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Solar Energy Earth

Lauren Said:

Will Mass of Earth change after receiveing solar energy ? Will Earth Explode finally ?

We Answered:

We have been bombarded by solar energy for 4.4 billion years. I think there might be something wrong with your understanding of how physics works.

Namely, the Earth is not a closed system. The sun shines on us, we shine back. We shine out just as much as the sun shines in. Because of the anthropic principle (we can only see something if it allows us to exist), this balance makes the Earth have a temperature of 14 degrees Celsius - providing liquid water and a survivable habitat. There is a balance, because hotter objects emit more radiation. Mercury's temperature (on the day side) is 180 degrees Celsius. Venus' would be 90 degrees, but it's different because of the greenhouse effect. On mars, it's -20 C. Etc. etc. The further away from the sun, the less energy you get from the sun, and therefore the less warm you have to be to maintain balance.

Also, why would the Earth explode if it's mass increases? Jupiter didn't, and it's tens of thousands times heavier than Earth.

Ashley Said:

what are some factors that affect the amount of solar energy that reaches the Earth's surface?

We Answered:

Solar energy to human and to entire planet ... are two different categories. Solar energy for human means, the direct sun light humans use to convert into electricity and that solar energy is affected by following four factors ----- 1) rain clouds which are dark in nature and block most of the sun light 2) dust particles within city area, ash particles in coal burning areas 3) fog/smog mostly during winter season which blocks visibility also 4) other pollutants like smoke/fuel emissions/vehicle and industrial air pollutants

For the solar energy to plants/animals/entire planet the four factors are --- 1) dust particles 2) green house gases which brakes the ozone layer and brings harmful ultra violate light inside the earths atmosphere instead of clear and healthy sunlight 3) other pollutants like smoke/fuel emmissions/ vehicle and industrial air pollutants(pollution created by humans) 4) clouds/fog/smog mostly during winter season which blocks visibility also

Brandon Said:

how does the angle of insulation ... affect the how much solar energy the Earth absorbs?

We Answered:

Its directly proportional to the inverse of the tangent.

Christian Said:

How does the angle of insulation ... affect the how much solar energy the Earth absorbs?

We Answered:

The angle of insolation has several effects on absorption of solar energy.
* Geometric effect is that a tilted surface spreads the energy over a larger area; such as near the north or south pole where shadows are very long due to the low angle of the sun. This can be worked out precisely in terms of angles using trigonometry
* Atmospheric path length changes absorption location (more in the atmosphere) so at sunset even an object facing the sun (normal incidence) receives very little energy. This is much more complicated than the geometry effect because it depends on dust and water vapor, clouds or "haze" etc.
* Reflection changes. This is significant over the oceans where when the sun is low in the sky nearly all light is reflected off the water - Calculations for an ocean with no waves is pretty straight forward, but the real situation is that the sea surface is not flat and the actual effect is difficult to model.

The other critical factor is albedo or overall reflection of the planet. Here we think of snow, clouds & water vapor, dust, etc. Although many of these are also related to (or effected by) angle, the vary in their own right.

Fred Said:

how does the amount of clouds cover the amount of solar energy that reaches the earth?

We Answered:

Clouds reduce the amount of solar energy reaching the earth. But they also reflect radiated energy that would otherwise be emitted into space from the earth.

This is called the greenhouse effect because, like the glass in a greenhouse it reduces the heat getting in but is very effective in preventing it from escaping so that the temperature inside the greenhouse becomes higher than the temperature outside.

Clouds are not the only greenhouse gas. Carbon dioxide is another and, unfortunately, because we have been burning a lot of fossil fuels since the industrial revolution, the proportion of carbon dioxide in the air has been rising. This is leading to global warming which will have catastrophic effects unless we stop it.

There are those who say the increase in carbon dioxide is insignificant and can not lead to global warming but I get the impression they are fooling themselves so they can continue with business as usual. They say that governments are trying to scare us so they can collect more taxes. That doesn't make sense to me because politicians do not make themselves popular by giving us bad news.

Best wishes

Crystal Said:

Flux of solar energy earth receives from the sun?

We Answered:

Why did you have doubts about your answer? You did everything correctly.

Actually, the answer from the figures above is 1343.9 W/m^2, but the input is way too imprecise to worry about this level of precision. You might as well round the answer to about 1340 W/m^2. (Note that the abbreviation for "watt" is an uppercase W, not lowercase.)


Just so you understand the meaning of this number: If a 1x1 meter solar panel on the roof of a house receives the sun's rays perpendicularly, it could in principle provide 1300 watts of power -- more than enough to power everything in a house in many instances (although not enough to power a 1500 watt space heater). In reality, however, solar panels are much less than 100% efficient; that's why you need a whole roof full of solar panels.

Also, the number you calculated is the energy flux reaching the earth's outer atmosphere, but the amount that penetrates to the surface is a bit less.

--- edit

The units are pretty straightforward, since luminosity is in watts and distance in meters. Obviously, you could have used any other unit of distance (including AU), but W/m^2 is a convenient unit for use on earth.

This flux is known as the solar constant (although it's now known to vary by about 0.1% with the sunspot cycle). In the old days of astronomy, it was commonly expressed in these very weird units:
1.92 calories/minute/cm^2

Here's a 1911 paper that uses these units:…

It's interesting to look at the first page of this paper; it's much more qualitative and far less intimidating than a typical paper published today. (But note that the paper is mostly incorrect. It wasn't until very recent years that we were able to accurately measure that the sun emits 0.1% more energy at solar maximum than solar minimum. The measurements discussed in this 1911 paper are wrong!)

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