“Everyone feels and experiences gravity in the same way, independently of who or what you are and look like. You can be a speck of dust, a bacterium, or an elephant, and you will still feel the gravitational pull from Earth.”

- Claudia de Rham, theoretical physicist, author of The Beauty of Falling - A Life in Pursuit of Gravity.

Gravity is difficult to pin down. 

It’s the mesh that holds our universe together. And you could say it’s one of the weakest physical forces out there, yet we feel its strong, inevitable downwards pull every day. But what even is “downwards”? This direction, that we never spend much thought on because we know it intuitively, really is defined by gravity. “Down” would feel very different on the surface of Mars or the Moon. And what if we are floating in between, somewhere out in space? …that’s right: Suddenly “down” isn’t nearly as straightforward as we thought.

Space changes the rules we spent our lives learning to play by. 

Astronauts who dare to leave the surface of the Earth are entering a whole new environment that is hostile to life as we know it. Space physiology is the area of research that investigates how the human body is affected and adapts to this new environment. It focuses on three main stressors:

• radiation - astronauts are no longer protected by the Earth’s magnetic field, 

• isolation and confinement - on long and faraway missions,

• and, what we just discussed, the absence of “down”. Or: microgravity - where you are in space, far enough away from a massive object so you are in constant free fall towards that object. (Picture the ISS orbiting Earth.)

Let’s take a closer look at microgravity. 

Even in outer space, there is no such thing as a perfect state of zero gravity. The gravitational influence of distant matter never switches off; it just becomes smaller and smaller. And when you orbit a planet, like the ISS orbits Earth, it is still subject to about 90% of Earth's gravitational pull. But you, the ISS, and everything inside it is in constant free fall towards the surface of the Earth, creating the feeling of weightlessness in an environment we call microgravity. 

But we spend our lives learning to live in the specific gravitational pull we experience on Earth's surface, that is defined as 1g. A surprising amount of bodily functions have evolved with this constant force around us; which is why we get awfully thrown off when it disappears.

There is an organ whose function depends on the presence of gravity.

The vestibular system hides behind our ears and is responsible for sensations of balance, orientation and proprioception (where our body is moving, relative to the space around us). So, technically it’s not an organ of itself, more of a system that integrates crucial information from other organs. Its crafty shape of fluid-filled loops in every axis (semicircular canals) and a base containing calcium carbonate crystals (otolith organs) can detect all sorts of movement our head does, and integrates it with input from our eyes and muscles, which keeps our brain informed about our body’s orientation and movement. But only in 1g gravity do the crystals behave in a way that we learned is normal. In microgravity, there is no “down” the crystals are being pulled towards, and the resulting signal generated by the vestibular system and sent to the brain is… a mess.

Astronauts get space motion sickness because this messy signal is paired with conflicting input from their eyes, which usually helps the brain with clues about how the body is oriented or moving about. As you can imagine, any astronaut who is just reaching the microgravity environment has other concerns than figuring out where up and down is or dealing with the unpleasant effects of motion sickness. 

Therefore, it is crucial to ask questions such as what happens to our vestibular system in microgravity to improve astronaut wellbeing and mission success. Understanding the physiological changes in this fundamentally different environment doesn’t only help us protect astronauts and improve their mission performance, it also provides a new perspective on human physiology that would not be (entirely) replicable on earth and can inform medical research for everyday terrestrial questions of physiology and medicine. 

COMPASSpace is here to ask these questions. 

We’re coming into the picture where basic research on the ground can’t provide satisfying answers to human physiology in outer space anymore. To a degree, the effects of microgravity on the human body can be mimicked with so-called ground-based analogs. Those are techniques like head-down bed rest that affect fluid shifts similarly to microgravity. But there are limitations to these techniques and the only plausible next step is to test our hypotheses in real microgravity. 

Specialized airplaines can recreate microgravity in parabolic flights for up to 22 seconds at a time. This provides a platform where we can conduct research studies in microgravity without having to fly to space. 

This is just the beginning of our journey. Over the coming year, the COMPASSpace team will refine the research question and experiments to work towards applying for the support needed to make it all happen. If all goes to plan, we'll take the next step: testing our ideas in real microgravity aboard a parabolic flight. 

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We will soon have a closer look at parabolic flights, the vestibular system in space, astronauts' cognitive demands... and what COMPASSpace actually stands for!

Come along to explore the brain in space with us!