Category: physics

Three scientists nab Nobel for Physiology or Medicine for work on optogenetics, one physicist wins for work on neutrinos

October 6, 2026 • 8:15 am

I completely missed the Nobel award in biology yesterday, but I see that one has been awarded this morning in physics. The former involves three scientists, the latter a lone physicist.

The Medicine or Physiology prize release is here. It describes advances in “optogenetics,” the use of optical signals to detect how neurons work. It’s very clever, based on an algal protein, rhodopsin, that is activated by light and, when put in a nerve cell, will create an impulse when the cell is illuminated by blue light.

There’s a clear discussion of the Prize-winning research at The Conversation (click below to read):

A summary:

Scientists who worked out how to control brain cells with light have won this year’s Nobel prize in physiology or medicine. Karl Deisseroth, Peter Hegemann and Georg Nagel were honoured for their research into “light-gated ion channels and optogenetics”.

Peter Hegemann, at Humboldt University of Berlin, and Georg Nagel, at the University of Würzburg, wanted to understand how a tiny, single-celled alga called Chlamydomonas senses light. Light-sensing is not unique to animals with eyes: organisms throughout the living world use light to detect their surroundings and respond to changes in their environment. Even single-cell organisms have proteins that respond to light. These proteins are used to move towards or away from light, to generate energy and to respond to the various demands of a 24-hour day.

Hegemann and Nagel discovered that Chlamydomonas has a beautifully ingenious mechanism of light detection that relies on a single protein called channelrhodopsin.

Channelrhodopsin is built into the outer membrane of the algal cell. Part of the protein faces the water outside the cell and part faces the inside. The protein also contains a small molecule called retinaldehyde, which is able to absorb light.

When light hits the retinaldehyde inside channelrhodopsin, it changes shape. This makes the channelrhodopsin protein change shape too. That change opens a tiny passage through the cell membrane. Positively charged particles, including sodium, can then flow from the water outside the alga into the cell. This movement of charged particles sends a signal inside the alga that helps it swim.

The researchers realised that if they could put channelrhodopsin into nerve cells, they might be able to switch those cells on simply by shining a light on them. That is exactly what Hegemann, Nagel and the third Nobel-prize winner, Karl Deisseroth, a psychiatrist and bioengineer at Stanford University in California, went on to do.

. . . and how it’s used, with a cool example:

The ability to control nerve cells with light is called optogenetics. It has become a powerful research tool because scientists can use it to switch specific groups of nerve cells on and off and see what happens.

First, scientists deliver the gene for channelrhodopsin to the nerve cells they want to study. The gene is usually carried into the cells by a virus that has been altered so that it cannot cause disease. The cells then make the channelrhodopsin protein, which makes them respond to light.

In animals such as mice, scientists can shine light into the brain through a thin optical fibre. When the light reaches the cells, channelrhodopsin opens and the cells become active. Nearby nerve cells that do not contain the protein are unaffected.

Light can be aimed at a very small part of the brain and switched on and off extremely quickly. This makes optogenetics a powerful way to investigate how the brain works. For example, if scientists want to know whether a particular group of nerve cells is involved in memory, sleep, sensation or movement, say, they can switch those cells on with light and see what happens.

In one experiment in 2012, a team at the Massachusetts Institute of Technology gave mice a mild electric shock in a particular cage. They used optogenetics to tag the nerve cells in the brain’s memory centre that were active during that the fear-conditioning experiment. Days later, in a different cage, they switched those cells on with light. The mice froze in fear, as if they remembered the shock.

Mice that were not shocked did not freeze, which showed that the light was reactivating a specific memory. Deisseroth was one of the study’s authors.

***************************************

And the press release for the physics prize is here. An excerpt:

Francis Halzen realised that ice at the South Pole could be used to track particles known as neutrinos. His vision and scientific leadership have been fundamental for the IceCube Neutrino Observatory – a cubic kilometre of ice that is equipped with light sensors. Using IceCube, researchers can capture neutrinos from extremely energy-rich processes in the distant universe.

Neutrinos are everywhere, but they do not make themselves known. They pass all the way through the Earth and through our bodies without us noticing. Very rarely, a single neutrino will interact with an atomic nucleus, which makes it possible for someone with the right equipment to discover them.

Scientists have long known that the cosmos contains natural particle accelerators, which fire out particles with energies up to a million times more than can be achieved in laboratories on Earth. Much about these sources is mysterious: what are they, where are they, and what are the main processes inside them?

Neutrinos with extremely high energies are created in the same environments as other types of particles. However, unlike other particles, neutrinos reach us without changing direction or losing energy. This means they can provide information that is not available in any other way.

Francis Halzen first presented his vision for capturing neutrinos at the South Pole in 1988. When a neutrino collides with an atomic nucleus, it produces a flash of light that can be tracked by sensors in the clear glacial ice. The South Pole’s ice has many advantages, as it is free from various types of interference and the area is geologically stable, with no earthquakes. Halzen and his idea soon gained the support of other researchers and, just a few years later, preliminary testing was conducted on sensors in ice.

