Author: Kyle Batra

I wrote my first passion blog on gravitational waves and how we had detected them for the first time a year ago, and that the Nobel prize in physics had been awarded to the researchers who had made this discovery. The main criticism of this blog post is that I didn’t go into detail on what the implications for this groundbreaking discovery were.

It just so happened that this past Monday a new breakthrough was announced from NASA and the LIGO team who detect gravitational waves. They had detected something new- two neutron stars colliding. I discussed last time about how gravitational waves are detected by LIGO so I won’t do that here, but it is important to note that what was detected by LIGO was the ripples in spacetime.

First I want to talk about why these gravitational wave discoveries are important. Einstein theorized about gravitational waves many years ago, and the detection of them confirms many of his theories which had not yet been proven yet. This means that scientists can treat them like fact and build of those theories with absolute certainty that base way of thinking is correct. The discovery of gravitational waves also brings to the forefront a new type of astronomy. Many things in the universe are difficult for astronomers to observe, a simple example is black holes because their gravitational strength is so great that light cannot escape its event horizon. So the LIGO detectors give astronomers a new way to observe these phenomena without using regular telescopes. Finally, the LIGO detectors can be used as mean to confirm other discoveries and observations.

This is exactly the case in what was announced on Monday. LIGO had detected two neutron stars colliding, and then the Hubble Space Telescope was able to confirm by looking in the direction of the event and detecting the massive wave emission that was caused by the neutron star merger. What is a neutron star you may ask? A neutron star is a collapsed star of a star that was once 10-30 solar masses. However, it is so dense that that mass is compacted in a sphere the size of a city on earth. Just think of that- 20 suns inside a sphere the size of Philadelphia- it has a large gravity, which is why the gravitational waves were detected during the merger. These mergers between neutron stars are important to us because most heavy elements in the universe come from the energy release when neutron stars merge. So you can think of the merger that LIGO and Hubble observed as an explosion of gold and platinum and other heavy metals. Your phone has gold in it, and that gold was probably created from a neutron star collision or some other stellar event billions of years ago.

by kyle batra

The past couple weeks have been filled with news from Puerto Rico and Nevada so you might have missed the other important news of the week- the Nobel Prize. The Nobel Prize, named after Alfred Nobel who was famous for inventing dynamite, is a yearly award in many scientific categories and also peace and literature that honor the greatest achievements in those fields.

This year’s Nobel Prize in physics was awarded to three scientists, Kip Thorne, Rainer Weiss, and Barry Barish for their contributions in discovering gravitational waves, a concept that had been theorized by Einstein but never proven until very recently.

So what are these gravitational waves? Gravitational waves are very similar to other waves- light, radio waves, gamma rays… Yet they are a lot fainter and harder to detect (gravity is the weakest force compared to electromagnetic forces and the strong and weak nuclear force). Because of this, as Einstein theorized, we would only be able to detect massive gravitational ripples in spacetime, for example, when two black holes collide. Just a few weeks ago, just this occurred. Two black holes each about solar masses ended up merging far away in space, sending out huge ripples, gravitational waves, out in spacetime. We were able to detect these waves on earth, confirming that gravitational waves exist, which is a major discovery in physics and proves that Einstein was correct. This gives scientists a new way to observe the hardest observable object in the universe, black holes, and allows astronomers to look at other high mass objects like galaxies as stellar clusters as well.

In the photo above, one can see the large dip in spacetime that the supermassive black hole causes in spacetime. When multiple black hole’s collide, it causes the reverberations in spacetime which is what scientists look for and is what is known as gravitational waves.

How were the gravitational waves detected? Scientists constructed these two large-scale detectors named the LIGO interferometers which use a complicated set of angled mirrors to send two powerful lasers through miles of tubes. At the end, a detector is able to measure the exact wavelength of the laser, including where the bals and troughs are in the light wave. By looking at the variability between the two lasers, it can detect if a gravitational wave impacted the light waves. The tubes are very isolated so that nothing other than the gravitational waves could impact them. There has now been a third interferometer constructed in Italy, which was also able to confirm the previous detection of gravitational waves. By now having three detectors, astronomers can triangulate where in the sky the gravitational event is coming from. The final detector, named VIRGO, is smaller than the LIGO interferometers but is just as useful because of its ability to help triangulate the location of the event.