For Priyamvada Natarajan, her earliest exposure to scientific research arose from her childhood passion making star maps. Her love for maps never abated, and shaped her career as a theoretical astrophysicist. In the media, she’s the famous ‘cosmic cartographer’, who featured in the TIME magazine’s list of 100 most influential personalities this year.

“I realise what an honour and privilege this is,” said Natarajan to The Hindu. “It sends a message that people working in science can be seen as influential, and that is very gratifying.”

The Indian-American’s claim to fame arises from her pathbreaking research into dark matter and supermassive black holes.

She devised a mathematical technique to chart out dark matter clumps across the universe. Despite dark matter being invisible and elusive to astronomers, they’re thought to dominate some 75% of the universe’s matter. Dark matter clumps act as ‘scaffolding’, in the words of Natarajan, over which galaxies form. When light from background galaxies gets caught under the gravitational influence of dark matter clumps, they bend like they would when passed through a lens. Natarajan exploited this effect, called gravitational lensing, to map dark matter clumps across the universe.

Simulation of dark matter clumps and gas forming galaxies. Credit: Illustris Collaboration

Natarajan reflected her passion for mapping in a TEDx talk at Yale University, where she’s professor of physics and astronomy. Though she’s an ‘armchair’ cartographer, in her own description, she has resolved another major headwind in astronomy – nailing down the origins of supermassive black holes.

Black holes generally form from dying stars, after they collapse under their weight due to gravity. These black holes would swallow gas from their environment to grow in weight. However, there also exists supermassive black holes in the universe, millions of times heavier than any star or stellar-sized black hole, whose formation can’t be explained by the dying star collapse theory. One example is Sagittarius A* at the center of the Milky Way, which is a whopping four million times massive than our sun.

First direct image of Sagittarius A* at the Milky Way center. Credit: EHT

The origins of these behemoths remained in the dark until Natarajan and her collaborators shed some light to it. In their theory, massive clumps of gas in the early universe would collapse under its own weight to directly form a ‘seed’ supermassive black hole. This would grow similar to its stellar-massed counterparts by swallowing gas from its environment. In 2023, astronomers found compelling evidence to validate her theory. They reported a supermassive black hole powering the ancient quasar, UHZ1, at an epoch when no black hole could possibly have grown to attain such a massive size.

These observations came nearly two decades following Natarajan’s first paper on this in 2005. In a 2018 interview to Quanta, she expressed how content she would be with her contributions to astrophysics without having her theory requiring experimental verification done within her lifetime. For, she would be simply content at having succeeded at having her ideas resonate among astronomers for them to go search for her black holes. “I’m trying to tell myself that even that would be a supercool outcome,” she said in that interview. “But finding [the supermassive black hole ‘seed’] would be just so awesome.”

Beyond science, Natarajan’s a well-sought public speaker as well, with pursuits in the humanities as well. In fact, at Yale University, she’s the director of the Franke Program in Science and the Humanities, which fosters links between the two disciplines. Her humanities connect comes at MIT, where she did degrees in physics and mathematics before taking a three-year hiatus from science to explore her interest in the philosophy of science. However, she returned to astronomy soon thereafter, enrolling as a PhD student at Cambridge, where she worked under noted astronomer Martin Rees on black holes in the early universe which seeded her success in later years.

History perhaps would have it no other way for Peter Higgs, with his name seemingly linked forever to the ‘God particle’.

The nonagenarian Higgs, who passed away last week in Edinburgh, had expressed displeasure once that he alone received the fanfare for the Higgs boson. For in his own admission, there were some six other theoretical physicists who had come up with exactly the same idea arguably around the same time. Higgs even proposed to re-name the mechanism which led to the Higgs boson, to “ABEGHHK’tH mechanism”, in an attempt to represent the contributions of every theorist involved by having their initials. However, the name Higgs boson stuck in parlance after Benjamin Lee, a physicist in the 1970s, was better acquainted with Higgs work than the other physicists, and preferred using the former’s name as ‘shorthand’ to describe the particle.

