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From the cost of childcare to the housing crisis, there’s no shortage of explanations for the dramatic global fall in the number of babies being born. These analyses, though, are all missing something, says cognitive and evolutionary anthropologist Paula Sheppard

The microbes that live in our mouth and gut may influence whether an allergic reaction to peanuts is mild or life-threatening, and could be harnessed to ward off a severe attack

Today we have some singletons, doubletons, and tripletons from readers: that is, miscellaneous photos. The IDs and captions are indented, and you can click on the photos to enlarge them.

From reader Jay, a photo from St. Augustine beach, Florida:

This photo shows two terns (possibly Royal Terns, Thalasseus maximus), in front of four Black Skimmers (Rynchops niger).

From Keira McKenzie:

These photos were taken on a warm afternoon in Hyde Park [Sydney, Australia], sitting beneath the plane trees at the eastern end of the park.

Here you have Australian White Ibis (Threskiornis molucca,  commonly referred to as bin chickens here—which is a bit rude. In the second picture it’s with an Australian wood duck (Threskiornis molucca; there is quite the family here in all their regimental delight), both birds roosting on the island in the eastern pond in the park. While most of the undergrowth was cleared, these birds still manage to find somewhere to roost. The ibis lost their favourite tree in the clearing process, but they have found others. The wood ducks seem happy as well and I love watching the family being marshalled for the march up to the lawns to either graze or look for beetles or whatever. When they come back to the ponds, they fly in a ragged formation careless of persons what might be sitting there chatting and drinking coffee!

And the egret: it’s a Great Egret, either Ardea alba (the western Australian one) or the equally common Ardea modesta: the Eastern Great Egret (subspecies modesta) . The reason I can’t decide is their are supposed to have black legs, but my photos all have them having yellowish legs which doesn’t come up in any descriptions.

I’ve added a pic of the little Baba Yaga in her outside tiger pen just to make you smile (she is currently yelling at me to come to bed!)

And Daniel Baleckaitis, who works for both our department and Organismal Biology and Anatomy, sent three mallard pictures (Anas platyrhynchos)—taken in Botany Pond! I don’t know the ducks but the pictures are great (and clearly taken a few years back when the pond was full of vegetation):

Ducks in action:

Ever since physicist Freeman Dyson first proposed the concept in 1960, the “Dyson sphere” has been the holy grail of techno-signature hunters. A highly advanced civilization could build a “sphere” (or, in our more modern understanding, a “swarm” of smaller components) around their host star to harvest its entire energy output. We know, in theory at least, that such a swarm could exist - but what would it actually look like if we were able to observe one? A new paper available in pre-print on arXiv, and soon to be published in Universe from Amirnezam Amiri of the University of Arkansas digs into that question - and in the process discloses the types of stars that are the most likely to find them around.

A famously resilient bacterium may be tough enough to survive one of the most violent events imaginable on Mars. In laboratory experiments designed to mimic the crushing shock of a massive asteroid impact, researchers squeezed Deinococcus radiodurans between steel plates and blasted it with pressures reaching 3 GPa (30,000 times atmospheric pressure). Even under these extreme conditions, a significant portion of the microbes survived.

Astronomers using the James Webb Space Telescope have spotted the most distant “jellyfish galaxy” ever seen — a cosmic oddity streaming long, tentacle-like trails of gas and newborn stars as it speeds through a dense galaxy cluster. The galaxy appears as it was 8.5 billion years ago, revealing that the early universe may have been far more violent than scientists expected.

Researchers at the University of Basel and the ETH in Zurich have succeeded in changing the polarity of a special ferromagnet using a laser beam. In the future, this method could be used to create adaptable electronic circuits with light.

Researchers at the University of Basel and the ETH in Zurich have succeeded in changing the polarity of a special ferromagnet using a laser beam. In the future, this method could be used to create adaptable electronic circuits with light.

Fusion energy may be one of the most promising clean power sources of the future—but only if scientists can precisely measure the extreme, fast-moving plasmas that make it possible. A new U.S. Department of Energy–sponsored report urges major investment in advanced diagnostic tools—the high-tech “sensors” that track plasma temperature, density, and behavior inside fusion systems. Bringing together 70 experts from universities, national labs, and private industry, the workshop identified seven priority areas ranging from burning plasma to full-scale pilot plants.

