Ireland has finally joined CERN as an associate member, opening the doors of the world’s biggest scientific instrument to Irish researchers for the first time. And what a machine to step into. This week, Professor Luke takes us deep inside the Large Hadron Collider — the 27-kilometre, super-cooled, magnet-driven particle racetrack buried under the Franco-Swiss border, where protons are hurled around at 99.99991% of the speed of light and slammed together to reveal the hidden architecture of reality itself. It’s a place colder than outer space, powered by magnets a hundred thousand times stronger than Earth’s gravity, and fuelled by Einstein’s famous equation, E = mc², made real at staggering energies.

Luke revisits the extraordinary discovery of the Higgs boson in 2012 — the so-called “God particle” that explains why anything in the universe has mass in the first place. He shares the joyful chaos of that summer, including the fact that the announcement itself was made in Dublin at a conference he chaired, months before Peter Higgs shared the Nobel Prize for the theory he first proposed back in the 1960s. And in classic Luke fashion, he uses a couple of gloriously groan-inducing Higgs jokes to explain what the particle actually does.

There’s plenty of Irish flavour threaded through the science too. The very word “quark” comes from Joyce’s Finnegans Wake. The first particle accelerator ever built was constructed by Irish Nobel laureate Ernest Walton, and that original device now sits in the lobby of CERN like a relic from the dawn of the scientific universe. And Luke even finds time to salute Nick Cave, whose song about the Large Hadron Collider he reckons might be the greatest science song ever written.

With 23 member states, 17,000 scientists on site, €4.6 billion spent on building the LHC, and €1.2 billion each year to keep it running, CERN is a cathedral to curiosity — powered by collaborations, cold atoms, and a lot of superconducting metal. As Luke explains, the collider is now undergoing enormous upgrades that will push particle physics even further into the unknown, from micro black holes to new forces of nature.

It’s a reminder that when you smash particles together at nearly the speed of light, the universe doesn’t just give up its secrets… it gives up entirely new questions.

For topic suggestions or comments, email Luke at laoneill@tcd.ie.

Why do so many of us feel the gloom set in when the clocks go back and the days get short? In this week’s podcast, Luke O’Neill delves into the biology of Seasonal Affective Disorder, or SAD, a form of depression that appears in winter and lifts again when the light returns.

First identified about fifty years ago in northern Europe, SAD affects around one in every hundred people severely, and up to one in five to a milder degree. Women are three times more likely to experience it than men. Geography plays a big part too: roughly 1% of people in Florida report symptoms, compared to 10% in Alaska. Around 7% of people here in Ireland can be badly affected each winter.

Luke explains that it all comes back to our circadian rhythms — the body’s internal clock that runs on a 24-hour cycle. In low light, this rhythm can drift off course, affecting hormones like melatonin (which regulates sleep) and serotonin (which affects mood).

The good news? Light therapy works. Recent studies show that 30 minutes a day in front of a light source of 10,000 lux can help reset your body clock and ease symptoms. For comparison, moonlight gives off just 1 lux, normal indoor lighting about 300, while a bright winter’s day can reach 20,000. So, step outside when you can — daylight is the best medicine.

The Mayo Clinic also recommends using a lightbox for about 20 minutes within an hour of waking during the darker months. SSRIs, the antidepressants that boost serotonin, can also provide relief.

Scientists even suggest SAD could have evolutionary roots, a leftover human tendency to “hibernate” through the bleakest months by conserving energy, withdrawing socially, and staying indoors.

Luke ends on an optimistic note: winter may mess with our body clocks, but it doesn’t last forever — the light always comes back.

✨ This episode was suggested by listener John O’Reilly.

💡 Got a question or topic for Luke? Email him at 📩 laoneill@tcd.ie

This week, Professor Luke O’Neill turns his microscope to a condition he knows all too well — cellulitis.

It’s one of the most common bacterial infections there is, affecting about one in every 500 people each year. The skin turns red, swollen, and sore, and you might even feel flu-ish as your immune system fights back. Left untreated, it can spiral into sepsis, making early diagnosis vital.

Listener Joanie suggested this week’s theme, and you can do the same by emailing Luke at laoneill@tcd.ie. As Luke explains, cellulitis happens when bacteria slip through tiny breaks in the skin — a scratch, a cut, even an insect bite — and start multiplying. He suspects that’s how he picked it up himself earlier this year.

Rates of cellulitis are on the rise, with hospitals seeing more admissions, especially in settings where people live in close quarters: nursing homes, homeless shelters, and college dorms. Obesity and antibiotic resistance may also be fuelling the increase.

Treatment is straightforward (antibiotics usually clear it up) but prevention is even better. Keeping skin clean and moisturised, and treating any breaks promptly, can stop it taking hold.

And it’s not just humans. Cats, dogs and even horses can suffer from cellulitis, with vets watching closely for swelling and lameness. In fact, that old-fashioned poultice once used to “draw out” infection still has its place — at least in the stable.

From microbes to moisturiser, Luke explores how our skin keeps the world out. And what happens when it can’t.