At a point 2,000 feet above the ground, the first atomic rocket of World War III explodes over your city.

1. WHAT AN A-BOMB WILL DO

Out of the sun a black, cigar-shaped object falls toward the earth. At the edge of town a filling station attendant sees it cross the slice of sky between the car above him and the edge of his grease pit. The center fielder of the visiting baseball team sees the moving spot, then looks back toward the batter, impatient for the third out. A woman in the park hears a strange, thin whistle and looks up, shading her eyes.

At a point 2,000 feet above the ground, the first atomic rocket of World War III explodes over your city. In one vast flash of light, equal to 100 suns, the buildings are etched against a sky of fire. A blinding ball of flame leaps from the point where the rocket exploded.

There, in a millionth of a second, a lump of plutonium or uranium, perhaps the size of a basketball, disappears. As it vanishes, the temperature at that point jumps to 1,000,000 degrees Centigrade. The air around it is pushed outward by a pressure hundreds of thousands times that of the normal pressure of the atmosphere.

A thousandth of a second later, the ball of fire is 45 feet across. Its temperature has dropped to 300,000 degrees.

After a full second, there is a globe of flaming air 450 feet wide, the size of a city block.

The shadows cast by this ball of fire are etched permanently into concrete sidewalks and granite buildings. Directly beneath the burst, in the split second before the blast wave arrives, pedestrians simply vanish into smoke and ash. This is the point which atomic scientists call "ground zero." Here the sidewalk temperature is between 3,000 and 4,000 degrees.

Light buildings and homes are totally demolished by the blast.

With the sheer flash heat comes another form of radiating energy, the only one which a conventional high-explosives bomb cannot match on its smaller scale: Nuclear radiation, X-rays of the A-bomb, invisible yet striking through concrete and steel to destroy the single human cells in bone marrow, blood and living tissues.

Then the blast hits. A moving wall of shock crushes the city under a giant hand, wrenches it from its foundations, levels a mile-wide area into rubble. Small masonry buildings are engulfed by a pressure wave and collapse completely. Light buildings and homes are totally demolished by the blast. Factories of steel are stripped of roofing and siding. Only twisted skeletons remain, leaning away from ground zero as though struck by a hurricane of stupendous proportions.

When the shock and blinding heat have gone, fire springs up in the wreckage. And billowing out in great clouds of dust, falling back to earth from the towering mushroom of smoke, there is the hidden terror which scientists call residual radioactivity.

What are these massive forces which an atomic explosion turns loose? How will they affect you?

ATOMIC FORCES

When energy is released suddenly by any sort of bomb, the rise in temperature of the exploding material causes complete vaporization of the bomb, casing and all. Solid matter suddenly turns to gas.

The tremendous heat generated by the explosion sends forth energy in a way which the scientists call thermal radiation.

This gas is in a restricted space, pushing outward with huge pressure on the air around it. So great is this push that it can move air, water or earth, whatever is around the bomb when it goes off. The series of events which follow constitute the destructive blast of the bomb. In TNT and atomic bomb alike, blast does nearly all the physical damage by brute force. The tremendous heat generated by the explosion sends forth energy in a second way, which the scientists call thermal radiation. This is heat traveling with the speed of light, heat exactly like that given off by the sun. The rays are not penetrating. They are stopped by any object which stops light.

Alone in the atomic bomb, rays of nuclear fission channel a third explosion of energy. When the radioactive material of the bomb disintegrates, it releases various particles of electricity: beta particles, the atom's electrons; alpha particles, which are combinations of neutrons and protons; neutrons alone, the particles from the center of atoms; and finally gamma rays, which are high-energy rays very similar to X-rays.

The cumulative effect of these sources of energy is the measure of the atomic bomb, or of any other explosion of nuclear force, whether it be in the fission of uranium or the fusion of hydrogen in the "Hell-bomb."

The nominal atomic bomb is the equivalent of 20,000 tons of TNT.

