|Fig. 1: Figure illustrating the relative blast radii of several explosions. (Source: Wikimedia Commons)|
Both fission and fusion are nuclear reactions that produce vast amounts of energy from very small amounts of matter. A "nuclear weapon" is an explosive device that is specifically used for destructive purposes and derives its energy from such nuclear reactions. The amount of energy released by a particular bomb or reaction is measured by the TNT equivalent. The conventional way of measuring energy is "ton of TNT", (4.18 × 109 joules) which is approximately the amount of energy released in the detonation of a ton of trinitrotoluene. Traditionally, kiloton and megaton of TNT are used to denote the destructive power of nuclear weapons. The amount of thermodynamic work energy of detonation for TNT has been accurately measured at 4686 J/g. 
Tsar Bomba (Russian for Tsar of bombs) is the epithet for the AN602 Hydrogen bomb, the most powerful nuclear weapon ever detonated in the history of mankind. The Tsar Bomba was also referred to as "Kuz'kina Mat'", which translates to "Kuzka's mother".  This is a part of a Russian phrase which most closely translates to "to teach someone a lesson". (The Soviet Union wished to teach the United States a lesson.)
The "Tsar Bomba" was the culmination of a series of "high-yield thermonuclear weapons" designed by the Soviet Union and the United States during the 1950's. The bomb had a yield of 50 megaton TNT. The magnitude of this explosion is equivalent to
10 times the combined power of all the conventional explosives used in World War II
1,350-1,570 times the combined power of the bombs that destroyed Hiroshima and Nagasaki
One-tenth of the combined yield of all nuclear tests to date. 
A graphical representation of the blast radius of the impact of the different bombs is illustrated in figure 1. Today, we can see the impact of Fat Man on Nagasaki even today, and we can hardly imagine what the impact of the Tsar Bomba would be.
The Tsar Bomba was tested on October 30th 1961 in the Novaya Zemlya archipelago, at Sukhoy Nos 2.
The initial design was capable of yielding 100 Mt (megaton) of energy, but this design was abandoned because it would cause too much of a radioactive fallout and would have destroyed the plane carrying the bomb before the latter could move out of the explosion radius. As a result, the tamper, which was originally made with U-238, was replaced with lead. As a result, the free neutrons from the second stage were absorbed by the lead. If Uranium were used for the tamper, the atoms would undergo fission and greatly amplify the magnitude of the explosion.
The bomb was attached to a parachute so that the Tu-95V release plane had enough time to escape the blast radius. The bomb was designed to detonate at a height of 4 km over land surface.  The recoil from the blast prevented the fireball from hitting the ground as originally calculated. The mushroom cloud that was generated was over 64 km high and 40 kilometers at base (the cap of the mushroom cloud was 95 kilometers wide). Houses in districts hundreds of kilometers away were destroyed, and radio communication was interrupted for over an hour. The heat from the explosion resulted in third degree burns on people 100 km away from the point of impact. The blast damage resulted in glass shattering as far as Norway and Finland. The blast was recorded at 8.1 on the Richter scale (but the energy was not converted to seismic waves since the bomb was detonated in the air rather than underground. 
© Surya Narayanan. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 P. W. Cooper, Explosives Engineering (Wiley-VCH, 1996), p. 406.
 V. Suvorov, Kuz'kina Mat': A Chronicle of the Great Decade (Dobraya Kniga, 2011) [В. Суваров, Кузькина Мать (Добрая Книга, 2011)].
 G. J. DeGroot, The Bomb: A Life (Harvard U. Press, 2006), p. 254.
 V. Adamsky and Y. Smirnov, "Moscow's Biggest Bomb: The 50-Megaton Test of October 1961," Cold War International History Project Bulletin, Issue 4, Woodrow Wilson International Center for Scholars, (Fall 1994), p. 3.
 E. Farkas, "Transit of Pressure Waves Through New Zealand From the Soviet 50 Megaton Bomb Explosion," Nature 193, 765 (1962).