What would be the effect of a giant magic fireball burning in the ocean?

(I got a lot of good information in the responses. I'm doing some research and will edit my post to be more specific.)

Imagine there's a magical fireball that stays in one spot in the middle of the ocean and emits heat at a constant rate that is hot enough to evaporate any water on contact. It's visually sun-like but doesn't do all that fusion crap, it just sits there perpetually emitting its fiery hotness.

Let's say it'll be big enough that its diameter will go all the way to the ocean floor while also sticking out of the surface of the ocean at the same time (ocean avg 3.5km deep), but smaller than the size of a dwarf planet/asteroid like Ceres (approx 939km diameter). So let's call that a range of 4km to 900km in diameter for our fireball. enter image description here It ought to be somewhere in that range; I'm still playing with the size.

My fantasy planet is Earth-like in size and in ecosystems (with some fantastical exaggerations and distortions lying around). I'd imagine:

  1. Fatal amounts of heat and steam within X distance of the fireball
  2. Loads of precipitation wherever it cools back down
  3. All that rain causes flora and fauna to flourish in those areas

I believe there may be other considerations that I'm overlooking to really understand what might go on here. With the given size and enormous volume of water, would this be big enough to affect the whole planet? As in all of the major wind and water currents? Would it sauna everyone to death? What would the water flow be like immediately around the fireball? How different will the effect be at different fireball sizes? Are there any other considerations for this setup that you can think of? Do you know any real-world experiments or setups to look at that may shed light on this issue? I tried to find some "large amounts of water vs very hot object" videos but didn't quite find what I was looking for.

I'd like to have a more functional understanding of the effects at play here because I'm certain the inhabitants of the area would as well. Like I could see the effects of this fireball shaping agriculture, sailing, flying, and even religion/culture for the people living in the region. What do you think?

I don't have a map of my fantasy planet, so picking a real-world ocean and plopping this fireball thing in the middle of it may be a good focal point to figure out the details. Let's say in the Pacific. Thoughts?

Thank you for your time.

  • 9
    $\begingroup$ How hot is it? That will make a big difference. $\endgroup$ – Willk Oct 9 at 2:48
  • 3
    $\begingroup$ Hello and Welcome to worldbuilding Terence. I would recommend you limit your questions to a single question. You seem to have presented us with all your trailing thoughts and this can make the real question you want to ask hard to answer. You will also need to determine a Size and Temperature if you want a detail answer. Having a range starting from 4 then expanding that 225 times creates a huge difference. $\endgroup$ – Shadowzee Oct 9 at 3:31
  • 8
    $\begingroup$ @renan Internet communication protocol? Insane Clown Posse? Illiterate Crackhead Punks? $\endgroup$ – SRM Oct 9 at 5:28
  • 4
    $\begingroup$ @SRM Insane Clown Posse. Check the lyrics for their song*"Miracles"* and its videoclip. It's comedy gold for most of it, but then there's the part with "And I don't wanna talk to a scientist, y'all mother****ers lying, and getting me pissed". $\endgroup$ – Renan Oct 9 at 5:36
  • 5
    $\begingroup$ @Renan Hah! I picked that one as a joke from a list of acronym expansions I found online. Didn't think that would be the right one! Thanks. $\endgroup$ – SRM Oct 9 at 11:17

Let's say your magical sphere has radius $r$ of 10km (so just poking up into the outer atmosphere) and is at a temperature $T$ of 1,250K (so glowing a nice warm yellow). The total radiative heat flux from the sphere is given by:

$$ Q = \sigma T^{4}. 4\pi r^2 \approx 1.7 \times 10^{14} \mathrm{W} $$

Where $\sigma$ is the Steffan-Boltzman constant. A proportion of this energy, however, will be lost out to space and so will not affect the biosphere. Let's say that the energy absorbed by the rest of the planet is $10^{14} \mathrm{W}$, or about 100 terawatts.

