What is Earth and moon: Definition and 36 Discussions

The Moon is Earth's only natural satellite. At about one-quarter the diameter of Earth (comparable to the width of Australia), it is the largest natural satellite in the Solar System relative to the size of its planet, the fifth largest satellite in the Solar System overall, and is larger than any dwarf planet. Orbiting Earth at an average distance of 384,400 km (238,900 mi), or about 30 times Earth's diameter, its gravitational influence slightly lengthens Earth's day and is the main driver of Earth's tides. The Moon is classified as a planetary-mass object and a differentiated rocky body, and lacks any significant atmosphere, hydrosphere, or magnetic field. Its surface gravity is about one-sixth of Earth's (0.1654 g); Jupiter's moon Io is the only satellite in the Solar System known to have a higher surface gravity and density.
The Moon's orbit around Earth has a sidereal period of 27.3 days. During each synodic period of 29.5 days, the amount of visible surface illuminated by the Sun varies from none up to 100%, resulting in lunar phases that form the basis for the months of a lunar calendar. The Moon is tidally locked to Earth, which means that the length of a full rotation of the Moon on its own axis causes its same side (the near side) to always face Earth, and the somewhat longer lunar day is the same as the synodic period. That said, 59% of the total lunar surface can be seen from Earth through shifts in perspective due to libration.The most widely accepted origin explanation posits that the Moon formed about 4.51 billion years ago, not long after Earth, out of the debris from a giant impact between the planet and a hypothesized Mars-sized body called Theia. It then receded to a wider orbit because of tidal interaction with the Earth. The near side of the Moon is marked by dark volcanic maria ("seas"), which fill the spaces between bright ancient crustal highlands and prominent impact craters. Most of the large impact basins and mare surfaces were in place by the end of the Imbrian period, some three billion years ago. The lunar surface is relatively non-reflective, with a reflectance just slightly brighter than that of worn asphalt. However, because it has a large angular diameter, the full moon is the brightest celestial object in the night sky. The Moon's apparent size is nearly the same as that of the Sun, allowing it to cover the Sun almost completely during a total solar eclipse.
Both the Moon's prominence in the earthly sky and its regular cycle of phases have provided cultural references and influences for human societies throughout history. Such influences can be found in language, calendar systems, art, and mythology.
The first artificial object to reach the Moon was the Soviet Union's Luna 2 uncrewed spacecraft in 1959; this was followed by the first successful soft landing by Luna 9 in 1966. The only human lunar missions to date have been those of the United States' Apollo program, which landed twelve men on the surface between 1969 and 1972. These and later uncrewed missions returned lunar rocks that have been used to develop a detailed geological understanding of the Moon's origins, internal structure, and subsequent history.

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  1. C

    Maximum safe mass of an asteroid in geostationary orbit

    Summary:: What is the maximum safe mass of an asteroid in geostationary orbit before it causes problems? Hello everyone, If there was an asteroid in geostationary orbit around the Earth, over the Pacific Ocean, what would be the highest mass it could have before it would start having...
  2. artriant

    B Earth & Moon Gravity Gradient: Investigating Its Impact

    Hello everyone, happy holidays! Y/day i googled that question (see title), and i found no clear answer, and I was really suprised, So I had to investigate my self, this is a super basic question, Let me know if i got this right: Earth R: 6,371 km Moon R: 1,737.1 km d1: 384,400 km (center to...
  3. B

    Finding distance between Earth and Moon in gravitational fields

    Here are 2 questions that I have tried to answer and was hoping if these are right ways to go about it? Q1) Find the distance in meters (m) between centre of the Moon and the centre of the Earth, assuming that the Moon moves in a circular orbit with a period of 27.5 days. Take the mass of the...
  4. A

    B Gravitational force of the Earth and Moon

    A person of mass 60kg will weigh around 100N on the moon. This is roughly equivalent to the gravitational force on a 10kg object on Earth. Even if the forces acting on both are about the same, we don't see 10kg objects floating around on Earth whereas a man weighing 60kg can easily float on the...
  5. T

    I Calculating Earth's Orientation and Moon's Position at J2000.0

    Hi there, I am making a very basic model of an earth, moon, sun system in ECEF in C# using the Helix Toolkit and in order to begin transformations according to Earth's rotation, tilt, and orbit, I need a reference orientation/position/time of Earth with respect to the sun and moon. So my...
  6. riveay

    Simulating Jules Verne Earth to the Moon trip?

