Why did Sputnik alarm the U. S.

Sputnik was launched in 1957, during the cold war, when there was a high distrust and mutual fear between the US and the Soviet Union. Sputnik had demonstrated the seemingly superior development of US industry, which scared the US, as it showed that their enemy was stronger. Additionally, it fueled the so-called missile gap, that is the belief that the Soviet Union had a lot stronger arsenal of nuclear weapons.