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What Happens When Light Goes Boom? Part 4: What Brad Bradington Is Good For

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(This is the final part of a series on Cherenkov radiation — the “light boom.” Read Part 1, Part 2, and Part 3 first.)

So we know what Cherenkov radiation is. We know how it works. We know that Pavel Cherenkov spent three years poking a glowing bottle of water before anyone believed him.

Now: what is it good for?

The answer, it turns out, is quite a lot. Cherenkov radiation shows up in some of the most dramatic, extreme, and important contexts in modern physics. And also, wonderfully, in hospitals.

Let’s start with the most visceral image in all of nuclear physics.

You’ve probably seen photographs of nuclear reactors — the ones where the fuel rods are submerged in a deep pool of water, and the water glows. That electric, otherworldly blue. It looks almost supernatural. Like something from a science fiction film. Like the reactor has a soul, and it’s blue.

That glow is Cherenkov radiation.

The reactor’s fuel rods are constantly releasing high-energy electrons and other decay products that travel through the surrounding water faster than light moves in water. And each of those particles drags a cone of blue light behind it. Billions of them, constantly, all producing that steady cold impossible-looking glow.

What makes this particularly striking is that it’s one of the very few places in all of physics where a genuinely relativistic phenomenon is directly visible to the naked eye. Most of the deep results of modern physics are invisible to human perception. You can’t see an electron. You can’t watch a quark change flavor. You can’t directly perceive spacetime curving around a massive object. You have to trust your instruments, trust your colleagues, trust the math.

But the Cherenkov glow in a reactor pool? You just look at it. That’s the light wake of particles outracing light. That’s a consequence of Maxwell’s equations and special relativity, visible and blue, right in front of you. No mediation required.

That’s Brad Bradington, sprinting through water, leaving light in his wake. The reactor’s heartbeat, made visible.

Here’s something humbling: we didn’t invent Cherenkov radiation. The universe has been doing this constantly, everywhere, for billions of years, completely without our input or appreciation.

The upper atmosphere of Earth is continuously bombarded by cosmic rays — high-energy particles streaming in from supernovae, neutron stars, black hole jets, and other extreme corners of the universe. When these particles slam into the atmosphere, they create cascades of secondary particles, many of which are moving faster than light moves in air.

The result: brief, faint, downward-pointing cones of blue and ultraviolet Cherenkov light, flashing constantly in the upper atmosphere, all over the planet, day and night, right now. You can’t see them from the ground — they’re too faint, and the sky is too bright. But they’re there. They’ve been there since long before there was anyone to notice them, or care, or build experiments around them.

Once we knew the universe was doing this, we decided to watch.

A class of instrument called an Imaging Atmospheric Cherenkov Telescope — IACT — does exactly what the name suggests. These are large mirror arrays built at high-altitude, dark-sky sites, pointed upward. They’re not looking for light from stars or galaxies. They’re watching for the faint Cherenkov flashes produced when very-high-energy gamma rays from space hit the upper atmosphere.

When an extreme-energy gamma ray enters the atmosphere, it creates a narrow, intense cascade of secondary particles — all of them moving faster than light in air — all producing Cherenkov radiation in a tight downward cone. The flash lasts only a few nanoseconds. The telescope has to catch it instantly and reconstruct the direction and energy of the original gamma ray from the shape of the flash.

The major instruments are MAGIC on La Palma in the Canary Islands, H.E.S.S. in Namibia, and VERITAS in Arizona. Between them, they’ve mapped the gamma ray sky in extraordinary detail — finding the remnants of supernovae, the jets of active galactic nuclei, the neighborhoods of pulsars — because the atmosphere itself is the detector, and the Cherenkov flash is the signal. We took a phenomenon we didn’t create and turned it into one of the most powerful tools in high-energy astrophysics.

The most audacious application of Cherenkov radiation isn’t a telescope pointed at the sky. It’s buried in the ice beneath the South Pole.