This is not actually that much energy, on a planetary scale. The solar constant (the measure of solar power incident at the Earth's surface) is about 1.3kW per square metre, so this is equivalent to doubling the solar energy deposited over a circular area just over 200km in radius, which is probably about the size of the 'chaos zone' around your artefact in any case.

(Note that because this equation is quartic in the temperature of the sphere, you can go from innocuous to world-destroying very quickly. Raise the temperature to 2,500 Kelvin, and your power goes up sixteen-fold, and the size of your chaos zone increases to 1,600km diameter. Go up to 8,000 kelvin, and the power input is equivalent to doubling the solar power across the whole earth; this would almost certainly cause a Venus-like biosphere destruction. At 100,000 Kelvin, you will deposit enough energy to exceed the gravitational binding energy of the Earth within a millennium; I'm not sure exactly how the disaster would unfold in this case, but it's sure to be pretty bad. But If you keep the temperature 'reasonable', you can maintain a stable biosphere.)

What would this sort of energy look like? Estimates of the power of hurricanes are on the order of $10^{14}$ to $10^{15}$ Watts, so at the mid-range the effects would probably manifest as a large hurricane surrounding the artefact, although the wind and water flows near the centre would be much more confused, with similarities to nuclear mushroom clouds. Modelling the behaviour very close to the artefact ('very close' here probably meaning up to a few kilometers) would be very computationally challenging.

On a planetary scale, this energy input is on the same order as the 3.2TW of greenhouse-gas-induced heating that's currently causing our climate woes, so the sudden appearance of such an artefact would put the Earth on the same sort of global warming course that we're currently facing. To be honest, the fact that we're doing twice as much damage to the biosphere with cars and power stations, as a city-sized white-hot alien artefact, kind of makes me want to move in with the aliens...

  • 24
    $\begingroup$ Indeed; hot enough to meet the two criteria (water boils on contact, emits visible glow), but cool enough to not immediately wreck the planet. Worldbuilding is more fun when you still have a world left at the end of the equation :-) $\endgroup$ – Stephen Oct 9 at 9:49
  • 3
    $\begingroup$ It would be like a Jupiter Red Spot with this parameters. And I belive wind patterns would be the same. $\endgroup$ – ksbes Oct 9 at 9:51
  • 9
    $\begingroup$ The energy output by this thing would be vastly greater, though, since it's in the ocean and constantly touching and boiling off water, and needs to produce enough energy to keep this going perpetually, assuming there's not a magical vacuum surrounding the fireball and preventing any conduction cooling. I assume the energy output by radiation will be peanuts compared to the energy output by thermal conduction. $\endgroup$ – Erik A Oct 9 at 13:45
  • 3
    $\begingroup$ The surface of the artefact might not be surrounded by a vacuum, but it would be surrounded by a region of superheated steam. The thermal conductivity of which would depend greatly on the temperature and pressure, but might be on the order of 100mW/m.K. I can imagine this steam area to be 1m thick, which gives a conductive thermal flux of 100W/m2 with a thousand-degree temperature differential. Compare that to the radiant thermal flux of 138 kilowatts /m2. $\endgroup$ – Stephen Oct 9 at 14:21
  • 9
    $\begingroup$ @Stephen I just realized there's a bigger problem. The fireball is in the ocean, constantly sending steam into the atmosphere. At 10km in size, I think this will bring global greenhouse gas levels past the runaway threshold. At that point, the heat given off by the fireball wouldn't even matter. With an atmosphere full of water vapor, the planet would no longer emit enough thermal radiation to offset even sunlight and remain habitable. The new surface equilibrium temperature would be enough to vaporize the remaining water on Earth and keep it vaporized. You would get Venus. $\endgroup$ – Priska Oct 9 at 16:38

There is no scenario in which the biosphere survives long. You have, at best, a few centuries. Say the fireball is as cool as possible while still being a fireball; 100 degrees celsius. All the oceans will continually drain towards the fireball and will boil on contact, as you said. This is bad news for your biosphere, because that's a huge amount of water vapor entering the atmosphere, and water vapor is a major greenhouse gas. The hotter the ball is, the faster this greenhouse effect ramps up.

