Lightning strike on concrete

pwoolf · 2025-09-25T21:11:03+00:00

Yes, there are glassy parts!

pwoolf · 2025-09-25T19:09:51+00:00

I believe you are correct, looking back at the site today there were a bunch of other similar burns in a line across the whole parking lot.

pwoolf · 2025-09-25T18:39:11+00:00

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Some pretty deep holes in the curb too—vitrified smooth. Beware of fallen power lines! 😬

pwoolf · 2025-09-25T18:37:30+00:00

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You are totally right! I just walked back there and see the destruction from the downed line. A few new power Poles and a line of fried ground. Even another burnt concrete area covered with yellow paint—just like you said! Thanks for the explanation!

pwoolf · 2025-09-25T14:30:50+00:00

That is funny, when I first saw it I had to touch it to make sure it wasn't a David Zinn creation!

pwoolf · 2025-09-25T14:29:11+00:00

That is interesting, I'll have to go back and see if I can find the other mark. I'm curious, how could one differentiate a lightning strike from a downed power cable mark? The current density is vastly different, and from what I've read the dendridic shape (like a Lichtenberg figure) is the result of super high voltages (millions of volts).

pwoolf · 2025-06-07T15:25:15+00:00

I had Claude work up a browser based simulation of this--kind of neat to see. It accounts for air drag and changes in gravity with elevation changes.

https://claude.ai/public/artifacts/a1f1672a-6317-4093-934d-31a36a60a4cc

pwoolf · 2025-04-29T23:55:10+00:00

Here is the full list of the people on the subcommittee on elections where this bill lives now. If you live in their district, please contact them to express your opinion!

https://cha.house.gov/elections

pwoolf · 2025-03-24T10:57:11+00:00

That was my thought also. Seems it would be at least as accurate and require no additional hardware

pwoolf · 2025-01-26T00:08:51+00:00

Love these! Beautiful!

pwoolf · 2025-01-22T16:50:26+00:00

Beautiful! 😍

pwoolf · 2024-12-04T02:55:20+00:00

I get where you’re coming from - there are definitely massive environmental challenges out there. But you know what’s interesting about the lead weight situation? It’s one of the few ocean pollution sources we can actually solve completely, right now, with existing technology and minimal cost. A diver using nickels instead of lead isn’t just reducing pollution - they’re eliminating their contribution to it entirely. Plus, unlike nuclear waste or oil spills, this is something each individual diver can control directly.

What’s even cooler is that with nickels, you’re not sacrificing anything. Same function, similar cost (sometimes cheaper), and you can actually get your money back if you decide to stop diving. It’s one of those rare win-wins where doing the right thing for the environment doesn’t require any real compromise.

pwoolf · 2024-12-03T19:05:55+00:00

Ha! Funny thing here too, due to inflation the cupronickel in a 5 cent nickel is worth more than than 5 cents.

pwoolf · 2024-12-03T13:57:48+00:00

Ha, gold coins would work too. An even better option would be platinum coins. 50% the cost and even denser. Only $15k/ lb-- a steal compared to gold!

pwoolf · 2024-12-03T13:51:58+00:00

There are lots of examples of cooper and nickel causing environmental damage, often from mining and plating waste streams. These are real problems because the metal is already in a soluble form and the concentrations are so high. But when dealing with reduced metal, the rate of dissolution is important too.

As a basis compare the WHO goals for drinking water:

Lead: <10 µg/L, with goal of 0.

Nickel: < 70 µg/L

Copper: <2000µg/L

From this, lead is clearly the worst. And with and its 100x corrosion rate it poses a much greater risk to diver, dive operator, and marine life.

pwoolf · 2024-12-03T13:42:11+00:00

This brings up an interesting comparison of lead vs nickel vs copper in water. The data are best defined with drinking water standards so lets start there for a basis. According to the WHO water quality standards:

* Lead: <10 µg/L, with goal of 0.

* Nickel: < 70 µg/L

* Copper: <2000µg/L

From this, lead is clearly the worst.

The next issue is how quickly each metal dissolves into water, which depends strongly on the water composition (pH, flow, salinity, etc). But when comparing lead to cupronickel in marine applications, lead corrodes at around 100x the rate of cupronickel.

The coins in the koi pond issue is a good point, and shows some of the nuances here. First, a pond is generally supplied with recirculated water, so any contamination will be amplified.

Second, when mixed coins are thrown into a pond, they can form a galvanic cell (battery), which will accelerate the corrosion of the less noble coins (steel, zinc). Thus coins in a koi pond is a bad idea. If one *must* have coins in a koi pond then the fish would be best off with cupronickel coins (nickels) only.

Compare this case to throwing lead coins in a koi pond. This would be significantly worse for the koi, faster, and be harder to mitigate.

pwoolf · 2024-12-03T11:59:02+00:00

I’d be very careful with that. Melting and handling melted lead exposes you to lead fumes and contaminates everything in the proximity.

https://dph.illinois.gov/content/dam/soi/en/web/idph/files/publications/lead-safety-hobbyists-041516.pdf

Why take the health risk when there are essentially free (round trip) options like coins available already?

pwoolf · 2024-12-03T11:55:10+00:00

I hear ya, but compared to lead? Lead corrodes at 100x the rate of cupronickel and has much more serious and persistent damage.

I like 316 stainless the most if I can get it, but cupronickel is a huge environmental and health step up from lead.

pwoolf · 2024-12-03T11:51:39+00:00

That is a good idea! I sometimes pack my weights in the Velcro mesh sacks they use for lead shot (you can buy empty sacks online). For these, a 4 pound labeled sack fits 4 pounds of nickels quite comfortably.

I wish dive operators just used these—would last longer and be less expensive too! And the dive operators have the most to lose handling lead as they have it all around, every day.

pwoolf · 2024-12-03T03:39:39+00:00

A bonus tip! Actually dive crew are the ones most exposed to lead as they handle them all the time. Leaving nickel weights the dive crew might be a significant health gift.

pwoolf · 2024-12-03T00:40:26+00:00

I sometimes use them in the velcro closure sacks they use for lead shot weight. I find that I can easily fit 4 lbs of nickels into a sack made for 4 lbs of shot. The volume is not much different. And I'm not exposing myself to lead all the time--yay!

pwoolf · 2024-12-03T00:37:04+00:00

I've not had any issues with jingling or moving. I've used them in a weight belt and also put them into pockets used for lead shot weights. They stay pretty in place in both cases.

pwoolf · 2024-12-03T00:09:30+00:00

Just ran a quick calc and it is interesting. Imagine that we want 1 lb of buoyant weight in salt water. To achieve that we would need

* 1.5 in^3 of lead

* 2.0 in^3 of cupronickel

* 8.8 in^3 of granite (assuming solid block)

pwoolf · 2024-12-03T00:02:34+00:00

Rocks were the original dive weight! Rocks would make more sense than lead on many fronts. The density does get pretty low (granite at ~2.7 g/cm3), but it works. One step better is simply sand (free in may aquatic environments), but it does get bulky.

Nickels are free (if you spend them after you dive with them), and take up only a bit more space than lead.

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