Why are Bubbles Round?
All of us enjoy playing with soap water bubbles. Have you ever thought about the round shape of the bubble? There is surface tension on the bubble’s skin. It is this force that keeps the bubble pulled in as tightly as it can. As air molecules trapped inside the bubble move around in all directions, its skin tends to form a sphere. This is because sphere is the shape with the least amount of surface area compared to the volume of air trapped inside. Nature always chooses the most economical shape to hold the volume of air inside.
What Makes Wood Float, but Stones Sink?
The answer lies in density. Density is a measure of how closely packed the particles in an object of a certain volume are. If you were to fill a space with water that was the same volume as one filled with wood, the space filled with wood would be lighter as it contains less mass. Those things that are less dense than water will float, while those that are more dense sink.
How Does a Baby Kangaroo get Into the Pouch?
The young kangaroo, or joey, is born at a very immature stage. The newly born joey is only about 2 cm long and weighs less than a gram. Immediately after birth it crawls up the mother's body and enters the pouch. Since pouches are for babies to stay in, only female kangaroos have them.
How Many Stars Are in the Sky?
Star is a ball of gas, burning with extremely high temperature, because of giant nuclear reactions. Our sun is a star. In our home galaxy, the Milky Way, it’s estimated there are nearly 100 billion stars. It is also estimated that there are nearly 100 billion galaxies in the universe. Stars are constantly dying and new ones are being born. So don’t expect to ever get an exact number!