# Tallest cliffs, by falling duration

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If you threw something over a certain cliff on a moon of Uranus, it would take over ten minutes to hit bottom.

By this measure, local fall time rather than absolute height, what are the near contenders to the prize for tallest cliff on a body in hydrostatic equilibrium in the solar system? Throwing the object horizontally at a few meters per second is ok. Not ok is throwing it beyond a tiny body's Hill sphere. Cliffs, not spheres.

Simplifying assumptions about atmospheres and exospheres are ok.

This answer shows that the close orbital period around a spherical body of uniform density is

$$T = sqrt{frac{3 pi}{G ho}}$$

and so the orbit's period $$T$$ is defined only by the body's density $$ho$$, not its size. It takes about 90 minutes to orbit the Earth in a low orbit, and it would likewise take 90 minutes for an atom to orbit a spherical speck of dust with a similar average density to that of Earth. (uncharged, unpolarizable dust, ignoring other forces e.g. Coulomb, Van der Waals, Casimir, etc.)

Let's compare cliffs on a spherical planet, small asteroid, and piece of dust. Assume the height of each cliff divided by the radius of the object is the same, and call the fraction

$$f = frac{h}{R}.$$

So if $$f=$$ 1%, then that's 64 km on Earth, 64 m on a 1 km radius asteroid, and 10 microns on a 1 mm radius piece of dust.

The fall time is

$$t=sqrt{frac{2h}{a}} = sqrt{frac{2fR}{a}}$$

where $$a$$ is the gravitational acceleration, keeping it simple by assuming it's constant though it changes slightly as we fall from such a great height.

$$a = frac{GM}{R^2}$$

$$M = frac{4}{3} pi ho R^3$$

$$a = frac{4}{3} pi G ho R$$

So

$$t = sqrt{frac{3f}{2pi G ho}}$$

For spherical bodies of the same density with cliffs of heights as a fixed fraction of radius, the time it takes to fall down the cliff is independent of the size of the body, and varies as the inverse square root of the density of the body.

For a $$0.01 R$$ cliff on a body of density 5.51 g/cm^3 (Earth's average density) that works out to 114 seconds, or about 2 minutes, and compares to 5063 seconds or 84 minutes for an orbit that skims the surface.

Let's apply @uhoh's answer's equation to a few bodies. Numbers come from the obvious Wikipedia pages unless otherwise stated. G = 6.6741e-11, in kg-m-s.

Verona Rupes on Miranda.
f = 20 km / 236 km, ρ = 1200 kg/m^3. So t = 711 s.

Enceladus has rifts 1 km deep.
f = 1 km / 252 km, ρ = 1600. So t = 133 s.

Those are the two bodies with smallest mean radius, of all solar system bodies in hydrostatic equilibrium.

Let's try a much smaller eccentric body, just to check.
The nucleus of the comet Wild 2 has cliffs "hundreds of meters tall" (Ulivi's "Robotic Exploration of the Solar System," part 3, p. 228).
f = 200 m / 6400 m, ρ = 600. So t = 610 s.

So Miranda's Verona Rupes beats even a comet. Compared to Miranda, any other round body is much bigger (f is much smaller) and significantly denser (ρ is bigger), so to beat this it would need truly brobdingnagian cliffs, which flybys would have seen by now at least with radar if not with visible light.

I could grind through rest of that table of bodies in h.eq., but it's a safe bet that Verona Rupes wins by a long shot, Enceladus is a distant second, and everything else is a giant hardly differentiated peloton.

## Here’s Why These Six Ancient Civilizations Mysteriously Collapsed

A section of the Mayan Troano Codex, one of three surviving pre-Columbian Maya books.

Universal History Archive/Getty Images

Arguably the New World’s most advanced pre-Columbian civilization, the Maya carved large stone cities into the jungles of southern Mexico and Central America, complete with elaborate plazas, palaces, pyramid-temples and ball courts. Known for their hieroglyphic writing, as well as their calendar-making, mathematics, astronomy and architecture skills, the Maya reached the peak of their influence during the so-called Classic Period, from around A.D. 250 to A.D. 900. But at the end of the Classic Period, in one of history’s great enigmas, the populace suddenly deposed its kings, abandoned the cities and ceased with technological innovation.

Dozens of theories have been put forth to explain what happened. Some historians, for instance, point to a major drought, exacerbated by deforestation and soil erosion, as the impetus for the societal collapse, while others put the blame on a disease epidemic, a peasant revolt against an increasingly corrupt ruling class, constant warfare among the various city-states, a breakdown of trade routes or some combination thereof. Though dispersed, the Maya never disappeared. Millions of their Mayan-speaking descendants continue to inhabit the region to this day.

