The effects of space on our body.

I have always been fascinated with space, but not in the physicist kind of way, more in the muggle stuck on earth kinda of way. It seems pretty magical to me that astronauts have made it to space. I myself would never aspire to BE said astronaut but I do want to know more about it. My main interest lies in biology, so I thought I would focus on how the body is affected by space. 

Space is a completely different environment to earth, where our bodies have evolved and adapted to for centuries. The main change in space is the change in gravity. While on the International Space Station (ISS) you are weightless, but while on a planet (say Mars) the gravity is about 1/5 of that on Earth’s. The reduced gravity will effect our bodies in a number of ways, having a significant toll on an astronaut’s body. 

The first main change is bone density and muscle degradation. Your muscles will begin to waste away because you will not need to move around as often, this can be due to the fact astronauts float around to move or that they are confined to the ISS, a small area. When astronauts get back to earth, they have to be rehabilitated to rebuild their muscle strength up. This is similar to when someone breaks a leg and gets a cast. When they get the cast off after numerous weeks, that leg is usually significantly skinnier than the other one because they haven’t been exercising the leg as much. To help alleviate that, astronauts exercise 2 hours a day whilst in space, usually on a treadmill. The effect of exercise decreases in space so the amount that needs to be done increases. The equipment needs to be working correctly and specially designed because astronauts are usually travelling a large distance from Earth. They can’t just turn around to pick up a missing part. Equipment (medical equipment too) and medications must be functioning properly and in reasonable supply. This makes it all the more complicated to plan a trip to space.

Photo Credit: NASA

Bone density changes a significant amount too. Density drops about 1% each month they are in space. Compared to the 1-1.5% drop in elderly people a year, that is a tremendous amount. This can be dangerous and could lead to osteoporosis, a disease where bones become brittle. This can not always be corrected with rehabilitation when astronauts get back to Earth. For this reason exercise and eating properly in space is extremely important.

Bone Density Changes (left = normal bone, right = osteoporosis). Photo Credit: Space Station Explorers

A physical change that I didn’t expect was vision changes. Gravity on Earth is apparent when someone stands up for too long and begins to feel faint because their is less blood near the brain. In this way, gravity pushes down, sending liquid (blood) towards your feet instead of towards the brain where a rich blood supply is needed. The opposite happens in space. The microgravity causes cerebrospinal fluid to move to your head. Cerebrospinal fluid is a fluid around the brain which helps regulate pressure changes around the brain. Whilst in space, the complicated system is disrupted by microgravity. As a result, astronauts heads will swell up, making it appear like they have gained weight. This puts pressure on the eyes and can cause blurred vision. The medical name is visual impairment intracranial pressure. You can imagine that an astronaut needs to be able to see clearly because they are completing complicated tasks on a daily basis.

Here is a magnetic resonance imaging of an astronauts eyeball before and after a space flight. Above: before flight. Below: during flight – you can see that the eyeball has flattened due to pressure from brain fluid.
Photo Credit: National Geographic article (RSNA took the photo)

For a similar reason, your heart size can decrease whilst in space. This is because the heart doesn’t need to pump blood against the force of gravity so it exerts less power to circulate the blood. After returning to Earth, the heart will begin to readapt to the gravity increase again. However, in the long term this can increase the risk of cardiovascular disease.

A less dangerous side effect of space is that an astronaut will get taller. On Earth, gravity pushes down on our spine, causing compression which makes you appear shorter. Making someone taller isn’t an important change, more of a fun fact!

Gravity isn’t the only change in space, the body also experiences more radiation on the ISS. The Earth’s magnetic field and atmosphere protects us from the harsh cosmic radiation. The radiation in space is 10 times that on earth. Excess radiation can cause mutations in DNA replication, resulting in uncontrolled cell division. In the long term, a tumour may form as cancer. However, the ISS has artificial shielding that can partially protect someone from the radiation increase.

The Types of Space Radiation. Photo Credit: ResearchGate

Clearly, astronauts have to consider a myriad of risks before they embark on a trip to the moon. But there are ways to reduce risks and damage to the body. ‘Rocket scientists’ have to think about a lot more than just building the rocket.

Photo Credit: Time Knowledge

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