The Universe doesn’t care what I think
Professor Brian Schmidt of the Australian National University addressed an audience of more than 400 people at the Schwarzman Centre for the Humanities on 12 September, at the 2026 Green Templeton Astronomy for All Lecture.
Dr Steve Raj Prabu reports
How did the Universe begin, what is it made of, and how will it end? Nobel laureate Professor Brian Schmidt took on these questions in Green Templeton College’s Astronomy for All Lecture, guiding the audience through more than a century of discoveries about the Universe on the largest possible scales.
Schmidt began close to the beginning. Around 380,000 years after the Big Bang, the Universe was filled with hot matter and radiation. Light from this period can still be detected today as the cosmic microwave background. Within it are tiny ‘bumps and wiggles’ – the traces of enormous sound waves that travelled through the young Universe. These patterns have become one of astronomers’ most powerful tools for understanding what the Universe contains.
Our modern picture of the cosmos began to emerge just over a century ago. By studying nearby galaxies, Edwin Hubble found a striking relationship: the farther away a galaxy was, the faster it appeared to be moving away. The conclusion was that the Universe itself is expanding. If that expansion is mentally run backwards, galaxies become progressively closer together, ultimately pointing towards the hot, dense beginning astronomers call the Big Bang.
But the story becomes more complicated once gravity is included. Einstein’s theory of general relativity indicates that matter bends space and that gravity should affect the expansion of the Universe. Depending on how much matter the Universe contains, it could have followed very different histories—and might even have eventually stopped expanding and collapsed back on itself.
In the 1990s, Schmidt and his colleagues set out to measure how quickly cosmic expansion was slowing. They used Type Ia supernovae: exploding stars so bright that they can be seen billions of light years away. Finding them was painstaking. On an observing night, the team could take around 1,500 images while finding only a handful of useful supernovae. They used what Schmidt described as a rudimentary form of artificial intelligence to help sift through the data, alongside around twenty astronomers who manually searched for promising supernova candidates.
Then came the surprise. The measurements did not show the expected slowing. Instead, they indicated that the expansion of the Universe had sped up. Schmidt recalled that he had rather liked the idea of a Universe that would eventually collapse, giving it both a beginning and an end. The observations had other ideas. ‘The Universe,’ he concluded, ‘does not care about what I think. It does what it does.’
Professor Brian Schmidt and some of the Green Templeton astrophysics Research Associates, including Dr Steve Raj Prabu (right)
The discovery led to the idea that something is pushing the expansion of the Universe to accelerate. This is called dark energy, although its true nature remains unknown. Current measurements suggest that ordinary matter (everything from people and planets to stars) accounts for only about five per cent of the Universe.
Around twenty-five per cent is mysterious dark matter, while approximately seventy per cent is dark energy. Measurements of the ancient sound waves in the cosmic microwave background also indicate that, on the largest scales, the Universe is remarkably close to flat.
There are signs that this picture may still be incomplete. Schmidt highlighted the ‘Hubble tension’: two different ways of measuring the current expansion of the Universe disagree by about eight per cent. Whether this is caused by a problem with the measurements or points towards new physics remains unresolved.
Schmidt also addressed a more down-to-Earth question: why spend money studying the Universe? Astronomy, he argued, is part of humanity’s desire to understand the world, but fundamental science also produces unexpected practical benefits. Technologies connected with astronomy and physics have contributed to developments used in wireless communication, digital cameras and GPS. The difficulty of predicting what science will produce tomorrow, he argued, should not make society underestimate its importance today.
Finally, Schmidt looked towards the distant future. If dark energy continues to behave as it does today, the Universe will expand faster and faster. Eventually, distant galaxies will recede from us so rapidly that their light will never reach us. The visible Universe will gradually become darker and visibly emptier.
For the astronomers of that distant future, Schmidt joked, there may be an additional problem. With almost nothing left in the night sky to observe, they could find themselves ‘unemployed, with or without AI.’
Dr Steve Raj Prabu is Breakthrough Listen Fellow at the Department of Physics, and a Research Associate at Green Templeton College, University of Oxford.
