The earth's orbit, perpetual motion?

If we look at the earth orbiting the sun, it maintains its orbit in spite of the gravitational force stemming from both the sun and the earth. If we look at space junk sent up into orbit by humans, it will eventually fall to earth. This is caused by upper atmosphere friction slowing the space junk velocity until the balance between its velocity and gravity is broken. But the earth is in the upper atmosphere of the sun, so to speak. This is called the solar wind. The question becomes, where does the earth get the energy to overcome the friction and maintain a perpetual orbit?

Gravity is often associated with the curving of space/time. This has been used to explain the earth's orbit around the sun. This raises an interesting conceptual point. The orbit of the earth is elliptical; we are closer to the sun during the northern winter. Does this mean that we will alter our reference cyclically through the year, since we vary our position within the warping of space/time cause by the sun?

The elliptical orbit also implies that there two foci in the earth's orbit. Essentially, the orbit reflects what one would expect from two centers of gravity. The variable earth velocity would imply one center of gravity stronger than the other. This anomaly is somehow connected to the energy source needed to maintain a perpetual orbit within the friction caused by the solar wind.

WAAAAYYYY back, a supernovae exploded, and sent out the detritus that eventually became Earth. This detritus has a momentum from the explosion.

Earth (or its precursor) was captured by the Sun's gravity. The orbit of Earth around the Sun is slowly bleeding off the momentum of the original explosion. It's a slow process, but you can be assured that it's occuring.

So no, there is no perpetual motion. The energy from the original explosion is keeping us from falling into the Sun (essentially fighting the gravity)

a piece of space debris when subjected to the friction of the upper atmosphere is influenced more greatly compared to the earth and the friction it is subjected to by the "upper atmosphere" of the sun. also the piece of space debris is much closer to the earth and therefore the friction much greater than the earth being so far away from the sun, and therefore a comparatively weaker friction.

a better analogy, not necessarily accurate, would be the moon and earth rather than a piece of space debris.

Then why is the moon moving away from the earth?

Hi Zeven

The transfer of Earth's rotational energy/velocity to the Moon's orbital energy/velocity via gravitational tides.

If the earth is transferring this momentum to the moon that means the earth must be losing momentum.

One of the theories to help form the iron core of the earth is connected to a period of intense asteroid activity that builds up the iron core. The sun's gravity helped pulled these asteroids inward with the earth taking a beating. The primary direction of momentum transfer, should have net pushed the orbit of the earth toward the sun. How did the orbit of the earth stabilize instead of decaying into the sun? If the asteroid theory is moot this would be a moot question.

The Earth could also be an aggregation of asteroids, as well, and our current orbit is the net sum of the momentum transfer.

(The theory that planets are made up of asteroids is one reason why people are so excited about harvesting asteroids ... all those 'yummy' metals that are too deep in the Earth would be the main composition of some asteroids. I recommend www.permanent.com for more information.)

Isn't it true that past knowledge is corrected when we find new data. I believe as time passes, that what is now thought to be fact, will indeed be corrected later. It just may be, that all is kept in check due to gravitational pulls versus magnetic repelling. It is, because it is, and is not where it started/or ended. We're caught in a loop of sorts, like a whirlpool. The rest is debris and natural corrosion. Galaxy upon galaxy is both collapsing and spinning off debris simultaneously. A perpetual state of decay and renewal. Possibly the result from the matter/anti-matter collision long ago...which distorted the then known universe into what is now. Or not.

Where was this supernova located when it exploded? The assumption is that the sun was already here, which I can accept. The nearest star now is 1 or 2 light years away and the nearby galaxies are contracting. Say we put that supernova in the middle, between the sun and the closet star, without any adjustment due to any contraction since then, It appears like we would get slim pickings to form the earth, especially with the sun taking the lion's share.

In other words, if the sun went supernova, the crap would go everywhere. By the time it reached even Pluto, we wouldn't have enough density for a tiny moon. If we place the supernova, 1 light year away, its local density would fit on the head of pin.

