Why Do Sharks Eat So Many People?

“Dad?” my son asked as we got out of the car. “Why do sharks eat so many people?”

I assume he’d seen something about sharks at school, but the question still came out of nowhere. Thirty seconds before, he’d been telling me about his school’s Mardi Gras party and asking me if I felt better (because I’ve been sick, which is why this article still isn’t looking at the fossils he found). So, I put my mind to it. “I don’t think they do,” I answer.

“They don’t eat people?” he responds, sounding skeptical.

“Well, they can,” I concede. “But they don’t eat people all that often.”

“Why not?” he asks, and I swear he sounds disappointed.

“Well, a lot of them are kind of small. And we aren’t the kind of things they normally hunt.” I’m trying to remember shark facts, now. “Most of them are probably just wondering what we are, and people get scared of them and think they’re attacking.”

“Why do people get scared?” he asks.

I shrug. “Why did you get scared of them, when we went to the aquariam?”

“Because they look mean!” Then he grabs my hand. “Since you’re not feeling good, can we take a break and play Star Wars?”

Do sharks eat a lot of people?

This is one of those questions where I really hope I told my son the right thing, because I was working from half-remembered articles I’d read years ago, and memory is a fickle, tricky thing. Fortunately, it turns out that the University of Florida maintains the International Shark Attack File (ISAF), which they describe as “the longest running database on shark attacks, has a long-term scientifically documented database containing information on all known shark attacks, and is the only globally-comprehensive, scientific shark attack database in the world”.

Before we dive into the numbers, though, it’ll be important to define two terms the ISAF uses: provoked attacks and unprovoked attacks.

  • An unprovoked attack is edfined as “incidents where an attack on a live human occurs in the shark’s natural habitat with no human provocation of the shark.”
  • A provoked attack, on the other hand, usually occurs “when a human initiates physical contact with a shark, e.g. a diver bitten after grabbing a shark, attacks on spearfishers and those feeding sharks, bites occurring while unhooking or removing a shark from a fishing net, etc.”

The ISAF reports that 2016 was a pretty typical year, with a total of 150 alleged shark attacks. Out of those 150 attacks, here’s how the results broke out:

  • 81 were classified as unprovoked attacks (53 total in the United States, 43 of which were in Hawaii).
  • 37 were classified as provoked attacks.
  • 12 were sharks biting boats (aka “boat attacks”).
  • 1 was a shark eating part of an already dead human cadaver.
  • 12 had insufficient evidence to prove a shark attack.
  • 7 were determined to be attacks by other marine animals (including a barracuda and an eel).
  • 5 were determined to be abiotic injuries (that is, an environmental injury – scraping coral or rock, for instance).

So, in the fairly typical year of 2016, there were 118 total shark attacks on humans (131 if you count the boat attacks and the scavenging). 2015, by contract, hit 98 unprovoked shark attacks- the highest yearly total on record. On average, shark attacks result in 6 to 8 fatalities per year (depending on what period of time you average out), but 2016 only had 4 shark attack fatalities. Statistically, surfers are most likely to be attacked 958% of the total), followed by recreational swimmers and waders (32.1% of the attacks).

That’s not a lot of attacks, is it?

No, not really. In fact, there’s a whole lot of animals that are much more likely to kill you. According to the BBC, venomous snakes kill an estimated 50,000 people each year, rabid dogs kill an average 25,000 people each year, crocodiles kill an estimated 1,000 humans per year, and hippos kills an estimated 500 people per year. All of which makes the paltry 6-8 shark kills each year pretty tame.

friendly-shark

Still, it’s probably best not to do this unless you know what you’re doing.

The ISAF provides some other interesting comparisons. The odds of dying from a shark attack are 1 in 3,748,067. Fireworks are about 11 times more lethal (odds of death: 1 in 340,733), sun and heat exposure are 273 times more lethal (odds of death: 1 in 13,729), and the flu is 59,664 times more likely to kill you (odds of death: 1 in 63).

Why do shark attacks get so much attention, then?

Rarity, in my opinion. Rarity and shock/

See, we notice things that appear out of the ordinary. According to the CDC, heart disease is the leading cause of death in the United States (614,348 deaths in 2014), followed by chronic lower respiratory diseases (147,101 deaths), accidents (136,053 deaths), stroke (133,103 deaths), Alzheimer’s disease (93,541 deaths), diabetes (76,488 deaths), and influenza and pneumonia (55,227 deaths). Most of those get no attention at all, unless they’re really spectacular or they happen to someone famous. But death by animal attack? That’s unusual, particularly in the United States. And particularly because we like to think we’re outside the food chain. Homo sapiens sapiens is, realistically, the ultimate alpha predator and one of the dominant environmental forces on the planet. It’s unsettling to be reminded that we’re still animals, and that we can still become prey.

Also, sharks inhabit an alien environment that we can only meaningfully visit with the benefit of technology. A wolf or bear attack happens on dry land, so the surroundings aren’t inherently hostile to us. But sharks? A shark could kill us with their own environment, even if the bite isn’t fatal. So, they seem frightening.

Just in case I am one of the unlucky ones, any tips?

