Question: why is it important for the astronauts to keep their back's safe? Why has it got to do with space and gravity?

Kirsty Lindsay answered on 12 Jun 2016:

What a great question Sangeeta!

On Earth our bodies work against gravity all the time- and our bodies are designed for that. If you think about what a jellyfish in the sea looks like compared to what a person looks like you can see we are built to work in very different environments.

In space there is gravity- on the ISS its almost as strong as on the ground, but the spacecraft (and everything in it, including the crew) are moving very very fast around the Earth at the same speed as gravity is trying to pull it down- the over all result is zero force on the astronaut- which we call microgravity.

Ok- so now we know why the crew floats around we see that their bodies don’t have to work very hard at all- they get to relax all they time! On Earth working against gravity helps to keep our muscles and bones strong, because they constantly have to work, but in space muscles and bones hardly have to work at all.

Keeping our backs safe is space means that we are less likely to injure them when we return to Earth and means astronauts have a nice strong base to do everything else. Our backs are the main bit of our skeleton that keeps us upright, and our arms and legs use it as a base to move from- with a weak and floppy spine even reaching or a cup of tea can be hard work!