Science fiction has conjured up countless pictures of what life could look like if humans could colonize space. But, is space colonization even possible? Not at the moment.

We currently know of no other inhabitable planets, and the technology that would be needed to make other worlds inhabitable does not yet exist. That said, the future may hold some interesting possibilities.

Why Would We Colonize Space?

Earth is naturally our ideal planet. Its thin atmosphere, which is strong enough to defend us from outside dangers without crushing us under its pressure, is comprised of the perfect mixture of gasses for us to breathe. Its temperature allows us liquid water and a bounty of food. Geographical catastrophes such as earthquakes and volcanic eruptions are infrequent enough for civilization to thrive.

But as our civilization progresses and our populations continue to grow, we may run out of room to expand on Earth. Space colonization could be a possible next step.

There could also be economic benefits to colonizing space. Countries could expand their territory without using up any more of Earth’s land. Space tourism already exists, and as technology improves, it could become more popular. We would have access to resources including the valuable metals contained inside of asteroids. New ways of harnessing solar energy and transmitting it back to Earth could be developed.

Why Would Colonizing Space Be Difficult?

Space is hard on the human body. Earth animals evolved to survive on Earth and Earth alone. Without Earth’s gravity, astronauts and other animals experience a variety of health complications.

Fluids can build up where they shouldn’t, muscles can atrophy, and bones can become weak. Organs drift and spines extend. Changes in pressure can cause vision problems. Harmful solar and cosmic radiation can be lethal without proper protection. Children raised in space would have all of these issues and likely could not visit Earth comfortably.

For humans to best survive in space, we would need a way to mimic the effects of Earth’s gravity. One idea is to build turning colonies that produce enough g-force to push inhabitants to the ground. This would not be real gravity but pseudo-gravity — the effect would not be unlike the feeling you get when you’re in a car taking a sharp turn and you get pushed against the door.

Another issue is resources. Earth is the only nearby planet with easy access to natural drinking water. Space colonists on Mars, for example, would have to excavate the planet’s frozen water supply, melt it down, and then somehow distil the results to make it drinkable. They would more or less be “roughing it.”

Of course, one key to getting colonists into space will be money for transportation. The cost to build and launch a spacecraft is tremendous, and government agencies such as NASA lack adequate funding. Private programs such as SpaceX are taking the reins in developing new ideas for human space travel.

What Options Do We Have?

Human beings could eventually live off of Earth. Where we would begin to do so is up in the air.

We could attempt to live on the moon or another rocky planet like Mars that is not too hot or too cold for us. A hypothetical process called terraforming, which involves changing the landscape of a cosmic body to suit our needs, is one conceivable way to do this. Living on a rocky surface would give us access to plenty of resource materials.

Another possibility is to simply live in orbit of Earth on large spacecraft. The International Space Station already houses astronauts for short spans of time. U.S. astronaut Scott Kelly is currently nearing the end of a record-breaking full year of life in space. No matter what, it’s important that the technology is durable and built with precision because it needs to withstand multiple journeys. In time, with improvements in technology, orbital colonies could provide a permanent home for human life.

While space colonization is currently impossible, the desire to make it possible someday is fueling research and development. As we learn more about space and the difficulties of living there, we may be slowly on our way to colonizing it.