Vacuum often thought of  as empty space, but even what appears to be empty space is filled with activity at the quantum level. This activity consists of pairs of virtual particles and antiparticles that spontaneously appear together and annihilating each other, a phenomenon tied to Hawking radiation, named after the physicist Stephen Hawking.

Can information get lost?

A black hole is a region in space time with such an immense curvature that within its event horizon, the gravitational pull is so strong that nothing- not even light- can escape.  

However, Hawking identified a paradox: if nothing can escape a black hole after crossing the event horizon, then any information that falls into it would be permanently lost (for instance throwing a book inside). This contradicts the laws of physics, which state that information cannot be destroyed.

Hawking radiation

Hawking proposed a groundbreaking solution: the activity of empty space itself. According to quantum field theory, virtual particle-antiparticle pairs continuously form and annihilate, borrowing energy from the vacuum. 

Near a black hole, if ounce of these particles is swallowed by the event horizon, the other particle can escape. The escaping particle is often a massless particle, such as a photon, because producing one with mass would require substantial energy to meet its rest mass.

In essence, this process allows energy to radiate from the black hole in the form of Hawking radiation.

The Casimir effect

An intriguing manifestation of quantum vacuum activity is the Casimir effect. This phenomenon occurs when two parallel metallic plates are placed close together in a vacuum. Between the plates, virtual photons can occur in the space between the plates due to Hawkins previously discussed proposal. 

If the wavelengths of the virtual photons fit an integer number of times into the gap between the plates, due to the principle of destructive interference.

 If a wavelength does nor resonate between the plated, it can es out after repeated reflections.

Therefore, the wavelengths between the plates can only have resonant wavelengths . However, outside the plates virtual photons can have any wavelength without canceling out. 

This difference in the number of virtual photons inside and outside the plates creates a disparity in energy density. Since fewer photons exist between them, the energy density in this region is effectively lower, which can be described as negative energy. The result is a measurable force pushing the plates together.

This force has actually been detected!