Addressing a packed audience, Cox said he was excited to give the speech at the event.
“I asked the organiser if they needed me to talk about safety and security,” he said. “They said no… just talk about the universe.”
Cox said the scale and challenge of his job as a cosmologist was shown by ‘the fact our nearest galaxy is 23 million light years away’.
He said: ‘What I’m trying to say is the universe is big! The challenge is to see our position. We are physically insignificant.’
Quoting cosmologist Carl Sagan, Cox said astronomy was a ‘humbling experience’, and then also American author, John Updike, who said ‘astronomy is what we now have instead of theology: the terrors are less but the comforts are nil.’
Cox then took the packed audience on a whistle-stop tour of the theories of the universe, including Einstein’s theory of relativity, and how that grew out of his own thinking on gravity and light, which was from James Maxwell’s 1860s experiments on light and rainbows.
He said: ‘Really simple benchtop experiments motivated Einstein to his theory. Depending on your feeling about maths, the equations are either gibberish or beautiful.’
Einstein had ‘demolished the notion of absolute time’ – one of the key theories of physics – Cox said.
Cox said it was an ‘audacious leap’ from ‘just some electricity and magnetism experiments’ that led to a theory of the creation of the universe.
He then went onto explain how when you look further back in space, you can see everything is so hot that atoms can’t form.
‘Can I see the Big Bang? The answer is yes, almost.’ He said.
‘Seeing the oldest light in the universe, there are no stars and galaxies, it is just the glowing plasma of the young universe with dense dots of light.
‘The different colours correspond to slightly different densities. This picture shows that the universe was very dense and very hot and that the universe is not eternal.’
He said that one physicist had described the dense spots ‘like looking at the face of god’ as they collapsed to form the first stars and galaxies.
When you put the image of the oldest light into a computer and simulate the expansion of the universe, the distribution of galaxies creates the cosmic web that we have today, he said.
Speaking about what existed before the Big Bang, Cox said ‘Inflation is the best theory’, and which only became a mature concept in the 2000s.
He said: ‘There is a little patch of space before big bang. The universe was still there, but it was empty and cold, and has a ‘kind of stuff’ but if you put it into the universe it makes it stretch very fast.
‘This theory starts with something a billionth of the size of the nucleus of an atom. Ten to the minus 37 seconds stretching out. It doubles 100 times and possibly many more times, until it stops, and when it stops the entire observable universe is the size of the exhibition hall.
‘And all the energy is dumped into the space, and it heats it up and it makes particles and it creates the Big Bang.
‘That’s the cause of the big bang itself.’
Cox also said there was a prediction that if you look into the data map of the universe, you should see circles in the sky that are a direct prediction from the oldest light.
Astronomers should be able to draw these circles through the distance between galaxies, by pairing galaxies up through a correlation function.
He said: ‘The graph was only published three years ago – it is true that it more likely to find these predictions than not.
‘This is cutting edge cosmology – we have been able to probe the origin of our universe from the billionth the size of an atom to today’s trillions of galaxies through data.’
Cox also took a number of questions from the floor, including why we haven’t found any other intelligent life in the universe.
He said: ‘Biologists point to the history of life on earth. Complex life doesn’t begin for 3.5 billion years, until then it is only single celled.
‘The evolutionary events are extremely fortuitous. Someone one cell got inside another one and survived and then reproduced.
‘It is ‘mind-boggling’ how rare it is but it did happen – and it happened here.’
‘One biologist told me, when looking at at my map of the Milky Way “you should say out there, there is only slime.”’