19 Feb 17
Originally posted by twhiteheadAre you quite sure about that? Uranus's axis of rotation is so skew that the pole is usually oriented towards the sun; so Uranus is more sort of rolling round the sun, than spinning like a top round the sun. So, if its moons were orbiting round its equator, then they might never eclipse. Just a thought experiment...
Eclipses occur with all moons. It is a geometric necessity.
19 Feb 17
2 edits
Originally posted by moonbusNo, that is incorrect. If a planet was exactly tilted over by 90 degrees then its north pole would face the sun then the equator then the south pole then the equator and so on as the year progresses. (Uranus has a year of 84 earth years, so in a long lifetime, both poles receive sunlight at least once.)
Uranus's axis of rotation is so skew that the pole is usually oriented towards the sun;
19 Feb 17
1 edit
A moons orbit necessarily coincide with the line between the sun and the planet exactly twice a year - without fail. Whether or not the moon in question is in the right place a the right time to cause an eclipse is a matter of chance. In addition, there is the possibility of an eclipse of the moon (the moon passing through the planets shadow).
The timing does not have to be exact for moons close to their planets. The eclipses we see are usually either partial eclipses or do not pass exactly over the 'earth-sun' line. A 'perfect' eclipse - with the centres of all three bodies lined up - is a very rare event indeed.
19 Feb 17
1 edit
Originally posted by joe shmoNot so.
Here is an orbital "geometry" that would never produce an eclipse. Circular orbit. Radial planetary/moon axis of rotation.
I am not certain what you mean by 'radial' here, but I am guessing that you are thinking of a vertical plane at a tangent to the planet-sun line.
Keep in mind that moon orbits do not rotate as the planet orbits the sun so what is a tangent at one time of year, point to the sun a quarter year later.
All possible orbits allow for eclipses. Its a geometrical necessity.
19 Feb 17
16 edits
Originally posted by chaney3That is a moronic baseless assertion because that is extremely clearly false to anyone here educated in the basic science. You could for example have the distance between the moon and the Earth 60% greater and we humans will not die as a result. Why would that kill us?
You cannot adjust any distance of sun, moon or earth.....to discuss an eclipse, because it would destroy human life in the process. .
Let me educate you in just a bit of science;
The moon's average distance (per orbit) from the Earth has been steadily increasing since the birth of the moon and for many millions of years and is continually doing so and we are not dead. In fact, The average distance (per orbit) the Earth is from the sun has changed many times and is still changing and life is still here.
Thus if as you say changing any distance would destroy human life, we all will be already destroyed long ago because those distances have been continuously changing and are still changing right now, and yet we are still here and clearly still alive. How do you explain that?
If those distances were all perfect and stayed perfect for human life then that logically implies they wouldn't change and yet they have therefore they are NOT perfect; no evidence there of your Goddidit/'design' then! Quite the opposite; why doesn't your god keep those distances perfect?
19 Feb 17
Originally posted by humyYou cannot move the moon 100,000 miles further away from earth, as you are implying, without dire consequences.
That is a moronic baseless assertion because that is extremely clearly false to anyone here educated in the basic science. You could for example have the distance between the moon and the Earth 60% greater and we humans will not die as a result. Why would that kill us?
Let me educate you in just a bit of science;
The moon's average distance (per orbit) fr ...[text shortened]... r Goddidit/'design' then! Quite the opposite; why doesn't your god keep those distances perfect?
I think you are wrong.
19 Feb 17
3 edits
Originally posted by chaney3Such as what? Give any example. And why would we die from it?
You cannot move the moon 100,000 miles further away from earth, as you are implying, without dire consequences..
And how can those distances be always perfect for human life when they are continuously changing? -this is clearly evidence against your god and is certainly not evidence for 'design'.
19 Feb 17
Originally posted by chaney3The moon is known to to be receding from Earth at about 4 cm per year. Call it an inch and a half. 8 years per foot. About a mile in 40,000 years. A thousand miles in 40 million years and about 4 billion years it will be 100,000 miles further out but long before that, Earth will be toast, literally since the sun will have long before that run out of first fuel and start burning it's trash and it gets hotter and bigger and eventually it will be as big as the entire Earth orbit, like 93 million miles radius. So there will be dire consequences but not from the moon. Stars burn out, run out of various levels of fuel till it is filled with iron which cannot take part in fusion reaction, iron is star poop and it will do a BIG poop called nova maybe or just collapse when it runs out of fuel at which point the engine stops and the star collapses very quickly and a big boom entails which, if Earth hadn't been scorched before, it will be when that happens.
You cannot move the moon 100,000 miles further away from earth, as you are implying, without dire consequences.
I think you are wrong.
19 Feb 17
Originally posted by sonhouseHumy was suggesting an immediate move of 100,000 miles, right now. It would be deadly.
The moon is known to to be receding from Earth at about 4 cm per year. Call it an inch and a half. 8 years per foot. About a mile in 40,000 years. A thousand miles in 40 million years and about 4 billion years it will be 100,000 miles further out but long before that, Earth will be toast, literally since the sun will have long before that run out of first ...[text shortened]... nd a big boom entails which, if Earth hadn't been scorched before, it will be when that happens.
He did not mean 4cm per year, or in a billion years.
Big difference. The moon is exactly where it needs to be for human life. Design.
19 Feb 17
Originally posted by chaney3I hate to be the one to break it to you, but there is a few billion years of life already here and if the moon were to be picked up in a giant Earth sized spaceship and carted away at the speed of light, there would be only lessening of tides, which would not go to zero because the sun causes some tides also so the ones that would miss it the most would be humans as a romantic symbol.
Humy was suggesting an immediate move of 100,000 miles, right now. It would be deadly.
He did not mean 4cm per year, or in a billion years.
Big difference. The moon is exactly where it needs to be for human life. Design.
There would be no other consequences. At least immediately. Earth might start tilting over slowly but that would be about it. Life on Earth would adjust, many life forms may die but life in general is very robust and would recover.
20 Feb 17
1 edit
Originally posted by twhiteheadTo avoid eclipses I think one would have to cook up a curious resonance: a moon whose orbital period about a planet equals the planet's orbital period about its sun.
Not so.
I am not certain what you mean by 'radial' here, but I am guessing that you are thinking of a vertical plane at a tangent to the planet-sun line.
Keep in mind that moon orbits do not rotate as the planet orbits the sun so what is a tangent at one time of year, point to the sun a quarter year later.
All possible orbits allow for eclipses. Its a geometrical necessity.
EDIT: I'm having a hard time coming up with such a setup that would be stable. Jupiter and Saturn have tiny little moons with orbital periods up to 3 or 4 years, which doesn't come close to the orbital periods of the planets themselves. A body situated where it would nominally take 12 years to revolve around Jupiter would be so far away from the planet that it would likely be perturbed out of orbit in short order.