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The qualities and behavior of dark matter, the invisible 'glue' of the universe, continue to be shrouded in mystery. Though galaxies are mostly made of dark matter, understanding how it is distributed within a galaxy offers clues to what this substance is, and how it's relevant to a galaxy's evolution.

On June 11, there was a special issue of Nature with several articles devoted to sex and gender.  In general the two terms were conflated (often used in the phrase “sex and gender”), and most of the issue was an example of a scientific journal being ideologically captured by gender activists. For example, on this site I criticized one of the articles, “Beyond the trans/cis binary: introducing new terms will enrich gender research“, which, as so often happens in science journals, introduces new and “inclusive” terms that, in the end, turn out to be confusing and useless. As I wrote at the time

Nowhere is this more obvious than the essay below, which is not only science-free, but wholly about semantics.  And useless semantics to boot, at least to my eye.  The whole purpose is to introduce a new term, “gender modality,” which, the authors say, will be of great help to people who don’t identify as “male” or “female”, and keep them from being “erased”.  The thing is, the other terms that fall under this rubric already exist, so grouping them as aspects of “gender modality,” a term whose definition is confusing, adds nothing to any social discourse that I can see.

To be sure, a couple of the articles emphasized that in biomedical studies one should be aware of separating males from females when that’s relevant. But if researchers don’t know that by now, I feel sorry for them. And one of the article that scientists should also take gender into account in biomedical research, something that baffles me.  To wit (my emphasis)

For Alzheimer’s and many other diseases that are common causes of death, including cardiovascular diseases, cancer, chronic respiratory conditions and diabetes, a person’s sex and gender can influence their risk of developing the disease, how quickly and accurately they are diagnosed, what treatment they receive and how they fare.

If you’re a tomboy (a female with male-like behaviors), which one can consider a gender identity, does this really affect your chances of getting cancer? If so, I don’t know about it. In fact, I’m not aware that gender can influence any diseases, and no references are given, but I doubt it. (Gender may be important in psychological maladies like gender dysphoria, but that’s not what the authors mean.) This paper is one example of sex and gender, two very different things, being lumped together.  Do not fall into that semantic conflation!

Perhaps it was this mixing up of sex and gender that prompted two researchers to write this newly-published letter in the journal: 

In the main I agree with them, but their arguments don’t really avoid the ‘sex binary,” which is simply the observation that there are two sexes: reproductive systems that are “male” and “female”, with the definitions based on gamete size and mobility, as well as the developmental apparatus that produces eggs and sperm. There are only those two types of gametes, and that’s the case for all animals and nearly all vascular plants.

In animals, which of course include humans, sex is as close to binary as you can come, with only 0.018% of individuals being neither male nor female, but intersex. Yes, some species can change sex, as in clownfish, and some can be hermaphroditic, an individual that is both male and femal at the same time.  But even functional animal (or plant) hermaphrodites still produce only the two types of gametes. And intersex individuals in humans are not a “third sex”, because they don’t produce a third type of gamete.  (In our species, there has never been a case of a hermaphrodite producing both sperm and eggs.)  As Griffiths and Davies wrote in 2020:

The biological definition of sex is not based on an essential quality that every organism is born with, but on two different strategies that organisms use to propagate their genes.

The Griffiths and Davis paper, by the way, is a very good resource for understanding biological sex, though I think it gives away too much to those who claim that they are really members of their non-natal sex.

As for pipefish and seahorses gestating eggs (true), that is a difference in sex ROLES, not sex itself. The same goes for female hyenas that have penis-like structures: they still produce eggs and produce offspring (through that penis-like structure!), but they remain female.  The sex/gamete binary is real, and it’s important because gamete size differences, universal among animals and nearly all plants, produce a whole world of evolutionary differences, the most important being sexual selection based on differences in reproductive investment. And that helps us understand the evolution of genetically-based differences in morphology and behavior between males and females. (Sexual selection also operates in plants.)  The biological definition of sex is important because it’s both universal and evolutionarily enlightening, similar to the biological definition of “species” (see Chapter 1 of Speciation by Coyne and Orr).