## Early life and career

Galileo was born in Pisa, Tuscany, on February 15, 1564, the oldest son of Vincenzo Galilei, a musician who made important contributions to the theory and practice of music and who may have performed some experiments with Galileo in 1588–89 on the relationship between pitch and the tension of strings. The family moved to Florence in the early 1570s, where the Galilei family had lived for generations. In his middle teens Galileo attended the monastery school at Vallombrosa, near Florence, and then in 1581 matriculated at the University of Pisa, where he was to study medicine. However, he became enamoured with mathematics and decided to make the mathematical subjects and philosophy his profession, against the protests of his father. Galileo then began to prepare himself to teach Aristotelian philosophy and mathematics, and several of his lectures have survived. In 1585 Galileo left the university without having obtained a degree, and for several years he gave private lessons in the mathematical subjects in Florence and Siena. During this period he designed a new form of hydrostatic balance for weighing small quantities and wrote a short treatise, La bilancetta (“The Little Balance”), that circulated in manuscript form. He also began his studies on motion, which he pursued steadily for the next two decades.

In 1588 Galileo applied for the chair of mathematics at the University of Bologna but was unsuccessful. His reputation was, however, increasing, and later that year he was asked to deliver two lectures to the Florentine Academy, a prestigious literary group, on the arrangement of the world in Dante’s Inferno. He also found some ingenious theorems on centres of gravity (again, circulated in manuscript) that brought him recognition among mathematicians and the patronage of Guidobaldo del Monte (1545–1607), a nobleman and author of several important works on mechanics. As a result, he obtained the chair of mathematics at the University of Pisa in 1589. There, according to his first biographer, Vincenzo Viviani (1622–1703), Galileo demonstrated, by dropping bodies of different weights from the top of the famous Leaning Tower, that the speed of fall of a heavy object is not proportional to its weight, as Aristotle had claimed. The manuscript tract De motu (On Motion), finished during this period, shows that Galileo was abandoning Aristotelian notions about motion and was instead taking an Archimedean approach to the problem. But his attacks on Aristotle made him unpopular with his colleagues, and in 1592 his contract was not renewed. His patrons, however, secured him the chair of mathematics at the University of Padua, where he taught from 1592 until 1610.

Although Galileo’s salary was considerably higher there, his responsibilities as the head of the family (his father had died in 1591) meant that he was chronically pressed for money. His university salary could not cover all his expenses, and he therefore took in well-to-do boarding students whom he tutored privately in such subjects as fortification. He also sold a proportional compass, or sector, of his own devising, made by an artisan whom he employed in his house. Perhaps because of these financial problems, he did not marry, but he did have an arrangement with a Venetian woman, Marina Gamba, who bore him two daughters and a son. In the midst of his busy life he continued his research on motion, and by 1609 he had determined that the distance fallen by a body is proportional to the square of the elapsed time (the law of falling bodies) and that the trajectory of a projectile is a parabola, both conclusions that contradicted Aristotelian physics.

## Biblical Archaeology’s Top 10 Discoveries of 2020

There was no shortage of biblical archaeology news in 2020, despite COVID-19 restrictions that canceled almost all of Israel&rsquos scheduled excavations. Some limited digs still took place in Israel and surrounding countries, and research on previous excavations continued, resulting in some major announcements.

Here are 2020&rsquos biggest stories about archaeology connecting us with the biblical world:

##### 10. Assyrian god carvings

Italian and Kurdish archaeologists uncovered 15-foot rock carvings depicting an Assyrian king and seven Assyrian gods standing on the backs of sacred animals. The artwork was carved in relief in a cliff along a canal in the northern Kurdistan region of Iraq. The king is believed to be Sargon II, who ruled from 722 to 705 B.C. and conquered the northern kingdom of Israel (2 Kings 17:6). It is possible that the canal where the relief was found was dug by Israelites enslaved by Sargon II.

##### 9. Church built on a solid rock

A dig in Banias in northern Israel has revealed the remains of a fourth-century church built, as was a common practice, atop a shrine to another god. Banias was a cultic center of worship of the god Pan, and the shrine was likely for worship of the Greek deity associated with sex and spring.

Christians in the fourth century, however, would have recognized the location as the biblical Caesarea Philippi, near the location where Peter told Jesus, &ldquoYou are the Christ&rdquo and Jesus replied, &ldquoOn this rock, I will build my church&rdquo (Matt. 16:13&ndash19). One stone in the ruin is marked with cross etchings left by pilgrims who visited the church shortly after Christianity became the official religion of the Roman Empire.

##### 8. Fort allied with King David

Archaeologists uncovered a fortified building in the Golan Heights dated to the time of David&rsquos rule, about 1,000 B.C. A large basalt stone in the fortress is engraved with two horned figures with outstretched arms.

Archaeologists believe this building was an outpost of the kingdom of Geshur, an ally of King David. David&rsquos wife Maacah, the mother of Absalom, was the daughter of the king of Geshur.