If the ball is hotter than about 1400C, you will start melting the ocean floor. This is also very bad for the biosphere. Most mass extinctions have coincided with massive volcanic eruptions, and that's basically what you have here. Molten rock gives off some pretty nasty fumes, which further alter the climate. If the ball is effected by gravity, it may sink into the mantle. This is the best case scenario I'd think. Eventually it would sink to a layer as hot as it was, and would stop causing chaos. The biosphere will probably be wrecked before it settles, but it might be able to recover. If it doesn't sink, you have a permanent volcanic eruption, which as I said above, is really bad news. Most life will be dead within a few years.

The Earth's core is 5400C. If the ball is hotter than this, even if it sinks, it never stops causing problems. If it doesn't sink, just know that 5400C is ridiculously hot. Iron boils at 2750C. This is like thousands of atomic bombs going off constantly in one place. Weather will be extreme immediately. We're talking winds many times faster than the fastest hurricane. The rain will be extreme as well, and it won't just be water. All that rock boiling will come back down, and it'll be super-heated. Lava rain basically. All macroscopic life will probably be dead within the day. Maybe people in hardened air-tight bunkers could survive a little longer, but the extreme earthquakes will get them soon enough. If the ball does sink, the Earth's plate tectonics will go crazy as it sinks. Massive earthquakes and volcanic eruptions everywhere. Mass extinction, just like in the 1400C example. Once it reaches the core, it'll keep sinking, and will disrupt the Earth's magnetic field. No magnetic field means no UV protection. Earth's surface will be sterilized in months, maybe a year. Life around deep ocean vents may survive, if the rampant volcanism didn't already get them.

Somewhere around 10 million C, the ball is as hot as the surface of the sun, and the Earth will be vaporized. Nothing survives.

  • 8
    $\begingroup$ Surface of the Sun is about 4000-6000C, not millions. $\endgroup$ – ksbes Oct 9 at 9:48

You are basically cooking your planet on a stove.

This magic fireball is an infinite source of heat, so it will sit there continually pouring heat into the planet's system. Water near it will be heated into steam, but the coolness of the water will not cool the fireball at all. This will cause the overall temperature to rise and rise until everything on the planet eventually matches the heat level of the fireball itself. Eventually the ocean will boil and steam in the atmosphere will render all life extinct. You will end up with a giant ball of ash (or maybe lava). And a 900km fireball is easily large enough to make this happen in short order.

  • 20
    $\begingroup$ We already have a source of practically infinite heat which pours heat continuously into Earth's system: it is called the Sun. Without knowing the actual parameters of the heat source we cannot say anything definite. $\endgroup$ – AlexP Oct 9 at 8:43
  • $\begingroup$ It's a fireball. It evaporates water on contact. It's at least large enough to reach from ocean floor to surface, and it is sitting in the ocean. If you are not convinced, it might help to ponder the difference between watching a campfire and sticking your hand into the campfire. $\endgroup$ – Priska Oct 9 at 8:59
  • 19
    $\begingroup$ To be slightly pedantic: the temperature of the Earth will rise until it reaches thermal equilibrium, not until it reaches the same temperature. The heating will stop when the Earth has reached a temperature where it radiates the same amount of energy as the sphere emits. But since the Earth is larger than the artefact (hence has a larger area), that will happen at a lower temperature. For a 60km-radius sphere (ie an Earth:Artefact radius ratio of 100:1) the temperature ratio would be 10:1, so the Earth would only get to a tenth the temperature of the sphere. $\endgroup$ – Stephen Oct 9 at 11:52
  • $\begingroup$ I just want to point out that all the OP has to do is move his planet farther from the sun. Mars is on average 60C cooler than Earth, so if I understand stephan's ratio, a 10km sphere would raise temp by a 60th and a 3600K sphere would raise a Mars distance Earth to Earth temperatures. $\endgroup$ – lazer-guided-lazerbeam Oct 9 at 13:35
  • 1
    $\begingroup$ Stephen is giving a simplification of the story, as I was originally. The average temperature of the Earth will raise by 1/10, but this does not mean each piece of land on Earth will be 1/10th hotter. The regions closer to the fireball will be uninhabitably hot, and the regions on the opposite side will be uninhabitably cold if you set the planet too far away from the sun. So there will only be some intermediate region that may be habitable. $\endgroup$ – Priska Oct 9 at 14:15

