Guest Post by Frank Meyer
Can you think of a point in your life when something important you had taken for granted turned out to be completely different? I bet you have no trouble coming up with such a point – occasionally, the universe seems to enjoy throwing us a curveball.
You thought you were on solid ground, but suddenly you realize that you are an unwitting participant in an episode of Monty Python’s Flying Circus, as you hear their trademark “and now for something completely different”.
The man who uttered it looks just like your standard TV news anchor – unobtrusive, conservatively dressed, sitting at his desk. Did you misunderstand? What you expect is more of the same! But then the camera zooms out, and you discover that the desk stands in shallow water, and small waves lap around the announcer’s impeccable socks.
Every time you gain a new perspective, your world view cracks and shifts a little. Fortunately, you can adapt – you adjust your model of reality to incorporate the new information. Good or bad, pleasant or unpleasant, you have learned something new.
Of course, some of life’s reminders that we haven’t figured it all out are bigger than others. Today I’d like to tell you the story of one of the biggest such reminders. If this one does not scare you at least a little, you haven’t thought about it enough.
The name of the man who delivered this shocking truth was Ernest Rutherford. He was born on a farm in New Zealand in 1871, a time when the whole of New Zealand had about as many inhabitants as the city of Cincinnati has today.
Young Ernest was exceptionally bright, but there was something about him that was even more important: he possessed a larger-than-life enthusiasm for all knowledge. Whatever the problem, he would not back down until he solved it. He was maybe less of a rebel than Einstein, but in pursuit of knowledge he did not much care for tradition or decorum. When he wanted to know something, he worked harder and thought more deeply than anyone.
He was also lucky to have all the support he needed: parents who believed in him, teachers who helped him develop. Even his girlfriend encouraged him to go where he could go – when he offered to marry her, she refused, but promised to marry him once he had built his scientific career. And marry they did, 6 years later.
So young Ernest entered the field of physics and went right for where the action was: The recently discovered radio waves. Rutherford excelled at radio wave research, conducting a series of successful radio transmission experiments, first in New Zealand, later in England.
There were scientists who said that Rutherford was ahead of Nikola Tesla and even Guglielmo Marconi, the Italian scientist who would eventually “win” the wireless race.
Some said Marconi won because Ernest left the field. But why did he abandon it when fame and fortune were so close? His interest was captured by a series of unexpected discoveries that promised to push the envelope of science even more than radio waves had:
There was Wilhelm Röntgen’s discovery of “X-rays” – which Germans still call “Röntgenstrahlen” in his honor, even though Röntgen himself first named them X-rays. Ernest’s own professor J.J. Thompson discovered “corpuscules”, particles that held a negative electric charge but were many thousands of times lighter than atoms – today we call them electrons. Henri Becquerel, Marie and Pierre Curie discovered “radioactivity”. Signs were piling up that atoms might not be the indestructible little balls practically everybody had thought them to be.
Ernest moved to a Canadian physics institute that had been newly created to research these phenomena. Soon he discovered that radioactive materials gave off different kinds of radiation, which he named alpha and beta rays, and that elements were transmuted when they emitted those rays; eventually he received a Nobel Prize for that discovery.
And now Ernest had his greatest idea. He had figured out that alpha rays were made from an unknown kind of particle, just like J.J. Thompson’s corpuscule rays and Ernest’s own beta rays were made from electrons. Alpha particles were positively charged, and about 4 times heavier than a hydrogen atom. They were easily stopped when they crashed into anything substantial, but they were thousands of times heavier than electrons and carried a lot of momentum, so they could punch through a little matter. Why not use alpha particles to find out more about atoms?
For a long time, the best thinking about atoms had been that they were little balls that stuck together according to the laws of chemistry. With the discovery of electrons, atoms were now thought to look like blueberry muffins – a bulk with a positive charge, and the negatively charged electrons stuck in it like blueberries.
