Why does the Earth rotate around the sun?

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In summary, it is said that sun pulls on Earth by gravity. But then I am told that Earth rotates round sun because of space distortion by sun.
  • #1
sneez
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It is said that sun pulls on Earth by gravity. Here 'gravity' i mean some attractive field mediated by something. (Newton theory i guess)

But then I am told that Earth rotates round sun because of space distortion by sun. (the famous rubber sheet example)

Which one is it?

and How does the search for gravitons go with the curved space hypothesis [why do we look for them if gravitational attraction is only illusion caused by curved space] ? How does the curved space produce tidal effects on moons rotating planets?

and if its not too much, How/what/why produces this curvature in space? [Does the graviton act on space or would the graviton act directly on the object?]

Even little bit of clarification is appreciated
 
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  • #2
in 8th grade science i was told that the planets rotate because of the way the dust-disk that all planets were formed from rotated in the same direction around the sun. (or something like that, my memory is bad and so was my teacher)

Except Venus, which was supposedly hit by one of the original prototype planets that caused it to tip over and switch rotation
 
  • #3
Stick with Newtonian gravitation right now, space distortion is a relativistic concept.
 
  • #4
I agree with Werg22, If you're just learning, stick with Newton's gravity; it explains enough so that you can get a grasp fo what's happening, make accurate predictions, etc.

But just keep in mind that the "rubber sheet example" makes all the same predictions, and is a slightly better understanding (for those to whom Newton's "force" of gravity isn't good enough).
 
  • #5
The Earth revolves around the sun, because it does.

Newton found that he could predict the positions of heavenly bodies by using a central force he called gravity.

Einstein found that he could model the same system by assuming that space is curved by massive bodies. The fact is that Einstein's model is more general and works over a wider range of conditions then Newtons model. What we have found, is that Newtons model is an approximation to Einstein's and can be arrived at by dropping "extra" terms that show up when using Einstein's model.

So as long as you are aware of what conditions are suited to Newtons laws they are useful and accurate. Einstein's theory yield more accurate results in all cases but they are much harder to apply. In the world we live in very precise measurements are required to separate the two models.
 
  • #6
Well, i appreciate responses but i would like to know what is theory about the apparent contradiction?

If space is curved and [as I am told einstein incorporates Newton theory in it], what would be the role of gravitons? And how curvature alone can produce tidal effects on planets? Streching to me is force, i don't understand how curvature can produce force? [i understand i can produce apparent force, ie. two man walking on parallel longitudes on a sphere].

Is there anyway to explain these to me without relativistic math?
 
  • #7
That image of two men walking is a good place to start. Suppose those two men were trying to carry one object by holing on to both ends. As each man walks along his own line of longitude, the load they share gets stretched.

In a similar way, the side of the Earth that is closest to the Sun travels through a space that is slightly more curved than the side that is farthest away from the Sun. It is the difference between these two curves that causes tidal forces (the stretching of the Earth's surface).
 
  • #8
sneez said:
How does the search for gravitons go with the curved space hypothesis [why do we look for them if gravitational attraction is only illusion caused by curved space] ?

This definition of a graviton may help with part of your question:

In physics, the graviton is a hypothetical elementary particle that transmits the force of gravity in most quantum gravity systems. In order to do this, one theory posits that gravitons have to be always-attractive (gravity never pushes), work over any distance (gravity is universal) and come in unlimited numbers (to provide high strengths near stars). In quantum theory, these requirements define an even-spin (spin 2 in this case) boson with a rest mass of zero.

en.wikipedia.org/wiki/Graviton

And I thought a graviton was an increment of measurement measuring the amount of gravity caused by n amount of mass. Wrong?
 
