#322 Why do dragonflies have four wings?
Why do dragonflies have four wings? So that they can hover and fly in any direction that they wish. Most insects have two pairs of wings but the second set…
Why do dragonflies have four wings? So that they can hover and fly in any direction that they wish. Most insects have two pairs of wings but the second set…
#398 How does a pressure cooker work? How does a pressure cooker work? By using high pressure to raise the boiling point of the water. Pressure cookers were invented in…
How does a refrigerator cool food? By transferring the heat from inside the refrigerator to outside using evaporation. Fresh foods have to be kept cool to make them last longer.…
Why does metal spark in a microwave oven? The microwave charges one side of the metal positively and one side negatively. This charge can ionize the air, making sparks. First,…
How long has the Sahara been a desert? Possibly for 4.6 million years, but maybe as long as 7 million years., The Sahara goes through a 41,000-year cycle. The Sahara…
How does crop rotation work? By alternating crops to give the soil a rest and to replace nutrients that are removed. People transitioned from a hunter-gatherer culture to an agricultural…
How does a steam engine work? By taking the energy contained in coal and making heat. Then using the heat to turn water into steam and using the steam to…
How tall could a skyscraper be? Theoretically 69.1 km tall, but practically, about 2 km. The tallest building in the world at the moment is the Burj Khalifa. It is…
When did the Egyptian Empire start to decline? It peaked during the reigns of Ramesses II and Ramesses III from 1279 BC to 1155 BC) and then began to decline.…
Where did the names of the continents come from? Generally, from Greek and Latin. There are seven continents and one continent that is almost completely underwater. In order of size,…