The Nobel Committee didn’t overlook this fact, when Higgs was awarded the 2013 Nobel Prize in Physics with Francois Englert – the only one of the remaining six to be alive by that point. But they’re also the lucky few who got to see their groundbreaking work become the crowning jewel moment in their career.

Higgs, who faced much of the limelight after he directly proposed a quantum particle in his 1964 paper, had a steely resolve to defend his work from the onslaught of critique, as is rather common when radical scientific progresses are on the cusp of making.

But for a really long time though, the Higgs boson didn’t find consensus amongst particle physicists as the particle they should really fund the LHC to identify. The theory didn’t find resonance amongst leading physicists of Higgs’ time either; even Stephen Hawking, as The Guardian notes, on one occasion publicly stated the particle will never be discovered. Higgs retorted publicly likewise, saying that Hawking’s celebrity status had helped him escape accountability for his misguided statements.

At long last when the Higgs boson was finally discovered in 2012, Higgs was all teared up during the announcement at Geneva. This was perhaps a crowning moment more so than the Nobel Prize arguably, for a career well-spent in service for science.

The media hype that followed in its reporting of the Higgs boson’s discovery, also helped the particle’s longevity in popular memory. A slew of news stories popularized it as the ‘God particle’, when it is literally anything but that. The Higgs boson is a prediction arising within quantum field theory (or QFT), which accounts for the various interactions between three of the fundamental forces of nature – electromagnetism, the strong and weak nuclear forces.

At one point in time, these three fundamental forces existed in unison at the time of the Big Bang. But matter as we knew it was massless too then. it was only after a billionth of a billionth of a billionth of a billionth second after the colossal Big Bang, did the particles get imbued with mass at all, due to a mediating Higgs boson. According to QFT, the Higgs boson emerges from one of, in fact, many characteristic energy fields from which quantum particles arises and interacts. The Higgs isn’t the carrier of mass, but it is that interlocutor which mediates the Higgs field (which is what the quantum field associated with the Higgs is called) with the massless particles. In QFT, the Higgs is just another particle. 

According to Business Insider, the ‘God particle’ conception was directly derived from Nobel Prize winning physicist, Leon Lederman’s book in 1990. The planned title of his book, ‘The Goddamn Particle’ was changed to ‘The God Particle’ upon the insistence of his publishers then. Lederman’s logic was to convey how Higgs boson evaded the eyes of particle detectors of his era. But Higgs wasn’t a fan of the naming. In a 2013 interview, he said “The name itself is a sham … it was a joke, you know.”

But the term ‘God particle’ stuck in popular lore ever after, with no re-naming around the horizon.

It was in the wee hours of October 2nd, 2018, when Donna Strickland received a call from Sweden saying she was declared one of the awardees of that year’s Nobel Prize in Physics. With that she would make history, being just the third woman since Marie Curie and Maria Goeppert Mayer, to win the Nobel Prize in Physics.

Like many Nobel laureates before and even after her, it did take a moment or two for Strickland to digest the news. However, she couldn’t have felt more surprised when she realized that it wasn’t any of her research in laser physics she’d prided on being an expert on that won her the prize. Instead, she was awarded for her PhD work all the way back in the 1980s, squishing laser pulses to generate powerful beams. 

Her work came at a time in the 1980s when laser physicists faced difficulty increasing laser power beyond a threshold, when it could damage its casing and the apparatus.

By 1985, Strickland helped materialize a work-around solution proposed by her then PhD supervisor, Gérard Mourou. They had laser light pass through a prism, splitting them to produce a rainbow-like distribution of individually low power light beams. These would then be passed through a power amplifier, before being forcibly recombined into an extremely intense laser pulse. For this work developing the mechanism called, ‘chirped pulse amplification’ (CPA), Strickland and Mourou were each awarded one-quarter of the Nobel Prize. The other half was awarded to Arthur Ashkin, for his work developing tiny particle traps using optical laser beams. 

