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We are all aware of the dangers of pollution to our air, water, and earth. In a recently published letter, scientists are advocating for the recognition and mitigation of another type of environmental pollution that poses equivalent personal and societal dangers: information overload.

Researchers investigated the propulsion mechanism by visualizing water flow around a swimmer during underwater dolphin-kick swimming in a water channel via particle image velocimetry. Their findings revealed that swimmers can utilize water flow and vortexes more effectively as their speed increases.

The period that liquid water was present on the surface of Mars may have been shorter than previously thought. Channel landforms called gullies, previously thought to be formed exclusively by liquid water, can also be formed by the action of evaporating CO2 ice, according to a new study.

Which process is best suited for mass production of perovskite solar cells? While solvent-based manufacturing processes are used in laboratories around the world, vacuum vapor-phase deposition processes are still the standard for the production of thin films for photovoltaics or organic light-emitting diodes. A new study that reveals major differences in the scientific discussion of these production processes.

A new paper presents findings about the Kuiper Belt Object 486958 Arrokoth, shedding new light on the preservation of volatile substances like carbon monoxide in such distant celestial bodies. The research uses Arrokoth as a case study to propose that many Kuiper Belt Objects -- remnants from the dawn of our solar system -- could still retain their original volatile ices, challenging previous notions about the evolutionary path of these ancient entities.

Advanced killer robots are more likely to blamed for civilian deaths than military machines, new research has revealed. The study shows that high-tech bots will be held more responsible for fatalities in identical incidents.

Advanced killer robots are more likely to blamed for civilian deaths than military machines, new research has revealed. The study shows that high-tech bots will be held more responsible for fatalities in identical incidents.

Researchers combined artificial intelligence and chemical biosensors to ferment the precursor of an Alzheimer's drug in bacteria.

A recent scientific breakthrough has emerged from the work of researchers aiming to combat SARS-CoV-2, the virus responsible for COVID-19. The study focuses on the design and development of a novel protein capable of binding to the spike proteins found on the surface of the coronavirus. The goal behind this innovative approach is twofold: first, to identify and recognize the virus for diagnostic purposes, and second, to hinder its ability to infect human cells.

Inspired by the classic drinking bird toy, scientists have developed an engine that efficiently converts energy from water evaporation into electricity to power small electronics. The device produces energy outputs exceeding 100 volts -- much higher than other techniques that generate electricity from water -- and can operate for several days using only 100 milliliters of water as fuel, according to a new study.

Research has found a less expensive and easier to use test to learn more about forensic touch DNA. This research has important implications for forensic investigations and being able to identify DNA from a primary contact -- someone who may have committed the crime -- as well as secondary DNA that was inadvertently and indirectly transferred through touch.

Pythons convert food into meat more efficiently than other livestock, and they can be fed on waste meat, but this doesn't mean snake meat is inherently more sustainable

Dina Rubina is a prominent Russian Israeli Jew who writes in Russian. Wikipedia gives this precis:

Rubina is one of the most prominent Russian-language Israeli writers. Her books have been translated into 30 languages. Her major themes are Jewish and Israeli history, migration, nomadism, neo-indigeneity, messianism, metaphysics, theatre, autobiography and the interplay between the Israeli and Russian Jewish cultures and languages.

This letter from Rubina comes from a site I don’t know, Truth of the Middle East (click on screenshot). It shows how Rubina staved off cancelation (for being Jewish) by canceling her appearance first. Click to read:

First, the intro:

Not long ago the Pushkin House in London together with the University of London invited the famous Israeli writer Dina Rubina to hold a meeting.
The topic was to be literary – a discussion of the writer’s books.
 Some time ago, Dina received a letter from the moderator of the meeting:

Then the email came that smells strongly like an impending cancelation:

“Good afternoon, Dina
The Pushkin House advertised our upcoming discussion on social media and immediately received critical messages regarding your position on the Palestinian-Israeli conflict. They would like to understand your position on this issue before reacting in any way.
Could you formulate your position and send it to me as soon as possible?”
Natalia! “

That letter is an arrant insult. Rubina was going to discuss her books, and her political stand on the war has no bearing on that. Even if it did, she had already been invited.  But the Pushkin House and the University of London are spineless, and surely wanted some groveling letter from Rubina that smacked of “both side-ism.” But that’s stupid given that she is an Israeli, a fact that, again, has no bearing on her book talk.

But Rubina has spine, and I put her response below. Instead of being canceled, she canceled her own talk and rebuked Pushkin House. I put her whole letter below because you should read it, because it’s “open”, and because she says exactly what needed to be said in response to Natlia’s insulting communication.

AN OPEN LETTER

from Dina Rubina

Dear Natalia!

