# Would humanity go extinct if suddenly a parallel magnetic field of 1T fills the entire universe?

Imagine one day the universe becomes a bar magnet except all the line of force are running in parallel and the magnetic flux density is 1 tesla throughout, could this be a doomsday scenario for us? Also can you tell me how much longer do we have left and is there any countermeasures we can take given today technology? Would it made any difference if the magnetic field is instead oscillating at 1 hertz or 1 cycle every second?

(BTW 1T is equivalent to the strength of typical loudspeaker magnet and the changes is overnight/abruptly/instant/no symptom also it is 1 Tesla not 1 thousand tera Tesla!)

# Earth becomes uninhabitable

I consider this universal homogeneous static magnetic field. I summarise my conclusions below.

I first consider direct health effects. However, 1 Tesla is below the thresholds for most magnetic field-induced health complications. The immediate impacts of this field on human health would be negligible.

Next we would want to consider the effect of this magnetic field on technology. 1 Tesla is extremely strong as far as most devices are concerned. Because this magnetic field is homogeneous, it will not cause iron objects to fly about. But this magnetic field may interfere with less-sturdily-built magnetic storage devices, so we're looking at major data-loss world-wide. It will also exert forces on all current-carrying devices, such as power lines. The force on electricity transmission lines would be great enough to rip the cables from the power poles. As a consequence, modern civilisation will collapse immediately. Rebuilding with new technology which can handle the magnetic field is theoretically possible, but that would be a post-apocalyptic rebuild.

But the effects of the magnetic field on technology is a trivial matter compared to the effects of this magnetic field on the Earth and Sun.

The Earth has a magnetic field, like a bar magnet. This external magnetic field, if not aligned perfectly with the Earth's magnetic field, will attempt to get the Earth's core to precess with a period of a year or two. The movement of the magnetic field would probably have negligible consequences on the biosphere (see geomagnetic reversals), but the force acting on the core could cause a change in the length of day or axis of rotation of the Earth.

But the effects due to action on the Earth's magnetic moment would be negligible compared to effects on the Earth's rotation due to magnetic braking. The Earth's core is conductive, so as it spins it would generate eddy currents which would in turn experience a force from the magnetic field which opposes the core's rotation. I estimate this torque would be enough to immediately stop the core from spinning. The surface of the Earth would grind to a halt within a decade. With days which last a whole year, the surface of the Earth will likely become uninhabitable to all but the hardiest life-forms (hardier than humans stripped of civilisation).

But it gets worse. The Sun is a giant ball of rotating plasma so is extremely susceptible to magnetic fields. The Sun's rotation will likely be stopped by this magnetic field and its various processes (convection, sun spots, etc.) will also be interfered with. I do not know what the exact effect of this would be, but it will almost certainly be a large enough effect to shift the habitable zone away from the Earth over an undetermined time-span. This will definitely kill humanity.

If you opt for an oscillating magnetic field, the results are spectacularly and immediately catastrophic for the entire Universe. The oscillating magnetic field will produce an oscillating electric field tens of thousands of times stronger than lightning throughout the entire Universe. All life will instantly die. Chemical bonds will be ripped to shreds. The Universe will be filled with a thick, hot soup of photons with measurable mass which will completely alter the dynamics of the Universe and increase its density by a factor of about 2 quadrillion. The fate of the Universe will be to collapse in on itself.

Derivations of each of these points are in the following sections.

## Magnetic fields overview

A static homogeneous magnetic field produces some effects:

• Lorentz force on moving charges. A charged particle travelling in a magnetic field will be pushed sideways, such that unhindered it will spin around in circles (this is cyclotron motion). When a conductor moves in a magnetic field, its charges get separated to opposite sides of the conductor under the Hall effect.

• Alignment of magnetic dipoles. Magnetic dipoles attempt to align themselves to a magnetic field, experiencing a torque until they are aligned. This is the effect which makes compasses point North, allows magnetism to spread through iron, and causes bar magnets to align with each other.

• Induced current in rotating conductors. This is the operating principle of electricity turbines.

• Zeeman effect. This effect comes about due to the alignment of electrons orbiting an atom to an external magnetic field, under the same interaction that aligns other magnetic dipoles. The effect of this is to split the energy levels of the hyperfine spectrum of atoms and to shift the fine structure spectrum.

