LectureHop: Black Hole Duet

Stressed by midterms? Having a bad day? It always helps to think about how tiny we truly are in this gigantic universe, and how we humans (and our problems) are really just an insignificant part of a cosmic order. Last night, Bwogger Alex Tang attended Columbia Astronomy Department’s lecture: “Black Hole Duet – Hearing the Universe for the First Time”. Here are the highlights from that lecture.

If you’re reading this, drop everything you’re doing and check out this 12-second clip right now.

According to last night’s lecture, this video documents the greatest scientific achievement of this generation.

On Saturday evening, Columbia University’s Astronomy Department hosted its twice-monthly Stargazing and Lecture Series, free talks open to the general community. On this particular occasion, astronomy grad student Maria Charisi discussed the recent discovery of tangible evidence for gravitational waves in her talk “Black Hole Duet – Hearing the Universe for the First Time”. Through her lecture, Charisi managed to clarify a dense and immensely conceptual scientific development, and even bring out its intrinsic beauty.

Charisi began with the basics, stating that all objects of mass contain their own gravity. Through Einstein’s Theory of Relativity, mass distorts space-time, releasing gravitational waves in a sort of “ripple effect” out of itself. However, in the scale of things we associate with on Earth, gravitational waves are near negligible in their effects. You, or I, or the grand piano in Lerner don’t possess nearly enough mass to create discernible gravitational waves. If the entire mass of the Milky Way Galaxy were taken, the gravitational wave ripple created would only be about the size of a basketball. Yet, we’re all surrounded by gravitational waves created by cosmic occurrences happening all around us. In other words, we and everything in the universe are constantly being stretched or shrunk in a wavelike fashion.

To find proof of the existence of gravitational waves, therefore, scientists have to focus on astronomical features with an enormous amount of mass, such as neutron stars (giant dead stars) as well as black holes (even bigger dead stars that have collapsed unto themselves). Even while working with astronomical features such as black holes, probes on Earth would have to discern disruptions in gravitational waves by about 1/1,000,000 of the width of a human hair. Doubtlessly, measuring such discrepancies would require instruments of immense precision.

Scientists turned to light as the method of observation, or in other words, the ruler that would measure the effects of gravitational waves. An international assembly of scientists built LIGO (Laser Interferometer Gravitational-Wave Observatory), with two locations in Louisiana and Washington State. LIGO consists of two identical, intersecting arms (4km long each), where in each arm, light is released at one end to be reflected off of a mirror at the opposite end. (see image) At the intersection of the two arms, the lightwaves would then presumably cancel each other out, and create no measurement of light. However, even slight gravitational waves will stretch or shrink the length of LIGO’s arms, increasing or decreasing the distance the light travels across the arm. Affected by gravitational waves, the lightwaves will not match up at the intersection, creating readable patterns.

On February 11, 2016, LIGO at both sites detected a measurable blip in the reading of light at the arm intersection. In other words, a major astronomical event had caused gravitational waves powerful enough to significantly stretch or pull planet Earth, causing a discrepancy in the distance of the arms, and a mismatch in the light readings at both arms. Scientists deduced that two black holes had collided long ago, and that 1.3 billion years later, the gravitational waves from the collision reached Earth, affecting the time-space fabric of everything it encountered. Charisi stressed that this was perhaps the biggest scientific development in our current generation.

The indisputable proof of gravitational waves has opened up a new realm of astronomy. While astronomy once consisted purely of electromagnetic evidence (lightwaves and other electromagnetic waves), the precedence has now been set to include evidence of gravitational waves. Charisi ended her lecture by providing the audience with a metaphor for the significance of the proof of gravitational waves. Before February 11, 2016, astronomy would have been a muted video of an orchestra, a purely visual, uni-sensual field. The proof of gravitational waves has added an additional dimension to astronomy. Now, astronomy is a video of an orchestra with all of its gorgeous music, becoming at once visual and aural, a multifaceted specialization of human inquiry.