In 1957, the USSR launched the Earth's first artificial satellite. It was called:

Sputnik 1 was the world's first artificial satellite. It was launched by the Soviet Union (USSR) on 4 October 1957 from the Baikonur Cosmodrome (now in Kazakhstan), using an R-7 rocket.

About Sputnik 1:

• "Sputnik" means "fellow traveller" or "satellite" in Russian.
• It was a polished metal sphere about 58 cm in diameter, weighing about 83.6 kg, with four long radio antennas.
• It orbited the Earth about once every 96 minutes and sent out simple radio "beep" signals that could be picked up by radio operators around the world.
• Its batteries ran out after about three weeks, and it burned up when it re-entered the atmosphere in January 1958.

The launch of Sputnik 1 started the "Space Race" between the USSR and the USA during the Cold War. It shocked the United States, which responded by setting up NASA (the National Aeronautics and Space Administration) in 1958 and greatly increasing spending on science education.

Other space "firsts":

• Sputnik 2 (November 1957): carried the dog Laika, the first animal to orbit the Earth.
• Explorer 1 (31 January 1958): the first US satellite; it discovered the Van Allen radiation belts.
• Luna 1 (1959): the first spacecraft to reach the vicinity of the Moon.
• Vostok 1 (12 April 1961): carried Yuri Gagarin, the first human in space.
• Valentina Tereshkova (1963): the first woman in space.
• Apollo 11 (20 July 1969): Neil Armstrong became the first human to walk on the Moon.
• Aryabhata (1975): India's first satellite, launched by the USSR.
• The UN's World Space Week is celebrated from 4 to 10 October every year, marking the launch of Sputnik 1 (4 October 1957) and the signing of the Outer Space Treaty (10 October 1967).

Why not the other options?

• ✗Explorer 1 was the first US satellite (1958).
• ✗Vostok 1 carried Yuri Gagarin into space (1961).
• ✗Luna 1 was the first spacecraft to reach the Moon's vicinity (1959).