chapter V
chapter VI
of the
Sakharov's broad scientific outlook included not only physics. Starting in 1956, Sakharov's attention was concentrated on the biological effects of nuclear tests.
Following the US, the USSR, France, Great Britain, China, India, Pakistan, and North Korea became nuclear powers.
Number of nuclear tests throughout the world from 1945 to 2000.
“In 1957, I wrote [...] an article, ‘Radioactive Carbon from Nuclear Explosions and Non-threshold Biological Effects.’ Work on it was an important stage in the formation of my views of the moral problems of nuclear tests”.
Andrei Sakharov. Memoirs
Sakharov's popular science article,”Radioactive Carbon from Nuclear Explosions and Non-threshold Biological Effects”. 1958. No. 20
Sakharov drew attention to the radioactive contamination of the biosphere, which emerges under nuclear tests in the atmosphere and under water, when the products of the explosions are strewn over great distances.
Even insignificant doses of additional radiation exposure  which does not kill people provokes so-called non-threshold biological effects — a general increase in morbidity and mortality which continues from generation to generation.
“I calculated that every megaton of test explosions in the atmosphere costs the lives of 10,000 people”.
Andrei Sakharov. Memoirs
Feeling himself responsible for the radioactive contamination of the planet, he set himself the goal to achieve an end to the dangerous tests.
When in July 1961, he tried to convince Khrushchev to refrain from the continuation of nuclear tests, Khrushchev was outraged.
“Sakharov, don't try to tell us what to do or how to behave. <...> I'd be a jellyfish and not Chairman of the Soviet of Ministers if I listened to people like Sakharov!”
Nikita Khrushchev, First Secretary of the CPSU Central Committee
© Bettmann / Getty
Soon, on 30 October 1961, at a Soviet polar testing ground, the most powerful thermonuclear device in the history of humanity was tested — AN602, the Tsar Bomba.
The explosion of the 50-megaton bomb occurred in the atmosphere at an elevation of 4,500. The flash was visible at a distance of 1,000 kilometers from the blast location.
The rocky soil at the test grounds fused like glass. Earth tremors were recorded by all the seismological stations on the planet. The shock wave went around the globe three times.
Clip of chronicle of Tsar Bomb tests. 1962.
Trinitite is a glass-like mineral which appears as the result of a nuclear explosion. It was first discovered at the site of the Trinity nuclear test in the USA in 1945.
Comparison of the might of the AN602 with other nuclear explosions
Work on designing thermonuclear warheads is conducted simultaneously by two secret scientific production centers — 11 (Arzamas-16) and NII-1011 (Chelyabinsk-70). By the fall of 1962, two competing design bureaus reach similar technical solutions. The question of which of them will be accepted for armament must be decided after the tests.
In September 1962, Sakharov tried to prevent  the subsequent testing of two nearly identical thermonuclear devices. He thought that damaging the biosphere was thoughtless and criminal. But he was deceived: after the first test, the second one was postponed to an earlier time in secret from him, so that he could not interfere with it.
“A terrible crime was about to be committed, and I could do nothing to prevent it. I was overcome by my impotence, unbearable bitterness, shame, and humiliation. I put my face down on my desk and wept. That was probably the most terrible lesson of my life: you cannot sit on two chairs at once!

I decided that I would devote myself to ending biologically harmful tests”.
Andrei Sakharov. Memoirs
In the practice of the great powers, the nuclear arms race was accompanied by peaceful rhetoric; however, the international negotiations on a total ban of nuclear testing had deadlocked due to the impossibility of monitoring underground nuclear explosions.
A breakthrough became possible only after Sakharov was able to convince Khrushchev of the possibility of banning at least the most dangerous tests – in the atmosphere, under water, and in space.
On 5 August 1963, the USSR, USA, and Great Britain signed the Treaty Banning Nuclear Weapon Tests in three environments.
© Bettmann / Getty
In the period of Khrushchev's thaw, Sakharov gradually moved away from work related to the creation of thermonuclear weaponry and returned to research in the field of theoretical physics.

At that time, political dissenters appeared in his social circle. His attention was increasingly drawn to human rights.
“Already by the late 1950s and especially in the 1960s, social issues began to occupy a greater and greater place in my world. They compelled me to speeches and actions, pushing into the background much else, even science to some extent”.
Andrei Sakharov. Memoirs