Dinosaurs

Hello, my friends! I am your knowledge guru and all-around role model, Ken Jennings. You may call me Professor Jennings.

I can tell by your large brains and hairy heads that you are all mammals. Good job, everyone! It’s great to be a mammal, isn’t it? We have pretty much ruled the earth for the last sixty million years. But in today’s class we’re heading back into earth’s prehistoric past, to find out who was running the show before the mammals. (Spoiler warning: You will not believe this, but IT WAS GIANT REPTILES!)

We have billions of years of prehistory and hundreds of different amazing dinosaurs to cover today. But even that huge amount of knowledge should be no problem for a Junior Genius. Remember, our official motto is "Semper quaerens, which is Latin for Always curious."

Before we leave the twenty-first century behind, let’s say the Junior Genius Pledge! Place your right finger to your temple, face this drawing of Albert Einstein, and repeat after me!

With all my fellow Junior Geniuses, I solemnly pledge to quest after questions, to angle for answers, to seek out, and to soak up. I will hunger and thirst for knowledge my whole life through, and I dedicate my discoveries to all humankind, with trivia not for just us but for all.

All right, Junior Geniuses. I hope you like volcanoes, because when you turn the page, we’re going to be on a very different earth.

THE LAND BEFORE TIME

History means writing things down, Junior Geniuses. If nobody records something happening, historians will never know about it. Keep that in mind when a grown-up promises to get you ice cream later or some other time. Get the promise in writing, or it didn’t happen!

Human beings have been keeping written records for only five or six thousand years. Everything that happened before that is prehistoric—before history.

We all know how time in recorded history works: We use a calendar. Days, months, years, centuries. Prehistory is different. The dinosaurs didn’t know or care if it was Tuesday or Friday or March or October.

Prehistoric time uses a geologic time scale, which scientists calculate based on evidence they find in rocks. Comparing geologic time to a modern calendar is like comparing a dinosaur to a flea: It’s much, much bigger.

Geologic time is measured in:

AGES

(long spans of time, hundreds of thousands of years)

that combine to make up

EPOCHS

(really long spans of time, millions of years)

that combine to make up

PERIODS

(incredibly long spans of time, tens of millions of years)

that combine to make up

ERAS

(amazingly long spans of time, hundreds of millions of years)

that combine to make up

EONS

(insanely long spans of time, billions of years)

EARTH DAY

The problem with geologic time is that it’s hard to wrap your brain around it. Think how long one minute can feel on the last day of school, or when there’s not a vacant stall in the restroom and you’re desperate. Now try to imagine one billion years’ worth of minutes. Good luck!

But I have a trick that may help. Let’s compress the entire life of the earth down to one twenty-four-hour day. Blink your eyes once. BOOM, more than five thousand years just passed. All of human history, and you missed it. That’s how fast time is going on this scale.

If the earth has been around for only one day, it was pretty busy.

12:00 A.M.: Earth forms out of dust and gas swirling around the sun.

4:00 A.M.: Life! Microscopic one-cell organisms appear in the oceans.

1:00 P.M.: Not until after lunch do these cells start to have a nucleus and little organs.

6:30 P.M.: Around dinner, tiny multi-cell creatures.

8:30 P.M.: The first plants—simple seaweed.

8:50 P.M.: Right around bedtime, animals finally explode onto the scene. Jellyfish!

9:50 P.M.: Animals and plants evolve onto land.

10:20 P.M.: Insects! Reptiles!

11:00 P.M.: Dinosaurs rule the earth.

11:40 P.M.: The dinosaurs disappear, and mammals take over.

11:59 P.M.: Human beings evolve and eventually develop farming, the Great Pyramids, democracy, and, finally, the Junior Genius Guides.

That’s the time scale we’re talking about. Pretty much all of human evolution is the last minute of the day. Sixty seconds. Two TV commercials.

So it’s not all about us.

A DIFFERENT WORLD

For the first billion years, earth was a lifeless rock. But that doesn’t mean it was boring. Here are some things you should not do if you ever travel back in time to visit the earth of more than 4 billion years ago.

Remember not to . . .

Breathe! The atmosphere has no oxygen. Unless you’re a fan of poisonous gases such as carbon monoxide, ammonia, and methane, hold your breath.

Walk anywhere! Do you like that playground game where you pretend the ground is lava? Well, here the ground is literally lava. Even once the earth’s rocky crust forms, giant volcanoes are everywhere.

Get wet! Once rain starts to fall and the oceans appear, they are heavy on sulfuric acid instead of oxygen.

Go outside! A hail of asteroids and comets is hammering away at the earth, pulled by some mysterious chaos in the orbit of the other planets.

On second thought, maybe it’s not a nice place to visit at all.

COMET RELIEF

Of course, we might not be here today if not for those icy comets. When they smashed into the earth, they delivered water that helped make life possible.

SOUP-ER MODEL

We don’t know exactly how life first appeared on earth, but it was a long, slow process. In the 1950s, a group of scientists combined four simple chemicals (water, methane, ammonia, and hydrogen) and heated and cooled them while zapping them with electricity. Within weeks the mixture had started to form amino acids, the molecules that make up the proteins in living cells.

Could the same thing have happened across millions of years as lightning struck the prehistoric ocean? (Sometimes scientists call this liquid the primordial soup, which does not make me hungry for soup.) And could those complex molecules have eventually evolved into early proto-cells? It seems possible. Other scientists think that the first life to arrive on earth may have hitched a ride aboard comets or meteorites. If that’s true, we are all space aliens.

In any case, life appeared before the