Cosmic neutrinos with extremely high energies are very rare, so an enormous volume of ice is needed to observe an adequate number of collisions. IceCube covers an entire cubic kilometre and was finished in 2011. Researchers soon discovered the first high-energy neutrinos and, a few years later, could publish their discovery of neutrinos that must originate far outside our solar system. The search for the universe’s neutrino sources could begin in earnest.

“Francis Halzen has led an international team of researchers and engineers who have provided us with a fantastic instrument. His tenacity and scientific vision has paved the way for a new kind of astronomy,” says Mark Pearce, Chair of the Nobel Committee for Physics.

The neutrino interactions that are continuously collected by IceCube will provide researchers with novel knowledge about the violent settings in which high-energy neutrinos can be created – and could even reveal previously unknown cosmic phenomena.

Here’s the apparatus and how it works, taken from the Nobel Prize press release. See if you can read it by clicking to enlarge. The observed ice and detectors are buried way underground. Just getting this damn thing set up at the South Pole would merit a prize by itself!

Now perhaps some reader with expertise can tell us in the comments why high-energy neutrinos from outside the solar system are so important compared to lower-energy neutrinos from, say, the Sun.

New surveys of physicists show them united on some scientific issues, but divided on most

May 17, 2026 • 9:30 am

British physicist and science popularizer Phil Halper emailed me about two new surveys he and others had conducted with 1675 physicists, asking their views about fundamental questions in the field.  This is not, of course, a guide to the truth, but simply a snapshot of where physicists stand on things like quantum gravity, black holes, and the Big Bang.  The links to the surveys are in the text below, sent by Phil. I’ll highlight a few of their stands on interesting (to me) issues. Phil’s words are indented:

My co-authors and I just released the largest survey of physicists ever done. In conjunction with the American Physical Society we got more than 1600 replies to our Big Mysteries Survey.

What’s relevant for debates between believers and non believers is that we only got a large consensus on one topic and that is the Big Bang should be understood only as a theory that says the universe evolved from a hot dense state that says nothing at all about a beginning of time . Interestingly, we got 68% in both this large survey of a broad cross section of physicists and for a smaller scale survey we did of leading physicists in Copenhagen with the Niels Bohr Institute. This seriously undermines William Lane Craig’s Kalam cosmological argument which is defended by claiming that physicists agree that the Big Bang has shown that the universe had a beginning, we now have strong empirical evidence that physicists think no such thing.

On the fine tuning argument the most popular answer  was that constants are brute facts that need no explanation. This was found in both of our survey and in the Phil papers survey of philosophers.

You can see the results here

And the Copenhagen Survey is here.

JAC: The Copenhagen Survey involved views of 151 physicists attending a conference on black holes in 2024.

And there is a video with Sean Caroll, Niayesh Afshordi, and Ghazal Geshnizjani discussing the results here. [JAC: I’ve put the video below.]

You might also enjoy the recent debate I did on science, cosmology and faith with Stephen Meyer here.

I haven’t yet watched the videos, but I did look at the big survey; you can access the pdf for free by clicking on the screenshot below:

First, a bit of methodology from the paper:

In the summer of 2024, a survey was conducted at the Black Hole Inside Out Conference in Copenhagen to assess physicists’ views on a range of ongoing controversies [1]. Eighty-five scientists responded. One year later, the authors collaborated with the American Physical Society’s Physics Magazine on a substantially larger follow-up survey, which polled 1,675 participants from the magazine’s readership and the members of the American Physical Society. The Physics Magazine survey therefore provides a broader view of attitudes within the physics community and allows comparisons with the more focused conference-based Copenhagen sample.

Taken together, the two surveys make it possible to compare views expressed in a specialist conference setting with those expressed by a much larger and more heterogeneous respondent pool. On some topics, the results are remarkably similar; on others, the differences are substantial. This paper presents the Big Mysteries Survey results, offers commentary on their interpretation, and highlights points of agreement and divergence relative to the Copenhagen survey

Here are a few bar charts from the paper. First, what the Big Bang implies (Sean Carroll explains this at the beginning of the video below).  A big majority of physicists think that the Big Bang says nothing about whether it marked the ‘beginning of time”:

Of course tyros like me have no idea why the Big Bang doesn’t imply the beginning of time, but so be it: all of this is above my pay grade but I’m happy to see where physicists stand on these issues now.

What about cosmic inflation? A bit more than half of physicists think that cosmic inflation (the expanding universe) explains “an unexpected uniformity” of the universe.

Dark matter: does it explain anomalies in the rate of rotation of galaxies? No consensus:

Also no consensus on whether dark energy explains the accelerating expansion of the Universe:

There’s no consensus on why the universe’s physical constants appear to be “fine-tuned” for the existence of worlds that can produce life. (This is a favorite theological argument for God.) The “brute facts” explanation brings a stop to searching for explanations, but only 26% of physicists hold it.  20%—and I think this includes Carroll—think it’s explained by a multiverse.

