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The lack of requirement for an inner ear in a non-rotating planet.

IF and it's a big if, we were on a non rotating yet orbiting planet the dinosaur would not have needed an inner ear. It's only on a rotating planet such an instrument of balance would be needed.Once again with a broad brushstroke, how else could creatures so massive move about a rotating planet or even stand. And if orbital conditions aren't so different how is the elephant so tiny in comparison as the largest land mammal. Yet in the sea where body mass is bouyed i doubt that whales have ever been much larger. So back to the bone collecters, if other bones and configurations happen in limbs etc why not an inner ear. And don't shout at me if it's illogical, but i feel it also a point of not shutting your own minds up in the same sense of self rightousness as the theists. Just a layman asking questions if one kind of evolving and adaptation, if on form why not the other.

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Permalink Reply by SecularCortex13.x on October 16, 2009 at 7:36pm

oh the aeons

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Permalink Reply by david hartley on October 23, 2009 at 1:49am

sorry for the late reply but you know how the aeons fly when your enjoying yourself.

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Permalink Reply by Cara on October 16, 2009 at 11:58pm

I read somewhere (A Brief history of Time, I think) that in order to have the life supporting atmosphere that we have, we have to rotate at just the right speed. If this is correct then we must have always had a rotating earth, or at least while life was flourishing.

Interesting to think about how and when the inner ear evolved. I cannot spin circles on land with out getting sick, yet in water I do not have the same problem. I guess it's because it almost simulates weightlessness.

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Permalink Reply by david hartley on October 18, 2009 at 9:47pm

Hello Tina It's just the problem of objects on the surface of a globe, I know how complicated but would'n't have a clue of the equations. I'm still whinging on as we accept it was one land mass but have'n't thought of what the couterbalance must have been for such a large land mass. I don't buy just water not stable enough over such a large body of liquid. So it must have been ice, which in itself could possibly be too unstable for a rotating planet, hence in a sense periodic ice ages in a post rotational state. I do love musing and questioning and i feel that what i've said has some logical symetry, so if i'm wrong i'm doing some of the sums the right way

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Permalink Reply by Jared Lardo on October 18, 2009 at 10:36pm

Nothing ever falls over because of the planet's rotation. They fall over because their center of gravity was moved out from being over their support base. I bring up falling down because it is bad and its badness led to the evolution of the sense of balance to prevent it. Since gravity does not require a body to be rotating and gravity is the source of falling (Intelligent Falling advocates can suck it), the inner ear would still have developed on some non-rotating planet.

Of course, since day and night would be as long as half the year, some far more interesting developments would have to arise for stuff to stay alive under that condition for very long.

As for underwater things, I take it that you haven't dived into the deep end of a pool. It's all about pressure, pain, and bodily damage. Due to taking damage to one's body and feeling pain being selected against, stuff that goes deep into water has a selective pressure on its "kind", so to speak, to not have that sensitive inner ear anymore.

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Permalink Reply by david hartley on October 23, 2009 at 4:27pm

It was never a question of gravity really but one of acceleration and balance, tied in with ideas of what split the original singular land mass. If sudden acceleration was the cause, and this is an area of the discussion nobody has touched upon, what could have been both the long and short term effects upon species extinction and evolution. A hypothosis in it's infancy.

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Permalink Reply by Jason Spicer on October 24, 2009 at 2:17pm

The Coriolis Effect at the Earth's surface is extremely small compared to other forces. Over large scales, it has an effect (hurricanes spin one way in the northern hemisphere and the opposite way in the southern hemisphere), but at the scale of a human (or a bathtub) other effects almost always swamp it. The idea that drains reverse the direction of swirl when you cross the equator is not realistic, because water in such situations is almost never calm enough (absolutely still for 24 hours with a uniform temperature) for the effect to be noticed.

Rotating or not, an animal that moves quickly needs a mechanism such as the inner ear to keep tabs on which way is down, not to counter the nearly undetectable effects of the planet's rotation. Unless a planet is rotating so fast that centrifugal force is a significant fraction of the acceleration of gravity, it just wouldn't be noticable to an animal on the surface. People standing on Earth's equator weigh slightly less than those standing on the poles, but the difference is only one twentieth of one percent (0.05%).

In any case, I'm not sure what a non-rotating planet would look like. The moon rotates as it orbits the Earth, even though it always keeps one face towards the Earth. It just takes 28 days to rotate, the same time as its orbit. If it faced the sun instead, it would take a year to rotate, but it would still be rotating. If it faced the galactic center, it would take 250 million years to rotate, but it would still be rotating. The only real question is, rotating with respect to what, and how fast?

