On a very clear night it may be possible to see over 1000 stars without a telescope. No one knows how many stars there are in the universe.

Yes, we can have light without heat. The light from such reactions is called cool light. Many chemical reactions produce both light and heat. A burning candle is such a reaction. It is much less common for a chemical reaction to produce light without heat. Such chemical reactions are called chemiluminescent reactions, the most familiar of which occur in living …

Plants take in sunlight and combine it with carbon dioxide from the air and water and minerals from the ground. The energy of sunlight is stored in the leaves. Some of the sunlight gets stored underground. This stored sunlight is in the form of fossil fuels like coal and petroleum. Solar energy can be stored at high temperatures using molten …

When you pick up a pebble on the beach, it is hard to imagine that this solid material rock, can be bent just as though it were toothpaste. Throughout the world, however, you can find large areas of exposed rock that clearly show the evidence of bending. It is also important to realize that it is the bending and upheaval …

Bordering the southern edge of the Sahara is a region called the Sahel. It extends from Mauritania and northern Senegal through Mail, Burkina Faso, Niger and Chad into Sudan. The Sahel has an average annual rainfall of between 100 and 400 mm (4-16in) and, in the past, it was grazing land. From the 1960s, this zone has suffered droughts, so …

It is possible that people will be born in space and live their whole lives there. These space people will be human beings who have left Earth to live in space colonies. The colonies will be gigantic spacecraft, many kilometers across, in which there could be whole cities, together with fields and lakes. The colonies would grow their own food …

Strange as it may seem, the answer is yes. When you push or exert any king of force on something, it always exerts the same force back. You can demonstrate this by standing on a trolley or a boat and throwing something heavy away from you. The trolley or boat will move backwards. As you push on the objects to …

Yes when you ride on a very fast sledge or hear a spooky ghost story, for example. Being just a little frightened is part of being excited.

While in theory it may be possible, in practice it could be in very small amounts. In any case, tapping cosmic rays is a very complex engineering problem and the cost is very high.

If you look at a map of the Atlantic Ocean, you will see that the coastal shapes of the Americas resemble those of Europe and Africa. Might these continents have once been joined together like pieces in a giant jigsaw? A German meteorologist, Alfred Wegener (1880-1930), thought so. He wrote a book saying that, about 200 million years ago, all …