Actually, yes. Here’s what the ISAF says: “If one is attacked by a shark, we advise a proactive response. Hitting a shark on the nose, ideally with an inanimate object, usually results in the shark temporarily curtailing its attack. One should try to get out of the water at this time. If this is not possible, repeated blows to the snout may offer a temporary reprieve, but the result is likely to become increasingly less effective. If a shark actually bites, we suggest clawing at its eyes and gill openings, two sensitive areas. One should not act passively if under attack as sharks respect size and power. “

Can They Hear Me In China?

“BOO!” my son yells, leaping out from a shrub.  And then he dissolves into a fit of laughter.

This is a game he likes to play, whenever he gets the chance.  As soon as we’d parked and he got out of the car, he ran up the sidewalk towards the front door of our condo.  And then he ducked back behind the hedge, lurking.  The game, now, is for me to walk towards the door.  Then he’ll jump out and shout “boo” and try to make me jump.

“Did you know I was there, daddy?” he asks.

Of course I did, I think.  You hide in the same place every time.  “Kind of,” I tell him.  “I guessed where you were.”

He blows that off.  “I was loud, wasn’t I?”

“Yes, you were,” I answer, unlocking the door.

“Was I loud enough for them to hear me in China?”

How Do We Hear?

Obviously, we hear with our ears.

howdowehear

Sound waves, which are really just pressure waves in the atmosphere, strike the outer ear and are channeled into the ear canal.  These pressure waves vibrate the eardrum, which in turn vibrates the bones of the inner ear (the malleus, the incus, and the stapes), amplifying the vibrations and transmitting them into the inner ear (or cochlea).  Hairs in the cochlea are stimulated by these vibrations, creating an electrical signal that transmits along the auditory nerve to the brain.

Yes, this is terribly simplified.

How Loud Are You?

Strictly speaking, “loud” is a matter of perception – the same pressure wave can result in different experiences of “loudness”.  However, this perception is tied to the intensity of the pressure wave, just as the perceived pitch of a sound is tied to the frequency of the wave.

wavy33b

A wave

Using the above image of a wave, the intensity is how high the peaks and how low the valley is – the higher the peak, the more intense the wave.  Another way to think of intensity is how much energy the wave carries – the taller the wave, the more energy (just like how bigger ocean waves hit harder than small ones).  Frequency, on the other hand, is how fast the wave moves – the closer together the peaks, the faster the wave moves and the higher the frequency.  Generally speaking, we perceive intensity as loudness (because the pressure wave hits the ear harder) and we perceive frequency as pitch (because the pressure wave stimulates the bones in the ear faster).

“Loudness” is measured in decibels (dB), because one decibel is the “just noticeable difference” in sound intensity for the human ear – assuming the pressure wave generated is in the 1,000 Hertz (Hz) to 5,000 Hz range we are best at hearing.  Every 10 dB represents multiplying the intensity of the pressure wave by 10 – that is, a 10 dB sound is 10 times more intense than a 0 dB sound, a 40 dB sound is 10,000 times more intense than a 0 dB sound, and a 100 dB sound is 10,000,000,000 times more intense than a 0 dB sound.

We generally can’t hear anything below 0 dB, and normally speak in the 60 to 65 dB range.  A jackhammer 50 feet away is about 95 dB, a power mower 3 feet away is around 107 dB, and loudness causes pain starting around 125 dB.  Sounds at 140 dB and greater can cause permanent damage with even short exposure.

How Far Away Can We Hear?

This gets tricky, because the answer is “no further than when the perceived volume falls to 0 dB”.  Tricky, because sound obeys the inverse square law which states that for any source power P generated at the center of a sphere, the intensity of at the surface of that sphere is P/4πr2 (although a good approximation is P/r2, since the math gets easier).  According to Hyperphysics, r is pretty much always measured in meters for these purposes (because sound intensity is actually measured in watts per meter squared, so it keeps the units the same).

Since sound intensity can be transformed into decibels, it’s really not a stretch to directly apply the inverse square law to decibel measurements.  So, a 60 decibel conversation would be perceived as 60 decibels at 1 meter away, 60/(2*2) = 15 decibels at 2 meters, 60/(3*3) = 6.6 decibels at 3 meters, 60/(4-4) = 3.75 decibels at 4 meters, less than 1 decibel at 8 meters, and so on.  Realistically, at this point, it’s probably safe to call it “inaudible” (even though you could technically detect it).

How Loud Would You Have To Be For Someone To Hear You In China?

All right, here’s where the math gets… entertaining.  I live in Cincinnati, Ohio, which is (according to Google) 10,969 kilometers from Beijing.  Measuring along the curved surface of the Earth, that is.  But, to keep things simple, we’ll ignore that.  So, 10,909 kilometers is 10,909,000 meters.  To be heard in Beijing, we’d have to generate enough decibels to result in a greater than 0 dB sound 10,909,000 meters away.

For laughs, let’s aim for a 60 dB sound.  That way, our sound can be clearly understood.  The radius is 10,969,000.  So, the equation looks like this:  x/10,969,0002 = 60.  Solving for x gives us x = 60(10,969,0002), or x = 7,219,137,660,000,000 dB.  This is a nonsensical level of perceived volume, and would render you deaf in ludicrously tiny fractions of a second.

