Letter 2: John Mather replies to Minnie Mao about the joys of discovery

Dear Minnie,

Thanks for your letter! I like to be called John; I’m still not used to formal titles. I enjoyed meeting you and now your letter tells me a bit about you and your trajectory so far and your love for doing science.

My biography is already rather public since the Nobel, so I won’t repeat it here. But some of it will come in to the answers to your thoughtful questions. You noted that there are two big groups of astronomers: the theorists and the observers. There will always be both, and since our nature is competitive if not combative, both groups will always be claiming that they are more important (and more intelligent). Don’t worry about that.

I would add that there is another group, those who enjoy building the instruments and the telescopes that are behind the great discoveries. Their numbers are smaller these days than the number of observers and theorists, but it was not always so. Many years ago, if you wanted a telescope, you built it yourself. Then telescopes got so big and lasted so long that it was no longer necessary to build your own. But somebody still has to build them!

My own passion for physics and astronomy has a lot to do with a desire to build things. When I was a teenager I learned a lot from the Scientific American monthly feature called The Amateur Scientist, and I borrowed the 3-volume book series Amateur Telescope Making from the library over and over again. I did build a small telescope, but I didn’t have the patience to grind a mirror –- I bought that. I also loved thinking about electronics, and I wanted to be a ham radio operator, so I assembled a Heathkit AR-3 radio receiver (with vacuum tubes!) and read the ARRL Handbook from cover to cover, over and over. That then led me to study math, so I could calculate things. When I saw the power of math, I wanted to be a theoretical particle physicist in college and grad school. I found a chance to do lab physics and I really liked it. It’s still a wonderful field, now maturing, to build amazing hardware to measure the cosmic microwave background radiation.

There’s a wonderful book by Martin Harwit called Cosmic Discovery that lists the greatest discoveries in astronomy, and shows what made them possible. In almost every case, the new discovery came from new equipment, and in a pretty large fraction of cases the equipment was designed for some other purpose. So I see a path to great discovery: imagine a measurement that could answer a question, and build something to make the measurement. Then, either you answer the question, or you find something new. But in either case, it will be something nobody else could do. Have you given any thought to good strategies for making your own discoveries?

That leads to your other question: what will be the most important discoveries with the James Webb Space Telescope (JWST)? Of course I don’t know specifically, but it seems that surprise is part of importance –- if everyone knows something already, it is not a discovery. The Nobel prizes very often are for something completely surprising to both theorists and observers. A fundamental fact of nature is that it is unstable and chaotic, whereas our minds are only extrapolating from what we know. (You can read my little essay about this.) No theorists and no observers predicted the correct story for galaxy formation before the Hubble Space Telescope was launched, neither group predicted cosmic dark energy or dark matter (though Fritz Zwicky saw evidence for dark matter in the 1930s), and neither predicted the nature and abundance of exoplanetary systems. My friends doing numerical simulations of stars and galaxies in supercomputers agree that they are not going to predict what we find with any certainty –- the complexity is just too great. And after all these years, we still have a hard time making a theoretical supernova explode.

So, I think the JWST will lead to some great surprise that nobody is even thinking about today. Perhaps, you will be the one to find that surprise.

With best wishes for your new role as a Discoverer!

John Mather

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