Remember, there’s a difference between the DEFINITION of sex (given above) and the ASCERTAINMENT of sex, with the latter made using secondary sexual traits like genitalia. Importantly, the traits used for ascertainment, which include chromosome complement, aren’t always a perfect correlate with biological sex. Still, those traits are used to ASCERTAIN sex, not to “assign” it, as in the ludicrous phrase “sex assigned at birth” or worse, “gender assigned at birth”. Those phrases should be completely eliminated because they’re a sop to the ignorant.  Gender, which involves how a person identifies vis-à-vis sex, and can involve a mixture of male and female traits, non-natal traits, or even nonhuman traits, is completely different from biological sex, and cannot be assigned at birth.

I sent my comments to Matthew, who added this:

The key point, of course, is that the vast majority of people are only interested in humans, where we cannot switch the kind of gametes we produce. There are no cases of this ever recorded, nor will there ever be. People can now do all sorts of things to alter their secondary sex characteristics, and – much more easily – to change their sex roles, but they can’t change the gametes they are born to produce, nor, in the case of people with disorders of sexual development, change their particular fundamental sex characteristics.

And although some species can change sex, either naturally (clownfish), or by being manipulated (crabs with parasites), they are extremely rare and I don’t know of any mammals that do this.

QED

(h/t to Matthew for finding the letter and for his comments)

Adding a polymer-alcohol mixture to menstrual pads causes blood to solidify, rather than being absorbed, which could ward off leaks

You might think I’m about to tell a joke. But no, not me. This is serious physics, folks!

Suppose a particle falls into a hole, and, as in a nightmare (or as in a certain 1970s movie featuring light sabers), the walls of the hole start closing in. The particle will just stay there, awaiting the end. But if the same thing happens to a wavicle, the outcome is very different. Like a magician, the wavicle will escape!

Today I’ll explain why.

As I described last time, stationary particles, waves and wavicles differ in their basic properties.

stationary particlestanding wavestanding waviclelocationdefiniteindefiniteindefiniteenergydefinite,
container-independentadjustabledefinite,
fixed by frequencyfrequencynonecontainer-dependentcontainer-dependentamplitudenoneadjustablefixed by
frequency & container
A stationary particle, standing wave, and standing wavicle, placed in an identical constrained space and with the lowest possible energy that they can have, exhibit quite different properties.

Stationary particles can have a fixed position and energy. Stationary (i.e. standing) waves have a definite frequency, but variable amplitude and energy. And standing wavicles are somewhere in between, with no fixed position, but with a definite frequency and energy. Let’s explore an important consequence of these differences.

The Collapsing Well

Imagine that we place a tiny object at the bottom of a deep but wide well. Then we bring the walls of the well together, making it narrower and narrower. What happens?

A particle will just sit patiently at the bottom of the well, even as the walls close in, seemingly unaware of or unconcerned about its impending doom (Fig. 1).

Figure 1: As the walls of a well draw closer together, a particle in the well seems oblivious; it sits quietly awaiting its fate, its energy unchanging.

A wavicle, by contrast, can’t bear this situation (Fig. 2). Inevitably, as the walls approach each other, the wavicle will always leap bodily out of the well, avoiding ever being trapped.

Figure 2: As the walls of a well draw closer together, a wavicle becomes more and more active, with more and more energy; and at some point it can hop out of the well.

The only way to keep a wavicle inside a collapsing well would be to extend the walls of the well upward, making them infinitely high.

This difference between particles and wavicles has a big impact on our world, and on the atoms and subatomic “particles” out of which we are made.

Energy Between Walls

In my last post I discussed what happens to a particle located between two walls that are separated by a distance L, as in Fig. 3. If the particle has rest mass m and is stationary, it will have energy E=mc2, no matter what L is.

Figure 3: A particle sits on the ground between walls a distance L apart.

A wavicle standing between two walls is different, because the energy of the wavicle grows when L decreases, and vice versa. A wavicle of mass m will therefore have energy larger than mc2.

Figure 4: A standing wavicle sits on the ground, occupying the space between walls a distance L apart.

The energy will be just a little larger than mc2 if the distance L is long, specifically much longer than the wavicle’s “Compton wavelength” h c / m (where h, Planck’s constant, is a constant of nature, like c). But if L is much shorter than the Compton wavelength, then the wavicle’s energy can greatly exceed mc2.

Click here for a math formula showing some details.