What could generate that?  Well, we’d have to reverse engineer the decibels into watts of power, which converts to 721913765999988 watts per meter, or about 721.9 terawatts of power.  Now, you can roughly convert watts to Joules per second, so that’s roughly the explosion of a 200 kiloton nuclear weapon.

Assuming I did my math correctly, which I’m not guaranteeing.  What I can guarantee is that there is no way you’d want to be standing anywhere near something loud enough in Cincinnati that you can hear it in China.

Is It Medicine?

Recently, we were at our local “natural and health foods” store. While my wife shopped for a specific supplement she was advised to use, I got to ride herd on my energetic five year old as he roamed around the store looking at everything. He loved the posters over by the pet food section, one of which showed a lion with a lamb curled up against it. He thought that was amazing and cute. Nearby was an entire wall of homeopathic products, including an entire array of products for pets. My son stopped and looked at the boxes, then turned and looked at me.

“Is this all medicine?” he asked.

I didn’t really feel like tackling that subject right there in the store. Not in any detail, anyway. “No,” I said.

“Okay,” he answered, and then he was off to look at the selection of vegan, glutin free baked goods.

What is homeopathy?

According to the American Institute of Homeopathy:

Homeopathy, or Homeopathic Medicine, is the practice of medicine that embraces a holistic, natural approach to the treatment of the sick. Homeopathy is holistic because it treats the person as a whole, rather than focusing on a diseased part or a labeled sickness. Homeopathy is natural because its remedies are produced according to the U.S. FDA-recognized Homeopathic Pharmacopoeia of the United States from natural sources, whether vegetable, mineral, or animal in nature.

The website goes on to explain that there are three guiding principles of homeopathy:

  1. “Like cures like”. A principal that a symptom can be treated with a substance that causes a similar symptom.
  2. The minimum dose. From the AIH website, “Homeopathic medicines are prepared through a series of dilutions, at each step of which there is a vigorous agitation of the solution called succussion, until there is no detectible chemical substance left. As paradoxical as it may seem, the higher the dilution, when prepared in this dynamized way, the more potent the homeopathic remedy. Thereby is achieved the minimum dose which, none the less, has the maximum therapeutic effect with the fewest side effects.”
  3. The single remedy. Again, from the AIG website, “Most homeopathic practitioners prescribe one remedy at a time. The homeopathic remedy has been proved by itself, producing its own unique drug picture. That remedy is matched (prescribed) to the sick person having a similar picture. The results are observed, uncluttered by the confusion of effects that might be produced if more than one medicine were given at the same time.”

Is homeopathy medicine?

Merriam-Webster defines medicine as:

1 a: a substance or preparation used in treating disease
b: something that affects well-being

2 a: the science and art dealing with the maintenance of health and the prevention, alleviation, or cure of disease
b: the branch of medicine concerned with the nonsurgical treatment of disease

3: a substance (as a drug or potion) used to treat something other than disease

So. By some definitions of medicine it qualifies. Homeopaths are certainly involved in “the science and art dealing with the maintenance of health and the prevention, alleviation, or cure of disease” and homeopathic medicines are certainly “a substance or preparation used in treating disease”.

Does homeopathy work?

No.

Uhm… could you elaborate on that?

There’s no way it could work. Let’s take another look at that second principle of homeopathy, the minimum dose. The AIH states that “Homeopathic medicines are prepared through a series of dilutions, at each step of which there is a vigorous agitation of the solution called succussion, until there is no detectible chemical substance left.”

Here’s how the dilutions work, as explained by a FAQ from Boiron (described as a “world leader in homeopathic medicines”):

What does the “C” listed after the active ingredient stand for?

The most common type of dilutions is “C” dilutions (centesimal dilutions). The 1C is obtained by mixing 1 part of the Mother Tincture with 9 parts of ethanol in a new vial and then vigorously shaking the solution (succussion). The result is a 1/100 dilution of the plant (the Mother Tincture being a 1/10 dilution of the plant itself). The 2C is obtained by mixing 1 part of the 1C with 99 parts of ethanol in a new vial and succussing. Recurrently, the 3C is obtained by mixing 1 part of the 2C with 99 parts of ethanol in a new vial and succussing.

What does the “X” listed after the active ingredient stand for?
X dilutions are decimal dilutions prepared similarly to C dilutions, but the factor of dilution is only 1/10 from one dilution to the next.

What does the “K” listed after the active ingredient stand for?
The K refers to a method of manufacturing known as the Korsakovian method. The Korsakovian method dilutes the homeopathic preparation of the substance at the rate of 1 part of the previous dilution with 99 parts of solvent.

What does the “CK” listed after the active ingredient stand for?
Korsakovian dilutions are manufactured using a device specially designed to ensure that the dilution process is reproducible from one dilution to the next. Only one vial is used for the entire process. Using ultra-purified water as the solvent, the machine removes 99% of the Mother Tincture and replaces it with the same volume of solvent. The vial is succussed for 10.5 seconds. The result is called 1CK. The 2CK is prepared identically from the 1CK. The automatic process using only 1 vial allows higher dilutions to be reached. The most common Korsakovian dilutions are 200CK, 1,000CK (also called 1M), 10,000CK (10M), 50,000 CK (50M) and 100,000CK (100M or CM).

