Last updated December 4, 2019 at 4:58 pm
Retrieving Infinity Stones, parallel universes, and the quantum fundamentals of the universe keeps Sean Carroll on his toes before his Australian tour next year.
When The Avengers needed to time travel, they called Sean Carroll to teach them how. Credit: Marvel Studios
Why This Matters: Understanding the biggest questions of our universe is part of our inherent human curiosity.
With the universe decimated and Infinity Stones destroyed, The Avengers concoct a plan to go back in time and steal the infinity stones from various points in history. However, doing so would create parallel universes at each point in time – universes where the infinity stones no longer existed.
While we know science fiction sometimes takes some liberties, parallel universes and the concept of many worlds is firmly rooted in scientific theory, says Avengers: Endgame scientific advisor Professor Sean Carroll.
“The many worlds of quantum mechanics is a very simple idea that we think is true in the real world. This is not crazy science fiction,” Carroll says.
“We think that every time you observe a quantum mechanical system like an electron or something like that, there’s different measurement outcomes that you could get. What actually happens is that many different versions of reality are created, and in each one a version of you got a version of the different measurement outcomes.”
Many worlds under test
A theoretical physicist at the California Institute of Technology, Sean’s work away from the Marvel realm focusses on quantum mechanics, cosmology and the nature of gravity.
“There are experiments going on right now to try to falsify this theory. If we ever see any quantum system behaving in a way that is not described by the Schrodinger Equation (an equation that is key to quantum mechanics), then we know that many worlds is not right.”
“Ultimately what matters are the equations.”
But don’t go expecting to see or visit these alternate universes.
“They’re not located anywhere. There’s no such thing as ‘where the other universes are located’ because the universes don’t exist within space. Space exists within each universe.
“So the universes are parallel and simultaneously existing, but they’re not located somewhere.”
In the end, the stones are returned to the exact moment they were taken, removing the possibility of parallel universes. And that, says Carroll, is entirely logical and internally consistent. (Interestingly, Bruce Banner promised that would occur before he knew it would be possible within the storyline).
Deeper: Avengers: Endgame science review – *that* bit explained
Would Professor Hulk cut the mustard?
So would Professor Hulk get a gig in a real-life university’s physics department?
“Any one of the scientists in the Marvel Universe would be an academic superstar. They seem to pick up entire new fields overnight,” Carroll laughs.
One thing that might count against Prof Hulk is his theories around travelling back in time, which Carroll isn’t so sure about.
“Travelling forward in time is no problem – everyone does it literally all the time. But travelling backwards, I’ll be honest, I think that it’s not possible.
“But we don’t know for sure.”
“When Einstein comes along and says space and time are curved, then you can begin imagining curving spacetime so much you can get in your rocketship, zoom out on a curved trajectory and end up before you left.
“However, when we try to create such warpings of spacetime mathematically, it seems that everything just collapses into a black hole.
“It seems we can’t actually pull it off. It seems to be an indication the universe is saying that time travel is just a no-no.”
Damn.
Getting science into the Marvel Universe
Although Sean feels like he was a tiny cog in the mammoth Marvel machine, his involvement with Endgame began very early during production.
“I would go in for an afternoon at a time during the script development phase and talk to the writers and directors. They’d tell me some of their problems, and I’d give them some suggested solutions.
“They already had the idea of time travel when I talked to them. But they didn’t know what to do about multiple universes and parallel realities and things like that. I helped them with that, and I helped clear up some of the bad ideas about time travel.”
“Now they might say ‘well that doesn’t work because of this’ and I’ll try something different, and eventually we’ll converge on something.”
And while different filmmakers have different approaches to working with scientific advisors, the Endgame team led by the Russo brothers were very open to his input.
“There’s a line in the movie where Paul Rudd says ‘so you’re saying Back to the Future is bullshit’, and that line basically came out of our conversations – because that’s definitely my opinion.”
Science fiction doesn’t need to be science fact
However, he says science fiction doesn’t necessarily need to stick to what we know to be possible.
“Science fiction has a responsibility to make sense. It needs to tell a story that is logical and coherent and compelling.”
They are, after all, works of imagination. And while there are a lot of things that we think we do know about the universe, they might only be approximately true, says Carroll.
Deeper: The Science of Fiction
“We don’t know the final laws of physics, maybe we’ll learn something someday.
“The role of science fiction is to explore different possibilities.”
And if those possibilities excite and interest people, that’s hugely important, he adds.
“I think they did a great job with Endgame.”
Sean will be touring Australia in February 2020. His Our Preposterous Universe events will tackle the many worlds theory, and its basis in quantum mechanics, and the fundamentals of our existence. And while he accepts that his work might not result in technological innovations, for him it’s the very nature of human curiosity that leads to seeking answers to the bigger questions of the universe.
Sean will be hitting Brisbane, Sydney and Melbourne, with tickets available from Think Inc. If you can’t wait until then, his latest book Something Deeply Hidden: Quantum Worlds and the Emergence of Spacetime is in shops now.