  • #9
sneez said:
Well, i appreciate responses but i would like to know what is theory about the apparent contradiction?
What apparent contradiction? It just seems to me that you don't understand the issue...
If space is curved and [as I am told einstein incorporates Newton theory in it], what would be the role of gravitons?
Those are questions that physics is still trying to answer, and at your level of knowledge it may be best to leave them alone for now, as others suggested.
And how curvature alone can produce tidal effects on planets? Streching to me is force, i don't understand how curvature can produce force? [i understand i can produce apparent force, ie. two man walking on parallel longitudes on a sphere].
The curvature is not easy to visualize, so it is best to use analogies such as the bowling ball on a trampoline. A marble placed near a bowling ball will get "pulled" toward the bowling ball due to the curvature of the trampoline. Two marbles placed different distances from the bowling ball will be pulled with different forces. The difference between those forces (which can be felt if you connect the marbles with a string) is the tidal force.
 
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  • #10
Integral said:
The Earth revolves around the sun, because it does.
This is an answer not to be passed by too quickly.

It is important that you recognize that both Newton's and Einstein's theories are simply models that we use to make predictions. Newton's is an excellent predictor in 99% of circumstances, but Einstein's is more like 99.9%. Neither actually claims to be the actual cause of the Earth going round the Sun.


As to what actually causes the Earth to revolve around the Sun, well, that's a question for future physicists.
 
  • #11
and what explains the Earth's motion around its own axis? ..I read that Earth rotates aroun the c.m of the earth-moon system which lies within the Earth itself , so Earth rotates arnd its own axis...is it true??..
 
  • #12
Well, the Earth's rotation and the moon's existence/orbit are likely unrelated as the Earth and moon probably did not form from the same disk of material (iirc, the leading current theory is that the moon was formed from the debris of an asteroid colliding with the earth).

But, the Earth's rotation and its revolution around the sun do have the same cause: the gravitational collapse of an asymetric cloud of debris induces a torque and thus the rotation and revolution of the earth. That's why most planets rotate in the same direction as they revolve.
 
  • #13
hey dudes ... i am not any genius or any thing .... but would like to think a lot and i got this strange feeling that Earth revolves around sun because it obeys gyroscopic effect ...... i mean to say that as Earth rotates around its own axis...this will cause the Earth to rotate around sun......

this can be seen in many experiments conducted by Eric Laithwaite ... any object revolving around its own axis...would be traveling in a path ... like Earth revolving around sun...
 
  • #14
rathlawath said:
hey dudes ... i am not any genius or any thing .... but would like to think a lot and i got this strange feeling that Earth revolves around sun because it obeys gyroscopic effect ...... i mean to say that as Earth rotates around its own axis...this will cause the Earth to rotate around sun......

this can be seen in many experiments conducted by Eric Laithwaite ... any object revolving around its own axis...would be traveling in a path ... like Earth revolving around sun...

So how does one explain Mercury, which rotates in the opposite direction to its revolution. Hamster wheel?
 
  • #15
Okay so here is a question for the physics types on here: The spinning Earth generates a magnetic field. I am assuming that other spinning planets/the sun generate a magnetic field. The question is, wouldn't this contribute to an attraction or a repulsion of the planets towards or away from one another (in the same way that wires with currents through them attract or repel each other)? I realize the distances between planets are quite large and the magnetic force between planets might be very weak, but even a small change in the orbit of these planets could cause a collapse towards one another...so why doesn't this happen?
 
  • #16
Renge Ishyo said:
Okay so here is a question for the physics types on here: The spinning Earth generates a magnetic field. I am assuming that other spinning planets/the sun generate a magnetic field. The question is, wouldn't this contribute to an attraction or a repulsion of the planets towards or away from one another (in the same way that wires with currents through them attract or repel each other)? I realize the distances between planets are quite large and the magnetic force between planets might be very weak, but even a small change in the orbit of these planets could cause a collapse towards one another...so why doesn't this happen?
1] The Earth's magnetic field is not caused by its spin.
2] The magnetic field is bipolar, meaning is has both north and south. The net effect is zero.
3] Gravity drops off as the square of distance. Magnetic fields drop off as the cube of the distance. i.e. at an arbitrary distance x, if the gravitational force has dropped off to 1/100th, the magnetic field will have dropped of to 1/1000th. If gravity is 1/1000th, then magnetic field is 1/31,617th.

And after all that,
4] Who says it isn't having an effect? Planets are perturbed all the time by each other and by jets of gas and energy from the sun. These are taken intro account. They do not send planets spinning out of control on collision courses.
 
