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Physics, philosophy and the space in between

| Tuesday, September 20, 2016

On an average night at Notre Dame I can usually see about 30 stars, 50 if I manage to squint through the light pollution. Last Tuesday, scientists at the European Space Agency (ESA) released a data set from a spacecraft that found 1.1 billion of them.

It was the first set of data to come out of the Gaia mission, an ambitious project that aims to pinpoint the location of over a billion Milky Way stars. In a nutshell, Gaia is a 5,000-pound spacecraft with two telescopes on board, all of which rotates slowly as it orbits the Earth about a million miles above us. As they spin, the telescopes take sweeping images of our sky, recording the position and brightness of every star they see. Over its five-year mission Gaia will survey each star about 70 times, allowing scientists on earth to track celestial movements. The spacecraft is capable of incredible accuracy, and can identify light that is 400,000 times fainter than can be seen with the naked eye — which explains why where I see 50 stars, Gaia sees 50,000.

Just like sunlight is fractured into a rainbow by water droplets, stellar light captured by the Gaia telescopes is fractured into a color spectrum. From this spectrum scientists can determine the chemical composition of the star, and from there estimate its age. Together, this data creates a so-called age map of the galaxy, allowing researchers to trace back the history of the Milky Way and ultimately get at the fundamental questions behind the Gaia mission: Why does our galaxy look the way it does, and how did it form in the first place?

Of course, humans have been asking the how-did-we-get-here type of questions for centuries. Who here has never looked up at the night sky and wondered about our place in the cosmos? Thinking about how our little marble of a planet got itself lodged in this particular corner of the Milky Way is, for most of us, a more philosophical line of questioning than one in search of a hard and fast answer. But the scientists behind programs like Gaia are looking for a hard answer, and it’s quite likely that they’ll get it. And when questions that used to be purely rhetorical suddenly have quantitative answers, what does that mean for philosophical thought?

Philosophy and science haven’t always gotten along, and the last decade has seen that divide deepen. Physicists in particular seem to draw the ire of their fellow silent-lettered department, and many famous physicists have disparaged philosophy as more or less obsolete (or in the stronger words of Stephan Hawking, “dead”).

But it was Neil deGrasse Tyson, the famous astrophysicist and science educator, who surprised me the most. In 2014, he gave an interview in which he called philosophy and philosophical questions “useless” and “distracting,” and received an amount of well-deserved backlash. I was surprised because Tyson is also the speaker of one of my absolute favorite quotes:

“We are all connected. To each other, biologically; to the Earth, chemically; and to the rest of the universe, atomically.”

To me, that sounds like a musing on the fabric of our world. And while science can now provide an answer to what that fabric is, it was philosophy that first posed the question, and Tyson’s comments on that answer wax philosophical themselves. If you ask whether or not all matter is made up of the exact same building blocks (that is, atoms), science can definitively answer yes. If you ask whether or not that means that I have an inherent connection to all other matter — well, first you have to define the word “connection,” and then probably apply some heuristics, and suddenly the conversation starts to shy a little closer to philosophy than quantum physics. Perhaps Tyson is more a philosopher than he cares to admit.

As a scientist-in-training, I can say with certainty that the more I learn about how the world works, the more questions I have about it. Sifting through the Gaia data only makes me think more about humanity’s place in the cosmos, and since science can’t yet fully answer those questions, I have no choice but to wax philosophical myself. In doing so, another round of questions is raised that science can attempt to answer, until it hits a wall and we again turn back to philosophy, and so on and so forth. A basic understanding of how our galaxy formed will only open the floodgates to a whole new set of questions for science to answer, and it will be the philosophers, amateur or otherwise, who ask them. To quote another famous physicist — that, is Albert Einstein — “The independence created by philosophical insight is — in my opinion — the mark of distinction between a mere artisan or specialist and a real seeker after truth.”

The views expressed in this column are those of the author and not necessarily those of The Observer.

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