There are more graphs, but I’ll show just one more. What kind of picture of the Universe is provided by quantum mechanics? The Copenhagen explanatoin, which people like me can’t reconcile with physical reality, is the favored explanation. I believe it was Feynman who said that if you think you understand quantum mechanics, you don’t. I’m still baffled by the issue of quantum entanglement, and don’t even understand the experiments buttressing it.

And here’s the video with Sean Caroll, Niayesh Afshordi, and Ghazal Geshnizjani.  Carroll, as usual, gives some very succinct and lucid explanations. The other physicists are good as well.

Have a look at the paper for more opinions, including about what black holes mean and what they do.

Readers’ wildlife photos

November 20, 2025 • 8:15 am

We have two batches left and this is one of them (i.e., send in your photos). Today we have some photos of the Aurora Borealis (and a few other things) taken by Ephraim Heller:

I was fortunate to be in Alaska on the night of Nov. 11-12 when the aurora borealis put on the best show of the year, widely visible across North America. I photographed the event at Birch Lake, about 50 miles southeast of Fairbanks.  I shot the aurora from 10pm – 3am as the temperature registered -16° F (-27° C) and I coughed with a cold. It was worth it.

“Aurora borealis” is Latin for “northern dawn.” Despite my wasted BA in Physics, I have never understood what causes the aurora. I decided to look it up and share what I learn with readers of WEIT. Real physicists and astronomers should feel free to correct my errors. Thanks to NASA and to Akari Photo Tours for nice explanations on their websites, from which I have borrowed liberally.

Our sun continuously emits a stream of charged particles (the solar wind) which flows outward through the solar system. When this plasma reaches Earth, it interacts with our planet’s magnetic field (the magnetosphere), depositing and accumulating energy there. During a geomagnetic storm, much of the accumulated energy in the magnetosphere flows down along Earth’s magnetic field lines. As these accelerated particles descend into the atmosphere they collide with oxygen and nitrogen molecules at altitudes between 100 and 300 kilometers. These collisions excite the atmospheric gases, causing them to emit photons.

The detailed version: coronal mass ejections (CMEs) are the eruptions of plasma and magnetic field from the Sun’s atmosphere that drive the most intense geomagnetic storms. If directed at Earth, fast-moving CMEs can reach our planet in as little as 15 hours traveling at ~6.2 million mph (10 million kph).

The critical process triggering auroras is called magnetic reconnection. The solar wind flows around Earth’s magnetosphere like a river rushing around a rock. This onrush of charged particles stretches Earth’s magnetosphere away from the Sun, creating a long wake known as the magnetotail. The magnetic shields of the Sun and Earth are polarized. The polarity of Earth’s magnetic shield is mostly stable, but the Sun’s can vary rapidly. When the polarity of the solar wind is opposite that of Earth’s magnetosphere, the field lines of the Sun and Earth interact strongly. The solar wind then pushes these connected field lines around Earth’s magnetosphere. Eventually, these field lines reach their limit and snap back, releasing energy. This energy accelerates charged particles – primarily electrons and protons – along Earth’s magnetic field lines toward the polar regions, injecting millions of amps into the atmosphere.

Oxygen excited to different energy levels can produce green and red. Green occurs roughly between 60 to 120 miles (100-200 km) altitude, and red occurs above 120 miles (200 km). Excited nitrogen gas from about 60 to 120 miles (100-200 km) glows blue. Depending on the type and energy of the particle it is interacting with, nitrogen can give off both pink and blue light. If it is below about 60 miles (100 km), it gives the lower edge of the aurora a reddish-purple to pink glow.

Aurora brightness depends on (i) the intensity of solar activity and (ii) the efficiency of energy coupling into Earth’s magnetosphere. The standard measurement for the intensity is the Kp index, which ranges from 0 to 9, derived from 13 magnetometer stations globally that monitor Earth’s magnetic field disturbances. A Kp index of 0 represents quiet conditions; a Kp of 9 represents an extreme geomagnetic storm capable of producing auroras near the equator.

Unfortunately, the Kp index has a serious limitation: it reports a 3-hour global average so it is often too slow and too generalized to capture short-lived auroral activity, such as auroral substorms (which typically last 10 – 30 minutes). These powerful bursts can produce the brightest northern lights displays, yet they are frequently missed when relying only on KP forecasts.

Aurora intensity also depends critically on the interplanetary magnetic field’s Bz component. When the solar wind’s magnetic field points southward (negative Bz), conditions favor magnetic reconnection and enhanced energy coupling, producing increased aurora activity. When it points northward (positive Bz), reconnection is suppressed, resulting in reduced activity. Bz values below -10 nT are considered effective for driving geomagnetic storms, and values in the range of -20 to -30 nT usually indicate strong conditions for auroral activity.

