Steven Hawking on: What are Virtual Particles?
In his paper Does God play Dice? Steven Hawking says:What we think of as empty space is not really empty, but it is filled with pairs of particles and anti particles. These appear together at some point of space and time, move apart, and then come together and annihilate each other.
These particles and anti particles occur because a field, such as the fields that carry light and gravity, can't be exactly zero. That would mean that the value of the field, would have both an exact position (at zero), and an exact speed or rate of change (also zero). This would be against the Uncertainty Principle, just as a particle can't have both an exact position, and an exact speed. So all fields must have what are called, vacuum fluctuations. Because of the quantum behaviour of nature, one can interpret these vacuum fluctuations, in terms of particles and anti particles, as I have described.
These pairs of particles occur for all varieties of elementary particles. They are called virtual particles, because they occur even in the vacuum, and they can't be directly measured by particle detectors. However, the indirect effects of virtual particles, or vacuum fluctuations, have been observed in a number of experiments, and their existence confirmed.
If there is a black hole around, one member of a particle anti particle pair may fall into the hole, leaving the other member without a partner, with which to annihilate. The forsaken particle may fall into the hole as well, but it may also escape to a large distance from the hole, where it will become a real particle, that can be measured by a particle detector. To someone a long way from the black hole, it will appear to have been emitted by the hole.
This explanation of how black holes ain't so black, makes it clear that the emission will depend on the size of the black hole, and the rate at which it is rotating. The radiation will be otherwise independent of what went into the hole.
Die auch im Vakuum sich ständig bildenden "virtuellen" Teilchen-Antiteilchen-Paare existieren i.A. nur etwa 10-23 sec.
Das Universum borgt sich dazu Energie, lebt ständig auf Pump und verhindert so ein absolutes Nichts.
Präziser: Ihre Lebensdauer multipliziert mit dem Doppelten ihrer Energie ist kleiner als das reduzierte Plancksche Wirkungsquantum: [1], [2]. Eben diese Eigenschaft macht sie virtuell, d.h. nicht einzeln beobachtbar.
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Bessere Erklärungen des Begriffs virtueller Teilchen