  • #17
A couple of Q's on these:

1] The Earth's magnetic field is not caused by its spin.
2] The magnetic field is bipolar, meaning is has both north and south. The net effect is zero.

1. At least when I last learned it, the magnetic field is proposed to be generated by liquid metal moving in a circular pattern near the Earth's core. Of course, for all I know this view might be outdated.
2. I thought all magnets have both a north and south pole? Or is this idea outdated too (<---- feels old).
 
  • #18
Yes, all magnets have a north and a south pole. I can't comment on the origin of the Earth's magnetic field except to say that just metal moving in a circular pattern wouldn't create one- there would need to be a motion of net charge.
 
  • #19
muppet said:
Yes, all magnets have a north and a south pole. I can't comment on the origin of the Earth's magnetic field except to say that just metal moving in a circular pattern wouldn't create one- there would need to be a motion of net charge.
For Earth's magnetic field I would imagine it more like a sea of liquid metal (iron perhaps?) rather than a synchronized flow influenced by convection currents and such. As far as science knows all magnets must have two poles since a monopole has not been discovered nor created yet.
 
  • #20
rathlawath said:
hey dudes ... i am not any genius or any thing .... but would like to think a lot and i got this strange feeling that Earth revolves around sun because it obeys gyroscopic effect ...... i mean to say that as Earth rotates around its own axis...this will cause the Earth to rotate around sun......

this can be seen in many experiments conducted by Eric Laithwaite ... any object revolving around its own axis...would be traveling in a path ... like Earth revolving around sun...
Wholly incorrect.
I assume that you are speaking of the Magnus effect, which makes a rotating ball curve its path.

The Magnus effect requires that the ball to rotate in a fluid (like the air), and is generated by the pressure differential set up in that medium.

Now, to be sure, the space-time of Einstein is not some sort of Newtonian rigid box, but you'd certainly not get at Earth rotation velocities effects like the Magnus effect out of general relativity.
 
  • #21
H0T_S0UP said:
For Earth's magnetic field I would imagine it more like a sea of liquid metal (iron perhaps?) rather than a synchronized flow influenced by convection currents and such. As far as science knows all magnets must have two poles since a monopole has not been discovered nor created yet.

Also, one of Maxwell's equations states that there are no magnetic monopoles! Some particle theorists expect them to exist, but there'd be a Nobel prize for anyone who can find one...

The point of my post above was that a "sea of liquid metal" would not create a magnetic field. You need a motion of particles with a net charge, otherwise any spinning object would create a magnetic field, even if it were made of wood.
 
  • #22
This is my own difficulty.

Our local group of galaxies goes around another local group in a space time 'disturbed bowl'
Our galaxies in our local group go around each other in a disturbed spacetime bowl
Our sun goes around our galaxy center of mass in a bowl
Our planets go around the sun center of mass in a bowl
Our moon goes around the Earth center of mass in a bowl.

If space time were truly curved - like how a picnic blanket is curved by a bowl of potatoe salad - then the sun would be in a distorted dent, on the side of the galaxies dent, on the side of the local groups dent, on the side of a cluster dent, etc. etc. That would make all the planets go around in some sort of tilted odd path.. and none of this whole 'how mass displaces space like a bowl' shows why it does that nor the particle 'thing' that portrays that influence. I just find it too simple minded and innocent. Not to mention how right now we're on a rock, going around a star due to a spacetime dent, on the outter portion of another curved dent, on the outter portion of another curved dent, etc. But Truth is my greater friend - I just can't think of a way to see if this is true for myslf.
 
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  • #23
eratosthenes:
GEneral relativity will only create a pseudo-Euclidean space-time LOCALLY, to naively extrapolate beyond such locally "sensible" geometry will simply lead you nowhere.
 
  • #24
magnetic reversal

Renge Ishyo said:
Okay so here is a question for the physics types on here: The spinning Earth generates a magnetic field. I am assuming that other spinning planets/the sun generate a magnetic field.

