Who Invented the Jet Engine?
The first flight by a jet-propelled aircraft was made in Germany on august 27, 1939. Its engine was designed by Hans-Joachim von Ohain, who
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Air
Why Do Exhaust Fumes Contain Lead?
The lead in exhaust fumes comes from the petrol used to drive the internal-combustion engine. Crude oil straight from the wells is thick, bl
Why Do Stars Blink or Twinkle?
Stars blink or twinkle when we observe them (from the surface of the earth) because we are viewing them through different layers of turbulen
Why Do We Burp?
A burp (sometimes called a belch or by its medical term, eructation) is the release of gas from the digestive tract (in this case, the esoph
Why Does Frozen Food Keep Well?
Frozen food keeps for a long time because the freezing of the water inside the food forces the bacteria, which cause it to decompose, into i