Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Dharmansh on 07/11/2011 17:57:37
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How do we get Night And day.It's obviously when sun comes it's day and moon comes it's night but how does earth rotate itself and makes moon revolve around her?Please help me m confused [???] [???] [???]
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It is a bit difficult knowing where to start with this one
Firstly the moon is in theory above the horizon just as much during the day as during the night its just that you tend not to see it.
Next the earth does not have to rotate itself because the rotation came as a result of the conservation of momentum and collision processes that formed the earth and there is so little friction associated with space and the distortions of the earth due to the gravity of the sun and the moon that the earth has not yet stopped rotating with respect to either of them.
This friction will eventually slow the rotation of the earth down and accurate time measurements do allow it to be measured at about 5 milliseconds per year and this is in good alignments with the ratio of day length to year length through the full four billion years or so of the earth's existence in the fossil record of days months and years in certain rock and shell formations.
The orbit of the moon came about as its formation in the debris of a collision early in the life of the earth but it has got considerably larger and slower over the billions of years due to this energy extracted from the rotation of the earth.
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Gravity holds the moon near the earth like a tether ball tied to a post. And with little friction, it keeps spinning around the earth essentially forever. However, paradoxically, since the earth spins faster than the moon orbits, the friction in the tides impart more energy to the moon, which in turn very slowly pushes it away from Earth, rather than pulling it closer.
The moon orbits the earth in just less than one month. When it is behind the Earth, furthest from the sun, we see a full moon. When it is to the side, we see a fraction of the moon. When it is between the earth and the sun, it can be hard to see, often called "no moon" or "new moon". Sometimes an eclipse will occur when the moon is between the earth and the sun.
The earth is spinning at a rate of one revolution per day. The sun illuminates one side (day), while the other side is dark (night). You can think about it as being like shining a flashlight at a softball in the dark. One side is bright. One side is dark. Now, if you slowly turn the softball, so it turns once a day, you can see the slow progression from night to dawn to day to dusk to night on the different parts of the softball.
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you are right CliffordK gravity holds moon near the earth so what about 2005 YU55 i have heard that it has came between moon and earth so will 2005 YU55 will revolve around the earth like moon or it will crash with earth and it's an giant asteroid, distance from earth is 240000 miles and distance from moon is 150000 miles??? [???] [???] [???]
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2005 YU55 is moving very fast with respect to the earth and the moon so although it will be slightly deflected by the gravity of the earth it could never enter orbit and will continue on a slightly changed orbit around the sun. Getting an object into a gravitational orbit around anything requires very precise adjustments of speed too slow and it will crash and too fast and it will just go away slightly deflected the difference in speed between these two is about 50%