## Highest fall survived without parachute

Vesna Vulović (Yugoslavia, b. 3 January 1950 d. 23 December 2016) was 23 and working as a Jugoslavenski Aerotransport hostess when she survived a fall from 10,160 m (33,333 ft) over Srbská Kamenice, Czechoslovakia (now Czech Republic), on 26 January 1972. According to the official accident report, an explosion tore the DC-9 she was working aboard to pieces in mid-air. Vulović was the only survivor.

In 2009, a journalistic investigation claimed that the aircraft had broken up at a much lower altitude than stated in the official accident report, having been forced into a rapid emergency descent prior to its disintegration. One of the journalists did however concede that the evidence was only circumstantial.

She was in hospital for 16 months after emerging from a 27 day coma and having many bones broken.

It is estimated that the human body reaches 99% of its low level terminal velocity after falling 573 m (1,880 ft) which takes 13 - 14 sec. This is 188-201 km/h (117 - 125 mph) at normal atmospheric pressure in a random posture, but up to 298 km/h (185 mph) in a head down position.

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## Time with respect to velocity

The general gravity equation for elapsed time with respect to velocity is:

Since the initial velocity vi = 0 for an object that is simply falling, the equation reduces to:

• t is the time in seconds
• v is the vertical velocity in meters/second (m/s) or feet/second (ft/s)
• g is the acceleration due to gravity (9.8 m/s 2 or 32 ft/s 2 )

Since the object is moving in the direction of gravity, v is a positive number.

Elapsed time of a falling object as a function of velocity or displacement

## Evidence for a Flood

". the fountains of the great deep [were] broken up, and the windows of the heavens were opened. And the rain was upon the earth forty days and forty nights."

This quote from the Book of Genesis is part of a familiar tale — the story of Noah's flood. Scholars have known for a long time that the Bible isn't the only place this story is found — in fact, the biblical story is similar to a much older Mesopotamian flood story in the epic of Gilgamesh. Scholars usually attribute things like the worldwide occurrence of flood stories to common human experiences and our love of repeating good stories, but recently scientists have started to uncover evidence that Noah's flood may have a basis in some rather astonishing events that took place around the Black Sea some 7,500 years ago.

The scientific version of Noah's flood actually starts long before that, back during the last great glaciation some 20,000 years ago.

This was a time when the earth looked very different from what we are used to today. Thick ice sheets extended down from the North Pole as far as Chicago and New York City. All that water had to come from somewhere, so ocean levels were about 400 feet lower than they are today. In essence, water that evaporated from the oceans fell as snow (which was compacted into glacial ice) rather than rain (which would flow back and replenish the oceans as it does now). The East Coast of the United States was 75 to 150 miles farther out than it is today, and places like Manhattan and Baltimore would have been inland cities. During this period, meltwater from the European glaciers flowed down to the Black Sea basin, then out through a river channel into the Mediterranean. Because the Mediterranean is connected to the world ocean at Gibraltar, it was also 400 feet lower than it is today, so this flow of fresh water through the Black Sea was downhill.

Two geologists at Columbia University's Lamont-Doherty Earth Observatory have offered a new theory of what happened next. William Ryan and Walter Pitman, in Noah's Flood (Simon & Schuster), postulate that as time went on, the world warmed, the glaciers retreated and meltwater from the European glaciers began to flow north into the North Sea, depriving the Black Sea of its main source of replenishment. The level of the Black Sea began to drop, and most of the area around its northern boundary — the area adjacent to present-day Crimea and the Sea of Azov — became dry land. At this point, the level of the Black Sea was several hundred feet below that of the Mediterranean, and the two were separated by the barrier of the Bosporus, then dry land. This situation, with the world ocean rising while the Black Sea was falling, could not last forever. Eventually, like a bathtub overflowing, the Mediterranean had to pour through into the Black Sea basin.

The idea that ocean basins can flood catastrophically during periods of rising sea levels is nothing new in geology. Five million years ago, long before there were any humans around, just such an event occurred. The level of the Atlantic Ocean had dropped, or some tectonic event had occurred, with the result that water could no longer get through, and the Mediterranean gradually shrank down to a desert spotted with a few salty bits of ocean. Subsequently, when either the Atlantic rose again or another geological change took place, ocean water began pouring back into the former sea. The basin filled, and the present-day Mediterranean was created.

We know such things because sediments reveal history. Ryan and Pitman began taking cores of the present-day Black Sea. The cores seemed to be telling a strange story indeed, particularly in the northern areas. At the very bottom of the cores, dozens of feet below the present seafloor, they found layered mud typical of river deltas.

Carbon-dating of shells in this mud indicates that it was laid down between 18,000 and 8,600 years ago. This data showed that an area of the Black Sea about the size of Florida might have been much like the lower Mississippi Delta today — rich farmland with an abundant supply of fresh water.

Directly above the layers of mud is a layer of what Pitman calls "shell hash" — an inch-thick layer of broken shells — overlain by several feet of fine sediment of the type being brought into the Black Sea by rivers today. The shells in the "hash" are typical of what was in the Black Sea when it was a body of fresh water. The fine sediments contain evidence of saltwater species previously unknown in the Black Sea. It is the interpretation of these layers that tells us what happened on that inevitable day when rising sea levels in the Mediterranean reached the base of the sediments at the bottom of the Bosporus — and all hell broke loose.

