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Durakken
2012-Oct-03, 06:26 AM
On a conworld forum it was asked (cleaned up a lot) What would a habitable planet with no tides look like?
At first I thought it was silly... but then I realized that it might be physically possible.

Step 1) Remove all other bodies in the system besides the planet and the star.
Step 2) Tidally lock the planet with the star.
Step 3) Assuming that the habitable surface is equivalent to Earth's habitable surface adjust the size of the planet.
Step 4) Move the planet to an orbit where the the heat from the star creates a "habitable" temperature on one side of the planet.

What would this planet be like?

side note: Given that removing all other bodies would indicate outside interference more than likely, it should be noted that we are just going to assume that the planet auto-magically gains a more modern earth-like surface to start with, rather than trying to figure out how water and oxygen got there.

eburacum45
2012-Oct-03, 07:10 AM
On a tidally locked world there would be a distinct and permanent gradation between the hottest part of the planet, facing the local sun, and the coldest part, facing away. You might find the most hospitable part of the planet occurs at the edge of the planet, where the sun appears permanently on the horizon. But if the planet is a bit cooler, you could find that the subsolar point, directly beneath the sun, would be the only habitable spot.

Winds would be a problem, too, as the atmosphere tries to distribute the heat from the sunny side to the cold side. Another factor would be the spin of the planet; tidally locked planets do rotate once a year, and if the star is very dim then the year would be short, and this means coriolis efects and other rotational effects will change the wind patterns. In the extreme case this could spread the warmest point quite considerably around the equator as the atmosphere rotates.

A wiki segment about a fictional locked planet here
http://en.wikipedia.org/wiki/Aurelia_and_Blue_Moon#Aurelia
and Orion's Arm's take on the subject
http://www.orionsarm.com/eg-article/4922e224a740d

Ara Pacis
2012-Oct-03, 07:33 AM
You'll also need the planet to have no axial tilt, otherwise I think the poles would experience tides over the course of a revolution.

You could have both sides habitable. If you have enough thermal transport in the atmosphere and hydrosphere, then both sides would moderate from the extremes, somewhat. If it's far enough from the star to have polar ice (which would require land above or near the ocean surface) then that might help moderate the warm side too. A lot of it will depend on ocean currents.

Cael0
2012-Oct-03, 04:12 PM
While we're being purely hypothetical, what if the moon of this hypothetical planet was positioned in such a way that the tidal forces of the moons counteracted the tidal forces of the star?

This way, the tidal forces would depend not on the planet's spin or orbital period, but on the orbital period of the planet's moon, right?

Durakken
2012-Oct-03, 05:07 PM
While we're being purely hypothetical, what if the moon of this hypothetical planet was positioned in such a way that the tidal forces of the moons counteracted the tidal forces of the star?

This way, the tidal forces would depend not on the planet's spin or orbital period, but on the orbital period of the planet's moon, right?

There is no moon ^.^ The Moon, in conjunction with the Sun is what causes the tides in the first place


Also, I doubt that the twilight areas of the planet would be the best place to live considering they'd likely have massive hurricanes caused by the massive air pressure difference

IsaacKuo
2012-Oct-03, 06:25 PM
There's another way for a habitable planet to have no tides. No oceans means no tides! So, a "desert" planet or a "snow" planet, with only small lakes of liquid water would have no tides. Also, a planet with only underground liquid water could lack tides, if the pockets of liquid water are "lakes" rather than "oceans".

Even if there's a tidal force which wants to slosh the water around, there's nowhere for the water to go if the only bodies of water are relatively small in extent. It's like the difference between a large baking pan filled with a little water and an ice cube tray filled with a little water. If you tilt the baking pan a little, this will cause big vertical "tides". If you tilt the ice cube tray a little, the water just stays in place with practically no vertical displacement.

grapes
2012-Oct-03, 09:08 PM
There's another way for a habitable planet to have no tides. No oceans means no tides! So, a "desert" planet or a "snow" planet, with only small lakes of liquid water would have no tides. That's a good point. Even large lakes do not have appreciable tides, small seas as well.

chornedsnorkack
2012-Oct-03, 09:10 PM
That's a good point. Even large lakes do not have appreciable tides, small seas as well.

The smallest sea that does have appreciable tides (it is checked, they are locally generated) is Red Sea. Mediterranean also has local tides.

Ara Pacis
2012-Oct-03, 11:04 PM
While we're being purely hypothetical, what if the moon of this hypothetical planet was positioned in such a way that the tidal forces of the moons counteracted the tidal forces of the star?

This way, the tidal forces would depend not on the planet's spin or orbital period, but on the orbital period of the planet's moon, right?

I don't think you could have such a moon, as it would have to always be at right angles, which means it has a very slow orbital velocity, which means it has to be very far away and have a high mass and I don't think that such an orbit would be stable, but I'm not sure. Plus, such an arrangement might be more properly considered as a double planet, instead of a planet-and-moon. You might try putting a moon or companion-planet in an L4/L5 location, but that wouldn't perfectly offset, since it would be towards the sunward side by 30 degrees and be massive.

Ara Pacis
2012-Oct-03, 11:06 PM
There's another way for a habitable planet to have no tides. No oceans means no tides! So, a "desert" planet or a "snow" planet, with only small lakes of liquid water would have no tides. Also, a planet with only underground liquid water could lack tides, if the pockets of liquid water are "lakes" rather than "oceans".

Even if there's a tidal force which wants to slosh the water around, there's nowhere for the water to go if the only bodies of water are relatively small in extent. It's like the difference between a large baking pan filled with a little water and an ice cube tray filled with a little water. If you tilt the baking pan a little, this will cause big vertical "tides". If you tilt the ice cube tray a little, the water just stays in place with practically no vertical displacement.

The planet would still have tides without water, since the lithosphere would also feel it.

If it's water basin effects that one is concerned with minimizing, then yes, reducing the size and depth of basins and their interconnectedness would go far. The Gulf of Mexico has minimal tides for this reason.