Twelve people are going to lie in bed for an entire month in the name of science, part of NASA’s research into how space travel affects the health of astronauts.

The space agency’s Johnson Space Center announced this week that the dozen guinea pigs are spending 30 days just lying in bed with their heads tilted back six degrees so that scientists can study what happens to their bodies during that time. The position in which the volunteers will be suspended, in addition to breathing air with a higher carbon dioxide content, should produce changes in the body that are similar to when someone is in space.

NASA says that applies on a physical level as well as an emotional one.

“These studies are expected to help advance the understanding of how to keep humans safe as we move from lower-Earth orbit missions into deep space exploration,” the space agency explained.

The research is taking place at a facility of the German Center for Air and Space Travel’s Institute of Aerospace Medicine. The German space agency, known by the initials DLR, has partnered with NASA’s Human Research Program on the effort “to observe and analyze the effects of fluid pressure on astronauts’ eyes and optic nerves,” NASA said. “Blood pressure, heart rate, nutrient absorption, energy expenditure, bone mass and even the participants’ mood will also be monitored.”

When the head is tilted backward, bodily fluids shift in that direction just like they do in the weightless space environment. This has been linked to vision problems for some astronauts and could have the same effect on the study volunteers.

There is another component to the experiment: Normal air we breathe on Earth is about 0.04 percent carbon dioxide, but these supine subjects will be breathing 0.5 percent carbon dioxide — more than 12 times what they are used to. But the American agency explains that in enclosed vehicles like the International Space Station, there is more carbon dioxide in the air. It is still safe to inhale, however.

The Earth study subjects will be on a limited diet as well.

The scientists are currently collecting several days’ worth of baseline health data from the study subjects before they spend 30 days lying down.

“Participants must live, eat, and even shower in the head-down position — and in this case in the carbon dioxide environment,” NASA said. “This causes their bodies to adapt as if they were in space.”

Experts will be keeping an eye on the changes with a goal of using the information to improve the health and experiences of astronauts who are traveling in space.

There could also be applications for people on Earth who are bedridden, according to the space agency.

“While very structured, the participants’ days may not be as boring as it would seem,” NASA explained. “Participants are encouraged to set a goal such as learning a new language or taking a class online.”

The subjects are allowed to use phones and computers during the study period as long as they remain in their tilted position.

german-space-agency Volunteers are going to lie down in bed for an entire month for an experiment at the Institute of Aerospace Medicine’s facility in Cologne, Germany, part of that country’s space agency. Photo: NASA