On Gravitational Waves

By Jenny Lee (HMC) ‘19
Design Editor, Science Enthusiast

In 1916, Albert Einstein predicted the existence of what were ripples in the curvature of spacetime that propagated across the universe in the form of waves. Called gravitational waves, these tiny pulsations can be compared to the waves formed by a pebble thrown into a pond. The differences lie in that those waves are moving at the speed of light, and the pebble is equivalent to enormous objects like black holes, whose incredulous accelerations are enough to make an impact in spacetime itself.

Let’s step back a bit. We naturally think of things existing in three dimensions. As we learned in math, this is commonly referred to as the x, y and z axes, or height, width and depth. But in reality, we are living in the fourth dimension, time. Spacetime is essentially the crossover of the three dimensions and time, so all of us are actually point on the four-dimensional coordinate system that looks like (time, x, y, z).

Gravity, as most of us know it, is the force that pulls on other things. Almost everything in spacetime has gravity. Imagine it being something like an aura around an object, except instead of radiating things away, it’s pulling everything around it to itself. The bigger the object, the stronger this force is, and thus the greater effect it has on spacetime.

As with most things in our universe, we are very small objects slowly cruising along in spacetime, not making much of an impact. But when huge things like black holes or supernovas appear as a result of exploding stars or galaxies, spacetime becomes distorted. Their huge gravitational forces suck in everything like a vacuum, including spacetime itself. This causes a disturbance that affects the rest of the universe in ripples.

Each time a ripple rolls along, that part “folds” in and thereby changes the distances between two points. You can remodel this simply with a piece of paper. Take the paper and lay it flat on the table. Mark two points, anywhere with reasonable white space between the two. Now slowly push either side of the points together so that the paper “folds” up in between the two points. You can see that the two points have gotten closer, despite that they’re stationary on the paper. The act of folding is comparable to the vacuum that sucks in everything.

The greatest problem with detecting gravitational waves was that these ripples were too small for it to be detected with certainty. In fact, these ripples were so small that LIGO, the Laser Interferometer Gravitational-wave Observatory, set deep underground in rural pastures, had trouble distinguishing signals of the actual wave from vibrations caused by tumbleweeds, hundreds of feet above the detectors.

So why is this discovery so important? Our current method of looking at the universe is through telescopes, which gives close to no information about black holes. Telescopes work off of light, but black holes consume even light, rendering them useless. Gravitational waves, however, introduce an entirely new spectrum of ways to observe things. This would answer so many questions that were left unanswered because of simply not being able to “look” directly at a black hole. In fact, in the very first week of discovering these waves, scientists were able to discover that black holes orbit around each other and merge to form one big black hole, a revelation itself in the field of astrophysics.

In addition, this furthers the incorrectness of the Newtonian theory of gravitation, which postulates that physical interactions of gravity happen at infinite speed. Simply put, this states that gravitational waves cannot exist. Instead, this confirmation puts us closer to the physics of general relativity, which, alongside quantum mechanics, composes the physics scientists work with today. As of February 11, 2016, scientists have taken an immense step forward in advancing physics as a whole. This is easily one of the greatest discoveries in all of mankind’s achievements in science, and the excitement is only uphill from here.