Throughout this post I’m going to be quantitatively imprecise, keeping only those conceptual and mathematical features which are needed for the conceptual lessons. A complete mathematical treatment is possible, but I think it would be less instructive and more confusing.

Roughly speaking, the formula for the wavicle’s energy is

Notice that

• if is infinite,
• if is large, , just slightly larger than
• if is small, , much larger than

Energy in a Well

Now let’s imagine digging a hole that has a width W and a depth D, as shown in Fig. 5. Let’s first imagine the well is quite wide, so W is relatively large.

Figure 5: As in Fig. 1, a particle sits in a well of width W and depth D.

If we put a stationary particle of mass m in the well, it just sits at the bottom. How much energy does it have?

If a particle placed at ground level, outside the well, has energy E=mc2, then a particle below ground level at a depth D has energy

• ,

where g is the acceleration of objects due to the Earth’s gravity. The energy has been reduced by the lowering of the particle’s altitude; the larger is D, the greater the reduction. (This reflects the fact that in a hole of greater depth, it would take more energy to lift the particle out of the hole.) But the particle’s energy shows no dependence on W.

Suppose we instead put a stationary wavicle of mass m in a wide well. It too sits inside the well, but it’s different in detail. It vibrates as a standing wave whose length is set by W, and whose frequency f therefore also depends on W. Since a wavicle’s energy and frequency are proportional, via the Planck-Einstein quantum formula E=fh, that means its energy depends on W too.

Figure 6: As in Fig. 2, a wavicle occupies a well of width W and depth D.

Being in the well, at a reduced altitude, reduces its energy by the same factor m g D that applies for the particle. As before, the larger is D, the greater the reduction.

But the wavicle’s energy gets a boost, relative to that of the particle in the well, because the finite width of the well increases its frequency. The smaller is W, the larger the energy boost from the narrowness of the well.

Thus there is a competition between the well’s depth, which lowers the wavicle’s energy as it does the particle’s, and the well’s width, which raises the wavicle’s energy relative to the particle.

Click here for a math formula showing how this works

Specifically, inside a well of width W and depth D, its energy is approximately

So what happens, now, if the well starts collapsing and the walls close in? What do the particle and wavicle do as W decreases?

Leaping Out of the Well?

As the well becomes narrower, the particle does nothing. Its energy doesn’t depend on the width W of the well, and so the particle doesn’t care how far apart the walls are until they actually come in contact with it. The particle’s energy is always less than the mc2 energy of a particle sitting on the ground outside the hole. That means that the particle never has sufficient energy to leave the hole on its own.

The wavicle is quite another matter. As W decreases, the energy of the wavicle increases. And at some point, when W is small enough, the energy of the wavicle in the well becomes greater than the energy of the wavicle that extends outside the well.

To keep things simple, let’s imagine L to be very large, so large that when outside the well, both the particle’s and wavicle’s energy are almost exactly equal to mc2. In that context, consider Fig. 7, where I show the W-dependence of the energy of four objects:

• the wavicle and particle outside the well (blue), whose energy is independent of D and W,
• the particle in the well (orange), whose energy depends on D but not W,
• the wavicle in the well (green), whose energy depends on both D and W.

Only the last of these depends appreciably on W, which is why the blue and orange lines are straight.

When W is large (at right in the plot,) then the fact that the well is deep assures that the energy of the wavicle in the well (green) is lower than the energy of the wavicle that sits on the ground (blue), filling the whole space. That implies that the wavicle will remain within the well, just as a particle in the well would.

Figure 7: The energy E of a particle or wavicle of mass m in the presence of a well of depth D and width W. Either particle or wavicle, when located outside the well, has energy approximately mc2 (blue line.) A particle in the well has its energy reduced by mgD (orange line.) A wavicle in the well has its energy similarly reduced, but also raised by the finite width of the well (green curve.) For small enough W, the green curve lies above the blue line, and the wavicle can escape the well.

But inevitably, when W is small enough (at left in the plot,) the situation reverses! (How small exactly? It depends on details, specifically on both the mass m and the hole’s depth D.) The wavicle in the narrow well, unlike a wavicle in a wide well, has energy greater than a wavicle outside the well. That means that the wavicle in the narrow well has sufficient energy to leave the well entirely, and to become a standing wave that sits on the ground, occupying the whole region between the outer walls.

