Video: How much do we understand about the universe?

In this video for the World Economic Forum, Nobel Laureate in astrophysics Brian Schmidt and cosmologist Lawrence Krauss turn metaphysics into physics, as they search the stars for the Holy Grail of the Big Bang.

Watch the full presentation in the video above, or read key quotes.

On an expanding universe

“In 1929, Edward Hubble discovered that the universe was expanding. It’s also what Einstein’s theory of relativity predicted. If Einstein had the courage of his convictions, he would have predicted this because his theory depended on it. It changed everything. In science the conventional wisdom was the universe was static and eternal. Then if things are expanding, it must have had a beginning.”

“If the universe is 13.8 billion years old, you’d think if we could see far enough we’d be able to see back to the Big Bang. But if I can’t ever see or know this stuff exists, is it really there? Are we at the limits of empirical science when it comes to understanding the universe? We look back in time. The universe is getting smaller and smaller, but it’s speeding up in its expansion.”

“Galaxies are getting younger and younger as we look back in time. Eventually we get to a time when there are no galaxies and no stars. The universe is a very boring place. And we think that’s about 400 years after the Big Bang, but we don’t know. This is one of the things that the James Webb Space Telescope is going to help tell us. There’s a period of Dark Ages, the universe is still expanding during this time. It’s becoming denser and denser as we look back in time, eventually becoming so dense and so hot that we have this wall.”

On a universe smaller than the size of an atom

“This is one of my favourite images. It’s called the Oroborus. It goes back in many cultures, at least 4,000 years and it’s a snake eating its own tale. And this really represents the universe. Because the universe is expanding. It was much smaller. In fact before the period of inflation, our visible universe was actually smaller than the size of a single atom. It’s hard to imagine. All that matter, of 100 billion galaxies, each containing 100 billion stars was contained in a region smaller than the size of an atom. It’s amazing we can talk about that with a straight face.”

“But that means if we want to understand the macroscopic properties of our universe, we want to understand physics on very small scales, not very large scales. And that’s why I, as a particle physicist, got into cosmology, because the way to test the universe on the larger scales is to try and probe matter on the very smaller scales. So one of the ways we can try to probe those very early times in the history of the universe, is not to look out with telescopes.”

“This is the large Hadron Collider at Cern. Underground is the most complicated machine humans have ever built. A 26 kilometre long tunnel that accelerates protons in one direction at 99.99999% of the speed of light and when they collide the energies are such, that they locally produce conditions that are reminiscent of the conditions of the very early universe. So if we want to create conditions that can tell us what the very early universe was like, we need to build large accelerators.”

On the probability of other universes

“If we can probe the physics of inflation, one of the predictions of that physics is that the most of space is still expanding very fast. Our universe was like a seed that decoupled from that background space that was expanding, but there should be many other universes, some of which are just being born now. If we can test the physics of inflation, we’ll turn this metaphysics into physics. We’ll be able to probe the theory, and even though we won’t be able to see those other universes, we’ll be able to make predictions of our universe based on that theory.”

“Just like when Einstein was developing his theory of relativity, we didn’t know that we’d be able to see atoms, but everyone knew that atoms existed because of the indirect evidence. So this will be an amazing result if it’s true, because we’ll be able to probe the metaverse, not just our single universe. So how many stars are out there? A lot, and you can imagine. You’ve got 260 billion galaxies in the visible universe. Each one of those has 100 billion stars. So that gives us a lot of stars. People like to ask me is there life out there? I don’t know. But there’s a lot of chances for it.”

Watch the full video in the player above.

Author: Lawrence Krauss is an American theoretical physicist and cosmologist. Brian Schimdt is a Nobel Laureate in astrophysics and distinguished professor at the Australian National University.

Image: A composite of separate exposures taken in 2003 to 2012 with Hubble’s Advanced Camera. REUTERS/HUDF/NASA.