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While solar panels can be used in multiple locations, areas with low cloud coverage and that receive large amounts of solar energy are best for solar panels.


Areas with low cloud coverage and that receive large amounts of solar energy are best for solar panels.

Solar panels can still produce energy on cloudy days, but they don't provide as much energy when compared to sunny days. Thus, areas with few cloudy days are best for solar panels.

The northwestern United States is typically known for it's rainy climate, and it does receive a lot of run. However, Portland, Oregon doesn't have that many more cloudy days than Miami, Florida (68 sunny days on average per year compared to 74 days-see here).

The amount of solar energy that reaches the solar panel is also going to effect how efficient it is and this varies across the globe. As you can see in the map below, light intensity is greater at the equator.

However, it is important to note that solar panels have limits in terms of their efficiency when it comes to sunlight intensity. After a certain temperature, the solar panel actually becomes less efficient (see image below). This is typically only an issue under very warm temperatures. For example, this might be a concern if you live in a desert.

Remember that solar panels work by using excited electrons that are knocked free from photons or light. As temperature increases, it takes less and less energy to knock these electrons free and thus less energy is transferred when the photon knocks the electron free.



Concentrated animal feeding operations (CAFOs) are widely used because they lower costs but they produce a lot of animal waste that isn't treated.


Concentrated animal feeding operations (CAFOs) are widely used because they lower costs. More animals can be raised in less space, and thus the output is maximized while costs are lowered.

In terms of environmental problems, CAFOs produce a lot of animal waste that needs to be handled properly. Whereas human waste is treated, animal waste or manure is not.

The manure produced by these animals includes whatever chemicals have been added to their feed, and these additions can result in nutrient concentrations that would not normally be found in the animals' manure or chemicals that wouldn't be present at all.
For example, because they are in such confined spaces, animals in CAFOs are at risk for diseases and may be given antibiotics in their food. Thus, if the manure is applied as fertilizer, this can pose a problem.

Waste can leach (dissolve into) into the soil and eventually contaminate the groundwater. Nearby lakes and streams can also be affected.

The image below shows waste ponds. If not carefully monitored, these ponds have the potential to contaminate the surrounding ecosystem through leaching and during particularly heavy precipitation events.

You can read more about CAFOs and their environmental problems here and you can read even more extensively about them here.



As carbon dioxide levels in the atmosphere increase global warming increases, assuming no other changes.


Apart from water vapor, carbon dioxide is the most abundant greenhouse gas in the atmosphere. Greenhouse gases allow energy from the sun to pass through and reach the Earth.

This radiation is primarily of wavelengths in the visible light spectrum (about half a micron). When the energy reaches the Earth it heats it up. The heated Earth is actually releasing energy as heat, but it is in a different wavelength (averaged at 11 microns). We refer to energy around that wavelength as infrared. Greenhouse gases block energy at that wavelength.

This is what the balance looks like, it's called the solar budget. It is important to note that the total amount of incoming radiation is equal to the total amount of outgoing radiation. Greenhouse gases (indicated by the 15%) are necessary to maintain the balance.

enter image source here

If you look at the 15% and imagine a great increase in the amount of those gases, eventually that 15% will become 16%. That means that 1% of the incoming radiation is not balance by outgoing radiation. This will result in a heating of the Earth so that the amount of heat released by the Earth will increase so that the amount absorbed by the greenhouse gases becomes 15% again. Now we are back in balance until the numbers change again.

For example, lets say the heat released by the Earth was 100 units, and to balance 15% (15 units) are absorbed by greenhouse gases. If 16 units are absorb then the heat of the Earth goes up. It isn't until the Earth is releasing around 106 units that the 16 units that greenhouse gases are absorbing becomes 15% and we have a balance again. Obviously for the Earth to be releasing 6 more units of heat the overall temperature of the Earth is going to have to go up.

No one disagrees with this at all. The point of debate regarding this is there are a lot of other numbers in that balance and each represents something else that impacts on the budget. Since there are so many other factors some argue that the greenhouse gas factor is somewhat less important.



They are one of the main driving forces behind evolution.


This question can be answered through the use of an example.

