Stephanie Slaunwhite (grade 4) - Tallahassee Community School, NS

The earth's atmosphere is essential to life. The atmosphere surrounds earth and protects it from the hazards of space. It insulates the inhabitants of earth from the extreme temperatures of space and stops all but the largest meteoroids from reaching the surface. Furthermore, it filters out most radiation dangerous to life.

Without the atmosphere, life would not be possible on earth. The atmosphere contains the oxygen we breathe. It maintains a level of pressure on our bodies and all other entities on earth too, for example, it ensures that water—the dominant element for life on earth—remains liquid at moderate temperatures.

The space environment is radically different from the earth. As you move further into space and away from the earth, fewer and fewer atoms and particles are present. There are no oxygen molecules, ergo, no air to breathe. There is no water. Solar radiation reaches spacecraft unfiltered (other than the protection provided by the craft). Bodies in space are exposed to extreme cold and extreme heat, and to radical changes in temperature. The pressurized environment of earth is not replicated in space. In fact, space is a vacuum; without the pressurized environment created inside a spacecraft, the human body could not survive.

Justin (grade 5/6) - St. Joseph’s School, ON

It is interesting to note that in microgravity the change in location of fluids, which make up the greatest part of the human body, are responsible for many of the sensations experienced in the weightless environment. On earth, blood is pumped out by the heart and sent, with help of gravity to the extremities of the body, like the legs. In microgravity, blood and other fluids tend to pool above the upper torso (chest area) and in the sinuses. The legs become skinnier and the head expands to accommodate all of this new fluid. As a result, astronauts often have headaches due to sinus pain and inflammation. They even have difficulty identifying the taste of foods.

	Sara C, through epals
	Jay Berreth (grade 3) - Sidney Street School, SK

From the moment an astronaut leaves the earth's atmosphere, whether they are inside the shuttle, the Space Station or outside the spacecraft conducting a spacewalk, he or she is weightless.

Patrick Bungay (grade 4) - Tallahassee Community School, NS

About 30-40 percent of all individuals experience "space adaptation syndrome" (which is a kind of motion sickness) upon first entering a low-gravity or microgravity condition, for 2-3 days. Others have no problems.

Kakisa Lake School, NWT

A large part of the answer to this question is based on how long you have been in space. Life on earth is highly evolved and takes advantage of its environment, including gravity. On a typical space shuttle mission of one or two weeks your body goes through quite a few changes.

Among the changes in your body is a loss of certain minerals such as calcium from the bones, in part because they no longer carry weight when you orbit the earth. This process is similar to a disease called osteoporosis experienced by many older individuals. When astronauts return to earth, they slowly regain their bone mass.

When you travel to space you also tend to unload fluids, in part because fluids, now weightless, accumulate in your hands, feet and face. When your muscles do not have to fight gravity they tend to lose nitrogen and they atrophy. Some people who return to earth after having been in space for an extended period of time will have trouble standing right away because of the changes in their blood volume. They might have trouble walking because their muscles have atrophied after a longer stay in space. Also, their sense of equilibrium needs some time to readjust to gravity’s up/down direction. These changes do not affect everyone equally.