Thread: The solar system

Is the earth spiraling towards the sun (like a ball on a small gravitywell) or is it staying in a perfect path. If nothing hit us, and nothing happened to the sun forever, would we slow down, or would we just keep going?)

Originally Posted by Shaderwolf

Is the earth spiraling towards the sun (like a ball on a small gravitywell) or is it staying in a perfect path. If nothing hit us, and nothing happened to the sun forever, would we slow down, or would we just keep going?)

The earth's orbital radius is actually increasing. Every few years, to account for this, we have to add an extra second on to the length of our year. Many millions of years from now we would expect the Earth's orbit to be a lot larger, and possibly that, due to tidal effects, the earth always shows the same side/face to the Sun. This will, of course, take some time, and we have the counteracting effect of the moon to assist in our continuing rotation.

Fear not, it's a long way away, though.

So, the radius is increasing. Does this happen every time you have one body orbiting another? I was wondering, if an object in space will keep moving once it starts (because there's no friction out there), and if it was moving in orbit around another object, could you orbit a magnet around some kind of non magnetic dense material? To do this, would the mass of the "anchor" have to be so great that it would be an impossible task? And if you got the object in a predictable orbit (like satelits around earth) could you build a coil of wire around that predicted orbit path, so that there is nothing touching? This all brings me to the final question. I know that a magnet moving through coils of wire produces electricity. That's elementary. Where does the energy come from? Will the magnet become weaker with time? Or will the magnet stop orbiting? Those are my two Ideas for where the energy originates... The motion and the electromagnetic field. How far off base am I?

There are formulas out there that says what size and density two objects have to be to have a sustained orbit, but I've forgotten what they're called. Orbits can either spiral inward or outward, but, more often, they're not simple spirals.

Also, you could orbit a magnet through a loop of wire if it weren't for one thing; a loop of wire all the way around a body doesn't feel that body's gravity at all (it cancels out in all directions). So the magnet could stay in orbit, but the wire couldn't. If you had it working for a while, the energy would come mostly from the motion, I think. Another way to do this though is to orbit a piece of wire through a sizable magnetic field, like the Earth's. They've done this. It produced enough power to break the wire.

Does that mean it is possible to generate power using rotational energy and the earth's magnetic field? The orbit would probably decay?

Does that mean Mars was earth-like?

How interesting.

Does that also mean the sun from time to time spews out a planet?

Very interesting.

Do you suppose we are biologically wired to work such a thing out though?

From theory?

What is wrong with you?

Originally Posted by sunshinewarrio

Originally Posted by Shaderwolf

Is the earth spiraling towards the sun (like a ball on a small gravitywell) or is it staying in a perfect path. If nothing hit us, and nothing happened to the sun forever, would we slow down, or would we just keep going?)

The earth's orbital radius is actually increasing. Every few years, to account for this, we have to add an extra second on to the length of our year. Many millions of years from now we would expect the Earth's orbit to be a lot larger, and possibly that, due to tidal effects, the earth always shows the same side/face to the Sun. This will, of course, take some time, and we have the counteracting effect of the moon to assist in our continuing rotation.

Fear not, it's a long way away, though.

Hypothesis is an essential ingredient to scientific inquisition.

Was Mars on this Earth-like orbit, a long time ago (obviously)?

I have nothing to do with that question.

Am I wrong or is the question?

More like it. It is very difficult to sometimes figure out if you are asking a serious question or merely talking in riddles.
Did mars once occupy an orbit similar to the current one of the earth? Doubt it. Too little time has passed for mars to migrate that far. Likely question.

Does the sun spit out planets from time to time? No. Ridiculous question, as you well know.

Originally Posted by KALSTER

Does that mean it is possible to generate power using rotational energy and the earth's magnetic field? The orbit would probably decay?

Kalster brings up another great question what about that?

From Wikipedia: Some satellites with long conductive tethers can also decay because of electromagnetic drag from the Earth's magnetic field. Basically, the wire cuts the magnetic field, and acts as a generator. The wire moves electrons from the near vacuum on one end to the near-vacuum on the other end. The orbital energy is converted to heat in the wire.

See also, Electrodynamic tether and Tether propulsion. If you don't trust Wikipedia, try the references in those links.

Thank you very much, I find this subject quite fascinating.

[quote="sunshinewarrio"]

Originally Posted by Shaderwolf

The earth's orbital radius is actually increasing. Every few years, to account for this, we have to add an extra second on to the length of our year.

