|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
The speed of earth's rotation around itself and the sun
I was talking to a friend of mine and this subject came up: What happened to the speed of earth? Is it a few milliseconds slower than, say, it had been a few thousand years ago? We faintly remembered sci. & tech news we read so I decided to ask: How does speed of the earth's rotation around itself change around itself during time? Are we having longer or shorter days? How is this related to the speed of earth's rotation around the sun? Are our years getting longer or shorter? What is the relationship between a body's rotation around its axis and the rotation around some other body such as sun? I hope some of the physicists here can provide some URLs or pointers. Thanks in advance. -- Emre Sevinc eMBA Software Developer Actively engaged in: http:www.bilgi.edu.tr http://ileriseviye.org http://www.bilgi.edu.tr http://fazlamesai.net Cognitive Science Student http://cazci.com http://www.cogsci.boun.edu.tr |
#2
|
|||
|
|||
Dear Emre Sevinc:
"Emre Sevinc" wrote in message ... I was talking to a friend of mine and this subject came up: What happened to the speed of earth? Is it a few milliseconds slower than, say, it had been a few thousand years ago? We faintly remembered sci. & tech news we read so I decided to ask: How does speed of the earth's rotation around itself change around itself during time? The Earth is slowing, as angular momentum is transferred from Earth (spin) to the Earth-Moon system (increase in the orbital radius of the Moon) via tides. Are we having longer or shorter days? Longer. How is this related to the speed of earth's rotation around the sun? It isn't related, although it may affect how much energy the Sun can transfer to/from the Earth-Moon system. Are our years getting longer or shorter? You might look at the "tidal rhythmite" data. I think the length of year is pretty stable... look for references to "recession". What is the relationship between a body's rotation around its axis and the rotation around some other body such as sun? It really depends. All sorts of non-correlations right here in our solar system. David A. Smith |
#3
|
|||
|
|||
In message ze%Ue.228507$E95.159553@fed1read01, "N:dlzc D:aol T:com
(dlzc)" writes Dear Emre Sevinc: Are our years getting longer or shorter? You might look at the "tidal rhythmite" data. I think the length of year is pretty stable... look for references to "recession". I've raised this before, but can't remember the answer! Is there any way to tell? Rhythmites tell us there were more days in the year than there are now, but AFAIK that assumes the year is the same length. -- Remove spam and invalid from address to reply. |
#4
|
|||
|
|||
"N:dlzc D:aol T:com \(dlzc\)" N: dlzc1 D:cox writes:
Dear Emre Sevinc: "Emre Sevinc" wrote in message ... I was talking to a friend of mine and this subject came up: What happened to the speed of earth? Is it a few milliseconds slower than, say, it had been a few thousand years ago? We faintly remembered sci. & tech news we read so I decided to ask: How does speed of the earth's rotation around itself change around itself during time? The Earth is slowing, as angular momentum is transferred from Earth (spin) to the Earth-Moon system (increase in the orbital radius of the Moon) via tides. Are we having longer or shorter days? Longer. How is this related to the speed of earth's rotation around the sun? It isn't related, although it may affect how much energy the Sun can transfer to/from the Earth-Moon system. Are our years getting longer or shorter? You might look at the "tidal rhythmite" data. I think the length of year is pretty stable... look for references to "recession". Thanks a lot for the explanation. I'll use the keywords you have provided for further research. -- Emre Sevinc eMBA Software Developer Actively engaged in: http:www.bilgi.edu.tr http://ileriseviye.org http://www.bilgi.edu.tr http://fazlamesai.net Cognitive Science Student http://cazci.com http://www.cogsci.boun.edu.tr |
#5
|
|||
|
|||
Emre Sevinc wrote in