Unfortunately, there is no way to predict the Bz. So even when the Kp is high there will be no aurora if the Bz is positive… and you just won’t know until you’re standing next to a lake outside of Fairbanks in -16° F weather with a respiratory infection.

So what happened on the night of November 11-12? Two coronal mass ejections reached earth, the Kp spiked to 8.67 (almost at the maximum value of 9), while the Bz reached a remarkable nadir of -55 nT!

Finally, I have been asked why photographs of auroras often appear more colorful and detailed than what observers perceive with the unaided eye. This is largely an artifact of low-light aurora viewing conditions. Auroras typically produce illumination levels comparable to moonlight, near the threshold of human vision. As you all know, there are two types of photosensitive cells on your retina: cones and rods. Under well-lit conditions, your eyes use cones to process light, known as photopic vision. The cones are responsible for color vision but are not responsive to low light. In very dark environments, rod cells dominate what you see, known as scotopic vision. Colors are barely perceptible under scotopic vision, leading to almost black-and-white, desaturated vision. Your eyes adapt to a low-light environment by transitioning sensitivity from the cones to the rods, which takes 20–30 minutes to complete.

While the eye’s photoreceptors are sensitive, they cannot accumulate light over time in the manner that digital sensors can. A camera sensor employs multiple mechanisms to collect more light than the eye: high ISO sensitivity amplifies the signal, long exposures integrate light over several seconds, and the full spectral response captures wavelengths across the visible spectrum.

Consequently, a faint aurora appearing as a low-contrast feature to the eye reveals more defined coloration in a photograph. As aurora intensity increases, the eye’s color perception approaches what cameras record. Additionally, wide-angle lenses compress perspective differently than human peripheral vision, altering the apparent geometry and apparent motion of auroral structures.

For the photography geeks among you, all of these photos were taken with a Nikon Z8 camera and NIKKOR Z 20mm ƒ1.8 S lens at ISO 3200, ƒ1.8, and shutter speeds of 1.0 second (occasionally up to 2 seconds).

And since this is supposed to be a post of readers’ wildlife photos, here are two images that I made near Fairbanks:

Reindeer or caribou (Rangifer tarandus):

Muskox (Ovibos moschatus):

Once again, theologians get paid for making stuff up

July 16, 2025 • 9:00 am

I am in fact surprised that two Iranian philosophers (yes, from the Department of Philosophy of Science, Sharif University of Technology, Tehran, Islamic Republic of Iran) are even allowed to publish this paper, which refers to God, not Allah, and doesn’t mention the Qur’an.  Well, that’s a good question, but not the question masticated in this paper in the journal Open Theology (click title to read or see the pdf here.

What we have is the usual kind of Sophisticated Theology™: a paper raising a question based on unsupported premises (there is a god that is kind, omnipotent and loving), and which then goes on to make up an answer about how certain baffling phenomena in the Universe can comport with such a god. Normally the topic of such inquiry is theodicy: why there is evil (especially “natural evil,” like childhood cancer or earthquakes) in a world made and run by such a god. This time, though, the topic is randomness. How, the sweating pair of theologians ask, can true randomness, untouched by God, exist in his Universe? More than that: how can true randomness, as part of the evolutionary process, unerringly wind up producing a species made in God’s image. As the authors ask, pretending to be puzzled:

. . . . from a theological perspective, the randomness and lack of purpose in the evolutionary process appear to conflict with God’s power, sovereignty, and wisdom.

Theologians cannot let this stand, for nothing can be allowed to conflict with God’s assumed wonderfulness and power. Nor do they assume that the randomness and lack of purpose in evolution comes from—could it be?—Satan.  No, in the end it’s all part of God’s plan.

The authors first discuss two types of randomness: stuff that appears to be random to us but in reality could be understood, or even predicted, if we had perfect knowledge. Whether a coin comes up heads or tails (or edge!) is this type of randomness.

The other type, which the authors take it upon themselves to comport with God, is fundamental, unpredictable (“ontological”) randomness—chance inherent in a system that cannot be predicted, even with perfect knowledge.  Quantum-mechanical “randomness”, or quantum probabilistic outcomes, are of this type. As the authors say:

In contrast, the real challenge for the relationship between God and the world lies in the existence of ontological or metaphysical randomness, which suggests that chance is an inherent aspect of the world’s structure and is inseparable from its dynamic nature. Ontological randomness cannot simply be viewed as a reflection of our inability to gain a certain understanding or a cognitive deficiency in comprehending the physical world. In other words, ontological randomness suggests a type of randomness inherent in the fundamental indeterminacy of the natural world. When every explanation of cosmic, macroscopic, and even biological phenomena relies on the principles of particle physics – which itself is characterized by intrinsic indeterminacy and stochastic events – it appears that we are confronted with ontological randomness.

