Fiction Science #2: Element 121

A BRIEFER HISTORY OF TIME

(in memoriam: Stephen Hawking)

(The full version of this introduction can be found in my first Fiction Science post)

 

SOME BACKGROUND

I originally got the idea for doing this from Halo Conversationalists. While they broke down each entry into the Halo Universe, they stumbled upon some questions regarding the feasibility of certain events that occurred, and I took it upon myself to answer to the best of my knowledge.  Different science questions have come up, including the first Fiction Science, the Planet of Blue and Red (Halo: Broken Circle), Biofoam (Halo 3: ODST), and this one, the feasibility of Element 121 (Halo: Nightfall). I do make a point to give as much leeway to the fiction, so long as it does not directly contradict with science, since this is, you know, fiction.  And I will do the same with other topics going forward.

THE KISS OF DEATH

So as this is a blog discussing both a fictional universe (Halo), and real science, there will inevitably be a point when the subject matter may get overly technical and complicated.  In that light, I will make a point to Keep is Simple, Stupid. My goal is to balance simplicity with technical correctness.  If I ever skew too far in either direction, I hope the readers will let me know so that I can fix it.  

KNOW WHAT YOU KNOW

As I did in my Tin Foil Halo series, I am providing this disclaimer that I may spoil some aspects of different Halo games, books, or comics.  These spoilers should be minor, but if you want to catch up with your Haloing before you read this, I have provided links to any Halo media that might get spoiled.

 

RELATED MEDIA (POTENTIAL SPOILERS)

 

THE QUESTION

COULD THE ELEMENT THAT WAS USED TO KILL HUMANS ON SEDRA, ELEMENT 121, EXIST, AND COULD THE RADIATION PULSE THAT IT CAUSED ACTUALLY HAPPEN?

This question was first asked on Halo Conversationalists Episode 45, and answered on Episode 50.

 

THE ANSWER

To answer this question, I am going to have to break it down into a few sub-parts, which will go into some of the background associated with elements and their creation.  Hopefully breaking it down this way will make it easy for people to skip the parts they already know, and jump straight to the parts they might need a little refresher on.

I have broken up the question into the following sub-questions:

  1. What makes up an atom?
  2. What is an element?
  3. What are isotopes?
  4. How do fusion and fission work?
  5. Where does binding energy come from?
  6. How do stars work?
  7. How are elements formed?
  8. What is the Island of Stability?
  9. So what is the scenario, exactly?
  10. Could Element 121 actually exist?
  11. Could the radiation pulse that killed people on Sedra actually happen?

Well there is no time like the present to get started on this, so here we go!

  Bohr's model  of the atom. The electron (blue) orbiting the nucleus (red).   (figure 1)     By Kurzon (Own work) CC BY-SA 3.0

Bohr's model of the atom. The electron (blue) orbiting the nucleus (red). (figure 1)

By Kurzon (Own work) CC BY-SA 3.0

1. WHAT MAKES UP AN ATOM?

The atom consists of 3 particles, a proton, an electron, and a neutron. The proton has a positive electrical charge, the electron has a negative electrical charge, and the neutron has no charge.  It is an oversimplification, but the neutron is effectively what you get if you smashed a proton and an electron together.  A little heavier than a proton, and no charge.  The middle of the atom, the nucleus, consists of protons and neutrons, and the outside of the atom, the electron shell, consists of the electrons which orbit around the nucleus.  Again, it is an oversimplification, but imagine the electrons orbiting the nucleus like the planets orbit the Sun.

 

2. WHAT IS AN ELEMENT?

Every element in the universe (hydrogen, helium, oxygen, etc.) has a unique number of protons in their nucleus.  Adding or removing protons from one element will turn it into another element.  Adding or removing electrons from the element do NOT change which element it is, but does change the charge of the element.  This difference in charge is primarily what drives chemical reactions.  Realize, that while chemistry can make all sorts of amazing chemicals, it does not change elements from one to another.  If you combine two hydrogen atoms and one oxygen atom together, you get H2O, or water, but the elements that make up the water molecule are still the same.

 

The periodic table.  Each element represents a nucleus with a unique number of protons, corresponding with the table number. (figure 2)

 

 

3. WHAT ARE ISOTOPES?

This is a term you may have heard in regards to nuclear power or weapons, but there are isotopes of every element, not just uranium and plutonium.

