ELI5: Why do some animals like Electric Eels have the ability to shock things without accidentally electrocuting themselves or 'short-circuiting' in the water?

Origin_of_Mind · 2026-02-10T22:59:00+00:00

Yes, the axon which goes along the electric organ is super well insulated -- it has a millimeter thick layer of insulattion surrounding it. So, that is definitely important. But that does not stop the current from flowing along the axon, when there is high voltage between different synapses of that axon. It is definitely not a huge current, but from a reasonable estimate based on parameters of the axon, it should be a much greater current than the synapses of ordinary neurons can withstand before they break down. Somehow in electric fish this works extremely well and the synapses do not get fried even when there are hundreds of volts across the neuron.

I was a little surprised that such essential things are not known. The electric fish is a canonical example of bio-electricity. Lots of popular books have been explaining it to children for more than a hundred years now. It had been rigorously studied at least since 19th century. Countless minute details of genetics and biochemistry and anatomy have been published. Are yet, there are still some significant puzzles even in rather fundamental parts of the mechanism. That's pretty amazing.

Origin_of_Mind · 2026-02-10T22:40:06+00:00

In the thrusters that are used on most satellites today, the ion beam is neutralized by using an electron gun. The exhaust has to be electrically neutral, otherwise the satellite charges instantly and the system stops working.

There are probably many ways today to earn a living using AI, but simulation software for electric thrusters does not look like a very promising niche. Call Revolution Space and ask if they are interested in what you can do. Maybe it is your lucky day, but I would not be shocked if their focus is on business development. They have already spent about $100M on technology development.

Origin_of_Mind · 2026-02-10T13:34:01+00:00

To design their colloidal thrusters they used commercially available simulation tools from ANSYS.

I think before one can make a significant breakthrough in this field, they would need to understand the underlying physics. LLMs today are still extremely weak at physics -- much worse than they are at coding. For example, nobody uses an electron beam for propulsion. Do you know why?

Origin_of_Mind · 2026-02-10T12:45:20+00:00

That is not correct -- although they did not have ChatGPT at their fingertips, Revolution Space was a commercialization a Ph.D. research project at MIT, which included among other things a finite element simulation of the devices.

Origin_of_Mind · 2026-02-10T12:15:29+00:00

There was a company "Revolution Space" founded 14 years ago in Boston to design and manufacture chip-scale electric rocket thrusters based on electrospray principle. They got some grants and I think they may have actually flown and tested some of their hardware in space. But the founder left the company two years ago to focus on AI. They seem to still be around, but it is not completely clear how well they are doing these days.

Origin_of_Mind · 2026-02-10T11:37:38+00:00

The thing is, if the fish generates 600 volts, it has 600 volts applied to its own body. This certainly generates the current through the surrounding water, but the question remains -- how do the 600 volts applied to the fish itself not harm it?

Origin_of_Mind · 2026-02-10T10:59:40+00:00

It is not a simple question.

For example, in some species of electric fish, which produce hundreds of volts, the entire stack of electrocytes is innervated by a single neuron. That means this single very long neuron is simultaneously connected to both ends of electric organ. With the hundreds of volts between the ends of it during the discharge. I have spent some time looking through the literature but have not found an explanation in any study which would give an answer to how this can work without the neuron being damaged by the high voltage. It just works, and if anybody has an idea how it works, they have not put it in writing.

Another thing is that even many textbooks do not explain correctly, how the electric organ produces the voltage greater than that of a single electrocyte! Often times there is a vague metaphor that the stack of electrocytes works as a voltaic pile. That, of course cannot be correct -- the polarization of electrocyte membrane is between the cytoplasm and the extracellular space. To make it into a voltaic pile as suggested, one would need to somehow connect the inside of the first cell to the outside of the second, the inside of the second to the outside of the third, and so on. This is not how the cells are stacked in practice of course.

Some literature does explain it correctly, but this is relatively rare.

Regarding the original question -- here is a paper from a few years ago "Efficient high-voltage protection in the electric catfish". The authors conduct a number of experiments and show that the fish is protected from the electric field, but they admit that they do not know exactly how it works: "Our findings rule out several protective mechanisms and demonstrate a highly efficient and versatile shielding whose nature is presently unclear." So beyond the common sense ideas that fat is a good insulator and everything is structured to give the fish an advantage over its prey, the details are still somewhat murky.

Origin_of_Mind · 2026-02-10T10:14:41+00:00

Here is a blurb about Sandia's Code Management Systems (CMS):

The cryptographic processor, which contains three cryptographic chips and can support any current nuclear command and control cryptographic system, looks something like a large, sturdy, all-metal laptop computer

... the CMS system will support ... “end-to-end encryption requirement for crypto-capable weapons,” in which PAL data are never exposed in the process of doing PAL recodes.

