Comments on: Particle Physics Experiment Will Use Ancient Lead From a Roman Shipwreck

By: Sarah

Sarah — Wed, 07 Jul 2010 00:46:43 +0000

Matt T and williejoe:

The natural abundances of radioactive elements in lead will be similar for all lead still in ore form. However, smelting lead removes most of these elements because they are insoluble in liquid lead and the slag can be scraped off before the lead is poured. Thus, the earlier the original smelt, the lower the radioactivity of the lead.

Also, lead is the stable end-product of the uranium decay chain, so most of the lead on earth actually came from primordial U-238 in the earth’s crust.

By: williejoe

williejoe — Mon, 26 Apr 2010 20:43:01 +0000

matt t is right-on—the purity of the roman lead relative to all other leads has nothing to do with the fact that it’s old and therefore has undergone more nuclear decay—-all the lead on earth was created in stars billions of years ago and has essentially the same percentage of the 210 isotope—–the lower radioactivity level is associated with other radioactive impurities which are effected by how the lead was processed 2000 years ago

By: Matt T

Matt T — Mon, 19 Apr 2010 23:33:08 +0000

Why does the radioactive half-life counter start ticking after it is extracted? What is the difference between the lead in the ground and the lead already extracted? I guess what I’m asking is how does the lead “know” that it is extracted?

By: Dick Mack

Dick Mack — Sat, 17 Apr 2010 01:24:05 +0000

Thank you JMW, that is exactly what I wanted to know. Now, are there any other contaminants in Roman lead that will confound the experiment? And how will they be removed?

By: JMW

JMW — Fri, 16 Apr 2010 23:59:09 +0000

Let’s see. Half life of 22 years, for 2,000 years…the lead’s natural radioactivity should be down to about 4.3 * 10^-28, or .00000000000000000000000000043, of what it was 2,000 years ago.

By: Evan Harper

Evan Harper — Fri, 16 Apr 2010 18:40:16 +0000

Awesome! I’ve heard of the same trick done with iron from the WW1 German Kriegsmarine fleet scuttled in Scotland, but ancient Roman lead is even cooler.