Effect of axial tilt on a planet

[BlackSilver]

There was a show on Discovery about the moon's effect on the Earth and how once it leaves it will total screw up the planets tilt and how that will pretty much kill all life on Earth. Can't recall the name of the show.

Little experiment you maybe could try- take a ball put two opposing points on it, put a weight attached to a string to one of those points and place the ball into a pool then swiral the water around the ball. Change the length of the weight on the ball to give it less stablity, and more weight to show greater stability. Swiral further from the ball to show the effects of a larger radius orbit and closer to show a shorter radius.

Its kinda of just an observation thing I suppose, but if you could do it, it might help you to see what your looking for.

Oh, and remember the core of the planet could effect the orbit. Our moon has no or very little iron core, but if it did I wonder what it would do? Emm- interesting thought.

Oh, last thing- I saw a National Geographic program at Costco today it was called- Red.... ah, crap I forgot the title, Red something. If you can find it that could help you out.

 

[GuardianLurker]

this statement is incorrect.

1) earth's axial tilt has had, over the last several billion years, as signifigant an axial tilt as mars does now. life happened anyway!

True. It's also been relatively stable over that time period. Mars has not. The problem in this case is not the amount of tilt, but how much it varies.

2) mars' axial tilt does not vary "wildly."

On a geologic time scale, it does indeed vary wildly. I'll conceed that the other points you mention are *bigger* problems to the formation of life. It is however, doubtful that life as we know it would have developed on a moonless Earth, for many reasons.

The show mentioned above ("If There Was No Moon") isn't the best science special I've seen, but it does cover the basics of this discussion.

 

[tarchon]

If you do end up with one of those players that asks, "Hey, why does winter last so long?", just tell him, "Because the Gods will it." That solves most of these problems.

"How did that kobold get past my AC and kill me?"
"Because the Gods will it."

 

[billd91]

Oh, last thing- I saw a National Geographic program at Costco today it was called- Red.... ah, crap I forgot the title, Red something. If you can find it that could help you out.

Are you thinking of Redshift, current version being Redshift 5 (I believe)?
If that's it, info can be found here: http://www.redshift.de/us/_main/index.htm

 

[Umbran]

Seasons are determined by two things: distance-to-sun and length-of-day. Eccentricity controls the first. Obliquity controls the second. Earth's tilt is severe enough, and eccentricity small enough, that Obliquity is the primary factor.

Not quite accurate.

If an orbit is eccentric enough, it can impact seasonal variation, yes. However, if our solar system is any measure, eccentricity is not an issue, as most of our planets don't have particularly eccentric orbits. Earth's is only a small way from being circular.

Then obliquity becomes an issue. But length of day isn't so important as the intensity of sunlight, which is controlled by the obliquity. The tilt controls the angle of incidence of light upon the ground at a given time of year, and that contols intensity. You're collecting notably more energy per square foot of surface in the summer than in winter.

 

[Umbran]

Err... no formal education on this topic here, but isn't that largely a function of there being far more water relative to land in the southern hemisphere?

Not only is there far more water relative to land, but most of the land is nearer the equator.

Land heats up and cools down more quickly than water, so land that has greater variation in insolation will show greater climate variation. But, in the southern hemisphere, there isn't all that much land outside the tropics, so there's not much land that sees much variation in insolation. Thus, you don't see as much seasonal climate variation.

 

[Goobermunch]

Then why are the days and nights longer in Alaska than in Texas? It's partly based on their location from their equator to the pole and the TILT of the earth. The tilt would affect the length of time that location is exposed to the sun.

Janx

They aren't. As used here, "length of day" refers to a full day (i.e., a 24 hour rotational period). Last time I checked, that's the same in Texas as in Alaska.

What you're referring to is the number of hours the pole is exposed to direct sunlight--also called a day. That is entirely a product of axial tilt.

--G

 

[Ferret]

Just a small hi-jack whilst people in the know are about: How does the 'planet' being a moon effect seasons and day etc, I started a discussion on it before and I don't think the answers were what I wanted. Given that it isn't tidally locked, and its going round a brown giant (?)

 

[JimAde]

I don't claim to be "in the know" but you need some more info. How much heat does the brown giant deliver to the planet? Is it negligible? If it is, then the moon's seasons will depend on its relationship to the actual sun. So if the moon isn't tide-locked I'll assume it has a reasonable-length day (comparable to our own). Does it have axial tilt? How long is its orbit around the brown dwarf? Does its orbit take it into the brown dwarf's shadow regularly?

Like that.

 

[Desdichado]

Just a small hi-jack whilst people in the know are about: How does the 'planet' being a moon effect seasons and day etc, I started a discussion on it before and I don't think the answers were what I wanted. Given that it isn't tidally locked, and its going round a brown giant (?)

I assume you mean brown dwarf, but yeah, as JimAde says, we need more info. Typically, a brown dwarf will have a diameter somewhere in the vicinity of Jupiter, but much more mass. This higher mass means that there will be considerable heat radiation from contraction -- the brown dwarf may glow dully like an ember.

To have the planet/moon not be tidally locked is perhaps a bit tricky, unless it's fairly far away, unless there's some mysterious force that keeps it from being so. Can't imagine what that would be. Keep in mind that there are other hazards too -- Jupiter's large satellites are smack-dab in the middle of an extremely "hot" magnetic field belt and are bathed in radiation almost constantly, making the possibility of life meager at best. To shield it, it would need it's own powerful magnetic field, and the close interaction between them will tend to have their magnetic fields twisted and disrupted. And tidal forces bend the moons something fierce; Io, for instance, is pulled and stretched like a ball of taffy by Jupiter's tidal forces.

But assuming you can get around those obstacles, I think the idea of an earth-like satellite of a giant planet or brown dwarf is a nifty idea and always have. I've also been stymied by the details of it's orbit around its host as well as its host's orbit around the star and what that means in terms of seasons, climate, day and night and a number of other things, though. If someone better in the know than I pops in, I'm extremely interested in that idea too.