CULTIVATING a child's talent for science is surprisingly easy here in the Baltimore-Washington corridor, with four planetariums, more than a dozen nature centers, two aquariums, a natural history museum and a nuclear power plant within easy driving distance.

You have a couple of choices here: You can approach science one field at a time -- checking out the electricity demonstration at the Museum of American History, say, or waiting in the dark for one of the Naval Observatory's telescope demonstrations.

Or you can wade right into this thing called science at Baltimore's Maryland Science Center -- three stories of hands-on, light-flashing, noise-making exhibits just a short walk from the city's Inner Harbor area. With its arcades and computers, the museum puts physics, geoiology, ecology and math just a pushbutton away.

Science Center personnel recommend that you start your tour on the third floor; it looks a little like a physics textbook in wonderland, providing hands-, ears-, eyes-, legs- on experiences in the laws of energy.

Giant disks placed at either end of one room create a whisper chamber for kids to try out funny noises and learn how sound waves work. Another machine lowers the pitch of the human voice; it was developed for divers plagued by the Donald Duck sound of speech in pressurized air.

There's a gadget for breaking up and redistributing a beam of light, which creates a picture on the wall; and prism lenses you can put over your eyes to help you see the colors in the lights around you.

Then there's a Roman arch you can construct (three attempts and we gave up -- it's all Greek to us) and a series of mirrors that seem to multiply your image to infinity.

The third floor also has a whole roomful of energy items from a bicycle you ride to produce enough energy to get yourself on TV (Donahue should work so hard) to windmills, generators, transformers and engines that work with cranks at speeds slow enough for even slow-of-mind parents to understand.

It's hard to get kids away from all this do-it- yourself physics, but we found on a recent visit that bribing works pretty well. A quarter should do it -- the next floor down contains computers, including video games. There's also a new design-your-own playground there, where visitors can use computers to make predictions on how weights will behave on a slide, seesaw or swing -- testing the predictions with real equipment lying nearby.

The rest of the computers, some of which weren't working at the time of our visit, also educate, teaching spelling and math.

Going downstairs onto the main floor puts you right in front of the gerbils, enthroned in a "natural" habitat. They're next door to a giant exhibit on geology, and across from one on the Chesapeake Bay -- both of which give visitors some limited, button-pushing opportunities. Then, at the store on the same floor, you can take away a piece of Maryland's rock for as little as 10 cents.

There are also a few fascinating fish swimming in tanks on this floor, but nothing like the hundreds you can meet eye to eye at the National Aquarium right down the street. Ambitious families may want to try for both museums in one day -- one very long day. You can whiz through the Science Center in a couple of hours, but you'll feel less like a nag if you allow a good three to four hours for your tour.

