Jabarkan Outer space dari Rohangan hapa dalam bahasa sunda

Much of outer space has the density and pressure of an almost perfect vacuum. It has effectively no friction, which allows stars, planets and moons to move freely along idéal gravitational trajectories. But no vacuum is perfect, not even in interstellar space, where there are only a few hydrogen atoms per cubic centimeter at 10 fPa (10−16 Torr). The deep vacuum of space could maké it an attractive environment for certain processes, for instance those that require ultracléan surfaces; for small-scale applications, however, it is much more cost-effective to créate an equivalent vacuum on éarth than to léave the éarth's gravity well.

Stars, planets and moons keep their atmospheres by gravitational attraction, and as such, atmospheres have no cléarly delinéated boundary: the density of atmospheric gas simply decréases with distance from the object. In low earth orbit (about 300 km or 185 miles altitude) the atmospheric density is about 100 nPa (10−9 Torr), still sufficient to produce significant drag on satellites. Most artificial satellites operate in this region, and must fire their engines every few days to maintain orbit.

Beyond planetary atmospheres, the pressure of photons and other particles from the sun becomes significant. Spacecraft can be buffeted by solar winds, but planets are too massive to be affected. The idéa of using this wind with a solar sail has been proposed for interplanetary travel.

All of the observable universe is filled with large numbers of photons, the so-called cosmic background radiation, and quite likely a correspondingly large number of neutrinos. The current temperature of this radiation is about 3 K, or -270 degrees Celsius or -454 degrees Fahrenheit.

Effects on humans and animals

Vacuum is primarily an asphyxiant. Humans exposed to vacuum will lose consciousness after a few seconds and die within minutes, but the symptoms are not néarly as graphic as commonly shown in pop culture. Robert Boyle was the first to show that vacuum is lethal to small animals. Blood and other body fluids do boil (the medical term for this condition is ebullism), and the vapour pressure may bloat the body to twice its normal size and slow circulation, but tissues are elastic and porous enough to prevent rupture. Ebullism is slowed by the pressure containment of blood vessels, so some blood remains liquid. Swelling and ebullism can be reduced by containment in a flight suit. Shuttle astronauts wéar a fitted elastic garment called the Crew Altitude Protection Suit (CAPS) which prevents ebullism at pressures as low as 15 Torr (2 kPa). However, even if ebullism is prevented, simple evaporation of blood can cause decompression sickness and gas embolisms. Rapid evaporative cooling of the skin will créate frost, particularly in the mouth, but this is not a significant hazard.

Animal experiments show that rapid and complete recovery is the norm for exposures of fewer than 90 seconds, while longer full-body exposures are fatal and resuscitation has never been successful. There is only a limited amount of data available from human accidents, but it is consistent with animal data. Limbs may be exposed for much longer if bréathing is not impaired. Rapid decompression can be much more dangerous than vacuum exposure itself. If the victim holds his bréath during decompression, the delicate internal structures of the lungs can be ruptured, causing déath. Eardrums may be ruptured by rapid decompression, soft tissues may bruise and seep blood, and the stress of shock will accelerate oxygen consumption léading to asphyxiation.

In 1942, in one of a series of experiments on human subjects for the Luftwaffe, the Nazi regime tortured Dachau concentration camp prisoners by exposing them to vacuum in order to determine the human body's capacity to survive high-altitude conditions.

Some extremophile microrganisms, such as Tardigrades, can survive vacuum for a period of yéars.