    Has anybody attempted simulating the trip to the moon described by Jules Verne? I've done a bit of research and found this two posts: https://www.physicsforums.com/threads/showing-deadly-acceleration.909104/#post-5726115...
  7. C

    Universal Gravitation and/or Tidal Force

    Homework Statement ANY HELP IS WELCOMED[/B] The single moon of an Earth-like planet creates tides on the planet that are slowing the planet’s rotation. The planet’s rate of rotation is decreasing at a rate of 7.00 x 10-7 radians/sec/century. The mass of the planet is 6 x 1024 kg, and its...
  8. EternusVia

    Binding energy / mass deficit of Earth-moon system?

    Homework Statement Consider the earth-moon system (whose constituent pats we take to be the Earth and the moon separately). a) Compute this system's gravitational potential energy (in joules) and the mass deficit (in kilograms). The radius of the moon's orbit is 384,000 km, and its period is...
  9. A

    Forces of gravitation of moon and earth + Newtons 3rd law

    In relation to two objects with a gravitational field on them (i.e. a planet and its moon), would there be two pairs of partner forces (the force of gravity exerted from each object and the resulting partner force from each force of gravity)? For example with the Earth and moon: 1. Force of...
  10. Mr. Krang

    Earth and moon barycenter question.

    I was just reading about the barycenter of bodies in space. My question might not make sense but, if we sent hundreds of thousands (or millions) of spacecraft to the moon filled with dirt and rocks could we change the barycenter enough for the Earth to orbit the moon? I know this is a huge...
  11. B

    Gravity force between Earth and Moon from this angle

    Homework Statement Hello the text is in swedish but ill try my best to translate, What it says is: Determine the resultant force on the moon with regard to thr gravitation force from the sun and the Earth when it's in this position shown in the figure [ picture http://m.imgur.com/AfJOVZo ] J...
  12. A

    In which point between Earth and Moon is gravity field zero

    Homework Statement I already searched for solution and i found similar one but I'm still confused. -In which point between Earth and Moon gravity field equals 0 if distance between moon and Earth is 60.3 * radius Earth and mass of the Earth is 81 * mass of the moon. Homework Equations...
  13. A

    What if the Earth and Moon were attached to each-other?

    Hello. My name is Andrew Huerta and I am a comic creator. I am currently doing some research for a comic I'm working on and I'm having a bit of trouble grasping some of the concepts I've created. Basically, what would be the reality of this situation? Like, what would that scenario do...
  14. T

    Space probe between the earth and moon

    Homework Statement The mass of the Earth is Me and the mass of the Moon is Mm. The (center to center) Earth to moon distance is d. a) If a space probe is sent directly from the Earth to the moon, how far from the center of the Earth would the net gravitational force (due to the Earth and...
  15. 8

    A rope in tension between Earth and Moon

    I attatch a rope of a constant density to the Moon and fasten it down to the surface. I set the other end in space right above Earth's atmosphere. The angular speed of the entire rope is brought up to the same angular speed as the Moon at time=0. http://i.imgur.com/kHlVvnM.png What would...
  16. F

    Gravitational potential energy between Earth and Moon

    Homework Statement Consider the Earth's radius to be 6.40x103km, its mass to be 6.00x1024kg, the Moon's mass to be 7.36x1022kg, and the Moon's radius to be 1.74x103km. The average value for the Earth-Moon distance is 3.84x105kg. Neglect friction and rotation. a. Sketch the potential...
  17. L

    Earth and moon where does gravity cancel out

    Homework Statement where does the gravity cancel out between the Earth and moon?Homework Equations s=3.84405x10^8m earth m = 5.98x10^24kg moon m =7.35x10^22kg G = 6.67x10^-11N m^2/kg^2 mass of object between = 1kg for simplicity F = G x m / r^2 r = ? F Earth = F moon G x Earth / r^2 = G x moon...
  18. A

    Gravitational pull with the earth and moon

    Homework Statement The mass of the moon is 7.35x10^22 kg. At some point between Earth and the Moon, the force of Earth's gravitational attraction on an object is canceled by the Moon's force of gravitational attraction. If the distance between the Earth and the moon (center to center) is...
  19. R

    Gravitation Field between the Earth and Moon

    Homework Statement There is a point on the line between the centres of the Earth and the moon where their gravitational fields have equal magnitude but are in opposite directions, effectively creating a point of zero gravity. Calculate the distance of this point from the centre of the earth...
  20. J

    Central Magnetic Force between Earth and Moon

    Hey guys I have a question about central magnetic forces between the Earth-Moon system and how they would work at a very large scale similar to that of the central gravitational force. I don't know about electromagnetism as well as I do basic celestial mechanics, so I'm at a loss as to how I...
  21. D

    Earth and Moon Orbits Aligned: Consequences?

    what would happen if moon orbits around Earth were to be on the same plane as the earthe Earth's orbit around the sun?
  22. A

    Why doesn't tidal force pull earth and moon together?

