Is everything radioactive?

Factual Questions
1

I just read in a current thread about what would happen if the Earth were water. The subject of the magnetic field of such an Aqua-planet came up, and although iron would not be at the planet’s core a very weak field might be set up with a core of a particular phase (right word?) of ice.

My query is huh?. I have learned a out Banana Equivalent dosages, using as a baseline the amount of radiation a banana’s potassium emits. So that gives potassium, iron, and all the scary trans- Uranic elements. But hydrogen and oxygen?

I clearly don’t understand radiation. But I’m aware in a rough way of alpha, beta, gamma and higher, as well as ionizing and non-ionizing.

But do all God’s chillun got emanations?

2

All elements have radioactive isotopes, some have only radioactive isotopes, but for the ones where there are both radioactive and stable isotopes the rates between isotopes vary. Hydrogen for instance has protium (the regular stuff), deuterium and tritium, which make up 99.985%, 0.015% and trace amounts of your average amount of hydrogen. Potassium is mostly made up of K-39 and K-41 which are stable, but also has 0.012% K-40, which is radioactive..

3

OK, maybe I’m not all awake yet, but what’s the connection between the first part (magnetic field of water planet) and the second part (radioactivity of water) of your question?

4

Except for the hypothesis that nucleons (neutrons and protons) break down given sufficient gazillions of years to do so, no, everything is not radioactive. True, every element has radioactive isotopes, but most elements as they occur in nature do not – their radioactive isotopes are too short-lived to have survived. Only carbon-14 and tritium, formed in the upper atmosphere by the impact of cosmic radiation on CO[sub]2[/sub] and water vapor, plus the intermediate steps in the breakdown chains of the metastable nuclides, are common short-lived nuclides.

Among relatively common elements other than carbon and hydrogen, only potassium-40 and rubidium-87 are reasonably metastable isotopes. There may be trace amounts of other radioactive nuclides in the common elements lower on the periodic table, but the operative phrase there is “trace amounts.”

Indium is an interesting exception to this rule, but the story here is interesting. Indium is present in two isotopes, -115 and -117. One is completely stable and comprises 4% pf present indium deposits; the other isotope (96% of the whole) is metastable, radioactive but with a half-life 50,000 times the age of the Universe, and thus barely noticeable as radioactive.

Every nucllide more massive than Lead-207 is radioactive, but descends from one of three metastable nuclides: Thorium-232, Uranium-235, and Uranium-238. (Bismuth-209 and Lead-208 are also metastable, to the point they were until recently considered non-radioactive, completely stable.) Of those three metastable isotopes, U-238 has a half-life just about the present age of the Earth (50% of the original amount left),Th-232 has a half-life of about 10 billion years (75-80% left), and U-235 has a half-life of just under a billion years, meaning only about 4% of the original amount is left. The various isotopes between U-238 and lead occur in relatively small amounts, as their natural (rapid) breakdown is counterbalanced by their slow, steady production by breakdown of the metastable elements. Also small traces of Np-239 and Pu-239 are present from the beta-decay of U-239 when U-238 is impacted by a neutron and does not break down in consequence – a rare but extant phenomenon.

Traces of the metastable isotopes, however, are present in the environment, e.g., in granite and in soils resulting from its breakdown (and the bricks made from them). This is why radon detection is so important in well-insulated areas.

5

I guess the OP is connecting the need for radioactive decay in the Earth’s core to maintain a liquid core - and thus allow the creation of a magnetic field, versus a cold solid core, and no flow.

Problem with radioactive decay and water is that you don’t have a lot of time. Tritium has a half life of 12 years, and the most long lived unstable isotope of oxygen has a half life of 2 minutes. Even if you started out with a planet made entirely of radioactive isotopes of hydrogen and oxygen, you are not going to have a hot core now.

Does every element have unstable isotopes? Well yes. Does every element have extant unstable isotopes naturally? Depends. Keep a glass of water shielded from cosmic radiation for long enough and all the tritium in it will decay, the unstable oxygen (if there were any) will also have long since gone, and you will have a glass of non-radioactive water. Long enough is, well a very long time, since half life is only a halving in content, and you will need a lot of halving to reasonably expect to get every last atom of tritium.

Some isotopes have short half lives, some longer, some are theoretically unstable but have never been observed to decay, some have half lives that exceed the life of the universe by a large margin, some are theoretically as stable as you like. The trouble with short lives is hat by now, they should have vanished. But you can make unstable isotopes either by radioactive decay from other elements, or by slamming a neutron (or more) into the nucleus, something cosmic radiation does. So there are processes that could constantly replenish the shorter lived isotopes of many elements. One suspects that for pedantic purposes, one could say that most elements have some extant unstable isotopes present on Earth. However for many, the amount will be inconceivably small.

6

First, thank you to all.

I just got this image of things just fading away like the Cheshire Cat, or like a speeded up film (which exists) of a plate of fruit being completely consumed by unseen bacteria.
The magician fills a glass of water and puts fruit on a plate. Then, Presto!, pulls back the curtain to reveal they’re empty. But would the glass and plate vanish first?