    You have written beautifully about my novels; I am very sorry for the time you have wasted. But it seems we’ll have to cancel our meeting. The University of Warsaw and the University of Torun have just cancelled lectures by the remarkable Israeli Russian-speaking writer Yakov Shechter on the life of Jews in Galicia in the 17th and 19th centuries – “to avoid aggravating the situation”. I suspected that this would also happen to me, because now the academic environment is the main nursery of the most disgusting and rabid anti-Semitism, hiding behind the so-called “criticism of Israel”. I was expecting something like this, and even sat down three times to write you a letter on the subject… but I decided to wait, and so I have waited.

That’s what I want to say to all those who expect from me a quick and obsequious account of my position on my beloved country, which now (and always) lives in a circle of ardent enemies who seek its destruction; on my country, which is now waging a just patriotic war against a violent, ruthless, deceitful and sophisticated enemy:

The last time in my life I apologised in the headmaster’s office, in the ninth grade. Since then, I have done what I think is right, listening only to my conscience and expressing only my understanding of the world order and human laws of justice.

And so on.

I’m really sorry, Natalia, for your efforts and the hope that you could “cook something with me” – something that everyone will like.

Therefore, I ask you personally to send my reply to all those who are interested:

On Saturday 7 October, the Jewish holiday of Simchat Torah, the ruthless, well-trained, carefully prepared and perfectly equipped with Iranian weapons Hamas terrorist regime ruling the Gaza enclave (which Israel left some 20 years ago) attacked dozens of peaceful kibbutzim and simultaneously pelted the territory of my country with tens of thousands of rockets. Atrocities that even the Bible cannot describe, atrocities and horrors that make the crimes of Sodom and Gomorrah pale in comparison (captured, by the way, by the frontal and chest cameras of the murderers themselves and boastfully sent by them in real time to the Internet), can shock any normal person. For several hours, thousands of gleeful, blood-drunk animals raped women, children and men, shot their victims in the crotch and in the head, cut off women’s breasts and played football with them, cut babies out of the bellies of pregnant women and immediately beheaded them, tied up small children and burned them. There were so many charred and completely burnt bodies that for many weeks the pathologists could not cope with the enormous burden of identifying individuals.

   My friend, who worked in a New York hospital waiting room for 20 years and then spent another 15 years in Israel identifying remains, was one of the first to arrive in the burned and blood-soaked kibbutzim with a group of rescuers and medics… She still can’t sleep. A medic used to cutting up bodies – she fainted from what she saw and then vomited all the way back to the car. What these people have seen is beyond words.

    Together with the Hamas fighters, the “civilian population” rushed into the holes in the fence, joined the pogroms on an unprecedented scale, robbed, killed and dragged whatever they could get their hands on into Gaza. Among these “peaceful Palestinians” were 450 members of the UN’s UNRWA scum. Everyone was there, and judging by the stormy total joy of the population (also captured in these inconvenient times by hundreds of mobile cameras) – there were a lot of people – Hamas supports and approves, at least before the real fighting starts, of almost the entire population of Gaza… The main problem: our residents were dragged into the beast’s lair, more than two hundred of them, including women, children, the elderly and non-essential foreign workers. About a hundred of them are now rotting and dying in the Hamas dungeons. Needless to say, these harassed victims are of little concern to the “academic community”.

But that’s not what I’m talking about. I am not writing this to make anyone sympathise with the tragedy of my people.

For all these years, when the world community has literally poured hundreds of millions of dollars into this piece of land (the Gaza Strip) – and the annual budget of the UNRWA organisation alone is a BILLION dollars! – All these years, Hamas has used this money to build an empire of the most complex underground tunnel system, to stockpile weapons, to teach primary school children how to dismantle and reassemble a Kalashnikov assault rifle, to print textbooks in which the hatred of Israel defies description, in which even the maths problems go like this: “There were ten Jews, Shahid killed four, how many are left?” – with every word calling for the murder of Jews.

And now that Israel, shocked at last by the monstrous crime of these bastards, is waging a war to destroy the Hamas terrorists, who have prepared this war so carefully, planting thousands of shells in all the hospitals, schools, kindergartens… – here the academic world of the whole world has risen up, worried about the “genocide of the Palestinian people”, based, of course, on data provided by… who? That’s right, by the same Hamas, by the same UNRWA… The academic community, which was not concerned about the massacres in Syria, the massacre in Somalia, the mockery of the Uighurs or the millions of Kurds persecuted for decades by the Turkish regime – this very concerned public, wearing “Arafat” around their necks, the trademark of the murderers, rallies under the banners “Free Palestine from the river to the sea! – which means the total destruction of Israel (yes, many of these “academics”, as surveys show, have no idea where this river is, what it is called, where some borders are…). – Now this very public asks me to “take a clear position on this issue”.

