Scientists are renewing efforts to discover what lies at
the center of the Earth.-- Geologists have long been frus-
tated by a deep ignorance of our planet's core, and how it
generates the magnetic-field that guides compasses and pro-
tects plants and animals from dangerous cosmic rays.
 
Our rough picture of our subterranean world comes from
tracking how quickly seismic waves caused by underground
disruptions travel across the planet. But those assumptions
are based on limited information, and eventually could be
proven false.
 
The most mysterious layer is the one furthest down. The earth's
core, which lies nearly 4,000 miles from its surface, is as hot
as the Sun's surface. Some scientists believe the core is com-
posed of a lumpy mass of slow-flowing iron.
 
Determining what is really happening at the center of the Earth
will be difficult. Several labs have tried to recreate cores by
pouring molten metal into barrel-size copper spheres; hoping to
replicate the core's magnetic field.
 
Another approach, more reminiscent of an imaginative science-
fiction novel, involves actually digging down to the core.
..David Stevenson, a professor of planetary science at the Calif.
Institute of Technology, has proposed pouring 100,000 tons of
liquid iron, along with sensors, into a crack blasted into the
Earth.
..Gravity should pull the metal into the Earth's core in a week.
The problem, Prof. Stevenson said, is that "the effort required
would be comparable to the Manhattan Project, or a space mission."
 
..Soviet scientists started drilling a hole in 1970 to see how far
they could get. They gave up in 1992 when the crust became too hot
and gooey for the drill to work. They had managed to create a can-
talope-wide tunnel, 7.6 miles long... some .002% of the way to the
core. {fini}