When the Mediterranean began to flow northward, it "popped the plug" and pushed those sediments into a "tongue" of loose sediment on the bottom of what would become the present-day Black Sea (this tongue can still be seen in cores taken from the ocean bottom in that area). As the flow of water increased, it began to cut into the bedrock itself. The rock in this area is broken — Pitman calls it "trashy" — and even today rockslides are a major engineering problem for roads cut into the cliffs alongside the Bosporus. The incoming water eventually dug a channel more than 300 feet deep as it poured into the Black Sea basin, changing it from a freshwater lake to a saltwater ocean. In this scenario, the mud beneath the shell hash represents sediments from the rivers that fed the freshwater lake, the shell hash the remains of the animals that lived in that lake, and the layers above it the result of the saltwater incursion.

It was this event that Pitman and Ryan believe could be the flood recorded in the Book of Genesis. The salt water poured through the deepening channel, creating a waterfall 200 times the volume of Niagara Falls (anyone who has ever traveled to the base of the falls on the Maid of the Mist will have a sense of the power involved). In a single day enough water came through the channel to cover Manhattan to a depth at least two times the height of the World Trade Center, and the roar of the cascading water would have been audible at least 100 miles away. Anyone living in the fertile farmlands on the northern rim of the sea would have had the harrowing experience of seeing the boundary of the ocean move inland at the rate of a mile a day.

In addition, Pitman and Ryan point out what archaeologists who study ancient civilizations have known for a long time: that at roughly the time of the flood, a number of people and new customs suddenly appeared in places as far apart as Egypt and the foothills of the Himalayas, Prague and Paris. The people included speakers of Indo-European, the language from which most modern European and Indian languages are derived. Pitman and Ryan suggest that these people might, in fact, represent a diaspora of Black Sea farmers who were driven from their homes by the flood, and that the flood itself might have been the cause of the breakup of Indo-European languages.

Unfortunately, the evidence for this diaspora is a good deal less solid than the evidence for the flood itself. Linguists have long known how to reconstruct ancient languages by looking at words that have survived in the descendants of those languages today. The date of an event like the split-up of the Indo-European languages can then be estimated by comparing those words with artifacts found in excavations — a language probably won't have a word for "wheel," for example, unless it actually uses wheeled vehicles. "It is unlikely that the Indo-European languages split up before 3500 B.C. (that is, 2,000 years after the Black Sea flood)," says University of Chicago linguist Bill Darden, basing his conclusion on this sort of argument. If he and his colleagues are right, then the diaspora part of the flood story will be just another beautiful theory shot down by ugly facts.

Walter Pitman accepts that there is controversy on this part of his thesis, but can't resist one final irreverent geologist's observation: "When you look at the settlements those people built," he says, "not one of them is less than 150 feet above sea level!"

## Valles Marineris formation

Over the years, scientists have proposed a number of theories about the formation of Valles Marineris. Erosion during a water-rich past and the withdrawal of subsurface magma were both early possibilities.

Today, most scientists think that the formation of the Tharsis region may have helped the canyon to form. The Tharsis region contains several large volcanoes that dwarf those found on Earth, including Olympus Mons.

As molten rock pushed through the volcanic region to form the monstrous volcanoes 3.5 billion years ago, the crust heaved upward. The strain cracked the crust, causing large faults and fractures across the planet's surface. Such fractures, growing over time, birthed the enormous canyon system.

The spreading cracks caused the ground to sink and opened an escape for subsurface water. The upward rushing liquid broke down the edges of the fractures, enlarging them and washing away more of the ground while flowing past.

Signs of flooding are especially apparent at the eastern end, in the mesas and hills known as chaotic terrain. Rushing water poured through channels into the lowlands, carving a series of channels. Scientists do not yet know whether the flooding took place over a short span of time, or whether one overwhelming flood was accompanied by several smaller flooding events.

At the same time, canyons were slowly widened over smaller scales as seeping groundwater carried rock and sediment away in smaller quantities. Landslides also helped to enlarge the features, sometimes traveling as far as 60 miles (100 km). Lava flows and ash falling from the nearby volcanoes may also have played a role in forming the intricate feature.

Glaciers probably helped with the carving. Signs of acid-rock interactions in Valles Marineris suggest that giant ice formations may have helped to carve at least some of the extensive network of channels. Deposits of the mineral jarosite suggest formation by ice rather than by puddles of water.

"Jarosite is usually considered an evaporative mineral: it forms from acidic water that is evaporating," lead author Selby Cull, of Bryn Mawr College in Pennsylvania, told Space.com.

"Getting an evaporating pool of water halfway up a 3-mile-high cliff is tricky, and the more we looked into the geologic context surrounding the deposit, the less likely a liquid water origin seemed."

