The ethics of researh: destroying 2,000 years old artifacts

[MarkB]

Indeed. Given that most of the info from the lead bars is on the surface, they could make a mold of the bars, and thus retain the knowledge before melting them down.

Or hollow them out, leaving the surface layer intact.

 

[freyar]

Good questions...

Is the contaminant already in the lead, or mixed in from the environment (after the lead is mined)?

It's already there. I can see how my last post could be confusing, but Umbran has the right of it I think (keep in mind I'm not a geologist). U-238 is literally all over the place in small amounts, including in the lead deposits being mined. So that is constantly producing Pb-210 in the lead deposits. Some Pb-210 could also get mixed in after mining, but I think that would be a small amount comparatively.

Once the contaminant is in the lead, is letting the lead sit in an isolated environment for an extended period of time the only effective way to remove the contaminant? (Letting what's there decay away, while not allowing any replenishment?)

It is the best way to remove the Pb-210. Most of these experiments use mined and purified lead, though. The way lead (or other elements) isotopes are separated out (purifying a sample from radioactivity) is usually centrifuging because the different isotopes have different atomic masses due to the different number of neutrons (as Janx said). This process works quite well for most purposes (it's how uranium is enriched --- purified into the effective isotope, if you will --- for fuel or military use, for example), but these particle physics experiments want to get rid of every last bit of radioactivity possible. And lead that's been isolated under the ocean for hundreds of years happens to be less radioactive than what we can do with centrifuges.

If contaminant is already in the lead, is there any significant difference in the level of contaminant in lead from different natural sources?

Well, I'm sure there is some natural variation, but you'd have to centrifuge it anway. So you'd just get to the same level after that process.

If the contaminant is mixed in from the environment, is the environment different now than it was a couple of thousands of years ago (in terms of the amount of contaminant present)?

No, U-238 has such a long half-life that a few thousand years wouldn't make a difference.

If the contaminant is mixed in from the environment, is there any way to process the lead to avoid contamination?

No, and, as noted, the Pb-210 would already be present before mining.

 

[tomBitonti]

Hi,

Thanks for the answers!

I'm guessing the contaminant is refreshed continuously by materials in the ore which contains the lead, which would be why the decay timer starts when the lead is smelted.

I'm wondering, then, if there are any alternative sources than the bars. I suppose that depends on the amount of time necessary for the contaminant to decay out. Perhaps there is a supply of old roman pipes which could be used.

Thx,

TomB

 

[Janx]

Or hollow them out, leaving the surface layer intact.

I'm thinking the work to put a bar in a vise and running a drill/router head into the bottom of it is pretty damaging, so much so as to not be worth it.

Far simpler to save 5 bars, make a few molds of any other ones that look special, and use the rest for other science needs.

Besides, the Doctor worked pretty hard to make sure those ships sunk so they could wear off the Pb-210, so they could be discovered and used for a dark matter experiment so he could detect the alien invasion when they begin bombarding the earth with neutrinos.

Don't mess up the timeline!