I had all sorts of light-related fascinations when I was a kid — that light had a speed at all, for starters, and that it was so unimaginably fast, yet also finite and measurable. I knew the moon was a light-second away, the sun eight light-minutes, and Proxima Centauri, the nearest star, 4.2 light years. I knew the Milky Way, one galaxy of billions, is 100,000 light years side to side.
Light helped me finally grasp the real immensity of the universe and my own infinitesimalitude.
Light is SO much faster than (pfft) sound — almost a million times faster — which is why lightning is already kicking back with a light beer when thunder comes panting up behind.
This stuff gave me endless fodder for discussion on first dates. It also took care of second dates rather neatly.
When it came time to marry, I limited the pool to those with no more than two degrees of separation from the speed of light. Fortunately my college friend Becca attended the same high school as Nobel laureate Albert Michelson, he of the Michelson-Morley experiment, which laid the groundwork for special relativity by showing that light weirdly measures at the same speed even if you are moving rapidly toward or away from the source.
Becca and I were married in a San Francisco Lutheran church with You-Know-What streaming through the windows.
Our kids have picked up the thread. As we drove home from his football practice four years ago, Connor (then 12) asked why time slows down as you go faster. (The previous week we had discussed the very cool Hafele-Keating experiment in which cesium clocks flown around the world differed from identical clocks on the ground by a few nanoseconds. I think I spotted the exact moment during the practice that he was thinking about Hafele-Keating instead of Offensive-Lineman.) I said our velocity through space plus our velocity through time equals the speed of light, so the faster you go through space, the slower you necessarily go through time.
In less than five seconds, he said, “So light doesn’t experience time, then.”
Holy buckets. I’d never thought of it.
Last week, standing in the dark waiting for the school bus, I discovered that I’d never shared with Delaney (9) the insanely cool fact that many of the stars we see probably aren’t there anymore. Some may have blinked out before the dinosaurs went extinct, but the end of the column of photons, even at 186,000 miles a second, still hasn’t reached us. Tomorrow morning we might suddenly see a “new,” bright star in the sky, which is actually a nova that happened millions of years before. That’s what nova literally means — a new star. But it isn’t really being born — it’s dying.
She made all those astonished, comprehending sounds I’ve come to love, and we quickly re-combed her hair as the bus pulled up.
On the heels of last month’s announcement that the speed of light might have been exceeded by neutrinos at CERN, Becca took the opportunity to give her second graders a little insight into how science works. “All these years we thought light was the fastest thing possible,” she said. “Even Albert Einstein said that was true. Now maybe, just maybe, scientists have found that it’s possible for something to go even faster. First they have to test and test again to be sure, and if it is, they’ll say, ‘Wow, we were wrong. We have to change our minds.'”
It’s true that we’re capable of upending our Newtons and Einsteins when the evidence insists, but of course it never happens quite as gladly as we sometimes claim. Individual scientists are just as prone as the rest of us to kick and scream and bite to protect their favorite conclusions, until the collective enterprise of science itself busts them upside the head. The important message for these second graders, though, is that science contains the ability, the means, even the willingness to change its conclusions in light of new evidence, despite whatever preferences individual scientists might have. (The CERN scientists assumed they made an error in measurement, by the way, something that has happened before — and a team in the Netherlands think they’ve found the error.)
All this light conversation brought me back to experiments I conducted around age seven, just inside my front door in St. Louis, Missouri. The edge of the glass on our front storm door was beveled, which formed a little prism, which at a certain time of day threw a tiny, intense rainbow on the floor.
I decided I was going to catch that rainbow. In a shoebox.
In what may be a perfect illustration of the seven-year-old mind, I knew that I would have to move faster than light to do this, but had not received the memo specifically prohibiting such a thing.
I found a shoebox and held it above the rainbow. I slowed my breathing and concentrated…then CLOMP! brought the box down on the rainbow.
Too slow. The damn thing was on top of the box.
I’d do this for a good half hour at a time before giving up — but only for that day. I remember thinking maybe light was a little slower in the winter, which was why it was colder then. So I tried in January. Even then, it was always just a liiiittle faster than I was, and the rainbow appeared on top of the box.
I eventually gave up my dream of catching the rainbow. But these experiments at CERN have given me hope. I just need to find a box made of neutrinos, and I’m back in the game.