It also slows down more as you move faster, which means astronauts (宇航員) someday may survive so long in space that they would return to an Earth of the distant future.

All these clothes are similar to the space Suit designs that kept astronauts comfortable in the temperatures of the moon, and are spin-offs from space technology.

In early space programs, such as the Apollo missions of the 1960s and 1970s, and in the Space Shuttle missions today, scientists developed objects for the astronauts to use on the moon and in space.

Much of it was left by American astronauts who landed on the lunar surface between 1969 and 1972 during NASA's Apollo missions.

The objects left by the Appllo astronauts included the equipment that was no longer needed.

Bacteria are an annoying problem for astronauts.

For instance, astronauts lose bone mass.

Nasa is worried about two things: recovery time once astronauts return home, and, more importantly, how to maintain strength and fitness for the two and a half years or more that it would take to make a round-trip to mars.

One of the nasa's major concerns about astronauts is how they can remain healthy for long in space.

Some astronauts feel sick on the station during the first few days because their brains receive contradictory messages.

The astronauts will suffer from a carbon-dioxide headache when they exercise in one place for a long time.

The exercise bike for the American astronauts has no handlebars.

The microorganisms from our bodies grow uncontrollably on surfaces of the international space station, so astronauts spend hours cleaning them up each week.

You can end up with what astronauts call a carbon-dioxide headache.