. . . Ontological randomness. . . refers to events that cannot be predetermined in principle. Contrary to the views of proponents of ID, evolutionists argue that randomness is inherently non-purposeful. It is not merely a matter of attributing randomness to mutations due to our limited epistemic capacity to analyze the complex systems involved in the causal processes – similar to our inability to fully understand the causes of earthquakes or the movement of airborne particles. Rather, the fundamental indeterminacy of these processes means that no one can predict when they occur, much like our lack of access to the origins of nuclear emissions from Uranium-238.

Now the authors assume that evolution is driven by ontologically random mutations (“random” meaning, in the evolutionary sense, that the chance that a mutation will occur has nothing to do whether it will increase or decrease the bearer’s reproduction).  This itself may not be a good assumption, for, if we had perfect knowledge, we might be able to predict when and where a change in the DNA might take place. The role of quantum phenomena in mutation (if there is such a role) is still unknown.

But let’s be charitable and assume that yes, mutations in the evolutionary process are like movements of electrons: ontologically unpredictable. How could such a process not reflect decisions of God and yet wind up with his most desired of all “creations,” Homo sapiens.

Here’s the authors’ answer:

Our preferred reconciliation does not view the relationship between God and the natural world as a dualistic one. Any dualistic perspective ultimately leads to the problem of interaction and, consequently, the “God of the gaps” fallacy. Instead, we embrace the open theistic view, which holds that the world exists within God. Although the divine transcends the natural world, it is also immanent within it; thus, the evolutionary process occurring in the world unfolds as a manifestation of God’s self-expression and self-consciousness.

The world is progressing toward God’s self-consciousness through the evolutionary process, which has culminated in human beings who exist within the natural world, are part of nature, and possess awareness of both their surroundings and of God Himself. In this perspective, the process of evolution becomes a revelation of God’s nature. God reveals Himself in the universe by becoming increasingly self-conscious, and this self-consciousness fosters freedom; true freedom arises from autonomy rather than heteronomy, and autonomy is rooted in self-awareness. The divine is indeed the sovereign designer and intelligent architect of the world, but does not merely create from a position of supreme distance. As Carl Schmitt notes, “The sovereign, who in the deistic view of the world, even if conceived as residing outside the world, had remained the engineer of the great machine, has been radically pushed aside. The machine now runs by itself.“

If you detect a whiff of pantheism here, you’re right, and the authors admit it (bolding is mine):

According to our panentheistic and open-theistic view, God is the designer of the world, which serves as a revelation of the divine mind and nature. God does not reside outside the world; rather, the divine is immanent within it and transcendent of it. The world does not operate on autopilot. The randomness we observe in the world signifies divine sovereignty and omnipotence, granting the world the necessary freedom to reveal its nature, which simultaneously unveils the nature of God.

Of course that last bit is totally made up, for the authors have no way of knowing that this is true of God (remember, they can’t even show us that there’s a God). This disproves the idea that the “clash” of ideas instantiated by freedom of speech will eventually arrive at the truth.  Theology is one disproof of that idea, for it and its understanding of gods haven’t advanced one iota despite many clashes of ideas.

But of course God being all-knowing, somehow must have realized that the randomness He himself created would produce, with the help of natural selection, a creature made in His own image. Isn’t that special?

These lucubrations are part of what is called “open theology,” in which God grants the world freedom. Not just physical freedom, but its result, real free will (which of course the authors see as ontologically unpredictable, though it isn’t).  In their drive to make up a concept of God that comports with ontological randomness, they hit on an answer that isn’t new: God wanted a world with maximal freedom because such a world is the best of all possible worlds:

The traditional view of divine sovereignty is often characterized by the notion of God having full control over every event, leading to the idea of eternal predetermination. This dominant perspective in the history of Abrahamic religions posits that the existence of ontological randomness implies that the entire system is not under God’s control, allowing for procedures that operate without purpose under divine sovereignty. However, according to open theism, we should comprehend God’s sovereignty in harmony with divine mercy. Thus, divine sovereignty does not imply a paternalistic control over all things; rather, it embodies the granting of freedom. The truly powerful agent bestows life and freedom, enabling others to flourish instead of confining and controlling them. The Almighty is not merely an omni-controller or authority but a liberator, allowing all creatures to choose their own paths according to their inherent potential and encouraging them to reveal their capabilities. This process of world disclosure is itself a manifestation of God and contributes to divine self-consciousness.

So God’s at the wheel after all, and the freedom he bestowed on the world includes the freedom of children to die of cancer and of the tectonic plates to cause death-dealing earthquakes and tsunamis. (This kind of theodicy the authors don’t explain.)

I can’t bear to go on much longer as I watch the sweat-sodden authors make a virtue of necessity, but I’ll quote one more bit to show how they do this. As one sees so often in Sophisticated Theology™, they simply attribute their solution to another theologian, as if citing yet another shill somehow justifies their own “solution”:

As Bradley eloquently explains, power, when understood in the context of mercy and love, does not necessitate complete control; rather, it signifies the full endowment of freedom and life. The omnipotent is the one who most effectively enables creatures to experience life freely, filled with love and happiness. Certainly, God has a distinct plan, a desired program, and a unique teleology for creation; however, this teleology unfolds through its manifestation in nature, as the natural world evolves through its history.

