Teleportation range limits and epic teleportation

[Loren Pechtel]

Where things get really interesting and exotic is when you start to consider objects like an Earth-sized "moon" of a brown dwarf, or something similar. How about a world where life is possible thanks to the warm body nearby, but said body doesn't actually put out any light as such? Can you say "illithid" and "aboleth," boys and girls? I knew you could!

If it's cool enough not to emit any visible light it's also too cool to raise the planet to habitable temperatures.

Furthermore, the cooler the central body the closer the orbit has to be to get enough warmth. Energy goes at the square of distance but tides go at the cube of distance--thus the smaller the body the greater the tides.

By the time you're down to red dwarfs the tidal problems become severe, you get tidal locking which makes it much harder to have an inhabitable world. Go smaller still and you had better also have a year that matches the day length of the star or you're going to be spiraling pretty fast.


However, there's another way you could have an inhabitable world without a visible star: instead of a brown dwarf how about a degenerate mass? While it would still glow I'm thinking of tidal heating rather than radiative heating.

Consider a world: It's in an elliptical orbit around a degenerate body. The atmosphere is opaque due to volcanic dust. The oceans are small which is good as the tides are incredible. All land masses are thin, enlongated masses oriented to let the tides pass by. (This is the result of erosion, the tides will smash down anything that doesn't present a narrow cross section.)

Even the ground flexes greatly due to the tide although this isn't too obvious as it doesn't flow. The flexing produces a lot of heat, though--that's what keeps the planet inhabitable. Each flex causes volcanoes to spew lava but it also brings water--the result is clouds of ash and steam. The steam quickly recondenses and rains out most of the ash but some of it is thrown high enough to avoid being rained out--the result is an opaque stratosphere but the troposphere remains breatheable if you're away from the volcanoes.

The lands around the volcanoes are no-go zones due to the ash (although with enough magic you can survive there), the spotty reports people have of the volcano lands have led to the belief that they are hell.

Boat traffic is out of the question (nobody has even invented water-borne transport), inter-island transport is by flight or magic only--you can have very different cultures and populations only a few miles away.

There's obviously no photosynthesis, life's energy source is chemically powered bacteria. (Think of the deep ocean vent communities of Earth.)

 

[Loren Pechtel]

[MENTION=463]S'mon[/MENTION] - I just went delving in my older rule books and the 3E and 3.5 SRD text for Teleport is basically the same as that of Pathfinder, there is no mention of needing a solid surface onto which you must teleport. 2E however, does have the statement that:

I'm pretty sure that was about retaining the risk of teleporting low. Otherwise you could do so in complete safety by teleporting high over adequate padding.

 

[paradox42]

If it's cool enough not to emit any visible light it's also too cool to raise the planet to habitable temperatures.

Incorrect. Heat is infrared; brown dwarfs emit plenty of that. Critters from a brown-dwarf world would likely be able to see infrared pretty well, in fact, since that's the majority of their sun's output. Plant(like) lifeforms on the world would probably be black, to our eyes, so as to absorb the maximum possible EM radiation.

Furthermore, the cooler the central body the closer the orbit has to be to get enough warmth. Energy goes at the square of distance but tides go at the cube of distance--thus the smaller the body the greater the tides.

By the time you're down to red dwarfs the tidal problems become severe, you get tidal locking which makes it much harder to have an inhabitable world. Go smaller still and you had better also have a year that matches the day length of the star or you're going to be spiraling pretty fast.

No argument. Habitable planets around bodies like a red dwarf or brown dwarf would only be habitable thanks to having an atmosphere capable of creating convection around the planet so as to distribute the heat more evenly around the surface. They'd have to be tidally locked in order to be within the habitable zone at all. But astronomers looking at exoplanets these days have been running plenty of simulations for how a tidally-locked world around such a star (they haven't considered brown dwarfs, but given the existence of Titan it's only a matter of waking up to the possibility really) could exist and keep liquid water at the surface. That was the answer they came up with- if the atmosphere is thick enough, then convection patterns in the atmosphere distribute the heat and make a more habitable planet. The weather probably isn't very interesting by our standards, since it'd constantly flow in about the same directions, but it can be done.

However, there's another way you could have an inhabitable world without a visible star: instead of a brown dwarf how about a degenerate mass? While it would still glow I'm thinking of tidal heating rather than radiative heating.

Consider a world: It's in an elliptical orbit around a degenerate body. The atmosphere is opaque due to volcanic dust. The oceans are small which is good as the tides are incredible. All land masses are thin, enlongated masses oriented to let the tides pass by. (This is the result of erosion, the tides will smash down anything that doesn't present a narrow cross section.)

Even the ground flexes greatly due to the tide although this isn't too obvious as it doesn't flow. The flexing produces a lot of heat, though--that's what keeps the planet inhabitable. Each flex causes volcanoes to spew lava but it also brings water--the result is clouds of ash and steam. The steam quickly recondenses and rains out most of the ash but some of it is thrown high enough to avoid being rained out--the result is an opaque stratosphere but the troposphere remains breatheable if you're away from the volcanoes.

The lands around the volcanoes are no-go zones due to the ash (although with enough magic you can survive there), the spotty reports people have of the volcano lands have led to the belief that they are hell.