Hi Renge! :smile:

http://en.wikipedia.org/wiki/Earth's_magnetic_field#Magnetic_field_reversals
Based upon the study of lava flows of basalt throughout the world, it has been proposed that the Earth's magnetic field reverses at intervals, ranging from tens of thousands to many millions of years, with an average interval of approximately 250,000 years. The last such event, called the Brunhes-Matuyama reversal, is theorized to have occurred some 780,000 years ago.

So the direction of the Earth's spin has nothing to do with the direction of the Earth's magnetic field. :smile:

See also http://en.wikipedia.org/wiki/Geomagnetic_reversal
 
  • #25
arildno said:
Wholly incorrect.
I assume that you are speaking of the Magnus effect, which makes a rotating ball curve its path.

The Magnus effect requires that the ball to rotate in a fluid (like the air), and is generated by the pressure differential set up in that medium.

Now, to be sure, the space-time of Einstein is not some sort of Newtonian rigid box, but you'd certainly not get at Earth rotation velocities effects like the Magnus effect out of general relativity.
i think gyroscope has nothing to do with magnetism......i just mean to tell about the rotation based on gyroscope.......
 
  • #26
So the direction of the Earth's spin has nothing to do with the direction of the Earth's magnetic field.

We can't say that yet; we have no idea what actually happens when a magnetic field reversal occurs (or for that matter why the direction of the field reverses itself periodically throughout the planet's history). If you try to apply conservation of angular momentum to the problem you run into all kinds of trouble...it seems unreasonable to believe that the Earth as a whole slows down and starts spinning in the opposite direction, but it seems just as unreasonable to suppose that a mere section of the Earth (charged "liquid metal" or what have you) will slow down and start spinning in the opposite direction while the rest of the Earth (including the layers surrounding the "liquid metal") keeps spinning in the previous direction unaffected.
 
  • #27
sneez,

I think you could say that the mass of the sun creates gravity, which curves or warps space-time. I'm pretty sure that this curavture is real because I've heard of an experiment done by astrophysicists during an eclipse where they were able to see a star that was behind the eclipse because the gravity of eclipse caused light from star to curve around the eclipse making the star visible. I'm not sure exactly how accurate what i said is, but maybe someone who knows more about this experiment can reply.
 
  • #28
Renge Ishyo said:
We can't say that yet; we have no idea what actually happens when a magnetic field reversal occurs (or for that matter why the direction of the field reverses itself periodically throughout the planet's history). If you try to apply conservation of angular momentum to the problem you run into all kinds of trouble...it seems unreasonable to believe that the Earth as a whole slows down and starts spinning in the opposite direction, but it seems just as unreasonable to suppose that a mere section of the Earth (charged "liquid metal" or what have you) will slow down and start spinning in the opposite direction while the rest of the Earth (including the layers surrounding the "liquid metal") keeps spinning in the previous direction unaffected.

The core is suspended in liquid like metal so in reality the center of our Earth is just floating around on liquid rock. What happens is that the core will sometimes do a flip and reverse the poles. There is evidence of this in the past and it occurs once every ~25000 years. Whats cool though is that 2012 will be ~25000 from the last magnetic pole switch!
 
  • #29
H0T_S0UP said:
There is evidence of this in the past and it occurs once every ~25000 years. Whats cool though is that 2012 will be ~25000 from the last magnetic pole switch!
You've been duped.

1] There's no pattern to the reversals, their durations vary wildly.
2] The most recent is more like 730,000 years ago. The number 25,000 (off by more than an order of magnitude) is pulled out of thin air to lend false credence to the whole http://en.wikipedia.org/wiki/2012#Metaphysical_predictions".

http://www.pbs.org/wgbh/nova/magnetic/images/timeline.gif
http://upload.wikimedia.org/wikiped...px-Geomagnetic_polarity_late_Cenozoic.svg.png

Please tell me you're not a 2012 woo-woo-er.
 
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  • #30
Please tell me you're not a 2012 woo-woo-er.

I'm not a 2012 woo-woo-er.
 
  • #31
Renge Ishyo said:
I'm not a 2012 woo-woo-er.
No, but HOT_SOUP might be.
 
