Bob
The Earth's magnetic field is shrinking - this is not evidence for a young Earth.
If you examine the magnetic field polarisations in certain rock strata you will find that it switches direction as does the Earth's magnetic field.
The Eaths magnetic field will shortly (in geological terms) vanish and then reverse and get stronger.
You must be careful of accepting what you read on the internet at face value.
If you google search age of the Earth you will get a large number of sites telling you the Earth is young and that carbon dating is rubbish etc. etc.
Strangely these are almost exclusively American and in a religious context.
It's not actually difficult - let's ignore radio carbon dating.
1/ Ever looked at a map? ever noticed how Africa Europe and America look like they could almost fit together?
They have been moving apart for millions of years. We can actually measure it now, directly. - about 2cm a year.
The Atlantic is about 3,000 Km wide if the Earth were 10,000 years old it would have to be moving at 300 meters a year.
2/ Why don't we find human or even rabit skeletons with dinosaur bones?
These are just 2 trivial example there are many different techniques and they all point to an old Earth - I can't find any reference to the mensa thing you refer to
For those interested in the History of how we got the Earth's age there's a great Radio discussion you can listen to here:
http://www.bbc.co.uk/radio4/history/inourtime/ inourtime_20031120.shtml
(select listen again on the left hand side)