Why does the Universe expand the way it does? Why does it accelerate? Einstein’s equations offer an explanation of gravity that works on the scale we know, but do they work on the grandest scales of space and time? Humanity now has a way to find out. The General Theory of Relativity predicts the behaviour of gravity, and includes a term known as the cosmological constant. Einstein added this term to make the universe static and unchanging, as he believed it was. But when the expansion of the universe was discovered by Edwin Hubble, Einstein regarded it as ‘the greatest blunder...
Today, the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) is expected to announce a monumental discovery that is 100 years in the making. Theorized by Einstein’s general relativity in 1915, gravitational waves are ripples in space-time, similar to sound waves, but much tinier. The search has been ongoing for decades, with no results. Until now. LIGO has the most sensitive gravitational wave detector ever conceived – in two interferometer facilities in Livingston, Louisiana and Hanford, Washington. They use a laser split along two axes to give an in-phase beam. If gravitational waves along one of the axes affect the beam, it...
When Isaac Newton quantified gravity, his theory explained how everything in the world around us behaved in its presence. It opened a door to an understanding of something fundamental, yet elusive in explanation. Centuries later, Einstein came along and took a step back, finding a larger more comprehensive theory of gravity, one that explained the strange things that happen in the grand universe. His theory could even explain things that Newton’s theory of gravity could not, such as the odd orbit of Mercury around the Sun. But the greatest part of Einstein’s theory is that if you use it to...
Predicting the death of a star is easy. If we know how massive it is, and what stage of life it’s in, we know that it should explode eventually, within a set timeframe of many hundreds of thousands, or even millions of years. But on human timescales, that is just not good enough. What if we could predict a supernova explosion within a few months? For something that lives for so long, this would be a triumph in our understanding of the universe. Over the past couple of years, this is exactly what happened. Here’s how. A supernova is one of the most...
The biggest problem in theoretical physics today is the marriage between Quantum Mechanics and Gravity. Throw in the fact that whatever theory comes out of it has to additionally be able to explain Dark Matter and Dark Energy, and we have ourselves a massive problem to solve. How do we reconcile the seemingly random probabilistic nature of quantum mechanics with the smooth, pliable space-time of General Relativity. We have two incredible theories that explain the Universe, make predictions accurately, and have led to amazing advances in technology and understanding, yet they completely disagree with each other at common scales. So...
