Dragons and white walkers aside, 'Game of Thrones' occasionally has some real science behind it

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• In "Game of Thrones," Old Nan speaks of the Long Night, a winter that lasted a generation. Not only is this possible, it happened in real life 20,000 years ago, when an ice sheet hundreds of meters thick covered most of Canada and parts of the US.
• In real life, dire wolves did roam the (American) North, although they didn't grow to the size of horses.
• The Mountain would never be able to crush a man's head until it burst, since an adult skull can withstand a whopping 1,000 lbs of force.
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Following is a transcript of the video.

Is that really possible? Could you really kill with a kiss? Direwolves aren't real, are they? Like millions of people worldwide, I'm a massive fan of "Game of Thrones." White Walkers, dragon riders, plot twists, and politics, the works. But I'm not just a fan. I'm also a science writer. So while half my brain dreams about befriending a direwolf, the other half questions if it's really possible to crush someone's skull with your bare hands.

Is it just a TV show? Yes. Is it a fantasy TV show? Also yes. Am I still gonna analyze it anyway? Oh yeah.

Let's get this out of the way. I know, I know there's magic in "Game of Thrones." When you're talking about fire-breathing dragons and vision-granting trees, science only gets you so far. But even so, you can find real science in even some of the most fantastical elements of the show. Take, for example, the Long Night.

Old Nan: Fear is for the Long Night, when the sun hides for years and children are born and live and die all in darkness.

Narrator: On the show, Old Nan tells Bran of a winter that lasted for a generation.

Old Nan: Kings froze to death in their castles, same as the shepherds in their huts.

Narrator: And with all her talk of White Walkers and giant ice spiders, the whole story seems farfetched. But it turns out a Long Night could happen in our world. In fact, it already has.

Twenty thousand years ago, an ice sheet hundreds of meters thick covered most of Canada and parts of the US. 25% of the planet's land mass was covered in ice year-round. That's more than double what we see today. The world was 5 degrees Celsius colder than in modern times, in some regions, reaching 22 degrees Celsius lower than today. Now, this cold wasn't brought on by White Walkers.

It was actually part of a regular cycle in Earth's climate, an ice age. Specifically, an extra-cold part of an ice age where ice sheets creep down from the poles. It's possibly caused when the upper part of the northern hemisphere receives less sunlight due to a bunch of factors, like how much the planet wobbles on its axis and how its orbit around the sun changes shape. And the last time this happened, the ice sheet made it all the way to New York City in the east.

While Manhattan was buried, parts of Brooklyn and Queens were left uncovered. So in a way, New York's outer boroughs are like a real-life Winterfell. We even have a wall, a 60-meter-tall ridge overlooking the outer boroughs. Now as Maester Aemon said...

Maester Aemon: Starks are always right eventually. Winter is coming.

Narrator: So is another glacial period on its way? Well, we're in the middle of what's called an interglacial period. That's a warm time when the ice sheet is in retreat, and somewhere in the range of tens of thousands of years, the glacial period will return, bringing the ice with it. So, yes, winter is coming. Eventually. But enough doom and gloom. Let's talk about puppies.

Brilliantly smart and unfailingly loyal, who wouldn't want a direwolf or six? But sadly, Nymeria, Ghost, and Grey Wind are as mythical as Drogon, Rhaegal, and Viserion. After all, they have a magic bond with the Starks and can detect zombies. That being said, dire wolves, spelled like this, really did roam the Earth, prowling the Americas between 125,000 and 10,000 years ago. Hunting in packs, they took down prey as large as a 300-kilogram moose. Sound familiar?

Ned Stark: There's no mountain lions in these woods.

Narrator: But unlike the Starks' mascot, these doggos never grew to the size of a small horse. Don't get me wrong. They were still enormous. They were about two-thirds larger than today's gray wolves. And while humans and dire wolves did live in the same range at the same, they probably weren't as close as Bran and Summer. Dire wolves, you see, aren't the ancestors of today's dog by any means.

Our Yorkies and corgis are more closely related to gray wolves than dire wolves. And according to recent research, dogs first came about 20,000 to 40,000 years ago, somewhere in Asia and the Middle East. So human-wolf team-ups happened on an entirely different continent than where dire wolves roamed. Now, direwolves are all well and good when it comes to fighting off knife-wielding assassins, but they're less useful if your enemy decides to use poison. Joffrey, Olenna, all the Freys. Poison brought down a lot of characters, especially Joffrey. And the scariest poison is called the Long Farewell.

Tyene Sand: Takes time to work, but if a single drop makes contact with the skin: death.

Narrator: And it turns out there's a real-life analog to the Long Farewell: snake venom.

Steve Trim: The African and Asian carpet vipers, their venoms cause epistaxis, which is the nose bleeding, because it weakens the capillaries and blood vessels, and so your blood starts to leak out.

Narrator: That's Steve Trim, a molecular biologist who specializes in venoms. Not only is he a big fan of "Game of Thrones," he also knows a thing or two about poison, and he noticed something very interesting about the Long Farewell because another snake called a sand viper also produces the venom that would have the same effect. And who uses the Long Farewell? That's right, Ellaria Sand, aka paramour to the Red Viper and mother to some of the Sand Snakes. Coincidence? I think not.

But even though viper venom can explain the Long Farewell's effects, it can't explain the kill-with-a-kiss tactic.

Steve: The interesting thing with the carpet-viper venom is that it's not gonna get into the body from a kiss. This venom can't, as far as we know at the moment, doesn't pass through the skin.

Narrator: And that's just one problem.

Steve: From a kiss, you've got a very small contact area, a couple of square centimeters at most, so you need something that's potent enough to actually have an effect in that small area.

Narrator: So in order for this to work, you'd need a poison like Novichok, which is so potent, just inhaling it could kill you. But Novichok doesn't cause internal bleeding the way we see on the show. So it looks like the Long Farewell is another bit of fantasy. Regardless, that poison isn't a fun way to go. But it doesn't look quite as horrible as death by the Mountain.

The Mountain: Elia Martell. I killed her...

Narrator: After all, who wants to get their head crushed like a soda can?

The Mountain: ...like this!

Narrator: Luckily, this is one threat you don't have to worry about because it turns out it's impossible. You see, the adult human skull is really durable. Pound for pound, it's stronger than steel or concrete, and if you squeeze an adult's skull, you'd need about 1,000 pounds of force to break it. That's about twice as much as even a man as strong as the Mountain could deliver.

Now, he could conceivably demolish his opponent's eyeballs, like he does here, since the soft, squishy tissue is even more vulnerable than the hard skull. But that wouldn't cause Oberyn's head to explode outward like that. Overall, this entire situation makes no sense.

That's right. Direwolves and eternal winters are more realistic than this totally nonmagical fight scene. So in the end, "Game of Thrones" does a pretty decent job when it comes to realism, at least where there's magic concerned. And while its more mundane spectacles can be farfetched, I'm still going to enjoy every minute. After all, I might be a science writer, but I'm still a fan.