Are you serious?! Are you serious?!!

You see, I’m a writer by profession. All my life, for more than fifty years, I have been folding words. My novels have been translated into 40 languages, including Albanian, Turkish, Chinese, Esperanto… and many others.

Now, with great pleasure, without using too many expressions, I sincerely and with all the strength of my soul send all the brainless “intellectuals” interested in my position go to ass. In fact, very soon you will all be there without me”.

Dina Rubina

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

It’s their loss.

Notice that she says there were 450 UNRWA members at the October 7 massacre. I knew that there were 13 who had been fired, but this higher figure may well be accurate, though I can’t confirm it yet. There are 13,000 UNRWA staff in Gaza, so if it was 450, that would be 3.5% of the entire staff, all present at the butchery.

And I wonder how many Palestinian writers or Arab writers would be asked to “clarify” their position before they gave a book talk.

After falling short in its first two attempts, SpaceX got its Starship super-rocket to an orbital altitude today during the launch system’s third integrated flight test. Now it just has to work on the landing. 

Today’s test marked a major milestone in SpaceX’s effort to develop Starship as the equivalent of a gigantic Swiss Army knife for spaceflight, with potential applications ranging from the deployment of hundreds of Starlink broadband satellites at a time to crewed odysseys to the moon, Mars and beyond.

The 396-foot-tall (120-meter-tall) rocket lifted off from SpaceX’s Starbase facility in South Texas at 8:25 a.m. CT (1325 GMT), with all 33 of the first-stage booster’s methane-fueled Raptor engines firing. The Super Heavy booster is considered the world’s most powerful launch vehicle, with 16.7 million pounds of thrust at liftoff.

Minutes after launch, the rocket’s second stage — known as Ship — successfully executed a hot-staging operation to start up its six engines while still attached to the Super Heavy booster. After stage separation, Ship continued onward at orbital velocity to an altitude of about 140 miles (230 kilometers). Meanwhile, the booster began a series of burns that were meant to bring it down to a soft splashdown in the Gulf of Mexico.

The Super Heavy splashdown turned out to be not as soft as SpaceX hoped. Only a few of the booster’s engines were able to light up again for the intended landing burn. The last telemetry from the booster seemed to suggest that it hit the water at almost 700 mph (1,112 kilometers per hour). “We didn’t light all the engines that we expected, and we did lose the booster,” SpaceX commentator Dan Huot said during today’s webcast. “We’ll have to go through the data to figure out exactly what happened, obviously. … But wow, Ship in space!”

For more than 40 minutes, a camera on the second stage transmitted stunning views of Earth as seen from an orbital height. SpaceX also tested the opening and closing of a payload door that’s meant to be used for satellite deployment in orbit — and tried out a refueling procedure that involved transferring liquid oxygen between tanks.

The flight plan for this test didn’t call for doing a complete orbit. Rather, the trajectory was designed to have Ship come down for its own soft splashdown in a remote stretch of the Indian Ocean.

The climax of the descent came when Ship’s onboard camera captured the glow of plasma generated by the craft’s descent at speeds in excess of 16,500 mph (26,700 kilometers per hour). The atmospheric heating was expected to reach 2,600 degrees Fahrenheit (1,425 degrees Celsius).

“We’ve never seen anything like this before,” SpaceX commentator Kate Tice said of the fiery real-time video, which was transmitted down to Earth via SpaceX’s Starlink network.

SpaceX founder Elon Musk marveled at the sight in a posting to X / Twitter, the social media channel he owns:

Watch the super hot plasma field grow as Starship re-enters the atmosphere! pic.twitter.com/to4UOF2Kpd

— Elon Musk (@elonmusk) March 14, 2024

A few minutes into the descent, SpaceX lost the signal from Ship — and the prolonged silence led SpaceX’s mission controllers to assume that the ship was lost during re-entry. It’s possible that the second stage’s engines weren’t able to fire properly to reduce the speed of the descent. The mission team will have to analyze the data to determine what went wrong.

“No splashdown today,” Huot said. “But it’s incredible to see how much further we got this time around.”

Huot emphasized that the aim of today’s test was to learn how to improve future Starships, and eventually make them reusable. “The data is the payload on one of these flights,” he said.

SpaceX is already getting ready for the next test flight, and the ones after that. “Hopefully, at least 6 more flights this year,” Musk said in a pre-launch X / Twitter posting. The precise timing will depend on approvals from the Federal Aviation Administration.

NASA is depending on SpaceX to provide a version of Starship that would serve as the landing system for the Artemis program’s first crewed mission to the lunar surface, currently set for 2026. Today, NASA Administrator Bill Nelson congratulated SpaceX on its “successful test flight.”

