Amy Smith, age 11, of Wisconsin Rapids, Wisconsin, for her question:

How hot is the center of the earth?

The very center of our planet is almost 4,000 miles straight down below your feet. People have descended a mile or more below the surface, but certainly nobody has been anywhere near the earth's central core. So let's not expect any on the spot reporting from the scene. What we know about the earth's core is gathered from things that have been learned on  and above the surface.

Scientists can only suggest theories to describe the internal regions of the earth. But their theories are educated guesses, based on known facts and most likely they are quite close to the truth. For example, we know that the core must be made of very heavy materials. The known surface layers are too light to account for the planet's total weight of 6.6 sextillion tons. Obviously the heavy stuff that makes up most of the weight must be packed in the middle.

We also know from the vibrations of earthquakes that the planet is built in several quite different layers, with the dense, heavy material at the center and the lighter layers toward to surface. We know from mines and other deep diggings that the solid earth grows gradually hotter as we descend lower. These and other data are used to estimate the increasing temperature, all the way to the very center of the earth.

The thickness of the rocky crustal layer varies from some five miles below the oceans to more than 20 miles below the major land masses. At its deepest levels, the temperature of the crust is estimated to be perhaps 1,600 degrees Fahrenheit.

Below the crust is the mighty mantle layer, which reaches down another 1,800 miles. Its dense materials are mostly silicas and aluminum, iron and magnesium. The upper level of the mantle is around 1,600 degrees F. and its base is estimated to be as hot as 4,000 degrees.

The mantle enfolds the outer core, which enfolds the ball shaped inner core at the center of the planet. As you would expect, the temper¬ature continues to rise as we get closer to the central core. The outer core is about 1,400 miles thick and scientists believe that it is a molten mixture, mainly of iron and nickel. At its top level, where it rests below the mantle, the temperature is estimated to be around 4,000 degrees F. Things get hotter toward the bottom level, where the temperature of the outer core is thought to be around 9,000 degrees.

This brings us to the earth's inner core, the seething ball in the very center of the planet. Most likely it is made of nickel and iron, densely compressed under the enormous weight of the upper layers that surround it. Down there in the core, the seething temperature is estimated to be about 9,000 degrees Fahrenheit.

Of course, we cannot be certain of these inner planetary temperatures. And it's not likely that anybody will ever descend to such depths with a thermometer. But we have a lot of other evidence to make an educated guess and, based on what we know at present, the center of the earth seems to be around 9,000 F. degrees    which is hot enough to melt almost anything you can mention.