. . . From this perspective, the randomness present in mutations reflects the freedom that God grants to all creatures. Through the evolutionary process, the world progresses toward an outcome of self-consciousness. Consequently, human beings emerge as the result of this evolutionary journey, possessing the capacity to understand their place in the world and, as part of the natural order, becoming aware of the world itself.

It always amazes me that theologians who can offer no convincing proof of a god’s existence are so sure about god’s nature and his methods.  How do they know this stuff?  The answer is that they don’t: they are either making stuff up or stealing ideas from their predecessors.

You may have noted that yes, there is teleology here. There is surely not complete freedom, as a rerun of evolution, if quantum mechanics has any effect on mutations, would not necessarily produce either consciousness or humans. And yes, the randomness isn’t true ontological randomness because it is biased towards getting what God wants (my bolding):

. . . . if we see God as immanent in the world and, so, in a panentheistic view according to which God is transcendent of the world but is not separated from nature, then we can explain why nature is biased toward the marvelous. The reason is that nature is manifesting God’s marvelous beauty.

To that, all I can say is “oy vey!”

In the end, then, the authors have produced nothing new. They’ve espoused pantheism, in which the God-who-is-in-everything has set up the world so it produces “the marvelous”, i.e. H. sapiens. This is not novel, and it’s not even ontological randomness. It is hooey. And two Iranian philosophers of science have gotten paid to produce it. The only question is not why they go on about this stuff at such length, but how the journal Open Theology was willing to publish a paper with such a mundane answer. Do they apply no critical standards? The answer is in the second word of the journal’s title.

The biggest question, though, is how I can be on an Arctic trip and have time to go after such bushwah. The answer to that one is that today is a sea day, and I don’t have a book to read or wish to watch television.

Bushwah!

h/t: B. Charlesworth

A psychedelic bubble

June 2, 2025 • 12:00 pm

Here’s an amazing video sent to me by reader Bryan Lepore. I didn’t quite understand what it showed, and he explained:

I think it is simply this:

1. Create a soap bubble from a soap solution that is sitting in a speaker/woofer.

2. Shine a light on the bubble. Here, you can see a ring of dots—that is simply a strip of LEDs in a ring. I have a light strip like this, and it produces unexpected results compared to an incandescent light.

3. Activate the speaker with different frequencies. This vibrates the bubble and the reflected image of the LED light strip.

… does that make sense?

Yep, sure does.

Guest post: does atmospheric chemistry suggest there’s life on another planet?

May 30, 2025 • 10:00 am

Today we have a guest post from reader Coel Hellier, who does this kind of stuff for a living. His text deals with the recent kerfuffle about whether a nearby planet shows an atmospheric gas indicative of life.  I particularly like the details about how scientists go about analyzing a question like this. His text is indented, and he’s added the illustrations.

Is the dimethyl sulphide in the atmosphere of exoplanet K2-18b real?

Everyone is interested in whether there is life on other planets. Thus the recent claim of a detection of a biomarker molecule in the atmosphere of an exoplanet has attracted both widespread attention and some skepticism from other scientists.

The claim is that planet K2-18b, 124 light years from Earth, shows evidence of dimethyl sulfide (DMS), a molecule that on Earth arises from biological activity. Below is an account of the claim; I try to include more science than the does mainstream media, but do so largely with pictures in the hope that the non-expert can follow the argument.

Transiting exoplanets such as K2-18b are discovered owing to the periodic dips they cause in the light of the host star:

And here is the lightcurve of K2-18b, as observed by the James Webb Space Telescope, showing the transit that led to the claim of DMS by Madhusudhan et al.:

If we know the size of the star (deduced from knowing the type of star from its spectrum), the fraction of light that is blocked then tells you the size of the planet.

But we also need to know its mass. One gets that from measuring how much the host star is tugged around by the planet’s gravity, and that is obtained from the Doppler shift of the star’s light.

The black wiggly line in the plot below is the periodic motion of the star caused by the orbiting planet. Quantifying this is made harder by lots of additional variation in the measurements (blue points with error bars), which is the result of magnetic activity on the star (“star spots”). But nevertheless, if one phases all the data on the planet’s orbital period (lower panel), then one can measure the planet’s mass (plot by Ryan Cloutier et al):

So now we have the mass and the size of the planet (and we also know its surface temperature since we know how far it is from its star, and thus how much heating it gets).  Combining that with some understanding of proto-planetary disks and planet formation. we can thus dervise models of the internal composition and structure of the planet.

The problem is that multiple different internal structures can add up to the same overall mass and radius. One has flexibility to invoke a heavy core (iron, nickel), a rocky mantle (silicates), perhaps a layer of ice (methane?), perhaps a liquid ocean (water?), and also an atmosphere.

