Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: clueless on 21/02/2024 15:34:20
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This question has to do with a story of mine I'll most probably include in my manuscript about strange stories.
Imagine stick out of neutronium, two-dimensional (length and height), perfectly symmetrical, so long that it is bigger than the Sun's diameter. It is traveling in the Solar System towards the Sun. Since immense gravity of the Sun bends space and time, if the stick approaches the Star sideways, is it true that, because of strong gravity and space bent around the Sun, that the mysterious stick would be bent as well, so that it forms a perfect circle, ring around the Sun, extending 200.000 miles from the star? If so, and I offer apologies for being a bit ignorant at science, how long would the stick have to be so that it forms a perfect, perfect ring around the Sun (extending 200.000 miles from the star)? And would this mysterious stick cause some disturbance to the Sun and its activity simply by being there, since alignment of planets etc. in the Solar System is a delicate matter and even a slight change of an angle of a planet could potentially cause a bigger problem to the entire Solar System? Thank You.
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Amusingly Interesting question.
: )
I am Clueless too.
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The neutronium would collapse into a sphere (or almost a a sphere if it was rotating)
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Hi.
The neutronium would collapse into a sphere...
Just to be clear, that would happen just because of the Neutroniums self gravity, i.e. it would happen long before it even reached the sun. So you just can't maintain a long stick of the stuff.
However, I'm not even sure that is the only problem. How do you sustain neutronium as neutronium without always having it under compression caused by its own gravity? Neutronium is stuff you find in a Neutron star. It is essentially just some neutrons tightly packed together. If you somehow managed to scoop some up and take it away from the neuron star then it would expand. The Fermi exclusion principle no longer prevents electrons from occupying this increased amount of space volume and so some neutrons will decay into protons + electrons. Overall the stuff can quickly become more conventional stuff - ordinary complete atoms with neutrons, protons and electrons. This is not stuff you would continue to call "neutronium".
So, you just don't ever have the ability to consider a long stick of Neutronium without putting some more fantastic or science fiction assumptions along with it: You need some way, some Sci Fi force-field perhaps to keep the neutronium under extreme compression all the time. Presumably that force-field along the edges of the stick is also sufficient to keep it long and straight rather than collapsing together to form a sphere. The remainder of the question is then un-answerable or could be answered any way you want. Does the force-field still allow the gravitational effects of the neutronium to pass through it?
And would this mysterious stick cause some disturbance to the Sun and its activity
Yes, you would have thought so. There are a few (maybe a hundred?) complications. For example, if you somehow have this extremely dense matter approaching the sun, then the tidal forces acting the sun could become severe when this dense stuff is close enough. The sun will certainly deform a bit and if the tidal forces are too large it is ripped apart. You mentioned staying 200 miles away from the sun and that might be OK. See this wikipedia article: https://en.wikipedia.org/wiki/Roche_limit that describes "the Roche limit" - the point at which an object would start to be pulled apart by tidal forces due to a second object it is approaching. Usually we consider an object being ripped apart as it approaches the sun (because the sun is the more massive thing) but since your neutronium is so very dense, it may be the sun that is ripped apart as it approaches the neutronium. We'd need more information, such as the total amount or mass of your stick of neutronium to perform the calculations and check to see if the sun disintegrates at 200 miles from this big stick of Neutronium.
(Minor note: If the sun is shredded as per the description in Wikipedia, then it will be bits of the sun that forms rings around the Neutronium rather than the Neutronium stick bending to form a ring around the sun).
Best Wishes.
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Thanks all for commenting, be it a witty reply, because of the healing power of laughter, or a concrete answer. Yes, that is very interesting, Eternal Student and others. I see I'll have to do my homework or be more specific.
My mind turned to clay, and all I that can't think of at the moment would be some other alloy (of the stick), steel or another material, other than neutronium, perhaps an alloy of neutronium, something similar and not so similar, seen in some science fiction shows, no matter how unrealistic that may well be, with EM shields or not. Is it then possible for this stick, enormously long, to, somehow, become the 'darn' ring around the Sun, perfectly symmetrical, considering the space around the Sun that's bent by its immense gravity, or it must be crushed, ripped apart to pieces?
I offer ten thousand apologies for being clueless, again. But at the very least I'm not alienated as long as Zer0 is Clueless too. Join the club! Perhaps not. No need to strive to provide a perfect answer, just if You have an additional idea, that is very welcome, even if it is fantastic, yet possible in SF, regarding the Sun's future ring. I've other stories as well, and not necessarily SF, so this one, no matter how intriguing, is not the only one. Thanks for your efforts. You've already answered quite a bit.
Usually we consider an object being ripped apart as it approaches the sun (because the sun is the more massive thing)...
Must this very long stick, out of a certain other alloy, be ripped apart for sure? Is it at all likely for the stick to get not too close or too far from the Sun, just the right distance, so that it wouldn't be ripped apart, rather form a stable ring (which You call a sphere, perhaps a Dyson sphere, even if the stick, rather than a wall, is no more than, say, 20 cm wide)?
