If a system of particles, like the Solar System, is acted on by an external force, then the centre of mass will move as a result of that force. If there is no external force, then the acceleration of the centre of mass will be zero.
I wrote in the other thread that the Sun “orbits” the solar-system barycenter, but, of course, the complicated motion influenced by Jupiter, Saturn, Neptune, and the rest is hardly a Keplerian orbit, in case that was in question.
To get back to the Op. Sure Jupiter may effect the Earths temp a tiny bit.
But usually these factoids, like with sunspots, are trying to show that Human caused global warming is false.
Nothing, other than human emitted CO2, etc- can account for the rise which is mapped against human caused CO2 etc release.
That rise- which is small and slow (when measured vs human span) is surely caused by humans and is what is concerning scientists- because altho we see it as “slow” it is really fast on a geologic time scale.
I’m somewhat surprised to find that Newton talked about this issue, writing Page:Newton's Principia (1846).djvu/537 - Wikisource, the free online library
“About the sun thus librated the other planets are revolved in elliptic orbits (p 403), and, by radii drawn to the sun, describe areas nearly proportional to the times, as is explained in Prop. LXV. If the sun was quiescent, and the other planets did not act mutually one upon another, their orbits would be elliptic, and the areas exactly proportional to the times (by Prop. XI, and Cor. 1, Prop. XIII). But the actions of the planets among themselves, compared with the actions of the sun on the planets, are of no moment, and produce no sensible errors. And those errors are less in revolutions about the sun agitated in the manner but now described than if those revolutions were made about the sun quiescent (by Prop. LXVI, and Cor. Prop. LXVIII), especially if the focus of every orbit is placed in the common centre of gravity of all the lower included planets; viz., the focus of the orbit of Mercury in the centre of the sun; the focus of the orbit of Venus in the common centre of gravity of Mercury and the sun; the focus of the orbit of the earth in the common centre of gravity of Venus, Mercury, and the sun; and so of the rest. And by this means the foci of the orbits of all the planets, except Saturn, will not be sensibly removed from the centre of the sun, nor will the focus of the orbit of Saturn recede sensibly from the common centre of gravity of Jupiter and the sun”
I summarize this as "The deviations in orbits due to the interaction between the planets (the gravity of Earth on Venus, etc.) are tiny; a bigger effect is the fact that the focus of planet A’s orbit is the center of mass of Sun and all the planets inside the orbit of planet A. Since the center of mass of the Sun and all the planets inside Jupiter is essentially the center of mass of the Sun (since all the inner planets are tiny compared to the Sun), only for Saturn do we have to worry about the effect of Jupiter.
Note that Newton passed away a little over 50 years prior to the discovery of Uranus …
I should have mentioned that, yes.
A paper published last year had the same misconception about Jupiter’s effect on the sun - and that paper was retracted a couple of weeks ago MSN
It’s a lot if you don’t have a diameter of 860,000 miles, shining on a tiny ball 92 million miles away.
Well, Newton was prior to the known discovery of Uranus, at least. Galileo made a few observations of it, but didn’t realize at the time that that’s what he was observing. Under ideal conditions, it can even be seen by the naked eye.
I’m not an astrophysicist or a rocket surgeon, but even I can see that a paper that says the distance varies by 1.85 million miles is inconsequential to the 91 - 94 millions miles the distance usually varies.
People don’t review these papers before they get published?
Fair enough.
1.85 million miles is about 2% of the Earth’s orbital radius - if that kind of motion really happened, it might have some effect on climate. But this motion isn’t real - it’s a misunderstanding of how orbital mechanics works.
That was Neptune that Galileo recorded!
The first definitely recorded sighting of Uranus was by Flamsteed in 1690. (But not recognized as a planet, of course.) That was 3 years after Principia was published so right in the midst of the Newton timeline.
Both cases so close and yet …
I am an astrophysicist and it’s not immediately obvious to me why that variation is inconsequential. Just as an analogy, the Earth’s temperature varies by 100+ degrees F at any given location, but 1 degree rise in the global average temperature is significant.
Papers do get reviewed, but reviewers aren’t always right. And journals don’t always find a completely impartial reviewer.
If Jupiter suddenly vanished, there would be a big effect on Earth’s climate. But that isn’t going to happen.
The important point is that, whatever the details of the complicated “dance” that Earth, Sun and Jupiter engage in, it is a fairly stable periodic dance that was much the same millions of years ago and will be much the same millions of years from now. Whatever effect Jupiter will have on the Earth’s climate is already accounted for in the status quo.
Jupiter’s gravitation, along with Saturn’s, does cause the eccentricity of Earth’s orbit to vary in a long two-frequency cycle. This is the slowest of the Milankovitch cycles which cause cycles in Earth’s climate. But even these effects don’t depend on average Earth-Sun distance or average insolation: the climate changes are caused by the distribution of the arriving sunlight in season and latitude. (When the Ice Age ended 12,000 years ago, the Earth was closer to the Sun during the Northern Hemisphere’s summer than it is now.)