“Starship has soared into the heavens,” Nelson wrote on X / Twitter. “Together, we are making great strides through Artemis to return humanity to the Moon — then look onward to Mars.”

Musk has pointed to Starship as the vehicle that could carry thousands of settlers to Mars in years to come — and he touched upon that theme again after today’s test flight.

“Starship will make life multiplanetary,” he wrote.

The post Starship Reaches Orbit on SpaceX’s Third Test but Breaks Up on Re-Entry appeared first on Universe Today.

Ten years’ worth of observations of a wild chimpanzee community show that most adults stop playing when food is short, but not mothers and their young

The world’s most powerful rocket, Starship, launched from Texas and reached an altitude of more than 230 kilometres, travelling further and faster than it has done before. But it seems to have been destroyed on re-entry into Earth’s atmosphere

Pamela Paul’s new column in the NYT (click on screenshot below or find the piece archived here) is about “mission creep” in American universities: the drift away from teaching, learning, and doing research to
promulgating social justice. As we’ve discussed so often, there are dangers inherent in this transformation, and some of them are occurring now, including Republican attempts to control universities as well as a decline in public respect for universities among Republicans, Democrats and folks among all ages and socioeconomic groups.

The biggest problem, of course, is the ideological slant that universities are taking, nearly all tilting left with some having more than 80% of the faculty describing themselves as liberal (e.g., Harvard). That in itself is a problem as students don’t get exposed to a panoply of views, but it’s worse because those on the Left—particularly the so-called progressive Left—can’t restrain themselves from making “official” university pronouncements on political, ideological, and moral issues, issues that themselves are academically debatable and whose imprimatur by the university as “official views” chills speech. If a University issues an official statement that there should be a ceasefire in Gaza, what untenured faculty member or student dares buck this position?

To keep free speech going without this kind of “chill”, the University of Chicago was the first to adopt and implement a policy of institutional neutrality, so that no University official or department can make such pronouncements. This principle, which went into effect in 1967, is called the Kalven Report, and you can read it here.

Kalven has worked pretty well here. Departments that couldn’t restrain themselves from taking stands on issues from war to abortion to shootings have had their statements taken down, and the University has issued virtually nothing about the Hamas/Israel war (see here for our anodyne acknowledgment, which basically says “there’s a war on and here’s where to go for help”). The only exceptions we have are for issues, like DACA, which can affect the University’s mission directly.

But so far only a handful of schools, like Vanderbilt and UNC Chapel Hill, have adopted institutional neutrality, though others like Williams and Harvard are contemplating it. But since institutional neutrality is essential in propping up a free speech policy, this reluctance to adopt Kalven is distressing, especially given that the Chicago Principles of Free Expression—the First-Amendment-like policy of free speech—have been adopted by over 100 schools. My conclusion: it’s easy to pass policies on free speech (which, as we see from Harvard’s case, have been implemented haphazardly), but it’s hard to make academics stop proclaiming the views they like as the “values of our school.” (Of course Kalven and all of us think academics have the right to say whatever they want as private citizens.)

And so to the piece; again, click to read.

Here’s Paul’s bit on why universities should shut up about taking official stands on issue that don’t bear on their mission. Sadly, she doesn’t mention the Kalven Report, which I think reflects a lack of historical perspective. But the rest is fine:

Right now, the university’s message is often the opposite. Well before the tumultuous summer of 2020, a focus on social justice permeated campuses in everything from residential housing to college reading lists.

“All of this activity would be fine — indeed, it would be fantastic — if it built in multiple perspectives,” noted Jonathan Zimmerman, author of “Whose America: Culture Wars in the Public Schools,” in a 2019 essay in The Chronicle of Higher Education. “For the most part, though, it doesn’t.”

Instead, many universities have aligned themselves politically with their most activist students. “Top universities depend on billions of dollars of public funding, in the form of research grants and loan assistance,” The Economist editorialized last week. “The steady leftward drift of their administrations has imperiled this.”

One of the starkest examples of this politicization is the raft of position statements coming from university leadership. These public statements, and the fiery battles and protests behind them, take sides on what are broadly considered to be the nation’s most sensitive and polarized subjects, whether it’s the Dobbs ruling or DACA for young immigrants, the Israel-Hamas war or Black Lives Matter.

At last month’s conference [a meeting at Stanford on civil discourse], Diego Zambrano, a professor at Stanford Law School, made the downsides of such statements clear. What, he asked, are the benefits of a university taking a position? If it’s to make the students feel good, he said, those feelings are fleeting, and perhaps not even the university’s job. If it’s to change the outcome of political events, even the most self-regarding institutions don’t imagine they will have any impact on a war halfway across the planet. The benefits, he argued, were nonexistent.

