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44

It'd suck in very little mass. One thing to understand about black holes is that they have super-strong gravity, but only when you are very close to their event horizon. Otherwise they're just normal objects. If the Moon became a black hole, it would have a radius of about 0.1 millimeters. You need to get pretty close to this distance before you notice ...


23

A lot of debris has probably fallen back to earth. To stay in orbit you need enough angular momentum to overcome attraction. But if the collision happened at an angle a portion of the debris could have enough angular momentum to sustain orbit. Here is a nice video of how the collision could have happened. Here are some snapshots from the video in case the ...


23

It would suck in basically nothing. If the mass of the moon were concentrated in a black hole, you could draw a sphere around that black hole the size of the moon, and for everything outside that sphere, nothing would have changed. The gravity field would be just the same as it is now. Now, black holes are tiny. At the mass of the moon, the radius is on the ...


18

There is no significance in the fact that the same face of the Moon is always oriented towards the Earth. It simply means that the rotation of the Moon around its own axis has the same period as the orbit of the Moon around the Earth. (This wasn't always so. It can be reconstructed that the Moon previously had a faster rotation rate than it has now. ...


15

Right now, it already eats a fair amount of mass, as tiny meteors (and occasional big ones) rain down on it every day. Once it became a black hole, it would eat far less. Gravitationally, meteors would behave exactly the same while they're outside the moon's former radius. This is because the gravitational field of a spherical shell is exactly the same as ...


14

Theories of the moon's formation are hypothetical and a subject of active research. While the impact theory is the most popular at the moment, it's not a done deal. So the true answer is that we don't know. But proposals for how it might have happened generally suggest a glancing collision, where the second body (Theia) ploughs through the mantle of the ...


12

I agree you raise a valid point. It is of course the case that material that is thrown up will not enter circular orbit automatically. Compare launching of satellites. The rocket sets its payload up such that the payload will reach an orbital apogee near the intended altitude, and then some more propulsion is needed to circularize the orbit. So the question ...


11

Foucault's pendulum would, indeed, work on the Moon - though because the rotation is much slower (a period of about 2360 ks versus about 86 ks), the pendulum will also precess that much slower. (It will also swing with a longer period, due to the reduced gravity, but that's a different matter.) Regarding your question about whether the rotation is "real&...


10

About 32 femtograms per day As others have explained, a black hole doesn't really suck in matter. It uses gravity to pull matter in, but that is not any different from how the moon acts now. Only matter that is on a direct collision course with the black hole will actually get eaten up, any other matter will just pass by and fly off into space again. A black ...


8

Hypersonic collisions of solid matter results in vapor. Much of the "debris" must have been in the gas state. Gas doesn't generally follow Keplerian orbits: instead it collapses into a disk. The subsequent evolution of the disk, condensation and accretion, formed the Moon in a process similar to the formation of planets. At least that's the current ...


4

The Roche limit is calculated on the assumption that the orbiting body is held together only by its gravitation i.e. there are no cohesive forces with the body that help hold it together. For large bodies this is a reasonable assumption, and indeed it is why large celestial bodies are approximately spherical. Their gravitation is so much stronger than any ...


4

Does the moon's elliptical orbit around Earth also affect Earth's spin? What effect does distance play? The moon's orbit affect's earth's spin. The eccentricity is not especially relevant, but the distance is. The closer the moon, the stronger the tidal forces, and (to a first-order), the greater the coupling between the two. That would suggest slowing ...


4

The answer to your question is already in the article you linked. The Earth would be 1.2 milli-degrees Fahrenheit cooler without thermal radiation from the moon.


4

they are different because the earth has a hot molten core which drives convection between the surface and the core. This convective movement breaks the crust up into slabs which crunch into one another in slow motion, driving the creation and continuous renewal of mountain ranges and valleys via a process called plate tectonics. No plate tectonic processes ...


4

Valid suggestion, but there is a problem. You would need a really tough custom-made balloon to not burst in vacuum. Regular balloons burst at about 0.1 atm pressure difference, which means you will need a 10 times thicker, and therefore heavier balloon. So, experiments that rely on balloon being light wont work. Such balloon would probably have to be custom ...