Notice this is completely general! No matter how deep we make the well, as long as the depth is finite, there is always a small enough width for which the wavicle’s escape becomes possible.

Wavicles Push Back; Particles Don’t

To say this another way, a wavicle in a narrow well has more energy than one in a wide well. Therefore, squeezing a well with a wavicle in it costs energy, whereas to squeeze a well with a mere particle inside costs none. As we shrink W, adding more and more energy to the system, there will always come a point where the wavicle will have enough energy to pop out of the hole. It’s almost as though the wavicle is springy and resists being compressed. A particle in a well, by contrast, is completely inert.

This remarkable property of wavicles, related to Heisenberg’s uncertainty principle, has enormous implications for atomic physics and subatomic physics. In my next post, we’ll see examples of these implications, ones of central importance in human existence.

———-

Aside: We can also compare wavicles with ordinary, familiar waves. We’ve seen how important it is that shortening a wavicle increases its energy. What about the waves on a guitar string? Can they, too, hop out of a hole?

A vibrating guitar string has a standing wave on it that produces sound waves at a particular frequency, heard as a particular musical note. A guitar player, by shortening the string with one finger, can make the frequency of the wave increase, which makes the musical note higher. But doing so need not increase the energy of the string’s vibration! There is no relation between energy and frequency for an ordinary wave, because the number of wavicles that makes up that wave can change. The frequency might increase, but if the number of wavicles decreases, then the energy could stay the same, or even decrease.

It’s only when the vibrating string’s standing wave consists of a single wavicle (or an unchangeable number of wavicles) that energy must be added to increase frequency.

For this same reason, a large wave in a well need not pop out of the well as its walls contract, because shrinking the well’s size, which may increase the wave’s frequency, need not increase its energy.

What was the greatest invention of human civilization? Arguably it was agriculture, which allowed for civilization itself. Prior to agriculture humans were some combination of hunters, gatherers, scavengers, and fishers. We lived off the land, which was a full-time job. Many communities had to be nomadic, to follow prey and follow the seasons. There were some permanently occupied sites, if they were in proximity to an adequate food source. Food was the ultimate limiting factor on human populations and ingenuity.

Agriculture was therefore a transformative invention, allowing people to stay in one place and develop infrastructure. It also freed up some members of the group to do things other than focus on acquiring food. It made civilization possible. How far back does agriculture go?

The consensus is that agriculture began in earnest about 12,000 years ago, in the fertile crescent that is now Iran, Iraq, Turkey and surrounding regions. Evidence for this includes the remnants of domesticated plants, and also evidence of farming and food processing. In addition there is evidence of domesticated animals, which would have been a source of labor and also an additional food source. There were also some downsides to this shift in lifestyle – relying on a narrow range of plants reduced food diversity and therefore overall nutritional quality. Living with domesticated animals, and in larger populations, also saw the rise of communicable diseases. The latter still plagues humanity. However, successful societies all figured out eventually how to farm a combination of plants that would provide adequate nutrition. You may have noticed that most cultures’ staple foods include some combination of a grain plus a legume – corn and beans, rice and lentils, for example.

It turns out, however, that agriculture likely had far deeper roots. A 2015 study details evidence for farming 23,000 years ago, on the shores of the Sea of Galilee. One of the lines of evidence was the presence of extensive weeds. This may seem counter-intuitive, but weeds thrive in cultivated and disturbed land, and so an unusual concentration of weeds is a marker for farming. There was also the presence of wild oats, wild barley, and wild emmer, in addition to tools for processing these grains and evidence of such processing. Was this a false start that eventually died off and had to be rediscovered, or was sporadic farming part of human behavior in this region for thousands of years before systematic agriculture?

It does make sense that kickstarting agriculture would be difficult. There is a bit of chicken and egg problem – you need a stable community to farm, but you need farming to have a stable community. Perhaps some communities did a little farming on the side.

A second major hurdle – what are you going to plant? I have often engaged in the thought experiment of what it would be like to try to kickstart civilization if you were suddenly transported to a prehistoric society 20 thousand or so years ago. Prior to agriculture there were no domesticated or cultivated plants. What exists in the wild is all barely edible – except for fruits, which evolved to be eaten as a bribe for seed distribution.  But even the wild version of most fruits would be considered horrible by modern standards. Only a handful of plants that humans regularly consume are close to their wild forms – such as raspberries. Most others would be unrecognizable to modern eyes.