IceCube is a neutrino detector. Neutrinos are extraordinarily difficult to detect — they have no charge, almost no mass, and interact with matter so rarely that trillions of them pass through your body every second without leaving a trace. Catching one requires either enormous patience, enormous volumes of material, or both.

IceCube chose enormous volumes. It contains over 5,000 optical sensors embedded in a full cubic kilometer of Antarctic ice, monitoring the permanent darkness for flashes of blue light.

Here’s how it works. Occasionally — very occasionally — a high-energy neutrino passing through the ice will interact with an atomic nucleus and produce a charged particle, usually a muon. That muon, if it’s energetic enough, travels faster than light moves in ice. And when it does, it produces Cherenkov radiation: a faint cone of blue light, spreading outward through the ice as the muon moves.

The sensors catch those photons. The timing and pattern of hits across thousands of sensors allows physicists to reconstruct the direction the muon was traveling — and therefore the direction the neutrino came from — and therefore the location in the universe where something violent enough to produce such an energetic neutrino must have happened.

The most elusive particles in the universe, detected not by catching them but by the light wake they leave when they’re not quite elusive enough. Brad Bradington, moving through a cubic kilometer of Antarctic ice, leaving footprints made of light.

And then there are hospitals.

PET scanning — positron emission tomography — works by injecting a patient with a radioactive tracer that emits positrons as it decays. A positron is the antimatter partner of an electron. When a positron meets an electron inside the patient’s body — which happens almost immediately, because electrons are everywhere — the two annihilate and produce a pair of high-energy gamma ray photons flying off in exactly opposite directions.

Those gamma rays travel faster than light moves through human tissue.

They produce Cherenkov radiation. The direction and timing of those faint flashes can be used to reconstruct exactly where inside the patient the annihilation happened — which tells doctors where the radioactive tracer accumulated — which reveals where the metabolically active tissue is — which can identify tumors, measure blood flow, and map neurological activity.

Brad Bradington, in a very real and non-metaphorical sense, is helping diagnose cancer.

Pavel Cherenkov’s glow in a bottle of water in 1934 has become: the visible heartbeat of a nuclear reactor. The constant invisible light show in our upper atmosphere. The foundation of gamma ray astronomy across three continents. A cubic kilometer of Antarctic ice bristling with sensors hunting the universe’s most elusive particles. A medical imaging technology used millions of times a year in hospitals around the world.

Not bad for something every previous scientist wrote off as fluorescence.

The best discoveries in science often start the same way. Not with a grand announcement. Not with a eureka moment. Not with the immediate recognition of their importance.

Just a careful person, in a quiet lab, looking at something everyone else has already looked at — and thinking:

Huh. That’s weird.

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In Alabama, Opposition to Renewable Solar Energy Joins a Data Center Battle

Tuesday’s runoff for a slot on the Alabama Public Service Commission has a familiar ring to it, with talk of data centers and electricity costs. But in a southern twist, solar power has joined the list of villains.

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New Study Assesses Titan’s Resources and their Potential Uses

Saturn’s largest moon, Titan, is a unique environment in our Solar System. It is the only moon (or body beyond Earth) to have a dense, nitrogen-rich atmosphere, and its methane cycle is very similar to Earth’s hydrological cycle, in which solid and liquid methane evaporates to form clouds and returns to the surface as precipitation. In addition, its prebiotic surface environment and rich organic chemistry make it a prime destination for astrobiology missions, such as NASA’s Dragonfly mission (set to launch no earlier than July 2028).

And as Robert Zubrin said in his book, Entering Space: Creating a Spacefaring Civilization, Saturn’s moons could become the “Persian Gulf” of the Solar System, with Titan being a major one because of its rich resource environment. In a recent NASA-supported study, a team of researchers compiled an inventory of Titan’s resources and their potential use by future generations of humans. When comparing this satellite to other destinations (i.e., the Moon and Mars), they conclude that Titan offers several potential benefits for human settlement.