The Atomic Energy Commission and Department of Defense have released a comprehensive handbook entitled "The Effects of Atomic Weapons," half a decade after the world's first atomic bomb was exploded. It tells the technical story of what will happen to any city under an attack similar to that on Hiroshima and Nagasaki.

AEC scientists at Los Alamos who wrote the report describe a "nominal atomic bomb." This they use as the basis for their calculations in damage and death. The bomb is the equivalent of 20,000 tons of TNT. Expressed in electrical energy, it is roughly equal to the daily output of the generators at Hoover Dam. Yet this tremendous force is only equal, they say, to the energy which would be released should 2.2 pounds of uranium 235 fission completely.

The explosion of the nominal bomb takes place in the first millionth of a second after two lumps of uranium or plutonium are brought together into one lump. The shock wave, the heat rays, the radiation leap outward.

A large building is struck by a greater force than a small structure.

The shock wave moves with the speed of sound. In a sense it is a moving wall of air, water or earth under tremendous pressure. When this wall hits a resistant surface, it hits with a punch multiplied by the size of the surface in its path. Thus a large building is struck by a greater force than a small structure, and often suffers greater damage.

In an atomic bomb exploded in the air, the front of this shock wave is vertical. The high pressure hits as a giant blow. Behind the shock front, high pressure reaches back for a considerable distance on the wave. Behind that is a region where the pressure drops to less than normal, a region of suction.

DESTRUCTION FROM THE BOMB

When a building is struck by the blast wave, it is first punched on one side by the wall shock. Then, as pressure moves on with the speed of sound, it envelops the entire building, squeezing down from all sides. This pressure decreases rapidly, and is succeeded by suction which pulls wind, debris and people back toward the point of the explosion. With shock and suction comes wind of great speed, first away from the bomb, then toward it, adding to the havoc.

The pressure of the blast wave is succeeded by suction.

The great power of the atomic bomb produces so-called "mass distortion" of buildings. It engulfs and flattens whole buildings. The area of virtually complete destruction at Hiroshima and Nagasaki, where the bombs were approximately the size of the "nominal bomb," was about 2,600 feet in radius. Inside a circle swung on a line half a mile long, the area of almost total havoc covered three-quarters of a square mile.

The circle of severe damage, where buildings are wrecked to the point of near collapse, will reach out a mile, covering four square miles. From this point, damage will diminish with distance, depending to a great extent upon the weather and hills and valleys of the city. Even as far as eight miles from the blast, windows will break and plaster will fall. The overall area of damage will be about 200 square miles.

The area of complete destruction was about 2,600 feet in radius.

Buildings designed to be earthquake-resistant were found in Japan to have suffered remarkably light damage, even when relatively close to ground zero. Smoke stacks, tall and thin, were often by-passed by the blast. On the other hand, quirks of pressure produced by the atmosphere produced havoc far beyond the circle where it was expected. At Nagasaki, barracks nearly five miles from ground zero collapsed to ground level.

In the strongest buildings of reinforced concrete, pressure on the outside walls may cause the roof or floors to buckle. The walls facing the blast may be dished inward. There will be uniformly heavy damage to false ceilings, partitions and plaster. Brick facings and cornices will be blown off into the streets, striking down the people caught outdoors.

Walls facing the blast may be dished inward.

Shed-type steel factory buildings will be bent over and blown apart, even when more than a mile from ground zero. Brick buildings, whose walls carry the entire load of construction, are among the most easily damaged. At distances up to 6,200 feet, they probably will collapse completely, taking with them everyone inside. Houses of wood at Hiroshima and Nagasaki were wrecked as far as 7,500 feet from the ground zero. The splintered wreckage kindled fires which followed.

Small steel-frame bridges were found to be quite resistant to blast, as were underground water mains, electrical conduits and gas lines. But damage to the water system through the breakage of pipes in houses and offices buildings will be one of the most serious effects of an atomic explosion. Overhead utility lines may be heavily damaged up to two miles from ground zero. Automobiles, buses and streetcars will be hit hard by blast and fire at distances up to a mile. In this country, atomic scientists believe, reinforced concrete buildings will be generally less resistant to blast than Japan's earthquake-proof buildings. But tall buildings having heavy steel frames such as office buildings and hospitals, should withstand the effect of blast quite well. For American-built frame houses, it is believed that the radius of structural blast damage would not exceed 7,500 feet -- a mile and a half from ground zero -- whereas at Nagasaki severe damage to houses extended out 8,500 feet. We build our homes better.