The large canyon system was discovered in 1972 by its namesake, NASA's Mariner 9 spacecraft, the first satellite to orbit another planet.

## [5.5] FUTURE PLANETARY AEROBOT MISSION CONCEPTS

* While the French were working on planetary aerobots, NASA's Jet Propulsion Laboratory (JPL) had become interested in the idea as well, with a JPL team performing several balloon flights in the Earth's atmosphere during the 1990s to validate technology. The JPL team envisioning a simple "Mars weather balloon" to validate the technology operationally to be followed by a large superpressure balloon flight and finally a solar-powered Mars blimp. A company named Global Aerospace Corporation performed an investigation of a Mars aerobot for NASA, with the aerobot envisioned as carrying both a science gondola and a set of small drop probes that could be released to provide detailed inspection of a number of sites.

JPL has also considered concepts for aerobots to explore planets other than Mars. One Venus aerobot concept involved a balloon that would drop surface probes. Another Venus aerobot concept involved a reversible-fluid balloon, filled with helium and water, that could occasionally drop to the surface of Venus to pick up samples, with the balloon rising to the heights again and launching the samples on a small rocket for pickup by a orbiter and transfer back to Earth. The high pressures and temperatures near the surface, as well as the sulfuric-acid-laced clouds of Venus, makes this a challenging idea.

More recently, researchers at the NASA Langley center in Virginia have tinkered with the concept of an airship with a crew of two, the scheme being designated the "High Altitude Venus Operational Concept (HAVOC)". Under HAVOC, a robot airship would be sent as a precursor mission, followed by a crewed mission. The crewed airship would be dispatched on one spacecraft, with the crew on another, with two crew riding the airship down into the Venusian atmosphere for deployment. They would remain above the clouds, where the temperature and pressure are relatively benign, dropping probes to the surface that might include tele-operated systems.

When done with the mission, the crew component of the airship would boost into Venus orbit, to rendezvous with the orbiting spacecraft for a voyage back home. The idea is interesting -- it is easier to get to Venus than to Mars -- but it is not entirely clear how much advantage it would have over performing tele-operated studies from Venus orbit.

Titan, the largest moon of Saturn, is an attractive target for an aerobot mission, since it has a nitrogen atmosphere twice as dense as Earth's atmosphere that contains a smog of organic photochemicals, hiding the moon's surface from view by visual sensors. An aerobot would be able to penetrate this haze to study the moon's mysterious surface and search for complex organic molecules.

JPL's concepts for a Titan aerobot have included a hydrogen balloon, with the hydrogen extracted from methane in Titan's atmosphere a superpressure balloon that would drift until it found an interesting site and then vent itself to drop a payload onto the moon's surface a reversible-fluid balloon that would be able to travel from site to site and, most recently, a montgolfiere balloon. The montgolfiere is now seen as the best option, since in the cold atmosphere the montgolfiere would be able to float on the waste heat of an atomic radioisotope generator used to power the payload, and the fact that hot air balloons are much more tolerant of leaks than other configurations would allow the Titan balloon to float for years.

A powered airship would be very attractive for cruising around Titan, and JPL engineers have been flying small, commercially-available radio-controlled blimps to test out control systems. One particularly ingenious concept explored by JPL, the "Titan Aerover", combined aerobot and rover. This vehicle featured a triangular frame that connected three balloons, each about two meters (6.6 feet) in diameter. After entry into Titan's atmosphere, the aerover would float until it found an interesting site, then vent helium to descend to the surface. The three balloons would then serve as floats or wheels as necessary. JPL built a simple prototype that looked like three beachballs mounted on a tubular frame.

No matter what form a Titan aerobot mission takes, it will likely require an atomic-powered radioisotope thermoelectric generator (RTG) module for power. Solar power would not be possible at Saturn's distance and under Titan's smog, and batteries would not provide adequate power storage. The aerobot would also carry a miniaturized chemical lab to search for complicated organic chemicals.

* Finally, JPL considered aerobots to explore the atmosphere of Jupiter and possibly the other gaseous outer planets. Since the atmospheres of these planets are largely composed of hydrogen, the lightest gas, such an aerobot would necessarily be a montgolfiere. Sunlight is weak at such distances and so the aerobot would obtain most of its heating from infrared energy radiated by the planet below.

A Jupiter aerobot might operate at altitudes where the air pressure ranges from one to ten atmospheres, occasionally dropping lower for detailed studies. It would make atmospheric measurements and return imagery and remote sensing of weather phenomena, such as Jupiter's Great Red Spot. A Jupiter aerobot might also drop sondes deep into the atmosphere, with the sondes relaying their data back to an orbiter until they were destroyed by temperature and pressure.

