What if the Sun and the Moon switched places? [Archive] - Wizards Community

What if the Sun and the Moon switched places? [Archive] - Wizards Community

Post/Author/DateTime Post
Strudel_Lumpycakes
12-16-07, 09:32 PM Would the world function the same? So instead of a small moon orbiting the planet, it's a giant ball of fire (the size of our moon), and instead of the solar system orbiting around a star, it would be a giant hunk of rock. Any thoughts on this kind of astrology?
Delfedd
12-16-07, 09:50 PM The world would not function the same, because we would all be dead.
Space_Dragon
12-16-07, 09:56 PM Assuming that the orbiting fireball has all the RL properties of a miniature sun, then yes, we would be dead.
Araes
12-16-07, 09:59 PM Darn, you stole my answer Delfedd.

Generally though, making a wild assumption that the world has Earth-like physics, this simply can't happen.

Problem 1 - If the sun is small enough to not instantly incinerate us all to dust then it dies to a lifeless ball of rock.

Problem 2 - If the moon is as massive as the sun, but a ball of rock, then it collapses under its own weight, and quite likely starts fusing like the sun, thereby becoming a sun.

If you are not following Earth-like behavior as far as the underlying physics go, then you can say whatever you want, because they don't have to behave in any particular way. Have a ball.
Johnathan_Vagabond
12-17-07, 12:34 PM You could create a new element that the moon is made up of, so hard that it does not collapse under the pressure caused by its own gravitational force.

Also, it could be a lunar system with so many other objects that the "moon's" gravity is someone lessened by the control exherted by the numerous smaller objects. While it has enough power to keep these in, their gravity pulling back keeps the moon from collapsing on itself. It would be interesting in some sort of spaces RPG, but I doubt the PCs would notices at all.
Araes
12-17-07, 07:43 PM Well, if you wanted to go that route, I guess you could have your entire large object be made of an incredibly dense material, that is heavy enough fusion is actually an energy absorbing process rather than a creative one.

However, if that is the case, then to make an object with the physical size of our sun, you would probably be verging on the stability limit for black hole creation using our universes' physics (again, a big assumption).

Most stars that have burned off all their heavier elements either explode or collapse into tiny (astromically speaking), super dense planetoids, with the further theory that certain combinations which have enough mass (~20 solar masses) collapse into black holes.

If you had enough super dense mass to try and build something like this, and stacked it all in the same place, you would very likely risk collapse. After a point, its not really about how tough something is, as the classical laws of material strength and physics break down. Note: Not an astrophysicist, only a rocket scientist, so take this with a grain of salt.

On the system of planetoids, since gravity is a D^2 phenomenon, unless the planetoids were literally filling all of the space around single monsterous object, and moving with tremendous velocities at the core, they would have only a minor effect on the internal sphere. In addition, after a certain point, you reach the problem that objects like Dyson's spheres have (note sig) in which gravity within the spherical object is negated by the opposing pulls from the objects on all sides.

This Wikipedia Article on the Divergence Theorem (http://en.wikipedia.org/wiki/Divergence_theorem) more completely explains the problems inherent in this concept using our universe's physics. Again, its just easier to say "magic" and let it be.
Strudel_Lumpycakes
12-18-07, 12:42 AM Thanks to everyone who posted so far. I thought there might be some problems with this idea, but I'm not exactly an astronomical physicist myself (still in high school). The less magic-wand waving I have to do as a DM the better. Oh well, I guess a wizard did it.
Naderion
12-18-07, 01:16 AM You could make the moon a giant gas planet and the world one of it's moons. The real sun is very small in size and far away, so it doesn't generate much light and warmth.
Saturns moon Titan is much like that, practically an almost earth-like planet, exept for a poisenous atmosphere and a temperature of almost -200 °C. I think it's about two or three times the distance from the sun as earth, so the sun would be very small and dim in the sky and it's astrological possible to have stars with the same size and gravity, but much lower heat and light.
And now you put your "large" magical ball of fire in the sky of this moon and it should work like a miniature sun.
Johnathan_Vagabond
12-18-07, 09:00 AM You know what! You could have instead of a single sun that rotated around the "planet/moon" a series of 3 moons on parallel paths at different latitudes. In the middle is your planet that orbits the SUPERMOON. Then, at the equal distances up and down you have two small gas moons, that combusted, and are now tiny suns. They didn't combust because the imploded on themselves, but for some other reason. Meteor strike that caused a spark which ignited the gas moon. As such, you've got the planet on one rotation, and two suns on the other. It gives you alot of free reign with how long and short the days are of your campaign, the can be 24hrs (just be appropriately lining up the revolutions) or they can be whack-zany!
Xiuhcoatl
12-18-07, 09:26 AM Yeah, going by real-life ... the sun would be too small to achieve fusion and would either be sucked up into the Earth or become a tiny Jupiter. The moon would collapse in on itself and achieve fusion--fusing the lighter elements. It would probably default to a Red Giant phase, though, due to the lack of enough lighter elements and an abundance of iron.
questionc
12-18-07, 10:34 AM If the moon were a luminous object, and the sun were not luminous, then...