    Why does tidal force strectechs the Earth and creates two tidal bulges, like pulling on a rubber band, instead of pulling Earth and moon together?
  23. T

    Point between earth and moon where net gravitational force is zero

    A) If the moon of mass mM has radius RM and the distance between the centers of the Earth and the moon is REM, find the total gravitational potential energy of the particle-earth and particle-moon systems when a particle with mass m is between the Earth and the moon, and a distance r from the...
  24. J

    Lunar orbit question (calculating the mass ratio of earth and moon)

    The problem I am struggling with is this . . The centre of the Earth-Moon system is 4.7x10^3 km from the centre of the earth. Calculate; i.the ratio of the mass of the Earth with the mass of the moon. ii.The acceleration of free fall on the Moon's surface. Constants Distance between...
  25. nukeman

    Is it possible that (re: earth and moon)

    Is it possible that...(re: Earth and moon) (This is regarding how the moon became apart of our orbit) Is it not possible that insted of the moon simply crashing into the earth, giving us some of its mass, and the rest just drifts off, gathers and gets caught in our orbit...could it not of...
  26. C

    Where is the point where the Earth's gravity is cancelled by the moon?

    Homework Statement Somewhere between the Earth and the moon is a point where the gravitational attraction of the Earth is canceled by the gravitational pull of the moon. The mass of the moon is 1/81 that of the earth. How far away from the center of the Earth is this point? a) 8/9 the way...
  27. R

    Astroid Toutatis year 2012 has effects on Earth and moon

    What are the physical possiblities if the ,astroid Toutatis , crosses directly between the moon and Earth on December 12th 2012. I understand that this is a fairly large astroid and is projected to zoom near Earth somewhere in the range of the distance between Earth and the moon. What are the...
  28. O

    De Broglie wavelenght of Earth and Moon

    Hi, Could someone please crunch for me the de Broglie wavelenght (\lambda), frequency (f) and energy (E) of Earth at perihelion (30300m/s) and at aphelion (29300m/s) and mean (29800m/s) Here are the numbers and formulas: \lambda=h/p , f=E/h , p=m*v (momentum=mass*velocity) h - Planck's...
  29. M

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    Homework Statement A spaceship is launched and starts moving directly towards the Moon. At what distance from the Earth will the pull of the Moon on the spaceship exceed the pull of the Earth? Ignore the effect of the Sun in this calculation. Homework Equations F = Gm1m2/r2 F = ma...
  30. Z

    What distance is the magnitude of gravity equal between earth and moon?

    Homework Statement At a point between the Earth and moon, the magnitude of the Earth's gravitational acceleration equals the magnitude of the moons gravitational acceleration. What is the distance of that point from the center of the earth? The distance from the center of the Earth to the...
  31. T

    Gravatational Force between earth and moon

    I was wondering, if the moon losses its mass at a constant rate and the Earth gains mass at this constant rate (so the sum of there masses is equal), the force between them would stay the same would it not? F = GMm/d² What happens to the moon? Does the moon move away, stay the same or come...
  32. Z

    Calculate Where Earth & Moon's Gravitational Attraction Is Canceled

    Homework Statement The mass of the Moon is 7.36 x 10 ^ 22 kg. At some point between Earth and the Moon, the force of Earth's gravitational attraction on an object is canceled by the Moon's force of gravitational attraction. If the distance between Earth and the Moon (center to center) is 3.84...
  33. P

    Earth and Moon (Acceleration of Gravity)

    Homework Statement The moon has a mass M = 7.36e+022 kg and an average radius R = 1740 km. for part a)I solved for the gravitational acceleration on the surface of the moon= 1.62 m/s^2 An object on Earth weighs 64 N. b) What is the weight of this same object on the moon? Answer...
  34. M

    Distance between earth and moon increasing

    I learned that the distance betwee the Moon and the Earth is increasing but I couldn't find the reason for it, Is it because of the Earth's orbit? I mean that when the distance is minimum , causes the moon to move towards the sun ( Newtonian laws ) and even when the distance becomes maximum the...
  35. E

    Gravity between earth and moon

    If an astronaut is located close to the positional median between the Earth and its moon, will the astronaut float around as if it was not being effected by gravity for the same reason that a person in an elevator in free fall would float around being unable to use a measuring device to...
  36. H

    N-body simulation test with sun, earth and moon

    Hi ! first, excuse my english, I'm just a poor french student... and we are so bad in languages here... anyway.. I'm trying to make a little program which could calculate the motion (and some other little things) of n bodies linked with gravitationnal interaction. (my final aim will be to...