Stephen Hawking’s Final Theory: A New Path to the Multiverse
Just days before his passing in March 2018, legendary physicist Stephen Hawking left the world with one final gift a groundbreaking paper that reimagines how we might detect the existence of parallel universes. Co-authored with Belgian physicist Thomas Hertog, the paper titled “A Smooth Exit from Eternal Inflation” was published in the Journal of High Energy Physics and continues to spark deep conversations about the origins and structure of our cosmos.
For decades, Hawking challenged the boundaries of physics, reshaping how we understand black holes, the Big Bang, and the nature of time. His last work pushed those boundaries even further, aiming to transform the multiverse from a purely theoretical idea into something that might be observable and testable.
The Puzzle of Eternal Inflation
To understand Hawking’s final idea, we first need to look at a major concept in modern cosmology: eternal inflation. This theory suggests that right after the Big Bang, the universe expanded at a staggering rate far faster than the speed of light. In many versions of the theory, inflation doesn’t stop everywhere at once. Instead, it continues in some regions, creating endless “bubbles” of space-time.
Each of these bubbles could become its own universe, with its own laws of physics a vast multiverse. But there’s a big problem: this classic view of eternal inflation predicts an infinite number of universes. Infinity makes it nearly impossible to calculate probabilities or test the theory with observations, leaving scientists unsure how to move forward.
Hawking and Hertog’s New Approach
Hawking and Hertog set out to solve this. Their paper proposes a fresh mathematical framework that avoids the messy infinities of traditional eternal inflation. Instead of countless bubble universes forming randomly, their model predicts a finite number of universes that emerge from a smooth exit from inflation hence the paper’s title.
Their approach is based on string theory and the principles of holography, which suggest that the universe’s three-dimensional properties can be described by information on a two-dimensional surface. Using this, they rewrote the equations of eternal inflation in a way that makes the multiverse predictable and potentially observable.
Searching for Evidence in the Cosmic Microwave Background
One of the most exciting parts of Hawking and Hertog’s work is that it offers a testable prediction. They proposed that traces of other universes could leave subtle marks in the cosmic microwave background (CMB) the faint afterglow left behind by the Big Bang over 13.8 billion years ago.
By studying patterns in the CMB with future telescopes and space missions, scientists might detect signs that our universe is just one bubble among many. Such evidence would not only support the multiverse idea but also reshape our understanding of cosmic origins and the nature of reality itself.
Hawking’s Final Legacy
Thomas Hertog later described the project as deeply personal for Hawking. Even as his health declined, Hawking continued refining the ideas behind the paper, determined to leave behind a legacy that future scientists could build upon. Hertog recalled that Hawking “was not satisfied with the existing picture of eternal inflation” and wanted to make it more scientific and testable.
Though the paper doesn’t prove the multiverse exists, it represents a bold step forward turning a concept once thought beyond science into something we can study with real data. It’s a testament to Hawking’s lifelong mission: to understand the universe and share that understanding with the world.
A New Chapter in Cosmology
Today, research inspired by Hawking’s final paper continues. Scientists are exploring new ways to test multiverse theories using improved observations of the CMB, gravitational waves, and high-energy physics experiments. Whether or not we ever confirm the existence of other universes, Hawking’s work has already changed how we think about the cosmos.
His final message is clear: the universe — and perhaps the multiverse — is not beyond our reach. With creativity, persistence, and science, we may one day glimpse worlds beyond our own.
Stephen Hawking’s last scientific contribution, “A Smooth Exit from Eternal Inflation,” is more than a paper it’s an invitation. It challenges scientists to look deeper into the cosmic background for clues of other universes and to rethink the boundaries of what we consider possible. As we continue exploring the vastness of space, Hawking’s final idea reminds us that our universe might just be one chapter in a much larger story one still waiting to be discovered.