PBS Space Time Season 2018 Episode 14 Using Stars to See Gravitational Waves

Using Stars to See Gravitational Waves is the fourteenth episode of the 2018 season of PBS Space Time. In this episode, the host Matt discusses how astronomers use distant stars to detect the ripples in the fabric of spacetime known as gravitational waves.

The episode begins by introducing the concept of gravitational waves, which were first predicted by Albert Einstein's theory of general relativity. Gravitational waves are caused by large masses accelerating, such as when two black holes merge or when a supernova explodes. These ripples in spacetime travel through the universe at the speed of light, distorting the positions of objects in their path by a minuscule fraction.

In order to detect these tiny distortions, scientists use a technique called gravitational microlensing. This technique requires the alignment of a distant star, a foreground star, and an observer on Earth. When a massive object, such as a black hole, passes between the distant star and the observer, it causes the light from the distant star to bend around the massive object. This bending of light creates a vision of the distant star in multiple places in the sky, creating a brightening effect that can last from a few hours to a couple of days.

By studying these microlensing events, astronomers can determine the characteristics of the massive objects that caused them. In particular, they can detect the presence of black holes and determine their masses. When two black holes merge, they create a burst of gravitational waves that travel through the universe, producing a characteristic pattern of brightening and dimming in the microlensed star.

The episode then shifts to a discussion of the latest developments in gravitational wave detection technology. In particular, the Laser Interferometer Gravitational-Wave Observatory (LIGO), which made the first direct detection of gravitational waves in 2015, and the Virgo detector, located in Italy, work together to detect these ripples in spacetime.

The detectors work by using lasers to measure tiny changes in the lengths of two arms, each of which is several kilometers long. When a gravitational wave passes through the detectors, it causes a tiny change in the lengths of the arms, which is detected by the lasers. By analyzing the frequency and amplitude of these waves, scientists can determine the characteristics of the objects that caused them, such as their masses and spins.

Finally, the episode explores the future of gravitational wave detection. With new detectors being constructed around the world, such as the KAGRA detector in Japan and the LIGO-India detector, scientists hope to detect even more gravitational waves in the coming years. These detections could provide valuable insights into the nature of gravity and the universe itself, including the possibility of detecting the elusive dark matter particles.

Overall, Using Stars to See Gravitational Waves is an informative and engaging episode of PBS Space Time that explains complex concepts in a clear and accessible manner. The episode demonstrates how astronomers use distant stars as cosmic telescopes to detect the subtle distortions in spacetime that reveal the presence of massive objects such as black holes. The show also highlights the latest developments and future prospects for gravitational wave detection, demonstrating the ongoing efforts of scientists to unravel the mysteries of the universe.