The fundamental problem is that there won't be an ocean left. And evaporating the ocean will destroy the biosphere from the heat.

The bottom of the ocean is 1000 bar of pressure. To stop the ocean from flowing in, you need 1000 bar of steam, which requires near star-core scale temperatures (400,000 K). And then you have a star on your planet, which means you don't have a planet for long.

If you simply evaporate the incoming water, well then the water flows out into the artifact at a rate equal to how fast it would be moving if you dropped water in a vacuum at the top of the ocean.

As a simple model, I'll assume a 3 km tall cylinder 1 km in radius. This has a surface area of 3 km * 2 * pi * 1 km, or ~20 km^2.

It has a diameter of 6 km. The rate at which water inflows is roughly $\sqrt{ h * 20 m/s^2 }$, so we want $1 g/cm^2 * 6 km * \int_{h=0}^{3 km} \sqrt{ h * 20 m/s^2 } dh$

Using wolfram alpha we get a flow of $2.939×10^{12} \frac{kg}{s}$. Evaporating that is 40.65 kJ/mol -- water is 18.0153 g/mol, so this is $\frac{40.65 \frac{kJ}{mol} }{ 18.0153 \frac{g}{mol} } * 2.939*10^{12} \frac{kg}{s}$

Or $6.6316048 × 10^{18} W$.

This exceeds the heat provided to the Earth by the Sun. So bye-bye biosphere.

  • 2
    $\begingroup$ I don't understand your rationale; the artefact is a heat source, not a wormhole. The high-pressure-high-temperature water at the bottom would form a supercritical fluid such as you find in 'black smoker' hydrothermal vents. The water wouldn't simply vanish allowing further inflow. $\endgroup$ – Stephen Oct 9 at 15:30
  • $\begingroup$ @Stephen "hot enough to evaporate any water on contact." -- supercritical fluid is not evaporated. In your solution, most of the fireball is actually drowning in water. To maintain 1000 atm, you need almost all of the water column above a point to be intact; maintaining that pressure with air is not possible without world-destroying consequences. The evaporated 1000 atm water vapor blasts upwards and is replaced by new water $\endgroup$ – Yakk Oct 9 at 16:41
  • $\begingroup$ @Stephen Ah, I see my mistake; there is no way to have a water gas at 1000 atm, period. So the object cannot "evaporate any water on contact" deep in the ocean. Well, unless it boils away the entire ocean (which it does in the second solution). $\endgroup$ – Yakk Oct 9 at 16:51
  • $\begingroup$ I was more thinking of 5km depth, which would be about 500atm. Maybe it's still too much. But I did also read about the black smoker vents and supercritical fluid. I think getting the water to reach supercritical levels might make more sense. I found the numbers for water to go supercritical: about 373 C and 217atm. An earlier comment said 1400 C would start melting the ocean floor, which I want to avoid. Using the earlier number of 1250 K (976 C) seems like a good middle ground, as the floor won't melt, but it'll still create supercritical water anywhere below 2km deep. Is this correct? $\endgroup$ – Koborakai Oct 10 at 0:03
  • $\begingroup$ @terence where does the pressure come from? If the water above boils, there isn't enough density. If it doesn't, the sphere isn't vaporizing water on contact, but rather is underwater itself. $\endgroup$ – Yakk Oct 10 at 0:08