While changing the number of protons in the nucleus changed which element we were referring to, and changing the number of electrons changed the charge of that atom, changing the number of neutrons in the nucleus change which isotope of that element we now have.  The chemical properties of an element are mostly unchanged by adding or removing neutrons, which is why we don't say the element has changed, but its nuclear properties can change drastically.

The chart of the nuclides, shaded by half-life.  Dark red corresponds with more stable (less radioactive).  The stable isotopes generally follow a straight line, though the completely stable elements end at #82 (lead). (figure 3)

For instance, hydrogen.  It is the most abundant element in the universe, and normally consists of one proton, one electron, and no neutrons.  The regular hydrogen atom is stable, which is to say it is not radioactive.  If you add a neutron to the nucleus of a normal hydrogen atom, you get H2, or deuterium.  It is still hydrogen, still will bond with oxygen to make water (albeit with a slightly different bond angle), but it is heavier.  Significantly.  Like twice as heavy.  Heavy water, which is water made of deuterium instead of normal hydrogen, is about 10% heavier.

If you add another neutron to the nucleus of a deuterium atom, you get tritium.  Tritium is even heavier than deuterium, but more importantly, it is an unstable nucleus, making it radioactive.  Radioactive isotopes are those that do not have a good balance of protons and neutrons in their nucleus.  The process of radioactive decay makes the nucleus more stable, but also emits radiation, and usually turns the isotope into another element altogether.

As an analogy, think of a ball at the bottom of a hill.  Every time you add a neutron to  a stable nucleus, it is like pushing that ball a little bit up the hill.  Just a little and friction will keep the ball from rolling back down.  Keep pushing the ball, and eventually the ball will overcome that friction and roll back down to the bottom of the hill.  Every element has one or a couple stable configurations.  After that, the element will become radioactive and decay until it gets back to a stable configuration.

 

4. HOW DO FUSION AND FISSION WORK?

Now that we have established some basics about the atomic nucleus and the different ways to alter their properties, we get to the more important question of 'how do you actually add or subtract protons and neutrons from a nucleus?'.  And to answer that question, we will briefly explore how the universe does it.

The most basic element, which I mentioned earlier, is the hydrogen atom.  It has only one proton, and no neutrons.  On the opposite side of the spectrum, natural uranium consists of ninety-two protons, and 146 neutrons.  Both can be used to generate energy, but they use slightly different means to get there.  These are called fission in the case of uranium, and fusion in the case of hydrogen.

It turns out, that while almost every element between hydrogen and lead (with the exception of technetium), have stable isotopes, some are lower energy than others (think the ball and the hill again).  If you take two hydrogen nuclei (one proton each) and smash them together hard enough, you will create a helium nucleus (two protons).  But because the helium nucleus is more stable (needs less energy to hold the nucleus together), the resulting atom will actually have slightly LESS MASS than the two hydrogen nuclei did together.  Of course conservation of mass dictates that you cannot create or destroy matter/energy, so that mass has to go somewhere.  Where does it go?  It literally is converted into energy via the mass-energy equivalence equation, most commonly known as E=mc^2.  This is how energy is generated via fusion, and how stars generate so much energy.

 Binding energy chart.  Left to right is number of protons (which element), and up and down is how much binding energy there is (how tightly bound).  Moving up on the curve results in net positive energy.  Iron (Fe and Nickel (Ni) sit at the top of the curve.   (figure 4)

Binding energy chart.  Left to right is number of protons (which element), and up and down is how much binding energy there is (how tightly bound).  Moving up on the curve results in net positive energy.  Iron (Fe and Nickel (Ni) sit at the top of the curve. (figure 4)

On the other side of the spectrum, uranium will do something similar.  If a neutron is fired into the center of a uranium nucleus, there is a chance it will break in half, and become two lighter elements, known as daughter products.  Those two lighter nuclei will be more tightly bound than the uranium nucleus, and again using E=mc^2, the end result is net positive energy.  This is the process of fission, and is how energy is generated in nuclear power plants today.

 

5. WHERE DOES BINDING ENERGY COME FROM?

But why, when you fuse two hydrogen atoms together, do you get energy, and when you split two uranium atoms apart, do you also get energy?  This is because there is a "most stable" configuration (again, ball and hill).  This configuration is right around where iron and nickel are on the chart of the nuclides (figure 4).  The nuclei of these atoms are as tightly bound as possible.  Adding or removing a proton would actually make the nucleus less stable.