Which leads me to another question. Something half-lives, radiates itself, away. The energy it “possesses” (mc^2) is transformed with no loss? The weak, strong forces and their real, honest to goodness amounts? Something’s got to give, right? Entropy and all that?

You are correct, in that I skipped a stage or three.* And I know I was not all that awake when I posted.

*An all-too common skipping process, sadly apparent in many of my posts. And conversations, which makes people look at me funny sometimes.

7

Energy is always transformed without loss, if you consider all forms of energy. Sometimes some energy ends up transformed into a form that you’d really rather it didn’t, and you can consider that “loss”, but the energy is still there.

8

As Polycarp above says, absent proton decay, there are absolutely stable elements, which the best magician can’t make vanish. But there are some strong theoretical reasons to expect that protons aren’t absolutely stable: the possibility of their decay is a prediction of most grand unified theories, i.e. most theories that aim to unify the electromagnetic, weak and strong forces into one (‘electrostrong’) force. The reason for this is the such theories contain additional force carrying particles (bosons) which can mediate proton decay (in the same way electroweak unification—the unification of electromagnetic and weak forces—introduced the neutral Z boson, which however can’t mediate mediate particle changes; those are taken care of by the W[sup]+/-[/sup] bosons, which for instance mediate beta decay).

However, experimentally, there are now very strong constraints on the proton’s half life, on the order of 10[sup]33[/sup] years (which rules out some, but not all GUT proposals)—thus, if there is proton decay, while the magician’s trick would become possible, it would require a very patient audience.

9

So, since we’re getting silly here, my body, surrounded by a leaded-crystal casket which is shielded from cosmic rays, and whose water content is hydrogen and non-isotope water, would, before poof-ing out into radiation, ultimately be just before then a pile of lead and protons?

To get even more stupid, you could figure out the order in which body organs would disappear.

10

This is either nonsense or wrong.

11

Welcome to my world.

And i can’t andwer because your choices seems to be equal.

12

“The Earth is a perfect sphere” is wrong.
“The Earth is custard shaped” is (most likely) nonsense.

13

Most of the matter of your body is made up of isotopes that are presumed stable, and so the best guess of the best theories we have available to us is that they will never decay, and will remain in that box forever (though they’ll surely go through some unpleasant chemical changes in fairly short order). Trace amounts of your body are unstable isotopes; they’ll mostly decay into stable isotopes of comparable mass, much lighter than lead. If, as some untested models predict, the proton itself is unstable, then eventually all of the elements we consider “stable” will decay, and the mass of your body (and that of the box containing it) will, over an inconceivably long time, eventually decay into a mixture of photons and neutrinos. The photons will mostly be absorbed by the lead box, and give up their energy into heat which will leak out, while the neutrinos will almost all just ignore the lead box entirely and fly off into the distance.

14

If an individual proton has a half-life of 10^33 years, will the half-life of a proton in a stable atom, e.g. Helium or Iron, be about the same, or significantly longer?

15

The half-life may well be different, but we don’t have enough information to say whether it’d be shorter or longer, nor by how much.

16

This is just such a fucking cool answer. Thank you Chronos.

  1. But just to check: the lead box would stay a lead box?

  2. Didn’t (some) physicists’ alarm bells go off when the idea of infinite (permanence) in physical form is posited–as I read you–with !unstable protons?

  3. Neutrinos never die/vanish/cease to exist? Never run out of steam, so to speak?
    [FWIW, I think that if the protons don’t decay, in your post you might say the body is “incorruptible.” So all it has to do is rise up, and like the Book says, it’s Miller Time.]

17

No, that’d go, too.

They’re forever, as are electrons and photons (as far as we know).

18

That is true, but it is important to mention that much of your body is made out of carbon, and while most of that carbon is the stable isotope of C12, there is also C13 and C14 present. C13 is also stable, but C14 is not. Even though it is not stable, C14 is produced naturally (as Polycarp mentioned upthread), so in all living things a mix of the various isotopes of carbon will be present.

Once you die and get sealed into a box, the C14 is going to decay. By measuring the amount of C14 relative to the rest of the carbon, you can tell roughly how long something has been dead. If you have ever heard the term “carbon dating” this is what they were talking about.

19

Yeah, that (among a few others) is what I meant when I said “Trace amounts of your body are unstable isotopes; they’ll mostly decay into stable isotopes of comparable mass, much lighter than lead.”. Carbon 14, for instance, decays into the presumed-stable nitrogen 14.

And Leo, I would not say that the body is incorruptible, because as mentioned, chemical reactions will still occur. Wait a while, and you’ll have a disgusting sludge instead of a body (though still composed of carbon, hydrogen, oxygen, etc.).

20

I’m not sure why this should set off alarm bells. Protons can still be changed to other things in a number of ways. Anti-protons turn them into photons. Gravity can smash then down into neutrons or even into black-hole-stuff (which is poorly defined, but you’re not getting any protons back out of a black hole).

Protons aren’t unique, either. I’m pretty sure electrons, photons and neutrinos are stable in the same way.