8
$\begingroup$

I was imagining the possibilities of creating a ship mast which could not get struck by lightning. Is there a material it could be made of that would never get struck by lightning?

$\endgroup$
8
  • 5
    $\begingroup$ Ordinary wooden masts protected by lightning rods connected to the salty sea? See the work of William Snow Harris. Fun factoid: before the invention of the lightning rod, buildings were quite often destroyed in fires started by lightning strikes. After Ben Franklin, that became rare. Franklin invented the lightning rod in 1752; only ten years later, King George III of Great Britain installed lightning rods at Kew Palace, London. $\endgroup$
    – AlexP
    Jul 20, 2023 at 18:49
  • 1
    $\begingroup$ "Is there a material lightning does not strike?" You'd need something without any charged particles. $\endgroup$
    – RonJohn
    Jul 21, 2023 at 0:40
  • $\begingroup$ "Is there a material it could be made of that would never get struck by lightning?" What technology level? In the far future, you could handwave the ability to make "neutronium". $\endgroup$
    – RonJohn
    Jul 21, 2023 at 0:41
  • 5
    $\begingroup$ In the rain, no matter what the material of the mast, the mast will be covered in rain. And rain is not pure water, it includes enough other stuff to be conductive. And any particulates that have settled on the mast before the rain will likely add to its external conductivity. Consequently, using something like a lightning rod to direct the lightning safely is probably going to be more effective than just building a non-conductive mast. (At least, without adding a certain amount of handwavium. 😄) $\endgroup$ Jul 21, 2023 at 17:29
  • 1
    $\begingroup$ @AlexP make your initial comment an answer please :) $\endgroup$
    – Shalvenay
    Jul 23, 2023 at 13:59

5 Answers 5

21
$\begingroup$

It's not the material per se which makes it lightning proof, but rather what's around it.

When a difference of potential starts building up, sooner or later it will cause a discharge and produce the lightning.

The discharge happens at the point which offers the least resistance to the discharge current flow. Therefore in a world made of gold, a wooden stick is almost sure to never get a lightning (unless it gets close enough to the other pole...).

Even in a world made of vacuum and only your perfect pole, a lightning would happen, because you can't store infinite energy in a finite volume.

$\endgroup$
3
  • 1
    $\begingroup$ In other words, if the electric field is strong enough it can tear electrons out of any material through the vacuum. $\endgroup$
    – DKNguyen
    Jul 20, 2023 at 19:01
  • $\begingroup$ Let's just say the lightning in a vacuum would be extremely rare, but also extremely deadly. Most likely cataclysmic level of destruction every time it happens. $\endgroup$
    – Nelson
    Jul 21, 2023 at 0:32
  • $\begingroup$ I mean, you can't have traditional lightning in a vacuum anyway, because any atmosphere that would generate an electrical charge would fall into the space occupied by the vacuum. $\endgroup$ Aug 1, 2023 at 20:09
8
$\begingroup$

I think there are two main physics principles to consider.

  1. The conductivity of the material. Typical sailing masts are wood, which is generally considered an insulator. However we know that lightning will hit trees and wooden masts. Electrical potential is a lot like water pressure in some ways. Normally glass stops water (like wood stops electricity), but at firehose pressures water breaks through. If the potential is high enough, an arc will go from the clouds to the ground.

  2. The geometry of the mast. Charges build up on the surfaces of objects, and the tighter the curvature of the surface, the more charge density you can get. (I am using a lot of improper terms here because its been a while since I studied electrical engineering.) So if you have a sphere, the charges will be spread around the surface pretty evenly. If you have a spiky ball, the spike tips will be more strongly charged than the sides of the spikes. The places of high charge density are more likely to arc. In the case of a ship, the mast is a really big spike. On the ground, trees are big spikes.

So, I think the best you can do is 1) use smoother, less spiky geometry where you can, and 2) make a lightning rod that is spikier than the mast.

$\endgroup$
4
  • $\begingroup$ just out of interest: A hollow wooden circle in which you hang the sail would be more 'resistant'. But because it is still the most outward part of the ship it would get hit (?). learned something today! $\endgroup$ Jul 20, 2023 at 18:21
  • 5
    $\begingroup$ Exposed wood really isn't a very good insulator. The conductivity can be measured with a multimeter and a couple of nails. It's actually one way the moisture content is assessed. Salt water (sea spray) is more conductive than pure water, and lightning does tend to come with rain. So at least the outer layer of the mast will be wet wood, possibly salty, and therefore quite conductive. $\endgroup$
    – Chris H
    Jul 21, 2023 at 10:37
  • 1
    $\begingroup$ "Typical sailing masts are wood" --> In 2023? I have seen few wood masts made after 1970s - at least in this world. $\endgroup$ Jul 21, 2023 at 12:05
  • 1
    $\begingroup$ I assumed we were in a pre-steam environment since we were sailing. Obviously sailing is still a thing with new materials. My bad. $\endgroup$
    – Atog
    Jul 21, 2023 at 16:13
4
$\begingroup$

Make your whole ship out of a resistor

Sure, you could go the boring, so-called "practical" route (yech) of installing a lightning rod. But why do that when you could instead make your entire ship out of paraffin wax, fused quartz, PET, or Teflon? Sure to turn heads, and a great conversation-starter!

You see, lightning takes the path of least resistance to the ground or water. Steel, aluminum, and wood are better conductors than air, which is why lightning prefers to travel through those when it can, rather than through the air. So all you have to do is make your mast (and, for good measure, the rest of your ship) out of something with a higher resistivity than air. Lightning will take one sideways look at your plastic ship and go the long way around.