## &lsquoOur Planet&rsquo film crew is still lying about walrus cliff deaths: here&rsquos how we know

Last week, I called “contrived nonsense” on the claim by David Attenborough and the production crew of Netflix’s ‘Our Planet’ that the walruses they showed falling to their deaths were victims of global warming. After unbelieveable media attention since then, newly-revealed details only solidify my assertion. Something stinks, and it’s not just the bad acting of director Sophie Lanfear in the ‘Behind the Scenes‘ trailer as she delivers her WWF-approved message: “This is the sad reality of climate change”.

Despite many statements to the press, the film crew have steadfastly refused to reveal precisely where and when they filmed the walrus deaths shown in this film in relation to the walrus deaths initiated by polar bears reported by The Siberian Times in the fall of 2017.

I can only conclude, therefore, that the two incidents are indeed essentially one and the same: that the filmmakers, probably alerted by resident WWF employees at Ryrkaipiy, moved in after polar bears caused hundreds of walrus to fall to their deaths. The crew then captured on film the last few falls over the cliff as the walrus herd moved away from the haulout.

The lie being told by Attenborough and the film crew is that 200-300 walruses fell during the time they were filming, while in fact they filmed only a few: polar bears were responsible for the majority of the carcasses shown on the beach below the cliff. This is, of course, in addition to the bigger lie that lack of sea ice is to blame for walrus herds being onshore in the first place.

See my point-by-point analysis below and make up your own mind.

##### Background

Walruses dying in large numbers due to falls from cliff tops is not a new phenomenon associated exclusively with reduced sea ice and neither are enormous land haulouts of walrus mothers and calves. Historical documents recorded prior to the decline of sea ice prove this is true (Crockford 2014 and references therein Fischbach et al. 2016 Lowry 1985) and the US government does not consider them ‘threatened’ with extinction (MacCracken et al. 2017 US Fish & Wildlife 2017a,b).

As I’ve noted previously, there were disturbing similarities between the event they filmed in 2017 somewhere in “eastern Siberia” and one reported by The Siberian Times at Cape Kozhevnikov near the village of Ryrkaipiy (see photo below) sometime in early to mid-September 2017 in which several dozen polar bears spooked a small herd of about 5,000 walruses so badly that hundreds fell off the cliff to their deaths.

Walrus haulout at Cape Kozhevnikov near the village of Ryrkaipiy.

Locations mentioned in this post:

##### What we know

Details on these points in the footnotes:

• The location of the incident where hundreds of walrus fell to their deaths after a herd of about 5,000 walrus was spooked by polar bears, as reported in The Siberian Times, was Cape Kozhevnikov near the village of Ryrkaipiy in Chukotka. A similar incident involving polar bears and somewhat fewer walrus occurred in 2011 (see footnote 1). In 2007, a herd of about 40,000 walrus spent time here in the early fall and left behind an unknown number of dead that attracted polar bears, see WWF account here (pdf here).
• The location of the Netflix cliff shoot was Cape Kozhevnikov near the village of Ryrkaipiy and the date was 19 September 2017, see footnote 2.
• According to tweets made by cameraman Jamie McPherson, the crew of ‘Our Planet’ arrived in Chukotka to film walrus on 14 September 2017 and left on 26 October 2017.
• The location in the ‘Our Planet’ film of a beach where more than 100,000 walrus were hauled out was not Cape Kozhevnikov near the village of Ryrkaipiy, see footnote 3: it may have been Cape Serdtse-Kamen, several hundred km east of Cape Kozhevnikov (map above), a known haulout area for super-herds of >100,000 walrus, see footnote 1.
• I was not the only scientist to question the filmmakers explanation of what was happening on the cliff: Lori Quakenbush from the Alaska Department of Fish and Game also found the films claims were scientifically dubious, see footnote 3. at the time the film footage was being shot, as ‘Our Planet’ director Sophie Lanfear has admitted.
• Low-altitude aerial footage shown in the film and the “Behind the Scenes” trailer (see footnote 4, at about 1:06) suggests the crew were using drones during the filming, which may have further aggitated the walrus massed at the top of the cliff while the rest of the herd was preparing to depart the haulout.
• Walrus have poor eyesight and the calls of walrus in the water as they left the haulout below may have caused those at the top of the cliff to move towards the edge where a misstep would have been fatal, even without being frightened.
• ‘Our Planet’ director Sophie Lanfear clarified in the ‘Behind the Scenes‘ trailer (see footnote 4) that the walruses they filmed were falling off the cliff because the herd was leaving the haulout.
• The polar bear initiated event reported after the fact in The Siberian Times at 19 October 2017 must have happened in early to mid-September, in any case before 19 September when the film footage was shot as the herd was moving out.
• Critically, “several hundred” walruses were stated to have fallen to their deaths during the polar bear initiated carnage at Cape Kozhevnikov in September 2017.
• ‘Hundreds of walruses’ were also claimed to havefallen to their deathsduring filming of the ‘Our Planet’ sequence (quote from Attenborough in the film).
• There’s probably 200-300 dead walrus on like a half mile stretch of beach here” [shown at the bottom of the cliff, after the crew shot the falling walruses] said cameraman Jamie McPherson in the ‘Behind the Scenes‘ trailer, see footnote 4.
• If there were two separate events of 200-300 walruses falling off that cliff (only one of which involved bears), McPherson should have recorded almost 600 carcasses on the beach below the cliff as the herd left the haulout. But he did not.
##### Conclusion

We know the ‘Our Planet’ film crew were in Chukotka by mid-September, perhaps at Cape Serdtse-Kamen, preparing to film a huge walrus haulout. I suggest that after polar bears frightened 200-300 walruses over the cliff to their deaths at Cape Kozhevnikov in early to mid-September, the film crew were alerted by WWF employees stationed at Ryrkaipiy about the incident.

