The Sun’s Energy

I. Our sun is a medium yellow star about 4.6 billion years old. A. All of the hundreds and billions of stars are classified based on their size, brightness and temperature.

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1. Stars range in mass with some stars having 150 times the mass of our star (the sun). These massive giant stars will have a shorter life span than our sun because they start off with much more mass (hydrogen and helium).

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Since stars create their energy by nuclear fusion, these giant stars will burn out much quicker.

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2. Our sun has an estimated life span of 10 billion years. That leaves us over 5 billion years because life on Earth cannot exist without the energy that we get from the sun.

II. Nuclear fusion is the process of combining 2 hydrogen (H) nuclei and creating a helium (He) atom. When the two nuclei combine, a great deal of energy is released.

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Nuclear fission is the opposite of nuclear fusion. Nuclear fission is the splitting of an atom, the same thing we do in a nuclear power plant. In contrast to fusion, which uses H for fuel, heavier elements such as uranium are used for nuclear fission.

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III. It is believed that the sun formed when gravity pulled together a vast cloud of gas and dust, from which the Earth and other planets also arose.

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A. The gravitational pull released energy and heated the early Sun. Heat is the motion of atoms and molecules: the higher the temperature, the greater is their velocity and the more violent are their collisions.

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B. When the temperature at the center of the newly-formed sun became great enough for collisions between nuclei they began to stick together and H protons were combined into He.

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C. This released nuclear energy and kept up the high temperature of the sun's core, and the heat also kept the gas pressure high, keeping the Sun puffed up and stopping gravity from pulling it together any more.

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1. Each second 700,000,000 tons of H are converted into gamma rays.

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2. The energy in the core is transferred by radiation until it gets to the last 20%, then the energy travels in the sun’s convection currents until it reaches the surface.

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3. As the gamma rays travel from the core of the sun to the surface, the energy is continuously absorbed and re-emitted at lower temperatures. So when it reaches the surface it is primarily visible light.

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4. The fuel that drives the cycle is H with gravity pulling it together. At present the sun’s mass is made of 70% H and 28% He.

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5. The sun’s energy travels to the Earth in the form radiant energy.

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IV. Energy has a number of different forms, all of which measure the ability of an object or system to do work on another object or system.

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A. Electromagnetic energy is the energy that comes from electromagnetic radiation. This radiation is composed of waves, such as radio waves and visible light that move at the speed of light in a way that is suggestive of both waves and particles. We call these particles of light photons. Electromagnetic radiation causes both electric and magnetic fields

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1. Only a small part of the electromagnetic field is visible; this part of the electromagnetic spectrum is known as the visible spectrum.

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a. Life on Earth is made possible by the energy in visible light. Photosynthesis is the beginning of the food chain.

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That means they can use the solar energy along with some elements and convert that energy into chemical energy that is stored in food.

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i. Plants, algae and some bacteria can absorb certain frequencies of light and turn it into glucose which is the base of the food chain.

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ii. The formula is:

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2. There are many forms of electromagnetic energy including gamma rays, x-rays, ultraviolet radiation, visible light, infrared radiation, microwaves and radio waves.

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3. Some of the frequencies of light such as x-rays and infrared cannot penetrate the Earth’s atmosphere.

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4. The Earth is protected from ultraviolet rays by the ozone layer.

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a. Ozone (O3) is a layer in the stratosphere that stops UV radiation from reaching the surface of the Earth. Life on Earth could not exist without the O3 layer.

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b. The Earth’s magnetic field also protects us from other forms of solar radiation. It reaches well beyond the thermosphere and acts like a giant shield reflecting dangerous solar winds and radiation off into space.

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i. It is believed that the magnetic field comes from the core of iron in the Earth and the rotation of the Earth.

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Evidence from Venus supports this because Venus also has an iron core but not much of a magnetic field. Venus spins much slower than Earth which gives us evidence that it is the spinning of the Earth along with the iron core that gives us our magnetic shield.

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ii. Evidence from rocks shows that there have been multiple magnetic reversals over millions of years. This is called Paleomagnetism and the reason has not been discovered.

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V. The reason for the seasons is the tilt of the Earth. A. The Earth’s axis is tilted at an angle of 23.5o. This tilting is what gives us the four seasons of the year. Since the axis is tilted, different parts of the globe are oriented towards the sun at different times of year.

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1. Solstices occur twice a year in June and December. In June, the Earth is angled to receive the most sunlight. This is called summer solstice and is the longest day of the year.

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In December, the Earth is angled far from the sun’s rays and the shortest day of the years occurs. This is called winter solstice.

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2. Equinoxes also happen twice a year and occur when there is an equal amount of day and night. These occur in the spring and fall.

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3. The southern hemisphere will experience the opposite affect from the northern hemisphere.

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VI. Differential Heating of the Earth’s Surface:

A. If you have ever walked on a beach you know that the sand gets much warmer than sea water. Water is a slow conductor of heat, thus it needs to gain more energy than the sand or dry land in order for its temperature to increase.

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B. On the other hand, the land would cool much faster than the water. Earth’s oceans are far more important than the land as a source of heat energy which drives the weather.

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1. The oceans cover 2/3 of the Earth, they absorb more sunlight and store more heat and retain it longer.

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2. This solar radiation also penetrates the oceans to a depth of many more meters than the land.

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3. Water has to lose more energy than the land in order for the temperature to decrease.

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C. This causes air moving across the land and sea to move in currents.

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1. The rising of heated air pulls the cooler air into the volume it has vacated. This causes global air currents, local and global winds and directly affects the weather.

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Background for Presentation Credit: lucaskrech.com

The End