# Tag Info

4

There are a couple of atmospheric phenomena that can create rings around the moon. Corona are caused by water droplets diffracting the moon's light, they are fairly small, and close to the moon. They are coloured but not as brightly as a rainbow. Our eyes are also not so good at seeing colours in dim light. The 22-degree halo is a larger ring, as big as ...

-3

I think you very nearly answered your own question. The rainbows are indeed due to light diffracting off high altitude ice crystals, but more in a kind of haze than in the form of clouds. I have seen something similar in Hereford UK, but only on very rare occasions. There must be something unusual about the climate where you live for you to see them so often....

19

The following diagram from the wikipedia article on the tidal force shows the tidal force that results from a moon. Note that the tidal force is directed away from the center of the planet when the moon (satellite) is directly overhead or underfoot but is directed toward the center of the planet when the moon is on the horizon. You are right that these very ...

19

Everything in the universe has a gravitational influence on everything else in the universe. It isn't a question of the strongest gravitational pull winning out and all the others doing nothing. The Earth is the strongest pull on the oceans, but the Moon and the Sun both have easily measurable effect in addition to the Earth's. Other bodies (Venus, Jupiter, ...

3

Astropy is one option: from astropy.time import Time from astropy.coordinates import solar_system_ephemeris, EarthLocation from astropy.coordinates import get_body, get_moon from astropy.coordinates import SkyCoord, EarthLocation, AltAz from astropy import units as u import time; t = Time("2019-08-11 11:00", scale="utc") loc = EarthLocation(lat=38.2464000*...

4

Earth's current rotation is faster (~1 day) than the Moon's orbital period around Earth (~28 days). This leads to tidal acceleration -- the tidal bulges raised by the Moon rotate ahead, pulling on (and being pulled by) the Moon. Over a long period, this converts Earth's rotational momentum into Lunar orbital momentum. The Earth's rotation slows, and the Moon'...

-1

There is not the slightest chance of the Earth stopping spinning, but if it did there would be hardly any effect on the moon. It would continue to orbit just as it has always done. You ask about a very gradual slowing ,and what the result of that would be. We are on very firm ground here, because there has already been a gradual slowing and we know exactly ...

-1

I would argue that the lower limit on impact delay is somewhere around 1.3 seconds. Any impact that would leave the Moon at rest relative to Earth (see previous answers) would also, ahem, structurally disrupt the Moon. As in, turn it into an expanding cloud of vapor and debris, some of which would strike Earth sooner, some of which would form a ring, some ...

3

Here is the math for the fastest scenario, in which the Moon would suddenly stop orbiting and fall straight to Earth: Moon's mass: $m_1 = 7.342 \times 10^{22} kg$ Earth's mass: $m_2 = 5.9723 \times 10^{24} kg$ Minimal distance between Moon and Earth: $r = 356400000 m$ Gravitational constant: $G = 6.6743 \times 10^{-11} m^3/(kg \times s^2)$ Force applied ...

0

TL;DR: Anything between 1,5 hours and infinity. Let's assume the moon would be hit in its perigee by an object of the same mass and speed but opposite direction of movement relative to Earth. Let's also assume a sizeable chunk of debris left by this colossal impact would remain at the last known position of the moon but with zero orbital velocity. (Maybe ...

9

There are two issues at play here, only one of which is real. It's possible to compute the energy and momentum that an asteroid impact would have to transfer to the Moon, assuming that two solid balls (classic Newtonian billiard balls) hit each other (either a direct impact or a glancing impact). There are certainly cases where the result would be the Moon ...

44

As several people have said, this is incredibly unlikely. Part of the reason why is that the "circling the drain" effect you describe doesn't really happen for solid objects much less dense than black holes. Orbits are not "precarious" in that way. So, suppose something large enough and fast enough to change its velocity noticeably, but not large enough or ...

14

There is no possibility whatsoever of the moon getting knocked out of its orbit by an asteroid impact. Compared to the moon, even a large Chicxulub-type asteroid has a very tiny mass, and the moon has already been struck by several of them, but as you can see, it wasn't knocked out of its orbit. The largest asteroid in the asteroid belt is Ceres, 500 miles ...

12

It would be much better for Earth if the impactor hit the moon... In this Worldbuilding answer, I used a paper on ejecta kinematics to do calculations for ejecta velocity upon impact. Without going into too much detail here, much of the ejecta from a large impactor would not exceed the moon's escape velocity of 2.38 km/s. You can examine Figure 7 from the ...

8

The Moon orbits the Earth from $\approx$ 380000 km, but its radius is only $\approx$ 3500 km. The sky has 41253 sq degrees, and the Moon covers only $\approx$ 0.25 sq degree from it. Thus, the probability that an incoming meteor is blocked by the Moon, is $\approx$ 1:160000. Thus, the Moon is totally unfeasible to protect us from anything. The debris would ...

-4

A meteor is a small, sand grain or pea-sized fragment which burns up in the atmosphere before hitting the ground. Those large enough to reach the ground ae called meteorites. It seems to me the ones you are talking about are large enough to be called asteroids. The moon affords hardly any protection against asteroids, and those that strike the moon do very ...

4

There's a principal in science that a strong hypothesis doesn't depend on numerous improbable factors. I read that somewhere, I think it was Phil Plait who created the bad astronomy website, but I can't find it right now. For Mercury to have done what you claim, a 2nd planet would have needed to form between Earth and Jupiter, OK, maybe that happened, in ...

1

It is highly improbable that the moon was created by a collision between Earth and Mercury, or that there has ever been such a collision. The idea that Mercury was formed in what sounds from your description like the asteroid belt and from there migrated to its present orbit, striking the Earth on the way, is pure speculation and there is no evidence for it. ...

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