Space travel is an incredible adventure, but it comes with bizarre and unexpected side effects that astronauts rarely talk about. From swollen heads to space brain syndrome, discover the strangest ways space affects the human body.
Space travel has always fascinated humanity, but while astronauts get to experience weightlessness, breathtaking views of Earth, and the thrill of the unknown, there are also some unexpected physical and psychological challenges that few people know about. The human body is not designed for life beyond our planet, and spending time in microgravity can have surprising and sometimes downright strange effects. From mysterious changes in eyesight to space-induced hallucinations, let’s explore the strangest side effects of traveling to space that astronauts rarely discuss.
The “Puffy Head, Bird Legs” Effect
One of the first things astronauts notice when they enter microgravity is that their faces swell up while their legs become noticeably thinner. This odd transformation, known as the “Puffy Head, Bird Legs” effect, happens because gravity no longer pulls bodily fluids downward, causing them to shift upward instead. With excess fluid pooling in the upper body, astronauts often experience stuffy noses, swollen faces, and increased pressure in their heads. This condition usually improves as the body gradually adapts, but many astronauts report that their faces never fully return to normal until they are back on Earth.
Spaceflight Alters the Shape of the Brain
In 2017, a study published in the journal New England Journal of Medicine revealed that spending time in space actually changes the structure of the human brain. Scientists scanned the brains of 34 astronauts before and after their missions and found that extended space travel leads to the upward shifting of the brain inside the skull. This shift is believed to be caused by fluid buildup due to microgravity. Some astronauts have even reported difficulties concentrating and memory problems after returning from space, leading researchers to further investigate the long-term cognitive effects of space travel.
Astronauts Can’t Smell or Taste Food Properly
If you ever dreamed of eating gourmet food in space, you might be disappointed to learn that astronauts often lose their ability to fully taste and smell. Due to the fluid shifts in their bodies, their nasal passages become congested, similar to having a cold on Earth. As a result, their sense of taste is dulled, making food seem bland and unappetizing. To counter this, astronauts often crave strong, spicy, or highly seasoned foods like hot sauce and wasabi. NASA even supplies extra condiments to keep meals interesting.
The Mysterious “Space Fog” and Cognitive Decline
Many astronauts report experiencing a mental sluggishness referred to as "space fog." This condition includes difficulty concentrating, slower reaction times, and temporary memory lapses. Scientists believe space fog is caused by a combination of microgravity’s effects on brain fluid distribution and increased exposure to cosmic radiation. A 2021 study from NASA suggested that long-term exposure to space radiation might lead to cognitive impairments that could persist even after astronauts return to Earth. This is a major concern for future deep-space missions, such as those to Mars, where astronauts will be exposed to radiation for extended periods.
Vision Problems That Linger for Years
One of the more serious and still poorly understood effects of space travel is its impact on vision. Many astronauts who have spent months aboard the International Space Station (ISS) report changes in their eyesight, with some experiencing permanent vision impairment. This condition, known as Spaceflight-Associated Neuro-ocular Syndrome (SANS), is thought to be caused by fluid pressure on the optic nerve and the reshaping of the eyeball due to microgravity. Studies show that up to 60% of astronauts who spend extended time in space experience some form of vision change, raising concerns about how deep-space exploration could impact long-term eye health.
The Phenomenon of “Phantom Limb” Sensations
Without gravity acting on their bodies, astronauts often struggle to perceive their limbs correctly in space. Some report experiencing "phantom limb" sensations, where they feel as though their arms or legs are floating in a different position than they actually are. This happens because the body’s proprioception—its ability to sense movement and body position—is thrown off in microgravity. Many astronauts train extensively to adapt to this sensation, but it remains one of the more peculiar and disorienting aspects of space travel.
Radiation Exposure Alters DNA
Unlike Earth, which has a protective atmosphere and magnetic field to shield us from cosmic rays, space exposes astronauts to high levels of radiation. Studies have shown that prolonged exposure to space radiation can alter DNA, increasing the risk of cancer and accelerating cellular aging. In fact, a study of astronaut Scott Kelly, who spent nearly a year in space, found that his telomeres—structures at the ends of chromosomes—became longer during spaceflight but rapidly shortened once he returned to Earth. This suggests that space travel could have significant effects on the aging process at a cellular level.
Space-Induced Hallucinations and Hearing “Outer Space” Sounds
Although space is a vacuum and should be completely silent, astronauts have reported hearing unexplained noises while aboard spacecraft. Some describe hearing mechanical knocking, distant buzzing, or even whispering sounds, despite there being no external sources. Scientists believe these noises could be due to pressure changes in the spacecraft or internal auditory illusions caused by microgravity. In addition, some astronauts report experiencing visual hallucinations, such as flashes of light or streaks of color, which may be caused by cosmic radiation interacting with the optic nerve.