Why do the earth spin araund the sun?

[jonsson]

yes it migth be a simple question (or not) but im 15 and not som damn brainy astronom

 

well, thise has bugged me some time, why dose it realy do that, why dose the earth spin araund the sun?

 

usealy you just get the answer "gravity!" but if i understand it rigth gravity would make the eart crash into the sun, but it spinns making centrifugal force or what its calld creating a midstate of not geting flung oute into the nothingnes and not crashing into the sun. (lagom is da shitz^^)

 

but iv never got the question why dose the earth spin to startwhite? why did it start?

 

so can anyone answer it and put me oute of my missery (and yeah im 15 so dumb it down abit )

 

oh and sorry for the spelling and grammar and what not, think i got dyclexi or somethign whene it comes to that :/

[insane_alien]

well, the earth and sun actually orbit what is known as the barycenter. basically the center of mass of the earth-sun system.

 

as the sun is so massive compared to the earth, the center of mass is deep within the sun.

 

also, the earth is continually falling into the sun, it is just we have enough sideways velocity that we keep missing it. the quote from hitchikers guide to the galaxy 'you just need to throw yourself at the ground and miss' isn't really as silly as it sounds as it perfectly describes an orbit.

 

the earth started going round the sun because the dust and rocks from which it formed was going round and round the sun. it was just conservation of momentum.

[swansont]

Some things do fall into the sun. But if the object is moving in the right direction with the right speed, it will continually miss — these are stable orbits.

[ydoaPs]

The red squiggly line means you made a spelling error.

[Sisyphus]

Orbits, like the Earth's around the Sun, have two parts: gravity and inertia. Inertia is what makes everything keep moving in a straight line at the same velocity forever unless something stops it. Gravity is what accelerates objects with mass towards one another.

 

Take the Earth, put it some distance away from the Sun, and give it a push at a right angle to the direction of the Sun. The gravity of the Sun will pull it in, but because the Earth is already moving sideways, the direction of the gravitational pull is constantly changing. The result is a curved, and eventually circular path. The Earth is constantly falling towards the sun, it just doesn't get any closer because the direction of "falling" is constantly changing. Kind of like how if you have a weight on a string and spin it around, you have to pull on it to keep it from flying away. If you let it go, it would fly off in a straight line in whatever direction it was moving when you let it go. That "pulling" is gravity in an orbit. What makes it fly off in a straight line is inertia.

 

As for how it got started in the first place, that's a whole other question. Basically the whole solar system was formed when a huge cloud of gas collapsed in on itself because of gravity, and the slight spinning of that cloud was magnified by conservation of angular momentum (the same reason that a figureskater can spin faster by pulling their arms and legs closer to themselves). Part of that spinning cloud formed the Earth, and there has been nothing to stop it spinning since.

[jonsson]

@insane_alien + Sisyphus

 

ahh, thanks and yeah, flying is the art of falling and missing the ground gues where i all my bruces comed from whene i was younger xD

 

@ydoaPs

 

oh how helpful, and just pointing oute that im swede and got swedish spell checing...

[matterdoc]

Every 'Astronomer' knows that the sun is a moving body. It is simple mechanics that no free body can orbit around another moving body in closed geometrical path. Yet why do every one say that earth orbits around the sun in elliptical path?

[swansont]

Every 'Astronomer' knows that the sun is a moving body. It is simple mechanics that no free body can orbit around another moving body in closed geometrical path. Yet why do every one say that earth orbits around the sun in elliptical path?

 

Because, like much of the way physics is done, it is approximately correct. And there's a lot you can do with an approximately correct model. The trick is in knowing the conditions under which it breaks down.

[pioneer]

Basically the whole solar system was formed when a huge cloud of gas collapsed in on itself because of gravity, and the slight spinning of that cloud was magnified by conservation of angular momentum (the same reason that a figureskater can spin faster by pulling their arms and legs closer to themselves). Part of that spinning cloud formed the Earth, and there has been nothing to stop it spinning since

 

The fundamental question then becomes why the original spin to the cloud in the first place? Gravity has its maximum pull radially toward the center of gravity, so why would much of matter begin to move (circulate) in a way that delays the inevitable collapse?

 

The circulation is not anti-gravity, but it does moves in a way that makes it harder for gravity to close the deal. This would suggest some form of output from the lowering of gravitational potential causing the gravity potential to increase elsewhere in the system; circulation that delays collapse. Another clue is although gravity will pull in 3-D the circulation defaults to 2-D.

 

This is all explained via the entropy spectrum.

