What Are the Two Most Important Factors in Temperature?

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Questions:

•What is temperature? •What are the two most important factors in temperature? •Why is it usually cooler at night? •Why does temperature change during the seasons?

Air temperature is one of those things that everyone is familiar with, which turns out to be more complicated than it might seem at first. History of the Thermometer

In order to truly understand temperature, we must first understand how a thermometer works. A thermometer is a device that measures the temperature of things. The name is made up of two smaller words: "Thermo" means heat and "meter" means to measure. You can use a thermometer to tell the temperature outside or inside your house, inside your oven, even the temperature of your body if you're sick.

Thermometers usually have a bulb at the base of the thermometer with a long glass tube stretching out the top. Early thermometers used water, but because water freezes there was no way to measure temperatures less than the freezing point of water. So, alcohol, which freezes at temperature below the point where water freezes, was used.

The red colored or silver line in the middle of the thermometer moves up and down depending on the temperature. The thermometer measures temperatures in Fahrenheit, Celsius and another scale called Kelvin. Fahrenheit is used mostly in the United States, and most of the rest of the world uses Celsius. Kelvin is used by scientists.

Fahrenheit is named after the German physicist Gabriel D. Fahrenheit who developed his scale in 1724. Water freezes to ice at 32 degrees Fahrenheit (F for short), and water boils at 212 degrees F. He arbitrarily decided that the difference between the freezing point and boiling point of water should be 180 degrees. The Celsius scale is named after Anders Celsius. The Celsius scale used to be called the "centigrade" scale. Centigrade means "divided into 100 degrees." Anders Celsius developed his scale in 1742. He started with the freezing point of water and said that was 0 degrees Celsius (C for short). At the point where water boils, he marked that at 100 degrees C. This scale is much more scientific because the measurement is broken down into an even 100 degrees. This is similar to the scientific system of measuring distance and weight called the metric system.

Kelvin is named after Lord Kelvin, whose full name is Sir William Thomson, Baron Kelvin of Largs, Lord Kelvin of Scotland. His scale starts at 0 degrees Kelvin, which is called absolute temperature.

Lord Kelvin took the idea of temperature one step further with his invention of the Kelvin Scale in 1848. The Kelvin Scale measures the coldest temperature there can be. He said there was no upper limit of how hot things can get, but he said there was a limit as to how cold things can get. Kelvin developed the idea of Absolute Zero. This is at minus 273.15 degrees Celsius (or -459.67 F)! At this temperature, absolute zero is the lowest possible temperature, occurring when no heat energy remains in a substance. Absolute zero is the point at which molecules stop moving. As far as scientists know, nothing in the universe can get that cold! How does a thermometer work?

When you look at a regular outside bulb thermometer, you'll see a thin red or silver line that grows longer when it is hotter. The line goes down in cold weather. This liquid is sometimes colored alcohol but can also be a metallic liquid called mercury. Both mercury and alcohol grow bigger when heated and smaller when cooled. All matter is made up of moving particles and when warmed, these particles move faster. As the particles move they collide and spread out. Inside the glass tube of a thermometer, the liquid has no place to go but up when the temperature is hot and down when the temperature is cold. Numbers are placed alongside the glass tube that mark the temperature when the line is at that point. Temperature is a measure of the average kinetic energy (or energy of motion) of the various gas molecules that make up the air around a thermometer. The other type of common thermometer is a "spring" thermometer. A coiled piece of metal that is sensitive to heat is used. One end of the spring is attached to the pointer. As the air heats, the metal expands and the pointer moves higher. As the air cools, the metal contracts and the pointer moves lower. Typically, these types of thermometers are less accurate than bulb or digital thermometers. What factors affect temperature?

Temperature is affected by many things. Latitude is one of the main factors affecting temperature. Latitude is the measurement of the distance of a location on the Earth from the equator. The farther away from the equator that you are, the less direct sunlight a location receives. Since Earth is round, not every place receives the same amount of sunlight, or heat.

Another reason is due to the angle of solar incidence, this is the angle at which the Sun's rays strike the Earth's surface. At the Equator, the Sun's rays strike the Earth at a right angle, which makes the heat more intense and concentrated over a small area. Less heat is lost to the atmosphere as the rays travel a shorter distance through the atmosphere.

At the poles, the Sun's rays strike the Earth at an acute angle (less than 90 degrees), this spreads the heat over a larger area. More heat is lost to the atmosphere as the rays travel a longer distance through the atmosphere. Another factor that affects temperature is altitude. The Earth's surface absorbs most of the heat from the sun. Then, as the Earth's surface warms up, the heat spreads into the lower layers of the atmosphere, and transfers some of the heat to the upper layers of the atmosphere. As the air heats up, it expands and becomes less dense, then becomes lighter, causing it to rise up above the cooler air. As it does this, the air continues to expand. This is because there is less pressure higher in the atmosphere, allowing the air molecules to spread out more. So, the higher one travels into the troposphere, the lower the temperature becomes. Temperatures drop in the troposphere at a rate of 3.6 degrees for every 1,000 feet, or 6.5 degrees Celsius for every 1,000 meters.)

The other factors that impact temperature include cloud cover, distance from the sea, wind and ocean currents, and the length of day.

Why is it cooler at night?

An object will cool as long as it emits more energy than it receives. An object will warm as long as it receives more energy than it emits. Therefore, the heating or cooling of an object is cumulative. The amount of energy that has been taken away or received over a period of time determines how much an object will warm or cool. Take the earth's surface for example on a clear day. The sun has warmed the surface during the day. Once the sun goes down, the earth's surface will begin to cool (energy emitted is greater than energy received). This causes the earth's surface to become progressively cooler during the night. The earth's surface is not coldest right after sunset and not coldest in the middle of the night. It is coldest in the early morning hours around sunrise. This is because cooling is cumulative. The longer an object emits more energy than it receives, the more it will cool.

Why does temperature change during the seasons?

Why is it hot in the summer and cold in the winter? This is primarily due to the fact that the earth is tilted on its axis. Many people believe that the temperature changes because the Earth is closer to the sun in summer and farther from the sun in winter, but this is not the case! In fact, the Earth is farthest from the sun in July and is closest to the sun in January!

During the summer, the sun’s rays hit the earth at a steep angle. The light does not spread out as much, thus increasing the amount of energy hitting any given spot. Also, the long daylight hours allow the Earth plenty of time to reach warm temperatures.

During the winter, the sun’s rays hit the Earth at a shallow angle. These rays are more spread out, which minimizes the amount of energy that hits any given spot. Also, the long nights and short days prevent the Earth from warming up. Thus, we have winter!