Consider a deciduous forest environment. This is a place similar to normal wooded areas found all over the United States. Normally, rabbits populate these areas quite heavily. Let the normal fur color of these rabbits be brown, however also consider that rabbits fur color is a very dynamic trait that can change.

Now imagine that there was an event that launched this area into winter-like conditions all year. The brown fur of rabbits in these types of conditions is not particularly good camouflage. But a genetic mutation occurs in one rabbit that gives it white fur.

That rabbit is much better suited to survive, and therefore is far more likely to reproduce and pass down this trait. The more times this occurs, the more widespread the beneficial trait occurs, and the less frequently the brown fur occurs.

Over time, nearly all of the rabbits in that area will have white fur because since the environmental climate changed, white fur became much more advantageous. In the initial climate, the mutation that led to white fur would quickly die out because white fur in that climate would be very visible, leading to the rabbit getting eaten. But in the new climate the rabbit with that mutation is able to flourish.

You may want to review the concepts of natural selection and adaptations for more information.



Increased temperatures affect the carbon cycle by lowering the amount of CO2 absorbed by oceans, melting permafrost which exposes the land underneath which then releases CO2 and CH4, and other


The carbon cycle describes how carbon moves and is transformed in the world. Global warming refers to increasing average global temperatures due to increases in greenhouse gases, such as carbon dioxide or CO2, in the atmosphere. Another important GHG is methane, CH4, is also increasing in the atmosphere.

Thus, the carbon cycle and global warming are intricately connected, as increasing carbon in the atmosphere means there is less carbon elsewhere in the cycle. Several feedback effects can be expected with higher temperatures:

  • Warmer oceans are less able to absorb CO2.
  • Higher temperatures also means melting permafrost, which will release carbon dioxide and methane into the atmosphere.

  • In areas with low precipitation, increased temperatures may increase the risk for forest fires, which would then release more carbon from the plant life into the atmosphere.
  • Increasing atmospheric CO2 concentrations is thought to have a direct effect on peat forests, causing the bogs to release more CO2 (see here).

Global warming will impact the carbon cycle in multiple ways, not all of which are fully understood.

See related Socratic content for more information:
How is carbon related to global warming?
How can the carbon cycle affect our planet?
How does carbon affect climate change?



Depending on the biome in question, the rates of certain steps of the cycle may change and reservoirs of water may change.


Depending on the biome in question, the rates at which certain steps of the water cycle (transpiration, precipitation, etc) may change. Where water is stored my also change.

Water cycle:

For example, in a rainforest biome, we wouldn't expect water to be stored in glaciers or ice. It's simply too hot for this. However, we would expect water to be stored in glaciers and/or ice in a montane biome.

The length of time the water is stored there may vary depending on conditions: in some habitats we may expect temperatures to climb high enough that any ice covering mountain tops melts during the warmer months, but this may not be true in other habitats.

In the biomes where there is little (or even no) vegetation, less water will be returned to the atmosphere via transpiration than in more heavily vegetated biomes.

Water cycle in the arctic:

The rate at which water percolates or infiltrates the soil may also change depending on the biome as will runoff rates, precipitation rates, the rate at which water is stored as groundwater, and evaporation. Different biomes receive different amount of precipitation, different amounts of sunlight, have different soil types and topography, and all of these variables will affect the water cycle and the rates certain processes occur.



The overall reaction that occurs within a hydrogen fuel cell is the same as that for combustion of hydrogen. This reaction is highly exothermic. Instead of producing heat, electric potential energy is generated.


A fuel cell is a type of electrochemical cell in which the reacting chemicals are continually added (one being oxygen), and products are removed (unlike a car battery or dry cell which is a closed system).

In the case of a hydrogen fuel cell, the process relies on a reaction that involves an equation identical to burning hydrogen

#2H_2 (g) + O_2 (g) rarr 2 H_2O (g#

This is an exothermic reaction (produces energy), in a fixed amount regardless of the process used to carry it out. The main difference is that the reaction is carried out in an electrochemical cell, with two half-reactions that take place at different locations within the cell.