This “degeneracy” is why Nikku Madhusudhan can argue that K2-18b is a “hycean” planet (hydrogen atmosphere over a liquid-water ocean) while others argue that it is instead a mini-Neptune, or that it has an ocean of molten magma.

But one can hope to get more information from the detection of molecules in the planet’s atmosphere, a task that is one of the main design goals of the James Webb Space Telescope [JWST]. The basic idea is straightforward: During transit, some of the starlight will shine through the thin smear of atmosphere surrounding the planet, and the different molecules absorb different wavelengths of light in a pattern characteristic of that molecule (figure by ESA):

So one observes the star both during the transit and out of transit, and then subtracts the two, and the result is a spectrum of the planet’s atmosphere.

If the planet is a large gas giant with a fluffy, extended atmosphere and is orbiting a bright star (so that a lot of photons pass through the atmosphere), the results can be readily convincing. For example, here is a spectrum of exoplanet WASP-39b with features from different molecules labelled (figure by Tonmoy Deka et al):

[I include a plot of WASP-39b partly because I was part of the discovery team for the Wide Angle Search for Planets survey, but also because it is pretty amazing that we can now obtain a spectrum like that of the atmosphere of an exoplanet that is 700 light-years away, even while the planet itself is so small and dim and distant that we cannot even see it.]

The problem with K2-18b is that the star is vastly fainter and the planet much smaller than WASP-39b. This is at the limit of what even the $10-billion JWST can do.

When you’re subtracting two very-similar spectra (the in- and out-of-transit spectra)  to look for a rather small signal, any “instrumental systematics” matter a lot. Here is the same spectrum of K2-18b, as processed by several different “data reduction pipelines”, and as you can see the differences between them (effectively, the limits of how well we understand the data processing) are similar in size to the signal (plot by Rafael Luque et al):

The next problem is that there are a lot of different molecules that one could potentially invoke (with the constraint of making the atmospheric chemistry self-consistent). For example, here are the expected spectral features from eight different possible molecules (figure by Madhusudhan):

To finally get to the point, I show is the crucial figure below. Nikku Madhusudhan and colleagues argue — based on an understanding of planet formation, and on arguments that planets like K2-18b are hycean worlds [with a liquid water ocean under a hydrogen-rich atmosphere], and from considerations of atmospheric chemistry, in addition to careful processing and modelling of the spectrum itself — that the JWST spectrum of K2-18b is best interpreted as follows (the blue line is the model, the red error bars are the data):

This interpretation involves large contributions from DMS (dimethyl sulphide) and also DMDS (dimethyl disulphide) — the plot below shows the different contributions separated — and if so that would be notable, since on Earth those compounds are products of biological activity—mainly from algae.

In contrast, Jake Taylor analysed the same spectrum and argues that he can fit it adequately with a straight line, and that the spectral features are not statistically significant. Others point out that the fitted model contains roughly as many free parameters as data points. Meanwhile, a team led by Rafael Luque reports that they can fit the spectrum without invoking DMS or DMDS, and suggest that observations of another 25 transits of K2-18b would be needed to properly settle the matter.

There are several distinct questions here: Are the details of the data processing sufficiently understood? (perhaps, but not certainly); are the relevant spectral features statistically significant? (that’s borderline);  and, if the features are indeed real, are they properly interpreted as DMS? (theorists can usually think of alternative possibilities). Perhaps a fourth question is whether there are abiotic mechanisms for producing DMS.

This is science at the cutting edge (and Madhusudhan has been among those emphasizing the lack of certainty, though the doubts have not always been in news stories), and so the only real answer to these questions is that things are currently unclear. This is a fast-moving area of astrophysics and we’ll know a lot more in a few years.

Sean Carroll on the weirdness of quantum physics

February 5, 2025 • 11:45 am

Although I’ve read quite a few books on quantum mechanics—popular books, not books intended for physicists—I still don’t understand it.  That is, I can understand the history, the controversies and some of the phenomena, as well as the various interpretations of quantum mechanics. But when it comes to stuff like entanglement, I’m baffled—not just by its existence, but what it really means physically and how it could be possible.

Sean Carroll (the physicist) has just published a paper in Nature that is about as clear an explanation of the weirdness of quantum mechanics as I can imagine.  I still don’t understand entanglement, but Carroll does point out why people like me have difficulty grasping some of the concepts and predictions.

Since, as Carroll notes, Heisenberg “first put forward a comprehensive version of quantum mechanics” in 1925, it is in one sense the 100th anniversary of quantum theory:

Click below to read for free:

I’ll give a few quotes under headings that I’ve made up:

Why quantum mechanics is qualitatively different from classical mechanics. 

