Physics trivia

# vacuum

The ideal or perfect vacuum would be a region of space where there is total absence of matter. However, in practice, the perfect vacuum does not exist.

The ideal vacuum would be a region of space without any presence of matter , such as molecules , atoms , protons , neutrons or electrons . However, there is no region in the Universe that has a perfect vacuum, as there will always be atoms and other particles occupying space. Therefore, there is no empty space, that is, the vacuum is partial.

In the field of Applied Physics and Engineering , we usually call the regions of space occupied by a small amount of matter as a vacuum. Consequently, these regions have a pressure lower than the external atmospheric pressure .

## uses of vacuum

→ Vacuum can be produced by sucking in air from inside a container. This suction is done by a pneumatic pump. Typically, this technique is used to preserve food for a longer time.

→ Vacuum cleaners and pumps used to suck water from artesian wells, for example, produce imperfect vacuums. These machines are able to lower the local pressure, leading to the suction of surrounding matter.

→ Vacuum regions can also be used to study the movements of bodies without the influence of air friction. Thus, it is evident that, disregarding aerodynamic friction, bodies of different masses fall at equal intervals of time.

## Largest known vacuums

Some of the closest vacuums to the ideal vacuum are produced here on Earth. Several experimental apparatus used in laboratories for scientific research are capable of reaching pressures of up to 10 -10 Pa . For comparison, in the space occupied by a Rubik’s Cube, this pressure corresponds to the content of about 4 million atoms, approximately 100 particles per cubic centimeter .

Meanwhile, in intergalactic space, it is estimated that it is possible to find an average of three hydrogen atoms per cubic meter , which corresponds to pressures of up to 10 -15 Pa .

## absolute vacuum

Absolute vacuum is the name given to the condition of zero pressure, that is, of total inexistence of collisions between atoms or molecules against the borders of a system or against some body. However, for such a regime to be possible, it would be necessary for there not to be any particles in space and hence any energy level. Such a condition violates the quantum nature of particles, since the uncertainty principle indicates that it is impossible for any region of space to exist with an energy level exactly equal to zero.

In this way, energy levels, no matter how small, will never be equal to zero. Thus, phenomena called quantum fluctuations arise: spontaneous and ephemeral emergence of particles even in pressure regimes close to absolute vacuum.