| Author |
Message
|
| siddhant |
 Posted: Tue May 06, 2008 2:41 am Post subject: WHAT IS THE CAUSE OF EARTH'S ROTATION ABOUT IT'S OWN AXIS? |
 |
|
Forum Freshman
Joined: 05 May 2008
Posts: 6
Location: india
|
I KEEP ON THINKING OF PHENOMENONS I CAN'T EXPLAIN.. CAN ANYONE EXPLAIN THIS ONE.. PLEASE...
HELP ME.... PLEASE.................................
_________________
I won't die until i find out where i m gonna go after dying..... and I KNOW PHYSICS IS GONNA HELP ME FIND IT OUT. |
|
| Back to top |
|
 |
| Dishmaster |
| Posted: Tue May 06, 2008 5:55 am Post subject: |
|
|
Forum Bachelors Degree
Joined: 30 Apr 2008
Posts: 459
Location: Heidelberg, Germany
|
It is a relic from the formation of our solar system. As I already explained in a different thread, in the beginning everything in the universe has a slight rotation, how small it may be. This often a result of encounters of - let's say - gas clouds that attract each other by gravity.
From such gas clouds that always also contain about 1% of dust, the stars form by gravitational collapse. Certain density and temperature conditions must be fulfilled so that a cloud can collapse by self gravity, i.e. the inner denser parts pull at the outer parts. Like an ice skater who pulls in his arms in order to increase his rotation, such clouds spin faster and faster during the collapse. The resulting centrifugal force in part compensates the gravity leading to the formation of a disc in the plane of the equator of the rotation. The centre forms the star, the disc is the material that forms planets.
The disc material is viscous, i.e. there is friction leading to local eddies that rotate inside the disc that itself rotates around the future star (called protostar). Through a process that is not yet well understood, these rotating eddies collapse themselves under self-gravity forming planets. The rotation that these proto-planets have survive the planet formation phase. As a result the planet rotates, because the local densification from which it ermerged inside the early viscous disc rotated. I hope, I was able to explain it. |
|
| Back to top |
|
|
| dejawolf |
| Posted: Tue May 06, 2008 1:11 pm Post subject: |
|
|
Forum Ph.D.
Joined: 31 Dec 2006
Posts: 716
Location: Norway
|
earth probably started rotating from all the asteroids colliding with it.
_________________
only a fool puts art above science. |
|
| Back to top |
|
|
| Ophiolite |
| Posted: Tue May 06, 2008 1:42 pm Post subject: |
|
|
Forum Radioactive Isotope
Joined: 25 Jul 2005
Posts: 4858
Location: Scotland
|
dejawolf,
read Dishmasters explanation. It is the correct one. Doubtless the impacts of comets and asteroids effected the rotation, but they did not cause it. The impact of a Mars sized planetesimal that is believed to have created the moon, probably also led to the high initial rotation rate - six hours or less.
_________________
The Universe is not only weirder than we imagine it is weirder than we can imagine. J.B.S.Haldane. |
|
| Back to top |
|
|
| sak |
| Posted: Tue May 06, 2008 2:02 pm Post subject: |
|
|
Forum Sophomore
Joined: 21 Sep 2007
Posts: 149
|
| I think the entire bodies in universe rotate. Where does the energy come from? When will they exhaust? The Sun & Moon put lot of tidal force on earth. Even then the rotation survived for such a long period? |
|
| Back to top |
|
|
| Ophiolite |
| Posted: Tue May 06, 2008 2:49 pm Post subject: |
|
|
Forum Radioactive Isotope
Joined: 25 Jul 2005
Posts: 4858
Location: Scotland
|
Energy can neither be created or destroyed. (We shall ignore transformation to matter and vice versa.) The energy of rotation, expressed as angular momentum, in any system must remain the same. All that happens with the tidal interaction of the Earth and the moon is that the Earth slows down (losing angular momentum) and the moon moves further away (gaining angular momentum).
_________________
The Universe is not only weirder than we imagine it is weirder than we can imagine. J.B.S.Haldane. |
|
| Back to top |
|
|
| Cold Fusion |
| Posted: Tue May 06, 2008 4:20 pm Post subject: |
|
|
Forum Ph.D.
Joined: 10 Apr 2007
Posts: 814
Location: In the circuitous haze of my mind
|
How noticeable is that effect? How many meters per year (if not Km) does the moon move away, and how much velocity does the earth lose per year?
_________________
Forget all that you know, achievements can only be accomplished by starting from nothing and selectively applying facts that are purely objective and absolutely necessary.
"Two things are infinite: the universe and human stupidity; and I'm not sure about the universe."
"Great spirits have always found violent opposition from mediocrities. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence"
-Einstein
http://boinc.berkeley.edu/download.php
Use your computing strength for science! |
|
| Back to top |
|
|
| Dishmaster |
| Posted: Wed May 07, 2008 3:09 am Post subject: |
|
|
Forum Bachelors Degree
Joined: 30 Apr 2008
Posts: 459
Location: Heidelberg, Germany
|
| Cold Fusion wrote: |
| How noticeable is that effect? How many meters per year (if not Km) does the moon move away, and how much velocity does the earth lose per year? |
The moon distance increases by 3.8 cm every year. This has an effect on the Earth's rotation that the day is prolonged by 23 microseconds per year. Another counter effect reduces this to a net value of 17 microseconds per year. This does not seem much, but it sums up to quite a number if calculated back to millions of years in the past. Remember: 86400 seconds roughly make a day. |
|
| Back to top |
|
|
| dejawolf |
| Posted: Wed May 07, 2008 10:24 am Post subject: |
|
|
Forum Ph.D.
