‘Women and Science’ Series – How Einstein’s theory of gravity is helping me see the world
I never wanted to travel much for work. Now I’m sitting in a trendy café in Stockholm writing about how I got here. The idea of travelling all the time turned me away from a potential career as a pilot because I didn’t like the idea of living out of a suitcase. Eventually I landed in an undergraduate science degree, saw the list of elective units and thought “huh, Astronomy. That sounds cool.” Fast forward 8 years and I now fill out forms with my occupation as “Astrophysicist”. Something I didn’t know was that travel is a big part of the job.
I basically make fake Universes. I study how the largest clusters of galaxies formed over the entire history of the Universe using a supercomputer (which is literally just a really big, powerful version of what you’re using to read this right now). But really, I just write computer code and do a lot of maths. That doesn’t sound as cool, though.
The thing is, most people use the wrong theory of gravity to do this. Well, it’s not “wrong”, it just might not be the best one to use. Most people use Newton’s original apple-on-the-head theory of gravity, which says that objects with mass are drawn together by some invisible force. This was the first real explanation for why we don’t all fly off into space. Then Einstein came along and thought: “Actually, it’s because space is curved in such a way that makes things move towards each other”. Objects like the Sun are essentially sitting on top of a kind of fabric and bending it, making smaller objects move on curved paths around them. So, our idea of a “straight” line isn’t always “straight” anymore. You can visualise this by taking a trampoline and sitting in the middle of it. When you bend the trampoline, an apple that was sitting nearby on the trampoline will start to move towards you. This is why we don’t float off into space, because the Earth bends space just like the trampoline (and we’re the apple). Say your friend rolled an apple across the trampoline instead. Its path would curve as it moved past you. This is why we orbit the Sun.
Turns out we can use Einstein’s theory to describe the motion of everything from apples to galaxies. Newton’s theory works pretty well for apples, but it starts to break down as we try to describe bigger things. I’m trying to figure out when we need to use Einstein’s theory instead, and whether this makes any difference to how our Universe looks.
I never thought I would be where I am today. Not Stockholm, but in my career. I love my job. Especially the work trips. I’ve seen some amazing places and always learnt something or met someone new along the way. I guess the reason I didn’t want to be a pilot was… I didn’t want to be a pilot.
I remember clearly the day of my last maths exam in high school, being so excited that I would “never have to do maths again”. Well, a message to my past self: Sorry… but not really. I guess when you find something you really love doing, you can sit back, relax, and watch a movie rather than having the lives of hundreds in your hands.
Dr Hayley Macpherson is a postdoctoral research fellow at the University of Cambridge. She is interested in the evolution of the entire Universe over all of time, but specifically which theory of gravity best describes this process. She studies this using numerical simulations on huge supercomputers, but also gets to travel a lot, too.