Why there specifically?  Without getting too technical, it is just a balance of forces.  There is a force, called the nuclear force, that wants to pull protons and neutrons together.  It is incredibly strong, but only works over very very small distances.  Then there is the electromagnetic force.  It wants to push all the positively charged protons away from each other.  It is also strong, but not quite as much.  But it works over a little bit longer distance, so once you have enough protons together, the electromagnetic force actually becomes stronger than the nuclear force.  

As another analogy, think of a magnet and gravity.  At close distances, a magnet is stronger than gravity.  But gravity works over much longer distances.  So if you had a magnet holding up a small metal ball, the electromagnetic force wins.  But keep attaching metal balls to each other, and eventually gravity will win out.  Binding energy is the same concept, just on a much smaller scale.

 

6. HOW DO STARS WORK?

At this point I hope I have made some sense of where we get energy from in fission and fusion reactions.  Now we will start to tackle the original question.  Or at least some background on that question.  Namely, where do all the elements we see come from?  And the simple answer to that is stars.  Effectively every single element, with the exception of hydrogen, was made in the heart of a former star.  We will really quickly go through that process, and the process of generating the higher mass elements, like element 121. 

To start very simply, if you press two hydrogen atoms together hard enough, they will fuse together to make helium.  Like unimaginably hard.  But it can be done, and it is done all the time in stars.  Gravity wants to pull everything together, and in the case of a star, is pulling an incredible amount of hydrogen together.  As it gets more and more dense, those hydrogen atoms are getting closer and closer and hitting each other more and more.  The more they hit each other, the hotter they get.  And the hotter they get, the faster they are moving.

Again, as an analogy, imagine one of those cans of air.  If you just hold down the button to spray our the compressed air, the can gets colder.  The energy per atom stays the same, but there are less atoms in the can now, so the energy density goes down.  It's like that, but in reverse.

So if you have enough hydrogen in the same place, like you do in a star, it will get to a point where the center will get smashed together enough and the atoms moving fast enough, that they will fuse together and make helium.  And that reaction makes energy, like I mentioned before.  And that energy means faster moving atoms.  And faster moving atoms means more fusion reactions.  And more fusion reactions means more energy.  And so on and so on.  This is a chain reaction.  This is the birth of a star.  This is fusion energy.

So the star reaches a balance.  In the center it is generating incredible amounts of energy which wants to push the atoms away from each other.  But there is all this matter that is being pulled together by gravity.  So it reaches an equilibrium, where the force of gravity pulling in equals the force of fusion pushing out.  This is what dictates the size of a star.

 

7. HOW ARE ELEMENTS FORMED?

So as the star continues to burn, it is fusing hydrogen into more and more helium.  Eventually, there will be enough helium that it will start to fuse.  But like we saw in the binding energy chart (figure 4), the nucleus of helium is more stable, and needs more energy in order to fuse and make heavier elements.  So the core has to be denser and hotter to fuse the helium.  Now that equilibrium changes a bit.  The energy from fusion goes up, but the energy from gravity stays the same.  So the star starts to swell. 

The layers of a late-stage star, prior to collapse and supernova. (figure 5)

By User:Rursus (R. J. Hall) [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0]

And this continues as the star keeps burning up its fuel.  Every new fuel needs to burn hotter to keep going, which means the core is denser, but the rest of the star gets less dense and swells.  But if the core is denser and hotter, is is also burning through its fuel faster.  Each new fusion cycle, from hydrogen, to helium, to carbon, and so on, burn hotter and faster, meaning each subsequent cycle is shorter.  For a star like our sun, it swells out until it absorbs most of the inner planets.  This is the red giant phase.  But our sun doesn't have enough mass and therefore gravity to keep the reaction going forever.  Eventually our sun will burn out and shrink down into a white dwarf, which isn't generating any energy anymore, but just sitting as a very hot, slowly cooling point in the universe.

For much larger stars, there is enough gravity to keep the cycle going.  Two hydrogen atoms become helium.  Three helium atoms become carbon, a carbon and helium atom become oxygen.  This process will just keep going, hotter and hotter, denser and denser, faster and faster.  Until iron.  Once the core burns up everything else and all you have left is iron, the fusion reaction actually results in less energy than before.  Remember, before, the star was a balance of gravity and fusion energy.  Now the fusion energy is gone.  Not only that, but the fusion reaction actually absorbs more energy than it took to make it.  The star RAPIDLY compresses.  All that mass just starts to fall into the center, and there is nothing to stop it.  Well nothing except the electromagnetic force.  All those protons don't want to be that close to each other, and the star explodes out, which is what a supernova is.