Boat traffic is out of the question (nobody has even invented water-borne transport), inter-island transport is by flight or magic only--you can have very different cultures and populations only a few miles away.

There's obviously no photosynthesis, life's energy source is chemically powered bacteria. (Think of the deep ocean vent communities of Earth.)

Nice idea! Life around a neutron star; I like that. Might work for a black hole too, though those usually have accretion disks and I'd think that would screw things up a bit. Of course, accretion disks put out lots of radiation, so perhaps that would just tend to make the black hole more of another star.

 

[Loren Pechtel]

Incorrect. Heat is infrared; brown dwarfs emit plenty of that. Critters from a brown-dwarf world would likely be able to see infrared pretty well, in fact, since that's the majority of their sun's output. Plant(like) lifeforms on the world would probably be black, to our eyes, so as to absorb the maximum possible EM radiation.

I said it's too cool to raise the planet to a habitable temperature, not that it emitted no heat.

Lets say the brown dwarf is "glowing" at 500 degrees F. Where does the planet have to be in order to stay above freezing?

That's about 1/2 the temperature of the surface of the star. (You have to do this on an absolute scale--Kelvin or Rankin.) Emitted energy goes up at the 4th power of temperature. 1/2 the temperature = 1/16th the energy. Therefore the star must comprise 1/16 the sky of the planet. Obviously half the sky is night, this means the star must be 1/8th the day sky.

Now, you could orbit close enough to a planet to do that but stars don't have anything like a defined surface, you're going to be in it's outer atmosphere and you'll spiral in from drag.

No argument. Habitable planets around bodies like a red dwarf or brown dwarf would only be habitable thanks to having an atmosphere capable of creating convection around the planet so as to distribute the heat more evenly around the surface.

They'd have to be tidally locked in order to be within the habitable zone at all. But astronomers looking at exoplanets these days have been running plenty of simulations for how a tidally-locked world around such a star (they haven't considered brown dwarfs, but given the existence of Titan it's only a matter of waking up to the possibility really) could exist and keep liquid water at the surface. That was the answer they came up with- if the atmosphere is thick enough, then convection patterns in the atmosphere distribute the heat and make a more habitable planet. The weather probably isn't very interesting by our standards, since it'd constantly flow in about the same directions, but it can be done.

I don't understand how they avoid the atmosphere freezing out on the dark side.

Nice idea! Life around a neutron star; I like that. Might work for a black hole too, though those usually have accretion disks and I'd think that would screw things up a bit. Of course, accretion disks put out lots of radiation, so perhaps that would just tend to make the black hole more of another star.

If the atmosphere is thick enough it can shield the planet from the radiation.

Note that you'll get something of a disk around a neutron star, also. It's just not as energetic.

Any degenerate body with a nearby planet is going to be hot (or have a hot disk at least) due to infalling matter. It's just they're going to be small enough not to contribute much in the way of light to the planet.

 

[paradox42]

I said it's too cool to raise the planet to a habitable temperature, not that it emitted no heat.

Lets say the brown dwarf is "glowing" at 500 degrees F. Where does the planet have to be in order to stay above freezing?

I don't know offhand, nor do I particularly care. The fact is, every body with a temperature above the boiling point of water has a habitable zone, it's just a question of whether a body can exist within said zone in the first place. And effects such as planetary atmosphere and others can change where the "effective" habitable zone lies.

I have a lot of time to read at work, and I spend much of it surfing the web- links about exoplanets have been some of my favorite targets in recent years.

I don't understand how they avoid the atmosphere freezing out on the dark side.

Convection, put simply. Convection really does make all the difference. An atmosphere is not a static thing, it's a fluid body that's constantly in motion and changing. That's as true on Titan as it is here, to use a handy example from our own system; you don't see Titan's atmosphere freezing out do you? Sure, it rains methane, but the atmosphere remains gaseous- and quite thick too, given the moon's low gravity.

But try some of these links on for size. This is just a selection of stuff I found with a quick Google search; there's been a lot more published on topics like this recently.

Link 1

Link 2

Link 3 (PDF) (This one's an actual scientific paper published in 1998 or 99, as far as I can tell.)

I'll also quote from the third link, the paper:

Recent work by Haberle et al. (1996) and Joshi et al. (1997) has shown that for a planet receiving insolation equal to that on Earth (Ie), a 100 mb pure CO2 atmosphere would ensure sufficient heat flux to the dark side of a SRP to preclude atmospheric collapse. For a 1500 mb pure CO2 atmosphere and 0.8 Ie, liquid water (essential for life as we know it) could exist over much of the planet. On a planet with intense volcanism or plate tectonics, it is likely that the atmospheric pressure of CO2 (pCO2) representing a balance between CO2 outgassing and drawdown of CO2 through weathering processes, will be controlled by a carbonate-silicate-cycle (Walker et al., 1981).

Note that you'll get something of a disk around a neutron star, also. It's just not as energetic.

True enough.

Side thought on that point; did you read about the "diamond planet" recently found in orbit around a neutron star, apparently the end result of a gas giant that had its atmosphere stripped away by the supernova? No way such a body could have life as we understand it of course, but wow would that be a cool setting for a world of Earth/mineral elementals!