What does “200CK” mean?
200CK means that the substance has been homeopathically diluted 200 times at the rate of 1 to 100.

The dilutions on the medicines I looked at (I didn’t look at all of them) appear to range between 3C and 12C, counting by threes (3C, 6C, 9C, 12C), with one hitting 30C. Here’s what that looks like:

  • 3C: 1 part active ingredient to 9,999 parts solvent (100 parts per million, or PPM).
  • 6C: 1 part active ingredient to 9,999,999 parts solvent (0.1 PPM).
  • 9C: 1 part active ingredient to 9,999,999,999 parts solvent (0.0001 PPM).
  • 12C: 1 part active ingredient to 9,999,999,999,999 parts solvent (0.0000001 PPM).
  • 30C: 1 part active ingredient to 9,999,999,999,999,999,999,999,999,999,999 parts solvent (0.0000000000000000000000001 PPM)

For comparison, let’s talk about the US Environmental Protection Agency’s Maximum Containment Level Goals (MCLG), Maximum Contaminant Levels (MCL), and Maximum Residual Disinfectant Level Goals (MRDLG):

  • Maximum Contaminant Level Goal (MCLG) – The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety and are non-enforceable public health goals.
  • Maximum Contaminant Level (MCL) – The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to MCLGs as feasible using the best available treatment technology and taking cost into consideration. MCLs are enforceable standards.
  • Maximum Residual Disinfectant Level Goal (MRDLG) – The level of a drinking water disinfectant below which there is no known or expected risk to health. MRDLGs do not reflect the benefits of the use of disinfectants to control microbial contaminants.

With that in mind, let’s have a look at the EPA Table of Regulated Drinking Water Contaminants. If you go and look at it yourself, bear in mind that the units are in milligrams per liter (mg/L), which is equivalent to PPM:

  • Chlorine has a MCL of 4 PPM (effectively 4 5C dilutions).
  • Arsenic has a MCL of 0.01 PPM (meaning a 7C dilution)
  • Cyanide has a MCL of 0.2 PPM (two doses of a 6C dilution).
  • Lead has a MCL of 0.015 PPM (one and a half doses of a 7C dilution).
  • Mercury has a MCL of 0.002 PPM (two doses of an 8C dilution).

By sheer logic, if the “like cures like” principal was correct and the minimum dose worked, then we’d be immune to eye/nose irritation and stomach discomfort (caused by chlorine), circulatory system problems (arsenic), nerve damage and thyroid problems (cyanide), developmental development issues and kidney problems (lead), and kidney damage (mercury).

Moles and atoms and molecules

Let’s put it a different way, and talk about moles.

mole6

No, not these guys

A mole is the SI unit of that measures the amount of a chemical substance that contains as many elementary entities (atoms, molecules, whatever) as there are atoms in 12 grams of carbon-12. This odd calculation is used because the number of atoms in 12 grams of carbon-12 happens to be the same as the Avogadro constant: 602,214,085,774,000,000,000,000.

Why is this important? Watch, and see.

A homeopathic “mother tincture” is 10% ingredient and 90% solvent, by weight. So a mother tincture of peppermint would be, say, 1 gram of peppermint oil and 9 grams of water. The active ingredient of peppermint oil is menthol (C10H20O), and water is H2O. Consulting the Lenntech molecular weight calculator, menthol has a weight of 156.26 grams per mole and water weighs 18.02 grams per mole. So one gram of menthol has 3,853,923,497,849,737,616,792 molecules of menthol, and one gram of water has 33,419,205,647,835,738,068,812 molecules of water. So the mother tincture has a total of 304,626,774,328,371,380,236,100 molecules, and is only 1.2% menthol by quantity of atoms (despite being 10% menthol by weight).

A 1C dilution takes 1 gram of the mother solution and mixes that with 99 grams of water, giving us 100 grams of dilution with a total of 3,338,964,036,568,570,000,000,000 molecules, of which 385,392,349,784,973,000,000 are menthol.  That makes it 0.0115% menthol at this point.  Each dilution after that reduces the number of menthol atoms by a factor of 100, until at a 12C dilution you get 3.85 atoms (let’s be optimistic and call it 4).  So, at a 13C dilution, you quite literally have nothing but water.

Homeopathic-Dilutions_thumb18-621x210

Bear in mind that this is the case with a relatively simple molecule like menthol.  Most of the “active ingredients” in homeopathic dilutions are far more complex – according to Chemical composition, olfactory evaluation and antioxidant effects of essential oil from Mentha x piperita, for example, the components of peppermint essential oils were “menthol (40.7%) and menthone (23.4%). Further components were (+/-)-menthyl acetate, 1,8-cineole, limonene, beta-pinene and beta-caryophyllene”.  This reduces the number of atoms per gram of each ingredient, causing the atoms of each chemical that make up the ingredient to go away faster (although in the case of the peppermint essential oils, menthone’s molecular weight is 154.25 grams per mole, so you’d end up with about 2 atoms each of menthol and menthone at a 12C dilution).

