Gravity is a very important force. It is the glue that holds together entire galaxies. It keeps planets in orbit. It makes it possible to use human-made satellites and to go to and return from the moon. It makes planets habitable by trapping gasses and liquids in an atmosphere. So how does gravity work in space? In this activity, you will take a more thorough look at gravity and temperature requirements in space.

As you learned in a previous activity, when there is no gravity for long periods of time, this leads to poor muscle strength and weak bones. Two solutions are being proposed to give the astronauts "artificial gravity."

The first is to rotate the part of the spaceship in which they live in a circle. The rotating will force the astronauts outward against the outside wall and will simulate gravity. This is similar to what happens when you tie a string on to a pail full of water and swing it around your head. The water is forced against the bottom of the pail and doesn't come out. This is called centripetal force. It is a force that acts on a body moving in a circular path and is directed toward the centre around which the body is moving.

A centrifuge is a machine that acts much like this spinning pail of water. The idea of spinning the entire living quarters of the spaceship is interesting, but another group of scientists have come up with a different solution. They propose using a small version of a human centrifuge. This will just spin a person instead of the whole ship. The person would lie with their feet against the "bottom" and as the centrifuge spins around, it simulates gravity on the person's body. They would have to do this a couple times each day to keep their muscles and bones strong. Below is a video of a large centrifuge. It works the same way as the miniature centrifuge.

Think about how you suit up when you go outside on a cold winter's day. You have your shirt, pants, sweater, perhaps long underwear, jacket, gloves, hat or hood, scarf, and boots. You put on quite a bit of clothing to protect you from the cold. Now, imagine what you would have to put on to protect you from outer space! Space suits must provide all of the comfort and support that the Earth or a spacecraft does, addressing issues like atmosphere, water, and protection from radiation.

Outer space is an extremely hostile place. If you were to step outside a spacecraft such as the International Space Station or onto a world with little or no atmosphere such as the moon or Mars and you were not wearing a space suit, the following things would happen:

You would become unconscious within 15 seconds because there is no oxygen.

Your blood and body fluids would "boil" and then freeze because there is little or no air pressure.

Your tissues (skin, heart, other internal organs) would expand because of the boiling fluids.

You would face extreme changes in temperature (sunlight: 248 degrees Fahrenheit/120 degrees Celsius and shade: -148 F/-100 C).

You would be exposed to various types of radiation, such as cosmic rays, and charged particles emitted from the sun (solar wind).

You could be hit by small particles of dust or rock that move at high speeds (micrometeoroids) or orbiting debris from satellites or spacecraft.

To cope with the extremes of temperature, most space suits are heavily insulated with layers of fabric (Neoprene, Gore-Tex, Dacron) and covered with reflective outer layers (Mylar or white fabric) to reflect sunlight. The astronaut produces heat from his or her body, especially when doing strenuous activities. If this heat is not removed, the sweat produced by the astronaut will fog up the helmet and cause the astronaut to become severely dehydrated. To remove this excess heat, space suits have used either fans/heat exchangers to blow cool air, as in the Mercury and Gemini programs, or water-cooled garments, which have been used from the Apollo program to the present.