It is incredible to think, therefore, of our ancestors planting these barely edible plants as a supplement to their diet. It would have been a lot of work for little return, although when living on the edge of starvation anything increases the chances of survival. And then, literally over thousands of years, picking and replanting seeds from incrementally better varieties slowly transformed these wild plants into modern crops. Seeds therefore became a vital commodity, and were traded far and wide. There is an unbroken connection from those first farmers at least 12,000 years ago, if not longer, to modern farming.

Up until very recently, however, farming was still a labor intensive way to get a steady supply of food. During colonial times, for example, 95% of the population was engaged in farming. That left the other 5% to essentially do everything else. But farming also allowed for huge population growth, so while 5% is a small fraction it is a massive population in absolute numbers – a population of scholars, engineers, inventors, artists, and politicians.

Today only about 2% of the population is engaged in farming, which is able to sustain a population of 8 billion people. That is the revolution of agriculture.

The post The Neolithic Revolution first appeared on NeuroLogica Blog.

Horse therapy helps people with Alzheimer's disease socialise and improves their mood to a greater extent than music therapy, which is more established for supporting people with dementia

Certain exoplanets pique scientists’ interest more than others. Some of the most interesting are those that lie in the habitable zone of their stars. However, not all of those planets would be similar to Earth – in fact, finding a planet about the size of Earth is already stretching the limits of most exoplanet-hunting telescopes. So the scientific community rejoiced when researchers at the Université de Montréal announced they found an exoplanet in the size range of the Earth. However, it appears to be almost entirely covered in water, making it more similar to a giant version of Europa, the ice-covered moon of Jupiter. 

There’s a lot to unpack in the press release describing the discovery. The exoplanet they studied is known as LHS 1140b. It’s located 48 light-years away in the constellation Cetus, making it one of the closest known exoplanets in its star’s habitable zone.

That star, LHS 1140, is only about 20% the size of our Sun, and the energy it puts out is smaller. LHS 1140b is one of two potential exoplanets orbiting it, but until now, scientists have debated whether it was a “mini-Neptune” or a “super-Earth.” If it were a “mini-Neptune,” it would be surrounded by hydrogen gas, but the researchers did not find that.

LHS 1140b has long been a center of attention for astronomers – as Anton Petrov describes here.
Credit – Anton Petrov YouTube Channel

They used “director’s discretionary time,” which means observational time directly assigned by the project’s director of the James Webb Space Telescope (JWST). They combined it with data collected from TESS, Spitzer, and Hubble. After looking closely at LHS 1140 b’s atmosphere, they saw something familiar—nitrogen. This was interesting for a few reasons. First, it ruled out the possibility of LHS 1140b being a “mini-Neptune,” as the hydrogen-rich atmosphere would have been very distinct in the data. 

Second, it is now officially the first known temperate exoplanet to have a “secondary” atmosphere – i.e., one created after the planet’s formation. Nitrogen does not naturally form part of a planet’s atmosphere at the outset and must be developed later through chemical processes. So far, no exoplanets in their star’s habitable zones have been observed with this gas in their atmosphere, though it had long been theorized since our own planet’s atmosphere is so rich in it.

But even more intriguingly, with the possibility that it was a “mini-Neptune” eliminated, it seemed LHS 1140b became a good candidate for a “super-Earth” – about 1.7 times larger than our home planet and 5.6 times its mass. However, the researchers also noticed the planet was much less dense than expected, indicating that about 10-20% of that mass could be water rather than rock.

Fraser discusses how we JWST to find exoplanets.

Having that much water could lead to several different outcomes. First, there is the possibility of LHS 1140b being a “Hycean world,” which would be entirely covered by a liquid-water ocean. This seems unlikely, as the star’s energy output doesn’t provide enough energy to keep an entire planet-sized ocean warm enough not to freeze.

This leads to the second possibility—a “snowball” world where a thick layer of snow covers the rocky interior. This is still possible, but it requires weather patterns that might be hard to discern remotely, even with JWST.