Each day would last about 27 solar days.
Nights would be longer than days.
Stellar objects currently visible would no longer be visible
The sun would not be visible.

I am not sure how it would affect the seasons.
Araes
12-18-07, 07:46 PM Stellar objects currently visible would no longer be visible
Maybe I'm misreading, but this one wouldn't be totally true, unless you're using stellar to mean Solar System Bodies. That would be true, as all nearby objects are visible from reflected light.

For normal stellar bodies though, as long as they were on the completely opposite side of the planet, and whatever stellar object in the sky they were looking at was self illuminating (like a star), then they should be able to see it as long as its brighter than whatever diffraction light makes it around the edge of the planet.

On the topic of the seasons, I'm pretty sure that there wouldn't be any unless the luminous body orbiting the planet had some kind of strange precessing orbit. The season are normally generated because as the Earth moves around the Sun, different parts of the Earth are more directly pointing at the Sun. If the energy source were instead moving in a fixed path around an immobile object, then you would instead just end up with bands that more heated than others. I think one way to fix this would be to have the planet rotate very slowly on a non-parallel axis to the orbiting body's orbit axis.
Another_Poet
12-19-07, 11:27 AM Here are my suggestions.

1) The "big moon" at the center of the system should be hollow. (None of your characters need to know that, of course). This makes it far less dense and, if it is engineered properly, it will not collapse. This also implies that some deity or advanced race built it, however.

2) The "little sun" orbiting your planet can have a gateway at its center. The gateway leads to the Elemental Plane of Fire. This way, the little sun never cools down, and although it is very hot, it is not as hot as the real-life sun. The planet is safe.

3) Your planet does not need to have drastically different days/nights/etc. As long as the planet is rotating, any given point on the planet will only face the "little sun" for half of any rotation. If a rotation lasts 24 hours then days and nights are not that different in length--but they are going to be "off". (Think of how often you can see the moon in the sky. However often that is will be daytime. That means a lot of 24 hour periods will be almost all "day", and occasionally you will have a very long "night".)

4) The little sun would always be "full" (no waxing/waning). Occasional eclipses though.

5) The big moon would not always be "full". It would have cycles, I imagine.

6) You could still see the big moon at night, and maybe a little bit in the day, as long as it is full or crescent.

7) You could still see stars at night.

ap
JulesCARV
12-19-07, 12:15 PM I remember reading Plato's Phaedo, and he refers to an idea from Anaxagoras in which the sun and the moon are extremely large, but smaller than Earth, objects, which are high in the Earth's atmosphere. They glow from heat which derives from air friction as they hurtle through the air. Plato's point was to attack Anaxagoras, but in truth, most of Anaxagoras's ideas presented in the Phaedo seemed to make a lot more sense than Plato's. Anyway, the idea that the sun and moon are bodies which travel through the atmosphere, glowing red-hot thanks to air friction, struck me as a remarkably elegant idea -- combining an explanation for their light and for their motion into a single cause.

The only question is why they don't slow down, if they're encountering so much fiction. With magic, though, this isn't too difficult a problem.
Artifact
12-19-07, 12:52 PM I don't have anything to add to this thread but I would just like to take the opportunity to say:

My head hurts trying to read and understand some of this stuff! ;) Did I say some, I meant most. I tried to dig into Araes' "Indistinguishable From Magic" thread not long ago and the same thing happened . . . Aargghh! uh . . . Aargghh!

