On 4 October 1957 the Soviets launch Sputnik 1, the first ever artificial satellite.
This was also the first human object in space, a 58 cm metal sphere with 4 radio antenas. It was launched in an elliptical orbit and circled Earth every 1h36min.
Soviet scientist putting the final touches on the Sputnik 1
Sputnik was visible around sunset or sunrise with a pair of simple binoculars. It also transmitted a radio signal that could be picked up by amateur radio operators.
Although the object seems small, it had big consequences.
The US establishment was caught of guard by this USSR triumph. At the time they were working on launching a satellite of their own about 10 times smaller than the Sputnik 1. And it's launch was only planned for 1958.
The fact that it could be seen and listened to from Earth increased the urgency.
A year later NASA was formed as to increase the rate of progress.
This event is seen as the start of the Space Race or Space Age.
In January 1958, after 4 months of operation, Sputniks orbit deteriorated and the satelite burned up entering Earth's atmosphere.