FLORA LICHTMAN: This is Science Friday. I’m Flora Lichtman, and we’re continuing our time travel adventure. It’s 70 million years ago. You’re running through a hot, swampy forest, stumbling through ferns, and on your tail is a hungry T. rex. What do you do? Run? Hide? Climb a tree? Accept your fate? Do you have any chance of escaping?

Well, science says maybe. This magic treehouse-esque experiment is the premise of a new book, How to Survive History. We’ll travel back in time to world-changing events– think the asteroid that wiped out the dinos, the eruption of Mount Vesuvius, the construction of the Pyramids– and we’re going to play a game. If you were plunked down in the middle of one of these scenarios, what would it take to survive with 20/20 hindsight and science on your side?

Joining me now to play this out is Cody Cassidy, author of How to Survive History. He’s based in San Francisco. Cody, welcome to Science Friday.

CODY CASSIDY: Thank you so much for having me. I’m excited to be here.

FLORA LICHTMAN: Cody, how did you get the idea for this book?

CODY CASSIDY: You know, I was searching around for a story to write for WIRED magazine, and I stumbled upon a study that seemed to suggest I could outrun a Tyrannosaurus rex. It was a study that looked at the sort of distance of their footprints and the height of their pelvis, and sort of determined that their top speed was around 12 miles an hour. And so I sort of went outside and tested that. And I didn’t quite run faster than that, to my disappointment.

But when I looked into it further and sort of looked at the advantages that prey have to their faster predators when they’re being chased, I sort of came to the conclusion that I probably could outrun the full-grown Tyrannosaurus rex. And I had so much fun thinking about that, and I sort of realized that I could apply those sort of same lessons to other ancient disasters. And it was a sort of fun way to not only learn about these disasters, but sort of learn about the cultures and the history and have a lot of fun doing it along the way.

FLORA LICHTMAN: I’m still surprised that you have a chance against a T. rex. I’m going to put myself in those shoes. So I’m not athletic, OK? I’m pretty sure I couldn’t get to 12 miles per hour, although I really don’t have a sense of how fast that is. But how would I do it? If I’m confronted with a T. rex, what do I do?

CODY CASSIDY: So for example, a brisk jog is about seven miles an hour. So it is a little bit– it is a little fast, but it’s attainable. And the way I think you might be able to do it is– they attached some accelerometers to cheetah and impala. And even though the cheetah runs at 53 miles an hour and the impala ran at about 40, the impala gets away about 2/3 of the time, and it does it by actually a counterintuitive strategy.

It doesn’t run at its actual top speed when it’s escaping the cheetah. It sort of maintains its maneuverability. And as the cheetah catches up and gets within one or two steps, it sort of swerves.

FLORA LICHTMAN: Like zig-zagging? Is that what I should picture?

CODY CASSIDY: Exactly. It actually is a strategy I employed on the playground when I’d run from faster bullies. And I’d sort of forgotten about this.

FLORA LICHTMAN: [LAUGHS]

CODY CASSIDY: But so judging by those numbers, you should be able to escape even if you’re a little bit slower than the 12 miles per hour that the T. rex runs.

FLORA LICHTMAN: How do we know that T. rex wasn’t fast? It feels so counterintuitive because they seem like such a mega predator. Why do we know that they– yeah, were topping out at 12 miles per hour?

CODY CASSIDY: Well, they couldn’t actually run. The T. rex was about 6,000 pounds, so it would have shattered its leg if both legs were off the ground at any one point. So it was more of a fast walker.

FLORA LICHTMAN: Oh, wow.

CODY CASSIDY: And it couldn’t really have walked much faster than 12 miles an hour, although I should add that that is only the full-size Tyrannosaurus rex. It actually was a much more dangerous animal to humans when it was a teenager, and that was only– because it was only about 2,000 pounds. And in that case, it could actually run at about 33 miles an hour, which suggests even if you employ the tactics of the impala, unless you’re sort of a top high school track star, you’d be in trouble running, and it would be best to hide.

