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Sunrise from west

by Faizan
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Faizan
#1
May21-04, 07:08 AM
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Hello friends,
i recently read somewhere that one day the sun would rise from the west and this year the sun would rise in the west in mars. Also i read that the direction of where our planet would change. Is this really true, if so then how and when canthis take place????
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mathman
#2
May21-04, 04:24 PM
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Barring a catastrophy (impact by a large asteroid?), the earth's rotation on its axis will not change direction, although it will gradually slow down over time. As for Mars, whatever it is will stay, unless hit by an extremely large object also.
Faizan
#3
May21-04, 11:15 PM
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Thanks mr.mathman, but i meant to ask whether the earth would change the direction of where it orbits around the sun or not and also can anyone tell me that which direction is earth revolving around now. And the other question is that what is "retrograde motion"?

enigma
#4
May22-04, 01:12 AM
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Sunrise from west

He answered your first question Faizan. The Earth will not change the direction it's rotating.

As for the direction, if you point your right thumb up, and imagine that is north, then your fingers curl in the direction of rotation and orbit. Retrograde motion is when an object orbits the other direction.
Faizan
#5
May22-04, 07:31 AM
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So Can Earth ever travel in retrograde motion, if so then when can this happen.
enigma
#6
May22-04, 02:23 PM
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Because of conservation of angular momentum, the Earth (and everything else) will continue to travel in the direction it is rotating unless acting on by an outside force.

Think about a spinning ice-skater. She will keep spinning in one direction, and keep spinning in that direction, and keep spinning in that direction. The only things which will slow her down are friction with the ice against her skates or when she opens her arms out and redirects herself.

The same thing is happening with the Earth except there is no ice, and there are no arms. There are a few things which are slowing down the rotation of the Earth. Gravitational interactions with the Moon and the Sun are slowing it down ever so slightly. The Sun will die out long before we slow down enough that we're not rotating relative to it (like the Moon is to us). That means that the only thing which could cause us to go retrograde (as mathman said) would be a huge (and I mean huge... as big as Mars at least) asteroid impacting us in the correct position and direction to blow off our angular momentum.

To visualise this, think of the skater again. To slow her spin down (and hurt her, I'm sure) you put a big block off to the side. She spins into it, and it stops the spin (and she gets a huge bruise probably)
Faizan
#7
May23-04, 12:39 AM
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Does this mean that the earth cannot orbit retrogradely, sooner or later?
AKG
#8
May23-04, 12:57 AM
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enigma

What about the effect or precession?
enigma
#9
May23-04, 03:10 AM
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Faizan, no. The Earth cannot orbit in a retrograde direction.

AKG, precession doesn't change the spin direction. It just changes the 'north' direction. Think of a top. The top always spins in the same direction. The north direction just wobbles.
ceptimus
#10
May23-04, 04:41 AM
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Concorde passengers, on certain flights could watch the sun rise in the west. This was due to Concorde's westward speed being higher than the eastward speed of the land due to the earth's rotation.

Now that Concorde doesn't fly anymore, only military jet pilots probably get to see this effect.
russ_watters
#11
May24-04, 02:53 PM
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Fazian, I think you might be mistaking the retrograde motion of Mars across our sky for an actual change in the direction of its orbit. The retrograde motion of Mars across our sky is a quirk of geometry - the actual orbit of Mars is stable.

http://marsprogram.jpl.nasa.gov/alla...ightsky04.html
Njorl
#12
May24-04, 03:01 PM
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The magnetic poles might flip. In that case, they will either have to reprint all of the magnetic compasses, or just decide that the Atlantic Ocean is the west coast of the US. In the latter case, the sun will rise where it always did, but it will be called west.
Integral
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May25-04, 07:41 AM
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Quote Quote by Njorl
The magnetic poles might flip. In that case, they will either have to reprint all of the magnetic compasses, or just decide that the Atlantic Ocean is the west coast of the US. In the latter case, the sun will rise where it always did, but it will be called west.
That would be rude! To wake up one morning to find that I am now on the East coast! Do you suppose the weather would follow?
Njorl
#14
May25-04, 08:38 AM
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Quote Quote by Integral
That would be rude! To wake up one morning to find that I am now on the East coast! Do you suppose the weather would follow?
Not the weather, but the attitudes will change. You will become a rude and dour workaholic, while I will wear "JAMS" and ride a boogie board to work.