The film crew temporarily moved to Cape Kozhevnikov and proceded to shoot footage of perhaps several dozen more walruses falling of the cliff onto the 200-300 carcasses already present at the bottom, as the herd prepared to move off due to the disturbance. The number of falling walrus may have been exacerbated by the use of drones and/or human activity around the haulout, but seem mostly to have been missteps taken by aggitated animals eager to join their fellows in the water. I suggest further that polar bears trying to feed on the carcasses were temporarily chased away by the WWF polar bear patrol before the crew began filming, which is why they had people watching to alert them should the bears return.

The lie being told by Attenborough and the film crew is that 200-300 walruses fell during the time they were filming, while in fact they filmed only a few: polar bears were responsible for the majority of the carcasses on the beach below the cliff. This is, of course, in addition to the bigger lie that lack of sea ice is to blame for walrus herds being onshore in the first place.

The crew and WWF can show I’m wrong by providing evidence of where the Netflix film footage was shot, where the haulout of >100,000 walrus was located, and the date in 2017 when the polar bear initiated walrus deaths at Cape Kozhevnikov occurred. If so, I will amend this post accordingly.

##### Footnotes

1. From ‘Pacific walrus coastal haulout database, 1852-2016 (see also Fischbach et al. 2016):

Cape Schmidt [Ryrkaipii Ryrkaipiy Mys Shmidta Cape Kozhevnikov Utios Kozhevnikov], with records of ‘at least 10,000, less than 100,000’ walrus in haulouts

Haulout Description: Rocky slopes and beach on eastern both sides of the Utios Kozhevnikov cliffs and adjoining spit 700 meters north of the settlement of Ryrkaipii. “Utios Kozhevnikov” is official name from Russian geographical maps and is part of Cape Schmidt. Another settlement, Cape Schmidt, lies 4 km to the east of this haulout. “Ryrkaipiy” means the “limit of walrus moving” in the Chukchi language.

Historical Use: Arsen’ev (1927) noted Cape Schmidt as a large haulout in the end of 19th century or begin of the 20th century. During the early 1930’s a large urban settlement was built near the site of the haulout, which may have contributed to the lack of observed haulout use until Kavry and others (2008) note the formation of a large haulout of more 40,000 walruses in September of 2007 (Kochnev 2012). Thereafter (2007 -2014), regular use has been reported, though not every year, with counts approaching 50,000 (Semenova and others 2010, Kochnev 2012, Pereverzev and Kochnev 2012, Maksim Deminov written communication and photograph 2014).

The haulout has been used by both adult males and by females and young, with the females and young replacing the adult males on the haulout as the season progresses from August through October (Semenova and others 2010, Pereverzev and Kochnev 2012). Overall, the age-sex composition is about 10% male, similar to the Wrangel Island haulouts. During the 2011 haulout large number of walruses of calves of the year and older age classes of both sexes were found dead (n = 123), and the deaths were attributed to both trampling and falls down steep rocking slopes, with polar bears playing a role (monrintoing [sic] support provided by TINRO and ChukotTINRO, Pereverzev and Kochnev 2012, Kochnev 2012).

Cape Serdtse-Kamen: with records of ‘more than 100,000’ walrus in haulouts [this is the only one in the database]

Haulout Description: Prominent cape Location 110 km northwest of the Bering Strait. Map location is center of haulout by mouth of river, 5 km southwest from the cape. During peak usage, the haulout extends over approximately 30 km of coastline from the cape to the southeast (Kochnev 2010b).

Historical Use: Use prior to 1927 is noted by Arsen’ev (1927). Nikulin (1941) noted use by walruses in 1937. Regularly use by walruses in ice-free autumns during all of the 20th Century up to the present (Belopl’skii 1939, Grachev and Mymrin, 1991 Zheleznov-Chukotsky and others, 2003 Kochnev, 2010b, unpublished data).

Use was noted during the 1960, 1964, 1975, 1980, 1985, 1990 aerial surveys (Fedoseev, 1966 Gol’tsev, 1968 Fedoseev, 1981 Estes and Gol’tsev, 1984 Fedoseev, Razlivalov, 1986 Gilbert and others 1992). In early October of 1975 Estes and Gol’tsev (1984) used extrapolation from aerial and density estimates to enumerate between 9 and 12 thousand walruses. The 1990 aerial survey indicated more than 12 thousand walruses on 30 September (Gilbert and others, 1992).

