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Microgravity

The near-weightless condition inside an orbiting spacecraft, caused by continuous free fall rather than by the absence of gravity.

Why it matters

The common description - 'zero gravity' - is wrong in a way that matters: gravity in low Earth orbit is roughly 90 percent of its value at the surface. Things float because the spacecraft and everything in it are falling around the Earth together. The scientific value is that removing the effects of weight also removes convection and sedimentation, so fluids, flames, crystals and cells behave in ways impossible to reproduce on the ground - which is the entire justification for doing research in orbit rather than in a laboratory.

In our data

Microgravity research is one of the recurring subjects across our 688 published articles, and it is the reason the crewed and cargo flights in our tracker keep repeating: the experiments need continuous access, not a single trip.

Where we use it

Not to be confused with

Zero gravity, which does not exist anywhere near Earth, and weightlessness produced briefly on parabolic aircraft flights, which lasts seconds rather than months.