Why do some people have to be so much smarter than others? I mean come on, give a fella a chance here ;). Damn, I just thought of something: I should have never experimented with illicit drugs as a youngster; nope, I should have gone on to higher schooling. Then, I'd be able to join in on a converstation like this and offer something worthwhile. Moral of the story then: Stay in shool. Say no to drugs. And while you're at it, find a real girlfriend.
Roburius
12-20-07, 04:52 PM This is a fun idea. I like the elemental plane of fire idea to power the mini-sun. Here's my take on this:

The "big moon" at the middle of the system would either be invisible (because it would be so far from the small light source) or, if you decide it can be seen, always full. It would have no phases because the light source and the observer are right next to each other.

The day and night would be the same length as each other. If the planet rotates in the same direction as the mini-sun orbits, each day (or night) would be a bit longer than half the planet's rotation. So, say the planet rotates once in 28 hours and the mini-sun orbits once every 28 days (just to make the math easy). In one planetary rotation, the mini-sun will have moved 1/28th of its orbit. It will take the planet an additional hour to catch it (actually a bit more) so the time from one "high noon" to the next will be 29 hours.

This will not vary by time of year and in fact there will be no seasons as we know them. Since the mini-sun orbits at the equator, all days will be the same length. This is probably the biggest, most noticeable change from the real world.

The big moon would rise and set once per day, but for half the "month" it would probably be invisible because it would be in the sky at the same time as the mini-sun and so washed out by the bright light.

Assuming the big moon and mini-sun exerted gravity about the same as our own moon and sun, tides should be similar to Earth's.
fodigg
12-21-07, 02:25 PM I could see a sun that "died" and became a rock-like center of the galaxy, but gave off no heat, and the mages of one of it's surrounding worlds poured all of their effort into forging a "sun orb" that they sent rotating around the planet.

It'd be a tiny speck of a thing, but it would give off the heat and light necessary for life, as it rapidly orbits the planet, simulating a sun.