Because the magnetic field is completely uniform, there are some things which it won't do. It will not cause ferromagnetic objects to be moved, because that requires a magnetic field gradient. It will not cause an induced current in conductors moving in a straight line, because these also require gradients, although it will still induce a Hall voltage in such conductors.

## Direct health effects: Negligible

Strong static magnetic fields can have adverse health effects. The charges flowing in your blood and nerves experience the Lorentz force and an electric current is generated whenever you turn (other relevant effects are negligible for biological systems). The reports by WHO and ICNIRP provide a detailed analysis of the evidence regarding exposure to static magnetic fields and their consequences.

In a field of 2 Telsa or greater, people experience vertigo and nausea, although moving faster will amplify the symptoms. There may be cardiac issues in fields greater than 8 Tesla, although the threshold might be higher than that. However, 1 Tesla is below the threshold for most biological effects. There might be a small decrement in visual tracking and hand-eye coordination at this flux density.

There is no conclusive evidence for long-term health consequences for exposure to magnetic fields. The evidence so far points to either small effects or no effects at all. However, studies are scarce and undoubtedly they do not consider continuous 24/7 exposure to strong fields. The human race might experience a small decline in overall health and cognitive performance, but this is far from an extinction-level event. Give it a generation or two and humans would have probably adapted to the magnetic field.

## Effects on Technology: Catastrophic

The most immediate casualty of this event will be human technology. We use a lot of electricity and magnetism in modern civilisation which will all get ruined by a strong magnetic field.

The simplest effect to calculate is that on all our power lines. A current-carrying wire in a magnetic field experiences a Lorentz force, which pushes the wire in a direction perpendicular to both the magnetic field and the current. For a magnetic field perpendicular to the wire, this force is equal to the length of the wire (in metres) times the current in the wire (in Amperes) times the magnetic field (in Tesla). (See Hyperphysics for details.)

The tricky part I've found is finding out how much current is in a wire. Wires are rated by voltage, but the current varies depending on the power in the wires, which varies based on many factors. Googling gives vague quantities around 100 to 1000 Amps. This means our wires in our 1 T field experience a force of 100 to 1000 Newtons per metre. Note that since power lines use alternating current, this force is oscillating.

How does this compare to the weight of the wires? Wikipedia suggests that overhead power-lines have cross-sectional areas between 12 and 750 mm$$^2$$. Aluminium, which power lines are typically made from, has a density of 2.70 g/cm$$^3$$. This gives power lines masses of 32.4 to 2025 grams per metre, which translates to approximately a weight 0.3 to 20 N/m. Since thinner wires correspond to lower currents, this implies forces of 50 to 300 times more than the weight of the wires being exerted on power lines by the magnetic field. I lack data on the structural integrity of transmission lines, but I would guess that most power lines would break catastrophically under such forces.

There is also the matter of our digital electronics. There is potential for magnets to erase hard drives. There is contradictory evidence floating around the internet as to how big a magnet you need, but I would imagine that a constant field of 1 Tesla (which is around the upper end of a field which a permanent magnet can produce) while the electronics are running cannot be good for their health. Some electronics might survive. Some would get wiped. The magnetic strips on your credit cards will most likely be erased.

There would be other effects. All current-carrying devices, not just transmission lines, will experience a Lorentz force, which may lead to damage in less sturdily designed devices. All rotating bits of metal will generate currents which may either conduct elsewhere or produce heating and resistance. Countless other electronic devices may fail for their own reasons.

So under this scenario, our power grids will collapse and electronics will go haywire. Modern civilisation as we know it will collapse. The consequences of this are beyond the scope of this question, but humanity will not go extinct because of this. It would be possible to rebuild. Power transmission wires could be built underground and with greater structural integrity. Electrical devices would be built more sturdily to handle rogue currents and Lorentz forces. Electronics would need to be made resistant to strong magnetic fields. Given time, humanity could recover from and adapt to this destruction of much of their technology.

## Interactions with Earth's magnetic field: Bad, but probably not too catastrophic

But what would be the effect of this magnetic field on the planet as a whole?

Could the Lorentz force on the Earth disturb its orbital motion? Overall the Earth is close enough to neutrally charged to make no difference, as discussed here. This would make any Lorentz force on the Earth negligible compared to the gravitational force on the Earth due to the Sun, so I would not expect any measurable changes in Earth's orbit.

