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I was answering this question about how a living planet-organism could be possible, and realized I didn't know how such a planet-organism could produce a magnetic field. I postulated that it could somehow use revolving magnets, but this seemed weak and difficult to imagine in reality. So this brings me too my question: how could a living organism generate a magnetic field? For this question, we're assuming earth-like biology, except for the magnetic field thing.

And for bonus points: if the organism was scaled up to planet sized (ignore the other problems with this happening), would that magnetic field be able to hold off solar wind?

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We already do generate magnetic fields. Pretty much all matter does. Electromagnetism is what makes matter behave the way we expect matter to behave.

We also generate electrical currents, which produce electromagnetic fields.

The former could be increased by containing large quantities of suitably arranged and magnetized ferromagnetic materials; A life form with permanent magnets embedded in it. The latter could also be increased by producing larger electrical currents, and by arranging them in suitable circuits (coils for instance) to produce electromagnets.

Biological electrical currents are generally short pulses rather than sustained so biological electromagnets would be similar pulses. A biological sustained electromagnet would require a rather different process, probably like a refuelable battery or fuel cell fed by biological chemical sources.

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Your question relates to the DC Comic Character Mogo, Since he has the internals to absorb energy, one would assume that he can control the flow of electrons.

Here is an explanation of how the earth generates its field: source physics.org

The Earth's inner iron core is molten, and spins to the rotation of the earth. This flow of liquid iron generates electric currents, which in turn produce magnetic fields. Charged metals passing through these fields go on to create electric currents of their own, and so the cycle continues. This self-sustaining loop is known as the geodynamo.

I would imagine, the Mogo would induce the same geodynamo effect by routing the current around his body thereby creating an electromagnet.

The electric eel gives support to this biological capability,

The electric eel generates large electric currents by way of a highly specialized nervous system that has the capacity to synchronize the activity of disc-shaped, electricity-producing cells packed into a specialized electric organ

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To make a planet sized organism generate a continuous magnetic current strong enough to repel the solar wind, embedded permanent magnets would be entirely unsuitable - It would take a large planetoid's worth of magnesium or neodymium to generate a field strong enough, and be difficult to alter that field in response to stimuli or threat. In addition, that would likely be a small, strong magnetic field that only extends a few miles above ground and pulls the iron out of blood - a large, diffuse one is better suited to protection from solar wind.

The way we humans, the electric eel, or other earth-evolved biological life generate electricity would be much more responsive - and presumably a planet sized entity could have an enormous nervous system generating a potentially significant electromagnetic field (if it's brain is anything like ours). That said, thinking demands an enormous amount of energy (your brain makes up ~2% of your body mass, but accounts for ~20-25% of your caloric expenditure) and generating electric current just for the sake of it is even more energy intensive. In short, it's a massively inefficient process that would take a crazy amount of energy to maintain, not well suited for a planet's magnetic field.

What I'd propose is something combining the best of both worlds - a massive 'circulatory system' that contains a highly compressed, nonreactive liquid filled with iron particulate - basically a thick sludge of fine iron filings and mineral oil. This circulatory system would be composed of 10-50km wide tubes, deep under the planet's surface, powered by an absolutely enormous biological pump. In the same way that an inorganic planet's magnetic field was generated by the movement of a massive iron core, this living planet would generate a magnetic field similar to a spinning iron core - the right size/strength to repel solar wind, unlike permanent magnets, and less energy intensive (by virtue of the circulating fluid's huge inertia and a well designed circulatory system) and continuous, unlike a biological field.

In addition, since it was powered by an enormous circulatory system, the planet could alter or reroute the flow of liquid through ring/coil shaped capillaries in it's 'skin' nearer the surface, inducing local magnetic fields to, say, crash an escaping spacecraft or scramble non-hardened electronics.

Hell, it could even decide to pause pumping this magnetic fluid altogether for a period of time to sterilize life on it's surface, or majorly alter the path of circulation to change it's spin/move it's axis of rotation (resulting in anything from objects on the surface flying off into vacuum if it abruptly slowed surface spin to instant seasonal change winter->summer if it altered it's axis).

That solves your magnetic field issue, gives you a ton of optional devices for your planet to take an active role in the progression your story, and you'd get the cool factor of being able to legitimately talk about the planet's 'heart'.

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  • $\begingroup$ The magnetosomes used by magnetotactic bacteria could be a carrier for the iron particulate. If the organism already uses blood, maybe you could modify such bacteria into an organelle carried in some of the blood cells. $\endgroup$ – Pastychomper thanks Monica Dec 2 '19 at 13:30
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A living planet is generating a magnetic field already. Earth is a living planet and the movement of liquid iron magma inside of its crust creates magnetic energy that coalesce into the strong magnetic currents that create the aurora borealis and Earths protective shied.

I can see how a fictional planet that has "intelligent" thought and was living as a person or A.I could control the flow of it's iron magma and create magnetic partitions to shield itself from attack in specific places. It may even be able to focus some of the liquid molten iron magma in bursts creating pulses of magnetic waves as weapons or communication disruption or as a source of energy bursts for travel.

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  • $\begingroup$ Not a planet with life on it, but a planet that looks like an organism. i.e. has cells, a heart, and other important organs. If you believe that earth is a living organism, ok, but I'm not going to count that for this question. $\endgroup$ – DonyorM Oct 19 '14 at 10:51
  • $\begingroup$ Chris' answer should stand as correct -- whether or not the Earth has individual bits living on it or those bits were united into a single organism, the chemicals at its core could be the same as those at the core of Earth today. We have iron in our blood that circulates... the living Earth has a big blog of iron that circulates... we create a tiny magnetic field... Earth creates a much bigger one. $\endgroup$ – SRM Nov 27 '19 at 22:43
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Electromagnets operate simply by running a current through a coil. Nerves create, albeit very small, current by transferring ions across synapses. The ionic charge of one cell, thus gets transferred to other cells via ion transfer across the gaps between receptors on either side of synapses. So it's not exactly a continuous current, but it's also not completely discrete, but rather pulsed. I'm not a biologist, or an electrical engineer, but I assume that these constraints are not an issue when it comes to large scales. For example, I know that a root mean square law applies to determining the usable power available from an alternating current source. Something similar likely applies to long nerve networks. So if these nerves were arranged in large-enough coiled structures, then the nerve pulses themselves could not only transfer relevant biological signals ( whether autonomic, locomotive or information processing ) but could serve a dual purpose of generating a considerable magnetic field for a planetoid life form. Evolutionarily, serving a dual purpose makes sense as life can be seen as an experiment in optimizing the utilization of metabolic processes to maximize survival and continuation of the species.

Beyond a general notion of how this can be done, I'll leave the hard engineering problems to more knowledgeable participants. Feel free to make edits.

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I would genetically engineer some giant long organ with a unusually high concentration of voltage-gated ion channels akin to an electric eel.

These organs are made of electrocytes, lined up so a current of ions can flow through them and stacked so each one adds to a potential difference.

Just stack up these organs in a line to create some directed field.

To be fair, this qualifies as "living" but is more like a bio machine.

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