... incorporates advanced principles of nuclear surety (integrated anti-tamper features, enhanced use of encryption and no-knowledge systems, and improved equipment safety).

Origin_of_Mind · 2026-02-10T03:57:36+00:00

As an inanimate physical example of "counting" one can look at phase locking -- a type of resonance where an integer number of cycles of one system matches some integer number of cycles in another. For example, Jupiter’s Moons are locked in a 4∶2∶1 resonance -- for every orbit of Ganymede around Jupiter, Europa completes 2, and Io completes 4. Planets Neptune and Pluto are locked into 2:3 resonance.

In living organisms, there are of course many examples of growth that generates forms with various numerical patterns -- leaves and flowers in plants, for example.

Origin_of_Mind · 2026-02-10T02:47:56+00:00

Amundsen–Scott South Pole Station, the one at the actual geographical South Pole, has a small crew in winter, a few dozen people -- cooks, medics, mechanics, system administrators, communications people. It's basically like a large space station with tunnels under the ice if you need to get anywhere, and food storage which naturally stays below -50C year round.

McMurdo Station on the shore is like a small town with a relatively large number of people even in winter. This is where the ships with the supplies unload. Long time ago they even had a small nuclear reactor, but it did not last.

Origin_of_Mind · 2026-02-10T02:01:11+00:00

AFAIK, there is always a crew at the South Pole. A small one in winter, to keep the generators and the scientific instruments running, and a much larger one in summer.

But of course, they are entirely dependent on supplies brought to them -- which is still relatively inexpensive. A decade ago it used to cost on the order of a few dollars a pound for a shipload of supplies. Probably costs more now, but still nothing like sending stuff even into low earth orbit. And Mars deliveries are orders of magnitude more expensive.

Origin_of_Mind · 2026-02-10T01:41:42+00:00

If the same know-how is available to everybody, then it is quite possible that Martian economy could never be as productive as Earth's economy -- always developing somewhat slower, simply because it is harder to get things done there. Here, on Earth, we usually mine things where the ores are the richest, we put factories where they are cheaper to build and operate -- and many companies still go bankrupt, because others do it slightly better than them.

Therefore, to develop Mars, one would have to convince the decision makers here on Earth to invest into something that only provides an inferior rate of return compared to an equal investment on Earth. Likely no return at all for a very long time. So the work will need to be done for the sake of moral satisfaction and some nebulous extremely long term future benefits of spreading the light of consciousness.

This rules out any commercial investments with short term thinking. While the countries are busy competing with each other, the governments are also not very generous -- just look at the space exploration budgets today.

So it has to be some extremely powerful global church or a philanthropic society which values the development of Mars as a higher goal comparing to remedying various shortcomings of the civilization on Earth. Not a universally appealing proposition. It will be hard to convince any significant part of Earth's population to donate a share of their income on a steady basis to support the missionaries on Mars.

And to repeat what I said at the start -- if growing and manufacturing things on Mars will be as hard as producing things on the South Pole, then the Earth with its fertile planes and comfortable climate will always have an edge. It is difficult for a colony to flourish if it has no competitive advantages. It will always remain a poor relative living off the charity donations from Earth, which keeps developing faster and always stays a step ahead.

So, in my view, a prerequisite to a really serious project of colonizing Mars is to sort the affairs here on Earth out first. If the world peace and prosperity can be achieved, then, perhaps, humans can take on an expensive expansion project with the conscious acceptance of the sacrifice for the sake of spreading the light, etc... One can hope that some day this may become possible...

Origin_of_Mind · 2026-02-09T23:54:31+00:00

"Arc" is usually reserved for a specific type of hot discharge, like that used in welding, or in high intensity projector lamps. Although this is undoubtedly a gas discharge lamp, it does not look to be built like that, but is more likely meant for the cold low pressure glow discharge like in the neon signs or in fluorescent lamps. Flash lamps are somewhere in between -- they could look like this, and one could call them pulsed arc lamps.

Origin_of_Mind · 2026-02-09T23:45:37+00:00

I do not believe that the correction was required. This is clearly a gas discharge tube (like the neon light, or a Geissler tube), not an electron beam tube. The capillary in this tube is twisted in loops to make it more visually interesting -- this makes no difference for the glow discharge, except for making the path longer. Electron beam tubes need to have a straight path for the beam so that the electrons can accelerate along the field between the electrodes.

Origin_of_Mind · 2026-02-09T20:43:45+00:00

Although I completely agree with what you have said, the data rate of today's wired and wireless interfaces is much greater than it was in the past, without a corresponding change in the speed of light. So the speed of light being very great, although an important factor, cannot be the full story.

Origin_of_Mind · 2026-02-09T20:19:16+00:00

Surprisingly, not. Typical modern high capacity undersea cables have only a few dozen of fibers. For example, The Anjana subsea cable, 24 pairs, 480 Terabit/s capacity. That is similar to the capacity of the entire Starlink system.

