Interesting paper here about a past possible stellar fly by as an explanation for some of the strange orbits, and orbital plane tilts, we see in the solar system
https://iopscience.iop.org/article/10.3847/2041-8213/ad63a6
https://iopscience.iop.org/article/10.3847/2041-8213/ad63a6
I've some catching up to do as I've been otherwise occupied.
The old ticker was experiencing biological time dilation and running slow, so my GP packed me off to hospital.
Fortunately, the consultant (a Mr. Bert Einstein) has assured me that a change of heart medication will make me relatively well again!
The old ticker was experiencing biological time dilation and running slow, so my GP packed me off to hospital.
Fortunately, the consultant (a Mr. Bert Einstein) has assured me that a change of heart medication will make me relatively well again!
I take issue with statements like objects that are further away are "moving faster".
In cosmological redshift, the wavelength at which the radiation is originally emitted is lengthened as it travels through (expanding) space.
Cosmological redshift results from the expansion of space itself and is not due to the motion of distant objects.
Points in four-dimensional spacetime are described using coordinates (x, y, z, ct), where c is the speed of light.
Obviously, the coordinate ct is time dependent.
Thus the metric that defines how distance can be measured between two points in spacetime in terms of the coordinates of those points can change in a way that causes distances to appear larger at later times.
I once shared the following illustration of how the distance between two points depends on the metric used to measure it.
Take the simple example of measuring the distance between two cities on the Globe.
If I use a straight line cut through the Earth's crust, I would find the distance between Los Angeles and New York to be 2,428 miles.
If I now measure along the spherical surface of the Globe, I would find that the distance between the two cities has increased to 2,468 miles - even though their positions on the Globe have not changed.
Spacetime is a bit like that. The distances between spacetime events can change depending on the metric with which they are measured (and that metric is changing with time).
Take the simple example of measuring the distance between two cities on the Globe.
If I use a straight line cut through the Earth's crust, I would find the distance between Los Angeles and New York to be 2,428 miles.
If I now measure along the spherical surface of the Globe, I would find that the distance between the two cities has increased to 2,468 miles - even though their positions on the Globe have not changed.
Spacetime is a bit like that. The distances between spacetime events can change depending on the metric with which they are measured (and that metric is changing with time).
However you want to frame it Galu, distant galaxies are receding from us, and the further away they are, the greater the recession rate.
The constancy of the velocity of c over cosmological time scales has been called into question in numerous papers, though not well accepted by mainstream physics because it would affect i.a.o electromagnetic theory.
https://cosmosmagazine.com/science/...ight-faster-at-the-beginning-of-the-universe/
Sorry to hear this. Trust you will make a speedy recovery and we can continue to spar on this thread 😉
Take your Meds and get better...we need the likes of you and your solid research; otherwise Bonsai would be at a loose end!
I'm sure that, a wee while back, Steve gave a particular example of a star which passed close to our solar system in the distant past.
Apparently, quaternions underlie Einstein's special theory of relativity by behaving like coordinates in 4D spacetime.
Quaternions have 4 dimensions, one real dimension and 3 imaginary dimensions known as i, j and k.
Sir William Hamilton's "flash of genius" so excited him that he was prompted to vandalise a bridge with 19th century graffiti!
Don’t know what happened with my last post.
Anyway, Sabine Hossenfelder has put up a video about the paper I linked to eatlier. Very interesting
Anyway, Sabine Hossenfelder has put up a video about the paper I linked to eatlier. Very interesting
Redoing my penultimate post:
IIUC they’d have been quite a few ideas about stellar flybys over the years but this paper looks to be the first that has looked at it in this detail (3000 simulations). We are due another flyby in about 1 million years.
As SH points out, these events have huge potential to disrupt objects and planetary orbits. One of the as yet unexplained things is why the inner rocky planets are where they are, and the gas giants much further out. In a nascent planetary disc, you would expect most material to be towards the centre and thus the gas giants to located there and this somewhat mirrors what has been observed in other systems.
IIUC they’d have been quite a few ideas about stellar flybys over the years but this paper looks to be the first that has looked at it in this detail (3000 simulations). We are due another flyby in about 1 million years.