The research was led by Conor A. Nixon, an astronomer and planetary scientist with the Solar System Exploration Division (SSED) at the NASA Goddard Space Flight Center and the Associate Laboratory Chief of their Planetary Systems Laboratory. He was joined by Ye Lu, a Professor of Aerospace Engineering at the Worcester Polytechnic Institute, and Jennifer E. Ruliffson, a Professor of Materials Science and Engineering at the University of Florida. The preprint of their paper has recently appeared online and is under review for publication in *Acta Astronautica*.

Artistic representation of Titan’s abundant resources and their possible uses. Credit: Nixon, C.A. et al (2026)

ISRU is a major aspect in all plans for long-duration missions to the Moon, Mars, and other locations far beyond Earth. To date, the vast majority of studies have focused on leveraging lunar and Martian resources to sustain crewed missions and eventual human settlement. With the exception of a recently proposed Titan ISRU Sample Return (TISR) mission, Titan has received considerably less attention, despite the possibilities this moon offers.

This includes opportunities for ISRU that would enable the construction of long-term habitats on the surface. In addition, they could also lead to Titan becoming a base for resupply missions traveling to and from the outer Solar System. Similarly, Titan could facilitate the exploration of Saturn’s other satellites, particularly the “Ocean Worlds” of Enceladus and Mimas, both of which are also rich in resources. Finally, its resources and products fashioned from them could be exported to other locations in the Solar System.

This includes fuel, feedstock, and basic necessities like food, water, nitrogen fertilizers, oxygen gas, and more. As Nixon told Universe Today via email:

Titan is gushing with hydrocarbons – what we call oil and natural gas on Earth. In the atmosphere, it has about 5% methane (what we call LNG and use in home heating and cooking). On the surface, we can find heavier hydrocarbons, such as propane used in BBQ tanks, butane used in lighters, and heavier liquids like kerosene and gasoline. Besides burning these hydrocarbons, we can also make a lot of products from them: plastics, synthetic rubber, and feedstocks for everything from solvents to pharmaceuticals, and even foods.

The previous study, led by Geoffrey Landis and the Compass Lab team from NASA’s John Glenn Research Center, looked at ISRU at Titan for one purpose: liquifying methane and producing liquid oxygen (LOX) and liquid hydrogen (LH₂) from water to create propellant for a sample-return mission. Nixon and his colleagues cast a much wider net, looking further ahead by examining the many possible uses of all of Titan’s resources.

*A rendering of a notional spacecraft powered by nuclear thermal propulsion. Credit: General Atomics*

They also considered how a rich resource base could be used for a wider range of mission profiles. These include missions that need to return to Earth, as well as missions that plan to explore beyond Saturn. To this end, refueling stations on the surface could be accessed by landers from a larger spacecraft that would take on fuel and supplies. Alternately, refueling depots could be built in orbit – similar to what SpaceX is investigating for the Starship – that spacecraft would rendezvous on their way to other destinations.

And as Nixon noted, there’s the possibility of harvesting resources to build long-term settlements on Titan’s surface:

Basically you could envision either ‘refueling’ at Titan (in the manner of the Oleson/Landis study), or using the resources to sustain a more permanent settlement. [And] regarding refueling, it doesn’t just have to be for a return trip to Earth: it could be refueling a ship just arrived from the inner Solar System to go further out, say to Uranus or Neptune, or to explore the Saturnian moons. Or it could just be refueling a regular shuttle that traverses around the Saturn system between colonies on different moons.

Also, we can widen the definition from just ‘fuel’ to resources for a wide variety of purposes. So let’s imagine a permanent station on Titan that refines hydrocarbons and stores them as a variety of feedstocks and raw materials: everything from printer ink to fertilizer. Then, when a visiting ship comes to ‘refuel,’ it is restocking not just fuel but raw ingredients for food, perhaps for 3D printers used to make spare parts, textiles, utensils, and more.