Estimates from 97,000 to 115,000 walruses of mixed age and sex classes are noted in October of 2009 and 2011 (Kochnev, 2010b Chakilev and others, 2012 Kochnev 2012). Residents from Enurmino and Inchoun indicated that the exceptionally large haulout documented during 2009 and 2011 may have formed similarly large in the years of sea ice scarcity prior to the 2009 monitoring effort (Kochnev, 2010b). During the 2011 monitoring effort, mortalities (n=120) attributed to trampling was noted that disproportionately affected younger animals (Kochnev 2012).

2. Andrew Montford has explained that images of the jagged cliff face from the film match perfectly with archived photos of the cliff face of Cape Kozhevnikov near the village of Ryrkaipiy (at Cape Schmidt) near the village of Ryrkaipiy. Also, EXIF photo metadata show that the footage was shot on 19 September 2017.

3. ‘Our Planet’ director Sophie Lanfear admitted to Ed Yong at The Atlantic that footage from two different locations were spliced together in the walrus film, perhaps giving the impression that the cliff haulout was part of the beach where over 1000,000 walruses were hauled out. She has so far refused to say which beach haulout they used for filming, but it is clear from remarks shared with various news outlets that the crew spent the majority of seven weeks at that location [my bold].

“…the seven-person Our Planet team filmed one of the largest haul-out sites—a single beach where 100,000 walruses tessellate into a solid red mat of tusks and blubber. The animals arrived almost overnight, while the team slept in a cramped hut. …

The walruses gather “out of desperation, not out of choice,” David Attenborough says over the resulting footage. “A stampede can occur out of nowhere. Under these conditions, walruses are a danger to themselves.” And so they climb “to find space away from the crowds.”

As the walruses spread across the beach, some start heading up a shallow slope, which curves into a steeper escarpment, which eventually culminates in 260-feet cliffs.

…Our Planet draws a straight line between climate change, sea-ice loss, bigger haul-outs, overcrowding, climbing walruses, and falling walruses. “It is not a normal event,” says Lanfear. “It’s such a tangible, obvious thing to show people. It’s clear as day.”

…Lanfear clarifies that the sequence includes footage from two separate beaches—one with the 100,000-strong congregation and one with the falls. At the latter, walruses started climbing only once the area beneath the cliffs had completely filled up gregarious or not, they had no room. Once at the top, they rested for a few days, and walked off only after the beaches below had emptied. Indeed, as the narration suggests, the sounds of their departing comrades may have lured the cliff-top walruses off the edge. “They seemed to all want to return to the sea to feed as a group,” Lanfear says.”

The haulout beach may have been Cape Serdtse-Kamen, several hundred km east of Cape Kozhevnikov, the only location within the range of Pacific walrus that haulouts of >100,000 animals have been recorded (Fischbach et al. 2016 database, see footnote 1). Such large herds were documented in 2009 and 2011, making it an attractive location for filmmakers intent on dramatic footage of heaving masses of walrus.

Also, according to The Atlantic I was not the only scientist to question the filmmaker’s interpretation of what was happening on the cliffs:

But a few walrus scientists who saw the clip have questioned parts of this narrative—including the claim that walruses are climbing “to find space away from the crowds.”

“Walruses thrive on crowds and haul out in tight groups, even when space is available,” says Lori Quakenbush from the Alaska Department of Fish and Game.

Also, in the sequence, it looks as if the beach beneath the teetering walruses is relatively empty. What crowds are they escaping from?

4. ‘Behind the Scenes’ trailer:

##### References

Crockford, S.J. 2014. On The Beach: Walrus Haulouts are Nothing New. The Global Warming Policy Foundation Briefing 11, London. Also available here

Fischbach, A.S., Kochnev, A.A., Garlich-Miller, J.L., and Jay, C.V. 2016. Pacific walrus coastal haulout database, 1852–2016—Background report: U.S. Geological Survey Open-File Report 2016–1108. http://dx.doi.org/10.3133/ofr20161108. The online database is found here.

Lowry, L. 1985. “Pacific Walrus – Boom or Bust?” Alaska Fish & Game Magazine July/August: 2-5. pdf here.

MacCracken, J.G., Beatty, W.S., Garlich-Miller, J.L., Kissling, M.L and Snyder, J.A. 2017. Final Species Status Assessment for the Pacific Walrus (Odobenus rosmarus divergens), May 2017 (Version 1.0). US Fish & Wildlife Service, Anchorage, AK. Pdf here (8.6 mb).

US Fish and Wildlife Service 2017a. Press Release (4 October 2017).

US Fish and Wildlife Service 2017b. Endangered and threatened wildlife and plants 12-month findings on petitions to list 25 species as endangered or threatened. Federal Register 82:46618-46645.