[clueless (OP)]

Inspired by  Anthony Peake, who suggests that most of atom is empty space, the question in the title stands, considering ALL matter of astronomical bodies in our Solar System; that is to say, I guess I need a hot-air balloon in a SF story of mine to make a point; but it doesn't necessarily have to be a "darn" hot-air balloon, perhaps something else, maybe a fruit. Thanks a lot. 

[Janus]

If you took the Sun (which makes up the vast majority of the Solar system's mass), and compressed it down until it was essentially nuclei rubbing up against nuclei, it would still fill a sphere over 11 km in radius.
Jupiter, the next largest body would form a sphere ~1 km in radius.

[yor_on]

Prove it!

At a distance, please.

[clueless (OP)]

This is, actually, important, that is to say, I'm ambitiously writing a SF book; so please be precise, if You can do just that, or else I'll end up like Dan Brown who wrote The Da Vinci Code: rich and miserable. Yes. That is very interesting information about the Sun and the planet, and I'm thinking about using it; but - is it 100% authentic? How about at least 70%?

P.S. I am still having trouble of letting the hot-air balloon go, so if you can think of a certain astronomical body that would indeed (more or less) fit in a hot-air balloon, I'd be greatly appreciated.

[Origin]

P.S. I am still having trouble of letting the hot-air balloon go, so if you can think of a certain astronomical body that would indeed (more or less) fit in a hot-air balloon, I'd be greatly appreciated.

You can figure it out yourself rather easily knowing that the density of a neutron star is

[Janus]

This is, actually, important, that is to say, I'm ambitiously writing a SF book; so please be precise, if You can do just that, or else I'll end up like Dan Brown who wrote The Da Vinci Code: rich and miserable. Yes. That is very interesting information about the Sun and the planet, and I'm thinking about using it; but - is it 100% authentic? How about at least 70%?

P.S. I am still having trouble of letting the hot-air balloon go, so if you can think of a certain astronomical body that would indeed (more or less) fit in a hot-air balloon, I'd be greatly appreciated.

The density of an atomic nucleus is 3e17 kg/m^3,  So it is a simple matter to take the mass of any body, like the Sun, and work out its size if it had that density.  Is it 100% accurate?  No, it would actually be an underestimate in size.  This is because the type of body that could physically form if you compressed the Sun down would be a neutron star, and the average density of it isn't quite as high as that of a nucleus. 
If we use the neutron star density value as given by Origin, and estimate the volume of a hot air balloon as being the equivalent of a sphere with a radius of 3m, then (roughly), the largest mass it could contain would be ~7e18 kg,  There are a number of moons in our solar system that are smaller than that.
But now we come up against the practicality of such a venture. Even if you could compress a body of that mass down to a sphere 3m in radius, you now would have to deal with the fact that the surface gravity would be in the millions of g.  If you tried to surround it with a hot air balloon, the material of the balloon would be crushed to the point that it would no longer maintain its molecular structure and would become part of the surface of the object itself.

[Kryptid]

You can figure it out yourself rather easily knowing that the density of a neutron star is

I'll go ahead and do that.

Radius of sphere from volume = ³√((3 x volume)/(4 x pi))

Mass of the Sun = 1.9885 x 10³⁰ kilograms

v_Sun = (1.9885 x 10³⁰ kilograms)/(10¹⁷ kilograms per cubic meter)
v_Sun = 1.9885 x 10¹³ cubic meters

r_Sun = ³√((3 x (1.9885 x 10¹³ cubic meters)/(4 x pi))
r_Sun = 16.807 kilometers

Mass of Jupiter = 1.8982 x 10²⁷ kilograms

v_Jupiter = (1.8982 x 10²⁷ kilograms)/(10¹⁷ kilograms per cubic meter)
v_Jupiter = 1.8982 x 10¹⁰ cubic meters

r_Jupiter ​= ³√((3 x (1.8982 x 10¹⁰ cubic meters)/(4 x pi))
r_Jupiter = 1.655 kilometers

Mass of Earth = 5.9724 x 10²⁴ kilograms

v_Earth = (5.9724 x 10²⁴ kilograms)/(10¹⁷ kilograms per cubic meter)
v_Earth = 5.9724 x 10⁷ cubic meters

r_Earth ​= ³√((3 x (5.9724 x 10⁷ cubic meters)/(4 x pi))
r_Earth = 242.5 meters

Mass of Moon = 7.342 x 10²² kilograms

v_Moon = (7.342 x 10²² kilograms)/(10¹⁷ kilograms per cubic meter)
v_Moon = 7.342 x 10⁵ cubic meters

r_Moon ​= ³√((3 x (7.342 x 10⁵ cubic meters)/(4 x pi))
r_Moon = 55.964 meters

Mass of Ceres = 9.3835 x 10²⁰ kilograms

v_Ceres = (9.3835 x 10²⁰ kilograms)/(10¹⁷ kilograms per cubic meter)
v_Ceres = 9.3835 x 10³ cubic meters

r_Ceres ​= ³√((3 x (9.3835 x 10³ cubic meters)/(4 x pi))
r_Ceres = 13.085 meters

[Eternal Student]

Hi everyone,

I'm ambitiously writing a SF book; so please be precise

   Well how fantastic or science fiction do you want to go, in that book?
    The earlier posts have talked about the most dense forms of matter we know about,   e.g.  Neutron stars.

