The limits of noise

Of the astronomical phenomena, we can witness with our own eyes, a solar eclipse is one of the most spectacular. This phenomenon was used early in the 20th century to prove Einstein’s new theory of gravity. As light passes around a celestial object, its path is bent exactly as predicted by Einstein’s theory.

When researchers compared the amount light that was bent by large clusters of galaxies with the observed mass of the galaxies, they found that there was a discrepancy of over a factor of 1000, giving birth to the phenomenon known today as dark matter.

Deandra Cutajar

The distortions of galaxy shapes by large masses, provide astronomers with a tool to construct a dark matter map and its distribution in the universe we observe. Images captured using telescopes are analysed carefully to understand the distortions of galaxies due to the presence of dark matter lenses. However, in practice this is a very arduous task because telescopes suffer both from electronic noise as well as atmospheric distortions, so throughout my PhD, I investigated how the noise present in astronomical images could contribute to the distortion of galaxy images and also introduce errors in our maps of dark.

Under the supervision of Prof Kristian Zarb Adami, I applied Bayesian inference to determine the correct measurements of galaxy shapes. However, since the variations in the shape and size of galaxies due to lensing is very small, the measurement of dark matter is extremely difficult. Only novel statistical methods developed within a consistent Bayesian framework allow us to extract the maximum amount of information in such difficult scenarios.

Unfortunately, the application of the new methods in my Ph.D. have shown results that are similar to those reported by other researchers, with the techniques failing to provide the desired accuracy. Nonetheless research goes on, unravelling more mysteries and questions that still need answers.

 

Understanding gravity to understand the universe

For a primate species clinging to a speck of dust in an incomprehensibly vast universe, curiosity has seen humans discover a great deal about how it all works. However, there are still mysteries that the cosmos is reluctant to relinquish, one of which is gravity. The most accurate theory describing gravitational attraction is general relativity, developed by Albert Einstein in 1915. Unlike Isaac Newton, Einstein did not describe gravity as a force, but rather a manifestation of the curvature of spacetime, thought of as a stretchable and squeezable fabric that is distorted by matter. However, his theory does not fully explain phenomena such as the accelerating expansion of the Universe and inconsistent orbital speeds of stars within galaxies.

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Extreme stars unlock gravitational secrets

Our understanding of gravity has changed over the years and will likely continue to as researchers arm themselves with new ideas tested by increasingly sophisticated technology. Dr Jackson Levi Said, Mark Pace, and Filippos Nachmias (University of Malta [UoM]) tell THINK more about their mission to unlock gravity’s secrets from neutron stars.

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Galactic rotation dynamics in modified gravity

In the last 100 years, Einstein’s theory of general relativity has proven invaluable to explain the nature of the universe. That being said, Einstein’s model of gravity does at times fail to comply with what we actually observe when looking up at the night sky.

Galaxies offer one of the most impressive laboratories where general relativity just does not work. Stellar objects in galaxies tend to orbit the galactic centre of mass. General relativity predicts that as one goes further from the centre of the galaxy, these orbital speeds drop off. Observational data shows that these velocities tend to stay constant along the radius of a galaxy. However, dark matter can be artificially introduced to account for this. The other argument is that such failures indicate the inability of general relativity to fully explain how the universe works. If this is so, it seems necessary to construct what are called alternative or modified theories of gravity. Such theories would have to be capable of correctly explaining all observed phenomena including those that general relativity fails to produce.

Andrew Finch (supervised by Dr Jackson Levi Said) is looking into the new concept of treating gravity as a torsional dominated system instead of a curvature dominated one, which is the concept explained by general relativity. The new models are being developed with the intention of agreeing with galactic rotation curves while managing to explain everything that general relativity already does. It is only possible to vigorously test such models because of the large amount of freely available data which has been gathered on galaxies. As models are obtained, the cluster in the ISSA (Institute of Space Science and Astronomy) laboratory is being used in order to determine model parameters. Using this data, Finch aims to compare Einstein’s theory with the new model being developed. Will it improve on Einstein’s ideas? Only Finch will tell…

This research is being performed as part of a Masters Degree in Astrophysics being read at the Institute of Space Sciences and Astronomy, University of Malta.

Andrew Finch

Is Time Travel possible?

Theory says yes; practicality says no. Thanks to Einstein time travel is possible. The easiest way is travelling very close to the speed of light. Achieve 99.5% close to light speed means that in 5 years you travel 50 years. Goodbye friends and family you left behind. The harder way is creating a wormhole, a device that can bend space and time, looping it on itself to go into the future or past. The energy required would rival the energy of the stars. Sorry Sci-Fi fans.

Did Albert Einstein say we only use 10% of our brain?

Probably not.Brain2 It has been misattributed to Einstein to explain his great intelligence. The idea being that if only we used more, we would unlock the powers of our mind, become mathematical geniuses, perhaps even become telekinetic. Unfortunately, even when we think we are being lazy, like sleeping, our minds are quite busy.

Is all hope lost? Are we stuck with the intelligence we have? Probably a good education does not hurt and cognitive scientists have identified two methods that can push our brains further. The first involves focus. By concentrating on a single task, you can use more of your brain and tackle those complex mathematical formulae. The brain is usually very distracted.

The second strategy is optimisation. It involves letting your brain find the optimal solution by stopping to think and considering many alternatives before jumping on one answer.

Creativity can use a totally different ball game. Sometimes it is best to let your brain wander and simply consider all alternatives. Our brain is too complex for a few basic strategies to apply to all situations.