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Dark energy discovery changed understanding of universe: Nobel laureate
The US-born Australian astronomer along with Adam Riess and Saul Perlmutter from the US discovered the stuff, later termed dark energy, in 1998. The three won the Nobel Prize for Physics in 2011.
Explaining the significance of their discovery that changed the understanding of how the universe functions, Schmidt told PTI, "Dark energy is really saying (that) there is energy tied to space itself.
If we didn't have dark energy, the universe would be curved and the universe wouldn't accelerate -- and that changes how cosmic objects, such as galaxies, looks. It really makes a difference," the astronomer, who was visiting Ashoka University for the Lodha Genius Programme, added.
The term dark energy is intentionally similar to dark matter.
Dark matter refers to particles in the universe that hold galaxies and other structures in space (the cosmos) together. It is said to have peculiar properties, such as being invisible, as it does not interact with light.
However, while "dark matter and atoms (that make up ordinary matter) are pulling the universe, dark energy is pushing the universe. There's a balance at any given time of who's winning the war -- dark energy has won the war, it seems now and is pushing the universe apart", Schmidt explained.
That's because dark energy had a density set at the time of the Big Bang, said the 58-year-old former president of the Australian National University and currently a distinguished professor of astronomy.
The Big Bang, believed to have given birth to the universe, happened some 13.8 billion years ago. Dark matter is among the particles formed immediately after the event, gravity exerted from which is said to produce a slowing effect on the universe's evolution.
"And (dark energy) stayed at that density. But as the universe expanded, and the density of atoms and dark matter dropped over time, the two crossed about 6.5 billion years back -- and that crossing meant the dark energy could take over and accelerate the universe," Schmidt said.
Work on the discovery that the universe is expanding at an accelerating rate and that dark energy is the driving force began in 1994.
Schmidt and colleagues intended to look at distant objects and measure how fast the universe was expanding in the past, and then look at nearer objects to see how it slowed down over time.
"And if we measured the universe slowing down really quickly, then we'd know that the universe was heavy and you're gonna get a Gnab Gib -- the Big Bang in reverse. But if the universe was slowing down slowly, then we'd know the universe is light and it's gonna exist forever. So that's what we were going to do." Three and a half years later came the answer.
What we saw was the universe was expanding slower in the past and it sped up. So instead of slowing down, it's actually the other way -- it's speeding up," the Nobel laureate said.
In 1917, physicist Albert Einstein first imagined dark energy as a concept -- only he did not think of it in those exact words but instead accounted for it in his equations of general relativity as a 'lambda' term.
Einstein is said to have considered the lambda term irrelevant, even denouncing it as his greatest blunder.
"When we made our discovery of the acceleration (of the universe), it was the only sensible way of making it happen. So that thing (the lambda term), that he (Einstein) brought in 1917 and then later discarded as being irrelevant, that seems to (be validated from) what we discovered," Schmidt continued.
"In 1998, cosmology was shaken at its foundations as two research teams presented their findings...," states the press release dated October 4, 2011, announcing the recipients for the Nobel Prize in Physics for 2011.
The 1998 model has since been scrutinised through experiments, mainly aimed at understanding the nature of dark energy -- is it constant or does it vary? "We put in some extra knobs in the model of 1998, where we allow dark energy to change over time. The models with the most recent data seem to prefer a dark energy that changes," Schmidt said.
But he is sceptical.
"I'm not saying they're wrong. I'm saying I need better data to be convinced they're right. He said he is also glad that someone else is working on it.
Schmidt leads the 'SkyMapper Telescope Project' for which he conducted a survey of the southern sky as seen from Australia, focussed on looking at the "oldest, first stars in the galaxy".
"We could see essentially what the chemistry of the universe was back really close to the Big Bang -- because if a star was formed right after the Big Bang, it's made up of the stuff that was in the universe at the time.
"And so, we found the most chemically pure stars that have ever been discovered, ones that were almost certainly not formed from the remnants of the Big Bang, but from a single exploding star after the Big Bang. That just gives us a sense of what the first stars look like," said Schmidt, who has published his findings in several journals, including Nature.
Schmidt, who addressed high schoolers and others on science as a potential career at the university, advised them to get the skills that seem useful for life by working on something that interests them.
Not knowing what to do in life and the fact that he enjoyed astronomy made Schmidt pursue the field.
"In learning astronomy, I'd learned math, I'd learned physics, I'd learned computing, I'd learned some engineering. And (while) I didn't think it was likely that I would get a job to be an astronomer, I knew math, engineering, physics, and computing liable to give me a good job doing something. And of course, I did end up being an astronomer," he said.
"You don't really know how all of this is going to come together in your life, but if you work on something you're interested in, with a set of skills that seem useful for life, then don't overthink your life, don't overplan your life," Schmidt said.
