How does Jupiter not pull earth way out of its orbit

[Northern_Piper]

@dtilque

That’s the Grand Tack, not Grand Attack.

One of the articles cited in the Wikipedia article uses both, because the Grand Tack may have destroyed nascent inner planets, hence a « Grand Attack ».

“This kind of theory, where first this happened and then that happened, is almost always wrong, so I was initially skeptical,” Laughlin said in a statement. However, “there is a lot of evidence that supports the idea of Jupiter’s inward and then outward migration. Our work looks at the consequences of that. Jupiter’s ‘Grand Tack’ may well have been a ‘Grand Attack’ on the original inner solar system.”

Jupiter's 'Smashing' Migration May Explain Our Oddball Solar System

[md-2000]

@Machine_Elf

Jupiter is moving along its orbital path, so the perturbation events don’t all happen at the same point in the earth’s orbit. By the time the earth has completed one orbit, Jupiter has advanced about thirty degrees along its orbital path. So now the next perturbation of Earth’s orbit will happen about thirty degrees later than where the one last year happened. Over much time and many orbits, these perturbations are fairly evenly distributed along Earth’s orbital path, and its orbit remains approximately round.

@Francis_Vaughan

Most of the effects cancel one another out. However, given enough time, yes indeed, it is possible for just the right confluence of effects to build up into something dramatic. The Earth could be ejected from orbit around the sun.

Remember orbital dynamics - the earth is basically “falling” around the sun. It has a certain velocity. If Jupiter is in coincidence, and pulls earth closer, then earth will speed up a little and fall closer to the sun after Jupiter is no longer as close. Since each of Jupiter’s little “tug” on earth happens at a different point on its orbit each time they are lined up, the high points cancel out.

If the orbits were in sync - the same place every year, or every 10 years - then yes, it would slowly pull the orbit of earth to make that a higher point each time. But since the point of closest approach is different each time, it doesn’t.

[Steve_MB]

@filmore

Even if the effect is minimal, why doesn’t it have a bigger effect after millions and billions of iterations? I could see how the effect would be infatismal from year to year, but after so many orbital cycles, it seems like those would all add up to major changes in our orbit. Is our orbit kind of like a “groove” to where minor forces aren’t enough to to pull us out of that groove?

In most cases, there isn’t much cumulative effect because one planet pulls on another from different directions at different times. If there’s an orbital resonance so that (for example) one planet goes around the sun twice in the same time another goes around once, there can be a cumulative effect because they planets line up in the same relative positions over and over. This tends to cause one or both of their orbits to shift until their orbital periods change enough to break the resonance or until one of them gets ejected into deep space or collides with something.

[Chronos]

@Jackknifed_Juggernaut

ETA: By the way, some parts of the theories are based on what we observe in other star/planet systems, where “hot Jupiters” and “super Earths” seem to be common, and where most planets’ orbits are much closer to their stars. We don’t have those, so the theories evidently explain that as well.

Be careful drawing conclusions from “hot Jupiters”, as there’s a huge selection effect there. Most of the exoplanets we discover are hot Jupiters, because those are the easiest planets to detect (in fact, for some methods, they’re the only planets we can detect). We don’t know how many systems there are out there like our own.

[dtilque]

@Steve_MB

If there’s an orbital resonance so that (for example) one planet goes around the sun twice in the same time another goes around once, there can be a cumulative effect because they planets line up in the same relative positions over and over. This tends to cause one or both of their orbits to shift until their orbital periods change enough to break the resonance or until one of them gets ejected into deep space or collides with something.

And there are gaps in the asteroid belt where no asteroid has certain a orbital period (or equivalently, semi-major axis) because of that effect. These are known as

Kirkwood gap

[Jackknifed_Juggernaut]

Thanks. Yes, I actually assumed that but I feel like I never hear this caveat from the science shows I watch. I always wonder if its just way easier to detect hot Jupiters and super Earths, considering they are using gravitation and light as the means of detecting planets. Maybe the scientists on the shows “dumb it down” for the audience, but this seems to be an important selection bias to point out.

[eburacum45]

@Andy_L

Note that the Milankovitch cycles do exist - periodic variations in Earth’s orbital eccentricity (over tens of thousands of years), due to the effect of Jupiter and other planets

Gravity of Venus and Jupiter Elongates Earth’s Orbit Every 405,000 Years | Geoscience, Planetary Science | Sci-News.com

We should not underestimate the importance of the Milankovitch cycles. These fluctuations in Earth’s orbit are driven by the effects of the other planets, mostly Venus and Jupiter, but not exclusively so. The effects of these fluctuations are very important in the Earth’s long-term climate, including the repeating cycles of ice age glaciation and the interglacial and interstadial periods when climate is more hospitable in the mid-latitudes. So, yes, Jupiter has a very important effect on Earth.