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Posted by yelmalio/">yelmalio on November 23, 1999 11:29:03 UTC
What is the Universe that we should be mindful of it?
A question I have seen here several times (mostly by Human I. Scientist) is simply "what is matter?". A lot of people also ask, what is gravity?
Gravity is commonly explained by physicists as the distortion (bending) of spacetime by a mass. To understand this think of it like this. Assume you live in Flatland, a 2 dimensional universe on top of a sheet of paper. You walk along flatland and everything seems normal and OK to you. If some one in our Universe folded the paper then our Flatlanders straightline course along the sheet would change. This change in direction he would feel as an acceleration (acceleration is defined as rate of change of velocity, speed or direction). The flatlander can not conceive of "up" or "down" but he could intuit that the "flat" space he lives in is curved into a higher dimension. In the same way our 3 normal dimensions can be bent into a higher fourth dimension and this is what we feel as Gravity - an acceleration caused solely by the geometry of the Universe.
If we describe the force (of Gravity or Electricity) at all points that it acts on then we describe a Field. Physics is nothing more than a study of the fields governing the forces that hold things togehter.
What though is mass? Mass is made of atoms and atoms in turn are made of particles. It is found that there are many, many types of particles with many properties. To explain the variety of particles and properties Physics invokes group theory. To generate a group you need a mathematical function that is a group generator. This group generator is interpreted as a Quark, another is the Lepton. Does this help so far, no. It is now also thought that an even simpler object, the string, is what we see as quarks, leptons, gluons and such like. Particles become nothing more than the vibrational modes of a string. All particles, though, can be thought of as probability waves in Quantum Mechanics. But probability waves are not particles and do not have mass.
Any force, gravity, electromagentism, weak and strong nuclear force, can be expressed as a field. This field in turn can be treated as a particle in Quantum Mechanics, called gauge bosons. All forces except Gravity has a particle that is the carrier of that force. Why? Because gravity is explained solely as a problem in geometry and not in terms of particles.
The biggest challenge facing modern Physics is simply this, marrying the Quantum universe of particles and gauge bosons to the Geometrical interpretation of Gravity.
But this still does not answer, What is Mass? The best idea to date is that there is another type of field called a Higgs Field. Particles traversing this field, which is thought to exist everywhere, interact with it and gain mass by coupling with the field. But this means that the Higgs Field has a force carrying particle, or gauge boson, this is the Higgs Particle.
It is this Higgs Field that is thought to create mass, powers the inflationary stage of the Big Bang and is generally responsible for the Universe being what it is. Note, "it is thought" and not "implicitly assumed to be absolutely correct". The existence or non-existence of this field is a goal particle detectors are working towards.
To help explain this plethora of disparate bits of knowledge theorists have now put together a new version of Einsteins Equations in 10 and 27 dimensions. These contain as special cases, Relativity, all known particles as described by group theory, electromagnetism, weak and strong nuclear forces. The solutions to these equations yield millions of possible universes, most of which look nothing like ours. What all this says is that something, as yet unknown, is governing how the Universe behaves. Current ideas are beginning to uncover a glimmering of how complex the Universe really is and how much more there is yet to understand. Obviously, this all leads to a lot of other questions, as yet unanswered.
To close, the Universe is not wierder than you think, it is more wierd than we can possibly imagine.
Yelmalio - apologies to Michio Kaku.
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