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Indian Express
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Hindustan Times
9 hours ago
- Hindustan Times
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Ahmedabad: The researchers at the Indian Institute of Technology (IIT) Gandhinagar have found that flood protection measures create inequality by protecting some neighborhoods while leaving others with worse flooding. The team developed tools to assess how protective infrastructure redistributes flood damage and deepens inequality in cities. Flooding is among the most devastating of natural hazards, causing around US$41.1 billion in annual economic losses and affecting 74.6 million people worldwide between 2003 and 2022. (AP Tolang) The study titled 'Partial flood defenses shift risks and amplify inequality in a core–periphery city' and published in leading journal Nature Cities on August 15, examines how levees and embankments affect flood risk across city parts. Flooding is among the most devastating of natural hazards, causing around US$41.1 billion in annual economic losses and affecting 74.6 million people worldwide between 2003 and 2022. These impacts are expected to increase further as populations expand into floodplains, economic activities intensify and climate change drives more extreme flood events, as per the study. Using Surat as a case-study, the researchers showed how partial flood defences shift risk toward vulnerable communities, raising questions about urban planning and equity. 'Adaptation must consider who is protected and who remains exposed, not just total risk reduction. Flood resilience is about ethics, not just about engineering. If our solutions protect some but leave others worse off, we haven't solved the problem; we've just reshaped it. This study shows that we can do better, and now we know how,' said Udit Bhatia, Associate Professor at IITGN's Department of Civil Engineering and the principal investigator of the study. Cities worldwide use partial embankment systems and levees against flooding, from Spain to India, the study stated while noting that these structures hold back water and shield urban cores but redirect waters to city edges and informal settlements. 'In many cities of the Global South, peripheral areas house informal settlements, agricultural workers, and artisanal communities with limited access to infrastructure or disaster support,' said Bhatia. The study uses Surat as a case study to generate what-if scenarios, a city on Gujarat's Tapi River that has suffered repeated floods, including a major one in 2006. The researchers used a hydrodynamic model built with river records, city data, and 49 years of Ukai Reservoir discharges to simulate a 100-year flood with and without partial levees. They combined this with land-use damage estimates updated to 2022 replacement costs and ward-level demographic data to assess how losses change. The results showed that partial levees reduced damages by ₹31.24 billion (US$380 million) in the city's urban wards and ₹10.34 billion (US$125 million) in surrounding villages. At the same time, damages became more uneven. The researchers measured this using the Gini index, which ranges from 0 (losses evenly spread) to 1 (losses concentrated in one place). In Surat, the Gini for flood damages increased from 0.55 to 0.66 after levees, and the Gini for population exposure rose from 0.31 to 0.39, meaning fewer neighborhoods bore a greater share of the impact. Ashish S. Kumar, the lead author and a PhD scholar in IITGN's Department of Civil Engineering, said their approach looked beyond standard flood maps. 'City planners need to know where water goes, how fast it arrives, how long it stays, and which communities are hit hardest,' he explained. The analysis showed that neighborhoods close to the river gained up to 12 extra hours before flooding, while some downstream areas flooded up to seven hours earlier. Of Surat's 284 neighborhoods, 119 experienced deeper floods and 134 saw less. In exposed areas, floodwaters rose by up to 2.38 meters, while protected areas saw water levels drop by as much as 10.13 meters. 'While core areas remained dry longer, downstream and peripheral wards, which are often less affluent and less protected, flooded earlier and more severely,' said Kumar, who is also the recipient of the Prime Minister Research Fellowship. Flood volumes declined overall, with reductions of 28.51 million cubic meters in the city and 37.42 million in the suburbs. Expected annual savings were estimated at ₹2.02 billion in the core city and ₹1.44 billion in suburbs. But some downstream neighborhoods could still face additional damages of up to ₹600 million (US$7.3 million) over the next 50 years. These impacts fell most heavily on wards with larger shares of marginal workers, showing that economic vulnerability and residual flood risk overlap. The authors describe this as a core–periphery dynamic, where central, economically important wards are protected while peripheral or rural zones remain exposed. They point out that similar patterns are seen elsewhere, such as in Valencia in 2024 when suburban areas were flooded while the city centre was shielded, and in cities like Chennai and Kinshasa where partial defences protect urban cores at the expense of the edges. Co-author Rajarshi Majumder of the University of Burdwan noted that the worst-hit neighborhoods in Surat also had more precarious workers. Vivek Kapadia, who has worked on Gujarat's water projects, said that choosing which areas to protect is as important as the engineering of the levees themselves. The researchers conclude that levees remain necessary but should be combined with early warning systems, wetland and mangrove restoration, flood zoning, bypass channels, and reinvestment of tax revenues from protected zones into unprotected ones. 'Cities in India face tough choices with limited budgets,' Bhatia said. 'But with the right tools, data, and intent, decisions can be better balanced.'
