For a few years I've been been asked to talk to speak to a science class at a local high school. I've always chosen the topic. Usually I ask a few kids in the class a few questions and go from there, In the past few years it's been global warming, but this year I was warned not to go there due to political sensitivities. There were about eighty kids from a few chemistry, biology and physics classes.
I took my peanut butter cookie fee and asked a few questions that didn't go anywhere. Then I asked how many have seen the Milky Way. Only a quarter of the hands went up, but I continued.. "How many have seen Andromeda?" Now we're down to five hands, but I continued. "Does anyone know how far you can see with the naked eye?" One hand - probably the class nerd. "Two million light years" She looked at another kid who raised his hand for Andromeda - "You have too."
I had my topic and enough of an audience. Here's roughly what I think I said. It's as unedited as it was when I talked but it was literally working for peanuts.
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Something remarkable has taken place in the past fifty years. Aha Internet, you say. It's almost that old after all, but I'm thinking about something deeper - cosmology became a science.
It's sad there's so much light pollution these days. Not enough of you have seen the Milky Way. You really need to fix that. Within a four hour drive from here you can find places where it'll cast shadows on dark moonless nights. Being out then is intoxicating enough that you have to be careful or you'll lose track of time and the Sunrise will be on you. Trust me - you need to do it.
When you're out with the stars and your thoughts the big questions flow. Where did it come from, where is it going, how big is it, who else is out there...? Religion and science started a sometimes star crossed dance over stories about the time of Copernicus. Science was able to settle some of the questions - like the Earth is sort of a sphere and goes around the Sun, and the Sun is four hundred times farther and larger than the Moon.
Then Galileo Galilei turned one of those new fangled telescopes towards the sky and saw the moons of Jupiter move. A window opened. Our imaginations are nowhere near as wild as Nature. Discoveries came with better telescopes and more people joining in. Discoveries including a comet that told us Newton was on the right track and the accurate recording of the positions of things that moved in the sky.
Knowing where things would be in the sky turns out to be useful if you're trying to navigate a ship and doubly so once accurate ship's chronometers were invented. Astronomy now had commercial value and the science part lost some luster. That is until a physicist put a prism on a telescope and started to learn enough about the light that these tiny dots in the sky were giving us a good idea of what they were made of. Helium was discovered on the Sun before it was found on Earth. The field of astrophysics was born. That's sort of a love of mine.
Now it was possible to deduce much more. That there is more to space that just the Milky Way, which our solar system is part of and as the twentieth century unrolled we learned the Milky Way is but one of many galaxies and that it is all expanding. We learned that our Sun is very old and the Universe even older. We learned how stars make light. Then the bomb shell, about fifty years ago, was the discovery of the remnant of the Big Bang. A radiation that is everywhere in space - including in you.
The last discovery came about forty years after radio telescopes were invented. Both the invention and the discovery took place at Bell Labs and both were quite accidental. Radio and visible light are closely related - they're both electromagnetic radiation. You'll learn all about that in physics if you haven't learned it already. Radio waves just have a much longer wavelength than visible light. Radio astronomy vastly widened our electromagnetic radiation widow to the heavens.
Every time you open a new window on the Universe you find the unimaginable.
Now we're listening to the sounds of the Universe. There's a new kind of telescope called a gravity wave interferometer. Einstein theorized that gravity is quite a bit different from the force you might think it is. Basically space and time send ripples made of space and time like waves traveling through the Universe at the speed of light. If you shake a really big mass - like if you crash a couple of black holes into each other - the ripples can be pretty big. When a ripples passes by you get a little thinner and then a little thicker and then go back to where you were. That's what the telescope - it's called LIGO - measures. Even for crashing black holes the effect is tiny and the most difficult measurement that anyone's attempted. And you can even play the vibration back once you've separated it from the noise and amplified it a lot. It sounds like a little chirp. An information laden chirp.
There are huge puzzles to solve. Only about four percent of the Universe is made up of the matter we're family with and are made of. As things go we're pretty rare. Nearly thirty percent is dark matter. It hasn't been directly found yet, but it evidence for it's existence is great. We think it's another sort of elementary particle - not like protons, neutrons and electrons, but something very different. What makes that exciting is it isn't out there, but it's right here - in this room and in you. That means we can build detectors deep underground to look for them.
And it gets even stranger.
The dominant form of energy in the Universe is called dark energy - almost seventy percent of the energy of the Universe. And I'll leave you with this. If you take away all of the matter in space and all of the radiation in any form you should be left with nothing but empty space, right? There's nothing there, but it still weighs something. And we don't understand why.
Isn't that beautiful? The most important thing about science is the questions. Answers are just stepping stones.
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They didn't throw rotten fruit, so I was happy.
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