A laboratory set up consisting of lasers passing through lenses and mirrors. These are continuous wave lasers, as opposed to pulsed lasers. Credit: Wikimedia

Their work removed the roadblock to building lasers with shorter pulses that were below femtoseconds (a billion times shorter than a microsecond) and ever higher power beyond pettawatts (thousands of billions of times powerful than a kilowatt source). Frontier research today uses these pulsed lasers to cut through metals, in experimental nuclear reactors to trigger fusion in pellets of hydrogen. But their usage extends well beyond the confines of the laboratory too. For example, LASIK surgery to correct eye power became a reality after intense ultraviolet pulsed lasers were shown to reshape the eye’s cornea. They’re a basic concept behind military applications such as directed-energy weapons.

Pulse waveforms of a 2.5 nanosecond pulse duration (much bigger than the lasers Strickland and Mourou worked on, that clocked in picoseconds – a thousandth of a nanosecond). Credit: Wikimedia / NIST

In the wake of CPA’s invention, Strickland and Morou moved onto researching different problems within laser physics, and led diverged career paths. However, Strickland, for one, had rather a very slow progression up the ranks. In fact, when the Royal Swedish Academy announced the 2018 physics laureates, Strickland wasn’t even a full professor at the University of Waterloo, Canada. Worse still, her recognition was stalled outside of academia until a Wikipedia page had to be propped after the Nobel Prize was announced. 

This became a hot topic after Strickland’s win since it ruffled the feathers of scientists, particularly women commentators at one point, who saw in Strickland, a potential to be an influential role model for girls and women in STEM. For she was just the third physics laureate at the time, after Marie Curie and Maria Goeppert Mayer, and the first in a very long time after Mayer was awarded in 1963. 

It turned out Strickland didn’t really apply to be promoted, and only did so following her Nobel Prize upon being beckoned by her well-wishers. Waterloo fast-tracked their final decision to promote her in just three weeks, which in any other scenario would have been an intense and long-drawn process altogether. 

But the lack of sufficient academic recognition did color views on her and her work in public. As it later turned out, Wikipedia editors denied a page in her name, deeming her three decade research into laser physics as insignificant. 

In fact, Strickland herself recalled being stunned that she was being awarded for her contribution decades ago.  “This work was done over thirty years ago so it’s not something that I am living and breathing every day … No one is expecting, in my position, to win a Nobel Prize,” she said. 

It’s unknown why exactly there has been a three decade long wait for laser physics to be awarded any Nobel Prize at all. Delaying consensus within the Nobel committee for the award can mean researchers may not even live to be awarded. The Nobel Prize doesn’t award posthumous awards. Arthur Ashkin, the third 2018 physics Nobel laureate, was already 96 years old and a retired emeritus professor. He passed away in 2020. However, understanding how the Nobel committee made the decisions that they did will have to wait another 44 years. when the nomination lists for the 2018 prize will be publicly released. 

For Strickland, life can’t have been more different after winning the prize. To girls and women, she was a rockstar in science, being the first woman to win a physics Nobel in a long time. However, she knows how much it means to them what being a scientist is like in her younger days. 

During her school days, Strickland stood out to gain both positive and negative attention. Positive, because she aced physics modules. But negative, in that, she was studying physics which was seen traditionally as a boys’ subject, and was questioned for her choices. Although her contribution to CPA wasn’t publicly acknowledged as much as it ever did only after three decades, Strickland did find some admirers soon after her work on CPA was published in 1985.

“I would like to acknowledge my homeroom teacher, Jim Forsyth, who was also my physics teacher in Grade 13,” Strickland said, as quoted in the 2018 Nobel biography. “When I returned to Canada as a faculty member at the University of Waterloo, he read that I had developed chirped pulse amplification. He contacted me through my mother asking if I would be willing to be placed on [her school’s] wall of fame. I wasn’t sure that I belonged on this wall that included John McCrae (a famous Canadian poet). Jim said that he wanted to have a female scientist on the wall as a role model for the female students. I agreed to his request and he made it happen. I have been on [her school’s] wall of fame for two decades for the development of CPA. They recently have rewritten the citation to say that I have received the Nobel Prize for CPA. Now it doesn’t seem so strange for me to be on [her school’s] wall of fame.”