Red shift problem?

[Paul365]

If you assume both that the solar system has existed for over 4 billion years, and that the space expands between these objects, they would surely be a lot further apart than they are today, given the calculations made concerning size and age of the visible universe

I think the main problem of debates of this kind is the difference in knowledge of participants about the subject of the debate. Therefore for a fruitful debate it would be very good for everyone to start with some some basic, agreed understanding of the Big Bang theory. A very good starting point is the link to the Yale course that was posted by Clearsky and others here several times.

To give a basic answer to your question: Space expands extremely slow. Its scale factor increases at the moment by 2 x 10^-18 per second. That's 6 x 10^-5 in a million years. The influence of the gravitational forces in the solar system is way bigger. Therefore you can't see an expansion of the solar system. The only object where you can directly observe space expansion is a photon, a light particle. It grows bigger over time and therefore it's wave length increases. Billion years old photons that we receive from far away galaxies are expanded, and this is a measurable effect.

I hope this helps. You can find a good explanation of space expansion on Wikipedia: http://en.wikipedia.org/wiki/Metric_expansion_of_space

 

[Tinker Grey]

Paul365,

I would like units on your numbers. 6 x 10[sup]-5[/sup] what per million years? Meters?

Thanks.

 

[Paul365]

It's a factor. No units. Multiply it with any length and you get the expansion of the length over time. For instance, if you take a photon and wait a million years, then it's wave length has increased by 6 x 10^-5 times the original wave length.

 

[Graham4C]

The influence of the gravitational forces in the solar system is way bigger. Therefore you can't see an expansion of the solar system.

That's exactly what i was talking about with regards to the big bang. While the distances were still relatively small, gravitational force would overcome the rate of expansion and the matter would be held together

 

[Hnefi]

That's exactly what i was talking about with regards to the big bang. While the distances were still relatively small, gravitational force would overcome the rate of expansion and the matter would be held together

Oh, now I understand. Well, your question makes sense under the assumption that the rate of expansion was constant. Apparently, it was not, and was never really thought to be. I believe (though may be mistaken) that in the early versions of the big bang theory, the pressure caused by the small amount of space and the vast amount of energy forced the universe outwards - rather like modern stars, which would collapse in on themselves if it wasn't for the pressure from their own radiation that counteracts gravity.

The modern theory has another solution, however. It is called cosmic inflation, and solves a number of problems with the theory (though your particular objection was, as noted, already solved IIRC). Look up the term 'cosmic inflation' on Wikipedia or the scientific journal of choice for details. I'm not qualified to explain it.