Salt water conducts electricity, so why are seafaring objects unharmed when lightning strikes water?

Question

Salt dissociates in water and the solution is then able to conduct electricity (ions). So whenever there is a storm at sea, if the lightning strikes water, how come the electric current doesnt travel up, for example, a cruise ship since it is metal, and shock ppl on board?
--fresh water doesnt conduct elect.

Answer 1

Maybe it has something to do with grounding. If a ship is in the ocean and not touch anything then there is no reason for the current to go up right?

Answer 2

This question came up previously. The short answer is, objects are not unharmed if they are in the lethal zone. A back of the envelope calculation would say that if you were swimming along, you probably don't want to be closer than 3 m to the actual strike point. Also, there are many instances of seafarers getting zapped by having broken or not sufficient grounding on there boats. The cruise ship is not a good example, since it is grounded, and has metal all over. However, if you were swimming in the pool on the aft fantail, and conditions were just right.... These scenarios require that you are part of the 'path of least resistance', between the sky above and the sea below.

In review, once a strike happens, the charge density reduced to very low levels a short distance from the strike point. Case closed. Oh, except the misnomer about fresh water. It still conducts electricity, just has a high resistance. So, remember if you are in fresh water, the lightning will pick you as a path first if you're in the way...

Answer 3

Well there are two things at work here. First off some of the current probably does travel up the ship. However even if it did hit the ship it probably would not affect the people all that much. Even 'ground currents' (the area on land around which lightning strikes) are only deadly for a couple of yards.

Also the current density coursing through the ship wouldn't be that great unless the lightning strike was right next to the ship. The closed loop would likely not contain your body as it is of high impedance.

Answer 4

Seafaring objects can be harmed by lightning. A man in the rigging of a ship can be killed. The electronics on a boat can be fried.

The way to keep these things from happening is to make sure that there are easy paths of electrical flow from high in the ship to the water.

Extremely sensitive electronics can be shielded or insulated from the surrounding boat and only connect to other systems through wires and circuits that will automatically cut out when there is a power surge.

Now, for you example of lightning hitting the water. The electricity wants to spread out and get the individual electrons way from one another. Once the lightning hits the water, it is easier to just spread out in the water than to travel up into the ship.

Answer 5

Well, in fact the charged clouds can and do make charge flow through the conduting water into the ship. But its a static charge - no current flows.

So the conductivity of the water means you have charged clouds over a charged sheet - the perfect conditions to create a coronal plasma discharge - a pale blue glow around pointy objects such as masts. When this happens it is called St Elmo's Fire.

When lightning does strike the water a current does flow, but it is rapidly conducted away by the water and causes no real harm.

Answer 6

Look at the surface area of the sea in question. It's like asking why a man in the desert can't feel a grain of sand dropped 2 miles away. Lightning hitting water would dissipate over a wide area and wouldn't have enough force behind it to hurt anything beyond a very small area....

Answer 7

There's no reason for the lighting to travel through you. Lighting is most dangerous when it strikes something that doesn't conduct well near you. The shock is caused by a difference in potential between two parts of your body. If you're in seawater the difference in potential between a point 5 feet from the strike and 6 ft from the strike is very small. If you're standing in freshwater, the difference is much larger and you get shocked.

Answer 8

electricity takes the path of least resistance to ground

for lightning striking a point on a marine body, the electrolytic solution is an efficient conductor having an exceedingly great cross-sectional area

while submarine objects (including, but not limited to, organisms) local to the strike could be injured, deepwater objects should be immune on account of dissipation of the electrical charge

"local" is a relative term, depending for its definition on how conductive are the objects proximate to the strike -- for instance, the steel lower hull of a hypothetical unpainted cruise vessel at sea would conduct electricity better than the flesh of a surfaced whale -- meaning it would be less invulnerable (this ignores the effect of the lightning on the whale's nervous system)

however, cruise vessels are painted and great attention is paid to mitigation of electrolytic forces that would otherwise cause accelerated degradation of the hull -- so, in layman's terms, cruise vessels are not electrically conductive with respect to the marine environment, because they are electrically insulated by their paint (and otherwise "bonded" to the marine environment)

the path of the electricity wouldn't shock the people, because they are never between the source of the charge and the electrical ground

Answer 9

Ships are grounded to the sea. Lightening passes straight through the ship. If not properly grounded, a direct hit can cause much damage to electronics and bonded metal connections.

Answer 10

The sea us so big, that the electricity is distributed over a very large area, and its strength then becomes negligible.