My boyfriend's roommate has a theory that the planets are moving closer to the sun and eventually Earth will become inhabitable and Mars will form life once it moves closer to the sun. Is this possible or no?

Does he have a reason for this? It could happen if the Sun's gravitational field strength was increasing, or if the planets' orbital velocities diminished (due friction provided by an interplanetary medium, for example).

In fact the Sun's gravitational field strength ought to be decreasing as the star very gradually loses mass. The very rarefied interplanetary/interstellar medium provides no significant resistance to planetary motion. I don't see how your boyfriend's roommate's theory could work.

At present, the Earth is moving in towards the sun at about .00000005 AU per century.
Mars is moving in at .00007221 AU per century. Saturn, Neptune and Pluto are also moving in.
Mercury, Venus, Jupiter, Uranus are moving out away.

The eccentricities of the planets are also changing with time, some decreasing and some increasing, though the change in semimajor axis and eccentricity do not follow any connected pattern. (some planets that are moving in are decreasing eccentricity, while others are increasing)

All these changes are due to Secular perturbations and do not remain constant. For instance, the Earth's eccentricity is decreasing at this time, but in 24,000 years it will start to increase again. In this time the average distance to the sun will only decrease by some 1800 km; very little when compare to the Earth's diameter (12000 km) not to mention the 4 million km the Planet moves in and out from the sun over the course of a year.

So, I can assume by what you are saying, the sun will swallow the earth during it's red giant phase, 4 to 5 billion years from now, before the earth's minute degrading orbit will resolve into the outcome of the original question.

Thanks everyone. Faulty, I don't know his reasoning behind it. If you really want to know, I'd be happy to ask him and post it.

What he might be thinking of is that the sun will eventually become a red giant and expand itself enough for the earth to fall in it. But in tis case itwould be the sun expanding wheter then the earth gradually falling in... :p

But by the time the sun expands to red giant, it will have lost enough mass to decrease its gravity (we are talking about a few Billion years here), thus the Earth (and the other planets) would be orbiting slightly farther out. Still close enough to be crispy, but not swallowed.

Let us know when that happens so we leave that day "blank" on our calendars.....O.K.?

>> a theory that the planets are moving closer to the sun

Sorry other way around, the planets are moving away from the Sun, the moons are moving away from the planets.

Venus will be the next Earth, Mars' fate is set for destructive break up once its core is totally frozen.

Wasn't it that the moon gradually slows down the rotation of the earth and in turn the moon will move closer to us? This should also be the case with the planets slowing down the rotation of the sun, however the sun loses mass by radiation and there are the pertuberations and framedragging gravity effects, wich would all account for all sort of pro and con factors that would make our planets back and forth in time.

But anyway, we will not go all the way to the sun, but a red sun will rather come to us, by that time we might have subtropical holiday resorts on mars and jupiters moons!

@ Silverback: yes, the Sun could lose up to half its mass during and after its red giant phase. Earth, though long ago sterilized and melted, will probably end up at an orbital radius similar to that of Mars today.

@ Zarkov:If the Moon's tidal effect eventually slows Earth's rotation to the point of synchrony, where the Moon remains fixed over one side of the Earth like a communications satellite, then obviously the Lunar tidal process will freeze. However, the weaker Solar tides would still continue to slow the Earth's rotation - angular momentum will then be transferred to the Earth's orbit around the Sun, and Earth will begin to spiral outwards. (This would all be long after the Sun's red giant phase ended).

What do you mean about planets breaking up once their cores freeze? I'm not familiar with that theory.

Re. the original subject of this thread: in the REALLY distant cosmological future, planetary orbits will theoretically collapse due to gravitational radiation, which leaks away kinetic energy - on the order of 10^20 years. [See the thread on "Does a Body that radiates gravity lose mass?"]

Before that, though, random encounters between the dead stars will have stripped most planets away from their suns.

But by the time the sun expands to red giant, it will have lost enough mass to decrease its gravity (we are talking about a few Billion years here), thus the Earth (and the other planets) would be orbiting slightly farther out. Still close enough to be crispy, but not swallowed.
What are you talking about when you say decreasing gravity? Most of the mass of a read giant is concentrated in the core, where all the CNO is. This core would have a density of 10⁶g/cm³, compared to the present stage which is 150g/cm³! After the Helium flash and after the sun becoming an RR Lyra, the outer envelope will pulsate at least twice a day and will slowly throw away its outer envelope into space creating a planetary nebula. Still, that will be only a small percentage of the mass compared with the core which is way massive then the rest of the star.

In other words... how come will the gravity decrease if we will have a white dwarf in the place of the sun?

Also, just as a comparison, Betelgeuse has a radius 150 times bigger then the sun. The distance from the sun to earth is about 150,000,000km and its diameter is about 1,309,000km. If the sun becomes like Betelgeuse and expand to a size of 150 times the present size, the earth would be just inside the sun, since the diameter of the sun would be bigger then the distance from the sun to earth. The diameter would be at least 150,000,000km, exactly the distance between them. Of course, this is just a comparison, since the sun has a mass of 1M_o and Betelgeuse has a mass of 15M_o, but you still can expect the sun to be way bigger then it is right now... :D

But anyway, we will not go all the way to the sun, but a red sun will rather come to us, by that time we might have subtropical holiday resorts on mars and jupiters moons!
Huuhh... RR Lyrae can be beautiful, but I have the slight impression that we will need suntain lotion... particularly when the sun star shooting out its outer envelope in our direction... :D :D :D

>> to slow the Earth's rotation - angular momentum will then be transferred to the Earth's orbit around the Sun, and Earth will begin to spiral outwards.

sorry to pursue the wrong subject but Starthane Xyzth, not sure that the above is logically correct.
Certainly the larger the orbit the slower the tangential velocity of a planet and this is a constant relation rv^2, so loss of kinetic energy would actually cause the planet to spiral into the Sun, ( a satellite slowed by the atmosphere is lost to the Earth)

SO there is no gain or loss of kinetic energy, but the distance defines the change in the velocity, so there is a gain of electrical energy in every orbit (= time), caused by electric charge separation, IMO

>> Re. the original subject of this thread: in the REALLY distant cosmological future, planetary orbits will theoretically collapse due to gravitational radiation, which leaks away kinetic energy - on the order of 10^20 years. [See the thread on "Does a Body that radiates gravity lose mass?"]

Thanks, these thoughts are intimately intertwined, eg does a magnet lose weight?
In Electrodynamic spin gravity theory, gravity is the resultant induced by non inertial acceleration of a body in a crossed centric electric-magnetic field. Magnetic fields will cause contraction of distances between objects, while polarised electric fields will cause an expansion of distances. The characteristics of equilibrium are in what we see.

BUT separated electric fields shield each other and remix with each other (leak) so once the source of charge separation is removed all matter will contract to each other.

So as long as the Sun has the appropriate output then all solar objects will move away from each other but eventually magnetism will win, once the Sun has ceased sufficient output to maintain an outward pressure on the solar object, the solar bodies will all eventually join the Sun again.

Re the core solidification.. well 'magnetic-electric tidal forces' if present break up the mantle and the core will be set on a different parth. From my calculations the planet expands in size until the value of the surface geomagnetic force is within a narrow range.

my understanding :)

Zarkov,
Do you claim that the orbital radius of all planets is currently and always increasing?
Do you claim that the orbital radius of all moons is currently and always increasing?

>> Do you claim that the orbital radius of all planets is currently and always increasing?

The observed averaged orbital tangential velocities of solar bodies is at or above the theoretical orbital velocities for these bodies. The Moon is measured to be receeding from the Earth. For most of the moons of other planets, they are theoretically receeding.
The solar planets show little discrepency, but I expect they would receed rather slowly.
my analysis


>> Do you claim that the orbital radius of all moons is currently and always increasing?

see above, EXCEPT the moons of Mars and maybe one of Jupiter. They show a depressed tangential velocity. This could be due to electric shielding.

I postulate that the positive outer electric charge of all electrically isolated bodies is increased by the Solar output. Of course this implies that the planetary system is born from the Sun (or planets) and they spiral out until the source of charge separation is extinguished and then the bodies spiral inwards towards the Sun.

Just my model :)

arent the planets mars and venus creeping back close to where we are currently?
traffic jam. also couldnt the earth be attracted towards the sun if an object with gravitational mass came into the solar system in the direction of the sun.

i think he is onto something but might have some facts twisted. or maybe i do heh

>> Do you claim that the orbital radius of all planets is currently and always increasing?

The observed averaged orbital tangential velocities of solar bodies is at or above the theoretical orbital velocities for these bodies. The Moon is measured to be receeding from the Earth.
This is due to tidal interaction between the Earth and Moon. As the lunar tidal bulge slows the Earth's rotation, the Earth transfers angular momentum to the moon, lifting it to a higher orbit.



For most of the moons of other planets, they are theoretically receeding.
The solar planets show little discrepency, but I expect they would receed rather slowly.
my analysis


>> Do you claim that the orbital radius of all moons is currently and always increasing?

see above, EXCEPT the moons of Mars and maybe one of Jupiter. They show a depressed tangential velocity. This could be due to electric shielding.

Quite a few Jovian moons are decreasing orbital distance, Metis, Adrastra, and all of the recently found moons that orbit in retrograde.

Most of Uranian moons orbit in retrograde to Uranus' rotation, so they also are approaching.

Five of Neptune's moons are approaching, because, while they orbit directly, they have orbital periods smaller that Neptune's rotational period.

These are all due to tidal interaction between the Planet and moon. If a moon either orbits retrograde to the planet's rotation, or orbits directly faster than the planet rotates it will move in towards the planet.

@

@ Zarkov:If the Moon's tidal effect eventually slows Earth's rotation to the point of synchrony, where the Moon remains fixed over one side of the Earth like a communications satellite, then obviously the Lunar tidal process will freeze. However, the weaker Solar tides would still continue to slow the Earth's rotation - angular momentum will then be transferred to the Earth's orbit around the Sun, and Earth will begin to spiral outwards. (This would all be long after the Sun's red giant phase ended).


Actually, the Lunar tidal process will not end there. As the Solar tide begins the slow the Earth's rotation, the moon will then start to orbit a little faster than the Earth. As this happens, the lunar tidal bulge will start to move again. But this time, instead of slowing the Earth, it will try to speed it up again to match the moon. It won't quite succeed due to the solar tidal drag, and the Earth's rotation will always lag a little behind the moon. Due to the resulting tidal interaction, the moon will spiral in towards the Earth until it reaches the Roche limit and breaks up.

>> to slow the Earth's rotation - angular momentum will then be transferred to the Earth's orbit around the Sun, and Earth will begin to spiral outwards.

sorry to pursue the wrong subject but Starthane Xyzth, not sure that the above is logically correct.
Certainly the larger the orbit the slower the tangential velocity of a planet and this is a constant relation rv^2, so loss of kinetic energy would actually cause the planet to spiral into the Sun, ( a satellite slowed by the atmosphere is lost to the Earth)

SO there is no gain or loss of kinetic energy...

Like Janus58, I was refering to a loss of angular momentum from the Earth's rotation: I guess that to call it "kinetic energy" is inaccurate. Sorry. The Earth can't lose angular momentum without it being gained somewhere else in the Earth-Moon-Sun system; if it is transfered to the orbital motion, then Earth's distance from the Sun will increase, via rv^2 as you said.

Oh - and do you have a link to your Electrodynamic spin gravity theory, Zarkov?

@Janus58: are you saying that ALL satellites with a retrograde orbit are slowly approaching their primaries? (That would also include Phoebe, the outermost satellite of Saturn). If the reason is the motion of the tidal bulges those satellites cause on the said primaries, it must be infinitesimally small with most of them: I don't think Adrastea or Metis, for example, can generate any appreciable tides in the liquid mantle of Jupiter!

The contrast in heating between the day and night sides of a planet would have more effect on its rotation than the tidal effect of such minor satellites.

Oh - and do you have a link to your Electrodynamic spin gravity theory, Zarkov?

@Janus58: are you saying that ALL satellites with a retrograde orbit are slowly approaching their primaries? (That would also include Phoebe, the outermost satellite of Saturn). If the reason is the motion of the tidal bulges those satellites cause on the said primaries, it must be infinitesimally small with most of them: I don't think Adrastea or Metis, for example, can generate any appreciable tides in the liquid mantle of Jupiter!

The contrast in heating between the day and night sides of a planet would have more effect on its rotation than the tidal effect of such minor satellites.

But they still will have an effect, even if only very small. Off course, in complex systems like the those of Jupiter and Saturn, you are going to have all kinds of perturbations to account for, some of which will cause individual moons to move in or out regardless of what the tidal effect is trying to do.(Just look at the solar system; all the planets orbit directly and with longer periods than the sun's rotation, yet some are presently moving in and some are moving out.)

>> to slow the Earth's rotation - angular momentum will then be transferred to the Earth's orbit around the Sun, and Earth will begin to spiral outwards.

sorry to pursue the wrong subject but Starthane Xyzth, not sure that the above is logically correct.
Certainly the larger the orbit the slower the tangential velocity of a planet and this is a constant relation rv^2, so loss of kinetic energy would actually cause the planet to spiral into the Sun, ( a satellite slowed by the atmosphere is lost to the Earth)

SO there is no gain or loss of kinetic energy...


The Earth's kinetic energy lays in two forms, the KE due to its orbital velocity and the KE due to its rotatation around its axis.

The earth's total orbital energy is equal to its KE due to orbital velocity plus its gravitational potential energy(GPE) this is expressed in by the formula

E = mv^2/2 - GMm/r

(GPE is negative, so we have the minus symbol)

Since v (the orbital velocity) can be found by

v = sqrt(GM/r)

Through substitution we can get

E = -GMm/2r

As the Earth slows its rotation, it loses kinetic energy, but its total energy stays the same, so this energy is converted to orbital energy.

thus -GMm/2r must get larger, and the only value that can change is r. In order for the orbital energy to get larger, r must get larger (Thus driving the Orbital energy less negative.)

As a result, the Earth moves into a higher orbit, Since higher orbits also have lower orbital speeds, the Earth also loses kinetic energy in this form.

Even though the Earth loses kinetic energy, the gain in GPE caused by moving away from the sun offsets this.

My boyfriend's roommate has a theory that the planets are moving closer to the sun and eventually Earth will become inhabitable and Mars will form life once it moves closer to the sun. Is this possible or no?

There is a giant misunderstand in the general population's understand of Mars and its nature. Mars indeed shares many features of Earth and may, at one time, had microsopic forms of life. However today, even if it was in the same solar position as us, it could not.

Mars has only 10% of the mass of the earth and proptionally less gravity, thus larger organisms would have a fundemental problem of staying on the planets surface. However, even if life did manage to stay on its surface through evolution, they would be able to survive the very bitter cold that would be on Mars at night and especially during its 6 months of winter. You see, because of the lack of mass, and thus gravity, mars has very little atmosphere compared to earth. Thus, heat cannot stay trapped as much or as long as it can on earth.

This is one theroized reason to why the water that may have been on mars at on point is now all ice at its polls. Overtime, as more and more atmosphere escaped into space, the planet grew colder, and colder, until it is what it is today.

Earth itself is also loseing its atmosphere. Notice that there is no hydrogen or helium in our atmosphere. It is not because it somehow changed forms and is now on the planet's surface. Over the billions of years of the earths existence, hydrogen and helium slowly escaped from our atmosphere, leaving the heavier elements in its place, i.e., carbon dioxide, nitrogen, etc.

Jupiter, due to its large mass, still has much of the same gas that was around even at its creation!

To be honest, Mars is more like a over sized moon than an actual planet. So to answer your question, no, even if mars was where we were, life would not exist (or to be more accurate, over time, as mars lost more and more of its atmosphere, life would cease to exist).

There is a giant misunderstand in the general population's understand of Mars and its nature. Mars indeed shares many features of Earth and may, at one time, had microsopic forms of life. However today, even if it was in the same solar position as us, it could not.

Mars has only 10% of the mass of the earth and proptionally less gravity, thus larger organisms would have a fundemental problem of staying on the planets surface. However, even if life did manage to stay on its surface through evolution, they would be able to survive the very bitter cold that would be on Mars at night and especially during its 6 months of winter. You see, because of the lack of mass, and thus gravity, mars has very little atmosphere compared to earth. Thus, heat cannot stay trapped as much or as long as it can on earth.

This is one theroized reason to why the water that may have been on mars at on point is now all ice at its polls. Overtime, as more and more atmosphere escaped into space, the planet grew colder, and colder, until it is what it is today.

Earth itself is also loseing its atmosphere. Notice that there is no hydrogen or helium in our atmosphere. It is not because it somehow changed forms and is now on the planet's surface. Over the billions of years of the earths existence, hydrogen and helium slowly escaped from our atmosphere, leaving the heavier elements in its place, i.e., carbon dioxide, nitrogen, etc.

Jupiter, due to its large mass, still has much of the same gas that was around even at its creation!

To be honest, Mars is more like a over sized moon than an actual planet. So to answer your question, no, even if mars was where we were, life would not exist (or to be more accurate, over time, as mars lost more and more of its atmosphere, life would cease to exist).
Good points, but a bump. I disagree with Mars being more like a moon than a planet though. A very intelligent post overall though, WELCOM TO SCIFOUMS!

As the sun expands it will engulf the planets eventually exploding into a supernova.

Hi emusquire, and welcome to the forums.
As the sun expands it will engulf the planets eventually exploding into a supernova.
Are you sure about that? You'll find that at sciforums, it pays to check your facts before posting.

I believe that should be when the sun switches over to helium burning and expands to a red giant. Most texts suggest it will engulf everthing out to the asteroid belt.

It varies, that distance. SOme say it won't even reach Earth, perhaps Venus and definitely Mercury but not Earth

I heard that if the sun would become a red giant right now then the earth would be swallopt,
but because the sun is losing mass by solar radiation and later on will expell it's outer layer's. It will loose a considerbly enofpart of it's mass. So the earth would move in a bigger orbit.

So, I can assume by what you are saying, the sun will swallow the earth during it's red giant phase, 4 to 5 billion years from now, before the earth's minute degrading orbit will resolve into the outcome of the original question.


It is pretty possible that might not even happen, the earth might not actually be engulfed by the sun. Although all this is just speculation, there is no hard evidence to support which one of the two will happen. On a personal note I believe we will end up in the sun. As its already mentioned in the Qu'ran.

As the moon goes around earth so the earth goes around the sun. so according to the great law of physics what happens with one does happen with the other too.

which implies

slowing of moons rotation will tke it away from earth and slowing of earths rotation will take it away from sun.

the earths rotation is slowing since we add o.1 sec extra every 2-3 years at the new year to keep our atomic clocks correct (I can also prove it mathematically if someone needs). so it is moving away from Sun and thus if it is moving away from sun it will never fall into it. similarly other planets are also moving away from sun.

One last thing all this has completely nothing to do anything with electricity or magnetism.

I'm sure I posted this link recently; in any case, here it is again.
http://www.astronomy.ohio-state.edu/~pogge/Lectures/vistas97.html

The Sun constantly loses mass because of the solar wind and other effects; gradually the Earth and other planets will move outward.
The remaining planets move further outward in response to the reduced central mass of the Sun:
Venus at 1.22 AU
Earth at 1.69 AU
This is just enough to keep them from being engulfed by the swelling Sun.

As the moon goes around earth so the earth goes around the sun. so according to the great law of physics what happens with one does happen with the other too.

which implies

slowing of moons rotation will tke it away from earth and slowing of earths rotation will take it away from sun.

It is actually the slowing of Earth's rotation that is causing the Moon to move away from the Earth. Due to tidal interaction, the Earth is transfering angular momentum to the Moon.

the earths rotation is slowing since we add o.1 sec extra every 2-3 years at the new year to keep our atomic clocks correct (I can also prove it mathematically if someone needs).
Just to clarify, the leap second we add every couple of years does not mean that Earth's rotation slows by that much over that period. IOW just because we added a leap second in 1987 and then another in 1989 does not mean that the Earth took 1 sec longer to complete a rotation in 1989 than it did in 1987. The leap second is to compensate for the fact that the standard length of a sec was established as 1/86400 of a solar day back in the 1800's. Since then, the length of the Solar day has increased by about 2 milliseconds. This 2 ms per day accumulates until it equals a difference of 1 sec. Then we add a leap second to keep standard time in sync with the Solar day. Also, since the rate of rotation for the Earth varies due to a number of factors, the addition of leap seconds are not on a fixed schedule. For instance, we had leap seconds added in 1992,1993 and 1994, but the last leap second added was in 2005.
Just to be clear, I am not accusing you of making this error, I'm just clarifying so that other don't jump to the wrong conclusion.


so it is moving away from Sun and thus if it is moving away from sun it will never fall into it. similarly other planets are also moving away from sun.

Many factors effect whether a palanet is moving in towards or away from the Sun during any given time period. For instance, for the present epoch, Jupiter, Saturn and Pluto are decreasing their average distance form the Sun, And while during the period of 1800 AD - 2050 AD, the Earth's average distance from the Sun is increases by 0.00000562 AU/century, during the period of 3000 BC - 3000 AD, the Earth's average distance [i]decreases[i/] by -0.00000003 AU/century.

One last thing all this has completely nothing to do anything with electricity or magnetism.

Agreed.

Measuring the distance is difficult. A well known fact, sure to be talked down, is average orbit distance, from assumed timing.

Our course is not constant. No 2d. The Sun's main influence is bodies nearly as large, or larger, and things like neutron stars. It really does vary a great deal.

I have recently learnt something which indicates that I was probably wrong in earlier posts on this subject- the Earth, and all the planets out to Jupiter, will probably spiral into the Sun at a late stage in its evolution.

The Sun in fact turns into a red giant at two separate points in its life history; the second time it ends up on the Asymptotic Giant Branch, and will probably put out so much material in its solar wind that the planets will be braked by friction, quite quickly falling into the star.

The tides are the primary mechanism by which transfer the Moon and Earth transfer rotational angular momentum to orbital angular momentum. The same happens with the Sun and Earth but to a much lesser extent. Just as the Sun raises tides on the Earth, so does the Earth raise tides on the Sun.

The Sun currently rotates faster than the Earth orbits the Sun. This will not always be the case. The solar wind takes angular momentum from the Sun, and does so faster than it takes mass from the Sun. This angular momentum loss will be compounded when the sun expands into a red giant. By that time, the sun will be rotating slower than the earth's orbital rate. The Sun-Earth system will transfer angular from the Earth's orbit to the Sun. The Earth will spiral into the Sun a long, long time from now. Note that this will not be a great feat because the Sun will be a lot bigger than it is a long, long time from now.

Another factor in the late evolution of the Sun will help the decay of the Earth's orbit. When the Sun expands into a red giant the Earth will orbit through the Sun's upper atmosphere. Just as satellites in low Earth orbit decay due to atmospheric drag (e.g., that satellite that was just "shot down"), so will the Earth's orbit decay as the heliosphere becomes denser.

A paper that examines these factors was recently accepted for publication in the Monthly Notices of the Royal Astronomical Society. The paper was recently posted at arXiv; link here (http://arxiv.org/abs/0801.4031).