![]() ![]() Since the total charge of the atom had to be neutral, then the electrons must be very very tiny and swimming, orbiting or dancing around that nucleus in a loose cloud. And this "nucleus" must be positively charged. Related: The 5 Most Ingenious Experiments in Astronomy and PhysicsĪmazing! What were these little particles telling us about gold atoms? The only explanation that made sense, the researchers concluded, was that the vast majority of the mass of the atom was concentrated in a very small volume. And once in a great while (about 1 out of every 20,000 shots, and yes, the scientists counted manually), an alpha particle ricocheted off the gold, slammed back the way it had come. But every once in a while, the particles would careen off in a random direction. These particles are small, heavy and fast - the perfect scientific bullets.Īs the researchers engaged in target practice, most of the alpha particles sailed on through the gold as if it were tissue paper. And they shot very tiny bullets: alpha particles, which are charged atoms of helium. The scientists chose gold because they could make very thin sheets of the material, meaning the gang could rest assured that they were probing atomic physics. It was Thomson's own former student Ernest Rutherford, together with his own students Hans Geiger and Ernest Marsden, who decided to shoot things at gold to see what would happen. Most importantly: How can something be smaller than an atom, and what does that mean for the structure of atoms themselves? It was up to the next generation of scientists to settle the puzzles raised by Thomson's results. These "electrons" (everybody else's word) were truly remarkable. earned his Nobel Prize: These "corpuscles" (his word) were about 2,000 times smaller than hydrogen, the lightest known element and therefore the smallest atom. And it also meant that cathode rays were made of the same stuff as electricity.īy comparing the amount of ray deflection in the electric fields versus in the magnetic fields, Thomson could derive some math and work out some properties of these charges. Fascinating! That meant that the glowy bit was connected to the charges themselves if the light was somehow separate from the charges, then it would sail straight on through, regardless of the field interference. ![]() The cathode ray would bend under the influence of both electric and magnetic fields. If charges were somehow involved in this cathode ray business, then you'd better believe they'd listen to those fields.Īnd listen they did. What made the glow? How were charges - which, at the time, were known to be linked to the concept of electricity but otherwise mysterious - connected to that glow? Thomson cracked the code by a) making the best dang vacuum tube that anyone ever had and b) shoving the whole apparatus inside superstrong electric and magnetic fields. This phenomenon raised questions for physicists. ![]() If you stick a couple electrodes inside a glass tube, suck all the air out of the tube, then crank up the voltage on the electrodes, you get an effervescent glow that appears to emanate from one of the electrodes, the cathode, to be exact. In the late 1800s, he become enraptured with ghostly beams of light known as cathode rays. Operating in parallel with Einstein was a wonderfully gifted experimentalist by the name of J.J. These "united states"Īnd just when people were getting comfortable with the size of these minuscule morsels of matter, thinking that these had to be the smallest things possible, someone came along to complicate it. In other words, Einstein gave us a way to weigh an atom. And by putting this connection on solid mathematical ground, he was able to provide a pathway for going from something you can see (how much the grain moves around in a given amount of time) to something you can't (the mass of the particles of the fluid). By treating the fluid as something composed of atoms, he was able to derive a formula for how much the innumerable collisions from the fluid particles would nudge that grain around. And after a few carefully executed experiments, Brown realized that this has nothing to do with air or fluid currents.īrownian motion was just one of those random unexplained facts of life, but Einstein saw in that a clue. If you drop a large grain inside a fluid, the object tends to wiggle and jump around completely on its own. He was interested, in particular, by the problem of Brownian motion, first described way back in 1827 by Robert Brown (hence the name). Just like all the other physics that he became a fan of, Einstein revolutionized them. This was pretty compelling, and Albert Einstein was a big fan of these kinds of physics. ![]()
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