Fusion, Fission, Quarks and such nonsense.

That still doesn't answer my question, which is, essentially, why is Carbon 14 unstable? Most of the unstable elements are heavier than Iron, but C14 is not. What makes it special?

 

From what I know, that is because it's kind of unnatural, being one of the products (the other one being Hydrogen) of reaction between Nitrogen and free neutrons. More or less, I know there's more to it, but that is the simple explanation.
And why would it be unstable? Because it has too many neutrons compared to protons, for its size at least.

 

Thanks for that information, Lahalito.
Interesting take on things.

From what I knew, it was a big impact, from a Mars size object into the Earth that made the Earth the way it is now.
You do make an interesting point though.
Do keep in mind that the Earth is slowing down as we speak, not just from the moon's gravitational drag, but by itself.
Eventually it will reach a point of tidal locking, and we will have month long days.

It may even get slower after that, due to the fact that nothing can spin forever.The Second Law of Thermodynamics works on planets, too.

Also, Omni,

That's not true.
The density of iron is 7.874 g·cm3
That's grams per cubic Centimeter
Iodine is 4.933 g·cm^3
Which is again, grams per cubic Centimeter.

By contrast, Osmium, the densest naturally occurring element, beating out Iridium is 22.59 g·cm3
Uranium is barely over 19.
The density of an object determines how heavy it is. Not it's place on the Periodic table. Otherwise Uranium would weigh more than the extremely dense iron in the inner core of the Earth.
And that iron, if smelted into a sword, would weigh several thousand pounds.

 

Little do you know that my alter ego is Cobalt man.

I think there's supposed to be an 'island of stability' around 120? That may just mean that they last for a couple of seconds,instead of something more like, you know, attoseconds.

I'm glad we have someone who's more of a professional on this.
Would it not be possible, though, to fuse two atoms to make, say, cobalt or nickel, couldn't you then fission that to theoretically have an infinite amount of energy? Or would the energy needed to fuse or fission outweigh the energy gained at that point, even if someone were to invent cold fusion?
It's great that you've dropped in to inform us though.

 

@ DavidB1111
Ah. I see. That you for the correction.

I always thought that more electrons/protons meant a heavier material. But as I said before, I never even attended High School. I pieced together 90% or more of my knowledge. There are surely more mistakes I have made.

Oh well. I consider it well worth being wrong to learn the right answer.

 

That's my philosophy too.
Don't worry, I promise someday to make you a suit of armor made of that super dense iron. Don't you want to be nuke proof?
Seriously, the core of the earth is so dense, a nuclear detonation directly on it won't even barely put a scratch into the thing.
Disclaimer, I'm not a scientist, so I don't know how the core of the Earth would hold up against something that hot.

 

I think the problem wasn't with your knowledge, but with semantics. I think that you can use heavier to say that it has a greater atomic mass too, so I think you were right there.
(I may be wrong, though, so don't take my word as law here)

 

There is no possible way to extract more energy than is required to chain fuse/fiss something. Not even in fiction. You would use a tremendous amount of energy to fuse things, and again a tremendous amount to break them apart. The only exceptions are those rare cases where it is already a weak link that requires less energy to fuse/fiss something. And they are never duplicative without loads of time and energy.

There are certainly better ways to phrase that, but I do not have the words.

Suffice it to say that we are barely able to break apart fragile molecules, and the gain is only a pitiful amount of the total released when we do. Most is wasted in the process. Controlled Fusion takes probably around a thousand times more energy per molecule than can be gained with our current best methods for fission of the produced molecule.

Even the highest technical nuclear power plants are massive things that rely upon capturing the tremendous energies of trillions of reactions in what is literally nothing more than a sealed steam engine no different from those used on the old steam locomotives of centuries past. Just much much larger and sealed since water can and does absorb radiation.

The flow of steam is controlled by pushing a very long carbon control rod attached to the radioactive element into an area with the water, or pulling it back from the water. Nothing more can be done.

When the water starts escaping, it is called meltdown. That is very literal. Since the heat of the continual reacting element will melt most all metals and earth and sink into the molten Earth. Expended elements from reaction are buried in massive sealed tanks of water that will diffuse the heat and prevent the materials containing it from melting for the thousands of years it will be hot enough to melt them.

We bury nuclear plants in concrete as a long term, last ditch solution when we cannot continue to repair them safely. There is no actual solution to the problem. The entire site will one day be radioactive at unsafe levels. And a million years from now they may still be unsafe to life forms like ours.

