The hypothesis that the number of possible states of every finite volume of space-time is finite.

The Finite Universe Hypothesis

Finite Universe is the hypothesis that:

  • Finite nature holds;

  • The universe is spatially finite;

If the Finite Universe hypothesis is true, the entire universe is finite in every respect - including temporally.

If the universe is spatially finite, the question arises about how big it is.

A spatially finite universe does not require that there be an "edge". Rather periodic boundary conditions would be employed.

If periodic boundary conditions are used, it seems quite possible that the universe is much smaller than what would be suggested by the apparent diameter of the visible universe.

This would be rather difficult to detect experimentally - so it is not very suprising that such a regularity has not yet been identified.

The problem is that - when you look out into space, you are looking backwards in time. Consequently you don't see exactly the same configurations repeated - in a regular pattern - but rather snapshots of the earlier evolution of the system at varying times.

This explains why you don't necessarily see much the same things in the distance when you look in diametrically opposed directions.

What about the fact that distant galaxies are all receeding from us? In a finite universe would we not see as many approaching as receeding?

There are several possible ways this could be resolved:

  • "Tired light" - the idea that interstellar space gradually saps the energy of light in transit through it.

  • Speed of light decay.

Then there's the possibility seems to be that space is bending and stretching under the influence of gravity. The early universe would be dense and consequently time-dilated due to gravity. The universe would effectively be stretching - but at any time would remain finite.

Other observations suggest that there are problems with the redshift data. [Redshift Quantization]is often invoked in this connection. To quote from there:

A galaxy's redshift may not be a Doppler shift, it is the currently commonly accepted interpretation of the red shift, but there can be and are other interpretations. A galaxy's redshift may be a fundamental property of the galaxy.

Such notions cast doubt on the conventional red-shift interpretation.

Having said this, evidence for universal expansion is fairly well established. Such evidence suggests that - if the universe is finite, it is comparable in size to the visible universe.

Finite Universe has some explanatory power. It explains spatial homogeneity - which otherwise seems mysterious - despite the attempts of inflationary scenarios to explain it.

Also it is consistent with Berkeley and Mach's hypothesis that all the matter in the universe is collectively responsible for experienced inertia.

Then there's some work in quantum cosmology - which seems to suggest a low- volume universe is more probable than a high-volume one, and an infinite universe would have zero probability of coming into existence.

It appears that testing the theory that the universe has periodic boundary conditions - and is smaller than the visible universe - would probably require a comprehensive statistical analysis of the presence of he background radition - or very long-lived objects to test.

The National Aeronautics and Space Administration's Microwave Anisotropy Probe (MAP) has now been launched - and seems likely to produce results relevant to this question shortly. The first results are expected in 2002.

This issue is currently being seriously discussed by cosmolgists.

Tim Tyler | |