So, is homeopathy medicine?  Only in a strict and narrow definition, because it is used to treat illnesses.  After all, the definition we looked at above doesn’t say the medicine has to work.  And it really doesn’t work.

Why Is It Called A Saber-Tooth Tiger?

Every shirt my son has is his favorite shirt. I know this, because he’ll tell me. “I’m wearing my Star Wars shirt! It’s my favorite!” he’ll declare. Then, the next day, he’ll say “Mario! It’s my Mario shirt! It’s my favorite!” He’s five. He’s allowed to have multiple favorites. One of the shirts is a long-sleeved shirt with a panther on it, a shirt that I think is a team shirt for some sport or another. But that’s not why he likes it. No, he likes it because he has declared it his “saber-tooth tiger shirt”.

One day, he’s wearing that shirt and we’re watching Walking with Beasts on DVD. We hit the episode with the saber-tooth, and he gets excited. Perking up, he announces “It’s a saber-tooth!” Then he tugs on his shirt to display the panther. “It’s my saber-tooth!”

I grin at that, and keep watching. He settles back, watching wide-eyed. And then he turns to me. “Why is it called a saber-tooth?” he asks.

To be honest, the answer to the question is “because they have big, curving fangs”.

sabertooth skullLike these.

But it got me thinking about the things I don’t know about saber-tooth tigers. Particularly because of another question he asked me: “Are saber-tooths the ancestors of cheetahs and jaguars?” That, I don’t know. I think I’ve read that they’re not particularly closely related to modern cats, but I couldn’t tell you where I heard or read that or how accurate it is.

Saber-Toothed Animals

To start with, it turns out that “saber-teeth” isn’t exclusive to cats. Saber-teeth has convergently evolved in several different species. UC Berkeley’s “What is a Sabertooth?” article states that “[t]he sabertooth morphology has appeared several times during the history of the mammals”, within true cats, within two extinct carnivore families (Nimravidae and Hyaenodontidae), and among the South American marsupials called thylacosmilids. Wikipedia gets a little more specific, listing six known appearance of saber-teeth:

  • Gorgonops, a (large) dog-sized therapsid (or “mammal-like reptile”) that lived between 260 and 254 million years ago.
  • Thylacosmilus atrox, a (large) dog-sized metatherian (ancestor of the pouched mammals, including marsupials) that lived from the late Miocene to late Pilocene (about 11.6 to 2.6 million years ago).
  • Machaeroides eothen, a Terrier-sized predatory mammal that may have been a Hyaenodontidae (not closely related to Hyaenas, despite the name) that lived in Wyoming during the Eocene (56 to 34 million years ago).
  • Hoplophoneus primaevus, a North American Nimravidae (an extinct family of cat-like carnivores) that lived 38 to 33.8 million years ago.
  • Barbourofelis fricki, another Nimravidae that lived in North America from 13.6 to 5.3 million years ago.
  • Smilodon, the famous Saber-Toothed Tiger.

Could one of these animals be the ancestors of cheetahs and jaguars?

Cheetahs are Acinonyx jubatus, and are native to eastern and southern Africa and parts of Iran. Jaguars are Panthera onca, and are native to South and Central America, and the southwestern United States. Both are part of the Felidae family, but the cheetah belongs to the Felinae subfamily and the jaguar belongs to the Pantherinae subfamily. This rules out Thylacosmilus, Machaeroides, Hoplophoneus, and Barbourofelis for a few reasons – first of all, Metatherians, Hyaenodontidae, and Nimravidae are not part of Felidae. So, although they have a common ancestor, none of those animals are ancestors of any Felidae species.

Gorgonops isn’t an ancestor of cheetahs and jaguars either. The family Gorgonoopsidae is part of the Suborder Gorgonopsia, which is part of the Theriodontia group. Mammals also belong to the Theriodontia group, but fall under Suborder Cynodontia. Which is a complicated way of saying that cheetahs and jaguars and Gorgonops all have a common ancestor, but one isn’t the ancestor of the other.

But what about Smilodon?

Smilodon

There are actually three known species of Smilodon: Smilodon fatalis, Smilodon gracilis, and Smilodon populator. S. populator was the largest (about the size of a modern lion) and S. gracilis was the smallest. As a genus, Smilodon lived in North and South America from 2.5 million to 13 thousand years ago, with S. fatalis being the last of the three species to go extinct – meaning that humans may have overlapped with the last of the Smilodons. Smilodon is a genus within the Machairodontinae subfamily of family Felidae, so they are true cats.

Despite being true cats, they weren’t the ancestors of cheetahs or jaguars. Not in any meaningful sense, anyway. First of all, they were in the wrong geographic area to be the ancestors of cheetahs – you know, with cheetahs in Africa and Smilodon in North and South America. Their range did overlap with the jaguar (or, at least, with the jaguar’s ancestors), but they really aren’t the ancestor of jaguars. As mentioned, jaguars are part of the Pantherinae subfamily of Felidae. Smilodon is part of the Malchairodontinae subfamily, so they have ancestors in common with the Pantherinae but aren’t otherwise related.

