After I posted this I bacame more and more sure that it was Russell Humphreys who wrote the book I referred to, so when I managed to get a spare half hour I had a look at the True Origins site, which is one of the more reasonable creationist sites.

(Ken Smith) writes:

This is my third response to Don’s initial post on cosmology and, like the second, can be read independently of the other two. This uses rather more technical terms than the others – if anyone doesn’t understand something please let me know.

[deletions]

The two attempts I was referring to are the writings of Barry Setterfield, which I now gather are no longer supported by Answers in Genesis, and a book by an author whose name I can’t recall (Russell Humphreys comes to mind, but I won’t swear that is correct), who put forward the suggestion that the universe started off as a sphere of water a couple of light years in diameter which God then turned into a “white hole” – Don can probably supply the author’s name and title of the book. If Don wants criticisms of these I’ll be glad to supply them.

I might as well say something about Humphreys’ book “Starlight and Time”, which was the one I saw several years ago. It was published in 1994. It has come in for a lot of criticism on all sorts of grounds, and some of these, with responses by Humphreys, can be seen if you go to

http://www.trueorigin.org/ca_rh_03.asp

I haven’t read all of Humphreys, but assuming that the critics have quoted him correctly, I was clearly wise in not expending my hard-earned shekels on the book. I’ll just recount here my reaction to his idea of the universe starting off with a sphere of water one light year in radius.

There is an exact solution of teh field equations of general relativity outside a spherically symmetric mass, which Karl Schwarzschild (I’m not sure of the precise spelling, but you can find it in most of the articles on the above site) obtained.

In this one component of the metric tensor is found to be 1 – 2m/r where, as usual in theoretical work in general relativity, the units have been chosen so that the constant of gravitation G and the speed of light c both take the values 1. If normal units are used the expression for this component is 1 – 2Gm/(r c^2)

The solution breaks down – in technical terms the event horizon occurs – where this term is zero, or

r = 2Gm/c^2

and this must be *inside* the boundary of the mass for the solution to be valid. Now the radial coordinate gets distorted in general relativity, but as a quick test to see if the solution is anywhere close to the right ball park this can be ignored if we are just interested in checking, and don’t actually want to investigate details of the solution.

I grew up in an era when cgs units were the standard, and the values of assorted constants in those units have remained in my long-term memory.

For a sphere of radius R the volume is 4 pi R^3 / 3, or, taking pi = 3 as a good enough approximation, and the density of water as 1 gm/cc we get (in cgs units) the mass of this sphere as 4 R^3 The gravitational constant G = 6.6 x 10^(-8), approximately. Rewrite the above equation as

r/c = 2Gm / c^3

and substitute the numerical values and we have

r/c = 2 x 6.6 x 10^(-8) x (R/c)^3

Now since the radius is 1 light year, we use this to convert the term on the left into light years, and drop one of the R/c terms on the right, so

radius of the event horizon = 2 x 6.6 x 10^(-8) x (R/c)^2

There are approximately 32 million, or 32 x 10^6 seconds in a year, so R/c = 32 x 10^6, and putting all this together we have

radius of the event horizon = 2 x 6.6 x 10^(-8) x (32 x 10^6)^2

which works out at about 500 x 10^6 – the magnitude is the important thing, not the exact value.

So the event horizon for this sphere of water is at a distance of 500 million light years!

All this I did in a few seconds of mental arithmetic. I suspect the person behind the table on which the creationist literature was displayed might have been offended by my laughing.

This is simply ridiculous! And it is put forward by Humphreys as serious science!

I have mentioned his ideas to various physicists and mathematicians familiar with general relativity and their reaction has been the same: amusement.

And none of them had ever heard of Humphreys before I mentioned this, so he isn’t very well known, at least in the moderately large group of people at the University of Queensland who are knowledgeable about general relativity.

In this case I’m personally glad that the work remains unknown in scientific circles, outside those who take an interest in creationist writings. It’s just too much of an embarrassment.

[rest of my earlier post deleted]

Salaam Ken Smith

— Dr Ken Smith – Christian, husband, unpaid mathematician, skeptic, … `Last season we went to an AFL game at which a large number of young women seemed to be constantly whipping up their tops and attaching tiny persons to their nipples.’ Jane Frazer, on breast feeding in public