h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Regret I didn't manage to get to this Entry much when it was in PR. However,

However, '...you are made of roughly 100 trillion of them...'

The figure I have written in my notes,which I try to keep up to date, is 75 billion

'They range from a few micrometres to the size of an ostrich egg'.

For the record, a human cheek cell is roughly 2.5 micrometres in diameter.
The largest cells are slime moulds, which occur in dead wood, and reach the size of a dinner plate. These are multinucleate cells formed from coalescing amoebae whose name I can't recall.

Stretched out, the DNA from a single human cell would measure 1.5 metres. So, I once calculated that, with 75 bn cells, the DNA from a single human being would stretch from Earth to Moon 3 times

I was surprised to find a number in the trillions, so I did check with a couple of sources. http://ask.yahoo.com/20020625.html and Wikipedia both give something between 10 and 100 trillion - meaning 10 to the 14 (100,000,000,000,000). Using an 'old' billion, that number would be read as 100 billion; using a 'new' or 'American' billion, it's 100 trillion. Perhaps that's where the difference comes from?

Gif

Yes, quite likely. Just shows tht it;s better to use 'times 10 to the power of....' convention to avoid confusions.