The Dumb Science Questions - Pro Science Answers Megathread

[Doomed Predator]

Yeah, at physical extremes you get crazy shit like Superfluids. I'm interested in knowing what might be happening inside that rocky core, and what might be left after said core is "liberated" from extreme pressures of the Gas Giant.

The 'gradual easing' makes it LESS likely you'd see anything exciting, since it would have time to re-equilibriate into whatever the 'normal' form was.

True, but there are plenty of instances where at extreme states, matter aligns itself in weird ways that it retains when temperature and pressure return to more "normal" levels. Alloys being the most obvious example that comes to mind.

How are alloys in any way weird?


AFAIK, most of the weird stuff that forms under extreme heat/pressure would just revert to it's "basic form" as the gas giant would lose matter and thus lessening the pressure and heat.

[Tarminic]

Yeah, at physical extremes you get crazy shit like Superfluids. I'm interested in knowing what might be happening inside that rocky core, and what might be left after said core is "liberated" from extreme pressures of the Gas Giant.

The 'gradual easing' makes it LESS likely you'd see anything exciting, since it would have time to re-equilibriate into whatever the 'normal' form was.

True, but there are plenty of instances where at extreme states, matter aligns itself in weird ways that it retains when temperature and pressure return to more "normal" levels. Alloys being the most obvious example that comes to mind.

How are alloys in any way weird?


AFAIK, most of the weird stuff that forms under extreme heat/pressure would just revert to it's "basic form" as the gas giant would lose matter and thus lessening the pressure and heat.

Weird isn't the right word, really. Alloys are an example of instances where a material is altered by high temperatures in ways that don't simply revert to their previous structure after they cool.

Some googling revealed that there are specific crystal formations of some metals that only occur under extreme pressure but are retained afterward. I'm interested in figuring out whether something like this might exist at the rocky core of a Gas Giant.

[FourFiftyFour]

Is there an upwards limit on how many elements could possibly exist?

[Evelgrivion]

Is there an upwards limit on how many elements could possibly exist?

As in different kinds of elements? If so, yes there is; radioactivity is a manifestation of elemental instability. I don't have a clue what physical processes actually result in insufficient strength to hold super heavy elements together, but it's because of radioactive decay that you don't generally see any element heavier than uranium naturally.

[Mona]

Is there an upwards limit on how many elements could possibly exist?

As in different kinds of elements? If so, yes there is; radioactivity is a manifestation of elemental instability. I don't have a clue what physical processes actually result in insufficient strength to hold super heavy elements together,

Electromagnetic force.
Protons have positive charge, so they repel each other. Strong force (or in this case nuclear force) is 100 times stronger than electromagnetic and can hold them them up to 3 femtometers, but if atomic nucleus gets bigger, and have lots of protons, then it's in trouble.

[shaewyn]

Is there an upwards limit on how many elements could possibly exist?

As in different kinds of elements? If so, yes there is; radioactivity is a manifestation of elemental instability. I don't have a clue what physical processes actually result in insufficient strength to hold super heavy elements together,

Electromagnetic force.
Protons have positive charge, so they repel each other. Strong force (or in this case nuclear force) is 100 times stronger than electromagnetic and can hold them them up to 3 femtometers, but if atomic nucleus gets bigger, and have lots of protons, then it's in trouble.

Electromagnetic force (between protons) is trying to push the nucleus apart. Strong Nuclear Force holds them and the neutrons together. To keep a larger nucleus stable, more neutrons are needed (hence why helium and some of the low elements have equal number of neutrons and protons, but the heavy elements have many more neutrons than protons).

As nuclei get larger, they get less stable. Bismuth (83 protons, 126 neutrons) is the largest stable nucleus. If you start adding more neutrons or protons from there, the nucleus is unstable - it will decay, either through alpha or beta decay, until it becomes stable again. Certain combinations of neutrons and protons are "more" or "less" stable, with half-lives from millions of years to fractions of seconds, but Bismuth is still the heaviest stable element.

So, to answer the original question, there's not really a "theoretical" limit on how many neutrons/protons you could *try* to cram into a nucleus, but there sure is a practical limit, as with many of the heavy elements, they fly apart almost instantaneously.

For more reading, see http://en.wikipedia.org/wiki/Island_of_stability

[elmicker]

Electromagnetic force.
Protons have positive charge, so they repel each other. Strong force (or in this case nuclear force) is 100 times stronger than electromagnetic and can hold them them up to 3 femtometers, but if atomic nucleus gets bigger, and have lots of protons, then it's in trouble.