But where do all the elements heavier than iron come from?  Well to put it simply, there is just so much mass being compressed together at the moment of a supernova, that even elements that don't generate any energy get fused together.  This doesn't last long, but it is long enough to create all the elements higher than #26 to exist.  And once the star explodes, all those elements get blown out into the rest of the universe.

 

8. WHAT IS THE ISLAND OF STABILITY?

So stepping back for a minute, take a look again at the chart of the nuclides (figure 3).  Notice how after element 82, there is a gap of no stable elements, then a small 'island' of more stable elements?  Well basically, it is theorized that there is another 'island of stability' around element 120-130.  That is not to say those elements are totally stable, but are more stable than those a little lighter.  We aren't sure it exists, but it is assumed to based on theories and equations.  That's it.  It isn't some magical place where super heavy elements are completely stable, just a place where some elements might exist long enough (like milliseconds) to be able to study some of their properties.  You know what makes us confident element 121 isn't stable?  We have never observed it in nature.  If it was stable, it would probably exist in small quantities somewhere.  But as far as we can tell, it doesn't.

 

9. SO WHAT IS THE SCENARIO EXACTLY?

Ok, so the original question is whether element 121 could exist.  But the real scenario is as follows:

The wildcat destabilization of the Pillar of Autumn's reactors caused a supernova-like event, generating elements heavier than iron, all the way up to element 121.  How that would work I have no idea, but this is science fiction, so I'll give the UNSC engineers credit that they have been able to design a fusion reactor that can fuse everything up to and including iron together, making the reactor go supernova.  Maybe it uses slipspace.  Who knows, its the future.  And to be honest, is a pretty cool explanation of how they managed to blow up an entire Halo with a single ship.

And this leads us to.....

 

10. COULD ELEMENT 121 ACTUALLY EXIST? (not gonna happen)

So yes, element 121 could, and likely does exist, though there is really no feasible way it could last for more than a few milliseconds.  But lets say that the half-life of element 121 is a few minutes, which would be pretty incredible.  This would mean that by the time Locke got to the Halo in 2556, four years later, it would all be gone, decayed away.  The half-life would have to be in the several years for the element to still be around by the time of the events on Nightfall, which doesn't sound that absurd, but would require a significant change in theoretical physics to work.  It is just incredibly unlikely.  Like pretty much no chance.

But this is a fairly minor thing to overlook, and I wouldn't really bat an eye at it, except for the final question:

 

11. COULD THE RADIATION PULSE THAT KILLED PEOPLE ON SEDRA ACTUALLY HAPPEN? (really not gonna happen)

To put it bluntly, NO.  Without going into all the background on radiation and all the types, there are four basic types: Alpha, Beta, Neutron, and electromagnetic.  Each is a little different, but they are all basically either higher or lower energy.  That's really it.  There is no known radiation that will only kill specific humans with specific DNA.  Radiation just isn't selective like that.  I can't even think of something that might make even the tiniest bit of sense.  Why didn’t they just say they found some weird Forerunner weapon? That would have made infinitely more sense.  Sorry, but this is just totally absurd.  Possibly the most absurd thing that has ever happened in the Halo universe.

 

SUMMMARY

My summary of this plot device is 'why?'.  It is obvious they had some nugget of information about the Island of Stability or something like that, but then they just ran with it, and not in a good way.  I mean, as stupid as saying they found some Forerunner device that only kills select humans, at least that makes sense from a universe perspective.  And the Forerunners were so advanced you can always chalk up anything they did as "Forerunner magic".  But no, this is a Halo movie, and the producers probably said "No one is going to know what is going on if there isn't a Halo somewhere in here".  So they come up with this contrived plot device that makes no sense, but frankly, who cares, because it wasn't executed well to begin with.  

Yea, so sorry about the rant; back to the science.  Is element 121 an actual thing?  Yes.  Could it really exist on Installation 04?  No.  Could it, or any element, cause some radiation pulse that kills people, but only select people, and over great distances?  Definitely not.  Sorry about the extremely long set up for this one, but I hope this was at least informative.

Actually, I think I might have come up with a pretty interesting idea for how a wildcat destabilization would work.  I'm going to have to think about that one more, but so far it sounds just plausible enough to work, and it fits the given data.  

If you have any questions regarding this analysis, or maybe think of something that I didn't, let me know, and we can discuss.  Who knows, I could very well be wrong.  I always like a good challenge.

 

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