Planet Earth gets swung away from the solar system by a passing black hole.

Hi there, I love this site. Been lurking for a while. I thought of this scenario at work and am very curious what would happen (just approximately is fine).

So, planet Earth gets swung away from the solar system by a passing black hole.

  1. In what kind of timeframe does the Earth’s atmosphere freeze into a thick layer around the Earth with no external sources of heat? Not necessarily asking for an exact answer, but would it happen in minutes or months?

About how thick would the layer be in its frozen form?

  1. Can planet Earth maintain liquid water indefinitely at the bottom of the ocean from just its own heat that it outputs at its core? (until the planet gets destroyed)

  2. An advanced civilization constructs a dome to live in that can contain an atmosphere, a water cycle and an oxygen cycle (but they can also take oxygen from the frozen atmosphere outside). The heat is generated by a nuclear power plant with an output capacity 10,000 MW. Ignoring other problems and applications of the power plant, how large of an area could such a reactor keep at room temperature assuming perfect energy efficiency and insulation of the dome (just for ease of calculating)?

I am mainly curious if this is something like 10 square km or more like 1000 square km, or even a million?

  1. what other major problems would there be for them? they have invented a light source that simulates the sun, allowing proper photosynthesis and thus the growing of food. So they have food, water that they can “mine” from outside and they can purify their own liquid waste, and oxygen and other atmosphere components that they mined outside. And a large stack of fuel for their nuclear reactor.

  2. would geothermal heat still reach the surface (indefinitely)? since the surface is so cold.

Thanks a lot for your time.


from :

The article suggests a human population could survive for hundreds of years on iceland using the abundant geothermal energy there.

Tangentially relevant story.

I read that popsci article before I made this thread, but there aren’t even any approximate measurements in there (that i would like to know) and the Iceland geothermal warmth comment seems like just a wild guess, or maybe they didnt even take into account that geothermal warmth might not reach the surface anymore.

I also read the “A Pail of Air” story before creating this thread. It’s definitely interesting to think about, but I don’t know about the scientific accuracy of that story.

Great story; zero science.

I think even that is a hopelessly optimistic scenario. Here are some previous threads on the topic:

[POST=7918024]The Sun turns off! How long do we have?[/POST]
[THREAD=611731]How long could humanity survive if Earth were flung out of its orbit?[/THREAD]
[POST=8336056]What Would Happen If The Sun Burned Out?[/POST]

The amount of energy required to drive the hydrosphere and provide all of the “hidden” energy in the food cycle, all of which is powered by the Sun’s gracious largess of visible and ultraviolet radiation, would dwarf any man-made energy production capability. (The same argument, incidentially, demonstrates one reason why “generation ships” to another star system are not feasible using anything like conventional technology.) Tapping geothermal energy and using hydroponic gardens to grow food is a temporary solution, but in addition to not supporting indefinate population growth, it also doesn’t allow that raw materials and natural resources will be consurmed and not replaced in usable form even with the best recycling methods.


Seems to me that a “passing black hole” would not just carry away the earth, but also everything in the solar system. Pulling everything with any mass at all into its gravitational well, then into the event horizon to be consumed, it would totally disrupt all the orbits of everything in orbit around the sun as well ending the sun’s orbit around the Milky Way galaxy. And would consume all this stuff in short order. Not to mention that black holes are thought to exist in galaxy cores, some crazy number of light years away from our system. So this is all pretty moot. Just sayin’.

I fully expected the visitors to cut up the family and use them for food.

There is a super massive black hole at the center of our galaxy, but there are smaller ones all over the place.

That depends on a lot of things like the mass of the black hole, the path it takes through the solar system, and the position of the planets at the time.

You can have a stable orbit around a black hole. Something can orbit indefinitely around a black hole, and never be consumed by the black hole, just like the Earth orbits around the Sun and does not fall into the Sun.

It’s been a long time since I covered orbital mechanics at school, but wouldn’t the timeframe for any changes depend on the speed that our distance from the sun increases?

That’s true, and I was going to bring it up. But if we’re being thrown out of the solar system, it would only stretch those timelines by weeks or months (since the popsci article assumes the sun instantly turns off, rather than a gradual decrease in solar radiation). Small consolation when the end result is the same.

Of course, there’s a chance that our exit trajectory could take us closer to the sun first. Then we’d be cooked first and frozen later.

Man, fk black holes!

Yet another great user name/topic meet-up.

On the subject of that A Pail story, the story mentions that long distance radio doesn’t work because there is no atmosphere to carry radio transmissions around the planet; that’s bullshit right? Radio waves don’t need atmosphere.

Black holes are not unstoppable eating machines, as they’re often depicted. The gravitational field of a black hole, at any given distance, is no different than that of any other object with the same mass. Fundamentally, the only difference with a black hole is that you can get a lot closer to it.

And while it would be possible for a passing black hole to eject Earth from the Solar System, and possibly capture us into an orbit around it instead, it could not, except under extremely contrived circumstances, capture the entire Solar System. It could seriously mess up all of the orbits, but when the dust all settled, there would still be at least one, and probably three or four, planets orbiting the Sun.

Line-of-sight radio doesn’t need atmosphere. But line of sight isn’t practical for the ranges at which we routinely use radio, since you’d need absurdly tall towers. Long distance radio depends on the waves bouncing back down to Earth off of layers of the atmosphere.

I know it would throw everything out, but my idea was that the black hole approaches the solar system just close enough to launch earth away but then moves away from earth faster than earth is attracted to it, thus the earth is out of its influence but it is still flung away. It’s never even close to event horizon.

Learned something new.