    However, there do seem to be objects in space that are over-dense Neutron stars  or  what could be described as totally collapsed objects.    These things are of course, Black Holes.
    Let's assume that to be remotely sensible, the surface of your balloon must be placed around the outside of the event horizon of a black hole.   Then we just need to see how much mass we can fit into a black hole with that Schwarzschild radius.

We're going to assume a simple, non-charged and non-rotating black hole  -  A Schwarzschild Black Hole.
     The Schwarzschild radius is given by:

     

Where  G = universal gravitational constant;    c=  speed of light;   M = a parameter that we can think of as the mass contained in the black hole (if we try to keep everything as simple as possible).

   I would do the calculations but that would be just tedious.   There's an online calculator tool you can use,  here's the link to one of those:
https://www.omnicalculator.com/physics/schwarzschild-radius
   I don't know if it's actually reliable, just that I'm too lazy to use my own calculator and a pencil.

Anyway,  let's take the example Kryptid gave earlier,   for an asteroid like Ceres, it would have a radius of 13m if we compressed it into a Neutron star.  If we compressed it until a black hole formed,  the Schwarschild radius would only be 0.000001 m,    which is quite a bit smaller.

   Conversely, if you allowed a balloon of radius 13m  then we can stuff    8 x 10²⁷  Kg   into a black hole to have a Schwarzschild radius of that size.   That's about 10¹⁰  objects like Ceres,  or  4 planets like Jupiter.

Best Wishes.

[Zer0]

Hmm... perhaps a stoopid thought...

But is there a possibility the Balloon could be made out of Dark Matter Fabric?

& Possibly propelled by Dark Energy?

Ps - Dark Matter has the Power of slowing down Galaxies.
Dark Energy has the Potential of ripping apart the Cosmos.

Why rely on lame matter, when you got exotic matter at your disposal.
Newyz, All thee Best!!!
👍

[Janus]

Hmm... perhaps a stoopid thought...

But is there a possibility the Balloon could be made out of Dark Matter Fabric?

& Possibly propelled by Dark Energy?

Ps - Dark Matter has the Power of slowing down Galaxies.
Dark Energy has the Potential of ripping apart the Cosmos.

Why rely on lame matter, when you got exotic matter at your disposal.
Newyz, All thee Best!!!
👍

Dark matter is "dark" because it doesn't interact electromagnetically (and thus doesn't interact with electromagnetic radiation.) You need electromagnetic interaction to make a tightly bound structure like a fabric. DM can't be made into "things"  like balloons.

[clueless (OP)]

Thanks all for your fine thoughts and reasoning. To paraphrase One (a drone from Star Trek), I'll need time to assimilate this information. But I'm certain that I'll use some of what two members propose.

[Zer0]

Hi J
😊

Mmm...but Dark Matter interacts with Normal Matter.
Like by providing it extra mass?

Why can't a balloon cloud of Dark Matter engulf a small solar system.

& Did that Chandra Yan from NASA really detect Dark Matter clouds interacting with it's ownself?
🤔

U know, i feel like the Universe in itself is like a balloon.
Won't Dare use the term GOD...
But sumthin or sumone seems to be really blowing hard onnit yaa!
🤭
(Wish the was an alternate hypothesis which could negate Dark matter & energy n just explain the Universe in a simpler format.)
Anyways, Thanks!
🍭

[Halc]

but Dark Matter interacts with Normal Matter.
Like by providing it extra mass?

Dark matter does not provide anything with extra mass any more than a planet adds mass to the star it orbits. But the mass of the dark matter affects spacetime the same as ordinary matter, so all matter, dark or not, is attracted gravitationally to each other.

Why can't a balloon cloud of Dark Matter engulf a small solar system.

Dark matter doesn't clump into clouds with local density. To do that it would need to have to slow down as it fell into its own gravity well, and it can't slow down if it can't interact. So the speed of any particular bit of dark matter tends to be greater than the escape velocity of any local object it happens to find itself in the vicinity of. The deeper the gravity well, the more likely that dark matter will enter but then leave it. Regular matter tends to remain behind because it is slowed by friction.

Wish the was an alternate hypothesis which could negate Dark matter & energy n just explain the Universe in a simpler format.

Be glad it's complicated. The simple universes don't have complicated things like us in them.

[Petrochemicals]

It may do. Just depends how much energy you remove from the constituent parts of matter. A standard A bomb does not release much of the nuclear binding energy in uranium, that itself is only a very small percent of the total binding energy known to be in the constituent parts.

https://www.nationalgeographic.com/science/article/110524-densest-matter-created-lhc-alice-big-bang-space-science

Quark gluon plasma is very dense but also quite hot.