The usual explanation for the breakup of pangea (and the supercontinents before it) is plate tectonics, driven by the internal heat of the Earth causing convection currents which push the plates sideways as the magma rises and falls. As far as I know, there is no reason to believe that the Earth's rotation has increased or decreased dramatically at any one time in the past. It started because the stuff the Earth was made of was already spinning, and the Earth has conserved that angular momentum, very gradually slowing its rotation over billions of years because of tidal drag and other effects.

Other bodies impacting the Earth would add or subtract from its angular momentum, but impacts large enough to make a significant change in angular momentum seem to have stopped before the formation of oceans. So, no, it's not likely that the continents were pushed around by a sudden acceleration, and certainly not in evolutionary time (the last 3.5 billion years or so).

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Permalink Reply by Jaume on October 24, 2009 at 4:09pm

The moon rotates as it orbits the Earth, even though it always keeps one face towards the Earth. It just takes 28 days to rotate, the same time as its orbit.

It's a bit misleading to say that tidal locked satellites 'rotate' (assuming you mean, rotation around their own axis). Imagine a non-rotating moon moving in a straight line before being caught in the Earth's gravitational field. It would still present the same 'front' and 'rear' to its new natural path (an orbit), just like a car moving on circular racing track. The car 'orbits' around the track's center, but does it 'rotate', although it always shows the same side to people in the center, like the moon does to the Earth?

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Permalink Reply by Jason Spicer on October 24, 2009 at 9:58pm

Jaume, John D has it right. Which is just and fitting, him being GOD and all. A non-rotating moon captured into an orbit would not always present the same face to the planet it started orbiting. It would retain its angular momentum of zero while orbiting, which would mean its whole surface would be visible from somewhere on the planet once during each orbit. From the planet, it would seem to be rotating, but only because it's moving around the planet. A tidally locked satellite does indeed rotate on its axis once per orbit. The car moving around the race track always presents the same side to the pit crews because it's always turning. If you put a powerful rocket motor on the moon's south pole and pushed the moon up and out of the Earth's gravitational field, the moon would still be rotating around its axis once every 28 days.

It occurs to me that it might be possible to tell if a body is rotating or not. If the acceleration of gravity towards its center of mass is the same at all points on the surface (assuming a uniform density), then it's not rotating. I think. I'm not sure that gravitational effects from other nearby bodies might not throw that off.

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Permalink Reply by Jaume on October 25, 2009 at 6:02am

What about an hypothetical photon following a circular geodesic in a strong gravitational well, then? You might still rightfully claim it orbits around the well, since its path is closed by the curvature of space it moves into, but it doesn't rotate on itself any more than if it was moving in a straight line outside of the gravitational well's influence. It just follows its natural path, a geodesic, because it's the most economical way for it to move from here to there. It does only seem to rotate from the well's perspective.

I see 'orbiting' and 'rotating' as distinct notions here. The latter is subject to relative appreciation (because of the absence of an absolute frame of reference), while the former is not (a circular geodesic - or orbit - will remain circular when viewed from any referential frame). I had a feeling you claimed they're more strongly related than they need to be. Maybe it's just we don't use the same definitions for these words, or more likely we attach different connotations to them.

If you put a powerful rocket motor on the moon's south pole and pushed the moon up and out of the Earth's gravitational field, the moon would still be rotating around its axis once every 28 days.

If you found a way to switch the Earth's gravitational field off long enough for the moon to escape it (give the space a zero curvature), I doubt it would. It would just behave as a car 'forgetting' to turn on the circular track. Maybe I'm wrong on this one, I can't do that kind of maths anymore, but it makes more sense to me at the moment.

It occurs to me that it might be possible to tell if a body is rotating or not. If the acceleration of gravity towards its center of mass is the same at all points on the surface (assuming a uniform density), then it's not rotating. I think. I'm not sure that gravitational effects from other nearby bodies might not throw that off.

Makes sense to me.

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Permalink Reply by david hartley on October 25, 2009 at 9:14am

Are we orbiting and rotating and the moon merely orbiting? That was part of what i was trying to say. By all means correct me if i'm wrong but i thought there was a side to the moon we did not see until satellites brought it into vision????

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Permalink Reply by Jason Spicer on October 25, 2009 at 12:04pm

Jaume, do photons have angular momentum? That seems like an odd idea to me, but I honestly don't know. In any case, I'm fairly certain that if you could switch off the Earth's gravitational field, the moon's angular momentum would be preserved and it would continue to spin at the rate of one revolution every 28 days. I can't think of any reason a sudden lack of a nearby gravitational field should decelerate it's spin.

And David, yes, the moon is spinning. If it weren't spinning at one revolution per orbit around the earth, we'd be able to see all sides of it at least once a month. Think of it as a person walking around another person, but always turning to keep their face to the person in the middle. The person walking around is definitely spinning, because they are presenting their back (and face) to all sides of the room that both people are in. WRT the moon, it presents all sides to the sun every 28 days. One lunar day is 28 Earth days long (about).