Indeed! Such statements are purely attempts to flaunt virtue and have no effect on social policy. Do you think that any statement by a university or school on the war in Gaza will have the slightest effect on the war itself? Yet such statements are being made everywhere, including from city councils and secondary school boards. Even the city of Chicago issued a call for a cease-fire. I’m sure Israel and Hamas are paying attention!

Paul continues:

As for the cons, Zambrano continued, issuing statements tends to fuel the most intemperate speech while chilling moderate and dissenting voices. In a world constantly riled up over politics, the task of formally opining on issues would be endless. Moreover, such statements force a university to simplify complex issues. They ask university administrators, who are not hired for their moral compasses, to address in a single email thorny subjects that scholars at their own institutions spend years studying. (Some university presidents, such as Michael Schill of Northwestern, have rightly balked.) Inevitably, staking any position weakens the public’s perception of the university as independent.

The temptation for universities to take a moral stand, especially in response to overheated campus sentiment, is understandable. But it’s a trap. When universities make it their mission to do the “right” thing politically, they’re effectively telling large parts of their communities — and the polarized country they’re in partnership with — they’re wrong.

When universities become overtly political, and tilt too far toward one end of the spectrum, they’re denying students and faculty the kind of open-ended inquiry and knowledge-seeking that has long been the basis of American higher education’s success. They’re putting its future at risk.

If you want schools to be Truth Universities and not Social Justice Universities (do see Jon Haidt’s excellent lecture on this bifurcation), then the cons far outweigh the pros when it comes to taking stands.  Paul’s last three paragraphs are succinct, clear, and correct. To universities and departments who are itching to take political stands that don’t affect their school’s mission, PLEASE SHUT UP.  Members of university communities have plenty of venues, like “X”, Facebook, or websites like this, to express their own private opinions.

After I saw that Paul had left out the Kalven Principles, I posted a comment after her piece—the first time I’ve ever commented in the NYT. Here it is, with one comma that shouldn’t be there:

The world’s most powerful rocket launched from Texas and reached an altitude of more than 230 kilometres. Starship carried out tests before attempting to re-enter Earth’s atmosphere to splash down in the ocean

Thank Ceiling Cat that several readers sent in wildlife photos, so we’re good to go for a bit over a week, I think. But remember, I always need more. If you’re a newbie, read the “how to send me photos” page on the left sidebar and please try to conform to the format.

Today Jim Blilie has returned with some varied b&w photos. His captions are indented, and you can enlarge the photos by clicking on them.

I recently joined some Facebook groups dedicated to black and white photography, which I did a lot of in my youth (pre-digital days).  I spent years scanning my negatives, slides, and, recently completed, my Dad’s slides and negatives.  (In 2023 I scanned 4918 of my Dad’s negatives.)

Inspired by these FB groups:  These are all my photos:  Black and white images that I like.  Some are scans of Kodachrome slides or are native digital images (color) that I converted to black and white images.  Most have only global adjustments (overall exposure, contrast, etc.) but some have “burns” and “dodges” to produce the visualized the final image.  I follow Ansel Adams’ Zone System method, both when I used film and paper prints and now in digital.  Many of these images will display Adams’ influence (I hope!). These reach way back in my photography.  I got my first camera (Pentax K-1000) in 1978.

First:  1981, Aspen leaf with rain droplets, northern Minnesota.  Scanned Tri-X Pan film. For this one I remember the exposure information: Pentax M 135mm f/3.5 lens with extension tubes, f/32, 30 seconds:

Next, two more from 1981.  Reflections in Maligne Lake, Jasper National Park and Mount Robson and Berg Lake (taken with a 1950 Rolleiflex, 6cm film; yes, I humped a Rolleiflex and a tripod up to Berg Lake!).  Both scanned Tri-X Pan:

Next is an image from Amboseli National Park in Kenya in 1992:  Elephants under rain clouds.  Scanned Kodachrome 64:

Next is an image of the foot bridge:  Passerelle Léopold-Sédar-Senghor in Paris:

Next is an image of Mount Whitney taken from near Lone Pine, California, February 2023. This is the classic view of the peak from the east.

