Tuesday, February 19, 2008

Unraveling the mystery

Let me revisit once again something I touched upon In Skeptics and True Believers.

I mentioned to a friend the other day that there is an arm's length of DNA in every cell of the human body. His perfectly reasonable response: How could there be an arm's length of anything in something too small to see with the naked eye?

I might as well have asked him to believe in hobgoblins or unicorns.

Let's do the math.

We know from X-ray diffraction studies that a strand of DNA is 1.5 nanometers in radius (1.5 billionths of a meter). Assume a cylindrical molecule 1 meter long with a radius of 1.5 nanometers. The cylinder has a volume of 7x10-18 cubic meters. A typical animal cell is about 8 micrometers in radius. Assume a spherical cell and calculate the volume: 2100x10-18 cubic meters. The cell has 300 times the volume of the DNA strand. The DNA fits neatly inside.

Or put your head around this apparently outlandish claim: The DNA in your body, if stretched out end to end, would reach to the Sun and back 30 times. No way!

Do the math. An arm's length of DNA in each of, say, 10 trillion cells. Ten trillion meters. Ten billion kilometers. Six billion miles. A round trip to the Sun is (approximately) 200 million miles. QED.

Lovely illustrations of the power of math as an aid to the imagination!

Many of us tend to believe those things that give us a sense of empowerment over our bodies or of being the focus of cosmic attentions: astrology, UFOs, reincarnation, angels, out-of-body experiences, miraculous cures, parapsychology, personal gods, etc., for none of which is there a shred of nonanecdotal, reproducible evidence. Meanwhile, the real wonders go by the board. As the naturalist/cartographer Tim Robinson wrote: Miracles are explainable. It's the explanations that are miraculous.