Physics in a Nutshell

For all antiquity nobody knew what stars were. When Copernicus realized that the sun, not Earth, is the center of the universe, the stars were placed on a far distant giant sphere. Some thought they might be holes through which shone the light of heaven. Copernicus, who was nineteen when Columbus first sailed across the Atlantic, started the Scientific Revolution, followed by Galileo and Newton, and the Age of Discovery began.

Can you picture something nine million miles across and yet is invisible? No, and neither can I or anyone else. It is a supermassive black hole at the center of our Milky Way galaxy, some 27,000 light-years away. The sun is eight light-minutes away, and the next nearest star about four light-years away. We are in an outer suburb of the galaxy. In contrast, there are dozens of stars within one light-year of that supermassive black hole, orbiting around it at speeds up to 8,000 kilometers persecond!

The moment our universe came into existence fits one part of the definition of a miracle very well, as does the appearance of the imbalance between matter and antimatter.

Prominent among physics’ many mysteries is dark matter — strictly speaking invisible matter — but the name stuck. The evidence is overwhelming that there is about five times more mass in the universe than we can see in the stars, planets, gas and dust.

On Sept. 1, 1859, the English amateur astronomers Richard Carrington and Richard Hodgson noticed an extremely bright spot on the sun, now called a flare. That night the sky lit up with brilliant auroras over much of the world: northern lights as far south as Cuba and southern lights as far north as Santiago. In the U.S. it was bright enough to read a newspaper at midnight, the whole sky eerily glowing with beautiful changing colors.

The top quark is the heaviest known elementary particle, as small as an electron but 340,000 times more massive! We don’t know how small those particles are, only that they are smaller than 1/1000th the size of a proton which itself is 1/100,000th the size of the smallest atom, hydrogen. Millionths, billionths, … soon we’re talking small numbers!

What is time?

“What’s done cannot be undone.” Look to Shakespeare for a great quote. He had Lady Macbeth murmur these simple but profound words to herself. Who does not wish they had done something differently? But the past is past. A broken teacup will not put itself back together. A dissolved sugar cube will not reassemble itself.

January’s column was about snowflakes; this is about an ice cube, but a huge one called – wait for it – IceCube. Each side is 1 kilometer, 1,000 meters, so the volume is one billion cubic meters, and it weighs a billion tons. Scientists wanted a massive block of clear ice to detect mysterious neutrinos coming from far away in the universe. These particles interact with matter so rarely that 99.9999% pass right through that block leaving no trace. But one in a million hits a quark, much smaller than a proton, creating a shower of new particles, which make flashes of light in the ice.

As I write this in mid-December there is no snow here – probably a trend – but people around me are singing “Let it Snow” and dreaming of a white Christmas. Snow is wonderful stuff, considering that it is “just” frozen water, but when you examine snowflakes you see beautiful crystalline forms usually with six-fold symmetry, and each one looks different.

One night in 1939, Professor Pierre Auger’s daughter asked him, “Papa, what are you doing?” In French, of course. “I’m studying the sparkles on the roof,” he said, with a twinkle in his eye. He had discovered that very energetic subatomic particles coming from outer space, cosmic rays, smash into atoms in the upper atmosphere making huge showers of particles that reach the ground.