Ernest designed an experiment about the size of a small water cooler: In a vacuum chamber there was a little capsule with a radioactive material that emitted alpha particles. The capsule had a hole through which a thin beam of alpha particles could escape and hit a piece of gold foil so extremely thin that it was practically translucent. The alpha particles, heavy and fast as they were, would have no trouble punching through the few gold atoms in their path. Behind the foil there was a small fluorescent screen the experimenter had to watch using a microscope built into the wall of the vacuum chamber, to count the little flashes of light created when alpha particles hit the screen.
Ernest thought the alpha particles would punch through the foil more or less in a straight line. A few would be deflected just a little, and that would tell him something about how masses and charges were distributed within the atom.
Rutherford was by then important enough to have his assistants Geiger (who would later invent the Geiger counter) and Marsden set up and conduct the experiment. It must have been quite exhausting: the whole room had to be absolutely dark; not the slightest shimmer of light was allowed. The experimenters had to sit in that darkness for an hour or more before the experiment even began, so their eyes would completely adapt to the dark. Only then did they have a chance to observe under the microscope the tiny light flashes from alpha particles hitting the screen. And they had to count lots and lots of them, under different angles. It was even dangerous, although they didn’t know it at the time – the amount of radiation coming from their little setup would have modern researchers hurry for the exits.
So Geiger and Marsden conducted the experiment, and the tiny flashes of light told them something astonishing: most of the alpha particles were barely deflected at all, and that was just what they had expected. But very few, about one in 10,000, did something seemingly impossible: they were deflected by large angles; sometimes they even flew straight back to where they had come from!
Geiger said this about their discovery: “It was quite the most incredible event that has ever happened to me. It was almost as incredible as if you fired a 15-inch artillery shell at a piece of tissue paper, and it came back and hit you.”
Geiger and Marsden had obtained the result, but they didn’t quite know what to make of it – it seemed totally impossible. Had they made a mistake? It was Rutherford who finally, two years after the experiment, broke the limits of imagination and figured it out:
Alpha particles were heavy. They could only bounce back that way if they hit something much heavier than themselves. But mostly they flew right through the gold foil without hitting anything, so this really heavy thing must be very small and hard to hit. This small and heavy target could only be an atomic nucleus tens of thousands of times smaller than its atom, in which almost all the atom’s mass was concentrated.
Ernest Rutherford discovered that everything is basically nothing. Empty space! A complete vacuum!
Our world is made of emptiness, because all atoms are empty. If the gold atom were a muffin the size of a church sanctuary, over 99.9% of its mass would be inside a tiny nucleus smaller than a blueberry. The rest is nothing but emptiness and a ghostly cloud of almost weightless electrons.
It was the most radical discovery! Rutherford’s experiment was repeated by others, its results confirmed. But for years the world’s physicists could not explain how atoms could possibly be stable that way. The negatively charged electrons could only circle the positively charged nucleus of the atom if they were accelerated – otherwise they would just move away in a straight line. But accelerated electrons would radiate away their energy as electromagnetic waves and fall into the nucleus. Why did Rutherford’s atom not collapse? The search for the answer eventually led to the discovery of quantum physics, the master key for the modern world. But we shall not open that can of worms today…
If we could somehow remove the empty space from all our atoms, humanity – all 7 billion human beings on this earth – would fit into a small marble, with room to spare! All the mass would still be there though – this little marble would weigh as much as a good-sized mountain!
Everything around us is nothing but empty space, made to look and feel solid only by a few tiny particles and the effects of quantum mechanics. We, all our things, our entire world, are soap bubbles in an ocean of nothingness.
Form is emptiness, emptiness is form?
Not quite. 100 years after Rutherford, physicists are still working on it. Einstein’s spacetime, virtual particles, dark matter, dark energy, neutrinos, the cosmological constant, the nature of gravity – we have made much progress, but we haven’t figured it out yet.
We may be lost in a vast, uncaring universe. We may not be able to personally participate in the epic struggle to learn its secrets. But this struggle sure is super exciting to watch!
What will be the universe’s next curveball?