Understanding the science behind the universe’s mysterious phenomena has always been a popular topic, connecting diverse branches of physics. From understanding its contents through studying the universe’s structure, to how it was formed. Yet gravity, even though a fundamental concept of nature, has not been fully understood and still presents us with unexplored mysteries.
Described as a force by Newton, it is now described somewhat abstractly by Einstein in his theory of General Relativity, as the bending of a spacetime fabric due to the presence of masses, such as planets and stars.
This was a revolutionary discovery, for example in the discovery of gravitational waves and its technological applications (most notably the GPS). Observations have continuously proved the validity of the general theory of relativity.
Yet, no theory is perfect. As human technology becomes more advanced, precise astrophysical and cosmological data slowly shed light on the issues of Einstein’s theory.
No one yet truly knows how gravity works at the smallest scales, that is, how gravity works with quantum mechanics. This is crucial to understand what happened in the first few moments after the Big Bang where the universe’s size was extremely small.
At the other extreme, General Relativity does not completely work at the largest scales either. Observations have repeatedly shown that the universe is expanding at an accelerating rate. General Relativity cannot entirely explain the cause for this accelerated expansion unless dark energy is introduced.
We don’t yet know where dark energy is coming from, or if it is a new particle or a byproduct of gravity, beyond what Einstein originally envisaged. Scientists have been actively researching on both fronts of the matter and, whatever the result may be, it will definitely be revolutionary.
Modifications are necessary to the general theory of relativity in order to unify gravity with the remaining forces of nature. Einstein himself considered this avenue, in attempts of unifying gravity and electromagnetism, albeit without success.
To better understand gravity, modifications to general relativity and other theories such as string theory and teleparallel gravity were introduced.
Over the last few years, Malta’s contributions to this global effort have been growing significantly and have made a significant impact in this topic.
The coming few years will be very interesting with possible discoveries that even our tiny island may be part of.
Gabriel Farrugia is a teacher, lecturer and researcher.
Sound Bites
• GPS requires the physics of both Special and General Relativity. Special Relativity describes how fast-moving clocks tick slower than stationary ones. GPS satellites’ clocks tick about seven microseconds slower than those on Earth. For the GPS receivers, clocks tick about 45 microseconds faster due to effects of gravity. Overall, the satellite’s clock will tick 38 microseconds faster. If this difference is not accounted for, the GPS location will end up with an error of about 10 km per day.
https://physicscentral.com/explore/writers/will.cfm
• The discovery of gravitational waves has opened the possibility for scientists to learn more about the very early universe. Current observatories can look back to when the universe was 400,000 years old, by observing the first light seen in the Cosmic Microwave Background. Before this time, the universe was opaque, requiring observations from alternative sources. Detection of the primordial gravitational waves would provide great insight about the properties of the early universe.
https://www.ligo.org/science/GW-Stochastic.php
https://news.mit.edu/2020/universe-first-gravitational-waves-1209
For more science news, listen to Radio Mocha on www.fb.com/RadioMochaMalta/
DID YOU KNOW?
• Neutron stars are very heavy compact objects formed after the death of a massive star due to gravitational pressure.
• Spaghettification – when objects fall into a black hole, they are pulled in and stretched until they form a very long thin strand of atoms, as if they form spaghetti.
• Supermassive black holes are the heaviest type of black holes and are expected to be found in the centre of large galaxies.
• Observations on distant supernovae showed that these objects were moving away from each other at an accelerating rate.
For more trivia see: www.um.edu.mt/think