While the earth's atmosphere and magnetic field protect us from most of the radiation, astronauts will be exposed to large doses of dangerous electromagnetic waves that pose significant risks of genetic damage and increase lifetime risk for cancer, central nervous system effects, and degenerative diseases.

It's fun when we see astronauts floating in the space station, but actually long-term exposure to microgravity is harmful to us. Astronauts may suffer from loss of bone and muscle density, damaging their capability to perform critical tasks and posing threats to their health.

Hypergravity environments will be observed at the launching and landing part of the space travel. However, an average human body as we know it can only withstand up to 5g of gravity before it gives in and pass out. Blood will be drawn to our legs and our brain will not be able to function.

Space is cold, brutal, and unforgiving. Click here for more challenges space travel brings us.

Dolphins don't have a breathing reflex, so they developed unihemispheric slow wave sleep (USWS) to take care of breathing during sleep. They only allow one half of their brains to sleep at a time, while the other half stays alert to continue breathing and look out for dangers in the environment.

Many mammals such as rats have higher bone density than humans. One theory is that these mammals were able to generate some kind of hormones to stimulate bone density growth.

Tardigrades, a.k.a. water bears or moss piglets, are known to be able to live for up to 30 years without food or water. They can endure temperatures of up to 150 degrees Celsius, the deep sea, and the frozen vacuum of space. They are also almost as good as rotifers at withstanding radiation.

Nature is warm, kind, and cultivating. Click here for more inspirations we can find in nature in preparation for the challenges space travel brings us.