At talk on Gravitational Waves by Natasha Carr


One of our younger members, Natasha Carr, has recently completed a four month project to learn about gravitational waves.

She delivered an excellent talk on this subject at the observatory on the 10th August 2018.

So what are gravity waves and why do we care about them?

When two massive objects – typically black holes – of different masses merge, the event causes waves not just in space but in time too. The distance of one metre varies by a tiny, tiny fraction when gravity waves pass through the space being measured. Pretty weird huh?

That quite clever chap Mr Einstein (IQ estimated at 170 – 190 based upon an analysis of his work) predicted gravitational waves over 100 years ago. In 1974 they were observed for the first time. But technology wasn’t advanced enough for us to properly detect and measure them back then and it took another 40 years and one of the most sensitive devices in the world to see them.

Two identical devices and a special telescope have all detected gravitational waves. The first two devices are the essence of LIGO (not to be confused with Lego), and are astonishing laser devices that send light 2km in two directions at a 90 degree angle. The light is split by a special prism and when the light returns to the laser, it is recombined. If there is a variation in luminosity between the light that leaves the laser and that which returns, then gravitational waves may have been detected.

Before it can be confirmed, NASA has to check with many sources around the world to make sure there have been no big storms or other events that might have created vibrations at LIGO. The device is so sensitive that it can detect footsteps as people walk past it. When LIGO was built, they even had to take the Moon’s gravity into account to make sure it didn’t affect the lasers. LIGO has two identical lasers in different parts of the US to check and confirm results.

Natasha gave us a great overview of the search for Gravitational waves and where we are before moving on to look at the future. And that’s where we find LISA. LISA is a massive detector that will sit far away from earth in space and instead of comprising two laser beams, it will be a large triangle with a laser beam on each edge. I have no doubt this will revolutionise our understanding of gravitational waves and take a big step further on our journey towards a unified theory of everything. However, before LISA can be built, funding has to be found and there’s not much cash about for this type of project at the moment. Cough up, Trump!

In finishing her talk, it was the unified theory that Natasha focused on. It is the Holy Grail of science – a complete theory that slots together all the individual aspects that have been described by various people from Euclid to Galileo, from Newton to Einstein and from Planck to Hawking with a whole host of people in between. If we could knit all these theories and ideas together, we would have a unified and complete view of the universe with a set of coherent rules that explains everything that happens.

As you read this, you might still be wondering why we are looking at gravitational waves and that’s a very reasonable thought to have. So here’s why it matters:

  • Anything that proves aspects of Einstein’s Theory of Relativity is very special because it elevates his work and helps to confirm our understanding of the universe
  • The detection and measurement of gravity waves will create other discoveries; unintentional consequences that will improve our appreciation of physics and some of the elusive aspects of the universe like dark matter, dark energy and dark ear wax
  • As for people and society, the instruments necessary for gravitational wave detection required new technologies that are now being used in the manufacturing industry. This is not unique to LIGO – many technologies developed for space exploration have found their way into everyday life albeit in a modified form. In this aspect alone, space exploration is invaluable and its huge contribution to society is impossible to overestimate.

Natasha provided a fascinating talk on a subject that is clearly close to her heart. Her explanations of the aspects we looked at and her expert handling of all the questions she was asked is a credit to her.

I hope Natasha will come back to give another talk on this subject sometime in the future to update us on progress and I wish her every success with her studies.

NB LIGO stands for Laser Interferometer Gravitational-wave Observatory and LISA stands for Laser Interferometer Space Antenna. You can learn more about these projects and see LIGO detection results on NASA’s website.