page_title: Weightlessness
section_title: Technical adaptation in zero gravity
hierarchical_section_title: Weightlessness / Technical adaptation in zero gravity
caption_attribution_description: English: A comparison between a flame on Earth and a flame in a microgravity environment. This occurs because the flame on Earth is hot and since heat rises it makes that nice slender shape but since there isn't gravity in the second picture it just expands in a sphere. Українська: Порівняння полум'я свічки на Землі (зліва) та полум'я у середовищі мікрогравітації. На Землі на нього діє тяжіння планети, полум'я підіймається, видовжується; оскільки друге зображення зроблене в умовах майже відсутньої гравітації, полум'я просто поширюється в усі сторони, формуючи сферу.
context_page_description: Weightlessness is the complete or near-complete absence of the sensation of weight. This is also termed zero-G, although the more correct term is "zero G-force". It occurs in the absence of any contact forces upon objects including the human body.
  Weight is a measurement of the force on an object at rest in a relatively strong gravitational field. These weight-sensations originate from contact with supporting floors, seats, beds, scales, and the like. A sensation of weight is also produced, even when the gravitational field is zero, when contact forces act upon and overcome a body's inertia by mechanical, non-gravitational forces- such as in a centrifuge, a rotating space station, or within an accelerating vehicle.
  When the gravitational field is non-uniform, a body in free fall experiences tidal effects and is not stress-free. Near a black hole, such tidal effects can be very strong. In the case of the Earth, the effects are minor, especially on objects of relatively small dimensions and the overall sensation of weightlessness in these cases is preserved. This condition is known as microgravity, and it prevails in orbiting spacecraft.
context_section_description: Weightlessness can cause serious problems on technical instruments, especially those consisting of many mobile parts. Physical processes that depend on the weight of a body (like convection, cooking water or burning candles) act differently in free-fall. Cohesion and advection play a bigger role in space. Everyday work like washing or going to the bathroom are not possible without adaptation. To use toilets in space, like the one on the International Space Station, astronauts have to fasten themselves to the seat. A fan creates suction so that the waste is pushed away. Drinking is aided with a straw or from tubes.
caption: Candle flame in orbital conditions (right) versus on Earth (left)
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