 

If we had a cylinder of gas and opened the valve the cylinder and gas will get very cold. The increasing entropy of the expanding gas will absorb the energy. Next, we take the gas after it reaches ambient conditions and compress it. The energy within the entropy is released and the cylinder gets hot. The heat from the surface of cylinder, can heat the gas near the cylinder to increase it entropy. If we do this right, it will not just randomly heat up the surrounding air, but it will also set up a circulation sort of like chimney effect. The movement up of the warm air will then pull air in laterally near the cylinder. This is different aspect of the entropy spectrum based on cylinder geometry and heat rate.

 

Gravity will lower the entropy of the original solar system gas cloud by shrinking the container volume (gravity is a compressor). When entropy lowers, energy is given off, which can then increase the entropy elsewhere. In this case, the entropy spectrum is associated with orbital circulation.

[swansont]

The fundamental question then becomes why the original spin to the cloud in the first place? Gravity has its maximum pull radially toward the center of gravity, so why would much of matter begin to move (circulate) in a way that delays the inevitable collapse?

 

It doesn't begin to move under those conditions. It is already moving.

 

The circulation is not anti-gravity, but it does moves in a way that makes it harder for gravity to close the deal. This would suggest some form of output from the lowering of gravitational potential causing the gravity potential to increase elsewhere in the system; circulation that delays collapse. Another clue is although gravity will pull in 3-D the circulation defaults to 2-D.

 

It's called conservation of angular momentum.

 

This is all explained via the entropy spectrum.

 

If we had a cylinder of gas and opened the valve the cylinder and gas will get very cold. The increasing entropy of the expanding gas will absorb the energy. Next, we take the gas after it reaches ambient conditions and compress it. The energy within the entropy is released and the cylinder gets hot. The heat from the surface of cylinder, can heat the gas near the cylinder to increase it entropy. If we do this right, it will not just randomly heat up the surrounding air, but it will also set up a circulation sort of like chimney effect. The movement up of the warm air will then pull air in laterally near the cylinder. This is different aspect of the entropy spectrum based on cylinder geometry and heat rate.

 

Entropy does not absorb energy.

 

Gravity will lower the entropy of the original solar system gas cloud by shrinking the container volume (gravity is a compressor). When entropy lowers, energy is given off, which can then increase the entropy elsewhere. In this case, the entropy spectrum is associated with orbital circulation.

 

No. A change in entropy cannot, in and of itself, cause rotational motion. That requires a torque.

[ewmon]

As for how it got started in the first place, that's a whole other question. Basically the whole solar system was formed when a huge cloud of gas collapsed in on itself because of gravity, and the slight spinning of that cloud was magnified by conservation of angular momentum (the same reason that a figureskater can spin faster by pulling their arms and legs closer to themselves). Part of that spinning cloud formed the Earth, and there has been nothing to stop it spinning since.

aka Nebular Hypothesis which, interestingly, was first proposed by Swedish scientist Emanuel Swedenborg.

 

yeah, flying is the art of falling and missing the ground

I must add this to my collection of quotes.

 

and just pointing oute that im swede

And as a Swede, you used the word "lagom" in your OP (ie, just the right amount for the situation), and I thank you. I first experienced this word on Friday, October 16, 2009, but have only now experienced it for real. I think the reason why "lagom" is so ... uh ... cool, is because whatever isn't lagom tends to crash and burn, so lagom is inherent in the stability of the world around us. In other words, the [stable] situation survives for us to experience it because it involves the right amount of something. (I hope I haven't spoiled it for you.)

[swansont]

 

I must add this to my collection of quotes.

 

 

I take it you have not read The Hitchhiker's Guide to the Galaxy

[ewmon]

I take it you have not read The Hitchhiker's Guide to the Galaxy

 

I only got to page 41. I've led a very depraved deprived life.

[Ophiolite]

I only got to page 41. I've led a very depraved deprived life.

That is either a neat coincidence or elegantly clever.

[ewmon]

Never read it, but I've heard the answer to everything is 42. Elegantly clever? Moi??

[michel123456]

The fundamental question then becomes why the original spin to the cloud in the first place?

 

As far as I know, from existing theory, the Big Bang is the cause.

[swansont]

As far as I know, from existing theory, the Big Bang is the cause.

 

But that's both a very blunt instrument and not really correct. A gas cloud that collapses need not have any rotational motion; I don't think that it is mandated by the physics of the big bang, there are a number of intermediate steps from the big bang to the spin of the earth, and even of the big bang were somehow discredited, conservation of angular momentum would still hold. If there is locally any net angular momentum, this must still be present one the cloud has collapsed.