So that leaves a final possibility—an ice world, where thick sheets of ice cover the entirety of the planet’s surface. We already know of one such world a lot closer to home—Europa. It is completely covered in ice, though intriguingly, it also has a liquid ocean underneath those ice sheets. The researchers think there is a good chance a similar subsurface ocean could exist on LHS 1140b as well.

Fraser discusses how to research exoplanet atmospheres with JWST.

That would make it the first known exoplanet to have confirmed liquid water. However, the data suggested another intriguing possibility – it could be a snowball planet with a “bull’s eye ocean” at the point where the star’s heat is strongest on it. This ocean could be around 4,000 km across, about half the size of the Atlantic Ocean on Earth. Models suggest that the water temperature in the ocean could even reach 20 C, a comfortable room temperature, though a bit cold to swim in. 

However, none of these details have been confirmed yet, and doing so will require—you guessed it—more observational time. In particular, the researchers are interested in whether there is carbon dioxide in LHS 1140b’s atmosphere. A greenhouse gas could make it more likely that the planet’s overall temperature would be warm enough to make it a Hycean world rather than a snowball with one isolated ocean. 

Observing carbon dioxide in an exoplanet as far away as LHS 1140 could take years of intermittent observational time on JWST. While LHS 1140b is now definitively one of the most promising candidates for finding liquid water on a planet’s surface – and therefore be a prime candidate for finding life on an exoplanet – continued observation of that kind would have to compete with all the other worthy use cases for JWST’s time. 

For now, the researchers hope to receive more observational time, even if it isn’t enough to confirm the presence of carbon dioxide. However, eventually, there will be more and stronger planet-hunting telescopes than even the JWST. Someday, there will be enough observational time on at least one of them to confirm whether or not LHS 1140b does indeed have a liquid ocean. That day might be one of the most monumental in the history of the study of exoplanets—and maybe for humanity itself.

Learn More:
Université de Montréal – Astronomers Find Surprising Ice World in the Habitable Zone with Webb Data
Cadieux et al. – Transmission Spectroscopy of the Habitable Zone Exoplanet LHS 1140 b with JWST/NIRISS
UT – Is This The Exoplanet Where Life Will First Be Found?
UT – A New Venus-Sized World Found in the Habitable Zone of its Star

Lead Image:
Illustration of exoplanet LHS 1140 b, including a “bulls-eye ocean”.
Credit – B. Gougeon / UdeM

The post Exoplanet Could be an Enormous Version of Europa appeared first on Universe Today.

The ‘Great North American Occultation’ sees the Moon blot out Spica Saturday night.

Few events in the sky transpire as quickly as occultations. While the path of the planets may move at a leisurely pace, and the orbits of double stars may be measured in terms of a lifetime or more, occultations are swift vanishing acts.

North American observers have a chance to witness just such an event this coming weekend, when the waxing gibbous Moon passes in front of the bright first magnitude star Spica.

The Moon meets Spica Saturday night. Credit: Stellarium.

The Moon is 52% illuminated (just past 1st Quarter) when the event transpires centered around 2:31 (UT) Universal Time (10:31 PM EDT), and most of Canada down through the contiguous United States (CONUS) south into Mexico will witness the entire event; only northwesternmost Canada and Alaska will miss out. The U.S. West Coast sees the occultation occur under dusk skies, while the U.S. Eastern Seaboard and the Canada Maritimes will see the beginning of the event (ingress) underway just before moonset.

The sky on the evening of July 13th. credit: Stellarium.

The International Occultation Timing Association (IOTA) has a list of ingress/egress times for select locales inside the occultation footprint here. The Moon moves its own apparent diameter (30′ or half a degree) about once per hour, and waxing occultations are especially dramatic, as the dark edge of the Moon leads the way.

The footprint for Saturday night’s occultation. Credit Occult 4.2. Spiking to Spica

Also known as Alpha Virginis, Spica is the brightest star in the constellation Virgo and is located about 250 light-years distant. A spectroscopic binary with a companion star in a close orbit, Spica is one of the closest stars to our solar system with the potential to explode as a Type II supernova in the next few million years.

Located close to the ecliptic plane, Spica played a role in helping the ancient Greek astronomer Hipparcos to deduce the precession of the equinoxes, as a temple in Thebes built on an alignment with the star in 3200 BC had since changed position with respect to the sky.

