Solar Unit

The Sun

• Is about 93 million miles from Earth.• Is the source of most energy on Earth.• We couldn’t live without it.• Moonlight is just sunlight reflected off the

moon’s surface.

The Sun contributes to:

• The water cycle.• Formation of fossil fuels.

• The sun causes:– Wind (because of uneven heating by the sun)– Solar energy (can be converted into electricity!)

Solar videos

• 2 min solar flare/explosion

• 4 min fiery loop on the sun

• 3min 30 The surface of the sun as you have never seen it **

• solar eclipse

MORE SUN FACTS

• Hot ball of gases – ¾ Hydrogen, ¼ Helium• 109x greater diameter than the earth.• HOT – 5,500°C (surface) 15 million°C

(core)• Emits energy in different sized

waves. – Light (visible)–Heat (infrared - invisible)– Radio waves and X-rays (invisible)

• Heat sinkA material, such as water, that can absorb a large amount of heat and release the energy slowly.

• Solar energyEnergy from the Sun. This energy takes several forms, including visible light and infrared light that can be felt as heat.

Solar Vocabulary

• AbsorbTo take up, soak in, or capture.

• ReflectTo bounce back.

• Solar collectorA material used to capture solar energy in a water heater or other device.

• Elapsed timeThe difference between a starting time and an ending time.

• Energy transferThe change of energy from one form to another (such as light to heat).

• Energy transfer The movement of energy from one object to

another. A hot pan heating the counter it is set upon.

Why do dark colors get warmer faster?

• Dark colors do not exactly absorb more heat, but they do convert a higher percentage of light into heat.

• If you notice when heading out in the sun with a dark colored shirt it gets hot, where a lighter colored shirt would not get nearly as hot.

• This is due to the amount of light being absorbed by the color. The lighter the color the smaller the range of visible light being absorbed and converted into heat.

•White objects reflect all visible light, where black objects absorb all visible light.

• While color is a factor of light absorption, it is not the only factor. You will find that some dark objects remain cooler in direct sunlight then other lighter objects.

• This is due to the fact that there are other factors at play, maybe one material is a poorer insulator; possibly there is a shine to darker object, leading more light to be reflected as a result. If the material is the same, you will find that darker colors become hotter.

• Surface area - Surface area is the area of a given surface. Roughly speaking, it is the "amount" of a surface.

Questions for back of surface area lab.

1. How was water heated by solar energy in the past?

2. What was the Day and Night system, and what was it used for? 3. How do solar water heaters work today?

Heat Transfer

• Heat Transfer: Conduction, Convection, Radiation

More vocab from Nova – Saved by the Sun

• Greenhouse gas – Gases that can absorb and emit infrared radiation.

• By their percentage contribution to the greenhouse effect on Earth the four major gases are– water vapor, 36–70%– carbon dioxide, 9–26% * key one to be concerned about– methane, 4–9%– ozone, 3–7%

• This process (absorbing and emitting infrared radiation(is the fundamental cause of the greenhouse effect.

Carbon Dioxide

• Produced from animals breathing.• Produced from burning fossil fuels.• Produced from using energy (electricity) in our

homes (which mostly comes from coal – produces CO2 or nuclear power)

• The greenhouse effect is a process by which heat (thermal radiation) from earth is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions.

• Since part of this re-radiation is back towards the earth it results in a higher temperature.

• Carbon footprint - A carbon footprint has historically been defined as "the total set of greenhouse gas (GHG) emissions caused by an organization, event, product or person.

• Renewable energy- Renewable energy is energy which comes from natural resources such as sunlight, wind, rain, tides, wavepower, and geothermal heat, which are renewable (naturally replenished).

Nuclear power• Sustainable energy is the sustainable provision of energy

that meets the needs of the present without compromising the ability of future generations to meet their needs.

• Nuclear power- • Conventional fission power is sometimes referred to as

sustainable, but this is controversial politically due to concerns about peak uranium, radioactive waste disposal, and the risks of a severe accident.