Why doesn't the earth have a ring?
If solid material such as dust and moonlets, and common components of satellite systems are brought nearer to the Earth, then what will happen? Will it take the form of a ring or fall down on the Earth?
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$\begingroup$ I don't understand your question. Can you please rephrase the second long sentence into at least two and check grammar? $\endgroup$– AtmosphericPrisonEscapeJan 13, 2017 at 16:57
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$\begingroup$ Related question here: astronomy.stackexchange.com/questions/8112/… $\endgroup$– userLTKJan 13, 2017 at 18:13
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$\begingroup$ Earth has got a ring of geostationary satellites today. It's just not very dense. $\endgroup$– Wayfaring StrangerJan 15, 2017 at 16:19
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$\begingroup$ @WayfaringStranger. Do you think that ring is circular. $\endgroup$– Harsh KumarJan 15, 2017 at 16:21
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$\begingroup$ It's close to circular: en.wikipedia.org/wiki/Geostationary_orbit $\endgroup$– Wayfaring StrangerJan 15, 2017 at 16:22
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1 Answer
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Most planets don't have rings. The ring region is inside the Roche limit which is quite close to the planet. A ring system outside the Roche limit needs to be either very faint or, it would over time coalesce into a moon or possibly pair of moons at Trojan points to each other.
There's different Roche limits for rocky bodies vs icy, but an icy body couldn't exist in Earth's orbit for long, so it's not really relevant for the Earth. Saturn's rings are mostly ice, which extends about twice as far as the rocky body Roche limit.
How long a ring system lasts depends on a few factors. How big it is, whether it's given new material regularly or not, what it's made of and how vulnerable it is to the sun's rays. Saturn's rings, for example, are losing material, raining down on Saturn as well as slowly adding material from Enceladus, one of it's small and close moon's that gives up ring material by tidal-volcanic eruptions.
Earth's large moon could (not saying it would but it might) play a role in disrupting and Earth-Ring system more quickly than it would with no moon. A 2 body system with the 2nd body as large as the moon isn't gravitationally friendly to other orbiting objects.
Many man made satellites orbit well within the Roche limit but they are small enough to be held together and not be affected by tidal forces. Larger objects, just a few miles across, perhaps less, are more vulnerable to tidal forces and tend to break up inside the Roche Limit.