FLORA LICHTMAN: OK. So if I– yeah, if I run into a a teenager T. rex, I either have no chance or I need to find a hiding spot.

CODY CASSIDY: Yes, you need to employ different strategies than running.

[LAUGHTER]

Maybe climbing a very tall tree.

FLORA LICHTMAN: So one of my favorite chapters in the book was the one about surviving the Chicxulub asteroid, the one that smashed into the Earth and killed off the dinosaurs. Put me on Earth the day of impact. Like, what would it be like leading up to that boom?

CODY CASSIDY: Surprisingly, you would have seen it– this is about 66.5 million years ago. And if you were in the Northern Hemisphere, you would have surprisingly seen it coming a few days in advance.

At first, it would have looked sort of like a faint star in the sky, and then the next night it would have sort of been the brightest, and then the next night it would have sort of outshined the moon and then the sun. And then it would have hit Earth– in this case, the Yucatan Peninsula– with the energy of about 100 million times the largest thermonuclear weapon ever detonated.

And so the results were catastrophic and sort of comprehensive. It vaporized the shallow sea above the Yucatan and sort of hit the bedrock of the Earth, sort of like the same effect that a cannonballer would have hitting a pool. Sort of gouged a wall of earth 20 miles high.

FLORA LICHTMAN: 20 miles high?

CODY CASSIDY: [LAUGHS] Yeah, exactly. And the cavity breached Earth’s mantle. And so all of that Earth, that 20-mile-high wall of earth would have sort of rained back down globally. The most catastrophic effect was some of the rock down there is actually oil and coated Earth’s stratosphere in sort of a black paint, and chilled– sunlight dropped on Earth by about 90%, and global temperatures fell by almost 50 degrees.

FLORA LICHTMAN: Because that black paint that was kicked up from the asteroid is now in the sky, blocking the sun?

CODY CASSIDY: Exactly. And it’s above the rain clouds. So even though– it ignited sort of global fires. That ash was wet down by rain. But because the sort of paint was above the clouds, it stayed up– it stayed aloft for almost 10 years.

FLORA LICHTMAN: OK. So if I wanted to survive, where do I need to be?

CODY CASSIDY: So I should note that this is [LAUGHS] one of the more difficult ones to survive. One of the experts I spoke with took quite a lot of convincing before he would– he gave me even a survival plan.

FLORA LICHTMAN: Like, the chances are slim even if everything goes right.

CODY CASSIDY: Exactly. [LAUGHS]

FLORA LICHTMAN: OK.

CODY CASSIDY: But your best chance is to be on the opposite side of the world of the impact and somewhere near the Equator, about where Indonesia is today where it didn’t totally freeze and there were some animals that did survive, particularly animals that nested in the ground. So I would suggest finding a deep cave because there’s a rain of fire is going to come down on the Earth as all that earth re-enters the atmosphere.

FLORA LICHTMAN: If I were on the other side of the Earth, would I feel the impact? Would I hear it? Like, would I know it had happened?

CODY CASSIDY: Yeah. The sonic boom of it entering the atmosphere actually reverberated around the globe a couple of times. The impact also rang Earth like a bell, which sort of fractured– earthquakes broke out globally as it sort of dislodged all the tectonic plates. So you would certainly know it happens, and then you would have a little bit of time to get in your cave.

And you should also get above the coastline because 1,000-foot tsunamis wrapped around the Gulf of Mexico and a 600-foot-high wave hit Europe. And it would be a little bit smaller on where it is now Indonesia, but certainly a danger as well.

FLORA LICHTMAN: OK. So I’m in my cave. Then what?

CODY CASSIDY: So even if you survived the initial impact, this sort of rain of fire and the global tsunamis, the cooling Earth eventually kills land animals larger than a raccoon. It kills all the dinosaurs and the birds. And our ancestors survived, but they were about the size of a shrew. So [LAUGHS] food becomes an issue for a large animal like yourself.

But in the river estuaries, I would suggest you hunt because turtles did survive and other animals. Fish and of course sharks, though those would be harder to catch. [LAUGHS] So you have to survive about 10 years. But after that, the Earth did make a recovery.