What is wrong with the good old fashion notion of the sun and the planets all forming at the same time from the same cloud of primal hydrogen/helium?

Because then we would question where the heavy elements came from. The sun (the largest fusion reactor around) has heavy elements in it, but how would you compress the earth out of hydrogen? You can't.

The heavy elements are a product of fusion, ergo, you need a fusion reactor to produce them. That fusion reactor was an older sun, gone supernovae.

(You'll also note that a lot of star have planets, so the chance of proto-Earth being captured by Sol seems to be low, the chance of it being captured by something is quite high).

Hi MDT et al,

It is a question of systems. Apparent movement is not aceleration. Particles will follow geodesics in space-time if they are in an inertial frame of reference. These are the equivalent of "straight lines" when you take Special Relativity and "mix" it with General Relativity. The same with "electrons in orbits around atoms". I have seen all the claptrap about this and they all ignore Einstein and Special and General Relativity to interpret it for them. It seems to be a mystery to them. I suppose they have axes to grind. Quantum Physics is "off the rails" by not taking Einstein's Theories "at face value"... all the way.

The Earth forms a system that is "at rest". Systems at rest have no energy to exchange. All inertial frames are "at rest" relative to the rest of the inertial frame (it is a postulate). Of course you can initiate new systems. What I mean by "system" is Energy itself is not absolute it must be related to a system. The energy of a ball at the top of a cliff is different to a ball at the bottom of a cliff (even if the ball does nothing) since its "energy" must be related to the cliff which is part of the system. So long as the earth "system" remains "at rest" even locally, the Earth will not radiate energy and spiral into the Sun. The curved path you see is due to General Relativity and is a geodesic. The re-entering Space garbage forms another system with the Earth and the energy given up to it is both Kinetic and Potential in nature, just like all energy. Luckily this is "small beer" for the Earth. I know that the Earth has mass and curves space-time but it does this by conservation of its 4-momentum. All forces are internal. We discussed this point for quanta in the Milo Wolff Thread.

Cheers

Hi Good Elf. Here is a related question. The solid core of the earth was found, by NASA, to rotate faster than the surface of the earth. With the earth continuous visco-plastic, until the faster rotating solid core, where does the energy come from to overcome friction? The heat generated by the friction could account for material movement toward the surface. This heat s radiated through volcano's and lava flows. Yet the system remains closed or energy balanced for its perpetual orbit. So where is the core energy coming from to maintain the balance?

I have copied and pasted this question from the previous comment. The question below is:

The question becomes, where does the earth get the energy to overcome the friction and maintain a perpetual orbit?

We all seem to agree (looking at previous comments and accurate information, that there is a grey area here that nobody can quite explain where the earth gets the energy to overcome friction and maintain a perpetual orbit.

I offer up this simple explanation. There is a perfectly working system that can easily become helpless without the exact sequence of events taking place yet we know that often things should have crashed and did not - why? Are we overlooking the power of the general electricity and adaptability of the human force involved to fill in the floating gaps that need to be fed but have the flexibilty when fed to transform into the power needed to hold up a perpetual orbit. In other words, it is not a set formula that when broken will fail. It is a brilliant sequence that allows for efficient addaptation when sufficiently filled. Perhaps we have interpreted 'overcoming friction' as just that, a task and must.
Perhaps it isn't a question of overcoming the friction on a regular basis, as it does,
but to have a built in coping system that can accomodate times of not enough friction yet function on target and without a lapse. Are we assuming that once a pattern is set that any change would alter that course? Please forgive the simplicity, but the perpetual orbit is not due to overcoming friction but to accomodating for it!

According to general relativity, the planetary orbits will decay since the bodies are radiating away gravitational potential energy.

z

What causes speedup in free fall?(Where you're not following a curve)

We have an answer to why there is a change in direction aka curvilinear motion. It is the curvature of space. But why should space-time curvature accelerate objects?
The machinery for changing direction is present but not speed up. And if you believe it is time then how does time move objects?