There are many physical phenomena that occur naturally on Earth. They can occur due to freezing, heating, boiling, and some are characteristics of Earth. Science helps us explain these phenomena.
People can sing, but have you heard of sand that can sing too? Seems impossible, right? Singing sand is sand that can make sounds. The sound emission is caused by wind blowing over sand dunes as people walk on the sand.
In order for sound to emanate from sand, there are many requirements. First, the dunes must be barchans, a crescent-shaped type of sand dune. Second, the sand grains have to be round. They also have to be medium-sized, have the right level of humidity, and be made out of certain materials. The sound that is made sounds like a low rumble. It is accompanied by an avalanching movement of sand. This natural song can reach up to 105 decibels. How loud is that? A toilet flushing is at 75-85 decibels. A baby crying is at 110 decibels.
Earth is a special planet. Its characteristics allow freezing, heating, and boiling to occur. Freezing refers to the solidification of liquid or gas into a solid form. Think about your favourite popsicles. They are made by freezing fruit juices. Freezing can also occur naturally on Earth. Have you ever ice-skated on a frozen lake? Water freezes due to the low surrounding temperatures; latent heat is released from the liquid until it freezes.
Boiling is another physical phenomenon that happens on Earth. Boiling is the vapourization of a liquid. When the vapor pressure of the liquid is equal to pressure on the liquid from the atmosphere, the liquid reaches its boiling point. The boiling point is not the same for every liquid. For example, water boils at 100°C, but mercury boils at 356.9°C!
Boiling water has many uses. It is nice to make a warm drink, and it helps us cook food. But there is an even bigger benefit. Boiling water kills microbes and makes it drinkable. The sensitivity of different microorganisms to heat differs, but if you boil water for 1 minute, most viruses become inactive. If you don't know if water is safe to drink, boil it first!
If you hold a pen, and then let go. What happens? The pen drops. This is because of gravity. We cannot see gravity, but we can see what it does to objects around us. That's why we can stay in our seats and walk on the ground. Gravity is important; without it, we would fly off Earth. It is also why all our planets gravitate towards our Sun.
Modern studies on gravity began in the 16th and 17th centuries. Galileo Galilei studied gravity by rolling balls down inclines and taking measurements. Sir Isaac Newton then took it further in 1687. He hypothesized that every mass attracts every other mass in the universe. This is known as Newton's law of gravitational attraction. His equations are still used today.
Refraction is the change in direction of a wave passing through one medium to another. Although sound and water waves experience refraction, it is easiest to see in light. It can look like objects are bending because of the change in speed and direction of the wavelengths!
Earth is full of wonder, and science helps explain the world around us. Is there anything that amazes you about the world?