The US and Iran are trading blows in the Gulf with a simple drone that costs as little as $50,000 to make. But why is a slow, cheap and relatively primitive drone seeing use in 2026 alongside hypersonic missiles and stealth jets?

The science writer delves into the vast subject of consciousness in his new book A World Appears – and draws some surprising conclusions, finds Grace Wade

This secretive device has been promising to deliver clean, free energy for more than 15 years — but so far nobody's been allowed to examine it.

Learn about your ad choices: dovetail.prx.org/ad-choices

Shaped by a different biology or culture, other intelligent civilisations – if they’re out there – might understand the universe in a completely different way than we do. Physicist Daniel Whiteson explores what that could tell us about physics and ourselves

Bad medicine, bad laws, bad choice

The post Legislative Alchemy: “Naturopathic Doctor” licensing is bad medicine for Florida first appeared on Science-Based Medicine.

Drones aren't yet licensed to carry passengers, but some may already be airlifting wounded personnel off the battlefield and could be employed for smuggling people

Researchers in Munich have used the Large Binocular Telescope in Arizona to capture five images of one and the same supernova in a single picture. The gravity of two foreground galaxies has deflected the light from a supernova far in the background along different paths to Earth.

The question of whether or not we have free will has been pondered by philosophers, psychologists, theologians, neuroscientists, and by many of us in our own conversations and thoughts. Nearly two thousand years ago, the Stoic philosopher Epictetus declared, “You may fetter my leg; but not Zeus himself can get the better of my free will.”1 But Epictetus also believed in a deterministic world where each event is determined by preceding causes. How can this apparent contradiction be resolved?

In the 1940s, Bertrand Russel saw no reason that human volitions would not also be determined in the same way that inanimate processes are determined. Further, he saw the determined nature of volitions as incompatible with a person being the true source of his own actions. Russell supposed that an evil scientist could, by use of psychoactive drugs, manipulate a person to perform certain actions. And this hypothetical manipulation did not seem to Russell so different from normal life, where people are manipulated to do what they do by natural causes outside their own control.2

Fifty years after Russell published his critique of the Stoic notion of free will, several other philosophers made the same argument.3, 4, 5 Today, the continued quandary contributes to a sustained lack of consensus on free will. According to surveys, most people—including most philosophers—believe in some form of free will, most under the rubric of compatibilism.6, 7 Novelist and Nobel Laureate Isaac Bashevis Singer summed up the dilemma, “We must believe in free will, we have no choice.” 

However, the debate still rages in the world of academic philosophy, in a broader audience reached by podcasts and popular books written by scientists, and among readers of Skeptic. Here I will try to convince you that free will is real and not an illusion. I’ll argue that far from being exemplars of rationality and skepticism, the main arguments against free will make unjustifiable logical leaps and are naïve in the light of cutting-edge scientific findings. 

Throughout the philosophical literature,8 resolving the question of whether or not we have free will has often revolved around two criteria for free will: 

1. We must be the true sources of our own actions. 
2. We must have the ability to do otherwise. 

I argue that humans meet both criteria through two concepts: scale and undecidability. 

Scale and the True Sources of Our Actions 

In an article in The Journal of Mind and Behavior,9 I argued that many of our actions are caused by our wills; that is, by our conscious desires and intentions. This is not disputed by most (what I’ll term) free will deniers. They more often dispute that our wills are free, not that we have wills and that our actions often follow from our wills. Sam Harris, one such determinist with a large general audience, has said that the subjectively felt intention to act is the proximate cause of acting. Harris makes the same basic claim as renowned scientist Francis Crick,10 philosophers such as Bertrand Russell11 and Derk Pereboom,12 and many others. They claim that in addition to the proximate cause (the will), our actions have ultimate causes lurking behind them that are the relevant causes to consider when judging whether or not our wills are free. The ultimate causes beyond and beneath the surface of our wills, they argue, make them unfree. What are these ultimate causes? Harris identifies genetics and environmental influences as “the only things that contrive to produce” his particular will.13 Molecules beyond DNA have also been offered as ultimate causes of our decisions. Biologist Jerry Coyne argued that, “Our brains are made of molecules; those molecules must obey the laws of physics; our decisions derive from brain activity.”14 Robert Sapolsky, a prominent neuroendocrinologist, is publishing a book this year, detailing many such mechanisms that, it is claimed, obviate the role of willed choices.15

My mind does not exist as a molecule nor as a historical epoch, nor as a socioeconomic class. Yet my mind does exist.