FLORA LICHTMAN: On a pescatarian diet. I feel like I could make that work.

CODY CASSIDY: Yeah. You know, our ancestor did, and they were about the size of a shrew at the time. So I suggest not eating them, because it’s actually unclear how many of those did survive, so you might have some sort of catastrophic butterfly effects there. But there might be enough.

FLORA LICHTMAN: OK. So I want to hear a little bit about the research process for this book. Did you just have, like, a million strange Google searches [LAUGHS] while you were writing it?

CODY CASSIDY: I did have, of course, yes, a lot of strange Google searches and I sort of– a lot of science papers and reading how the different impacts affected the Earth such as the asteroid. But I think my favorite part was sort of asking the experts, people who had worked on the ground such as in Pompeii what they would have done if they were there. I sort of found those answers the most interesting, and in many cases surprising.

FLORA LICHTMAN: What was the fact that surprised you the most that you learned?

CODY CASSIDY: Well, [LAUGHS] speaking of Pompeii, when I when I spoke to the archaeologist who’s done quite a lot of work there and I asked him how he would have survived, he suggested actually you run toward the volcano, which [LAUGHS] I found surprising. But he said the timing of the eruption and the way the wind– the way the wind blew that morning would actually mean that if you ran toward it and then past it, you would have the best chance.

FLORA LICHTMAN: Well, let’s go to Pompeii. So you start this chapter at a bakery. So let’s say I’m ordering a square of focaccia and a few miles away Mount Vesuvius starts erupting. Would I notice? Like, would I know that that’s happening?

CODY CASSIDY: Certainly, yeah. If you’ve ever been to– [LAUGHS] if you’ve ever been to Pompeii, Mount Vesuvius sort of looms over the town. It’s only about five miles away. And so immediately, the earthquake would hit and the gas started– the gas cloud would have started rising.

But fortunately, the early stages were not the most dangerous. Because the wind blew the cloud that morning, it sort of rained the ash on Pompeii, but it sort of fell as a snow initially. But this was the most important period. Some people decided to take cover from the falling ash and some people decided to run. And certainly, running was the best option.

FLORA LICHTMAN: OK. So what should I do? I should not stay put. Where should I go?

CODY CASSIDY: Well, because the wind blew south that morning, it actually carried the cloud further– and Pompeii is south of the eruption. It carried the cloud further in that direction. So even though your initial [LAUGHS] instinct– which in many cases, I should add, is probably the right one in volcanic eruptions. But in this case, would not have been the best decision.

We know, for example, Pliny the Elder died in Stabiae, which is a good few miles south of Pompeii. So you have an option to run east, but that is blocked by mountains, so it would make your escape slower. You could try to sail away, and certainly, some did. But the wind was against you, and there were some sort of small tsunami waves that the earthquake caused.

So really, the best option is to run past the volcano. If you run, there’s a coastal road. It takes you to the town of Herculaneum, which is right at the base of Pompeii and a sort of luxury resort for Romans. But you shouldn’t actually stop there because the first pyroclastic surge, which is what happens when the volcano loses– the gas cloud loses its sort of power, and instead of rising into the stratosphere falls to the– falls to the ground and rolls, sort of like a superheated sandstorm moving at highway speeds. It’s a cloud hot enough to melt lead.

FLORA LICHTMAN: Fun.

CODY CASSIDY: That first hits Herculaneum around 3 o’clock in the afternoon. You have to keep going.

FLORA LICHTMAN: Does that head to– does that head to Pompeii too?

CODY CASSIDY: It does, yeah. That hits Pompeii later in the afternoon, which is what eventually buried the town and why we see all those perfectly preserved sort of plaster casings of the bodies there, and why you should not stay there and take cover. But if you make it all the way to Naples, which is about 13 miles– and you have five hours, so that’s sort of a fast walk– you should be fine. But it’s quite hot, I should add, so just make sure to stay hydrated.

