I'm trying to make an alt-history in which electronics are constantly effected by higher-than-normal background magnetic effects - think a constant geomagnetic storm, except not necessarily caused by the Sun. The idea is to cause several changes regarding technology:

  • power grids are generally either heavily shielded or highly localized (to the point that neighborhoods often have their own power plants [chronologically: wood/coal, then oil, then fission or solar, then fusion], because it's less expensive then running a heavily-shielded/redundant cable to them from a far-off power plant), because big grids form conducting loops when subject strong magnetic field changes

  • the telegraph was never really a thing; they went straight from horse messengers to radio

  • satellites, spacecraft, and anything that leaves the atmosphere has to be heavily shielded; cell coverage, GPS, Internet, and the like are provided by things that are so large they could be space stations

  • ICBMs and strategic nuclear warfare via missile technology don't really work, because if they leave the atmosphere the circuits get messed up, and shielding them means that they're incredibly heavy; instead, nuclear war is conducted via massive conventional artillery and air-breathing cruise missiles, and has actually occurred on several occasions because mutually assured destruction is a lot harder when it's so easy to shoot down cruise missiles and bomb big artillery emplacements

  • solar power satellites (heavily shielded, of course) are a major research objective, so that neighborhoods, large buildings, and the like don't need to rely on their own power plants

I'm personally targeting a constant -1000 nanotesla (relative to IRL) reduction in Earth's horizontal magnetic field. Is there anything that could plausibly do this, such as stronger solar wind, a constant, low-level coronal mass ejection, or a reduction in the Earth's magnetic field?

To be clear, this is not a question of:

  • "how can humanity do this" (it's intended to have been around since the beginning of the Solar System - not something man-made)

  • "is this possible" (geomagnetic storms have caused similar such disruptions in the past)

  • "what would the effects of this be on life/civilization (I'm going to ask that later, and I've already thought of a few reasons, as you can see above)

  • $\begingroup$ Can we go so far as alternate-earth? Can we make the sun a binary with a small pulsar or change the moon to have a whomping magnetic field such that its orbit around the planet would cause disruptions? Can we change the core to be non-homogeneous in a way that causes the Earth' magnetic field to go skewampus? What's our limit? $\endgroup$
    – JBH
    Aug 1, 2021 at 2:34
  • $\begingroup$ Or maybe something like this (Huge rogue 'planet' has magnetic field scientists can't explain), only it's in our system and close enough to annually shut everything down as it passes close by? Are these kinds of changes out of scope? $\endgroup$
    – JBH
    Aug 1, 2021 at 2:36
  • $\begingroup$ @JBH I'm trying to make this as close to the IRL solar system as possible, so no. $\endgroup$
    Aug 1, 2021 at 3:06
  • $\begingroup$ Just to be sure I'm clear, you want a constant global magnetic disturbance, but it can't be man-made. It could be caused by the sun, but isn't restricted to that - but we can't actually change the solar system to do it.... This is another one of those "let me set your expectations for you" moments. $\endgroup$
    – JBH
    Aug 1, 2021 at 3:15

2 Answers 2


Decades ago, Earth captured a large comet with just the right properties. If you're willing to hand-wave a little bit, I think this could achieve many of the effects you want, in at least a semi-plausible way.

  • The plasma in the comet's tail contains enough charged particles to interfere with Earth's magnetosphere. Every time Earth passes through the tail, a geomagnetic storm is created. Furthermore, the large influx of charged particles fuels the storm directly. The effects would be similar to a CME, but more concentrated at Earth.
  • The plasma from the comet also supercharges the Van Allen radiation belts. Aside from making space travel difficult, this strengthens Earth's ring current (which acts to resist the planetary magnetic field) and further worsens the geomagnetic storms.
  • The comet will evaporate eventually, of course. However, Earth is far enough from the Sun that full evaporation could take many years if you make the comet large enough and select the right composition.
  • You can decide what type of magnetic effects you want. Perhaps the comet orbits the Earth every few hours or every few days, causing geomagnetic storms on a regular schedule. Or perhaps it is still breaking up into smaller chunks that cause less periodic damage.
  • As a bonus, you get frequent, spectacular auroras and a very visible comet in the sky.

Two types of event could cause some of the effects you want but at the same time they would also render some e of your desired changes in technology impracticable. (And the effects would not be permanent.)

  1. A CME event; (as already mentioned). A large (powerful) enough impact would have some of the effects you required but its important to remember that while quite common the Sun ejects CME'se in random directions and the chances of any one impact hitting Earth is very small. Remembering that as a target the Earth is less than 13,000 K in diameter and orbits the sun at 150 million K. (Think trying to hit a flying mosquito with bullet at 15 meters, only worse.)

If we were hit by a Carrington level CME the effects would potentially be quite devastating depending on how much of the grid could be turned off and insulated in time. But the actual event itself would be over in less than a day or so. So this isn't the permanent effect you want.

  1. Polar Reversals; are another well documented event that could fit the bill given that at some point during the events the magnetic field protecting the Earth would weaken. The 64,000 thousand dollar question (from the point of view of your question) is how long a that weakened state would persist and how severe the weakening would be. And I don't know the answer. It could realistically be a few years at least. And of course once the field has stabilized again in its new direction things return to normal.

In terms of your wish list of technology. If the field is weakened for a considerable period of time flights at high attitude would expose passengers to higher levels of radiation and indeed under some modelling since the ozone layer could be impacted - the mount of UV hitting the Earths surface would spike (but not to levels that would be life threatening.) Sunbathing however would probably no longer be a 'thing'. So long distance air travel might well become less frequent/more expensive leading to a resurgence of rail and passenger ships.

Military equipment including ICBMs are hardened against magnetic and radiation effects so would probably be unaffected. Existing commercial satellites in orbit however would be effected - probably toasted. Perhaps even some military ones. So your power satellites idea is a non starter until the adverse effects stabilize somewhat and scientist and engineers can get a handle of how much shielding is needed to protect new launches. After that launches could resume although per unit satellites (including solar power generators) would be more expensive.

Same thing for manned flight. Initially the crews of any manned habs in LEO would have to be evacuated since currently all manned platforms orbit inside the protection of the use the Earths magnetic field. There are plans to equip space ships with their own magnetic filed generators for extended space voyages like trips to Mars etc. The haven't been built yet but could be so if there was a good enough reason manned flights could resume. Albeit by the time the final design work was done the crisis might be passing anyway.

Grids would have to be substantially hardened over time but yes, might well become smaller in extent until the filed stabilized again. (The long term benefits of interconnecting all grids would are significant so over time it would happen once all sections had been earthed properly.)

Key takeaway though? I cannot think of any way to make the effect you want permanent. There isn't any physics I am aware of that would generate the kind of 24/7 electromagnetic disturbance you want.

  • $\begingroup$ In that case, I'll just go with making my setting a 4 on the Mohs Scale of Sci-fi Hardness (tvtropes.org/pmwiki/pmwiki.php/Main/…) - the One Big Lie is that, due to some alien weirdness or god-knows-what in the past, the Earth's magnetic field is constantly reversing. Thank you for the idea of a resurgence of rail travel and passenger ships, BTW - that's another historical change that I'll incorporate. $\endgroup$
    Aug 1, 2021 at 1:22
  • $\begingroup$ I like the idea of a polar reversal as an ad hoc explanation for the effect, but in reality, you'd need to reverse the poles constantly every fraction of a second to create the hoped-for effect - and that would probably mean no birds in the sky (certainly no migrations). $\endgroup$
    – JBH
    Aug 1, 2021 at 3:18

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