At the cathode of the cell, hydrogen gas is supplied, and the process that occurs is the oxidation of the hydrogen into #H^+# ions:

#2H_2 (g) rarr 4 H^+ 4 e^-#

The hydrogen ions drift through the permeable anode material, the electrolyte (typically a solution of KOH) and arrive at the cathode. Here, they react with oxygen from the air in a reduction:

#O_2 (g) + 4H^+ + 4e^-##rarr 2 H_2O (g)#

This cell generates electrical energy with a cell potential of about 1.25 volts.

The combined "sum" of these two half-reactions (as they are known) yields an equation that is the same as the one that describes combustion of hydrogen gas.

Since the overall reaction is the same, the total energy produced is the same, but the efficiency of the cell (the portion of the energy that can be used to do useful work) is far greater than combustion provides.

You may want to check out this site:



They are structure used to change the Potential Energy of Water into Electric Energy.

[AEP’s Smith Mountain Hydro Project on the Roanoke River southeast of Roanoke, Virginia]

Have a look at the diagram:
enter image source here

In (A) you have a water reservoir (a lake of other water basin) where water is stored ready to be used. The water is secured by the actual dam (B) that is a kind of big wall that keeps the water from flowing down. The water in the reservoir has Potential Energy because it is at a higher level compared to, say, the valley below.

We use a pipe (C) to let the water flow down towards a structure (D) where is housed a big turbine connected to a dynamo.
The turbine (a kind of propeller) is moved by the water and acting on the dynamo produces electrical energy that, after transformation to high voltage, will be transmitted through a line (E).

The dynamo is normally called a Generator:
USGS Water Resources



Greenhouse gases contribute to the greenhouse effect.


The greenhouse effect is caused by increasing amounts of greenhouse gases (GHGs).

Since roughly the time of the industrial revolution, humans have been adding significant amounts of specific GHGs to the atmosphere.

These increases are anthropogenic in origin. Greenhouse gases include carbon dioxide, methane, ozone, water vapor, and others. Carbon dioxide and methane are the two GHGs of greatest concern. The former is emitted at very high rates and the latter persists in the atmosphere for a very long period of time. Burning of fossil fuels is a major source of increased GHG emissions.

To learn more, see this related question on Socratic describing how GHGs cause the greenhouse effect.



The atmosphere doesn't actually "stop" at a certain point, but gradually becomes thinner and thinner.


As you go up from the surface of the Earth, the weight of air above you generally becomes less and less. This reduced air pressure allows air molecules to be spaced apart more widely, making the air up high thinner than air at sea level.

(Temperature is another factor that affects the density of air. The molecules of hot air are more likely to be traveling at high speeds and will try to spread out more.)

The main layers of the Earth's atmosphere are (from the bottom up):

  • Troposphere
    (This is where you can breathe and where most visible weather happens.)
  • Stratosphere
    (The ozone layer in the lower part of it protects us from solar UV radiation.)
  • Mesosphere
    (The air up there is too thin for airplanes, but still too thick for satellites.)
  • Thermosphere
    (The ionosphere in the lower part of it is important for long-distance radio.)
  • Exosphere
    (The Earth's gravity is just barely hanging on to these molecules and ions.)

enter image source here

The usual definition for the "edge of space" is a height of 62 miles (100 km), near the bottom of the thermosphere. This distance is called the Karman line. This was the definition used by the Ansari X Prize , a competition to develop cheaper human spaceflight.

The top of the exosphere is defined as the height where ions of hydrogen (the lightest element) are more likely to get blown away into space by sunlight than to fall back to Earth. This happens around 6,200 miles (10,000 km) high. You could also say that the atmosphere ends here.

But the Earth actually does control what happens out farther than the exosphere. The magnetosphere is the area of space where the Earth's magnetic field is more powerful than the Sun's. It's not really a sphere, but squashed into a teardrop shape by the solar wind, high-energy particles streaming off the Sun. The magnetosphere is what keeps power stations from exploding and satellites from getting cooked every time the Sun tosses some stuff in our direction.

Check out this video from Crash Course Astronomy about the Earth and its atmosphere.
(Atmosphere part starts after 5min 43sec)
The Earth and its atmosphere .

More Crash Course Astronomy videos