Crosson said:
The key thing about vacuum energy is that it should be the same energy density everywhere in the universe. Cosmologist believe it is constant through time also, the vacuum energy is called the cosmological constant.
This is where I believe the misunderstandings regarding vacuum energy begin. Even many of the top people researching ZPE fall into this trap, and it shows in their papers. ZPE is expressed through fields, and fields can be polarized, densified, or rarified. Even at absolute zero, the vacuum is swarming with particle-antiparticle pairs. The pairs can be prevented from arising by the simple expedient of physical exclusion. A Casimir device demonstrates this by physically preventing some wavelengths of the ZPE field from arising simply by restricting the space in which the pairs can form. Solid matter physically prevents particle-antiparticle pairs of many more (but perhaps not all) of the wavelengths of the ZPE from forming.
As for polarization: If the alignment of these virtual pairs can be affected by the presence of matter, then the ZPE field will be both polarized and densified. At the quantum level, the behavior of particles is not straightforward and the chance of finding a particle at a certain place at a certain time between point A and point B is a matter of summing amplitudes of probability of the various paths that the particle could take from A to B. See the wonderful Feynman lecture series at VEGA:
http://www.vega.org.uk/series/lectures/feynman/
If matter and antimatter are attracted to one another, virtual particle pairs will arise preferentially oriented with the antiparticle closer to the dominant local mass, and with respect to the local polarized ZPE field. It takes less energy for the pairs to arise in this orientation and therefore quantum physics tells us that a preponderance of the pairs in the field will be so oriented. In this scenario, the ZPE field has been polarized, and because that orientation promotes packing, the field is also densified. The Athena Project (link below) is dedicated to producing experimentally-useful electrically neutral antihydrogen. If the gravitational infall rates of antihydrogen and hydrogen are not equal, the simplest, most intuitive method of polarizing the vacuum fields will have been discovered.
http://athena.web.cern.ch/athena/
Another common misunderstanding relates to the total energy of the vacuum, with a nice overview here:
http://arxiv.org/PS_cache/astro-ph/pdf/0005/0005265.pdf
The ZPE field theoretically contains 120 OOM more energy than required by the cosmological constant, BUT this is only if we calculate this energy in relation to a perfect vacuum, as envisioned in quantum theory. The problem here is that the ZPE is the Ground State of our universe, and there is no perfect vacuum. Since we can only sense and exploit energy differences, the 120 OOM energy problem is a moot point. As an example that even young children can understand:
Q: How can a bird perch on a high-voltage wire without being fried?
A: The bird comes to the same voltage potential as the wire on which it perches. Without reference to a higher or lower voltage reference, the bird is safe. If she should be able to touch an object that is referenced to a much higher or lower voltage (like a grounded utility tower), though, POOF!
We are in exactly the same situation with ZPE. Theoretically, the vacuum has incredible potential energy, but since it is the ground state of our universe, there is no way that we will be able to exploit it unless we find a way to either densify or rarify a ZPE field so we can exploit that differential.
Stupid questions for 100: what is Dark Matter? What is it do? What is meant by vacuum? Because I think I might be thinking of vacuum in the wrong context?
, but I seriously want to know about this stuff because its interesting.
