A brief history of A Brief History of Time

In 1988, Stephen Hawking released what was to be his seminal science book, A Brief History of Time. It has sold millions of copies in multiple languages. But many people admit to never making it past the first few pages, earning the book the accolade of being the most popular unread tome of all time. If you did the same, former Cambridge astrophysicist Dr Matt Middleton, who's now based at the University of Southampton, has a brief history of A Brief History of Time to bring you up to date...

I can’t possibly do the content, nor impact, of this famous book justice. “A Brief History of Time” was Professor Hawking’s way of placing the wonders of the cosmos within reach of everyone with a curious mind. It has helped shape and inspire a generation of eager scientists, and I count myself amongst their number. But, in any case, I’ll try and break his famous book down, by telling you about my favourite bits of the physics it explores. Here’s a very brief history of A Brief History of Time.

Stephen Hawking worked extensively on black holes – from the mindbending nature of singularities to the establishment of black hole thermodynamics, before we had any evidence they existed,, and now they’re a main-stay of observational astronomy - from hot gas clouds pulled apart by SUPER Massive Black Holes to smaller black holes stripping material from a companion star. More recently, LIGO confirmed their presence from the detection of gravitational waves as two spinning black holes collided and merged together. I’m sure Prof Hawking was also excited by the prospect that we might soon see a black hole for the first time. 

Telescopes all around the world lined up to create the biggest telescope ever - The Event Horizon Telescope. The path of the light near a black hole is bent by gravity resulting in a shadow that we can observe with this extremely high resolution instrument

This gravitational light bending-  the idea that the path of light can be affected by gravity, - is presented in a Brief History of Time. It is a direct consequence of General Relativity, which predicts that both the paths of light and matter are affected by massive objects. It is now used extensively in the discipline of ‘lensing’ where massive objects or collections of objects (such as clusters of galaxies) can bend light around them. When they intersect, they amplify light,  so we can detect and study very distant objects. This study of distant objects connects rather nicely to other themes in BHoT, notably the expansion of the Universe.

By looking at how light from distant galaxies is shifted compared to light you might see in a labratory, Edwin Hubble famously confirmed that galaxies were (almost exclusively) retreating from us – a notable exception is Andromeda which will collide with the Milky Way in a scant 4 billion years. The realisation that the Universe is expanding remains one of the most important in human history.

Extrapolating backwards inevitably results in a point in time where all the Universe’s mass was contained in an extremely small space - the explosion of space and time from which the Universe emerged was dubbed the ‘Big Bang’. Stephen Hawking worked extensively on this concept and naturally it features heavily in a Brief History of Time

When we look at the residual light and radiation from the big bang - known as the cosmic microwave background - the fluctuations are so extremely small in any direction that we look, we know that the universe was once incredibly compact, and expanded very very quickly. When I say quickly, we can work out it expanded in 100 millionth of a trillionth of a trillionth of a second, by a factor of 10⁵⁰, a number so large I don’t even have time to say it. 

In fact this ‘inflation’ was faster than the speed of light – but don’t panic, the expansion of the Universe doesn’t have to obey the speed of light. We think this inflation is down to something mysterious called vacuum energy (also called Dark energy or Quintessence).

One of the things I really love about A Brief History of Time is that it’s about more than just the science; it’s also a story of development and our place in this beautiful cosmos. Stephen Hawking presents a human perspective throughout, navigating our movement away from a Ptolemaic view of the Universe (where the earth was at the centre), through the Copernican revolution of a heliocentric solar system and to the point where we do not inhabit a special place in the Universe at all.

Whilst this may sound a tad bleak, we should take comfort in the fact that the Universe may have been just right for life to develop – referred to as the anthropic principle. If the the Universe wasn’t able to support life then we may not have the stars and galaxies, mankind may never have dragged itself from the primordial swamp and – most upsettingly of all – the Universe may have been denied minds such as Stephen Hawking’s and we may not have had a Brief History of Time at all...