The failure of the classical paradigm can be traced to a single, provocative concept: measurement. The importance of the idea and practice of measurement has been acknowledged by working scientists as long as there have been working scientists. But in pre-quantum theories, the basic concept was taken for granted. Whatever physically real quantities a theory postulated were assumed to have some specific values in any particular situation. If you wanted to, you could go and measure them. If you were a sloppy experimentalist, you might have significant measurement errors, or disturb the system while measuring it, but these weren’t ineluctable features of physics itself. By trying harder, you could measure things as delicately and precisely as you wished, at least as far as the laws of physics were concerned.

Quantum mechanics tells a very different story. Whereas in classical physics, a particle such as an electron has a real, objective position and momentum at any given moment, in quantum mechanics, those quantities don’t, in general, ‘exist’ in any objective way before that measurement. Position and momentum are things that can be observed, but they are not pre-existing facts. That is quite a distinction. The most vivid implication of this situation is Heisenberg’s uncertainty principle, introduced in 1927, which says that there is no state an electron can be in for which we can perfectly predict both its position and its momentum ahead of time.

On entanglement.

The appearance of indeterminism is often depicted as their [people like Einstein and Schrödinger’s] major objection to quantum theory — “God doesn’t play dice with the Universe”, in Einstein’s memorable phrase. But the real worries ran deeper. Einstein in particular cared about locality, the idea that the world consists of things existing at specific locations in space-time, interacting directly with nearby things. He was also concerned about realism, the idea that the concepts in physics map onto truly existing features of the world, rather than being mere calculational conveniences.

Einstein’s sharpest critique appeared in the famous EPR paper of 1935 — named after him and his co-authors Boris Podolsky and Nathan Rosen — with the title ‘can quantum-mechanical description of physical reality be considered complete?’. The authors answered this question in the negative, on the basis of a crucial quantum phenomenon they highlighted that became known as entanglement.

If we have a single particle, the wavefunction assigns a number to every possible position it might have. According to Born’s rule, the probability of observing that position is the square of the number. But if we have two particles, we don’t have two wavefunctions; quantum mechanics gives a single number to every possible simultaneous configuration of the two-particle system. As we consider larger and larger systems, they continue to be described by a single wavefunction, all the way up to the wavefunction of the entire Universe.

As a result, the probability of observing one particle to be somewhere can depend on where we observe another particle to be, and this remains true no matter how far apart they are. The EPR analysis shows that we could have one particle here on Earth and another on a planet light years away, and our prediction for what we would measure about the faraway particle could be ‘immediately’ affected by what we measure about the nearby particle.

The scare quotes serve to remind us that, according to the special theory of relativity, even the concept of ‘at the same time’ isn’t well defined for points far apart in space, as Einstein knew better than anyone. Entanglement seems to go against the precepts of special relativity by implying that information travels faster than light — how else can the distant particle ‘know’ that we have just performed a measurement?

Yes, I know that this cannot be understood in terms of everyday observation, but what I fail to understand—and perhaps some reader can explain this to me—is exactly what properties of a particle can be affected by ascertaining properties of another particle light years away.

I’ll leave you to read the various interpretations of quantum theory, the most trenchant involving whether it actually represents physical reality or is merely a theory meant to explain experimental results.  I’m not sure where Carroll fits on this spectrum, but I do see that while he describes another interpretation, the “Everttian or many-worlds interpretation,” I thought that Carroll used to favor this explanatin, which of course is  deeply, deeply, weird, creating a new but unobservable universe each time an observer measures something. His summary of the state of the field is this:

So, physicists don’t agree on what precisely a measurement is, whether wavefunctions represent physical reality, whether there are physical variables in addition to the wavefunction or whether the wavefunction always obeys the Schrödinger equation. Despite all this, modern quantum mechanics has given us some of the most precisely tested predictions in all of science, with agreement between theory and experiment stretching to many decimal places.

The big remaining problem. If you read even a bit about quantum physics, you’ll know this:

Then, there is the largest problem of all: the difficulty of constructing a fundamental quantum theory of gravity and curved space-time. Most researchers in the field imagine that quantum mechanics itself does not need any modification; we simply need to work out how to fit curved space-time into the story in a consistent way. But we seem to be far away from this goal.

What good is quantum mechanics? But of course quantum mechanics, even if not comprehensible by the standards of everyday experience, has been immensely useful, for we’ve long known that its predictions match observations about as closely as any theory can. Here are the benefits:

Meanwhile, the myriad manifestations of quantum theory continue to find application in an increasing number of relatively down-to-Earth technologies. Quantum chemistry is opening avenues in the design of advanced pharmaceuticals, exotic materials and energy storage. Quantum metrology and sensing are enabling measurements of physical quantities with unprecedented precision, up to and including the detection of the tiny rocking of a pendulum caused by a passing gravitational wave generated by black holes one billion light-years away. And of course, quantum computers hold out the promise of performing certain calculations at speeds that would be impossible if the world ran by classical principles.

And don’t ask me what “quantum chemistry” is, as I know it not.

These are just small excerpts. Go read about the theory in its centenary year.