[pioneer]

Gravity works as a compressor of matter. It is more than just a contraction of space-time or else neutron density could not form. If gravity was only a contraction of space-time, the neutrons would not see themselves getting closer in their contracting reference. Since they need to get physically closer to form neutron density, in any reference, they need to become physically compressed even within their contracting space-time reference. The laws of physics being the same in all references means neutron density forms the same way in all references.

 

This means two components; one connected to GR and one to a reference independent compression so this law of physics becomes active. This compression will lower the entropy, since neutron density reduces the degrees of freedom of the neutrons. This will be exothermic. This energy output now has to deal with the space-time contraction as it leaves. If we are also heating matter, that is expanding out into the expanding space-time, there are two components to the expansion. If the laws of physics are the same in all reference, when I heat a gas it will expand regardless of reference. If the space-time reference is also expanding we get heat expansion within a space-time expansion. The summation is entropy increase.

 

The expansion in space-time implies more degree of freedom in time, since it can do more things for any given unit of simultaneous time. For example, say someone was throwing the dice. If I was watching a stationary and a contracted references each throw their dice, the stationary is throwing the dice faster, allowing it to cycle through the sides much faster. If instead of dice this was two similar assembly lines with 1% defects, the stationary will have more entropy since defect appear faster.

 

That being said, there is a dual but connected entropy output to add a twist.

[swansont]

Gravity works as a compressor of matter. It is more than just a contraction of space-time or else neutron density could not form. If gravity was only a contraction of space-time, the neutrons would not see themselves getting closer in their contracting reference. Since they need to get physically closer to form neutron density, in any reference, they need to become physically compressed even within their contracting space-time reference. The laws of physics being the same in all references means neutron density forms the same way in all references.

 

This means two components; one connected to GR and one to a reference independent compression so this law of physics becomes active. This compression will lower the entropy, since neutron density reduces the degrees of freedom of the neutrons. This will be exothermic. This energy output now has to deal with the space-time contraction as it leaves. If we are also heating matter, that is expanding out into the expanding space-time, there are two components to the expansion. If the laws of physics are the same in all reference, when I heat a gas it will expand regardless of reference. If the space-time reference is also expanding we get heat expansion within a space-time expansion. The summation is entropy increase.

 

The expansion in space-time implies more degree of freedom in time, since it can do more things for any given unit of simultaneous time. For example, say someone was throwing the dice. If I was watching a stationary and a contracted references each throw their dice, the stationary is throwing the dice faster, allowing it to cycle through the sides much faster. If instead of dice this was two similar assembly lines with 1% defects, the stationary will have more entropy since defect appear faster.

 

That being said, there is a dual but connected entropy output to add a twist.

 

What does any of this have to do with the OP?

[michel123456]

But that's both a very blunt instrument and not really correct. A gas cloud that collapses need not have any rotational motion; I don't think that it is mandated by the physics of the big bang, there are a number of intermediate steps from the big bang to the spin of the earth, and even of the big bang were somehow discredited, conservation of angular momentum would still hold. If there is locally any net angular momentum, this must still be present one the cloud has collapsed.

 

Blunt it is. But why not really correct? As you said "If there is locally any net angular momentum, this must still be present(...)", and indeed, it is still present today.

[swansont]

Blunt it is. But why not really correct? As you said "If there is locally any net angular momentum, this must still be present(...)", and indeed, it is still present today.

 

How is conservation of angular momentum a consequence of this (or any) cosmological theory?

[D H]

Blunt it is. But why not really correct? As you said "If there is locally any net angular momentum, this must still be present(...)", and indeed, it is still present today.

It's incorrect because the angular momentum of the universe as a whole is most likely zero, and that is the angular momentum of the big bang.

[vuquta]

Because, like much of the way physics is done, it is approximately correct. And there's a lot you can do with an approximately correct model. The trick is in knowing the conditions under which it breaks down.

 

I would like to propose an experiment much like the GPS sagnac proves the earth is rotating.

Can we do this for the earth's orbit around the sun since this is a sagnac path with the radius being from the earth to the sun?

 

This would settle this problem.

Is this correct?

Edited September 22, 2010 by vuquta

[swansont]

I would like to propose an experiment much like the GPS sagnac proves the earth is rotating.

Can we do this for the earth's orbit around the sun since this is a sagnac path with the radius being from the earth to the sun?

 

This would settle this problem.

Is this correct?

 

!

Moderator Note

vuquta, stop hijacking threads with off-topic discussion

[michel123456]

It's incorrect because the angular momentum of the universe as a whole is most likely zero, and that is the angular momentum of the big bang.

 

I suppose your comment is correct under the BBT. But the question is not about the angular momentum of the universe as a whole, but the angular momentum of the Earth.

I have no knowledge of any other cause for the angular momentum of any celestial body.