So it may be easier to take a day for the center, and then divvy up the aquarium and other science sites for weekend adventures later on. For the one-subject-at-a-time approach, here's a list of specialty centers waiting for you: ASTRONOMY ARLINGTON PLANETARIUM -- 1426 N. Quincy St., Arlington 558-2868. There are regularly scheduled family programs here and the current one, running through April 14, is "Star Travelers," which explains the solar system, constellations, nebulae and galaxies. Programs run Friday and Saturday at 7:30, Sundays at 1:30; cost is $1 per person. Reservations strongly recommended. NATIONAL AIR & SPACE MUSEUM -- Seventh Street and Independence Avenue SW.357-2700. NASM's Einstein Spacearium is currently showing "Comet Quest," starting at 10:50 each day. Cost: $1.50 adults, 75 cents students and senior citizens. NATIONAL CAPITAL ASTRONOMERS -- Call 320-3621 to find out about current meetings of this amateur group of astronomers. NAVAL OBSERVATORY -- Massachusetts Avenue at 34th Street, 653-1543. Night tours are scheduled every Monday, with tickets distributed at 7:30 on those evenings to the first 140 people. OWENS SCIENCE CENTER -- 9601 Greenbelt Rd., Lanham, 577-8780. On Friday nights at 7, there's a 45- minute program (the current show is about the sky watchers of ancient Mexico), followed by an update on the night sky and, if it's clear outside, a quick look at what's up there. $1.50 adults, 75 cents for students. ROCK CREEK PARK PLANETARIUM -- 5200 Glover Rd. (near the intersection of Military Road), 426-6829. This planetarium gives shows Saturdays and Sundays at 1 for children 4 and up, and at 4 for those seven and older. Free. BIOLOGY NATIONAL AQUARIUM -- in the basement of the Commerce Building, 14th Street Between E Street and Constitution Avenue. 377-2825. This is the nation's oldest aquarium, they say. It takes roughly an hour to view its 1,000-plus fish; come around 2 on Monday, Wednesday or Saturday to catch the shark feeding, or the same time on Tuesday, Thursday or Sunday to watch the piranha being fed. Cost: $1 adult, 50 cents for children 12 and under and senior citizens. NATIONAL AQUARIUM -- Inner Harbor, Baltimore. 301/576-3810. Open Monday through Thursday, 10 to 5, Friday from 10 to 8; Saturday and Sunday from 10 to 5. Admission: Adults $5.75; students and senior citizens, $4.25; children age three to 11, $3. NATIONAL MUSEUM OF NATURAL HISTORY -- 10th Street and Constitution Avenue NW.. 357-2700. The Discovery Room opens its hands-on exhibits in all life sciences (including anthropology) on Monday through Thursday from 12 to 2:30, Friday and Saturday from 10:30 to 3:30, and on Sunday from 1 to 3. If you're there in the middle of the day, you might like to pop into the Insect Zoo at 11:30, 12:30 or 1:30 for the tarantula feedings. NATURE TRAILS -- abound all over the D.C. area. If you're tired of the one at your nearest nature center, you might like to try Rock Creek Park's Nature Center (5200 Glover Rd., off Military Road) or the Audubon Society, 8940 Jones Mill Rd., Chevy Chase, near the intersection with Jones Bridge Road. GEOLOGY LURAY CAVERNS -- on Route 211 in Luray, Va., 91 miles from D.C. 703/743-6551. Open daily 9 to 6. One of the oldest and largest caves in the eastern U.S. Admission: $7 adults, $3 children seven to 13; includes tour of cavern and car and carriage exhibit. SKYLINE CAVERNS -- Take I-66 to Linden exit, take Virginia Route 55 to Front Royal and follow signs. 703/635-4545. Open 9 to 4:30 daily. Admission: $6 adults, $3 children seven to 13. CALVERT CLIFFS STATE PARK -- on Pennsylvania Avenue Extended (Route 4) past Prince Frederick. You can pick up a nature trail here that will take you 21/2 miles in to Scientist's Cliffs, a good place to find shark's teeth and other fossils. An easier way to see them is to travel farther down the road to the Calvert Marine Museum (301/326-2042), which has the largest exhibits of Calvert Cliffs fossils in the U.S. Open 10 to 4:30 Monday to Friday; noon to 4 on Saturday and Sunday. Admission free. PHYSICS CALVERT CLIFFS NUCLEAR POWER PLANT -- Route 4 past Prince Frederick, Md. 301/586-2200. The visitor center has hands-on exhibits, including computer games and a schematic of the plant. It's possible to take a tour of the plant itself but you must be 18 or older and give them advance warning, your driver's license number, your Social Security number, your phone number and come in a group. "And you don't see as much of the plant as you do in the schematic anyway," warns a spokesman. The visitor center is open 9 to 5 every day except Christmas and New Year's. MARYLAND SCIENCE CENTER -- 601 Light St., Baltimore. 301/685-2370. Open Monday through Thursday 10 to 5; Friday and Saturday from 10 to 10, Sunday noon to 6. Adults $3.50; children, senior citizens, students and Armed Forces Personnel, $3; $12 family rate. Third-floor science arcade has more than 40 hands- on displays using lenses, mirrors, telescopes, light and sound. Also a special children's room for ages four to seven, open Sunday from 12:30 to 4:30. NATIONAL MUSEUM OF AMERICAN HISTORY -- 12th and Constitution Avenue NW. 357-2700. There are exhibits here covering the history of our nation's contribution to physics. See especially the Demonstration Center in the Electricity Hall featuring the different ways man uses electricity. Exhibit open Monday to Saturday, noon to 3. Museum open 10 to 5:30.