Presumably that force-field along the edges of the stick is also sufficient to keep it long and straight rather than collapsing together to form a sphere.
This part I don't get (science is not my strong suit). I thought that space is bent around the star, so how can this stick defy space that is bent, even if equipped with EM field? Isn't the stick, well, inside this space that is bent around the Star - where else could it be? - so no matter how strong or resistant the stick is, it ought to bend, at the very least, just like the space it occupies? I guess I'm talking nonsense to You, neither do I completely comprehend gravity, being a bit more confused than usual. Perhaps this story is too ambitious for me. Aw.
Later.
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Hi.
I offer ten thousand apologies for being clueless, again.
That's no crime, none of us will know everything. It's also highly commendable that you are prepared to just come out and say something like that.
be it a witty reply,
It wasn't meant to be witty in the sense of being downgrading, that was not my intention. I must apologise if that's how it seems. This is the main Physics, Astronomy and Cosmology section of the forum. In here replies should first and foremost be based on mainstream science. In other sections, like "Just Chat" or "New theories" the guidelines are less restrictive. I don't think it matters and I don't think you need to move your discussion. It's just important that you realise that @Bored chemist and @Eternal Student (me) were somewhat obligated to provide an answer based on mainstream science in the first instance.
Must this very long stick, out of a certain other alloy, be ripped apart for sure?
No. Rigid bodies where there are inter-atomic forces holding the body together can get very close to the sun before tidal forces should tear them apart. Indeed they could get so close that they have entered the outer layers of the sun and from there in toward the very centre of the sun, the total gravity they experience is reduced (they will only experience a pull toward that bit of the sun that is still more inward toward the centre, the bit of the sun that is now forming a shell exterior to that rigid body can be ignored - see "the hollow shell theorem" if your interested). So they can get arbitrarily close to the centre of the sun without being torn apart by tidal forces - but other stuff like extereme temperature and pressure would be a problem if they are in the sun.
I thought that space is bent around the star
Yes but for our Sun the curvature of space is still quite small. For every mass there is a certain distance at which the curvature of space gets "out of hand". For convenience we'll say this distance is the Schwarzschild radius although you may consider that the curvature is already quite significant at some multiple of this distance, say twice the Schwarzschild radius. Just to be quite confident that we're in some space where curvature is really not too serious at all, let's take 10 times the Schwarzschild radius.
The Schwarzschild radius of our sun is about 2.9 Km (information source : Science direct https://www.sciencedirect.com/topics/physics-and-astronomy/schwarzschild-radius because I couldn't be bothered to do the calculation myself). So let's say the curvature of space could be significant at ten times this distance ≈ 29 Km. If you were 29 Km away from the centre of a mass equal to our sun, then the curvature of space can be significant.
Now the actual radius of our sun is approximately 700 000 Km (information source: NASA https://science.nasa.gov/sun/facts/#hds-sidebar-nav-3).
As you can see 29 Km is a lot smaller than 700 000 Km. The curvature of space isn't going to be significant until you're inside the sun. As mentioned just above, once you're inside then you can't even consider the entire mass of the sun to be contributing any longer (Hollow shell theorem, only the bit of the sun more interior than the 29Km counts) - so the curvature of space still will not be significant even when you are at 29 Km from the centre of the sun. Overall, our sun is just no-where near dense enough to cause a significant curvature of space.
Summary: There is some (small) curvature of space close to the sun but it's on the scale of effect that can deflect some rays of light by a degree or two and that's all. It's nothing like enough to make a rigid straight rod that was pushed up close to it turn into a bent ring all the way around the sun.
LATE EDITING: Articles discussing the deflection of light rays passing close to our sun are talking about arc-seconds of deflection. 1 arc-second is just a small fraction of 1 degree.
You're talking about effects, curving space in some extreme way, that would really require a star like a Neutron star rather than the humble star that is our sun.
Best Wishes.
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Much appreciated, Eternal Student. That was very helpful.
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This part I don't get (science is not my strong suit). I thought that space is bent around the star, so how can this stick defy space that is bent, even if equipped with EM field?
"Space-time" is said to be "curved". In Relativity, space and time are not the separate and distinct things they were considered in Newtonian physics. So, we have three spatial dimensions, Up-down, left-right, front-back. and a time dimension, past-future. and they are all "connected" in a way.
And saying that space-time is curved means that it doesn't adhere to the Euclidean rules of geometry.
Now, that being said, it is also important to remember that space-time is not some rigid structure that everything is fixed within. If that were the case, then movement would be impossible. Everything would be frozen in its point in space-time.
Nothing is "forced" to follow the local space-time curvature. In can exert an influence, but it is not in insurmountable. Local influences and forces can take precedent.
For example: The universe is expanding, and this is explained by space itself expanding. But this does not mean everything in the universe is expanding. You are not expanding. Earth is not expanding, the solar system is not expanding, our galaxy is not expanding. This is because there are other influences (molecular forces, gravity) that hold these things in shape despite space itself expanding.
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Much appreciated, Janus, for simplifying things. I understand better now.