Damage to the water system through the breakage of pipes will be one of the most serious effects.

For an air burst over water rather than land, the shock wave is much the same. At Able Day at Bikini, ships suffered severe damage or were sunk 3,000 feet from the point directly beneath the blast. Minor damage occurred out more than a mile.

UNDERWATER OR UNDERGROUND EXPLOSION

In an underwater or underground atomic explosion, however, the action of the shock wave is entirely different. "There are no actual experiences upon which to base conclusions (about an underground burst)," the AEC reports, disregarding Soviet Russia's claim that it set off an atom bomb and moved a mountain.

Blast damage from an underground or underwater atomic explosion is expected to be less than that from an air burst. If a nominal atomic bomb were exploded 50 feet down in ordinary soil, a crater 800 feet across and 100 feet deep would be blown open. A bomb such as the Baker Day explosion, at Bikini, detonated underwater at shallow depths, would throw tremendous quantities of water into the air.

Office buildings and hospitals should withstand the effect of blast quite well.

Both the soil and the water from such bursts would be intensely radioactive. In these two cases, danger from longlasting radiation is expected to be greater than from any other source. The explosion's heat will be absorbed entirely by the material around it. And while blast damage will be done, the scientists have calculated the greatest blast damage is produced by a bomb exploded about 2,000 feet in the air.

EFFECT OF AIR BURST

At that height, chances of any one surviving within 2,600 feet -- half a mile -- are very poor, the scientists say bluntly. Persons within that circle will either be killed by the blast wave, crushed by falling buildings, burned to death or given a greater-than-lethal dose of radiation.

A crater 800 feet across and 100 feet deep would be blown open.

While the blast wave will take about 10 seconds to travel the two miles in which it does damage, the heat wave of an atomic blast lasts only three seconds. It will set flash fires and char combustible materials. Human beings exposed to it will receive more or less serious skin burns if within two miles of ground zero. At 4,000 feet, roof tiles will bubble and blister.

The heat will roughen polished granite, set fire to dark clothing and burn rubber tires a mile from the blast.

This radiant heat travels only in a straight line. Protection from it is afforded by almost any object. Clothing shields the body. The shadow of a tree trunk will be untouched by the heat. It is this phenomenon which produced the "profile burns" on buildings or human beings. It sears only where a surface is within line-of-sight from the explosion.

The shadow of a tree trunk will be untouched by the heat.

Burns from flash heat and the fires produced by the heat caused more than half the deaths and three-quarters the injuries at Hiroshima and Nagasaki. There were no fire departments after the explosions. Water pressure in the city mains was practically zero. Twenty minutes after the blast came the "fire storm," wind blowing into the holocaust from all directions, blowing 30 to 40 miles an hour at its height.

This is not all. The atomic scientists estimate that at 3,000 feet from the bomb's burst, there is better than 50 percent chance you will be killed by nuclear radiation, even if you are shielded by 12 inches of concrete. This is the effect of the deadly rays you cannot see. Neutrons and gamma rays are the dangerous particles of energy in this wave.

Gamma radiation will kill at 4,200 feet from the burst.

Gamma radiation (X-rays) from a nominal atomic bomb will kill at 4,200 feet from the burst. Neutrons are not quite so far-reaching, but they will deliver a lethal dose as far as half a mile from ground zero. Shielding from either of these particles is a matter of reinforced concrete by the foot, or solid lead inches thick.

RADIATION SICKNESS

A lethal dose of radiation from the immediate blast will have these effects: Varying degrees of shock, possibly within a few hours; nausea, vomiting and diarrhea in the following day or two; then fever. Often there will be no pain in the first few days, but merely discomfort, depression and fatigue.

