Robert Krulwich

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:

A lot of you have had it by now, or are having it or are about to be exposed. This year's flu is called "H3N2" and this week it's doing big business in about 47 states, Chicago and New York. If you've had a flu shot and if you wash your hands several times a day for 20 seconds, (which is the time it takes to hum "Happy Birthday to You" two times through) you might reduce your odds of getting sick.

Updated Jan. 1, 2013: I've added a postscript to this post. You can find it at the bottom of this page.

Look at yourself. Right now.

You are muscle,skin, bone, brain, blood, warmed by energy, and all of you, every cell, even the subsets of those cells, all trillions and trillions of them, are going to tire, waste and depart. In 10 years almost every bit of you will have been replaced by new bits.

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 was 1569, or maybe early 1570, when it happened: A young French gentleman was out for a ride with his workers, all of them on horseback, when suddenly, "like a thunderbolt," he felt something thick and fleshy slam him from behind. (It was an overzealous, galloping assistant who couldn't stop in time.) Michel de Montaigne's horse crumbled, he went flying up, then down, he crashed to the ground. Then things went black.

When he came to, a minute or so later, he says,

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?

There was a time — and it wasn't that long ago — when kids would leave home on a summer morning and roam free. "I knew kids who were pushed out the door at eight in the morning," writes Bill Bryson of his childhood in the 1950s, "and not allowed back until five unless they were on fire or actively bleeding." That's what kids did. They went out. Parents let them, and everybody did it. "If you stood on any corner with a bike — any corner anywhere — more than a hundred children, many of whom you had never seen before, would appear and ask you where you were going," Bryson writes.

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:

It's hot today. Really, really, hot; over a 100 degrees Fahrenheit hot, and so I'm sweating.

Think of a giraffe lying on the Serengeti plain. He has just died, maybe of disease, maybe he was killed by a pride of lions, but now he's a 19-foot-long, 4,000-pound mound of meat, which very soon is going to stink and rot and muck up the neighborhood.

"Mind is such an odd predicament for matter to get into," says the poet Diane Ackerman. "If a mind is just a few pounds of blood, dream and electric, how does it manage to contemplate itself? Worry about its soul? Do time and motion studies? Admire the shy hooves of a goat? Know that it will die?

...How can a neuron feel compassion?"

Yes, how?