# Difference between revisions of "Universe"

The universe is, in principle, all of material existence or natural things (matter and energy). Therefore, everything outside of the universe is not natural or material, but supernatural (things going beyond nature). However, in order to solve problems with naturalistic explanations of the the origin of the universe, some speculate that there are other universes.

There have been and continue to be a number of competing ideas about the universe, but most agree that the universe is expanding. The size, shape, and age of the universe, as well as how it began, are, however, all points of contention.

## Shape

The common view among cosmologists is that the universe is a four dimensional Riemannian manifold whose spatial part of the metric is increasing over time. This is interpreted as an expansion of the universe.

Imagine you are at a random spot on a spotted balloon, when someone inflates the balloon you'll see the spots moving away from you, so it would seem you are at the center of the expansion. Furthermore, the further away the spots are the faster they move away from you. This is also true for the universe: the more distant a galaxy is, the faster it moves away from us.

Further imagine that you are a creature that only exists in two dimensions. That is, you have width and depth, but no height. So living on the surface of the balloon, you cannot see the shape of the balloon itself. If you went for a walk in a straight line, you would actually go around the balloon and end up where you started, despite not being aware that you were travelling in a circle.

The theory goes that the three dimensions of our universe that we can see are like the two dimensions of the surface of the balloon, which wraps around on itself in another dimension, so that if we travelled through space in a straight line, we would eventually return to our starting point. The fourth dimension is time and String theory holds the universe exists right up to ten dimensions.

One consequence of this idea is that the universe therefore has no edge (just like there is no edge to the surface of a balloon) and therefore no center. Thus for any location in space, it would appear that that location is at the center of the expansion of the universe.

If we were really at the center of the universe, this would support the idea that the Earth occupies a "special place" in the universe, which would support the biblical idea of creation, even though the Bible does not claim that the Earth is physically in the center of the universe. So many scientists find the idea that it only looks like we are at the center of the universe an attractive one.

In the mid 1970s the astronomer William Tifft put forward the idea that red shift distances were quantized and possibly organized into spheres. If the observations were accurate, then it would suggest that the Earth is at or close to the centre of these spheres. While this centre is not necessarily the same thing as the centre of universe, it would certainly put Earth in a "special place".[1] However, Tifft's original data involved a relatively small sample of around 200 bodies. Later observations have revealed that there is red shift clumping, due to structures such as supercluster complexes, it is random in terms of direction and does indicate any symmetrical pattern[2][3].

## Age

According to the Big Bang theory, the universe erupted into existence from a highly compact singularity[4][5] approximately 13.7 billion years ago, and has been expanding ever since. This is the current scientific consensus and is agreed upon by the vast majority of the scientific community[6].

Ancient Christian Biblical accounts disagree with contemporary science, and adherents to such are known as young Earth Creationists. Bishop James Ussher calculated the universe was created on October 23, 4004 BC. While this is not the only biblical chronology which has been developed, almost all chronologies give a creation date near 4000 BC[Citation Needed].

This gives rise to the "starlight problem" for some Christians, although there is nothing inherently illogical about the creation of light in situ to inform humanity of the existence of objects farther away than 6000 light-years. Believers in relativity have constructed a number of models which explain the age of the universe as being affected by the time-warping effects of gravity as predicted by Einstein's General Theory of Relativity, so that the age of the universe as measured by a hypothetical observer at the edge of the universe might be 14 billion years, but as measured by an observer on Earth is only 6,000 years.[7]

## Size

A recent calculation placed the visible universe at about 156 billion light years across.[8] This creates a dilemma of faster than light movement, but it is speculated that the expansion of space itself can exceed the speed of light even if the objects within it moving on their own can not.[8] As an analogy, imagine ants (galaxies), that can't walk faster than 20 centimetres per second, sitting on an elastic cord. Normally two ants moving away from each other could not exceed a speed of 40cm/s relative to each other (speed of light). However, if the cord is stretched while the ants are moving (expansion of space), the ants' speed relative to each other can be greater.

Current theories on the universe means that scientists are only able to account for 4% of the matter in the universe, so new theories of dark matter (unseen matter) have been developed to explain this.[9]