 

Omni here is basically right! There's some amplitude of a wavefunction that penetrates anything but an infinite potential energy barrier. The important thing to note here is that when all is said and done, you can't have made any EXTRA energy. This means that particles can leak out of a nucleus, but when you add up all the energy of the system afterwards, it must still be equal to the energy you had to begin. This seems fairly reasonable, but its effect is that some decays are prohibited. Think of a helium nucleus, for instance. 2 protons and 2 neutrons:
http://en.wikipedia.org/wiki/Helium-4
Eh, I don't know if the link is working. Anyway, imagine we want it to decay into a tritium nucleus, and a proton:
http://en.wikipedia.org/wiki/Tridium (heh. The link says "Tridium," but the article says "Tritium." One is spelled wrong.)
http://en.wikipedia.org/wiki/Proton

Let's think about adding up the mass of all three objects (which is proportional to energy. we won't 'waste' energy by letting the tritium or proton move after the decay. I'm lifting all of these from wikipedia, which is sometimes OK about science. We could use the particle data group if we wanted, for which there are other controversies. All of these are in atomic mass units (not important to convert these to something else)
4-He = 4.002602
3-H = 3.0160492
p = 1.007276466812(90)
So if the decay is allowed, we should find that the amount of mass-energy required for 3-H + p is less than that of 4-He:
3-H + p = ~4.02332566
We see that the mass of p + 3-H is greater than that of 4-He! If the 4-He is not very hot, this is impossible. The transition
would produce energy from nothing.We can try to exploit uncertainty (this is going to be an oversimplification!),
but this would require short time scales; the proton wouldn't be allowed to be free for long. In fact, 3-H decays in to 3-He, which
has less mass (unsurprisingly).
So for all those isotopes lighter than iron, we have similar mechanisms to the 3-H example. 14-C is heavier than 14-N + e + neutrino, so the transition is allowed. Probability then describes the chance that the transition will occur, given some amount of time.
Well then what's with everything that's heavier than iron in the first place? For that matter, what's with the existence of every manifestly unstable nucleus? Everything heavier than lead is ALWAYS unstable? How did they get here?
Star dust. It takes a lot of energy to produce fusion, and that's for energetically favorable transitions; from higher energy states to lower ones. It takes a lot MORE energy to move from LOWER energy states to HIGHER ones. It takes so much, in fact, that this really only occurs in supernovae. Every single atom heavier than iron comes from the death of a star. In fact, to a good approximation, everything heavier than lithium comes from the death of a star! Most stars simply don't get hot enough to fuse past lithium. So that's something to ponder for a moment. It's pretty much just hydrogen and helium that formed out of the early universe. How much of what we deal with here on earth isn't either of those two elements? Pretty incredible.

Oh and a cool note about spherical symmetry in radiation: Only most of it is spherically symmetric. There's an effect called "parity violation" that exhibits asymmetry in some decay channels, notably beta decay. Beta decay operates via the weak force, which breaks position symmetry. That is, if something happens in our world through the weak force, if we looked for the same transition with x --> -x, y --> -y and z --> -z (I mean to say we let all of the position coordinates be their negative counterparts; I don't know if you can see that with what I typed out there), we may not see it at all. As far as I know, symmetry properties (parity, charge, time) are basically just an experimental assertion. We have never once seen these symmetries broken for the other three forces, although it's not completely unreasonable theoretically. To be sure, I should stress that a broken symmetry represents an inability for a transition to occur despite adequate energy in the system. For some transitions, there are other ways for them to occur besides the parity violating one. And we know the most about lower energy scales (on the order of TeV). Things may get even more strange at very high energies.


whelp! There's another novel!

 

Wow. This thread is active. Two Three posts while I was typing that mess above.

Any day we do not each learn something is a day we did not live.

 

And indeed, stuff's all gettin' posted while I'm trying to respond...
Omni! You said the same thing I said! Which is awesome.

As for nuclear waste, I had heard different numbers from a visiting prof discussing viable energy schemes. I believe he suggested that we wouldn't NEED to contain the waste for the million years that wiki quotes. Now, I wouldn't go wandering around eating radioactive tin isotopes, but things may be better than some people think. I haven't really looked in to this, so the most I can say is that I've heard conflicting opinions and the source on Wikipedia for how long radioactive waste must be contained is a political action site devoted to eliminating nuclear energy. What I can say is that the radiation is dangerous if it tends to ionize particles you need to live. Also, there are ways to reuse some of the fuel we in the US tend to bury in mountains, but we don't like to do it because...hmm...I can't remember the precise reasons...I think either it produces byproducts that are good for weapons, and we don't like making weapons just any old place, or the byproducts are more dangerous on a shorter time scale...Anyway, France has facilities that research uses for nuclear waste, and I think they reuse some of it in special nuclear reactors as well. One thing I do remember is that, if you reuse the fuel, the NEW nuclear waste decays faster than the old nuclear waste would have.