Post/Author/DateTime	Post
Strudel_Lumpycakes 12-16-07, 09:32 PM	Would the world function the same? So instead of a small moon orbiting the planet, it's a giant ball of fire (the size of our moon), and instead of the solar system orbiting around a star, it would be a giant hunk of rock. Any thoughts on this kind of astrology?
Delfedd 12-16-07, 09:50 PM	The world would not function the same, because we would all be dead.
Space_Dragon 12-16-07, 09:56 PM	Assuming that the orbiting fireball has all the RL properties of a miniature sun, then yes, we would be dead.
Araes 12-16-07, 09:59 PM	Darn, you stole my answer Delfedd. Generally though, making a wild assumption that the world has Earth-like physics, this simply can't happen. Problem 1 - If the sun is small enough to not instantly incinerate us all to dust then it dies to a lifeless ball of rock. Problem 2 - If the moon is as massive as the sun, but a ball of rock, then it collapses under its own weight, and quite likely starts fusing like the sun, thereby becoming a sun. If you are not following Earth-like behavior as far as the underlying physics go, then you can say whatever you want, because they don't have to behave in any particular way. Have a ball.
Johnathan_Vagabond 12-17-07, 12:34 PM	You could create a new element that the moon is made up of, so hard that it does not collapse under the pressure caused by its own gravitational force. Also, it could be a lunar system with so many other objects that the "moon's" gravity is someone lessened by the control exherted by the numerous smaller objects. While it has enough power to keep these in, their gravity pulling back keeps the moon from collapsing on itself. It would be interesting in some sort of spaces RPG, but I doubt the PCs would notices at all.
Araes 12-17-07, 07:43 PM	Well, if you wanted to go that route, I guess you could have your entire large object be made of an incredibly dense material, that is heavy enough fusion is actually an energy absorbing process rather than a creative one. However, if that is the case, then to make an object with the physical size of our sun, you would probably be verging on the stability limit for black hole creation using our universes' physics (again, a big assumption). Most stars that have burned off all their heavier elements either explode or collapse into tiny (astromically speaking), super dense planetoids, with the further theory that certain combinations which have enough mass (~20 solar masses) collapse into black holes. If you had enough super dense mass to try and build something like this, and stacked it all in the same place, you would very likely risk collapse. After a point, its not really about how tough something is, as the classical laws of material strength and physics break down. Note: Not an astrophysicist, only a rocket scientist, so take this with a grain of salt. On the system of planetoids, since gravity is a D^2 phenomenon, unless the planetoids were literally filling all of the space around single monsterous object, and moving with tremendous velocities at the core, they would have only a minor effect on the internal sphere. In addition, after a certain point, you reach the problem that objects like Dyson's spheres have (note sig) in which gravity within the spherical object is negated by the opposing pulls from the objects on all sides. This Wikipedia Article on the Divergence Theorem (http://en.wikipedia.org/wiki/Divergence_theorem) more completely explains the problems inherent in this concept using our universe's physics. Again, its just easier to say "magic" and let it be.
Strudel_Lumpycakes 12-18-07, 12:42 AM	Thanks to everyone who posted so far. I thought there might be some problems with this idea, but I'm not exactly an astronomical physicist myself (still in high school). The less magic-wand waving I have to do as a DM the better. Oh well, I guess a wizard did it.
Naderion 12-18-07, 01:16 AM	You could make the moon a giant gas planet and the world one of it's moons. The real sun is very small in size and far away, so it doesn't generate much light and warmth. Saturns moon Titan is much like that, practically an almost earth-like planet, exept for a poisenous atmosphere and a temperature of almost -200 °C. I think it's about two or three times the distance from the sun as earth, so the sun would be very small and dim in the sky and it's astrological possible to have stars with the same size and gravity, but much lower heat and light. And now you put your "large" magical ball of fire in the sky of this moon and it should work like a miniature sun.
Johnathan_Vagabond 12-18-07, 09:00 AM	You know what! You could have instead of a single sun that rotated around the "planet/moon" a series of 3 moons on parallel paths at different latitudes. In the middle is your planet that orbits the SUPERMOON. Then, at the equal distances up and down you have two small gas moons, that combusted, and are now tiny suns. They didn't combust because the imploded on themselves, but for some other reason. Meteor strike that caused a spark which ignited the gas moon. As such, you've got the planet on one rotation, and two suns on the other. It gives you alot of free reign with how long and short the days are of your campaign, the can be 24hrs (just be appropriately lining up the revolutions) or they can be whack-zany!
Xiuhcoatl 12-18-07, 09:26 AM	Yeah, going by real-life ... the sun would be too small to achieve fusion and would either be sucked up into the Earth or become a tiny Jupiter. The moon would collapse in on itself and achieve fusion--fusing the lighter elements. It would probably default to a Red Giant phase, though, due to the lack of enough lighter elements and an abundance of iron.
questionc 12-18-07, 10:34 AM	If the moon were a luminous object, and the sun were not luminous, then... Each day would last about 27 solar days. Nights would be longer than days. Stellar objects currently visible would no longer be visible The sun would not be visible. I am not sure how it would affect the seasons.