3

The Giant Impact might have liquified and even vaporized a large part of both the impactor and the Earth. If this was the case, gas expansion may have added velocity to ejecta post-ejection, to alter the orbits of the ejecta. Lock et. Al propose the possibility that the impact that created the Moon imparted so much energy that the resultant system exceeded ...


3

Yes, it would work. Of course, you should take into account that gravity at the Moon's surface is only 1/6 of the value on Earth and that a Moon (sidereal) day is 27 Earth days.


3

Probably much less than its present rate. Moon has a lot of surface to "catch" meteorites and convert their kinetic energy into heat (so they won't bounce back into space). If made a black hole, most of these will pass in a parabolic/hyperbolic orbit around the black hole and leave for good. In order to get something into the black hole (less than ...


3

The referenced link is not that good: The planet Mercury is tidally locked to the Sun so that the same scorchingly hot side always faces the Sun and the other side is perpetually cold. This was what was thought to be the case a century ago. That Mercury does not rotate at the same rate that it orbits the Sun was overturned over half of a century ago. ...


3

I believe this is due to Rayleigh scattering. The light from the moon passes through a thicker layer of atmosphere when the moon is low in the sky than when it is high. The light gets scattered along the way, with shorter wavelengths being scattered the most. That means bluish colors are scattered away more than red, so you see the moon as appearing reddish. ...


3

On the surface of the Moon, the main source of radiation is energetic solar particles (mostly protons and electrons) and galactic cosmic rays (GCR). (The GCRs come out of the Solar system.) The gamma radiation (as a primary particle) is negligible. (The gamma flux in the space is very low...) According to this article, most of the particle showers won't ...


3

I think I understand your question. It's not so much about Foucault's Pendulum as it is about frames of reference. I believe this is what you are thinking: If you ignore the rotation of the moon and just think of it as an orbiting point, then an obvious way to use it to generate a coordinate system that follows it is to have one axis tangent to the orbit, ...


3

A balloon in a vacuum would expand to more than its usual size as there is no counter-acting atmospheric pressure. I agree it would make for an interesting and fun experiment. There is a famous experiment illustrating Galileos observation that all objects fall at the same speed no matter what their mass. Here, an astronaut releases a feather and a hammer at ...


3

The Moon's escape velocity is about $2.38 km/s$. Nobody can throw anything at that speed. A suitable machine can, of course, do it - as evidenced by the fact that we've been to the Moon and back.


2

A projectile hitting a water surface under any angle causes a circular wave. The reason is that the surface is a uniform medium so the propagation speed does not depends on direction. The same is the case for a solid surface.


2

In the third century BCE Aristarchus of Samos estimated the ratio of the distance of the sun to the distance of the moon by observing the angle between the sun and the moon when the moon was exactly half full.


2

When you ask, "What causes tides?", you may hear, "Gravity". A follow up question is: "Which tide is stronger: the Sun or the Moon?",..., "The Moon". So: Then why does the Earth orbit the Sun and not the Moon?....clearly, the Sun's gravity is stronger (about 250x). The resolution to this tidal paradox is that tides are ...


2

If we ignore other bodies, the orbital plane will remain fixed. It will not turn along with the Moon as the Moon orbits. That would require a force acting on the satellite which is not in the orbital plane. Orbits do precess in real-world examples, but that is under the influence of other bodies (or of uneven features of the body orbited), and it is usually ...


2

I can see where you're getting this question from: If you fire a cannon from the surface of an airless planet with enough velocity to achieve some sort of orbit, then that cannonball will inevitably come back around and hit the cannon in the back. But the situation gets a lot more complicated when you have vast amounts of debris flying into space, because ...


2

Newton's cannonball seemingly applies here, which I suspect is the basis for your question. An unpowered orbiting body will revisit its position, so anything that got shot off from the surface of the Earth must revisit the Earth. That is correct. However, unpowered is the issue here. If something interferes with this object mid-orbit, it can alter its ...


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