But Earth is a giant rotating bar magnet. Like any other bar magnet, Earth's magnetic field would want to align itself with this external magnetic field. You have not specified how this field is oriented with respect to the Earth, so the new alignment could point in any direction.

However, Earth's magnetic field has changed in the past during geomagnetic reversals. There are no conclusive links between geomagnetic reversals and extinctions, although there might be an increase in vulcanism.

But what if the external magnetic field is not parallel to the axis of rotation of the Earth? The Earth's magnetic field is produced by rotating columns of molten iron in the Earth's core, according to dynamo theory. So the Earth's magnetic moment has an accompanying angular momentum. The scenario we would get is gyroscopic precession.

The magnetic moment of the Earth, under the dipole model, is about $$8.06\times 10^{22}$$ N m/T. The maximum torque exerted on the Earth's dipole moment by this external field is thus $$8.06\times 10^{22}$$ N m, if the magnetic field is perpendicular to the Earth's axis. The moment of inertia of the Earth, if we approximate it as a solid ball of uniform density, is about $$9.7\times 10^{33}$$ kg m$$^2$$.

The period of gyroscopic precession is $$T_P = \frac{4\pi^2 I_s}{\tau T_s}$$, where $$T_s$$ is the period of the spinning object, $$I_s$$ is the moment of inertia along the object's axis, and $$\tau$$ is the torque. If we approximate Earth as a solid bar magnet, then the period of precession is $$5.5\times 10^7$$ s, or 637 days. If the magnetic field is not perpendicular to Earth's spin axis, then the period of precession will be longer because the torque will be smaller.

Having Earth's rotation axis constantly changing would surely wreak havoc on the climate. But while this might cause a mass extinction event, humanity is adaptable enough to survive as a species (even if civilisation will collapse).

However, the truth will be far more complicated than the solid bar magnet approximation. The core of the Earth, where the magnetic field is generated, is not rigidly connected to the crust of the Earth, where we experience the Earth's rotation. Indeed, even now the magnetic poles of the Earth do not precisely align with the Earth's rotation axis. A full answer as to how the precession of Earth's magnetic moment would affect the rotation of the Earth as a whole, especially when you add in all the other complicated effects which affect the Earth's rotation (see, e.g., this what-if), is far beyond the scope of this site. But we could expect some gradual change in the length of the day and orientation of the Earth due to magnetic torque.

## Effect on Earth's rotation: Catastrophic

However, we can expect a far more dramatic change in the length of day due to magnetic breaking from eddy currents. The Earth's core is electrically conductive, so its movement in a magnetic field causes charges to separate and currents to flow. These currents will in turn experience a Lorentz force from the magnetic field which will oppose the motion of the Earth's core.

An exact calculation of this effect, even if we assume a simple homogeneous iron sphere, is extremely difficult. However, we can use dimensional analysis to find an approximate formula for the torque on the Earth (good to within an order of magnitude).

The current density $$j$$ is the Lorentz force, which is velocity $$v$$ times magnetic field $$B$$ times charge, divided by the charge and the resistivity $$\rho$$. So $$j\propto v B/\rho$$. In circular motion, $$v=\omega R$$, where $$\omega$$ is the angular frequency and $$R$$ is the radius, so $$j\propto \omega R B/\rho$$.

The Lorentz force $$F$$ on an infinitesimal volume $$dV$$ of this current-carrying object is $$F dV = j \times B dV \propto \omega R B^2 dV /\rho$$. The torque $$\tau$$ over the whole object is done by the integral $$\tau = \int r \times F dV \propto \omega R^2 B^2 V /\rho = \frac{4}{3} \pi \omega R^5 B^2 /\rho$$. This formula likely overestimates the torque by a factor, since it doesn't account for the lower velocities and distances near the centre of the sphere. But besides a scalar factor it should have the right functional dependence. It has the correct units, at least. As a fudge factor I'll remove the $$4\pi/3$$ constant to counter-balance the overestimation.

Taking $$\tau \approx \omega R^5 B^2 /\rho$$, we can plug in some values. At 86,400 s per cycle, $$\omega = 7.3\times 10^{-5}$$ radians/s. Only the Earth's core is metallic, so we will consider its radius of about $$R=3.4\times 10^6$$ m. Our magnetic field is $$B=1$$ T.

