I am zeroing in on a trillion.

Thanks to the labors of Caroline Green's pupils in Big Bear Middle School, we know what a million is. It's four 30-gallon plastic trash bags full of square-inch pieces of The Times.

Green had her class tear The Times into 1 million pieces to give them some conception of the number of Jews--6 million--that died in the Nazi Holocaust.

In reporting on that ingenious classroom exercise, I noted that I have always tried to think of a million as the Coliseum filled 10 times.

Jim Robinson, a high-school teacher in San Diego, says he explains a million to his students in terms of "simple, cold cash." He explains that a basketball player must play 80 games over a six-month period to earn $1 million, but the highest-paid teacher in San Diego must work 182 days a year for 25 years to earn a million.

Fred Gruenberger of Popular Computing sends a few illustrations from that publication: "A million days ago was 765 BC. A billion grains of common table salt would weigh 300 pounds--about seven cubic feet. A billion pencils laid end to end would go around the Earth nearly five times and weigh 6,168 tons. A billion five-grain aspirin tablets would weigh 417 tons and would fill your swimming pool 11 times."

When you get into the billions my mind numbs. It was obviously numb when I let George H. Matter's estimate of the known universe as 200 million miles slip past me. Laurence McGilvery of La Jolla points out that Matter's figure is "too small by a factor of something over 50." Isaac Azimov bears that out, estimating the size of the universe at 10 * billion * light years. Roy Brady notes that the Mauna Kea observatory recently detected an object * 15 * billion lights years away.

As McGilvery wisely counsels, quoting A. E. Houseman, "The less you say about that which you do not understand, the less you will say that is foolish." Brady adds: "Most people should leave things mathematical alone, even the most elementary."

OK. Leaving mathematics out of it, what I want to know is what will we find at the end of the universe? Will there be a wall? A plastic screen? Another universe?

It might seem wise to leave a trillion to the mathematicians, but since Congress recently passed a $1.1-trillion budget, which we must all pay for some day somehow, maybe we all ought to try to get some idea of how much that is.

McGilvery says a stack of 1 trillion $1 bills would be 67,000 miles high, or more than a quarter of the way to the moon. Also, he says, the total of U.S. currency in circulation is less than one-quarter trillion dollars.

Using my method, McGilvery calculates that the Coliseum would have to be filled 10 million times before 1 trillion tickets had been collected. "Assuming one event each day, it would take over 27,000 years to reach that goal." By that time, of course, our Coliseum will have crumbled into dust, and so will Rome's. (Actually, I have an idea our Coliseum will perish under the wrecking ball before today's children are making $1 million a year on the basketball court.)

Numbing my mind even further, Barbara Rasmussen of Pacific Palisades quotes the Saint Joseph Federal Credit Union Quarterly Report: "If you packed 1 trillion $1 bills into 50-foot-long boxcars, the train would have 15,743 boxcars that would stretch 167 miles."

Also: If you won a $1-trillion lottery and received a $100 bill every second, it would take 317 years just to collect the money.

I wondered earlier whether teacher Green's paper-tearing game would "increase (her pupils') international awareness," as she hoped.

Recalling the Holocaust, Carol Ratelle of La Habra observes that the world "should have been forever horror stricken, but mass murder still goes on. . . . Perhaps this is the international awareness the teacher had in mind."

S. M. Rosen of Newbury Park adds: "I commend Ms. Green for her ingenuity, and I do hope she impresses on her charges that each one-inch square represents a human being. . . ."

Says Margaret Marketa Novak, a Holocaust survivor, "It is essential that our children be taught this awful truth. . . ."

Isn't Caroline Green worth as much as Magic Johnson?