As SH points out, these events have huge potential to disrupt objects and planetary orbits. One of the as yet unexplained things is why the inner rocky planets are where they are, and the gas giants much further out. In a nascent planetary disc, you would expect most material to be towards the centre and thus the gas giants to located there and this somewhat mirrors what has been observed in other systems.
I'll get round to Sabine's video later.
The outer solar system is indeed a chaotic place. Classical celestial mechanics has a tough job keeping track of all the goings on.
The n-body problem, orbital resonances, chaotic orbits etc. etc. - what a jumble of perturbations!
Even the venerable and empirical Titius-Bode Relation of Planetary Distances, aka Bode's law, breaks down after reaching the orbit of Uranus.
https://www.britannica.com/science/Bodes-law
Note the inclusion of Ceres, a member of the asteroid belt, chosen to represent a planet once thought to have existed between the orbits of Mars and Jupiter. I wonder what catastrophic event befell that hypothetical body?
The outer solar system is indeed a chaotic place. Classical celestial mechanics has a tough job keeping track of all the goings on.
The n-body problem, orbital resonances, chaotic orbits etc. etc. - what a jumble of perturbations!
Even the venerable and empirical Titius-Bode Relation of Planetary Distances, aka Bode's law, breaks down after reaching the orbit of Uranus.
https://www.britannica.com/science/Bodes-law
Note the inclusion of Ceres, a member of the asteroid belt, chosen to represent a planet once thought to have existed between the orbits of Mars and Jupiter. I wonder what catastrophic event befell that hypothetical body?
I've watched Sabine's video and have read the IOP paper. Here's a brief summary:
Computer simulations suggest that moons which occupy unusual retrograde orbits round Saturn and Jupiter may be objects outside Neptune's orbit (TNOs) that have been injected deeper into the solar system by a close stellar flyby.
Computer Simulation
There's a shorter, non-technical article about the stellar flyby here: https://www.copernical.com/news-public/item/47362-2024-09-11-07-55-16
Quote: "The best match for the outer solar system we found in our simulations was a star slightly lighter than the Sun - about 0.8 solar masses. This star passed by our Sun at a distance of about 16.5 billion kilometers, which is roughly 110 times the distance from Earth to the Sun and almost four times the distance of Neptune."
Computer simulations suggest that moons which occupy unusual retrograde orbits round Saturn and Jupiter may be objects outside Neptune's orbit (TNOs) that have been injected deeper into the solar system by a close stellar flyby.
Computer Simulation
There's a shorter, non-technical article about the stellar flyby here: https://www.copernical.com/news-public/item/47362-2024-09-11-07-55-16
Quote: "The best match for the outer solar system we found in our simulations was a star slightly lighter than the Sun - about 0.8 solar masses. This star passed by our Sun at a distance of about 16.5 billion kilometers, which is roughly 110 times the distance from Earth to the Sun and almost four times the distance of Neptune."
I don't want to imagine what would happen if Saturn or Jupiter were, subsequent to a close stellar flyby, tipped out of their currently quite circular orbits to highly elliptical orbits around the Sun. For my money, it would be a disaster.
I wonder what happened to Uranus?
Unlike the other planets which revolve round the Sun like spinning tops, Uranus is more like a rolling ball going round the Sun.
Rather than the Uranian axis of rotation pointing 'up' like those of the other planets, it points along the ecliptic plane.
What could have caused the extreme axial tilt of Uranus? Some sort of collision that occurred billions of years ago?
Unlike the other planets which revolve round the Sun like spinning tops, Uranus is more like a rolling ball going round the Sun.
Rather than the Uranian axis of rotation pointing 'up' like those of the other planets, it points along the ecliptic plane.
What could have caused the extreme axial tilt of Uranus? Some sort of collision that occurred billions of years ago?
But still no news on the TCrB nova event which was expected between February and September.
I hope you haven't given up looking, especially now you have your new Nikkor 35mm, f1.8 lens!
As far as planets go, Jupiter is the ‘big boi’.
Seems to me everything got tipped a bit on its axis with Uranus taking the brunt of it. Jupiter, because of its huge mass, managed to stay more or less upright. IIRC, the general orbital plane of the planets is 11 degrees off the n-s axis of the Sun’s axis of rotation. In other words, the planetary orbital plane is tipped and so are the planetary axis. Are the two related or did they arise from separate causes?