to the agency’s Postdoctoral Program Fellowship and was then kept on as a research scientist. So how did this gifted student from Belfast go on from studying industrial processes to approaching the Great ET question? In both areas of research, it’s about maximising results from limited means. With the metallurgical furnaces she researched for her PhD, part of the skill was to make models that could project results for vast variables and quantities without detailed data. ‘[They] get so hot. You can’t stick a thermometer in there. They can’t take coal particles out because that’s going to affect the process. So there wasn’t really data.’ This turned out to be excellent preparation for her current work. With exoplanets, sparse data is an issue. About 5,000 such planets are ‘confirmed’, but consensus holds that most, if not almost all, stars have a planetary system – and there are approximately 200 sextillion stars (that we can count!) In the study of exoplanets, the light that meets the apertures of our ground-based and orbital telescopes yields most of what we have to go on. Pinpointing them is a tricky business: exoplanets can be inferred from the gravitational wiggles effected in the star by a planet’s orbit, by spotting them in transit across the star’s direct light, or by the light bounced off them by their stars. Different telescopes give complementary data; the Hubble telescope focuses on visible parts of the light spectrum, while the James Webb gathers infrared. For better insights, we can compare models based on data from each. The gaps between what we might like to know about a given world and what we can see are vast. Enter the computational models, which supply predictive simulations based on the data gathered by astrophysicists. ‘If you really wanted to try and properly model a planet that we know very little about, you would need to know so many things about the atmosphere, about the climate, about clouds, winds, about stuff that we just don’t have.’ Nothing compares to our knowledge of our own home. Therefore, ‘assumptions’ are necessary, as with modelling particles, interactions and energy releases from a furnace. ‘One of the things we want to approximate is the phase function, describing how the atmosphere is scattering the light. A lot of that would involve working with pen and paper trying to figure out the best approximation… then you can start to write the code.’ These steps require an extraordinary combination of calculating power and the creativity needed for leaps across the gaps where concrete data is absent. What does Dr Rooney think about the Big Question itself, the one she is helping to grind into an answerable form? The existence of simple life is a probable, but hesitant yes, because the universe is too big and ‘we’re not that special.’ Intelligent life? Unknown. In both cases, caution is needed. ‘We jump into the end of the story when we’re talking about life and intelligent life. We don’t know what most of the universe is even made of – when it comes to dark matter and dark energy, for instance. There’s so many more things that we would need to understand before we could make a reasonable guess.’ A system of reasonable (ever-more-refined) guesses is perhaps not a bad summary or Dr Rooney’s models, each iteration helping to bring us closer to resolving an enormous unknown – perhaps the biggest of them all.
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