suppose the moon is a black hole

[suntrack2]

what would be the operations on moon, in such case moon too could be able to swallow the other nearby material into it? or moon will not be visible? or moon can disturb the electronic system of earth, what exact impact may fall accordingly. ? will moon sparkle at night on a full moon day ?

ofcourse moon is a real moon, but just I am giving a tilt here "suppose".

I am trying this question with a status "not a childish question".

[antoniseb]

If the Moon were a black hole with the same mass as the Moon, it would be tiny, and we wouldn't have discovered it until recently, and would be at a loss to explain tides. It is possible that it could have been noticed during times that with our current Moon we call Total or Annular Solar Eclipses, because there would be a small amount of gravitational lensing disturbing the face of the Sun.

[suntrack2]

Antoniseb, thank you very much for the answer, your last line is quite important, that it may disturb sun by a small amount of gravitational lensing, amazing. In such case do you think that the loss of tides over sea may be advantagious in respect of tsunami like big tides, or such tides may be later become slower! planetory effect will be larger?

[Neverfly]

Apollo would have been a disaster.

[Neverfly]

"We put a man on the moon!"











"He didn't come back... But, by golly, we put him there!"

[antoniseb]

In such case do you think that the loss of tides over sea may be advantagious in respect of tsunami like big tides, or such tides may be later become slower! planetory effect will be larger?

No, the tides would be the same as we see today. Same frequency, same intensity. The gravity from the object is the practically identical at our distance.

[suntrack2]

there will not be a major gravitational pool between such type of moon and earth! what disturbance the eclipse period will get?

[phaishazamkhan]

If the Moon were a black hole with the same mass as the Moon, it would be tiny, and we wouldn't have discovered it until recently, and would be at a loss to explain tides. It is possible that it could have been noticed during times that with our current Moon we call Total or Annular Solar Eclipses, because there would be a small amount of gravitational lensing disturbing the face of the Sun.

I thought that the sun had a greater effect on Earthly tides than the moon?

[Michael Noonan]

I thought that the sun had a greater effect on Earthly tides than the moon?

It is significant but according to Wiki here

Down the page a bit under Tidal forces

A schematic of the Earth-Moon system, showing the entire Earth following the motion of its center of gravity. The tidal force produced by a massive object (Moon, hereafter) on a small particle located on or in an extensive body (Earth, hereafter) is the vector difference between the gravitational force exerted by the Moon on the particle, and the gravitational force that would be exerted on the particle if it were located at the center of mass of the Earth. Thus, the tidal force depends not on the strength of the gravitational field of the Moon, but on its gradient. The gravitational force exerted on the Earth by the Sun is on average 179 times stronger than that exerted on the Earth by the Moon, but because the Sun is on average 389 times farther from the Earth, the gradient of its field is weaker. The tidal force produced by the Sun is therefore only 46% as large as that produced by the Moon.

The full article in Wiki also has a neat animation next to this text.

[Van Rijn]

I thought that the sun had a greater effect on Earthly tides than the moon?

No, it's more massive, but much further away. From here:

The moon, which is approximately 240,000 miles (386,240 km) from the earth, exerts a greater influence on the tides then does the sun, which sits 93 million miles (150 million km) from the earth. The strength of the sun's gravity is 179 times that of the moon's but the moon is responsible for 56% of the earth's tidal energy while the sun claims responsibility for a mere 44% (due to the moon's proximity but the sun's much larger size).

[Van Rijn]

Heh. Another example of parallel posts, with the same time stamp.

[tony873004]

This is an interesting question. The event horizon would be less than 2 centimeters. Aside from the inexplicable tides, by now, we would have noticed an unexplained wobble in the Earth's position. Also, asteroids passing less than 1 lunar distance would be perturbed in a noticable way. Manmade satellites would probably have their orbits drift in a noticable way, escecially the geosynchronous satellites.

Gravitational lensing and eclipses have already been mentioned. I would guess that a light source directly behind the black hole moon would have its light bent by about 1 degree. The Sun would take on a highly distorted shape during solar eclipses, as would planetary and stellar occultations, although these would be extremely rare.

[Michael Noonan]

This is an interesting question. The event horizon would be less than 2 centimeters. Aside from the inexplicable tides, by now, we would have noticed an unexplained wobble in the Earth's position. Also, asteroids passing less than 1 lunar distance would be perturbed in a noticable way. Manmade satellites would probably have their orbits drift in a noticable way, especially the geosynchronous satellites.

Gravitational lensing and eclipses have already been mentioned. I would guess that a light source directly behind the black hole moon would have its light bent by about 1 degree. The Sun would take on a highly distorted shape during solar eclipses, as would planetary and stellar occultations, although these would be extremely rare.

Right so we would definitely noticed by now, good. I guess that pretty much takes care of any significant black holes in near earth orbit.

I am still puzzled though because if a primordial black hole took up residence in the moon and needed say a million years to get big enough to swallow it, what then? Would it stay around long enough to do it?

[phaishazamkhan]

Heh. Another example of parallel posts, with the same time stamp.

I call it hivemind.

Also amused that one says 44% and another says 46%

[hhEb09'1]

Also amused that one says 44% and another says 46%

One says 44% tidal energy, the other 46% tidal force. The 46% is computed just by dividing 179 by 389, not sure what the website used to compute the 44% figure, it's just presented without other figures.

[Argos]

there will not be a major gravitational pool between such type of moon and earth! what disturbance the eclipse period will get?

Everything would be the same, suntrack, as Antoniseb points out. The mass of the Moon would be unchanged, so would be its orbital period and gravitational influence. Such a strong g field transiting across the suns disc would cause noticeable lensing disturbances.