the year that Albert Einstein upended classical physics with a series of groundbreaking papers.

Experiments in the 1880s showed that the aether idea was wrong, but it was twenty years before Einstein came up with an alternative. Well, we know we don't know everything. And knowing that one idea is wrong is still an important step forward.

Einstein's ideas really were groundbreaking - and mind-blowing. But they, too, had to be tested. In fact, they're still being tested. So far, they've been confirmed by numerous experiments. But as we get deeper and deeper into the fundamental nature of things, there's always more and more we don't know.
By imagining light not as a wave, but as a particle carrying discrete packets of energy, which he called "quanta," Einstein found that he could predict how certain frequencies of light would electrify certain metals. Einstein's explanation of the photoelectric effect won him the Nobel Prize in physic in 1921, and helped usher in the era of quantum physics.

So now we understand light, and all electromagnetic radiation, as having a dual role of both wave and particle. Electromagnetic radiation, including light, travels as a wave, but arrives as a particle, and there's no need to invoke any mysterious aethers.

Or is there? Einstein himself continued to use the word, particularly when attempting to describe how gravity acted on distant objects. And the quantum mechanical conception of vacuums are anything but empty: they contain ephemeral particles that pop in and out of existence, and even fleeting electromagnetic waves. Once you get to a very small scale, the universe starts too look a little more like Aristotle and the other plenists imagined it.

Funny, huh? Don't misunderstand. There's more and more we don't know, but there's more and more we do know, too. We use that photoelectric effect in modern technology. The fact that we don't know everything doesn't mean that we don't know anything. We are advancing all the time.

And this is cutting-edge stuff, now. Einstein was a hundred years ago. We're building on what he gave us - or, more specifically, on his theories as confirmed by experiment.

Anyway, this is where that Scale of the Universe animation comes in. (Trust me, it's really, really neat.)
Zoom in, past the penny, past the matchstick, past the paramecium and the DNA molecule. Keep zooming. Go past the gamma ray and the proton and the neutron. Go past the quarks and the neutrinos. Eventually, you'll get to a whole lot of nothing.

In fact, most of what we take to be solid matter actually consists of empty space. If you imagine an atom the size of a cathedral, its nucleus would be roughly the size of a fly. Thanks to electromagnetism, in this case the tendency for electrons to repel each other, everything doesn't collapse in on itself. You may think that you are sitting in a chair right now, but you are actually hovering above it at a distance of one angstrom, about 250 millionths of an inch. Neither your electric field nor that of the chair wants to get any closer.

Anyway, keep zooming in. Eventually, you'll get to the Planck Length, which is what physicists say is the smallest unit of measurement in the universe. At anything smaller than this distance, it would be impossible to tell the difference between two locations.

At this scale, physics is really weird. "Virtual" particles are flashing in and out of existence at extremely high energies, warping space and time into a quantum "foam," or so one theory goes. One-dimensional strings, according to another theory, vibrate in eleven dimensions, forging and maintaining the very fabric of our reality.

Now zoom all the way out. [If you're a gamer, be sure to look for the Mindcraft World to the left of Neptune.] All the way, past the planets, galaxies, and nebulae, until you get to our entire, expanding, universe. What is the universe expanding into? Nothing at all, according to the best current cosmological models. What was there before the universe? Was that nothing too?

The ancient Greeks were fond of another phrase about nothingness: It comes to us via the Latin expression "Ex nihilo nihil fit," or "nothing comes from nothing." They believed that the gods fashioned the universe out of a primeval matter, which they called "chaos."

Today, as cosmologists try to explain how our universe sprang from nothing, it's worth remembering that, in science, nothing is not what it seems.

Coincidentally, I was watching the Atheist Experience yesterday, last Sunday's show, and a very arrogant theist called in. This guy was convinced that he was the best debater in the world, just absolutely certain that he'd stomp any atheist who dared to challenge  him.

And when asked to give just a taste of his expertise, this guy said he had an argument which would convincingly prove to everyone the existence of God. First, something can't come from nothing, right?

Heh, heh. That must be something they teach somewhere, because I hear this argument all the time. You're supposed to agree with that, which will lead you inevitably to "God." The fact is, that's not true, even if something can't come from nothing.

But there's no need to go that far, as Matt Dillahunty and Tracie Harris pointed out. No, we don't know that "something can't come from nothing." That doesn't mean that we can conclusively demonstrate the opposite, but only that we don't know.

Well, that caller really had trouble understanding his logical fallacy. It was actually pretty funny (and I'll post a video clip of it, if someone creates one - or maybe if I figure out how to do that, myself).

The thing is, there are a lot of things we don't know. But our ignorance doesn't imply anything, except perhaps that these aren't easy questions. Maybe something can't come from nothing, I don't know. But you're going to have to demonstrate that if you expect me to accept it as true.

Heck, I don't even know what "nothing" is. We don't normally encounter "nothing" in our daily lives. We might think of air as "nothing," but we'd certainly learn better if it were missing. Even vacuum might not be "nothing."

Well, I think this stuff is fascinating. Most of it, I'll never know. None of us will. But I know far more than Aristotle did, not because I'm smarter than he was, but because smart people have spent their lives, generation after generation, adding to our knowledge. Long after I'm dead, ordinary people will know a lot more than I do now. That's how this works.

Anyway, I thought this article was a good demonstration of that.

4 comments:

Chimeradave said...

Wow, if that was made by 14 year olds I can't wait till Henry is 14. Those kids are brilliant!

WCG said...

Ah, that's nothing, John. Henry will probably be doing that kind of thing when he's three. :)

Anonymous said...

>Even vacuum might not be "nothing."

Interestingly, a vacuum isn't "nothing," because a vacuum is "something." It can be identified and differentiated from other things. If a lab purchases a vacuum, how would they know they got what they paid for if there was no way to measure and identify this..."thing"? Vacuum is a thing with meaning and definition, and most importantly, a physically identifiable, existing manifestation. Sounds an awful lot like "something" to me...?

:)

WCG said...

I don't know, Anonymous. A concept isn't necessarily "something." I can pay to have someone remove a tree in my yard, and I can tell when that happens. But is not having a tree "something"? What about not having any matter?

If a lab purchases a vacuum, they're not expecting nothing to be there, but they are expecting fewer molecules than in Earth's atmosphere. And yes, they can test it to tell if they got what they wanted. But that's more the (relative) absence of something, rather than "something" itself.

The problem with identifying "vacuum" with "nothing" is, first of all, one of definitions. We have to be sure of what we're talking about. And since we never encounter "nothing" in our daily lives, that makes it even more difficult. But the concept of "nothing" can still exist, whether "nothing" makes sense in the real world or not.

So, even if a vacuum were "nothing," it would still have meaning and definition, and we'd still be able to tell it apart from "something." Of course, scientists would be a lot more precise with their labels and their definitions than that!

But I'm not a physicist, and this kind of thing is hard to talk about with any kind of precision. Note that this wasn't really the point of my post, either. I'm quite willing to say "I don't know" when it comes to the fundamental properties of a vacuum.

And "I don't know" doesn't imply anything else. It just means that I don't currently know. I can live with that. :)