I presume you are asking about physics theories.
My judgement would be general relativity and quantum mechanics.
Both were developed mainly (in the former case, almost entirely) by German scientists.
yes
Nuclear fission happens spontaneously in nature. Uranium-235 does this, and is the only commonly occurring natural isotope that does. Nuclear fission can be induced by crashing a neutron into a fissionable atom. Some things other than Uranium-235 are fissionable, notably Uranium-238. Fission has been induced in various experiments. It happens in nuclear reactors and in nuclear bombs.
Albert Einstein developed the theories of general relativity and special relativity. He also did work in quantum theory. (He won a Nobel prize for his work with light.)
Nuclear fission was used in the atomic bombs dropped on Hiroshima and Nagasaki during World War II, leading to devastation and loss of lives. It was also harnessed for energy production in nuclear power plants, providing electricity to communities around the world.
Two planets are at their greatest separation when they are on opposite sides of the Sun. When a planet is at its greatest separation from the Earth the planet is said to be at superior conjunction. It cannot be seen until it has separated out from the Sun, which usually takes a few weeks at least.
The birth of the "new drama" in the twentieth century was aided by which two movements
It is two words.
Japan!
"In the twentieth century" - The prepositional phrase in this sentence is "in the twentieth century."
The Twentieth Century - 1957 Nehru Man of Two Worlds 9-12 was released on: USA: 6 March 1966
Mirabeau Olympe De Gouge
Leibniz was one of the two greatest mathematicians of the 18th century.
the first two decades of the twentieth century
Hugh Shannon has written: 'Two men of the twentieth century'
riding dune buggies
Nonfiction has become especially popular in the twentieth century because few people feel that they have enough leisure time to settle down for a whole afternoon or evening of reading.
They were the two architectural geniuses of the twentieth century.