Maximiliano Isi ’14, a Ph.D. student at Caltech, works on one of the teams of scientists that first detected gravitational waves in September 2015. When those teams detected the collision of two neutron stars this past October, they documented an event that could change much of what we know about how the universe works. Isi was interviewed by Editor Joseph Wakelee-Lynch.
What are gravitational waves and how are they formed?
Gravitational waves are ripples in the fabric of space-time. If you think of space-time as the surface of an ocean, imagine throwing a stone in. You’ll cause ripples that will propagate outward from where the stone fell. Similarly, in space, if you shake a configuration of matter and move it very quickly, you will create variations in the structure of the space and time around it that will propagate outward. Almost any accelerated configuration of mass will create these ripples. If I shake my fist back and forth, that will create gravitational waves, but the effects are so mind-bogglingly small as to be undetectable. So, to create waves that have an effect that we could detect, we need extremely dense objects moving very fast. The densest objects that move the fastest in the universe are black holes.
You and your colleagues detected gravitational waves caused by a collision of black holes, correct?
Black hole collisions are some of the most powerful energetic events in the universe. There is no way to actually see them happening directly. The only way to see them is by observing these gravitational waves. After the event happens, the waves will propagate outward and travel millions of light years, and eventually this ripple will go through the Earth. So, for the first time on Sept. 14, 2015, our experiment detected this signature. One of the reasons it’s important is that it is the opening of a new era of observation. This is a tool that allows us to study the universe in a completely new way.
Can gravitational waves tell us about the first moments of the Big Bang and reveal even more about the origin of the universe?
The observations we have done so far do not tell us about the moments close to the Big Bang. The universe is 14 billion years old. Because light was not able to propagate in the early universe, we can only see as far back as 379,000 years after the Big Bang. But gravitational waves almost do not interact with anything. That means we can trace them farther back, up to seconds after the Big Bang, because they were not impeded in their propagation earlier on. That’s going to be very important in cosmology and other areas in physics and astronomy, but we’re not there quite yet.
Is it possible that events that generate large amounts of energy could take place close enough to our galaxy that the impact would have a noticeable effect here on Earth?
In terms of gravitational waves, the answer is no. You’d have to be rather close to feel anything and to be that close is bad news. If you were close enough to feel it, it would probably tear you to shreds. It is a real, physical stretch-and-pull.
What do you hope to discover or learn as a scientist before you reach the end of your life?
That’s a tough question because I don’t know what’s out there. We are all hoping to be surprised. Sometimes the public’s perception of science is that it’s fixed, something that is set in stone. That couldn’t be further from the truth. Scientists are constantly looking to be proven wrong. So, it would be amazing in my lifetime to find a clear indication of where our theories are wrong, something that doesn’t fit in with what we know and expect. That’s always the most fertile, most exciting time. We can rethink, advance and push forward. That would be amazing: Being there for something completely new would be great.