Next is another image taken in February 2023:  The Visitor building and lawn of Sunnylands estate in Rancho Mirage, California:

Next is an image of the very upper Aosta Valley in Italy, just across Mont Blanc from Chamonix. This photo shows the Mont Blanc massif from the Italian side.  (Lumix 7-14mm f/4.0 lens):

Next is an image I call The Shape of the Land.  A photo (2023) of the Palouse region landscape in the southeastern Washington state, near where our son Jamie attends Washington State University.  The Palouse is characterized by these sinuous rolling hills of Loess soil.  This area grows an immense amount of wheat:

Finally, two photos taken on this last New Years’ Eve, 31-Dec-2023, near Hood River, Oregon, very close to our home in southern Washington.  We had brilliant clear skies above a strong inversion layer, which provided dramatic clouds through which we ascended on our hike:

Equipment:

1950 Rolleiflex 6cm camera  inherited from my Dad; Schneider 75mm f/3.5 lens
Pentax K-1000, ME Super, and LX cameras
Various Pentax M series and A series lenses
Pentax K-5 digital camera and various Pentax D lenses
Olympus OM-D E-M5 mirrorless M4/3 camera and various Olympus and Lumix lenses
Epson V500 Perfection scanner and its software
Lightroom 5 photo software

On April 8th, 2024, a small strip of North America will witness a total solar eclipse. Total solar eclipses are amazing, life-changing experiences; I hope you have a chance to experience one, as I did.

Everyone else from Central America to northern Canada will see a partial solar eclipse. What good is a partial solar eclipse?

Astonishingly, the best thing about a partial solar eclipse seems to have essentially disappeared from public knowledge. We’ve got three weeks to change that, and I hope you’ll help me — especially the science journalists and science teachers among you.

The best thing about a partial solar eclipse is that you can measure the Moon’s true diameter, armed with only a map, a straight-edge, and a leafy tree or a card with a pinhole in it. No telescope, no eclipse glasses, no equipment that costs real money or is hard to obtain. You’ll get an answer that’s good within 10-20 percent, with no effort at all. And in the process you can teach kids about shadows, about simple geometry (no trigonometry needed), about the Earth, Moon, and Sun, and about how scientists figure things out.

About a week later, you can measure the Moon’s distance from Earth, too. All you need for that is a coin, a ruler, and drawings of similar triangles.

In this post, I’ll explain

• First, the two easy steps necessary to measure the size of the Moon;
• Second, evidence that this actually works;
• Third, the reasons why it works;
• Fourth, a brief comment (and a link to an older, longer post about it) showing how to measure the Moon’s distance once you know its size

The Amazingly Easy Way to Measure the Size of the Moon

1. Before the eclipse, find a map that shows your location and the “totality strip” where the eclipse is total. On that map, measure the smallest linear distance (not the driving distance!) between you and the edge of the strip. Call that distance L.
   
2. Next, right at the maximum of the eclipse, when the Moon’s silhouette blocks as much of the Sun as it can from your location, determine the fraction of the Sun’s diameter that remains visible, measured at the thickest part of the Sun’s shape. (You can see the shape of the eclipsed Sun where it is projected onto the ground or a piece of paper, after the sunlight has passed through leaves, or through a colander, or through a grid of your own fingers, or through any other little hole through which light can pass.) Call that fraction F.

Then the diameter of the Moon D is roughly equal to L divided by F:

That’s all there is to it!

This estimate should be accurate to within 10-20% (as long as you’re not too close to the Earth’s poles or too close to the totality strip; we can talk about why later.) Any child over ten can carry this out with a little help.

Click here to see an example of how this works

From Boston, here’s how I can measure L, using Google Maps and an eclipse map showing the location of the totality strip:

From Boston to the totality strip is about 145 miles.

Meanwhile timeanddate.com predicts that in Boston at mid-eclipse the Sun will appear as shown below: a fraction of around 6 to 8% of the Sun will be unblocked. (We’re so close to the totality strip that measuring F is quite difficult to do accurately, so our estimate of the Moon’s size will be more uncertain than for people further away.)

The fraction of the Sun’s diameter that will be visible at mid-eclipse in Boston is less than 10%; the full diameter of the Sun is shown in orange. Prediction from timeanddate.com .

That will give us (if we take F=7% as a best guess) an estimate of the Moon’s size

• D = L / F = 143 miles / 0.07 = 2050 miles .

(If we let F range from 6% to 8%, this estimate really ranges between 1900 and 2200 miles.) The Moon’s true diameter is about 2160 miles, so this is wonderfully successful, given its ease.

Is this too good to be true? Let’s see.

Some Basic Evidence

Here’s a map from NASA (via Wikipedia) showing where the eclipse is total and partial. Let’s call the region of totality the “totality strip”, and the regions where the eclipse is partial the “northern partiality zone” and the “southern partiality zone.”

Figure 1: As with all total eclipses, the one on April 8th will have a narrow totality strip (dark blue) where the eclipse is total, surrounded by two large “partiality zones” (light blue) in which the eclipse will be partial. Eclipse Predictions by Fred Espenak, NASA’s GSFC

Now here’s the same map with the Moon, correctly sized, superposed on the two partiality zones. You see that indeed the width of each partiality zone is roughly the size of the Moon — slightly larger, but much less than twice as large. [Because the eclipse is north of the equator, the northern partiality zone is closer to the north pole, and the Earth’s curvature causes it to be somewhat larger than the southern partiality zone. This is discussed in an aside later in this post.]