The electrical resistivity is a bit trickier, since $$\rho$$ is temperature and pressure dependent. At atmospheric pressure, iron has a resistivity of $$9.71\times 10^{-8}$$ $$\Omega$$ m at room temperature and a resistivity of $$139\ \mu\Omega$$ cm $$= 1.39\times 10^{-6}$$ $$\Omega$$ m near its melting point. Iron's melting point is 1811 K, but the Earth's core is at least 3000 K. However, increasing pressure reduces electrical resistivity. This work found that at 15 GPa of pressure, the resistivity of iron is only $$4.5\times 10^{-7}$$ $$\Omega$$ m at 1600 K. Since we're already dealing in approximations, I'll take the resistivity of the Earth's core to be about $$10^{-6}$$ $$\Omega$$ m.

Plugging these values into our formula, we get a torque of $$3.3\times 10^{34}$$ N m. The moment of inertia of the Earth is only about $$9.7\times 10^{33}$$ kg m$$^2$$, so we have an angular deceleration of 3.4 radians/s$$^2$$, which would bring the Earth's core to a screeching halt in a few microseconds.

While this might invoke pictures of instant global windstorms and everything falling over (see 'Global Windstorm' in the book what if? by Randall Munroe, for instance), the reality will likely be less destructive. Only the core of the Earth stops spinning. The surface of the Earth is separated from the core by the mantle. So the magnetic field would apply a braking force on the core of the Earth which would, over time, slow down the rest of the Earth. We would get some nasty earthquakes when the field turned on, though.

I can't say how long it would take for the Earth to stop spinning. Normally the coupling between the core and the crust takes around a decade, but this is far from normal circumstances. I'd guess that it would take up to a few years for the Earth to stop spinning.

With the Earth no longer rotating, we now have a serious problem. The length of a day, as measured by where the Sun is in the sky, becomes one year. At the poles this won't make much difference locally, but away from the poles you will get scorching heat for 6 months followed by freezing cold for another 6 months. There will be extreme winds as a result too.

If humanity had access to the power of civilisation, they might be able to devise something to avoid total extinction, although fatalities would still be enormous. Air-conditioned underground shelters with hydroponic food supplies and sturdy sources of renewable power, perhaps. But since civilisation crashed immediately upon this magnetic field appearing then humanity would be as ill-equipped for this catastrophe as all other forms of surface-dwelling complex life and would likely go extinct. Inhabitants of the Arctic circle might fare slightly better than everyone else, but they would still experience a drastic shift in the climate which would probably collapse the local biosphere which would result in their extinction too.

If the Earth stopped spinning, then the Earth's magnetic field would probably also collapse. But we now have a bigger magnetic field spanning the Universe, so this is probably a negligible effect.

If the magnetic field happened to be exactly aligned with Earth's rotation axis, then this catastrophe might not happen. But such an alignment is unlikely.

## Effect on the Sun: Catastrophic

The Sun is a big ball of rotating plasma, which is a soup of charged particles. This means it definitely interacts with magnetic fields.

A magnetic field of 1 Tesla would definitely be large enough to mess with the Sun. This page reports that the Sun's typical surface magnetic field is $$10^{-4}$$ T and sun-spots have fields of up to 0.4 T. This paper reports that coronal loops (involved in solar flares) have magnetic fields around $$3.5\times 10^{-2}$$ T. A 1 T field should thus be enough to disrupt many of these processes.

If we apply the same logic as I applied to the Earth to the Sun, then I would also expect the Sun's rotation to come to a screeching halt due to magnetic braking. If the Sun were to stop spinning, this would greatly interfere with the Sun's convection, which would in turn change how heat and matter is distributed through the Sun, which would modify its nuclear fusion reactions and the Sun's size and temperature.

Precisely how the Sun's temperature will change is well beyond my knowledge. However, considering the drastic extent of the changes, the habitable zone will almost certainly shift such that Earth is no longer in it. All water on Earth will either boil or freeze. Humanity will die.

How long this will take, though, I don't know. It could be days, since the magnetic field is quite strong. It could be years (maybe thousands of years, even), since it takes a long time for reactions in the core of the Sun to reach the surface.

