This Sunday is, of course, the Summer Solstice. It's one of the few remaining popular links between sky and Earth. Ask friends what happens on June 21 and they're likely to get it right - mostly. Longest day: check. Sun highest up: check. Sun moves through the sky along its most curving path: hmm, what? That one's not widely known.

Still, people do pretty well with the Solstice. Yet most folks fail miserably when it comes to everything else about the sky. Even those with PhDs bomb when asked the stone-simple sky stuff that every village idiot would have known 200 years ago. Go ahead; test your friends. As the sun is setting, does it move straight down, down and to the left or down and to the right? Most get this wrong. A century ago, everyone would have picked the latter choice without a moment's hesitation.

Why is the world more sky-stupid than at any time in history? Perhaps people are less observant. More finish college than ever before, but you don't need a classroom to learn the basics of the natural world. It stares you in the face. But if you're not looking, you won't see it.

We could offer a hundred pages about the Solstice and its fascinating history, mythology and science, but few could handle it. Even many astronomers prefer entertaining gee-whiz-type information rather than technical facts. Which of these revelations do you find more interesting?

a) Researchers just found a pulsar 4,600 light-years away that only emits gamma rays.

b) Shadows of the moon's mountains creep along the crater floors at 10 miles per hour: the speed of a jogger.

Most of us would pick (b), even though the info is centuries-old, while the other discovery is brand-new. That's because it's more fun to learn about things with which we're already somewhat familiar. We enjoy gossip about friends, not strangers. Factoid B combines the everyday concepts of shadows, jogging and a graspable speed.

Here's a quiz question that you'll probably enjoy: What kind of energy does the sun emit most strongly?

a) Heat

b) Gamma rays

c) Ultraviolet energy

d) Green light

This is fun mainly because the answer involves something familiar, rather than exotic. In this case, it's ordinary green light. When we realize that green is the wavelength most prevalent in starlight, and that our eyes too are maximally sensitive to it...well, we can relate to this kind of stuff.

Another example: What's the only celestial body that moves through space its own width in an hour? Answer: the moon. That's why it takes an hour to enter our shadow during eclipses.

Notice that all these involve light or time: the key players in the Solstice. So the most fascinating information involved things that you don't already know, but to which you can relate. With that in mind, here are a few more Solstice goodies:

" The Solstice sun stands directly over the Tropic of Cancer - just south of Key West.

" It's when the midday sun is highest of the year, but it's getting less high over time. That's because Earth's tilt is decreasing.

" The Solstice is when the sun is lowest in the sky for those at the Equator.

" The word solstice comes from the two Latin words "sun" and "stoppage." Makes sense: The sun stops moving north that day.

" In India, the Summer Solstice ends the six-month period when spiritual growth is supposedly easiest. Too bad; you blew it.

" That day, the sun rises farthest left on the horizon and sets at its rightmost possible spot. Sunlight strikes places in your rooms that get illuminated at no other time.

" In ancient Greece the solstitial sun was in the constellation Cancer. But it has been in Gemini since around the time of Christ. In 1989 it shifted into Taurus, where it will remain until the fifth millennium.

Choosing which of a hundred such Solstice morsels will interest people depends on the audience. It may be the best-known sky event, but everyone has his or her own unique attention span and appetite for information. Maybe that's why TV announcers merely give it two seconds: "It's the start of summer!"