This is not to say that Smilodon and the ancestors of jaguars couldn’t have mated. After all, much like Las Vegas, what happens in the wild stays in the wild. However, breeding two different species within the same genus often results in sterility, because the specific numbers of chromosomes may not match. Donkeys and horses, both family Euidae and genus Equus are an obvious example of this. The discrepancies are only magnified if you step up past genus to family.

Still, it could have happened. And it is possible (if not likely) that a single “jaguodon” could have managed to be born fertile. So quick, let’s do some math. A jaguar hits sexual maturity at age 2 and has 38 chromosomes. Smilodon fatalis went extinct about 13,000 years ago, so that’s 6,500 generations for the “jaguodon” and her descendants, which start at 50% Smilodon – so, 19 Smilodon chromosomes.  Assuming mama “jaguodon” breeds with a jaguar, her kittens have 9.5 Smilodon chromosomes, and 28.5 jaguar chromosomes.  This continues for the next, oh, call it 6,000 generations (we’ll assume a small degree of individual jaguars that happen to have Smilodon DNA breeding with other jaguars that happen to have Smilodon DNA).  That means that any given jaguar might have 38/26000 Smilodon chromosomes, which is 2.5 x 10-1805 chromosomes.  Which means that any given jaguar could be around this much Smilodon:

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Clearly, that’s not much Smilodon in your jaguar.  So, while the fearsome “saber-tooth tiger”could (in theory, at least) be an ancestor of a given jaguar, we don’t really need to worry about saber-toothed jaguars suddenly being born.

How Do You Get To Space?

We’ve got another contextless question here. Just the question “how do you get to space?” listed in my notes. I strongly suspect, though, that it has to do with my son’s current obsession with Star Wars. There’s a lot of space ships in those movies, after all, and he’s got a toy Millennium Falcon that he abuses in true five-year-old fashion. So he thinks about space – or at least movie “space” – a lot.

What Is Space?

Generally speaking, “space” is “outside Earth’s atmosphere”. Specifically, though, this gets problematic. There’s six different layers of the atmosphere, after all:

  • The troposphere, which averages about 7 miles (11 km) thick, and ranges from 8 km thick at the poles to 16 km at the equator. This is what most of us think of as “the atmosphere”, with breathable air and weather and most of clouds. The temperature drops with altitude in the troposphere.
  • The stratosphere, which sits on top of the troposphere and extends upwards to 30 miles (45 km) above the Earth’s surface. You find the ozone layer here, as well as temperature increasing slightly with altitude – up to a high of 32 degrees Fahrenheit (0 degrees Celsius).
  • The mesosphere, which sits on top of the stratosphere and extends upwards to about 53 miles (85 kilometers) above the surface. Temperature begins dropping with altitude again in this layer, reaching a low of -130 degrees Fahrenheit (-90 degrees Celsius), and it’s the atmospheric layer in which meteors begin to burn up as they fall towards Earth.
  • The thermosphere, which sits on top of the mesosphere and extends upwards to about 372 miles (600 kilometers) above the surface of the Earth. Temperatures can reach thousands of degrees (Celsius or Fahrenheit), but it’s measured in the energy of the molecules of gas in this layer and there’s not a lot of molecules that high up (the average molecule would have to travel 0.62 miles/1 kilometer to collide with another molecule), so it doesn’t feel hot.
  • The exosphere, which sits on top of the thermosphere and extends upwards to about 6,200 miles (10,000 km).
  • The ionosphere, which starts 30 miles (48 km) above the surface and stretches to 600 miles (965 km) above the surface. That’s an average figure, though, as it grows and shrinks based on solar conditions. It’s also divided into sub-regions, based on what wavelength of solar radiation it absorbs. Note that the ionosphere, although considered a seperate layer of the atmosphere, overlaps the mesosphere, the thermosphere, and the exosphere.

So, where’s space? The definition “outside Earth’s atmosphere” could mean that you have to exit the exosphere to be “in space”, but this would put us in the ridiculous position of having to consider the International Space Station (which orbits at an average height of 249 miles) within the atmosphere. Clearly, that’s ridiculous.

The commonly accepted altitude definition for space is the Kármán line, which is 62 miles (100 km) above sea level. This line, sitting in the lower reaches of the thermosphere, is approximately the altitude above which wings no longer provide lift and below which atmospheric drag makes orbital paths fail without forward thrust.

Ways to get to space

Clearly, then, to get into space “all” we have to do is travel at least 62 miles (100 km) straight up. Simple, right? Well, maybe not. At present, we have only a handfull of ways to leave the surface of the Earth: balloons, really big guns, rotor wing aircraft, fixed-wing aircraft, and rockets. Each has some advantages and disadvantages.

Balloons

For balloons, the current record-holder for unmanned flight is the Japanese BU60-1, which reached an altitude of 33 miles (53 km) and carried a 10 kg payload. The altitude record for a manned balloon was the StratEx, which reached an altitude of 25.7 miles (41.4 km). Both were impressive achievements, but neither made the Kármán line.

