I wondered if you could float into space on a balloon. After a quick search on Google I found an answer that left me with more questions. This is what it said:"Could a helium balloon float all the way up into space? A helium filled balloon can float very high up into the atmosphere, however, it cannot float up into outer space. The air in Earth's atmosphere gets thinner the higher up you go. The balloon can only rise up until the atmosphere surrounding it has the same weight as the helium in the balloon. This happens at about a height of 20 miles (32 kilometers) above Earth's surface. So, this is as far as a helium balloon can rise. Outer space starts somewhere around 600 miles (960 kilometers) above Earth's surface." The density of the atmosphere changes but the density of the molecules of air stay the same. The Helium molecules are less dense so when the balloon gets high in the atmosphere why cant it just release air to keep it's density less than the surrounding air? Then I found another site saying something else "They are amateur scientists and radio operators, and they use weather balloons to send radios, cameras, and scientific experiments high into the stratosphere. The balloons can reach altitudes over 100,000 feet before bursting to shreds and parachuting back to Earth with their payloads. At that altitude, atmospheric pressure is a mere 1 percent of what it is at sea level and the radiation many times greater. Temperatures can reach -90 degrees F. " The only thing that limits these flights is the balloon. If a pressure check valve were put on the balloon so ,rather than explode at 100,000 feet ,it just releases helium to maintain pressure at a safe level could it go higher? I realize that a balloon could not float into space because once it is in the vaccuum of space it will be denser than it's surroundings. But it should be able to float on top of the atmosphere like a ball floats on the water. My Idea is to put a model rocket on a platform. The platform has four or more helium balloons with enough volume to float. Each balloon has a pressure check valve that maintains the balloon's pressure at 5 or more psi. Once the platform foats up to the edge of space a small model rocket can easily launch into space. Perhaps the expiriment could be done on a larger scale.