The phrase that goes to the very heart of the problem is “very little kindling,” which is another way of illustrating the difficulty of lighting a fire in a high wind when you have only one match. We know that to ignite deuterium, by far the cheaper and more abundant of the two H-bomb elements, a temperature comparable to those existing in the interior of the sun, some 20,000,000 degrees centigrade, is necessary. This temperature can be realized on earth only in the explosion of an A-bomb. We also know that the wartime model A-bombs generated a temperature of about 50,000,000 degrees, more than enough to light a deuterium fire. The trouble lies in the extremely short time interval, of the order of a millionth of a second (microsecond), and a fraction thereof, during which the A-bomb is held together before it flies apart. In the words of Professor Bacher, we must make our green, ice-covered wood catch fire in the subzero mountain weather before the “very little kindling” we have is burned up. The times at which deuterium will ignite at any given temperature, in both its gaseous and its liquid form, are widely known among nuclear scientists everywhere, including Russia, through publication in official scientific literature of a well-known formula, originally worked out by two European scientists as far back as 1929, and more recently improved upon by Professor George Gamow and Professor Teller. By this formula, derived from actual experiments, it is known that deuterium in its gaseous form will require as long as 128 seconds to ignite at a temperature of 50,000,000 degrees centigrade, well above 100,000,000 times longer than the time in which our little kindling is used up. This obviously rules out deuterium in its natural gaseous form as material for an H-bomb. How about liquid deuterium? We know that the more atoms there are per unit volume (namely, the greater the density), the faster is the time of the reaction. The increase in the speed of the reaction (in this case the ignition of the deuterium) is directly proportional to the square of the density. For example, if the density, (that is, the number of atoms per unit volume) is increased by a factor of 10, the time of ignition will be speeded up by the square of 10, or 100 times faster. Since liquid deuterium has a density nearly 800 times that of gaseous deuterium, this means that liquid deuterium (which must be maintained at a temperature of 423 degrees below zero Fahrenheit at a pressure above one atmosphere) would ignite 640,000 times faster (namely, in 1/640,000th part of the time) than its gaseous form. Arithmetic shows that the ignition time for liquid deuterium at 50,000,000 degrees centigrade will be 200 microseconds, still 200 times longer than the period in which our kindling is consumed.