Balloons function because of Archimedes’ Principle:

When a body is fully or partially submerged in a fluid, a buoyant force Fb from the surrounding fluid acts on the body. The force is directed upwards has a magnitude equal to the weight, mfg, of the fluid that has been displaced by the body.

In other words, if an object is submerged in a fluid but is lighter than that fluid, the fluid pushes it up until the object it is the same weight as the surrounding fluid. And while we don’t tend to think of it in this fashion, our atmosphere behaves like a fluid. We don’t float in the air because we’re denser then the air. A balloon inflated with air doesn’t float, because it’s actually slightly more dense than the atmosphere (because you forced more air in to inflate the balloon). But balloons filled with hot air, or with a gas that is less dense than our atmosphere (hydrogen or helium, say) will float.

Because of this, you could theoretically float a balloon into space – all you need is for the balloon to be less dense than the surrounding environment, after all. There’s a catch, though. The material of the balloon needs to be strong enough to not burst if the interior is pressurized, strong enough not to be crushed by the denser exterior, and light – because the mass of the balloon is added to the mass of the interior to determine if Archimedes’ Principle will lift it. A vacuum would be the ideal interior, but so far we don’t have anything simultaneously strong enough to keep the atmosphere from crushing a vacuum balloon and light enough for the air to push it up.

Big Gun

Jules Verne proposed this in From the Earth to the Moon way back in 1865. All you need is enough power, and you can launch something (or someone) into space from the ground. How much power? Well, using a ballistic trajectory calculator and assuming that the projectile is fired straight up from sea level, you would need a muzzle velocity of 4,595.52 feet per second (1,400.715 meters per second) to launch something 100 kilometers into the air – ignoring the effects of atmospheric drag. If you’re curious, that’s 142.78 times the force of gravity.

This is clearly not a good way to put people into space, but it would work well for launching non-fragile items. And in 1966, Project HARP demonstrated that it would work. A 16-inch (and 119 feet long) gun constructed by the US Department of Defence in Yuma, Arizona fired a 165 pound shell 590,000 feet (179,832 meters) into the air on November 19, 1966 – that’s 111.74 miles (179.8 kilometers), putting it well past the Kármán line

Plane

Planes seem an obvious choice, right? We all know what they are, they take off and land, so why not fly into space? Well, there’s a good reason for that – the Kármán line (meaning that by the time you reach space your wings aren’t working) and the propulsion (both jets and propellers require air to function). So, any plane that could reach space would need to be a rocket as well as an airplane. Right now, the world altitude record for a airplane was set on August 31, 1977 by Alexander Fedotov, who reached 23.4 miles (37.66 kilometers) in a MiG-25.

Rocket

Right now, this is the way we get to space. A rocket engine carries stored fuel and utilizes Newton’s third law by expelling that fuel in one fashion or another from one end of the craft to push the opposite direction. Most rockets in operation are combustion rockets, meaning that the fuel is ignited and burned in some fashion. These can be quite expensive, as the rocket has to lift all of its fuel at the time of launch. However, with sufficient fuel and engineering and money, you can build a rocket capable of reaching any altitude.

Other Strategies

Any number of launch methods that do not rely on rockets have been proposed – the space gun technically is counted in this category, but it differs from the others in the fact that it has actually been constructed. Most of the others have a US Department of Defense technology readiness level of 2, meaning that they are dependent on the invention of the materials and technologies needed to support them, and may not actually be feasable. They include:

  • Space tower: a tower that reaches above the Kármán line, possibly as far as geosynchronous orbit (22,369 miles or 36,000 km).
  • Skyhook: A satellite that lowers a lift cable (or the equivalent) and then reels in the payload.
  • Space elevator: A tether attached to the Earth at one end and a geosynchronous satellite at the other, which can then allow vehicles to climb into space.

How do you stay in space?

To quote Randall Monroe, “getting to space is easy. The problem is staying there.” Why? Well, gravity is still pulling you down. So, you have to go ‘sideways’ fast enough that you keep missing the Earth as you fall (which is pretty much what an orbit is). Using the Earth Orbit Velocity calculator on Hyperphysics, an orbit at the Kármán line would require an orbital speed of 25,745.41 feet per second (7847.2 meters per second), which translates to 17,549.1 mph (28,249.64 kph).

Fortunately, you don’t have to maintain constant acceleration at that speed – one of the defining features of space is that it’s pretty empty, meaning there isn’t a whole lot out there to slow you down once you get going. But still, you have to get going really fast to stay there – orbiting at the Kármán line means you circle the earth every 1.45 hours.

How do you get back down?

Oh, that’s easy. You fall. Whether or not you die is a matter of how you land.

How Long Would It Take To Drive To The North Pole?

About a week ago, we’re in my car running a few errands. My son is chattering away, happily talking about how Winnie-the-Pooh didn’t really discover the North Pole because he was just pretending. (The Winnie-the-Pooh books are our current bedtime story, if you’re wondering.) Something about the combination of these two facts must have sparked what happened next.

“Dad? How long would it take to drive to the North Pole?”

