Investigators have undertaken such studies very recently by employing a new radiometric method technically called _gamma-ray spectroscopy_. Work of this sort has been and is being done at the Los Alamos, New Mexico, Scientific Laboratory on scores of meteorite and tektite specimens loaned to the Laboratory by the Institute of Meteoritics. Some of the individual meteorite specimens tested weighed as much as 37 pounds, and are probably the largest single extra-terrestrial masses yet tested for cosmic ray-induced radioactivities. Let us turn now to another important application of meteoritics. Any body in motion through the air or in space has a “striking power” of sorts. For some objects, this striking power, which is technically known as _ballistic potential_, is very weak, as in the case of silky milkweed-down drifting through the air. Hailstones have a good deal more striking power, as may have been painfully demonstrated on your own head. And, finally, such masses as falling meteorites (and especially those orbiting in space, unretarded by atmospheric resistance) have an extraordinarily formidable ballistic potential. This is because meteorites are not only tough and dense, as good projectiles must be, but are also moving at high velocities—particularly high if the meteorites come into the Solar System from interstellar space. For this reason, the speeds of meteorites are very important to scientists responsible for rocket flights and for keeping satellites aloft over long periods of time. Clearly, these men must have as accurate information as possible on where and how fast meteoritic particles are moving, so as to chart the safest routes for spaceships, and to develop satisfactory means of protecting rockets and satellites against the effects of bombardment by the smaller meteorites. For these “small-fry” cosmic missiles are so numerous that many of them are sure to be encountered even in brief flights outside the earth’s atmosphere. Such information might also prove valuable in the future to the crews of spaceships on long flights into deep space. Such men may face the life or death problem of taking successful “evasive action” against giant meteorites that will seem like flying hills and mountains. A strong parallelism exists between a meteorite fall and the re-entry of a nose-cone or data-capsule into the atmosphere. To a considerable extent, the difficult problems connected with the latter are being attacked at present through careful studies of meteorites. From the air-sculptured shapes of meteorites, their crustal flow patterns, and the thicknesses and types of fusion crusts they show, scientists are learning a great deal about certain factors connected with the re-entry problem. These factors include rate of vaporization, effects of extreme temperatures, and types of sculpturing to be expected as a result of encountering the resisting molecules of the atmosphere.