Araes 12-18-07, 07:46 PM	Stellar objects currently visible would no longer be visible Maybe I'm misreading, but this one wouldn't be totally true, unless you're using stellar to mean Solar System Bodies. That would be true, as all nearby objects are visible from reflected light. For normal stellar bodies though, as long as they were on the completely opposite side of the planet, and whatever stellar object in the sky they were looking at was self illuminating (like a star), then they should be able to see it as long as its brighter than whatever diffraction light makes it around the edge of the planet. On the topic of the seasons, I'm pretty sure that there wouldn't be any unless the luminous body orbiting the planet had some kind of strange precessing orbit. The season are normally generated because as the Earth moves around the Sun, different parts of the Earth are more directly pointing at the Sun. If the energy source were instead moving in a fixed path around an immobile object, then you would instead just end up with bands that more heated than others. I think one way to fix this would be to have the planet rotate very slowly on a non-parallel axis to the orbiting body's orbit axis.
Another_Poet 12-19-07, 11:27 AM	Here are my suggestions. 1) The "big moon" at the center of the system should be hollow. (None of your characters need to know that, of course). This makes it far less dense and, if it is engineered properly, it will not collapse. This also implies that some deity or advanced race built it, however. 2) The "little sun" orbiting your planet can have a gateway at its center. The gateway leads to the Elemental Plane of Fire. This way, the little sun never cools down, and although it is very hot, it is not as hot as the real-life sun. The planet is safe. 3) Your planet does not need to have drastically different days/nights/etc. As long as the planet is rotating, any given point on the planet will only face the "little sun" for half of any rotation. If a rotation lasts 24 hours then days and nights are not that different in length--but they are going to be "off". (Think of how often you can see the moon in the sky. However often that is will be daytime. That means a lot of 24 hour periods will be almost all "day", and occasionally you will have a very long "night".) 4) The little sun would always be "full" (no waxing/waning). Occasional eclipses though. 5) The big moon would not always be "full". It would have cycles, I imagine. 6) You could still see the big moon at night, and maybe a little bit in the day, as long as it is full or crescent. 7) You could still see stars at night. ap
JulesCARV 12-19-07, 12:15 PM	I remember reading Plato's Phaedo, and he refers to an idea from Anaxagoras in which the sun and the moon are extremely large, but smaller than Earth, objects, which are high in the Earth's atmosphere. They glow from heat which derives from air friction as they hurtle through the air. Plato's point was to attack Anaxagoras, but in truth, most of Anaxagoras's ideas presented in the Phaedo seemed to make a lot more sense than Plato's. Anyway, the idea that the sun and moon are bodies which travel through the atmosphere, glowing red-hot thanks to air friction, struck me as a remarkably elegant idea -- combining an explanation for their light and for their motion into a single cause. The only question is why they don't slow down, if they're encountering so much fiction. With magic, though, this isn't too difficult a problem.
Artifact 12-19-07, 12:52 PM	I don't have anything to add to this thread but I would just like to take the opportunity to say: My head hurts trying to read and understand some of this stuff! ;) Did I say some, I meant most. I tried to dig into Araes' "Indistinguishable From Magic" thread not long ago and the same thing happened . . . Aargghh! uh . . . Aargghh! Why do some people have to be so much smarter than others? I mean come on, give a fella a chance here ;). Damn, I just thought of something: I should have never experimented with illicit drugs as a youngster; nope, I should have gone on to higher schooling. Then, I'd be able to join in on a converstation like this and offer something worthwhile. Moral of the story then: Stay in shool. Say no to drugs. And while you're at it, find a real girlfriend.
Roburius 12-20-07, 04:52 PM	This is a fun idea. I like the elemental plane of fire idea to power the mini-sun. Here's my take on this: The "big moon" at the middle of the system would either be invisible (because it would be so far from the small light source) or, if you decide it can be seen, always full. It would have no phases because the light source and the observer are right next to each other. The day and night would be the same length as each other. If the planet rotates in the same direction as the mini-sun orbits, each day (or night) would be a bit longer than half the planet's rotation. So, say the planet rotates once in 28 hours and the mini-sun orbits once every 28 days (just to make the math easy). In one planetary rotation, the mini-sun will have moved 1/28th of its orbit. It will take the planet an additional hour to catch it (actually a bit more) so the time from one "high noon" to the next will be 29 hours. This will not vary by time of year and in fact there will be no seasons as we know them. Since the mini-sun orbits at the equator, all days will be the same length. This is probably the biggest, most noticeable change from the real world. The big moon would rise and set once per day, but for half the "month" it would probably be invisible because it would be in the sky at the same time as the mini-sun and so washed out by the bright light. Assuming the big moon and mini-sun exerted gravity about the same as our own moon and sun, tides should be similar to Earth's.
fodigg 12-21-07, 02:25 PM	I could see a sun that "died" and became a rock-like center of the galaxy, but gave off no heat, and the mages of one of it's surrounding worlds poured all of their effort into forging a "sun orb" that they sent rotating around the planet. It'd be a tiny speck of a thing, but it would give off the heat and light necessary for life, as it rapidly orbits the planet, simulating a sun.