FLORA LICHTMAN: This is Science Friday from WNYC Studios. I’m Flora Lichtman, talking with author Cody Cassidy about his new book, How to Survive History. Let’s zip over to ancient Egypt during peak Pyramid building time. If I wanted to be part of this great infrastructure project, how would I get conscripted to work?

CODY CASSIDY: So conscripted actually is the right word for ancient Egypt and building the Pyramids. Those who built, carried the rocks were actually probably farmers along the Nile and were conscripted sort of like a modern conscription army during the summer when the Nile’s flood floods the farmlands there and makes the land so fertile, but also idles the farmers.

So Pharaoh Khufu had this huge workforce that was sort of– was kind of nothing to do during the summer. And he would conscript them to lift the rocks of his Great Pyramid.

FLORA LICHTMAN: That sounds like a terrible job. How did people feel about it?

CODY CASSIDY: You know, surprisingly, it looks like there was– a sort of esprit de corps kind of developed amongst these workers. They would have team names. We can see these sort of graffitied into the Pyramid. One of them was called Khufu’s Drunkards. They also ate quite well. There’s a tremendous amount of beef bones that have been found, which was an expensive meat, and sort of indicative of the level of resources that Khufu devoted to building his Great Pyramid.

FLORA LICHTMAN: What are the risks to my survival?

CODY CASSIDY: [LAUGHS] Well, there are quite a lot of risks. There’s a cemetery at the base of the Pyramid with workers, and many of them show significant fractures of the arms and legs. And in this book, I sort of focus on the heaviest stone in the Pyramid was this 80-ton black granite rock found almost 200 feet up. It forms the roof of Khufu’s tomb.

Hauling a rock of that size would have a lot– tremendous number of risks. It certainly violates OSHA’s recommendations of hauling 50 pounds. It suggests that there were– probably at least 300 workers were hauling this up a ramp. It was about an 11% grade. And when you’re pulling that much weight, there’s actually quite a lot of danger of the rope– the rope snapping.

There have been some really gruesome disasters when there have been some tug of war– large tug of war teams. And so I suggest not standing at the front of that hauling team because if a rope snaps, it actually can hurtle back towards the pullers at a sort of fast enough speed to actually remove limbs. So certainly, stand back and– stand at the back, and don’t lift with your back either. Use your legs.

FLORA LICHTMAN: Is there still debate about how the Pyramids were built, or are people settled on aliens?

CODY CASSIDY: [LAUGHS] There’s certainly no debate about the fact that they used ramps. The biggest debate is the design of the ramp on how to pull up the stones. They certainly sat stones on sleds and then used a sort of mud-slicked surface to haul them up. But if you speak to the archaeologists who’ve actually been there and worked on it, they suggest to me that there’s really no debate at all.

They actually see the quarry at the base of the pyramids. It’s still there if you visit it. And there is a ramp leading up from the base of the quarry to the surface. And if you continue that trajectory, it would arrive at the– basically, about the mid height of the Pyramid, about 200 feet up at about an 11% grade. And then they think it just sort of did one loop around the back of the Pyramid to the top.

FLORA LICHTMAN: So you know, there’s no shortage of existential threats and catastrophes in the world that we live in now. In looking back and doing this book, has this made you think differently about our current predicaments?

CODY CASSIDY: Totally. I think a lot of these disasters– I was surprised– repeat themselves. You know, Pompeii is still within the shadow of an active volcano. I still live on a fault line. I think a lot of these disasters surprisingly repeat themselves. And the less– and they repeat themselves in a similar way. Hopefully, this has less relevance toward today, but sort of the sacks, the way cities were sacked and the way famines occurred usually occurred in the same way.

And the instructions were actually the same, in which case a lot of times I didn’t– I only wrote about one category of disaster in this book because were I to write about medieval sacks or medieval famines that occurred hundreds and sometimes thousands of years apart, it would actually be similar instructions. So that was one thing that I think echoes today and would echo forward.

FLORA LICHTMAN: Cody Cassidy is the author of How to Survive History. Thanks for joining me.

CODY CASSIDY: Thank you so much for having me.

FLORA LICHTMAN: To read an excerpt from Cody’s book, visit sciencefriday.com/survive.

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