The ionosphere gets its name from the solar radiation that ionizes gas molecules to create a positively charged ion and one or more negatively charged electrons. The freed electrons travel within the ionosphere as electric currents. Because of the free ions, the ionosphere has many interesting characteristics. At night, radio waves bounce off the ionosphere and back to Earth. This is why you can often pick up an AM radio station far from its source at night.
The Van Allen radiation belts are two doughnut-shaped zones of highly charged particles that are located beyond the atmosphere in the magnetosphere. The particles originate in solar flares and fly to Earth on the solar wind.
These lines extend from above the equator to the North Pole and also to the South Pole then return to the equator. When massive solar storms cause the Van Allen belts to become overloaded with particles, the result is the most spectacular feature of the ionosphere—the nighttime aurora.
The particles spiral along magnetic field lines toward the poles. The charged particles energize oxygen and nitrogen gas molecules, causing them to light up. Each gas emits a particular color of light. There is no real outer limit to the exosphere , the outermost layer of the atmosphere; the gas molecules finally become so scarce that at some point there are no more. Beyond the atmosphere is the solar wind.
The solar wind is made of high-speed particles, mostly protons and electrons, traveling rapidly outward from the Sun. Skip to main content. The Atmosphere. Search for:. When gas molecules are cool, they are sluggish and do not take up as much space. With the same number of molecules in less space, both air density and air pressure are higher.
When gas molecules are warm, they move vigorously and take up more space. This corresponds to air at about 13 kilometers altitude. If the size of our container were decreased to 1 meter on all sides, as in Case 3, and we kept the same number of molecules, that density would increase to.
Notice that we have the same amount of material; it is just contained in a smaller volume. How we decrease the volume is very important for the final value of pressure and temperature. You can explore the variations in pressure and temperature at the animated gas lab.
Actual molecules of a gas are incredibly small. In one cubic meter the number of molecules is about ten to the 23rd power.
That's 1 followed by 23 zero's!!! For a static gas, the molecules are in a completely random motion. Because there are so many molecules, and the motion of each molecule is random, the value of the density is the same throughout the container.
As an example, consider Case 1, in which the mass is. Then, think about the space around each bowling ball, and imagine that the space is filled with air.
That pool is not very dense, because there are lots of air pockets. Now, imagine that you fill the spaces in between each bowling ball with clay baseballs. Your swimming pool just got a bit denser, with fewer spaces for air. Now, if you fill in the remaining spaces with silt marbles there should be very few spaces left that are filled with air. This last kind of soil is the most dense. Figure D. Density of compacted vs. Soil that is very dense and has few air pockets has become this way through compaction.
Compaction makes it harder for water and air to penetrate the soil around the roots of your crop, which makes it hard for the plants to grow. Compacted soil results in less root growth, because it creates a barrier that makes it difficult for roots to have access to oxygen, water, and nutrients from the soil.
On the other hand, compacted soil is a good thing when it comes to things like building roads or buildings. Princeton U. How can the air become lighter if we add water vapor to it? Scientists have known this for a long time. The first was Isaac Newton, who stated that humid air is less dense than dry air in in his book, Optics.
To see why humid air is less dense than dry air, we need to turn to one of the laws of nature the Italian physicist Amadeo Avogadro discovered in the early s. In simple terms, he found that a fixed volume of gas, say one cubic meter, at the same temperature and pressure, would always have the same number of molecules no matter what gas is in the container.
Most beginning chemistry books explain how this works. Imagine a cubic foot of perfectly dry air. Molecules are free to move in and out of our cubic foot of air. What Avogadro discovered leads us to conclude that if we added water vapor molecules to our cubic foot of air, some of the nitrogen and oxygen molecules would leave — remember, the total number of molecules in our cubic foot of air stays the same. The water molecules, which replace nitrogen or oxygen, have a molecular weight of One oxygen atom with atomic weight of 16, and two hudrogen atoms each with atomic weight of 1.
This is lighter than both nitrogen and oxygen. Related: Understanding water in the atmosphere. But, humid air is lighter than dry air at the same temperature and pressure. Baseball players have found that home runs travel farther in the less dense air in high-altitude Denver than in ball parks at lower elevations.
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