What’s wrong with this line of reasoning? Consider the following question as an analogy: Are apples red? Suppose we all agree that apples have color. The question is whether the color is red or non-red. To answer the question, determinists would look beyond the proximate color of the apple. Realizing that the apple is nothing but atoms, they would examine many of the carbon atoms on the surface of the apple. They find that not a single carbon atom is red. Since none of the atoms are red, and the apple is nothing but atoms, they would conclude that the apple can’t be red. The error is that though they agree the apple has a color, they try to examine the nature of the color at a scale (a carbon atom is smaller than the wavelength of red light) where color is incoherent. The fact that they found no redness at that scale shouldn’t lead them to conclude anything about the color of the apple. 

Likewise, the fact that determinists find no personal authorship or freedom in the actions of molecules shouldn’t lead them to conclude anything about the nature of the will. We agree that we have wills, that we have subjectively experienced intentions that influence our actions. The question is whether our will is free or unfree. To look at molecules for the answer is a scale mistake. DNA and neurotransmitters observed at the molecular scale exhibit no will whatsoever. With that knowledge, is it compelling that they exhibit no free will? No. That should tell us that determinists are looking at the wrong scale to find answers about the will, just as looking for answers about redness at a scale where color is not meaningful. 

The right scale for finding answers to the question of apple redness is the apple scale, not the atom scale. The right scale for finding answers to the question of freedom of the will is the agent scale, not the molecule scale. Searching the molecule scale is just one example of this error. There are many other wrong scales where a confused determinist might look for answers about the will. He or she may zoom out temporally into an irrelevant timescale, including the time before the will in question existed. In the above analogy, this would be like conceptualizing the apple as merely a step in a process of agricultural industry. Since agricultural industry is not red, should we conclude that the apple is not red? The question about the will can only find its answers from a scale where the will exists as a will. Expanding the timescale to include the time before the person was born renders the question incoherent. 

If we keep our analysis in the scale where the individual agent exists, not zooming too far in nor too far out in space, time, or level of organization, then the primary and ultimate cause of my actions is me. The will emerges from the complex interactions of many small parts. It’s literally not true to say that it’s caused by any particular small part. It is caused by many small parts, but only when taken together all at once. And that’s the same thing as the whole person. So my thoughts and actions are deterministically caused by me. The molecules of which my brain is made are simply irrelevant to this fact. So I am the true source of my own actions, and there are no other “ultimate” causes. My mind does not exist as a molecule nor as a historical epoch, nor as a socioeconomic class. Yet my mind does exist. René Descartes’ “I think therefore I am” convinces me of this.16 In order to claim that my choices are really caused by a molecule or a historical epoch, one must refer to the dynamics of a scale where I (that is, my mind) cannot be found. Eliminating the mind from the analysis is not a valid way to answer a question about the mind. 

The Ability to Do Otherwise 

There is a temporal asymmetry in the question of whether I could have done otherwise. In the question’s typical form, it is backward-looking. It asks about what could have been in the past, and, at first, it seems like a coherent question. I did one thing yesterday, and we wonder if I could have done something else. But what if we wanted to figure out whether or not I’ll have free will tomorrow? From that temporal angle, the question of the ability to do otherwise stops making sense. In a forward-looking sense, the question becomes manifestly nonsensical. Can I do otherwise in the future? Otherwise? Other than what? Other than the thing I will do? The question stipulates that I will do a certain thing, and simultaneously asks whether or not I can avoid doing that thing. The stipulation contained within the question makes the answer trivial. No, of course I can not do something other than the thing I will do. In order for the question to have any significance in the forward-looking tense, it must be modified. The question can not directly stipulate that I will do a certain thing. The question must ask whether or not I can do something other than what I’m expectedto do, not other than what I will do. 

The will emerges from the complex interactions of many small parts. It’s literally not true to say that it’s caused by any particular small part.