This is wrong. At present, the Earth's mean orbital radius is decreasing at a rate of 0.00000005 AU per century. At which rate, you lose a second from the year every 42 years.
The leap seconds that we add every few years are due to the fact that the moon has slowed the Earth's rotation by about 2 milliseconds per day since 1820, when the length of the modern day second was established. Every few years this 2 milliseconds per day accumulate to the point where our clocks and the Earth have drifted 1 sec apart. A leap second is then added to bring them back into sync.

Many millions of years from now we would expect the Earth's orbit to be a lot larger, and possibly that, due to tidal effects, the earth always shows the same side/face to the Sun. This will, of course, take some time, and we have the counteracting effect of the moon to assist in our continuing rotation.

In a million years, at the present rate, the Earth's orbit will have decreased in size by 7.5 million kilometers, which is only a little bit more than it already varies in distance between perhelion and aphelion.

Originally Posted by Janus

Originally Posted by sunshinewarrio

The earth's orbital radius is actually increasing. Every few years, to account for this, we have to add an extra second on to the length of our year.

This is wrong. At present, the Earth's mean orbital radius is decreasing at a rate of 0.00000005 AU per century. At which rate, you lose a second from the year every 42 years.

Another opinion, from Ask a Scientist:

name C. Gerald
status educator
age 40s

Question - As our solar system evolves, and the earth revolves, what
is the current scientific thinking on the future of each? Most
importantly, is the earth "moving" closer to or further from the sun?
----------------------------------------
C. Gerald,
The earth is not doing either one. The earth is in an elliptical orbit with
the sun at one focus. The earth will remain in this orbit until something
extreme happens. It is true that the presence of other planets can cause
slight variations, but nothing significant. So long as nothing the size of
a moon or small planet strikes the earth, nothing important will happen.
The earth's orbit is stable.

The great astronomical catastrophe that is most likely to destroy the
earth's orbit will come from the sun. The sun will eventually become a "red
giant", expanding far beyond the orbit of the earth. After this, I do not
expect the earth will exist anymore.

One interesting site that talks about planetary creation and evolution is
posted by NASA:
http://www.jpl.nasa.gov/stars_galaxi...m_origins.html

Dr. Ken Mellendorf
Physics Instructor
Illinois Central College

So what is actually happening? Should we have a poll to decide if the Earth's orbit is shrinking, getting bigger or staying the same?

Originally Posted by Bunbury

The great astronomical catastrophe that is most likely to destroy the
earth's orbit will come from the sun. The sun will eventually become a "red
giant", expanding far beyond the orbit of the earth. After this, I do not
expect the earth will exist anymore.



Dr. Ken Mellendorf
Physics Instructor
Illinois Central College

So what is actually happening? Should we have a poll to decide if the Earth's orbit is shrinking, getting bigger or staying the same?

It's doing both and neither. Dr. Mellendorf is correct that, in the long term, the Earth's orbit is stable, which is why I said at present.

Right now, the Earth's orbit is shrinking, However, if you consider the whole time period from 1800 AD to 2050, then during that period, the Earth's orbit, on average, grows. For the period 3000 BC- 3000AD, it shrinks at an average rate.

One point however about the Sun engulfing the Earth. I remember hearing that newer models of the Sun's stellar evolution predict that the Sun in its red giant stage won't swell out to as far as the Earth's orbit.

Originally Posted by Janus

One point however about the Sun engulfing the Earth. I remember hearing that newer models of the Sun's stellar evolution predict that the Sun in its red giant stage won't swell out to as far as the Earth's orbit.

Side question. If the sun does expand as it loses mass, wouldn't the gravitational pull of the sun also decrease and allow the earth and other planets to slowly move away from it ?

I guess that the sun would grow larger much quicker than it would lose mass. The earth will still orbit the sun at more or less the same distance with the sun in red giant mode.

That makes sense. Thank you.

Originally Posted by KALSTER

I guess that the sun would grow larger much quicker than it would lose mass. The earth will still orbit the sun at more or less the same distance with the sun in red giant mode.

Ah, but the size doesn't matter much, only the total mass. He has a point. It may be that other factors impact our separation more rapidly, however.

What I'm getting out of this discussion is: Exact speeds never happen. Any planet will always be traveling at least slightly above, or slightly below, the idea orbital speed.

To randomly land on the exactly perfect speed would be quite exceptional.

Yes that is what I'm saying. The earth would still be attracted towards the centre of the mass, no matter how big it is. The earth's present orbit is more or less the same as the swirl that became the earth later on? How big a difference did the large mass that crashed into the earth and created the moon make to our orbit?