 

Great minds think alike.

The truth on nuclear waste may never be known to us. There are a million and one odd rumors and different reasons and laws and such. But all we know for sure is that nuclear waste is bad to be in close proximity to. And that includes being in proximity to things that have been in proximity to them. To varying degrees relative to the intensity of the wastes. But if it were potent enough to be a big hazard I would think more energy could be squeezed out of it. But it is complex since half depleted things may have a dozen different relative characteristics that make it unsuitable for purposes A through M but not N through Z. Or any combination of such.

Some elements when expended are probably suitable for use in a different type of nuclear plant. It may not have the heat required to use it in a large scale plant anymore, but could run a smaller steam engine using a mixture of several chemicals as it's evaporative element. It cannot boil water? No problem if there is a smaller plant capable of using freon instead. (It would have to be radically redesigned to use freon, but this is still quite possible.)

I think the biggest problem with radioactive wastes is simply greed. The plants are built to make money. They are not made to squeeze every last watt/joule of energy out of the radioactives. They could be, but they are not. They are designed "to make a maximal amount of money and we will worry about the wastes in three decades when I retire..." and such.

Making a freon reactor would be easy in reality. But other phase change substances are probably better for reasons I have no insight into. They will not do it because it will not make them money. And here in the USA if a company running a reactor is publicly traded, the executives have a responsibility to make a maximal income for the shareholders or face a possible prison sentence for any of a number of laws that can be brought to bear against them for such a failure. (Some would sue them and claim they avoided making profit to devalue the stock so they could buy it themselves and other such nonsense.)

I hate our laws here in America.

I would gladly pay a premium to buy energy from a company that generates it via "Expended" materials and has efficient salvage energy.

 

My dad is a retired double E (electrical engineer) and he has some veeeery interesting things to say about nuclear power. What it boils down to is, the byproducts of what I believe is called a "second phase" reactor are actually much safer than what you get out of the initial reaction. The thing people in America don't like is you have to get a lot of it in one place to make it go, and some people are oddly worried that other groups of people will steal it and use it in "dirty bombs".

What's odd about that? Well, you can put reactors of both types in one facility, so people could effectively walk waste uranium from the onsite waste storage facility to the second reactor and toss it in periodically, instead of loading it onto trains and shipping them across a continent to a long term storage facility. Which of these is less secure again?

In point of fact, France and, to a lesser extent, most other Western European countries do this. I believe the current stockpile of radioactive waste in France fits in a building smaller than Fort Knox, and its less radioactive to boot. By the time waste storage becomes an issue French nuclear engineers are talking about having a third phase reactor that will produce waste that is practically harmless. While second phase reactors cost a fair amount to build, they let you use your fuel twice, so over the course of a decade or so they actually make power cheaper.

But it's impossible to overhaul our existing reactors or build more due to excessive- Well, this is a physics thread, not a politics thread. But yes, nuclear waste may not really be as much of a storage issue as you are often given to believe. Time will tell.

 

Interesting! Do you know by what mechanism it is slowing down (I ended up looking this up. You can have my whole train of thought, though!)? It is still true that angular momentum is conserved, so if the earth is slowing down, something else must be getting that spin in return. Dust collects on the earth...but the earth is pretty dang heavy, so that does not significantly contribute to anything approaching rapid slowdown...hmm...
This fellow's quick calculations say that the earth loses 50,000 tons of mass a year. His calculations are mercifully in kilograms, so that's 50,000,000 kg a year. The earth is apparently ~5.9742 x 10^24 kg though. So it doesn't lose a large percentage of its mass a year. About 8.3*10^(-16) percent. The classical equation for angular momentum is L = m*v*r (v is the velocity of the particle, r is its radius from the position of rotation). Since the earth isn't a spherical shell, but in fact a solid sphere, we should be using L in terms of a sphere's moment of inertia. I'm going to make the bad approximation that the earth has the same density everywhere.
Shame on me! I forgot the classical expression for L...My guess turned out to be correct...Anyway, L = I w, where I is the moment of inertia, and w is the angular velocity in radians/second ( just v / r, but now we don't have to think about all the individual locations of the particles). I for a sphere is 2/5 m R^2 where R is the radius at the edge of the sphere. So the angular momentum of the earth is :
L = (2/5) w m R^2. Small changes in m result in inversely proportional small changes in w such that L-initial = L-final.