Human choice is temporally asymmetric and must be analyzed as such. This point could be missed without properly situating our analysis at the correct scale. An inappropriate focus on the dynamics of little particles could obscure the truth. The laws of physics that describe or govern the interactions of particles do not specify a direction of time. If we could watch a video of two protons colliding, we would have no way to know whether the video was being played forward or in reverse. This is called time reversal symmetry. This symmetry holds true in a wide variety of particle interactions.17 Time appears asymmetric only at scales where emergent phenomena transpire. Large collections of particles obey the second law of thermodynamics, which is not time reversal invariant. As astrophysicist Matt O’Dowd put it, “Zoom in to individual particle interactions and you see the perfect reversibility of the laws of physics. But zoom out, and time’s arrow emerges.”18 A consideration of scale leads to a recognition of temporal asymmetry in human choice. 

In analyzing the ability to do otherwise, we should consider only a forward-looking ability because choices, by their nature, are forward-looking. We don’t deliberate or make choices about the past. Choices are always about something, and those objects of choice always lie in the future, thus choices are always forward-looking. At the time when a choice is actually made, there is as of yet no “what” as in “Could have done other than what?” I have not already made the choice, so there is no established action to have done otherwise. There can only be expectation of what I will do. If my actions are in principle perfectly predictable, then I do not have the ability to do otherwise in a forward-looking sense. If my choices are in principle not predictable, given total knowledge of the present world, then I do have the ability to do otherwise in a forward-looking sense, which is the only sense that makes any sense. Given the different dynamics found at different scales, the ability to do otherwise needs to be understood as temporally asymmetric; that is, as always forward-looking; as the ability to do something which is in principle not predictable. We do have that ability, and it derives from our self-referential nature. 

Self-Reference and Undecidability 

The fact that I am the relevant cause of my own actions comes with another important implication: I am a causally self-referencing entity. If a molecule were the relevant cause of my action, this would not be true in the same way. The molecule has no capacity for self-reflection, but I do. I can ask myself, “What will I do? What could I do? What should I do? What do I want to do? What would I do if I wanted to do X and should do Y?” Self-referential questions like these affect the choices that I make; and those choices change the self-referential questions that I ask. 

At the relevant scale, self-reference is causally important. I am a system which analyzes its own inputs, character, and potential outputs; generates new outputs based on those analyses; and feeds those new outputs back into itself as inputs which affect the outputs, which affect the system’s character. I am an output of and an input for my own processing. Framing the human self-referential nature in this way brings us to the concept of undecidability. 

A system that exhibits undecidable dynamics cannot be predicted, given complete knowledge of its present state. Computer scientists and mathematicians have proven that this fundamental unpredictability shows up in some algorithmic computations, mathematical systems, and dynamical systems (including physical systems).19 Though an unpredictable dynamical system may evoke the concept of chaos, undecidability is not chaos; it is a different sort of unpredictability. IBM research scientist Charles H. Bennett makes the difference clear: 

For a dynamical system to be chaotic means that it exponentially amplifies ignorance of its initial condition; for it to be undecidable means that essential aspects of its long-term behaviour—such as whether a trajectory ever enters a certain region—though determined, are unpredictable even from total knowledge of the initial condition.20

If a system exhibits undecidability, then it is unpredictable even given total knowledge of all of its constituent parts. Undecidability makes deterministic systems fundamentally unpredictable in principle, not as a result of merely lacking precise measurements. If humans can exhibit undecidability, then we meet the second main criterion for free will: the forward-looking ability to do otherwise. Scientists recently made such an argument feasible by explicating what features of a system give rise to undecidable dynamics. In 2019, Mikhail Prokopenko and his colleagues conducted a comparative formal analysis of recursive mathematical systems, Turing machines, and cellular automata. They come to a clear conclusion: 

As we have shown, the capacity to generate undecidable dynamics is based upon three underlying factors: (1) the program-data duality; (2) the potential to access an infinite computational medium; and (3) the ability to implement negation.21

If humans do have these three properties, then we meet the criteria for undecidable dynamics, which means we can take actions that are fundamentally unpredictable, which means we have the ability to do otherwise in a forward-looking sense, which means we have free will. 

