THE SOUTHWORTH PLANETARIUM 207-780-4249 www.usm.maine.edu/planet 70 Falmouth Street Portland, Maine 04103 43.6667° N, 70.2667° W Founded January 1970 "Officially listed as one of the greatest wonders of the ancient world." THE DAILY ASTRONOMER Wednesday, January 27, 2016 Moon in a Soup Can You realize that for awhile, we believed we were about to puzzle it all out. Ever since Thales of Miletus, Aristotle, and those lot combined insatiable human curiosity with disciplined philosophy, we've striven to completely understand our physical reality. From the unfathomably small subatomic particles to remotest stars, we happy presumptuous humans thought ourselves close to having the entire cosmos wrapped, shipped, and its manifest filed. And, then our understanding collapsed, leaving a largely mysterious Universe to regard us quizzically as though challenging us to try again. What could be better? Our confidence peaked toward the Victorian period's end, in the 19th century's last decade. Just as the patent office declared that all that could be invented had been invented long before airplanes, computers, and satellites transfigured our lives, the pre-Relativistic, pre-quantum science community predicted that twentieth century physics would be a crashing bore. They envisioned sad, frustrated, and ultimately pathetic 20th century physicists spending their time measuring the gravitational constant with slightly more accuracy and wasting themselves in taverns, lamenting that they hadn't been born two generations earlier. The reality differed from the prediction. The two most significant 20th century advances were the Relativity theories (Special 1905; General 1916) and Quantum theory (1900…and many other years). Today, we fly past the relativity and leap into the quantum. For, even though astronomers astonished humanity with its expansive fields of galaxies, more profound surprises awaited us as we scrutinized the atomic realm. Just as our Milky Way Galaxy was seen to be a mote amongst many, even though we once believed it to enclose the Universe entire; our comfortable notion of a minor solar system in every atom was shattered irrevocably: electrons as clouds instead of planets; a nucleus weighed down by phantasmic quarks and between them a spatial expanse as vast, comparatively, as that separating a stadium's perimeter and a marble on the 50-yard line. Astronomy was showing more space beyond. Quantum theory was revealing more space within. We know the word "quantum" conjures exotic notions such as time travel and body switching, but the essence of quantum theory is simple: that energy is discrete, not continuous.* Energy travels in small "packets," or quanta. That light energy propagates in bundles, called 'photons,' while retaining wave-like properties is quantum mechanics' basis. And, moreover, material objects, themselves, exhibit wave-like behaviour, as well. For instance, electrons are hardly little negatively charged spheres whirring around a nucleus, but instead are "smeared out" along specific energy levels. Apart from defining an atom's vague, changeable perimeter, electrons also impart "solidity" onto objects that are predominantly empty space. Strike a table with your hand. Both your hand and the table are essentially nothing: the protons, quarks, and other material components occupy a minuscule volume of the space within both. The photon exchange between electrons makes them seem solid. This electron interaction solidifies our nearly empty world. Ironically, even though vast space separates celestial bodies, vast space comprises these celestial bodies: except, of course, for the neutron stars. These stellar remnants form when a highly massive star collapses onto itself. This collapse compresses interior material down into a volume no larger than a city. (Imagine the material equivalent to half a million Earths contained within a Manhattan-shaped sphere.) These unfathomably dense neutron stars, or pulsars, are devoid of empty space and therefore are the only examples of solid objects that are completely solid. Comprehending such densities is, well, impossible for most of us. Such extremes defy intuition, and we're left with analogies that might help us appreciate these densities, if not understand them. Holding a teaspon of neutron star matter would be difficult: the mass of this small teaspoon would equal that of an entire mountain.* And, for another more stunning example, if you compressed the Moon down to a neutron star's density (i.,e. the Moon without any empty space within it), you could place it inside a…well, actually, you probably know if you read the title. And, here's the kicker: all the matter of all the humans who've ever lived and those now living would, if compressed, fit inside a sugar cube volume. Humanity all but vanishes if its empty space is kneaded out of it. How lovely to think that existence is, indeed, an airy nothing *"Discrete" vs. "continuous" The number of people in a room is an example of something discrete, as people are separate objects. A straight line is continous, as it consists of an infinite number of points.