Figure 2: Each partiality strip is a little wider than the diameter of the Moon, for reasons explained later.

Let’s say you’re in one of the partiality zones, and let’s call its width W. If you’re right near the outer edge of that zone, then L is approximately W. That’s also where the eclipse barely happens — the Moon just clips the edge of the Sun — and so, since the Sun’s diameter is hardly blocked at all, F is close to 1. Your estimate will then be

• D = L / F = W / 1 = W,

which is in accord with Figure 2.

Suppose instead that you are halfway between the totality strip and the outer edge of your zone (measured on a line perpendicular to the totality strip.) Then L = W/2. But also the Moon will block half the Sun’s diameter, leaving half of it unblocked: F = 1/2. That means that you will estimate, again,

• D = L/F = (W/2) / (1/2) = W.

More generally, if your distance from the totality strip is L, and L is a fraction P of the width W of the partiality zone, i.e.

• L = P W ,

then the fraction F of the Sun’s diameter that will be unblocked at mid-eclipse will also be approximately P. Therefore, no matter where you are in the zone,

• D = L / F = (P W) / P = W ,

so your estimate of the Moon’s diameter will always come out more or less right.

(That said, if you’re very close to the totality strip, F will be hard to measure precisely, so your estimate may be very uncertain; and if you’re close to the poles, W will be significantly larger than D, so your estimate will be poor. Fortunately, that won’t be true for most of us.)

What’s behind this clever trick? Here’s the reasoning.

Why Does This Work?

What’s great about this trick is that it’s not hard to understand, though it does take a few steps. [I’m not sure I yet have the best pedagogical strategy for laying out those steps; suggestions welcome.]

Why the Partiality Zones are as Wide as the Moon

First, we need to understand why the width of each partiality zone is roughly the same as the width of the Moon — why D and W are almost the same, as long as we are far from the Earth’s poles. It all has to do with shadows — moon shadows, of both types.

You may have noticed (kids often do) that there are often two types of shadows visible when you’re at home and lit by a single central light. If a thumbtack lit by a small light bulb is close to a wall, it casts a shadow that is crisp and about the same size as the tack. But as you move the tack away from the wall, the shadow becomes fuzzier. If you look closely, you’ll see that the inner dark part of the shadow (the “umbra”) is shrinking, while there’s an outer part (the “penumbra”), quite hard to see, that is growing.

Eventually, when the tack is far enough away, the inner dark part will become almost a dot. At that point, the outer dim shadow — you may only barely see it — has a diameter about twice the diameter of the tack. See Figure 3.

Figure 3: How a shadow of a tack changes as it moves away from the wall. (Left) The shadow is crisp and the same size as the tack. (Center) The dark umbra is narrower than the tack, while the dim penumbra is wider than the tack. (Right) As the dark umbra becomes very narrow, the penumbra becomes twice the width of the tack (as indicated by the two tack-sized disks). Credit: the author.

For the solar eclipse, it’s the same idea, except that instead of bulb, tack and wall, we have Sun, Moon and Earth.

There’s simple geometry behind this shadow-play; I’ve drawn it vertically in the figure below, so that you can see it no matter how narrow your screen. Let’s assume that the Sun is much further away from Earth than the Moon is (a fact that you can also verify during daytime, either a week after the eclipse or a week before.) I’ve drawn four lines, two of them red, two of them black; watch where they go.

Figure 4: The Sun is totally eclipsed in the little gap between the black lines; it is partially eclipsed between the red and black lines. Not to scale.

Inside the black lines, the Moon totally blocks the Sun; both the left edge and right edge of the Sun in the figure are blocked. Inside the red lines, the Moon partially blocks the Sun. And so, at the moment shown, the little space between the two black lines is where the eclipse is total; that’s a location within the totality strip. Meanwhile, the distance between each red line and the nearest black line is the width W of one of the partiality zones.

For maximum simplicity, I’ve drawn this where the Sun, Moon and Earth are perfectly lined up, so that the total eclipse is occuring where the Earth’s surface is nearest the Sun and Moon. That makes both partiality zones the same size. In the aside below, I’ll show you what happens if this isn’t the case. But let’s not get distracted by that yet.

The important thing is that because the Sun is so much further than the Moon, the red and black lines from the left edge of the Sun are almost parallel. Where they meet the Moon, they are separated by the Moon’s diameter — that is, by the distance D. But the distance between two parallel lines is constant, so the distance between two nearly parallel lines changes very slowly. This means they are still a distance D apart when they reach the Earth.