Hm... It does sound to me like you will just keep on putting Energy into your planet, which will make the whole system gradually heat up indefinitely even if it is a small ( < 10km) Ball of 600-2500°C. I don't have that much knowledge about the details as some of the others have, but how about this:

Try to have it as cool as possible (600-800°C is deep red while ~2500°C is glowing white) so it doesn't have any global consequences. Have the ball somehow float at the same height so it doesn't fall down and melt through the earth's mantle. Also create another ball that absorbs heat and sends it to the Fireball on the other side of the earth so you don't have to deal with the whole planet heating up for millenia and keep the law of energy conservation. That way you get a nice pole of extreme heat and a pole of extreme cold, which should also be a nice point for the plot.

  • $\begingroup$ Your infinitely hot earth will emit an infinite amount of radiation energy per second. Please recalculate ;) $\endgroup$ – Hans Janssen Oct 9 at 20:15
  • $\begingroup$ An infinitely hot planet would do that, but it will be uninhabitable way before that. A part of the heat would be emitted as radiation, while another would be absorbed by the planet, heating it up. At least that's what my highschool-and-one-semester-university-physics knowledge is telling me... $\endgroup$ – Anton Oct 10 at 8:09
  • $\begingroup$ @Anton When the planet starts heating up, it will start emitting more radiation. Eventually, it will reach an equilibrium temperature where the additional power it radiates is equal to the output power it's absorbing from the sphere. At that point, the planet will stop heating up. The problem is trying to design this system where that equilibrium point doesn't destroy all life on the planet. $\endgroup$ – reirab Oct 10 at 22:44

The above answers, particularly Stephen's first one which sets out the total power of the object and shows that it can be achieved while maintaining a habitable planetary system, cover most of what you ask, but you do need to consider the location of the object with regard to latitude and relative position of continents. Atmospheres and oceans will convect and create patterns of moving air - think jet stream winds, Atlantic gulf stream etc. On an ideal planet rotating about its poles and heated from a central star, with a uniform atmosphere / ocean, you will get jet streams (or ocean streams) in the form of belts and zones rotating in opposite directions around the planet, with cyclonic and anti-cyclonic circulation at the boundaries between the belts and zones. Your object will inject a large amount of heat and moisture into the oceanic and atmospheric circulation at its location. If that is at a mid latitude with an uninterrupted flow around the planet (think the Southern ocean but a bit further up) then you would likely see a hurricane-scale perpetual storm around its location, but also a much more powerful water vortex arising from the water circulation around the object: that's something we don't have an equivalent of on Earth, but with the rate of water uptake from evaporation on contact with the object it would kind of be like a reverse plughole, with water taken up into the atmosphere rather than down the plughole. Obviously there would be intense rain in the vicinity too, on the scale of the atmospheric storms. On the other hand, if plonked in the middle of the Earth's arctic ocean with surrounding continental masses there would be very little rotational effect but the object would still cause large scale dumping of water vapour over the surrounding few hundred miles - in this case you could potentially generate a ring of ice mountains around the pole.

The other thing to consider is the mass of this object. Even though at 1250K it won't melt through to the mantle, if it's a sphere then all of its mass will act on a small contact patch at the bottom of the object: at 8-10km diameter as discussed in other answers, if the object were made of something like rock or metal the pressure would be colossal and it would sink part-way into the planetary crust anyway, like if you put a big ball-bearing on soft mud. At that mass it would definitely have a measurable effect on the direction of the gravitational field in the vicinity (google Schiehallion gravity experiment for an idea of what I mean).

On the other hand, it's magic so maybe its weight is negligible?

New contributor
Adrian is a new contributor to this site. Take care in asking for clarification, commenting, and answering. Check out our Code of Conduct.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.