The early stages of radiation sickness may be followed by two or three days when the patient is free from all symptoms, although profound changes are taking place meanwhile in his body. Then the earlier symptoms reappear. Active illness is soon followed by delirium, coma and finally death, which comes within two to three weeks. Infection, internal bleeding, swelling of the throat glands, loss of hair and degeneration of the sex organs are all apt to occur.

AEC scientists and genetics experts are extremely cautious in discussing one vital question: Will the children and grandchildren of atomic victims be human monsters? Chromosomes and genes, biological factors which control heredity, are changed by radiation. But how much are they changed? Is there serious danger that these changes can be passed along to the next generation, or those which come after that?

Risk of passing on any changes in the chromosomes can be reduced if atomic victims "refrain from begetting offspring for a period of two or three months following exposure," the reports states. However, this precaution probably would not lessen the chances, if they exist at all, of passing on changes in the genes. Until large gaps in man's knowledge of radiation and its genetic effects can be closed, admit the scientists, estimates of what can or may happen in this field from atomic explosions will be little better than guesses.

AFTER-EFFECTS OF BOMBING

Will the bombed city be left an echoing ghost town.

Will the bombed city be left an echoing ghost town, too "hot" with radioactivity to be entered? If the bomb explodes high in the air, the AEC report says, this hazard will be very small. The radioactive residue of the bomb itself will fall to earth, but the small amounts of these fission products and the wide area over which they will be dispersed lead military men to discount almost completely any real danger from them.

Some dirt and dust will be sucked up into the boiling cloud of an atomic explosion, but this too will travel far and come back to earth spread over many miles. However, the "base surge" of water from an underwater explosion, or the great clouds of dirt thrown by a bomb exploded at street level or beneath the surface, will be intensely radioactive. Lethal levels of radiation in the wake of such bombs are possible and must be guarded against, the scientists warn.

If an atomic bomb were a fizzle, unexploded radioactive material might settle over a limited area in high enough concentrations to be dangerous. Such fizzles are possible. If the two lumps of fissionable material do not come together just right, the bomb might explode only partially, breaking apart and scattering its substance into the air.

Radioactive materials might be deliberately sown without an explosion.

Radioactive materials might be deliberately sown without an explosive taking place, as a new weapon of war. Such materials can and are being made constantly in the normal operation of atomic piles. Small amounts of certain elements can be made to give off tremendous amounts of radiation when so treated. If these were to be spread uniformly over a limited area, that area might be denied for human habitation for a considerable period of time. Those who remained within the area would be poisoned in much the same way that nuclear radiation from an exploding bomb strikes the human body. Even if great numbers of people are not directly killed, even if large areas are not laid waste as by direct atomic explosion, the panic-inspiring potential of radiological warfare as a "mystery weapon" makes it a grim possibility which must be taken into account in civilian defense planning.

The blast of an atomic bomb is more violent, but methods of dealing with explosion damage, fire and rescue of the injured were developed long ago, and are not changed by the mere fact that an atomic blast is stronger than ordinary TNT explosions.

Panic is a major danger of atomic bombing.

But in combating the radioactivity that comes with atomic bombing, new hazards and new ways to meet them must be planned for. Rescue crews and monitoring teams must have instruments to show them where dangerous levels of radioactivity have been left. They must know the length of time a human being can remain in buildings and rubble-strewn areas left radioactive. They must know new techniques of decontamination.

They must know how to deal with panic, for scientists are agreed that panic is the major danger of atomic bombing. "Mass hysteria could convert a minor incident into a major disaster," they say.

The first atomic bomb at Hiroshima killed 78,150 people. This is far from a "minor incident." But if an American community -- anywhere -- were atom-bombed, panic would strike 80 out of 100 of the physically unharmed survivors. Tens of thousands of thousands of Americans might be struck down by sheer terror, making vastly more difficult the job of meeting atomic attack. The great industrial centers of the nation might suddenly become empty shells as the people fled from A-bombs yet to come.