The measure of all motion?

The big bang was not an explosion IN space, it was an explosion OF space. No matter was "expelled" from the center, the space between bits of matter just keeps getting bigger. Just as no point on the surface of an inflating balloon is the center of expansion, the big bang has no center (in three-dimensional space, anyway). Another way to look at it is that all points in the universe are equally the "center," at least from their own perspective

The velocity of expansion of the universe is measured by the Hubble Constant, about 72 km/sec/megaparsec. That means that 2 objects that are 3,260,000 light-years apart are separating at a rate of 72 km/sec due to expansion of the intervening space.

But surely if the universe is 3-dimensional, it has a center, whether it can fairly be considered a focal point or not. If objects are getting farther away from eachother, how is space not moving? If space is moving, in what direction is it moving? If space is expanding, from which focal point is it expanding?

Basically, all I need to know is what speed you would have to be travelling and in what direction in order to be completely still by comparison to the universal measurement of motion.

It is difficult to imagine the expansion of a centerless 3-dimensional space, but this web site may help:

Expansion of the universe

A 2-dimensional analogy is the surface of an expanding balloon. There is no point on the surface that is the center of expansion. You need an additional dimension to pinpoint it.

What makes you think that the universe only has 3 dimensions? It is most likely 10 or 11 dimensional according to string theory.

Are you at all familiar with Einstein's theory of relativity? There is no universal measurement of motion. The closest we can come to a reference frame for the universe is the Cosmic Microwave Background Radiation. The local group of galaxies is moving at about 600 km/s with respect to the CMBR, and the Earth itself is moving at about 370 km/sec in the direction of the constellation Virgo.

CMBR map

So to answer your question, if you left Earth and headed away from Virgo at 370 km/sec relative to earth, your would be at rest relative to the CMBR.

cold,

I want to back up Terry's very nice explanation of physics. There is no reason that a 3 dimensional Universe needs to have a center.

However in my physics class, I said that *I" am the center of the Unverse. The students that undetstood this got good grades.

(Note: There is nothing wrong about saying that I am at the center of the Universe, as long as you accept the fact that this can be said, just as correctly, about any other point in the Universe.

Strangly, saying that there is no center to the Unverse and saying that every point is the center of the Universe is the same thing.)

Humans perceive 3 dimentions plus time, but present science believes that there may be as many as 20 dimentions and the flow of time may be more delusion than reality. The others have expressed the main physics opinion which could change radically over the next few decades. At present there is no center, no outer edge, no staionary (except you can pick any moving object and define that as stationary)
Does the universe have volume a that includes those portions receding faster than light? Probably not. 13,600 divide by 3.26 times 72 = 300,000 kilometers per sec which is approximately the speed of light. The 13,600 is the time elapsed since the big bang and the distace to the point where space is receeding at the speed of light in millions of light years/millions of years. Please correct, refute,embellish. Neil