Quotes from Henning Genz

The universe is but one immense unit; it cannot be separated into spatial domains that are totally empty and others that are completely filled with matter. Matter and space can be distinguished from each other, but where we draw the blurred line between them is largely a matter of taste.

Any space that distinguishes directions and accelerations cannot be "empty", in Aristotle's meaning.

But for all practical purposes the formation of ice breaks the continuous symmetries of water non-deterministically. This non-deterministic symmetry breaking is called spontaneous symmetry breaking.

Can a cat vanish, but not its grin? Can structure exist without matter? This may be possible in the abstract interpretation of Plato and Plotinus; in a concrete sense, it is impossible. Structured matter can be interpreted as an excitation of unstructured matter, just as the cat with the grin may be seen as an excitation of the nongrinning cat.

If all of the presently observable universe pooled its matter to create one giant black hole, its radius measured in light-years would amount to the same number as its age in actual years: approximately 10^10.

REALITY OF ZERO-POINT ENERGY The uncertainty relation implies that there cannot be a region in space totally devoid of electromagnetic fields. They may well be absent on the average, but their energy fluctuations have to satisfy the uncertainty relation. We described the Casimir effect; it is nothing but a consequence of the inevitable fluctuations of the electromagnetic field. The fluctuations of zero-point energy are real and measurable, even if the zero-point energy itself is not.

If the universe as we know it is nothing but a vacuum fluctuation with a purloined total energy that is not much different from zero, it may exist for quite a while before the vacuum decides to call in the loan.

The space that is added as the universe expands has the same properties-curvature, energy density-as the parent space.

In another experiment Guericke connects a small glass sphere that's filled with air with a larger evacuated one. As he opens the valve between the two, air from the small sphere penetrates the large, empty volume; in the process, water droplets appear and sink to the bottom. This effect- the formation of droplets during rapid expansion has been used routinely in our century as a detection method for elementary particle tracks in an instrument called a cloud chamber.

Theory and experiment both show us that light does not need a material medium for propagation. We would have no trouble understanding this if light were nothing but particles zooming along through empty space. But that is not the way it goes: Light is a vibration, an oscillation made up of elementary oscillations we call photons. But there is no substance that oscillates when light propagates; thus we cannot impede the propagation of light when we remove substances from some given space.

The vacuum of physics contains in its faculties everything that the laws of nature will permit. It fluctuates-the virtual particles come and go. The only thing they may be missing is the energy it would take to make them appear as real particles. All that can appear in reality must be present as a possibility- as a state of virtual particles-in a vacuum. Addd energy to the vacuum and those virtual states may appear as particles.

Certain macroscopic objects directly display quantum mechanical effects. Superconductors and neutron stars-the latter behaving like atomic nuclei with a six-mile diameter-are macroscopic objects that cannot be described in terms of classical physics.

The quantity that physicists call the specific heat of a substance is defined as the amount of energy needed to raise the temperature of 1 g of this substance by 1 degree Celsius.

The oscillations-or waves-mandated by the Goldstone theorem originate in the application of symmetry operations to small domains.

There is no such thing as an indescribable material object. Every particle that meets its antiparticle gives up its identity and becomes radiative energy. In the process, the energy is conserved, but the structure of the particle-be it Democritus's sphere or a die, be it charged or neutral-vanishes. It dissolves into pure energy. All identity is absorbed in the sea of pure energy.

There is no such thing as an indestructible material object. Every particle that meets its antiparticle gives up its identity and becomes radiative energy. In the process, the energy is conserved, but the structure of the particle-be it Democritus's sphere or a die, be it charged or neutral-vanishes. It dissolves into pure energy. All identity is absorbed in the sea of pure energy.

The orthodox interpretation offers no explanation as to why everyday objects never assume quantum mechanical states that do not allow a classical interpretation.

It is impossible to bring a substance down to a temperature of absolute zero; there cannot be a blackbody without radiation because absolute zero cannot be reached. And that means that empty space in its true sense cannot be created.

John Maddox, the editor of the British journal Nature, had immediately suggested that the minister should be told that the Higgs boson can be explained similarly to the way we visualize the W and Z bosons: as carriers of information and effects. They permit us to understand effects that would otherwise look like long-distance action across empty space in the absence of any carrier.

In physics terms, the reason for symmetry breaking is the instability of the symmetric state.

Light is an excitation of empty space proper, of the vacuum. It is no more and no less.

Before the particles that we observe today materialized, all matter in the early universe must have gone through this stage of a quark-gluon soup, or plasma.

The gravitational field of Earth will determine the direction of the rock that you drop from your hand. Aristotle concluded, from the simple fact that the rock "knows" in which direction to move, that space cannot be empty where it transmits that knowledge. Both Newton and Einstein would agree-the former because the gravitational field of Earth acts at the location of the rock, the latter because Earth's gravitational field actually curves space in that location.

At the end of inflation, just as after the hot Big Bang, the universe is hot. It is, we might say, self-created by dint of its explosive growth: The inflationary process generates space, and the energy that space contains, from essentially nothing. To repeat Alan Guth's dictum, "The universe may be the ultimate free lunch.