BUT somebody thinks you're right! What's more, measurements have apparently been made using the lunar laser ranging devices we put on the moon in the 60's! I haven't explored much to see if the data has been published anywhere, but the LLR techniques have yielded good results in the past in other areas of science. It looks like the proposed mechanism is the tides. Although direct gravitational forces between the center of masses of the earth and the moon don't torque, the oceans moving with respect to the earth do, in the form of the rising tides. Angular momentum is apparently recovered in the moon, of all things, which also gains some kinetic energy. One of these fellows quoted on the wiki there ( http://en.wikipedia.org/wiki/Tidal_acceleration ) thinks that most of the energy is lost to heat, and only a small portion is transferred to the moon. Never the less, angular momentum is still conserved. This requirement is one way to understand how the moon gains energy from this interaction.

 

Well, I'm not a scientist, so I just basically repeat what I heard.
I don't even understand 1/8 of what you said, to be honest.
Just that last part.
Everything else just shot up over my head, and made my head start hurting.

 

It's like that for most people David, so don't worry about it. I only understand what they are talking about because I spent a lot of time talking about various physics-related things with my physics teacher when I was in high school (and that guy was a real enthusiast, he got his Phd in physics for the sake of getting a Phd in physics, as he already had a job as a physics teacher when he had his master's degree), but I still try not to post anything long there because I'm kind of awed at the whole discussion. Which is good, when you think about it (the part about being awed, the other one varies from person to person).

 

Re: How C-14 can be radioactive:

Edit to add: C-14 is made unstable as it is a product of a proton of N-14 being converted to a neutron, forming C-14. http://en.wikipedia.org/wiki/Radion...s_of_nuclides.2C_.22stable.22_and_radioactive

The only thing that radioactive decay is is basically an atom saying "Hey. Shit. I'm unstable."

Its like (in fact, it's almost exactly like) if you were carrying a shitton of groceries in from the car. You're stumbling around with your arms full of these groceries, when suddenly something falls off. You can carry the rest more easily now, but you've lost some of your groceries .

The C-14 atom has sufficiently many nucleons (protons and neutrons) that it doesn't have as firm a hold on some of its particles as C-12 - the 'standard' carbon isotope. It thus spontaneously decays (a neutron turns into a proton) and it craps out an electron and... I think an electron antineutrino through beta decay. Its basically the same as you and your groceries, except more like making some of your ingredients into a cake, throwing out some leftovers and carrying the rest easily.

Also, the 'heaviness' of an element/atom whatever is absolute crap.
It has mass (which is constant per specific isotope), density (which varies based on conditions), net force of gravity acting on it (dependent on position) - which is weight... And thats about it.

Iodine is definitely, 100% a more massive element than iron - it has 127 nucleons compared to the super pitiful number of like 56 for iron. The thing is, in large scale applications - iron is a metallic lattice. Its got a shitton of iron cations lumped together in a sea of delocalised electrons. It means these particles are bonded super strongly, and really DENSEly. Thus, a 1cmx1cmx1cm lump of iron is more massive than (in standard conditions) the same volume of iodine molecules. BUT - in a dense situation, i.e. in the core of a neutron star, or if you were to decompose all of the molecules of iodine into the component nucleons and reassemble them into a 1x1x1 cube of iron, the masses would be identical.

Also, what is with this crap with "Iron is the last stable element". Lead is the last stable element. Also - the highest atomic number feasible under the non-relativistic bohr model is ~137 - 200 protons is about 60 more than we think is possible.

As the solar system (probably) formed from a rotating accretion disk, it strongly implies that the earth must have always been rotating.
See below for more info.
http://en.wikipedia.org/wiki/History_of_the_Earth#4.6_Ga:_Solar_System

 

Briefly regarding nuclear power: There's radioactive isotopes in coal, burn coal, release isotopes. Uglier scenario than carefully storing your nuclear waste in an underground bunker - assuming you don't reprocess.

 

duh, I forgot that some of the mass while fusing/fissioning is turned to energy. /facepalm
Well there goes my shot at undermining decades of science
I really love this stuff, as you might of surmised by my name.
Speaking of quarks, if you haven't heard the quark song, you should listen to it now. (That's a link)

 

Click "Like" if you clicked to see Giraffe Sex... at the end of that Quark Song. Lol.

*Edit* Ah! No filtering! I love it!