: "N:dlzc D:aol T:com \(dlzc\)" N: dlzc1 D:cox writes: Dear Emre Sevinc: "Emre Sevinc" wrote in message ... I was talking to a friend of mine and this subject came up: What happened to the speed of earth? Is it a few milliseconds slower than, say, it had been a few thousand years ago? We faintly remembered sci. & tech news we read so I decided to ask: How does speed of the earth's rotation around itself change around itself during time? The Earth is slowing, as angular momentum is transferred from Earth (spin) to the Earth-Moon system (increase in the orbital radius of the Moon) via tides. Are we having longer or shorter days? Longer. How is this related to the speed of earth's rotation around the sun? It isn't related, although it may affect how much energy the Sun can transfer to/from the Earth-Moon system. Are our years getting longer or shorter? You might look at the "tidal rhythmite" data. I think the length of year is pretty stable... look for references to "recession". Thanks a lot for the explanation. I'll use the keywords you have provided for further research. Just a curiosity to add to your quest. The Earth's rotation rate measurably sped up with the recent Indian Ocean earhquake. The rupture of the fault caused a large enough change in the Earth's moment of inertia to result in a detectable shortening of the day. In general though, the trend is for the days to slowly length as angular momemtum gets transferred to the moon's orbit. As far as changes to the period of the Earth's orbit around the Sun, well I don't know how we could tell that prior to the invention of sufficiently accurate clocks. I would say that if what we know of gravity is correct then there are no significant purturbing factors to the length of the Earth's orbit around the Sun although it is known that the eccentricity of the orbit does slowly change with time as does the apsidal line. Klazmon. |
#6
|
|||
|
|||
Dear Johnathan Silverlight:
"Jonathan Silverlight" wrote in message ... In message ze%Ue.228507$E95.159553@fed1read01, "N:dlzc D:aol T:com (dlzc)" writes Dear Emre Sevinc: Are our years getting longer or shorter? You might look at the "tidal rhythmite" data. I think the length of year is pretty stable... look for references to "recession". I've raised this before, but can't remember the answer! Is there any way to tell? Rhythmites tell us there were more days in the year than there are now, but AFAIK that assumes the year is the same length. Rhythmites assume a constant infall of matter to produce the layers? So much accumulated debris = so much time. The distribution/nature of the debris describes the day, month, and annual cycles. I can't say I remember either. David A. Smith |
#7
|
|||
|
|||
Dear Llanzlan Klazmon:
"Llanzlan Klazmon" wrote in message .6... .... Just a curiosity to add to your quest. The Earth's rotation rate measurably sped up with the recent Indian Ocean earhquake. The rupture of the fault caused a large enough change in the Earth's moment of inertia to result in a detectable shortening of the day. Do you have a citation for this? The only references I have seen is that this purported decrease in length of day was a *prediction*. A prediction which apparently ignored the fact that amorphous rock is *less* dense than the magma it floats on, which subduction displaces more dense stuff to higher "altitude", increasing the moment of inertia, which should *slow* the Earth's rotation. David A. Smith |
#8
|
|||
|
|||
[Change in length of year.]
In article , Jonathan Silverlight writes: Is there any way to tell? I don't think there are any direct measurements. It's possible to _calculate_ the Earth's and other planets' orbits. I think I recall seeing calculations for 10^9 years or so, but a quick check finds only 10^8. Touma and Wisdom (1994 AJ 108, 1943) calculated the Earth-Moon orbit characteristics for 10^9 years. I don't see how they could do that without knowing what all the other planets were doing over that time, but I haven't read their paper in detail. Maybe someone else will track this down. You could start with an ADS abstract search on J. Wisdom. -- Steve Willner Phone 617-495-7123 Cambridge, MA 02138 USA (Please email your reply if you want to be sure I see it; include a valid Reply-To address to receive an acknowledgement. Commercial email may be sent to your ISP.) |
#9
|
|||
|
|||
According to this page at the U.S. Naval Observatory, the Earth's
rotation is about 1.4 milliseconds slower per day per century. http://tycho.usno.navy.mil/leapsec.html -- Paul Hirose To reply by email remove INVALID |
Thread Tools | |
Display Modes | |
|
|