# Suction

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{{short description|Air pressure differential between two areas}}
{{other uses|suction (medicine)|suction convention}}

{{Multiple issues|
{{More citations needed|date=January 2024}}
{{Original research|date=December 2022}}
}}
thumb|240x240px|Gasses or liquids that move along a pressure gradient can exert forces on objects.
'''Suction''' is the day-to-day term for the movement of [gas](/source/gas)es or [liquid](/source/liquid)s along a [pressure](/source/pressure) gradient with the implication that the movement occurs because the lower pressure pulls the gas or liquid. However, the forces acting in this case do not originate from just the lower pressure side, but instead from the side of the higher pressure, as a reaction to the pressure difference.

When the pressure in one part of a [physical system](/source/physical_system) is reduced relative to another, the [fluid](/source/fluid) or gas in the higher pressure region will exert a [force](/source/force) relative to the region of lowered pressure, referred to as [pressure-gradient force](/source/pressure-gradient_force). If all gas or fluid is removed the result is a perfect [vacuum](/source/vacuum) in which the pressure is zero. Hence, no negative pressure forces can be generated. Accordingly, from a [physics](/source/physics) point of view, the objects are not  pulled but pushed.

== Examples ==
Pressure reduction may be [static](/source/Static_pressure), as in a [piston](/source/piston) and cylinder arrangement, or [dynamic](/source/Dynamic_pressure), as in the case of a [vacuum cleaner](/source/vacuum_cleaner) when [air flow](/source/Airflow) results in a reduced pressure region.

When animals [breathe](/source/breathing), the [diaphragm](/source/Thoracic_diaphragm) and [muscles](/source/Muscles_of_respiration) around the [rib cage](/source/rib_cage) cause a change of volume in the [lungs](/source/lungs). With increasing [volume](/source/volume) of the [chest cavity](/source/chest_cavity) the pressure decreases inside, creating an imbalance with the ambient air pressure, resulting in suction. Similarly, when a [straw](/source/drinking_straw) is used to suck a liquid from a glass into the mouth, the [atmospheric pressure](/source/atmospheric_pressure) on the fluid in the glass pushes the liquid up through the straw along the pressure gradient, creating a liquid column up to the height corresponding to the drop in pressure.

A common semantic mistake in [aviation](/source/aviation) accident reporting is describing people or objects as being 'sucked out' during [rapid decompression](/source/Uncontrolled_decompression) events, when physically they are 'blown out' by the higher internal cabin pressure rushing toward the lower ambient pressure outside the plane — the opposite phenomenon to what happens when an object is placed too close to a running [jet engine](/source/jet_engine) creating the risk of being sucked in.<ref>{{Cite web |last=Quora |title=There's No Suction In Space, Because Suction Is An Illusion |url=https://www.forbes.com/sites/quora/2016/11/21/theres-no-suction-in-space-because-suction-is-an-illusion/ |access-date=2024-01-14 |website=Forbes |language=en}}</ref><ref>{{Cite web |title=Why doesn't Earth's atmosphere escape into space? |url=https://www.spacecentre.nz/resources/faq/solar-system/earth/atmosphere-escape.html |access-date=2024-01-14 |website=www.spacecentre.nz}}</ref><ref>{{Cite web |title=NTSB Schedules Investigative Hearing on Boeing 737-9 MAX Door Plug Blowout |url=https://www.ntsb.gov/news/press-releases/Pages/NR20240312.aspx |access-date=2025-03-19 |website=www.ntsb.gov}}</ref>

== See also ==
{{Wiktionary}}
*[Pump](/source/Pump)
*[Vacuum pump](/source/Vacuum_pump)
*[Suction devices used in medicine](/source/Suction_(medicine))
*[Implosion](/source/Implosion_(mechanical_process))
* [Suction cup](/source/Suction_cup)
* [Suction cupping](/source/Suction_cupping)

== References ==
{{reflist}}

Category:Physical phenomena
Category:Vacuum

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Adapted from the Wikipedia article [Suction](https://en.wikipedia.org/wiki/Suction) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Suction?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.