eMTee Posted April 26, 2005 Report Posted April 26, 2005 I have a question about the spin of the Earth. I hear that the spin of the Earth is slowing down. how long has this been going on? and how fast is slowing down. like say compared with the speed today, how much faster would you say it went 100 years ago?
Buffy Posted April 26, 2005 Report Posted April 26, 2005 Well its an average, but something under 2 milliseconds every 100 years. The earthquake in Sumatra actually supposedly speeded up the rotation of the Earth, but this was postulated, not measured. Its been slowing down since it was created: its basically a gigantic flywheel that is acted upon by tidal forces induced principally by gravity from the Moon and the Sun... Cheers,Buffy
Queso Posted April 26, 2005 Report Posted April 26, 2005 AHH! that amazes me every time i think about it :rant:
C1ay Posted April 26, 2005 Report Posted April 26, 2005 I think I remember once that 1 second was added to the end of the year to make up for the accumulative loss thus far.
UncleAl Posted April 26, 2005 Report Posted April 26, 2005 The moon orbiting the Earth is tidally locked into its rotation and revolution rates being equal (give or take libration). The same part of the moon always faces the Earth. In a similar manner the Earth's rotational energy is being slowly bled away into the moon's orbit by tidal fricition until it too will be locked into a 28-day day. Angular momentum is conserved. Fresh water impoundments (dams) redistirubte mass. Like a spinning iceskater opening her arms, they slow down the Earth's rotation by takeing mass from sea level and moving it to higher altitudes. Wind electrical generators are working off the Earth's rotation in part - Coriolis acceleration of the wind. There ain't no such thing as a free lunch.
lindagarrette Posted April 26, 2005 Report Posted April 26, 2005 The moon orbiting the Earth is tidally locked into its rotation and revolution rates being equal (give or take libration). The same part of the moon always faces the Earth. In a similar manner the Earth's rotational energy is being slowly bled away into the moon's orbit by tidal fricition until it too will be locked into a 28-day day. Such a long day could cause major weather situations. I hope by then we have better methods of forecasting.
cnfsdnlostinside Posted May 19, 2005 Report Posted May 19, 2005 Its been slowing down since it was created: its basically a gigantic flywheel that is acted upon by tidal forces induced principally by gravity from the Moon and the Sun... Just as the Sun and moon have a gravitational pull on the Earth, the Earth has a gravitational pull on the sun and moon. I remember from some time ago that the moon moves maybe 2 or so inches away from the earth every so often (i don't remember if the time frame was a year, decade, century, or what ever) so eventually the moon will fall out of the earth's orbit. When this happens, how will the spin of Earth be effected? One radical thought that just jumped into my head is that if the lack of a moon causes a durastic change in earth's axial rotation, could the earth end up becoming similar to venus (obviously there are certain details that make this statement a very poor guess/stab in the dark, such as venus is closer to the sun and has an axial rotation about 8 times greater than ours; however, venus is only slightly smaller than earth, and it has no satellites)?
bumab Posted May 19, 2005 Report Posted May 19, 2005 It's about 1 1/2 inch per year. The moon will slowly leave orbit which will cause (among other things) a destabilizing of the earths tilt. Right now, the tidal lock that UA mentioned keeps us right around 23 1/2 degrees, but that will go all wacky when the moon gets far enough away. That's bad enough- imagine a 90 degree tilt... They measure that by bouncing a laser off the moons surface- a mirror was installed during the Apollo missions.
C1ay Posted May 19, 2005 Report Posted May 19, 2005 Such a long day could cause major weather situations. I hope by then we have better methods of forecasting.It has always been my position to predict that there is a 50% chance of rain everyday, either it will or it won't....
DigitaLMasteR_Alex Posted May 19, 2005 Report Posted May 19, 2005 I hear that the spin of the Earth is slowing down. how long has this been going on? and how fast is slowing down. like say compared with the speed today, how much faster would you say it went 100 years ago? I have always wondered about this case, I just can't get the answer for "will it stop? or will it settle in a specific rate of rotation " Though, I recommend you go see this site for accurate information on the subject The Slowing Spin of Earth
eMTee Posted May 20, 2005 Author Report Posted May 20, 2005 I remember from some time ago that the moon moves maybe 2 or so inches away from the earth every so often (i don't remember if the time frame was a year, decade, century, or what ever) so eventually the moon will fall out of the earth's orbit. It's about 1 1/2 inch per year. If the Moon was 2000 feet closer to the Earth than it is now...how would that effect the Earth's rotation and all?
bumab Posted May 23, 2005 Report Posted May 23, 2005 The earth would rotate a tad faster, and the pole progression would be a tad smaller. But really a negligable difference at only 2000 feet. REALLY negligable.
eMTee Posted May 23, 2005 Author Report Posted May 23, 2005 what would happen if it was 8,000 feet closer than it is now? or 8,000 feet furher than it is now?
C1ay Posted May 23, 2005 Report Posted May 23, 2005 what would happen if it was 8,000 feet closer than it is now? or 8,000 feet furher than it is now?Do the math.... G = 6.67 × 10^−11 N m^2 kg^-2m1 = 1 earth mass = 5.9742 × 10^24 kgm2 = 1 moon mass is 7.35 x 10^22 kgr = average Earth-Moon distance is about 385000 km
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