However, since civilisation crashed so catastrophically, and the climate has also crashed so catastrophically, even if the changes in the Sun take many years to make the Earth utterly inhospitable the odds are stacked against humanity. We would have to move to another planet which is in the new habitable zone and terraform it to be hospitable to life. This is beyond our current technology. Humanity has no hope.

## Oscillating magnetic field: Everything dies immediately

The magnetic braking on the Sun and Earth would still apply in the case of an oscillating magnetic field. We would still get the catastrophes described above.

An oscillating magnetic field would also generate electrical currents in everything. By Maxwell's equations, an oscillating magnetic field produces an electric field. Based on the sinusoidal plane-wave solutions of the electromagnetic wave equation, an oscillating magnetic field with a strength of 1 Tesla will produce an oscillating electric field with a strength of $$3\times 10^8$$ V/m.

This is an enormous electric field. $$10^8$$ V is the voltage in a typical lightning bolt (see this table), and we have that voltage every metre. All life in the universe dies immediately from electrocution. The entire atmosphere, and probably all other matter in the Universe, undergoes dielectric breakdown, making everything a conductor with currents running through it. Chemical bonds will be ripped to shreds, and organic life will become impossible.

But there's more. The energy density in the electric field is $$\epsilon E^2/2 + B^2/2\mu$$, which for an electromagnetic wave simplifies to $$B^2/\mu$$, where $$\mu=4\pi \times 10^7$$ H/m is the magnetic permeability (in vacuum). Our oscillating electric field thus fills the universe with photons with an energy density of $$8.0\times 10^5$$ J/m$$^3$$. This is a lot of energy, although from ripping matter apart we could already guess that.

This energy has mass. From $$E=mc^2$$, our photon field has a density of $$8.9\times 10^{-12}$$ kg/m$$^3$$. Interstellar space has a density of about 1 hydrogen atom per cubic centimetre, which corresponds to $$1.7\times 10^{-21}$$ kg/m$$^3$$. The density of the universe as a whole is about $$5\times 10^{-27}$$ kg/m$$^3$$. This field increases the density of the universe by a factor of 2 quadrillion. The result is about a thousand times denser than nebulae and the solar corona.

By pushing the density of the Universe far above the critical density, the Universe will become destined to collapse in on itself. Also, local perturbations to the field are likely to cause localised collapsed, resulting in tangles of twisted electromagnetic fields. It will be as if the entire Universe became like the Sun's corona, which will put the Universe into a new regime where everything is dominated by the seething mass of high-temperature photons.

I hope that's catastrophic enough for you.

## References

• Alas that I have but one upvote to give. Dec 26 '19 at 7:01
• Did you happen to have a manuscript ready for publication when this question came up? Very impressive! Dec 27 '19 at 20:33
• @Tom Our magnetic field would indeed collapse in this scenario (see end of Effect on Earth's Rotation), but it is replaced by a far larger universal magnetic field. However, as I think about it, the parallel nature of this new field is significant. The component of particles' velocity which is parallel to the field will not be deflected, so we would face a radiation hazard. However, unless this field were aligned along Earth's orbital plane, the Sun's radiation would be deflected, leaving only far more distant sources (although the collimation may prevent their diffusion). (continued) Jan 29 at 6:41
• @Tom (continued) Even if the magnetic field were aligned with Earth's orbital plane, it would only channel the Sun's radiation towards us twice a year. However, it might be more concentrated due to not radiating outwards as much. I'll have to think more deeply about a large magnetic field's ability to collimate charged particles radiated from a point source. Jan 29 at 6:44
• I would not put the ozone layer specifically at any greater risk than the rest of the atmosphere, though. As long as we have an oxygen-containing atmosphere and inbound UV radiation (the latter of which will be true for as long as the Sun is hot, as light is not affected by magnetic fields), we'll produce an ozone layer. Jan 29 at 6:47
• Mass of an electron: 9.10938356 × 10^-31 kilograms
• Density of electrons in iron: 1.7x10^29 e/m^3
• Radius of heliopause: 1.8x10^10 km
• Volume of sphere: pi*r^3

From the above values, we can compute...