There’s also the large volume of water on Titan, which accounts for 50% of its mass (the rest being rocky material in its core) and exists in both solid and liquid states. The liquid portion exists largely beneath the surface, where ammonia and salinity (two natural antifreeze compounds) maintain its liquid state. Water also exists in abundance as surface ice, which could be harvested and used to provide everything from drinking water to hydrogen fuel, oxygen gas, and (as noted) to manufacture LOX/LH² propellant.

*This mosaic of Saturn’s moon Enceladus was created with images captured by NASA’s Cassini spacecraft. Credit: NASA/JPL/Space Science Institute*

After considering Titan’s resource base and the opportunities for resupply, settlement, and exploration, Nixon and his colleagues compared Titan with the Moon, Mars, and several NEAs. They determined that while Titan is much more distant and would require nuclear propulsion to enable transits, its potential is unrivaled. “There is simply no other world (that we know of) like Titan,” said Nixon. “Titan is unique in multiple respects: it’s the only moon with an atmosphere, and it’s the only planet/moon other than Earth to have hydrocarbons available in the atmosphere and on the surface.”

While the idea of crewed missions to Titan, or the settlement of this and other Cronian moons, is a far-off prospect, the potential is obvious. By establishing infrastructure and outposts in and around Saturn’s moons, humanity would have access to a huge resource base. Beyond Titan, Saturn’s atmosphere contains massive reserves of the rare isotope helium-3 (³He), considered the ideal fuel for fusion reactors and fusion propulsion. With so much water, hydrocarbons, and precious gases available, Saturn could very well become the “Persian Gulf” of the Solar System.

But as Nixon indicated, the benefits go far beyond refueling and include the means to build a manufacturing base capable of meeting all the needs of a human population. With the abundant plastics, feedstock for 3-D printers, fuel, and food that could be produced in-situ, a human settlement on Titan could endure for generations. It may be a far-off possibility, but it’s good to know that it’s there and could be fulfilled someday as part of humanity becoming an interplanetary civilization.

Further Reading: arXiv

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California high surf and coastal flooding risk continues until Wednesday

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The risk of flooding and dangerous surf at California beaches will continue until Wednesday, weather officials said Sunday.

Waves are not expected to be as big as those that pounded the shore last week and led to the deaths of two people.

The National Weather Service said San Francisco recorded its highest-ever summer ocean water level late Saturday.

At 1.83 feet above normal high tide, the level was the highest recorded outside of those occurring from November to March, when winter storms cause surges, officials said. Water level records go back to 1898.

A coastal flood advisory remains in effect through Wednesday morning, the weather service said.

The highest tides will be in the evening, officials said.

Over the last week, the greatest threat of dangerous rip currents and sneaker waves has been on the beaches facing south or southwest, officials said.

The city of Newport Beach warned residents to prepare for a series of king tides, continuing through Tuesday.

City employees have been distributing sandbags to residents to help protect their property from flooding. Officials urged those going to the beach not to park in low-lying areas.

“Motorists are urged to drive slowly through flooded areas to avoid creating wakes that can worsen flooding and impact nearby properties,” the city said in a statement.

Last week’s ocean swell brought historic 20-foot waves to the Wedge, the Newport surf break at the tip of the Balboa Peninsula.

On Wednesday, rescuers attempted to save two women who were swept out to sea from a beach in Santa Cruz. One of the women died. The other was in critical condition, officials said Friday.

The body of missing 5-year-old Amada Mia Brown of San Bernardino was recovered in Laguna Beach on Thursday, two days after she vanished in high surf.

Officials urge beachgoers to stay off rocks and jetties at times of high surf and keep an eye on the ocean.

If caught in a rip current, don’t panic, officials advised. Swim along the shoreline, rather than directly back to the beach, until free of the current’s pull.

If needed, tread water and call for help.