  • #32
sneez,

whoops. This experiment just proves that gravity can bend light, not that space is curved.
 
  • #33
bending of light

ucf-fisher21 said:
whoops. This experiment just proves that gravity can bend light, not that space is curved.

Hi ucf-fisher21! :smile:

No, because light has mass (though not rest-mass), so even without space curvature it would be bent by gravity.

You can calculate that general relativity (with curvature of space) produces twice the bending expected without space curvature.

And that experiment did indeed verify (very approximately) the higher figure.

In other words, it proved that gravity can bend light and that the bending is caused by something more than "flat" gravity. :smile:
 
  • #34
tiny-tim,

this space curvature...is it the space-time 'fabric' that is being curved? If so, how is time affected?

also, in what dimensions is this curvature taking place?
 
  • #35
Hi ucf-fisher21! :smile:
ucf-fisher21 said:
tiny-tim,

this space curvature...is it the space-time 'fabric' that is being curved?

Yes, "flat" gravity would be in "flat" space-time fabric.

Experiments show that space-time fabric is curved. :smile:
If so, how is time affected?

Well, the stronger the curvature, the slower time goes … but I don't know a simple explanation for that. :redface:
also, in what dimensions is this curvature taking place?

"Curved" just means that the geometry isn't Euclidean (flat).

It doesn't mean that there's some higher-dimensional flat space in which "real" curvature can be seen.

It's just a word. :wink:
 
<h2>1. Why does the Earth rotate around the sun?</h2><p>The Earth rotates around the sun due to the force of gravity. The sun's massive size creates a gravitational pull on the Earth, causing it to orbit around the sun.</p><h2>2. How long does it take for the Earth to complete one orbit around the sun?</h2><p>The Earth takes approximately 365.24 days, or one year, to complete one orbit around the sun. This is why we have leap years every four years to account for the extra 0.24 days.</p><h2>3. What causes the Earth to rotate on its axis?</h2><p>The Earth's rotation on its axis is caused by its initial spin when it was formed, as well as the conservation of angular momentum. As the Earth formed, the particles that made up the planet were spinning, and this spinning motion has been maintained over time.</p><h2>4. Is the Earth's rotation around the sun perfectly circular?</h2><p>No, the Earth's orbit around the sun is not a perfect circle. It is slightly elliptical, meaning that at certain points in its orbit, the Earth is closer or farther away from the sun. This is due to the gravitational pull of other planets and objects in the solar system.</p><h2>5. Does the Earth's rotation around the sun affect the seasons?</h2><p>Yes, the Earth's rotation around the sun does affect the seasons. The tilt of the Earth's axis as it orbits the sun is what causes the change in seasons. When the northern hemisphere is tilted towards the sun, it experiences summer, while the southern hemisphere experiences winter. As the Earth continues its orbit, the tilt changes, causing the seasons to change as well.</p>

1. Why does the Earth rotate around the sun?

The Earth rotates around the sun due to the force of gravity. The sun's massive size creates a gravitational pull on the Earth, causing it to orbit around the sun.

2. How long does it take for the Earth to complete one orbit around the sun?

The Earth takes approximately 365.24 days, or one year, to complete one orbit around the sun. This is why we have leap years every four years to account for the extra 0.24 days.

3. What causes the Earth to rotate on its axis?

The Earth's rotation on its axis is caused by its initial spin when it was formed, as well as the conservation of angular momentum. As the Earth formed, the particles that made up the planet were spinning, and this spinning motion has been maintained over time.

4. Is the Earth's rotation around the sun perfectly circular?

No, the Earth's orbit around the sun is not a perfect circle. It is slightly elliptical, meaning that at certain points in its orbit, the Earth is closer or farther away from the sun. This is due to the gravitational pull of other planets and objects in the solar system.

5. Does the Earth's rotation around the sun affect the seasons?

Yes, the Earth's rotation around the sun does affect the seasons. The tilt of the Earth's axis as it orbits the sun is what causes the change in seasons. When the northern hemisphere is tilted towards the sun, it experiences summer, while the southern hemisphere experiences winter. As the Earth continues its orbit, the tilt changes, causing the seasons to change as well.

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