Why Occultations

Beyond just providing a great show, occultations can reveal unseen companions and even tell us something about the nature of the target object, to include its apparent diameter.

In the current epoch, the Moon can occult three other major first magnitude stars in addition to Spica: Antares, Regulus, and Aldebaran. The Moon could also occult Pollux (Beta Geminorum) up until 117 BC, after which, precession and the star’s own proper motion carried it out of the Moon’s path.

The Moon’s path is a busy one in July. This weekend’s Spica event is part of a current series of occultations of the star by the Moon once per lunation, running out until November 17th, 2025.

Follow that Moon in the next few weeks, we have:

-Wednesday, July 17th: The +84% waxing gibbous Moon occults the bright star Antares (Alpha Scorpii) for South Africa.

-Sunday, July 21st: The Moon reaches Full phase… the July Full Moon is known as the Thunder, Buck or Hay Moon.

-Wednesday, July 24th: The -86% waning gibbous Moon occults the planet Saturn for southeast Asia.

-Thursday, July 25th: The -80% waning gibbous Moon occults the planet Neptune for the western Pacific.

-Monday, July 29th: The -36% waning crescent Moon occults the Pleiades star cluster (Messier 45) for southeast Asia.

All this, from simply watching one celestial body pass in front of another. Keep in mind, these are all part of a busy series of occultation cycles for the Moon in 2024. If skies are clear, don’t miss Saturday night’s occultation of Spica by the Moon.

The post The Moon Occults Spica This Weekend For North America appeared first on Universe Today.

Discussions about the GBD tend to take place in the conditional tense- what would, could, and should have happened. But the GBD actually existed and we can examine what actually happened.

The post Part 1: We Don’t Have to Wonder if the Great Barrington Declaration Could Have “Worked”. In the Real World, It Failed. first appeared on Science-Based Medicine.

Artificial intelligence (AI) chatbots have frequently shown signs of an 'empathy gap' that puts young users at risk of distress or harm, raising the urgent need for 'child-safe AI', according to a new study. The research urges developers and policy actors to prioritize AI design that take greater account of children's needs. It provides evidence that children are particularly susceptible to treating chatbots as lifelike, quasi-human confidantes, and that their interactions with the technology can go awry when it fails to respond to their unique needs and vulnerabilities. The study links that gap in understanding to recent reports of cases in which interactions with AI led to potentially dangerous situations for young users.

Using an instrument for ultrafast electron diffraction (MeV-UED), researchers discovered how an ultrathin material can circularly polarize light. This discovery sets up a promising approach to manipulate light for applications in optoelectronic devices.

Using an instrument for ultrafast electron diffraction (MeV-UED), researchers discovered how an ultrathin material can circularly polarize light. This discovery sets up a promising approach to manipulate light for applications in optoelectronic devices.

To offer cross-protection against diverse influenza virus variants, nanoparticle vaccines can produce pivotal cellular and mucosal immune responses that enhance vaccine efficacy and broaden protection, according to a new study.

The question of whether Mars ever supported life has captivated the imagination of scientists and the public for decades. Central to the discovery is gaining insight into the past climate of Earth's neighbor: was the planet warm and wet, with seas and rivers much like those found on our own planet? Or was it frigid and icy, and therefore potentially less prone to supporting life as we know it? A new study finds evidence to support the latter by identifying similarities between soils found on Mars and those of Canada's Newfoundland, a cold subarctic climate.

Within a group of decision-makers, the longer it takes someone to make a choice, the less likely they are to be influenced by their inherent biases according to a mathematical model

Two lions, one missing a leg, made a 1.5-kilometre swim through crocodile-infested waters in Uganda, probably in order to mate with females

Social media assures us that we can grow a rose cutting in a raw potato. But you're better off sticking with tried and tested methods of rose propagation, says James Wong

See some of the dazzling pictures that were shortlisted for the annual Astronomy Photographer of the Year competition

Some technologies never quite make it. But a new book, The Long History of the Future, shows how certain problems are just bigger and thornier than we thought

Exhausted by today's political and environmental instability, Annalee Newitz investigated what a future Earth might look like. Get ready for green mining, soft cities and robo-taxis