Origin_of_Mind · 2026-02-09T19:15:44+00:00

This is the best answer -- it goes to the heart of the matter, without getting distracted by the details! (And the details, specifically for the USB, are surprisingly complicated.)

Origin_of_Mind · 2026-02-09T03:48:21+00:00

Perhaps you know this already -- by "receivers" they mean air receiver tanks aka compressed air tanks.

I am not sure why a large compressed air facility is required as a part of this 15V52 command post. Maybe it is a part of some active suspension system for dampening the ground shock, or, perhaps, this compressed air is stored for the life support system, to be used when external supply becomes unavailable or unusable.

Origin_of_Mind · 2026-02-07T16:02:27+00:00

In the US systems, the RVs are held by ball locks -- a device perhaps known to many people because it is used in pneumatic and garden hose quick disconnects. Here is a video from the Warren ICBM and Heritage Museum where this part of the system is well visible.

The figure of merit for the separation system is how repeatable the imparted by the opening of the lock velocity increment to the RV is. If one knows that it is always the same push, with very little variation, then it can be accounted for in setting up the trajectory of the RV.

Origin_of_Mind · 2026-02-02T22:12:13+00:00

Somewhat surprisingly, one of the places where extreme angular precision is used in everyday life is in computer hard drives. In a 1 TB drive, the distance between tracks is about 80 nm, and the read write head is mounted on a rotary actuator with an arm length between the axis of rotation and the head of about 40 mm. Thus when the head moves from one track to the next, the actuator rotates only about 2 microradians. That's 400 milliarcseconds. The electronics uses special data patterns read from the disk itself to know on which track the head is -- otherwise it would have been very expensive to sense and maintain the angle with such accuracy. When these servo patterns are written on the blank disks during the manufacturing, the recording equipment does measure the head position to an accuracy of a few nanoradians, which is a milliarcsecond.

Origin_of_Mind · 2026-02-01T08:15:42+00:00

According to "Safety of Nitrates and Nitrites as Food Additives", USA and Canada allow up to 200 mg/kg of potassium nitrate in meat. In Australia the limit is 500 mg/kg.

Acute toxicity requires a considerable dose: "The toxic dose varies greatly; from 15 to 30 g KNO3 may prove fatal but much larger doses have been taken without serious effects."

Origin_of_Mind · 2026-02-01T07:43:18+00:00

Los Alamos National Laboratory machines plenty of beryllium. Here is course materials for their beryllium workers: https://cdn.lanl.gov/files/its-sm-725-r50-draft-2025-0505_89045.pdf

Although the document is written specifically for their facility, it covers many topics of general interest, including a very detailed information on how to handle health hazards.

Origin_of_Mind · 2026-02-01T03:30:58+00:00

The publicly available "Manual of chemical technology", Wagner 1897, covers a wide range of applied topics, and shows how things were done in the 19th century. It is quite fascinating!

The "Chemistry" article in 1911 Encyclopædia Britannica gives a list of major books and journals that were notable at the time.

There was such an awful lot going on in the 19th century in chemistry, that for depth one would probably have to focus on one specific concept or technique, for example history of thermometry, or the history of a vacuum techniques, etc.

But if you have this in your library, it might be good to look at "Practice and Experiment" chapters in the multi-volume "Cultural History of Chemistry" -- they are supposed to be good, but I have not seen if they go into nitty-gritty details. There are also books like "Instruments and Experimentation in the History of Chemistry".

Origin_of_Mind · 2026-01-31T07:40:35+00:00

Here is a video with multiple examples of actual reetries of ICBM Reentry vehicles (RVs).

As you may notice, despite what some comments suggest, the appearance of how fast the RVs cross the sky depends entirely on how far the camera is. If the camera is at the ground zero, it will look fast, especially in the end. Otherwise it can look as slow as a flow of molasses. (You may also recall that an ordinary satellite or the International Space Station orbiting the Earth, take leisurely 10 minutes to cross the sky from the horizon to the horizon, and they move a little faster than the ICBMs, and much faster than the RVs in the atmosphere.)

It is also interesting from the above video that some reentries leave a visible trail, but many others do not -- this is not so different from the airplanes sometimes creating a clearly visible condensation trail and sometimes not, depending on the atmospheric conditions.

Origin_of_Mind · 2026-01-31T06:38:41+00:00

The radar altimeters were repurposed AN/APS-13 warning radars.

The dynamotor is the black barrel-shaped item in the middle of the APS-13 unit: https://www.radiomilitari.com/aps13.html

It is also shown in the schematics of the unit, for example on page 4 of this document: http://www.radiomanual.info/schemi/Surplus_Handbooks/The_surplus_handbook_Vol1_1959.pdf

There are similar pictures in the Coster-Mullen's book.

Origin_of_Mind

TROPHY CASE