• Volume of heliopause: 1.832e40 m^3
• electrons added to our solar system by this magnetic field: 3.115e69
• Mass added to our solar system: 2.837e39 kg

Now consider this:

• Mass of Sagittarius A*, the black hole at center of Milky Way: 7.956 x 10^36 kg
• Volume of Sagittarius A*: Approximately half distance of Sun to Earth

The mass you've added to the solar system is greater than the mass of a super massive black hole, but it is more spread out. I couldn't quite puzzle out whether it is or is not within the Schwarzschild radius, but I believe it is. So most likely, you have introduced enough mass to create a black hole everywhere, with all the gravity ripping effects that implies.

Even if you haven't introduced a black hole everywhere, in the vicinity of the Sun itself, you have considerably increased its mass. Increased mass kicks its temperature way up, and you easily cook the Earth. You can put your own math together there.

• Where do all these electrons come from? I don't think the querent is planning to fill the universe with iron, they just want the magnetic field. Now, it is possible that the mass introduced by the energy of the magnetic field alone might have some effects, but I don't think turning the universe into electron soup is one of them. Dec 23 '19 at 8:54
• I didn’t add iron. I added enough ELECTRONS only — no protons — to account for a similar strength field. The electrons are simply created ex nihilo, per the question’s original declaration (the field just appears from nothing). @BBeast
– SRM
Dec 23 '19 at 14:20
• @BBeast put another way: a magnetic field only exists if the author has introduced an electron soup. No electrons, no magnetic field.
– SRM
Dec 23 '19 at 14:22
• Fair enough, although in that case the bigger problem would be filling the universe with an enormous electric charge (and also all that matter). This answer then becomes a consequence of how you generate the field rather than what the field itself does. Additionally, you only need about a sixth of that number of electrons: most of the electrons in iron are paired so do not contribute to the magnetic moment of iron. Although that would not change the outcome. Dec 23 '19 at 20:52
• I understand the question more in the way: The laws of physics themselves change, so that the 1T magnetic field is suddenly a basic property of space itself. With all the implications about suddenly having a defined inertial frame of rest respective to the universe itself. Dec 24 '19 at 22:50

There only bad news here.

and there are 5 reasons for that and more - earth rotates, the earth orbits the sun, sun fly trough space, the sun orbits the galaxy

all that happens in a 1T magnetic field, and assuming it being equal all over the space, there is no induction causing current and thus high voltages, but there are Lorenc forces that act on positive and negative charges and creating those currents and voltages because of superposition of all the movements. (if field oscillates it induces currents and all the beauties of eclectic shocks with it on the scale of the whole planet - thus shocking with voltage and heating everything)

Speeds which we fly through the field - 450m/s cuz earth rotation, 30km/s cuz orbiting the sun, sun fly 20km/s if I recall correctly, do not recall other speeds - so as you may see it is significantly faster than speeds of a typical rotor in electric engine so effects are higher as well.

The field will affect processes happening in stars as well.

So chaos starts the moment the field engages. Which shape and form the chaos will take needs quite a thinking - but problems mentioned as about difficulties of our technologies to work in such conditions are minor, not important effects on the grand scale of things.

So if you wish to provide any chances you have to raise the field over decades. It not necessarily has to be a universe-wide event, it may be a wave traveling after some grand event. Otherwise, there are no chances, too sudden and too harsh.

Assuming the constant field:

• all electric/magnetic motors stop to work immediately (which is kind of really bad, but survival is possible)
• Building containing a lot of magnetizable material may experience trouble (which is bad)
• neon lamps, high pressure natrium lamps etc. may have problems
• mass spectrometer fail
• mobile compasses fail
• GPS fails (atomic clocks will fail)
• gears containing ferromagnetic components fail
• magnetic switches fail
• i would have to calculate, but probably we see FETs having change properties, so modern circuitry may fail
• vaccum tubes may fail
• electromagnetic relais may fail
• magnetic valves fail
• Our ionosphere changes
• Plasma physics in the sun changes

The good news is: we probably would not die right away. * assuming that the sun stays alive, we can have solar power and water power using electric generators without stator or ferromagnets * Electronics can be easily redesigned or shielded * Once we redesign everything a little we probably could make good use of it.....

The 1T/second changing field has probably much more funny consequences, i leave that to other answers to elaborate, in that case all our energy problems would be solved, but i could imagine that there is a heatup of ferromagnetic materials in the ground, and also the constant reversal may cause the earth magnetic core to oscillate and emit low frequency sound waves (Earthquakes?). I am not an expert on either of these subjects.