On top of this, the two black lines almost meet; the totality strip is very narrow. Taken together, these facts imply that W, the width of the region on Earth’s surface between a red line and the closest black line, is roughly the same size as D!

As noted in an aside below, the Earth’s curvature tends to make the partiality zones a bit larger than the Moon’s diameter, while for an eclipse nearing a pole of the Earth, the partiality zone closest to the pole will be larger than the other partiality zone. But these are details; they don’t change the basic story.

Click here for an brief discussion of why W and D aren’t quite the same

As noted, W isn’t quite D. Even with the eclipse centered on the Earth as in Figure 5, W is larger than D because the Earth’s surface is a sphere. (This is somewhat compensated for by measuring L to the edge of the totality zone rather than its center or opposite edge.)

The width W of the partiality zone is wider than the diameter D of the Moon because of the Earth’s shape.

Second, if the eclipse is far from the equator, the partiality zone nearer to a pole of the Earth will be larger than the other.

If the location of totality is offset from the line connecting Moon and Sun, then the totality zone on the side of the offset will be larger than the other, and than D, due to the Earth’s curvature.

In short, this is not a method designed to get a precise or accurate measurement of the Moon’s diameter. But it’s perfectly fine if one’s aim is merely to get a rough idea of how nature works, which is often more than enough for scientists, as well as for everyone else. There is an opportunity here to talk to students about the nature of approximations, when and why it’s okay to use them, and how to improve upon them.

Why the Unblocked Fraction of the Sun’s Diameter Plays the Key Role

Second, we have to understand why the unblocked fraction F of the Sun’s diameter is roughly the same as what we called P (the distance L to the totality strip divided by the width of the partiality zone W.) This is illustrated in Figure 5, where again I’ve drawn four lines on each image, but now all four begin from the location at which we are observing the eclipse, and they indicate where the Moon and Sun appear to us.

Figure 5: What one sees in the partiality zone between the red and black dots; the orange and grey lines show the location and width on the sky of the Sun and Moon.(Far Left) In the totality zone, F=P=0. (Far Right) Near the edge of the partiality zone, F and P are close to 1. (Near Left and Right) Throughout the partiality zone, F=P, as shown for P=1/6 and 1/2. Not to scale.

In each image in Figure 5, the totality strip is indicated by the black dot, and the edge of a partiality zone by the red dot. The Sun’s disk in the sky is spanned by the green lines, and its apparent width in the sky is shown by the orange line; the Moon’s disk is spanned by the blue lines, and its apparent width is shown by the grey line.

In the far left image, the observer is in the totality strip, so P=0; the Moon blocks the Sun completely, so the grey line aligns with the orange line and F=0. At far right, the observer is at the outer edge of the partiality zone, so P is almost 1; the grey line almost misses the orange line completely, so almost all the Sun’s diameter remains unblocked and F is almost 1. In between are shown intermediate situations where F and P are both 1/6 or both 1/2. The closer the observer gets to the totality strip, making P smaller, the less of the Sun is unblocked, making F smaller by the same amount.

Bonus: Measure the Distance to the Moon in Daylight

I’ve explained how this works in this older post. For today, here’s a quick summary.

Within a week after the eclipse, the Moon will reach first quarter, which means that the Moon will rise around noon. In the afternoon, then, you can see it in the East. Then you can have one person hold a penny, and another person move until the penny perfectly eclipses the Moon; a third person can measure the distance s between the person’s eyes and the penny. Then, measuring the diameter d of the penny, we can use similar triangles to convince ourselves that the distance S to the Moon, divided by the diameter of the Moon D, is the same as the distance from observer to penny divided by the diameter of the penny:

• S/D = s/d

and so

• S = (s/d) D

Since we measured D during the eclipse, we now know S also.

By the way, in another old post, I showed that we can also confirm that our original assumption, that the Sun is much, much further than the Moon, is correct. At first quarter — i.e. one quarter of the way through the Moon’s monthly cycle — one can verify two things at once, by eye:

• the Moon is half lit
• the Moon is 90 degrees away from the Sun in the sky

These two things can only both be true if the Sun is much further than the Moon.

Spread the Word

So you see, it’s not only easy to measure the Moon’s size during an eclipse, it’s relatively easy to explain how and why the method works. To do so requires a range of logical reasoning tools, some drawings of lines and triangles, and a little experimentation with shadows, but no actual math. (I’m sure it can be done better than I did it here.) On top of that, the measurement can be carried out in daylight, while most children are in school. I think it’s a great opportunity for science education — a chance for a meaningful fraction of the 600 million people in North America to experience scientific reasoning for themselves, and to observe how it leads to consistent, reliable knowledge.