Joined: 31 Dec 2006
Posts: 716
Location: Norway
|
thats not much at all. it basically means when the dinosaurs died out, earth spun about 18 minutes slower.
_________________
only a fool puts art above science. |
|
| Back to top |
|
|
| Dishmaster |
| Posted: Wed May 07, 2008 11:14 am Post subject: |
|
|
Forum Bachelors Degree
Joined: 30 Apr 2008
Posts: 459
Location: Heidelberg, Germany
|
| dejawolf wrote: |
| thats not much at all. it basically means when the dinosaurs died out, earth spun about 18 minutes slower. |
Faster. It slows down. The days were shorter then. |
|
| Back to top |
|
|
| sak |
| Posted: Wed May 07, 2008 12:17 pm Post subject: |
|
|
Forum Sophomore
Joined: 21 Sep 2007
Posts: 149
|
| Dishmaster wrote: |
| Another counter effect reduces this to a net value of 17 microseconds per year. This does not seem much, but it sums up to quite a number if calculated back to millions of years in the past. Remember: 86400 seconds roughly make a day. |
14b * 17 X 10**-6 = 2.75 Days. Is it that pretty small? Our tidal height is over 1M! |
|
| Back to top |
|
|
| Dishmaster |
| Posted: Wed May 07, 2008 12:40 pm Post subject: |
|
|
Forum Bachelors Degree
Joined: 30 Apr 2008
Posts: 459
Location: Heidelberg, Germany
|
| sak wrote: |
| 14b * 17 X 10**-6 = 2.75 Days. Is it that pretty small? Our tidal height is over 1M! |
What are you calculating here? Is it the time shift within 14 billion years? The earth only exists for about 4.5 billion (10^9) years. I doubt that this rate can be extrapolated that far. It is probably only valid for a much shorter time.
Anyway, what is that reference to the tidal height? Are you suggesting that the tides are created by the rotation of the Earth? I think, in that case you should better look it up somewhere, because they aren't. At least not that simple, depending on the point of view how to explain them. |
|
| Back to top |
|
|
| William McCormick |
| Posted: Wed May 07, 2008 8:11 pm Post subject: |
|
|
Forum Professor
Joined: 03 Apr 2008
Posts: 1656
|
The liquid core of earth is what keeps it at the speed it is going at, pretty much. It would go much faster if the core cooled off.
My aunt Carole showed me the uncooked and the hardboiled egg spin test. Pretty cool.
MY guess is that if there was not some liquid in the core they could probably go faster.
Sincerely,
William McCormick
_________________
Warning: Any information contained in this post could be part of a conspiracy to make you stupid. So only use it if you understand it. Use at your own risk.
http://www.Rockwelder.com |
|
| Back to top |
|
|
| Dishmaster |
| Posted: Wed May 07, 2008 11:58 pm Post subject: |
|
|
Forum Bachelors Degree
Joined: 30 Apr 2008
Posts: 459
Location: Heidelberg, Germany
|
| William McCormick wrote: |
The liquid core of earth is what keeps it at the speed it is going at, pretty much. It would go much faster if the core cooled off.
My aunt Carole showed me the uncooked and the hardboiled egg spin test. Pretty cool.
MY guess is that if there was not some liquid in the core they could probably go faster. |
Oh please. How would that be possible? It is just its inertia of rotation. The breaking is done by tidal breaking by the sun and the moon. Did you know that the core of the earth is made of an outer shell of liquid iron (mostly) and an inner solid core? This is the thought to be the earth's dynamo producing the terrestrial magnetic field.
I suppose your aunt stirred the egg in water. This causes breaking due to friction. The test works, because the raw egg has a tendency to keep upright which is done by the chalaza (just looked the name up). You might remember the discussion about the main axes of inertia. The initially induced rotation is not done along one of the main axes. This hinders the rotation to continue.
http://en.wikipedia.org/wiki/Egg_(food) |
|
| Back to top |
|
|
| SuperNatendo |
| Posted: Thu May 08, 2008 2:36 pm Post subject: |
|
|
Forum Masters Degree
Joined: 10 Dec 2007
Posts: 518
Location: Nashville, TN USA
|
I think he (william) was talking about the test where you spin an egg and stop it with a finger and let go before the liquid yoke inside stops rotating, thus allowing the egg to resume spinning.
Hard boiled eggs don't do this, it all has to do with inertia.
But the thing that started the core spinning is as Dishmaster said:
"It is a relic from the formation of our solar system....in the beginning everything in the universe has a slight rotation, how small it may be. This often a result of encounters of - let's say - gas clouds that attract each other by gravity."
_________________
“It’s no wonder that truth is stranger than fiction. Fiction has to make sense.” - Mark Twain |
|
| Back to top |
|
|
|
|