This.

This is best described in pictorial form, wikipedia to the rescue.



So, as you can see, there is effectively a hard limit on the stability of nuclei, beyond which they'll spontaneously undergo fission in infintesimally small fractions of a second. We can probably make them, but they won't be around for very long at all.

I'll spoiler this one because it's lolhueg, it illustrates the relationship between the size of a nucleus and the energy binding it together, or the amount of energy required to break it up.

  Spoiler:

As you can see, smaller than iron, the larger nuclei get the more stable they get, due to the dominance of the strong force. As they get larger than iron, the electromagnetic force begins to outmuscle the very shot ranged strong force, making the nucleus less stable the larger it gets.

The other interesting thing to note is the discontinuities. Helium 4, Carbon 12 and Oxygen 16 are near-ideal nuclei. I seem to recall something about that 2:2 pairing of protons and neutrons being super stable or something but I can't be sure.

Personally I always found the graph more intuitive thinking about things in reverse. Instead of thinking about how stable the nuclei are, we should think about how much energy they store - how much energy we'd get out breaking them up or smashing them together.

  Spoiler:

That always made it much more clear to me why light nuclei undergo fusion and heavy nuclei undergo fission. You can reverse the situation, but you end up consuming energy, locking it into the nucleus, making the process inherently limited, as opposed to the net energy gain of the natural process.

ed: and beaten to the punch while typing this up. hooray.

[shaewyn]

Typing speed success!

Also, I quite like that "upside down" binding energy graph.

[Zeekar]

This graph reminds me, are there any other catalysts for fusion except muons? Tau comes to mind but i assume the mass and the short life span rule it out?

[SAI Peregrinus]

This article is very good for learning a bit more about the stability of the nucleus (and the neutron).

[FourFiftyFour]

So a follow up question.

As science discovers more and more about particle (right word?) does the possibility of working around the strong nuclear an electro magnetic forces arise or are we stuck with box of Legos we already have?

[Muffinsrevenger]

All i can think of is that the elements should result in harmony

is this bad c/d?

[kyrieee]

As nuclei get larger, they get less stable. Bismuth (83 protons, 126 neutrons) is the largest stable nucleus. If you start adding more neutrons or protons from there, the nucleus is unstable - it will decay, either through alpha or beta decay, until it becomes stable again. Certain combinations of neutrons and protons are "more" or "less" stable, with half-lives from millions of years to fractions of seconds, but Bismuth is still the heaviest stable element.

Just to add to that, the reason it happens is because the binding force (the strong nuclear force) decays in strength much more rapidly over distance than the electromagnetic force. In a large nucleus the neutrons on one side don't interact with the strong force (they only "feel" their closest neighbors), they are simply too far apart, but the protons still repel at that distance. So basically, as the nucleus grows the relationship between the forces changes, the EM force becomes dominant.

[shaewyn]

As nuclei get larger, they get less stable. Bismuth (83 protons, 126 neutrons) is the largest stable nucleus. If you start adding more neutrons or protons from there, the nucleus is unstable - it will decay, either through alpha or beta decay, until it becomes stable again. Certain combinations of neutrons and protons are "more" or "less" stable, with half-lives from millions of years to fractions of seconds, but Bismuth is still the heaviest stable element.

Just to add to that, the reason it happens is because the binding force (the strong nuclear force) decays in strength much more rapidly over distance than the electromagnetic force. In a large nucleus the neutrons on one side don't interact with the strong force (they only "feel" their closest neighbors), they are simply too far apart, but the protons still repel at that distance. So basically, as the nucleus grows the relationship between the forces changes, the EM force becomes dominant.

Yep, exactly... which leads to my pondering...

Gravity is easily the weakest of the fundamental forces. My question is not "why is gravity the weakest", but "why does gravity have the largest (apparent) range?" Why does gravity easily have an effect over megaparsecs, but the other forces have far shorter ranges?

[elmicker]

The electromagnetic force has an infinite range too, it's just all matter, in most cases, has equal numbers of positive and negative charges, so the effects over a long range are neutralised extremely quickly. Gravity has no such opposite partner, so gravity keeps on going and going and going and going.

[Qwert]

As nuclei get larger, they get less stable. Bismuth (83 protons, 126 neutrons) is the largest stable nucleus. If you start adding more neutrons or protons from there, the nucleus is unstable - it will decay, either through alpha or beta decay, until it becomes stable again. Certain combinations of neutrons and protons are "more" or "less" stable, with half-lives from millions of years to fractions of seconds, but Bismuth is still the heaviest stable element.