First, consider program-data duality, which in this context is the ability for self-reference. The word “duality” simply refers to the typical distinction between program and data with which we are all familiar. A human at time 1 has a certain overall state of mind, coinciding with a certain overall physical state. The state at time 1 is a program, in that it entails implicit rules about what the system would do, given certain types of data. The streams of perceptions taken in at time 2 are data, which get processed according to the implicit rules. In addition to processing basic sense data, this duality allows for a program (or implicit set of rules encoded in the state of a human) to process other programs as data. For example, a human can process ideas, hypothetical scenarios, mathematical operations, and representations of the self as data (thus self-reference). 

The question about the will can only find its answers from a scale where the will exists as a will. 

The next requirement for undecidability is the potential to access an infinite computational medium. The computational medium is the substrate on which the state of the system is represented. In a computer, the computational medium would be the memory and storage. The set of all possible states of the system is called the state-space. For example, the state space of a computer would be the set of all possible configurations of its memory and storage. If we knew that a certain system had an infinite state-space, we could infer that the system has access to an infinite computational medium. 

It can be informally proven that humans have an infinite state-space. How many different thoughts is it possible for a human to have? That question includes sub-questions, such as how many things is it possible for a human to see? The state of your visual perception is one small part of your overall state. Think of the number 74. Now think of the number 74 with your eyes closed. Those two occasions of thinking of 74 occupied two very different points in your state-space because of the difference in visual perception. 

To roughly estimate how many overall states are possible while thinking of 74, we would need to do something like multiply the number of possible visual perceptions by the number of possible auditory perceptions by the number of possible sensations of heat and cold by the number of possible gradations of feeling sadness or happiness, and so on. Also, you may think of 74 while remembering, for example, the time you thought of 106 or 107. And the next time you think of 74, that will be yet another point in your state-space, since you’ll recall that you’ve thought of 74 before. There may be an infinite number of possible states in which you might think of 74. And there are many conceivable numbers other than 74, and many things to think about other than numbers. 

An obvious objection might be that a human and his brain are physically finite. In what sense can an organ that fits inside a skull be infinite? As a starting point, consider the 100 billion neurons that make up the brain. As a simplification, a neuron can be considered to be “firing” or “not firing.” So a simplified brain has 100 billion binary cells. Such an array of cells could instantiate 2^100,000,000,000 distinct patterns of on-or-off activation. That’s a big number. For comparison, there are estimated to be roughly 10^80 atoms in the observable universe.22 The number of atoms in the universe is an infinitesimally small number compared to the number of activation patterns possible in a simplified brain. And what about a real brain? A real brain is made of neurons which are not simply on or off. Some neurons show gradations in voltage and neurotransmitter release, meaning that they have many possible states between “on” and “off.”23

Undecidability makes deterministic systems fundamentally unpredictable in principle, not as a result of merely lacking precise measurements.

Besides neurons, there are many other variables in the brain that are not captured by the simplified on/off variable. Each neuron can vary in the amount of neurotransmitter in its vesicles ready for release, and the state of the receptors on its soma and dendrites (that is, to what degree they’re blocked by other molecules). There can also be variation in the amount of neurotransmitter that is floating free at any moment in the space between any two neurons. There are minute variables that will likely never be measured yet do, theoretically, make a causal difference. For example, in what spatial direction is each neurotransmitter molecule oriented? A neurotransmitter molecule must fit into a receptor in order to carry on a signal. For the molecule to fit, it must be facing a certain direction relative to the receptor. So the spatial orientation of the molecule before binding must have some nonzero effect on the binding affinity. How many different patterns of analog spatial orientation might trillions of neurotransmitter molecules be capable of? That alone may be infinite. The variable of “firing” or “not firing” does not capture any of these variables. So the actual number of possible overall brain states is some large exponent greater than 2^100,000,000,000 which is a large exponent greater than the number of atoms in the universe. 

Whether the human state-space is technically infinite or merely practically infinite (larger than any other number computed for any purpose in all of science), it will not be exhausted in the meager 100 years of a human lifespan. This means that the self-referential loops of processing do not need to stop at any predetermined iteration or level of abstraction. So for the purpose of analyzing the choices of a human, the state-space and computational medium are functionally infinite. 

The last element required for undecidability is the ability to implement negation. Negation in this context refers to the ability of a logical system to produce an output which is exactly contrary to the processing which led to the output. It is equivalent to the liar paradox, which is exemplified in a statement such as “everything I say is a lie,” or more formally, “this statement is unprovable.” The liar paradox is a self-referential statement, which can not be judged to be true or false without a contradiction. Self-reference is fundamental to this paradox because the statement refers to its own validity. If humans can implement this paradoxical logic into their thinking, then humans meet this requirement for producing undecidability. The fact that humans came up with the liar paradox thousands of years ago is evidence that humans can perform the logical operation of negation. 

