Original prompt:

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

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."

First edit with new specifications:

  • Solid, non-buoyant, fiery magical sphere
  • 10km in diameter
  • Temperature of consistent and perpetual 1250K/976C
  • DOES NOT necessarily evaporate/vaporize water on contact (but does boil)
  • Will not sink into the Earth
  • Sits on floor of South China Sea (5km deep, top half of sphere exposed)

enter image description here

  • 55 mi from Scarborough Shoal
  • 130 mi WSW to next closest (Unnamed) Island
  • 136 mi from Truro Shoal
  • 185 mi from closest coastline of Philippines
  • 245 mi from Manila, Philippines
  • 335 mi from Puerto Princesa, Philippines
  • 545 mi from Qui Nhon, Vietnam

Latitude and longitude from Google are 14°24'09.6"N 117°20'05.9"E

enter image description here

I'm using a real-world example location just so all the data is already there and I don't have to invent a bunch of it. This location in the South China Sea is perfect because it's very similar to where the sphere would be on my fictional planet. There's an interdimensional rift on the opposite side of my fictional planet, so assume the same for this scenario, and assume it absorbs the excess heat generated by the sphere. Iceland would be a comparable real-world location for said rift. For those who've commented about these elements of my planet creating a smaller habitable region for people to live, you've got the right idea about where I'm going with this.

I expect the area close to the sphere (within 5km) to see some pretty extreme water boiling effects, like what is seen in this video right when the 1000C kettlebell makes contact with the water, only continuous and on a much bigger scale:


For the area between 5km and 200km, I expect there to be dangerous storms on the scale of hurricanes. More than one person has made such suggestions. The math can be found in the top responses.

To wrap this up, I'd like to limit myself to the environmental/weather questions as before, but with the South China Sea location as a reference point. What would be the effect of this sphere on the specified neighboring locations at their various distances? How would it interact with the air and ocean currents that flow primarily northeast and southwest through the South China Sea?

enter image description here

If there's not much to add/change in the "within 200km" range, then I'd still be curious about the effects of the sphere beyond 200km. I'd guess that once the storms from the sphere hit land (especially higher elevation), then they'll start slowing down and dissipating. Is this accurate? The furthest location I chose for reference is Qui Nhon, Vietnam, but if there are potentially-affected locations further away, feel free to include them in your response.

I hope this is an improvement from before and worthy of a revisit from everyone. Please let me know of any errors. Thank you!

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    $\begingroup$ How hot is it? That will make a big difference. $\endgroup$
    – Willk
    Oct 9, 2019 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, 2019 at 3:31
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    $\begingroup$ @renan Internet communication protocol? Insane Clown Posse? Illiterate Crackhead Punks? $\endgroup$
    – SRM
    Oct 9, 2019 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". $\endgroup$ Oct 9, 2019 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, 2019 at 11:17

7 Answers 7


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...

  • 26
    $\begingroup$ 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, 2019 at 9:49
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    $\begingroup$ It would be like a Jupiter Red Spot with this parameters. And I belive wind patterns would be the same. $\endgroup$
    – ksbes
    Oct 9, 2019 at 9:51
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    $\begingroup$ 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, 2019 at 13:45
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    $\begingroup$ 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, 2019 at 14:21
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    $\begingroup$ @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, 2019 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.

  • 9
    $\begingroup$ Surface of the Sun is about 4000-6000C, not millions. $\endgroup$
    – ksbes
    Oct 9, 2019 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.

  • 21
    $\begingroup$ 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, 2019 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, 2019 at 8:59
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    $\begingroup$ 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, 2019 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. $\endgroup$ Oct 9, 2019 at 13:35
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    $\begingroup$ 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, 2019 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, 2019 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, 2019 at 16:41
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    $\begingroup$ @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, 2019 at 0:08
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    $\begingroup$ @terence if it is a solid sphere it might work; the solid sgere can provide pressure. A zone of nothing but magical heat starts boiling the ocean from the top; this drops pressure lower down (as no more water column), and you either have water flowing in and boiling as fast as it can be replaced or somehow enough pressure from steam to match a water column of non-trivial depth until you hit 3x point (!). I lack the math to solve for that, but my gut says "no". A solid sphere would be far more sane. $\endgroup$
    – Yakk
    Oct 10, 2019 at 1:42
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    $\begingroup$ Aee, water requires lots of energy to boil, and flows downhill. So the depth of the boil determines the flow, which in turn determines the wattage required. Supercritical is deep-away, so insane-wattage away. But that means the sphere has to not emit much heat underwater to avoid boil -> expell vapor -> inflow cycles that make the wattage diverge. Hurm. Maybe the vapor insulates the water as it rises? Pv=nrt can get insane P via n and not T, which is an error I made above. $\endgroup$
    – Yakk
    Oct 10, 2019 at 1:46

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?

  • $\begingroup$ I don't know how I overlooked your post last time I read through this, but that's some good input building off of Stephen's numbers. I have edited my question with some of Stephen's numbers and some more research of my own. As with Stephen, I'd invite you to revisit my post and see what you think, as I think the new info I provided will help you help me. Please let me know. $\endgroup$
    – Koborakai
    Nov 19, 2019 at 23:42

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 ;) $\endgroup$
    – user26494
    Oct 9, 2019 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, 2019 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, 2019 at 22:44

Well it will be loud.

No one has mentioned so far is how loud this thing is going to be. The second you start boiling water in a continuous stream deeper than about an atmosphere (10.2 m) you need to be aware that you will be creating a choked flow scenario. That means water reaching the surface at supersonic velocities. Any supersonic boom will have a volume of 191 dB, and given the size of your fireball in comparison to the thicker parts of the atmosphere, this sound will dissipate as a line source rather than a point source. Line sources decrease with the square of distance rather than the cube. To get to the threshold of pain at 130 dB you will need to be 335 km away from the center of the ball, the continuous hearing damage limit of 85 dB will require you to be about 4500 km away.

  • $\begingroup$ Good point. I didn't think of that. Ouch, so I guess in my example location in the South China Sea, a lot of Southeast Asia is in painful ear-shattering distance (Philippines especially), and even more is in gradual hearing loss distance? 4500 km reaches all the way north to Mongolia, west to India, and south to Australia. That's a lot of "going deaf" area. The most significant barrier I can see in this range is the Himalayas. They would offer significant protection from the severe loudness, correct? What about lesser barriers, like smaller elevation changes, forests, jungles, and such? $\endgroup$
    – Koborakai
    Nov 20, 2019 at 0:10
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    $\begingroup$ There are defiantly ways to reduce the effects. The above does not consider dissipation for example, only the spreading of energy. Soft ground could absorb some of the sound energy, while sudden walls of hard material such as mountains could reflect it. Gradual changes in elevation however are only likely to funnel it. The atmosphere halves every ~3000m, and sound energy will be distributed by mass. Anything smaller than 3km is not going to have much effect for absorption while a 1500m mountain range (above base, not sea level) will reflect about 3dB. $\endgroup$
    – XRF
    Nov 21, 2019 at 23:59
  • $\begingroup$ I did some digging and the eruption of Krakatoa has comparable loudness (180db, or even 300db at its loudest): en.wikipedia.org/wiki/1883_eruption_of_Krakatoa And by a potentially useful coincidence it's in the same region as my example. Going by what you say, then my sphere would basically be like Krakatoa erupting constantly? But launching water/steam and not earth/ash? Overall studying this eruption should give me a good idea of the constant effects of the sound of my sphere, right? I was worried at first, but I actually feel like this could make my world even more interesting. $\endgroup$
    – Koborakai
    Nov 25, 2019 at 3:38

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