“Magnetic, or true?” I counter.

“What?” he responds.

The Two Poles

There are two North Poles (and two South Poles as well), the “true” (or geographic) North Pole and the magnetic North Pole. And they do not really match up. So what’s the difference between the two of them? Here’s how National Geographic describes the North Pole:

The North Pole is the northernmost point on Earth. It is the precise point of the intersection of the Earth’s axis and the Earth’s surface.

The North Pole sits in the middle of the Arctic Ocean, on water that is almost always covered with ice. The ice is about 2-3 meters (6-10 feet) thick. The depth of the ocean at  North Pole is more than 4,000 meters (13,123 feet).

275px-Arctic_Ocean
Here.

The magnetic North Pole is a little more difficult to pin down. Why? Well, let’s start by letting NOAA tell us what the magnetic poles are:

Magnetic poles are defined in different ways. They are commonly understood as positions on the Earth’s surface where the geomagnetic field is vertical (i.e., perpendicular) to the ellipsoid. These north and south positions, called dip poles, do not need to be (and are not currently) antipodal.

“Antipodal”, by the way, is your new word for the day. It means:

  1. Geography. on the opposite side of the globe
  2. diametrically opposite
  3. Botany. (in a developing ovule) of or at the end opposite to the micropyle

So why does the magnetic field move? Because it’s produced by the spinning of the Earth’s inner core – a solid iron ball almost as big as the moon and hotter than the sun that spins a little faster than the Earth’s crust in a massive sea of liquid (or, at least more liquid) metal called the “liquid inner core”. So far, so good. Right?

world-pr

Now, the full details of what generates the magnetic field are not understood – a fact that I’m certain makes scientists extremely happy. But, as Natural Resources Canada explains, we do understand the basic concepts:

For magnetic field generation to occur several conditions must be met:

  1. there must be a conducting fluid;
  2. there must be enough energy to cause the fluid to move with sufficient speed and with the appropriate flow pattern;
  3. there must be a “seed” magnetic field.

All these conditions are met in the outer core. Molten iron is a good conductor. There is sufficient energy to drive convection, and the convective motion, coupled with the Earth’s rotation, produce the appropriate flow pattern. Even before the Earth’s magnetic field was first formed magnetic fields were present in the form of the sun’s magnetic field. Once the process is going, the existing field acts as the seed field. As a stream of molten iron passes through the existing magnetic field, an electric current is generated through a process called magnetic induction. The newly created electric field will in turn create a magnetic field. Given the right relationship between the magnetic field and the fluid flow, the generated magnetic field can reinforces the initial magnetic field. As long as there is sufficient fluid motion in the outer core, the process will continue.

So why does it move? well, the magnetic field is created by a fast-spinning ball inside a slow-spinning ball. So it wobbles, at an average speed of 10 kilometers per year for the entire 20th century.

nmppath2001_med

So where is it right now? According to the World Data Center for Geomagnetism you’ll find it at 80.4° North, 72.6° west. Or, in other words, Nunavut, Canada.

Magnetic Pole
Right there

How long would it take to drive there?

According to the handy Computing Distances between Latitudes/Longitudes in One Step page, and checking the latitude and longitude of Cincinnati, Ohio (39.1000° N, 84.5167° W), I get the following figures:

  • Geographic North Pole: 3,524.64 miles
  • Magnetic North Pole: 4,144.18 miles

Now, looking at the map above, you would think that driving to either pole would be impossible. After all, there’s ocean in the way! But this is where living in Cincinnati comes in handy – we have a Ride the Ducks tour here!

duck boat

The “Duck Boat” is a World War II surplus DUKW, an amphibious vehicle capable of cruising at 35 mph (56 km/h) on roads and 4.41 mph (7.14 km/h) in the water with an operational range of 400 miles on land (or 58 miles/93 km in the water). I doubt it has the ring mount for the machine guns, though. So, we can do this. In theory, at least.

Eyeballing the map, I’m going to go with an estimate of 90% overland travel to the magnetic North Pole and 65% overland travel to the geographic North Pole. Further assumptions will be:

  • Driving 18 hours a day – my wife has agreed to go along with this mad idea, so we can drive quite a bit. But we still need to stop for bathroom breaks, meals, stretching our legs, and refueling.
  • We’ll be hitting our cruising speed.
  • We don’t get eaten by polar bears.
  • We’re not worrying about mountains.
  • We drive in a straight line, and we don’t get lost.

Getting to the geographic North Pole is roughly 2,291 miles over land and 1233.64 miles over sea. That’s (2,291/35) + (1233.64/4.41) = 345.19 hours. Based on our assumptions, that’s 19 days, 4 hours, 15 minutes. And we would have needed to stop for gas 27 times on the trip.

Getting to the magnetic North Pole is 3,729.762 miles over land and 414.418 miles over sea. That’s (3,729.762/35) + (414.418/4.41) = 200.54 hours. Based on our assumptions that’s 11 days, 3 hours, 23 minutes. And we would have needed to stop for gas 17 times.

Either way, we also get a complimentary duck whistle for the trip.  So my son is going to love this!