Just to add to that, the reason it happens is because the binding force (the strong nuclear force) decays in strength much more rapidly over distance than the electromagnetic force. In a large nucleus the neutrons on one side don't interact with the strong force (they only "feel" their closest neighbors), they are simply too far apart, but the protons still repel at that distance. So basically, as the nucleus grows the relationship between the forces changes, the EM force becomes dominant.

Yep, exactly... which leads to my pondering...

Gravity is easily the weakest of the fundamental forces. My question is not "why is gravity the weakest", but "why does gravity have the largest (apparent) range?" Why does gravity easily have an effect over megaparsecs, but the other forces have far shorter ranges?

Gravity and EM have the same range (1/r^2), and EM is RIDICULOUSLY stronger than gravity (see also, magnet picking up a paperclip vs the ENTIRE PLANET puling it down).

At large scales, however, matter tends to be electrically neutral. Since EM functions on difference in charge while gravity just functions on mass, the more neutral the material, the more gravity matters. Grabbin an old reddit post:

To paraphrase wiki ( http://en.wikipedia.org/wiki/Fundamental_forces ):

If you were to place two four kilogram (~1 US gallon) jugs of water a meter apart, their electrons would repel each other with 4.1 x 10^26 N of force. This is larger than what the planet Earth would weigh if weighed on another Earth. The nuclei in one jug also repel those in the other with the same force. However, these repulsive forces are cancelled by the attraction of the electrons in jug A with the nuclei in jug B and the attraction of the nuclei in jug A with the electrons in jug B, resulting in no net force. Electromagnetic forces are tremendously stronger than gravity but cancel out so that for large, neutral, bodies gravity dominates.

[shaewyn]

yep! It's that whole "opposite charges" thingy. Reminds me of an article that I read that suggested that antimatter might react as "negative" for gravity (just proposed it, they didn't have any evidence)

[definatelynotKKassandra]

yep! It's that whole "opposite charges" thingy. Reminds me of an article that I read that suggested that antimatter might react as "negative" for gravity (just proposed it, they didn't have any evidence)

This suggestion is complete horseshit.

NB not an attack on you, just a note in case anyone thinks this idea has any basis in reality.

[balistic void]

As nuclei get larger, they get less stable. Bismuth (83 protons, 126 neutrons) is the largest stable nucleus. If you start adding more neutrons or protons from there, the nucleus is unstable - it will decay, either through alpha or beta decay, until it becomes stable again. Certain combinations of neutrons and protons are "more" or "less" stable, with half-lives from millions of years to fractions of seconds, but Bismuth is still the heaviest stable element.

Just to add to that, the reason it happens is because the binding force (the strong nuclear force) decays in strength much more rapidly over distance than the electromagnetic force. In a large nucleus the neutrons on one side don't interact with the strong force (they only "feel" their closest neighbors), they are simply too far apart, but the protons still repel at that distance. So basically, as the nucleus grows the relationship between the forces changes, the EM force becomes dominant.

And just to add more to this, there can exist "islands of stability". There could be some crazy element 200 elerium-esque stuff that is incredibly rare and stable. Can't disprove otherwise. They are stable coz of weird quantum mechanical effects, the protons arrange themselves in some freak stable configuration (think of a buckyball or something like that).

Also this -> http://en.wikipedia.org/wiki/Allotropy Radioactive elements can also exist in stable allotropes.

Isotope = same element, but different number of neutrons.
Allotrope = same element, same neutrons, but different stable configuration.

Remember stuff like Uranium etc gets formed in supernovae, that's how much energy it takes to form these kinds of heavy elements. In a nuclear reactor the actual power comes from supernova faeces
edit: Pretty much all elements above helium come from supernovae I think, not just the heavy stuff. Astronomers call everything above helium a metal
edit2: The heavy stuff actually gets formed in supernova... the other stuff (think carbon and nitrogen and oxygen etc) get formed during "normal" star burning, but then get scattered during supernova. Just to be correct about stuff.

[Maximillian]

It is believed that a number of super-heavy elements are created in the supernova of stars between 100 - 200 solar masses. In part that is why these supernova are far brighter and last longer than the nova from smaller stars - the expelled gas being heated by the chain-reaction half-life decay of a whole series of unusually elements decaying down to a stable state emitting energy.