This table tells us that air has a resistivity of 1.3×10^16 to 3.3×10^16 Ω m. Selected entries from the table:

Aluminum            2.82×10^−8
Titanium            4.20×10−7
Stainless steel     6.9×10^−7
Wood (damp)         1×10^3 to 4
Wood (oven dry)     1×10^14 to 10^16
Air                 1.3×10^16 to 3.3×10^16
Paraffin wax        1×10^17
Fused quartz        7.5×10^17
PET                 10×10^20
Teflon              10×10^22 to 10×10^24
$\endgroup$
13
  • 3
    $\begingroup$ Making ships out of paraffin wax, fused quartz, PET and Teflon is... more than a bit impractical. $\endgroup$
    – RonJohn
    Jul 21, 2023 at 0:13
  • $\begingroup$ @RonJohn Fascinating $\endgroup$
    – causative
    Jul 21, 2023 at 0:19
  • 2
    $\begingroup$ @RonJohn Not if there's an air path to take. Teflon has 100,000x more resistivity than air, so it will receive 1/100,000 of the current if the circuit has an equal volume of Teflon or air. Also, the development of a lightning bolt iteratively ionizes the air along the path that already had the most current, so it is a "winner take all" scenario. If the Teflon had 1/100,000th of the current as the bolt began to form, it wouldn't be the "winner" so it would end up with much less than 1/100,000th of the current by the time the bolt fully forms. The main bolt would just go around it $\endgroup$
    – causative
    Jul 21, 2023 at 0:44
  • 1
    $\begingroup$ @RonJohn Artificially applied voltage in a tube is not lightning. We're talking about a boat. $\endgroup$
    – causative
    Jul 21, 2023 at 0:58
  • 2
    $\begingroup$ @worldbuilder Hey, did I say it would be smart? Did I say it was seaworthy? No! I said lightning wouldn't strike it. You get what you ordered, pal. $\endgroup$
    – causative
    Jul 21, 2023 at 15:57
4
$\begingroup$

No, yes, kinda...

If the potential difference between two ends of a length of material is great enough, it will conduct electricity. It doesn't matter what it is. However, the nature of the material may be that it melts, burns, or explodes when that happens. So when you ask the question, "is there a material lightning does not strike?" the simple answer is "no."

However, you can't always control what's around the object. In other words, if the base of your ship's mast is made of metal and for some weird reason that metal extends through the ship to touch the water below, the metal at the base of the mast becomes a great place for lightning to strike and topple the mast.

Except! Your ship is on an ocean of water and pretty much anywhere is a better place for lightning to strike than the ship, itself. It's a common misconception that altitude alone makes something significantly more susceptible to a lightning strike. That's true only if there's a better conductor to ground than every where else. Thus, a wet tree in a rain storm is a little closer to the potential discharge than the surrounding grass and is therefore more likely to be hit.

But change that to a tree on a 10 square-meter island in the middle of a massive lake and the odds of that tree being hit drop tremendously because the surrounding water represents a better conductor than any amount of water on the tree.

Keep in mind that lightning striking the masts of sailing ships are kinda uncommon. Modern statistics say the odds are four out of every thousand strikes during rough weather. Those are low odds. But as the linked article explains, it's still valuable to do something to mitigate the effects.

In other words, you don't want to try to make your mast a better insulator, you want to do something to make your mast a better conductor, so when the lightning does strike it goes exactly where you want it to and discharges in a much safer manner.

But if you insist that you want a better insulator, avoid rainy weather. It's the only way to solve the problem. Water is a more than satisfactory conductor.

$\endgroup$
2
  • 1
    $\begingroup$ I was looking this up and lightning strikes on boats are extremely common, far more than on land. In fact, especially on the east coast, electrical damage from boats getting struck by lightning is common, 1 in 10,000. Moreover, the statistically highest chance of getting struck by lightning is on a sailboat, which interestingly is 4x more likely to get struck than a pontoon boat. $\endgroup$ Jul 21, 2023 at 10:42
  • 1
    $\begingroup$ @worldbuilder Sailboats typically have deep keel into the water. Pontoon boats typically have a significantly shallower draft and usually nothing deep or pointy under the water. $\endgroup$
    – David S
    Jul 21, 2023 at 15:00
4
$\begingroup$

Another alternative is keep your mast metal, but make it actively charged via Van de Graaf electrostatic generator or similar.

The lightening happens because electrostatic potential levels of clouds and ground (or sea) are different. When that difference (i.e. voltage) becomes high enough, even the things that are usually not conductive become so due to dielectric breakdown, and electricity flows from one potential level to the other, until they equalize.

As other say, which path is preferred depends on its conductivity, and solutions offered so far focus on reducing that aspect.

However, another alternative is making your mast at the same charge as the clouds. That way it won't be interesting target for the lightening which wants to reach opposite polarity charge (just like the lightning that has started from cloud potential towards ground potential does not decide "ok let's get back to the same place in cloud where I started" - there is no reason why it would go back to the same electrostatic potential).

Of course, it would use energy, and you must watch you do not overcharge it, as otherwise you could create your own lightning from your mast to the sea (even in the absence of the storm outside).

$\endgroup$
2
  • $\begingroup$ Do you think there is a systematic and automated way to do this? I like the idea of matching the electrical potential with that of the clouds, although I'm not sure this is realistic to do $\endgroup$ Jul 26, 2023 at 12:49
  • $\begingroup$ you could check electrostatic potential of the sea, and charge in opposing direction. Still, it is worldbuilding material idea, not "let's patent it and make a bestseller yacht product" (in reality, it is cheapest and safest to use real-world protection methods where you want the lightning to struct your arrester - but it does not seem to fit your worldbuilding theme) $\endgroup$ Jul 26, 2023 at 14:43

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .