Planetary orbit shifts?

[Vanamonde]

The idea of a planet's orbit shifting always seemed like bad science fiction to me but I've been seeing in some science vids that it's believed to have happened in earth's climatic history. Can someone explain to where the momentum goes? If it's due to earth interacting with other planets, why does it seem to have been discrete events rather than an on-going affect? 

[18Watt]

Tidal forces and precession are two means that I'm aware of for an orbit to shift.  Earth-Moon and Phobos-Mars are two systems that exhibit shifting due to tidal forces.  Mercury's precession of it't orbit around the Sun has also been well documented.

Oh, as for where the energy goes:  In the case of Earth-Moon, the Moon is actually stealing rotational energy from Earth.  So the Moon is gaining energy, which gradually puts it in a higher orbit.  You would think that the rotational energy lost to the Moon would slow down Earth's rotation.  Which is exactly what is happening.

In the case of Phobos-Mars, I think the energy is going the other direction.  I think that's a tidal interaction also, but the orbital energy of Phobos is slowly being transferred to Mars.  Phobos doesn't weigh much, so Mars probably doesn't notice it, but eventually Phobos' orbit will get closer to Mars.

For an explanation of orbital precession, somebody smarter than me will have to reply.  I think it involves microwave ovens and non-dairy coffee creamer, two things which have never been understood by mankind.

[PakledHostage]

The only way that makes sense to me is to use gravitational interactions from a 3rd celestial body. I've seen "future tech" proposals to use oort cloud objects carefully sent earthward to slingshot past the Earth and increase its orbital distance from the Sun. Over the course of millions of years, we may be able to move the Earth enough to save it from being baked by the Sun.

But presumably orbital perturbations could also happen naturally due to the passing of something large. The star Gliese 710, for example, will pass through our outer oort cloud in about 1.3 million years. If it carries its own oort cloud, it stands to reason that some of the bodies in that oort cloud will pass through our inner solar system. A close encounter with a large object like that could bump an orbit slightly, as could the passing star itself if it is massive enough (Gliese710 is not).

That being said, I find it hard to believe that these types of orbital changes would really be that noticeable. Our own orbital distance from the Sun varies by millions of kilometers over the year, with our closest approach happening in early January (i.e. northern hemisphere winter), and yet it's still winter on a good deal of the planet when that happens each year.

[Superfluous J]

4 hours ago, Vanamonde said:

Can someone explain to where the momentum goes? If it's due to earth interacting with other planets, why does it seem to have been discrete events rather than an on-going affect?

The only way I can see this happening would be an interstellar interloper flying by once, close enough, slow enough, and large enough to have a one-time effect on Earth's orbit/rotation/tilt/etc.

[magnemoe]

4 hours ago, Vanamonde said:

The idea of a planet's orbit shifting always seemed like bad science fiction to me but I've been seeing in some science vids that it's believed to have happened in earth's climatic history. Can someone explain to where the momentum goes? If it's due to earth interacting with other planets, why does it seem to have been discrete events rather than an on-going affect? 

There is some effects like orbits tend to become more circular and you have stuff like moon slowing down earth rotation, both is because of tides. 
Going back 4 billion years stuff was a weirder.

Some theories even Jupiter and Saturn moved around quite a bit, I say this is mostly scientists trying to explain the solar system from limited data and models.  

[kerbiloid]

A passing-by chunk of Dark Matter ^(tm), if it exists.

Actually, if it exists, I barely can understand, how the planets at all can have orbits.

[PakledHostage]

15 hours ago, Superfluous J said:

The only way I can see this happening would be an interstellar interloper flying by once, close enough, slow enough, and large enough to have a one-time effect on Earth's orbit/rotation/tilt/etc.

The Nice model of the solar system's early evolution includes major changes in Uranus and Neptune's orbits, but this involved the two planets interacting with millions of other bodies and exchanging energy with those. In the process, they also "cleaned up" the early solar system and swapped positions.

[kerbiloid]

Also, somebody could change the Kopernicus cfg files.

[K^2]

On 12/27/2023 at 1:20 PM, Vanamonde said:

If it's due to earth interacting with other planets, why does it seem to have been discrete events rather than an on-going affect? 

"Discrete" on the timescale of the age of the Solar System. These are still very slow migrations from one stable location to another.

Take two massive planets around a star and consider their mean interaction in the constant of motion coordinates for the central potential. When the planets are far out of resonance, the energy and momentum flow between the two are very slow. The orbits will drift, but very, very slowly. As the two approach the resonance, the transfer rate becomes much higher, with some sort of an equilibrium at the exact resonance. For just two planets, all that really means is that they'll drift slowly and then almost "snap" to resonant orbits like a pair of magnets when they get close to resonance. Again, on the "age of the star system" kind of time scale. 

As you start adding more objects to the system, interactions get more complex. There aren't just drifts, but also precessions. Several planets might be happily spinning in their own planes for ages and ages as the planes of their individual orbit slowly precess, until the two planes align, and suddenly, these two planets are strongly interacting with each other or with some 3rd body, causing their orbits to start changing rather rapidly on the cosmic scale.

Point is, there are a lot of quaistable arrangements that become unstable once some of the parameters of the system happen to align in a certain way, then they become highly unstable, and start shifting until a new quasistable arrangement is achieved. Truly dynamically stable systems are exceptionally rare. There's currently only one system I'm aware of (HD 110067) that is suspected to have all of its known planets nearly co-planar and in simple resonances with each other, therefore, being exceptionally stable. Pretty much everything else we've found has some combo-breakers in the system that are orbiting  out of the main plane, with high eccentricity, or way out of resonance, meaning they'll throw a wrench into the stability at some point in the future. Solar System is unusually messy, based on what we've seen so far in other star systems, but not incredibly so. The current arrangement is stable enough, and there is no expectation of drastic shifts for the near future, but in the system's past, we've had a lot of rearrangements that would come in bursts of activity for the aforementioned reasons.

[Errol]

Here's a paper proposing to use a large asteroid on an elliptical orbit as a sort of "orbital energy siphon" utilizing slingshots at both ends to transfer momentum from one planet to another.

ASTRONOMICAL ENGINEERING: A STRATEGY FOR MODIFYING PLANETARY ORBITS

Edited January 6 by Errol

[JoeSchmuckatelli]

On 12/27/2023 at 4:20 PM, Vanamonde said:

The idea of a planet's orbit shifting always seemed like bad science fiction to me but I've been seeing in some science vids that it's believed to have happened in earth's climatic history. Can someone explain to where the momentum goes? If it's due to earth interacting with other planets, why does it seem to have been discrete events rather than an on-going affect? 

There are some articles out there about Jupiter and Saturn having wandered a bit during the very early formation of the system.   Grand tack hypothesis - Wikipedia

They're also the two planets responsible for changing the eccentricity of our orbit (Milankovitch cycles).  Milankovitch (Orbital) Cycles and Their Role in Earth's Climate – Climate Change: Vital Signs of the Planet (nasa.gov)

 

Planetary migration[edit]

Main articles: Nice model and Grand tack hypothesis

According to the nebular hypothesis, the outer two planets may be in the "wrong place". Uranus and Neptune (known as the "ice giants") exist in a region where the reduced density of the solar nebula and longer orbital times render their formation there highly implausible.^[66] The two are instead thought to have formed in orbits near Jupiter and Saturn (known as the "gas giants"), where more material was available, and to have migrated outward to their current positions over hundreds of millions of years

According to the Nice model, after the formation of the Solar System, the orbits of all the giant planets continued to change slowly, influenced by their interaction with the large number of remaining planetesimals. After 500–600 million years (about 4 billion years ago) Jupiter and Saturn fell into a 2:1 resonance: Saturn orbited the Sun once for every two Jupiter orbits.^[46] This resonance created a gravitational push against the outer planets, possibly causing Neptune to surge past Uranus and plough into the ancient Kuiper belt.^[68] The planets scattered the majority of the small icy bodies inwards, while themselves moving outwards. These planetesimals then scattered off the next planet they encountered in a similar manner, moving the planets' orbits outwards while they moved inwards.^[46] This process continued until the planetesimals interacted with Jupiter, whose immense gravity sent them into highly elliptical orbits or even ejected them outright from the Solar System. This caused Jupiter to move slightly inward.^[c] Those objects scattered by Jupiter into highly elliptical orbits formed the Oort cloud;^[46] those objects scattered to a lesser degree by the migrating Neptune formed the current Kuiper belt and scattered disc.^[46] This scenario explains the Kuiper belt's and scattered disc's present low mass. Some of the scattered objects, including Pluto, became gravitationally tied to Neptune's orbit, forcing them into mean-motion resonances.^[69] Eventually, friction within the planetesimal disc made the orbits of Uranus and Neptune near-circular again

Another question is why Mars came out so small compared with Earth. A study by Southwest Research Institute, San Antonio, Texas, published June 6, 2011 (called the Grand tack hypothesis), proposes that Jupiter had migrated inward to 1.5 AU. After Saturn formed, migrated inward, and established the 2:3 mean motion resonance with Jupiter, the study assumes that both planets migrated back to their present positions. Jupiter thus would have consumed much of the material that would have created a bigger Mars. The same simulations also reproduce the characteristics of the modern asteroid belt, with dry asteroids and water-rich objects similar to comets.^[71][72] However, it is unclear whether conditions in the solar nebula would have allowed Jupiter and Saturn to move back to their current positions, and according to current estimates this possibility appears unlikely.^[73] Moreover, alternative explanations for the small mass of Mars exist

Formation and evolution of the Solar System - Wikipedia

[magnemoe]

Comets are another thing, they are pretty unpredictable, we can not predict Halley's comet or other like it more than a few orbits into the future. 
The issue here is that tiny changes has huge effects on Ap, and tiny changes to Ap affect period and then the day its reach Pe who changes how planets interact with it who affect Ap. 

[kerbiloid]

The comets are chaotic evil.

They see, what happened to the lawful good DidymosDimorphos, and are performing evasive action.

A natural shelter for a space-based megalomaniacal scientist.

[sevenperforce]

On 12/28/2023 at 8:49 PM, K^2 said:

As you start adding more objects to the system, interactions get more complex. There aren't just drifts, but also precessions. Several planets might be happily spinning in their own planes for ages and ages as the planes of their individual orbit slowly precess, until the two planes align, and suddenly, these two planets are strongly interacting with each other or with some 3rd body, causing their orbits to start changing rather rapidly on the cosmic scale.

Point is, there are a lot of quaistable arrangements that become unstable once some of the parameters of the system happen to align in a certain way, then they become highly unstable, and start shifting until a new quasistable arrangement is achieved. Truly dynamically stable systems are exceptionally rare.

I saw the original post, started typing a reply, scrolled up a bit, and then saw you had said this, which was 95% of what I was going to say.

On 1/7/2024 at 8:29 AM, JoeSchmuckatelli said:

There are some articles out there about Jupiter and Saturn having wandered a bit during the very early formation of the system.   Grand tack hypothesis - Wikipedia

They're also the two planets responsible for changing the eccentricity of our orbit (Milankovitch cycles).  Milankovitch (Orbital) Cycles and Their Role in Earth's Climate – Climate Change: Vital Signs of the Planet (nasa.gov)

Milankovitch cycles are particularly interesting (for me) because they leave directly observable traces on Earth's surface...some of which are even visible with the naked eye.

The full Milankovitch cycle is the fusion of periodic changes in axial tilt, orbital eccentricity, perihelion, and precession rate. Of these, eccentricity has the largest forcing function on global temperature, and it operates on a roughly-100,000-year cycle created primarily by Jupiter. I believe that the amplitude of the changes are forced primarily by Saturn, though I'm not sure. The function looks like this (going back and extrapolated forward by just under a million years):

Whenever eccentricity reaches a maximum, the increase in solar insolation at perihelion reaches a maximum, and so global temperature starts to rise. This increase in temperature releases carbon dioxide stored by the oceans, which further drives up global temperature in a rapid spike. As glaciers melt and ocean levels rise, the dissolved gas carrying capacity of the ocean increases, allowing the oceans to slowly scrub the atmosphere of excess CO₂, allowing global temperature to gradually trickle back down until the next peak in eccentricity. These temperature cycles are recorded on Earth in a number of ways, both organic and inorganic. Foraminifera, or forams, are single-celled organisms with calcium carbonate shells, and since calcium carbonate (CaCO₃) contains oxygen atoms, foram shells trapped in benthic seafloor sediment create a record of the isotopic concentration of oxygen in the atmosphere at the time. Because ¹⁸O evaporates more readily at higher temperatures, higher ocean temperatures lead to a higher ¹⁸O/¹⁶O ratio in the atmosphere. Thus, benthic forams record global temperature. Similarly, air bubbles trapped in ice cores also preserve samples of the global atmosphere. Sure enough, both benthic forams and ancient ice cores reflect this sudden temperature spike and gradual decline on the exact same period as Earth's variation in eccentricity:

And it's not just these two records. Because global temperature impacts sedimentation rates, and sedimentation rates impact the density of sedimentary rock, we can literally see Milankovitch cycles recorded on the sides of cliffs in certain areas, where the rapidly-deposited sediment has weathered away faster than the slowly-deposited sediment:

Spoiler

I'm a fan of this because it's one of the bodies of evidence that helped me to leave the science-denial cult I grew up in.