Robert Krulwich

The 19th century just lost its last living man.

Look at the center of this map, at the little red dot that marks Kansas City. Technically, Kansas City is at the edge of Missouri, but here on this map it's in the upper middle section of a bigger space with strong blue borders. We don't have a name for this bigger space yet, but soon we will.

Let's get dense. If we take all the atoms inside you, all roughly 70,000,000,000,000,000,000,000,000,000 of them, and squeeze away all the space inside, then, says physicist Brian Greene:

There are people (and I hear from them constantly) who think if a subject is sophisticated, like science, the language that describes it should be sophisticated, too.

If smart people say torque, ribosome, limbic, stochastic and kinase, then the rest of us should knuckle down, concentrate and figure out what those words mean. That's how we'll know when we've learned something: when we've mastered the technical words.

It is autumn, and where I live the leaves are peaking; there is a riot of them everywhere, narrow ones, broad ones, droopy ones, crunchy ones. Leaves come in so many shapes, hues, textures — the closer you look, the more differences you see. Botanists have names for every leaf type, and clumped together, says writer Robert Dunn, they sound like free verse poetry ...

I guess everybody, even the smartest people who ever lived, have days when they feel dumb — really, really dumb. Oct. 1, 1861, was that kind of day for Charles Darwin.

In a letter to his friend Charles Lyell, Darwin says, "I am very poorly today," and then — and I want you to see this exactly as he wrote it, so you know this isn't a fake; it comes from the library of the American Philosophical Society, courtesy of their librarian Charles Greifenstein. Can you read it?

It says:

Whoah! You know the feeling, right?

Oh, dear.

First off, this lizard? It's not really a lizard. It's an almost vanished species, a reptile like no other.

Here's a question you probably didn't know was a question: Why is the sky dark at night?

Look at this map, and notice that deep, deep in the Republican South, there's a thin blue band stretching from the Carolinas through Georgia, Alabama and Mississippi. These are the counties that went for Obama in the last election. A blue crescent in a sea of red.

You are 200 miles directly above the Martian surface — looking down. This image was taken by the Mars Reconnaissance Orbiter on Jan. 27, 2010. (The color was added later.) What do we see? Well, sand, mostly. As you scroll down, there's a ridge crossing through the image, then a plain, then dunes, but keep looking. You will notice, when you get to the dunes, there are little black flecks dotting the ridges, mostly on the sunny side, like sunbathing spiders sitting in rows. Can you see them?

Before we go slow, let's go fast, so fast you can't go any faster. That would be light in a vacuum, traveling at 670 million miles per hour ...

Light, of course, can slow down. When light passes through water, it loses speed. A diamond is an even better speed bump. It can slow a beam of light by 40 percent.

But moving on, you and I are going pretty fast right now, though we don't notice. The planet we're on is zipping around the sun at 66,000-plus miles per hour ...

So you're minding your own business when all of a sudden, a nuclear bomb goes off, there's a shock wave, fires all around, general destruction and you, having somehow survived, need a drink. What can you do? There is no running water, not where you are. But there is a convenience store. It's been crushed by the shock wave, but there are still bottles of beer, Coke and diet soda intact on the floor.

So you wonder: Can I grab one of those beers and gulp it down? Or is it too radioactive? And what about taste? If I drink it, will it taste OK?

What we have here is a moon — a small one (slightly wider than the state of Arizona) — circling Saturn.

If you look closely, you will see a small splay of light at its top, looking like a circular fountain.

That's because it is a fountain — of sorts. A bunch of volcano-like jets are sending fantastically high geysers of water vapor up into the sky, so high that you can see them in this remarkable print by Michael Benson, back lit by light bouncing off of Saturn.

Check out this graph of America's "Growing Season" — it measures the number of continuous days and nights when it never gets below 32 degrees. You could call this our "frost-free" time of year. In many places, the frost-free season begins in the spring and ends somewhere in October.

As you can see, over the 20^th century, it's been staying frost-free longer...and longer...and longer...

This is one of those fun-to-think-about questions. A brain isn't much to look at, after all. It's about the size of your two fists put together, three pounds to hold, but oh my, what it can do.

With our brains, we can think backwards, imagine forwards, conjure, create things that don't exist, leap vast distances. For example, suppose I say to you, close your eyes and imagine this: