My daughter has some questions about planets and moons.?

Question

Does a moon's weight and distance from a planet affect its speed of orbit?

Are there other ways in which a moon's weight and distance from a planet affect it?

If a moon had vegetation and water how would that affect its reflection of sunlight- and would it be seen as a green or blue moon from the planet it orbits?

If a planet has three moons, how could that affect the behavior of the moons in orbit- and would it be possible to estimate how often the moons would be aligned?

How would having three moons affect a planet's ocean and weather systems?

Answer 1

1. Are you talking about the orbital period of the parent or its moon? i'll answer both. the orbital speed of the satelite, (moon), is affected by distance it is from the planet, as well as the parent's mass. the longer the distance, the longer the orbital period, as proven by Kepler's third law. The moon itself hardly affects the orbit of the planet, unless it is a souble planetary system. pluto is a good example. pluto's largest moon, charon, is a little more than half the size of pluto, making the system a "double dwarf planet". because the moon is so big compared to the planet, despite the fact that charon orbits pluto, the gravitational pull of charon does slightly affect pluto's orbit.

2. lets clarify something. when you say "weight" you should be saying "mass". weight is the amount of gravity affecting you. so my weight, on earth, is 120 pounds, because that is how much i am being pulled to earth. my mass, is also 120 because earth's gravity, on the scale, is 1. now if i was on jupiter, which has a gravitational affect of about 2.53, i would weigh more because gravity's affect on me changes, but i still have the same mass, because no matter has been changed in me.

so back to the question, the moon's mass and distance can affect the planet's orbit, but also the planets tidal properties. our moon is a great example. because our moon is fairly large, (5th largest in the solar system), and relatively close to the planet (at about 250,000 miles) it's magnetic properties have affects on our oceans, and our moon causes high tide, and low tide. over the years, earth has become dependent on the moon's orbit. if the moon were to suddenly disapear, the earth would start to wobble because of the rapid change in force.

3. it completely depends on how much of the planet is covered by it. our moon is highly reflective, and if it was covered in water and vegitation, it might a little more relfective. ice water reflects a lot of sunlight, as well as water. land on the other hand, absorbs more light. but on earth, we probably wouldn't notice the change in brightness. for water, we would probably see the wavelength of light the vegitation or water absorbs, and reflects.water reflects blue most times, and vegitation reflects usually green or brown. but like i said, we wouldn't notice a change in the brightness. it also depends on how much vegitation there is.

4. usually planets that have three moons are larger than planets that have one moon. there are some exeptions- mars has two moons and is a lot smaller than earth, but those moon's are also a lot smaller than ours. if earth had three moons the size of the moon we have now, then yes there would be an effect. the moon is about 1/4 the size of earth which would make it considered a double planetary system by some. if we had three more, which is impossible given the circumstances, then the earth's orbit would be more irregular, and possibly more eliptical than it is now. the moons' gravity would be affecting earth so greatly, that the earth would orbit slower. but if the moons were the size of asteroids, nothing big would happen. it is possible to estimate how often they will be aligned. we can use kepler's 3rd law to find the orbital period of all of them, and then estimate at what point their orbits would be aligned.

5. if these three moons are the size of the one now, then the tides and weather systems would be affected a lot more than they are now. we would have higher high tides, and lower low tides, and they would occur more often throughout the world.

Answer 2

Any objects speed of orbit will depend it's distance from the primary and the gravity of the primary.  If the mass of the moon is a large portion of the primary, like the earth/moon system then they each significantly the others orbit.

The change in color would depend on how much water and vegetation were present.  Most moons would not have enough gravity to maintain an atmosphere or water.   The only moons that we know of with an atmosphere are large ones orbiting the giant planets like Jupiter and Saturn.

Multiple moons would cause changes in each others orbits.  If the system is stable the orbits, and the alignments would be predictable.  Jupiter and Saturn have stable systems and multiple moons.

Weather and tides on a primary would depend on the mass and proximity of the moons but they would occur.    When the moons are aligned the tides would be higher at that time.  This happens even when the sun and moon are aligned and produce the highest tides at that time. Tides do have some affect on the weather also.

Doug

Answer 3

Yes the weight and distance effect the orbit as it goes around the planet. Our moon is 1/4 the size of earth, which is the biggest in the inner solar system. Referring to the tides, the planet would have a big problem with rising and falling in the tides. The sun light would be reflected from hitting the water. The moon would appear the way Earth dose in space. If there was more than 1 moon orbiting Earth would have been destroyed if that happened. But to answer a question that you might have later there is 2 known moons that could be inhabited by humans, Europa(Jupiter), Titan(Saturn), and Triton(Neptune). Earth can only have one moon do to the amount of space and the gravitational pull of the planets, and the sun. Vegetation dose not effect the orbit of anything, the obit depends on the mass of the object. The inner planets or terrestrial planets, have rocky surfaces, a mantle and a solid iron core. While the outer planets are made of liquid hydrogen ad helium the two most abundant elements in the universe, and they are thought to have a solid core of rock. The amount of moons in the orbit dose not effect the weather patterns of a planet.

Answer 4

Assuming that a moon's mass (weight is not quite the correct term) is a very small fraction of the body it orbits, then the period of revolution depends almost entirely on the mass of the parent body, and the distance of the moon from the (center of) larger body.

Other effects, if the satellite orbits too close to the parent body, the gravity gradient (difference in gravitational field between inner-most and outer-most points) will literally tear the moon apart.  A little further out, the gravitational gradient produces strong tidal forces which stress and pull the moon, heating  the inside to a molten state, causing massive volcanoes on the surface.

Answer 5

I think your "daughter"(cough) doesnt exist

Answer 6

I think you're 'daughter' (rolling eyes) needs to do her own homework.

Answer 7

The first two questions:

The weight of a moon has no effect on its speed. This was demonstrated by Galileo Galilei, that big and small objects fall at the same rate. He did this by rolling objects down an slope and measuring how long they took to reach the bottom, regardless of mass, all objects fall at the same rate irrespective of their size. Only distance influences the speed of the moon, the closer the faster. The mass of a moon and its distance will influence the tides, the closer and bigger it is, the bigger the tides.

Weather question; I suppose the Moon would look just like the Earth but smaller. However, its atmosphere would be deeper then Earth's, due to the Moon's weaker gravity the atmosphere would spread out, reaching a higher altitude above the Moon's surface. The cloud base maybe 5 miles high. It would also lose its atmosphere at a rapid rate, its lost atmosphere might form a comet like tail, visible when the Moon is just below the horizon.

Last two questions, so called "three body problems" are usually chaotic. However, three moons and a much larger planet means that its not a "three body problem", the orbits of the moons will be stable and regular, in fact they may  form resonances, repeated same cycle over and over of the same moon positions.

Therefor, the effects of the three moons on weather and tides will be predicable, but maybe more extreme depending on the mass and orbital distance of the moons. They could be additive, depending on oppositions (lining up of the moons).

Answer 8

These are good questions.  You should encourage your daughter to keep asking.  My parents did and it made a huge difference in my life.  Both the moon's weight (or really it's mass) and its distance from Earth affect the time it takes to orbit (the period).  Kepler's third law of planetary motion allows us to predict mathematically just how much changing those things changes the period.  Increasing the mass of the moon decreases the amount of time it takes to orbit.  Increasing the distance from Earth will increase the time it takes to orbit.  If the moon had vegetation and water, that would definitely change the reflection of sunlight.  Water would make the moon look smooth and shiney.  Vegetation would absorb light.  The moon would probably look a lot like the earth does now when you look at it from the moon.  The color of the vegetated areas, would depend on what kind of plants they are.  There are different types of chlorophyl, blue, green, and red.  Green is the dominant one here on Earth, but it is possible that blue or red might have ended up being more prevalent on the moon.  So the moon could have blue oceans with red vegetated areas.  If a planet has more than one moon, the equations describing their motion become very complicated and almost impossible to deal with.  It becomes much easier if the masses of the moons are small compared to the mass of earth, and if the moons don't pull on each other much gravitationally.  In that case it would be easy to predict how often they would align.  It would basically be a small version of the solar system...where the mass of the sun is much greater than the mass of the planets and the planets don't interact much gravitationally.  If you have a situation with something like three stars pulling on each other, then the math is horrible to deal with and we have to use computers to approximate solutions.  This is called the many body problem and is still an outstanding problem for both math and physics.  If the moons were massive, then the weather and oceans would be affected.  Tides would certainly be higher.