Njorl
Andre
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May25-04, 10:44 AM
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Now, lets have a look at the complete system. The sun rises in the west at Venus, for a day length of about 60 Earth days.

The solar system is supposed to be chaotic. With resonance acting between precession of planets, their obliquity and the eccentricity all interacting. When the freqencies get within resonance ranges extreme things happen to the orbit and spinning axis. Due to these effects Venus may have toppled in the past, causing it's retrograde spinning.

Due to the moon gravtiy, the precession of the equinoxes (26,000 years) is much faster than the obliquity cycle (41,000 years). But as the moon recedes and the Earth spinning slowly decays, decreasing the equatorial bulge, the precession slows down and within a few billion years it will be in resonance with the obliquity cycle. Who is alive then, will be able to note if that it could tilt the Earth axis upside down. It will not be funny to live then.

The big guru on these matters is Prof Laskar in Paris.
Cecil
#16
May26-04, 04:16 PM
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Quote Quote by Njorl
The magnetic poles might flip. In that case, they will either have to reprint all of the magnetic compasses, or just decide that the Atlantic Ocean is the west coast of the US. In the latter case, the sun will rise where it always did, but it will be called west.
***Pedantic mode on***

The geographic north pole of a planet is defined such that the planet rotates west to east. Magnetic north may - and will - shift sooner or later, but the Atlantic Ocean will always be off the east coast.
Nasirz
#17
Jun6-04, 08:58 PM
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hello faizan
sunrise from the west

Now I express some of the encyclopedic facts about the rotation and magnetic field of the earth to judge the possibility of the rising of the sun from the west.
(1) Talking about the motion of the earth and the attraction of the other planets over it, the Chamber's Encyclopedia says, " In reality however the attraction of the other planets cause the whole orbit to rotate round the sun and to undergo slow changes in shape and size...that is the orbit fluctuates in shape and size."
(2) The Encyclopedia of Science and Technology says, "Never it is well established that the Earth's magnetic field does originate predominantly in the deep interior.
(3) Now it is well known that, "The Earth's magnetic field is gradually changing with time in its intensity as well as in its distribution pattern."
(4) The fraction of the Earth's magnetic field produced by outside sources is now understood to be an important representation of the electro magnetic activities in the Earth's upper atmosphere.
(5) The moons gravitational forces also gives rise to a tidal current in the ionosphere, just as it does in the ocean water consequently a lunar ionosphere dynamo also exists.
(6) Near the Earth the magnetic field is compressed and neutralized in an outward direction, and thus the magnetic filed is confined within a limited space surrounding the Earth. This limited space and its outer boundary are called the magnetosphere and the magnetopause of the Earth.
(7) It was believed that the outer space beyond the Earth's atmosphere is a perfect vacuum but it is established that the solar corona extends beyond the Earth's orbit, the space between the Sun and the Earth is filled with plasma gas called the solar wind. During a period of low solar activity (quiet sun), the solar wind flows radically outward from the Sun at the speeds 186-311 miles per second. Electrons and positive ions in the solar wind when approach the Earth, are repelled by the magnetic field of the Earth, yet they reach a region where the kinetic pressure of the solar wind and the pressure of the Earth's magnetic field are in equilibrium.
Phobos
#18
Jun8-04, 04:00 PM
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Quote Quote by Njorl
You will become a rude and dour workaholic,
hey, who you callin' a workaholic?

east-coast-Phobos


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