Conclusion 

All three factors underlying the capacity to generate undecidable dynamics are present in humans. First, we exhibit program-data duality when we process ideas, hypothetical scenarios, mathematical operations, and representations of ourselves as objects of thought. Next, we have the potential to access an infinite computational medium. This is demonstrated by the fact that we can think of any one of an infinite number of objects of thought, which implies an infinite state-space, which implies an infinite computational medium. Finally, we have the ability to implement negation, demonstrated by the inception of the liar paradox in the minds of humans. If these three elements are sufficient to generate undecidable dynamics, then humans are capable of generating undecidable dynamics, which means we cannot be accurately predicted. And that means we have the ability to do otherwise in the forward-looking sense. 

Figure 1. Relational map of concepts. The truth of each concept supports the truth of the concepts downstream from it. This diagram illustrates how the concepts described throughout this article contribute to the overall reality of free will.

Figure 1 shows the relationships between the concepts discussed in this article. An understanding of the human agent at the scale where conscious humans actually exist leads to recognition of the self as the source of one’s actions, recognition of the relevance of temporal asymmetry to human choice, and recognition of self-reference as causally relevant to human actions. Self-reference, in combination with access to an infinite computational medium and the ability to implement negation results in undecidable dynamics. This entails the ability to do otherwise in the forward-looking sense, which is the only sense that makes any sense when temporal asymmetry is taken into account. The resulting total picture is that we (humans) meet two criteria for real free will: the forward-looking ability to do otherwise and being the source of one’s own actions. 

Viewing human agents as whole humans instead of as molecules makes it clear that humans are the cause of their own actions, and also leads to a focus on the human features such as self-reference, that generate undecidable dynamics. The Stoic philosopher Epictetus was right. Neither Zeus, Bertrand Russell, nor the scientists recapitulating the latter’s argument 77 years later can diminish our free wills.

Satellite imaging is increasingly important to every field from crop monitoring to poverty reduction. So it’s no surprise that there have been more and more satellites launched to try to meet that growing demand. But with more satellites comes more risk for collision - and the debris field that comes after the collision. A new paper in Advanced in Space Research from John Mackintosh and his co-authors at the University of Manchester looks at how we might use mission design to mitigate some of the hazards of increasing the number of satellites even more

Star dust is at the root of everything that exists, and is produced in large quantities around Wolf-Rayet binaries. But there are some puzzling observations of dust grain sizes that require explanations. New research shows why different observations have found different dust grain sizes.

This morning a friend who works in the department office called me and said “there are two ducks in the pond.” I instantly knew that this would be a male/female pair of mallards scoping out the pond as a potential nesting and rearing site. Within one minute I grabbed my camera and my container of adult duck food (I saved it from last year; I have plenty and it’s still good), and ran down to the pond.

Sure enough, there was a pair of mallards at the far (south) end.  Moreover, then swam near me when I whistled, though they didn’t come right up to me. This suggests that these are the mallards knew me, though, based on bill patterns in the hen, I don’t think they are Esther and Mordecai from last year.

Those ducks were named because they arrived on the Jewish holiday of Purim, and, sure enough, that holiday is tomorrow.  These are again Jewish ducks and will have to be named accordingly.

I am so happy. There is no guarantee they’ll stay, but food is thin on the pond, and I am making sure they know it is a place to get a nice meal. After filling their tummies, they retired back to the south end for a rest.

Photos. First, the pair (name suggestions welcome, especially Jewish-themed names—but not Mordecai and Esther):

The hen:

The hen eating (out of focus). They were hungry!

The drake, dripping water from his bill after having eating a food pellet (I give them only the best):

The hen’s bill:

This is Esther from last year. The bill pattern of today’s hen is clearly different, so the hen we have now is not Esther. But there’s no guarantee that this one will breed here (remember, Esther was our first ground-nesting female). Note that today’s duck lacks Esther’s black markings on the top and tip of her bill, and those should have remained over a year.

Stay tuned for 2026 Duck Adventures.