h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

well i think the real question should be what is the purpose of radiation ?

That's like asking what is the meaning of life, the universe, and everything.

Radiation exists as part of the universe and how it works. If you mean what's the purpose behind human beings messing around with radioactive materials and things, then I think the answers are rather obvious (energy and weapons are two) as well as more subtle, such as medical purposes, and more purposes having to do with how we observe and attempt to understand the deeper secrets of the universe.

= JD

Also, life originated in a radioactive environment. It is possible that if there was no radiation there would be no life.
(This is the precept behind the idea of 'radiation hormesis' which argues that radiation in low doses is actually beneficial). I might write an Entry on this at some point)

Of course I have a few silly questions that were sparked from trying to understand this entry. I was hopeing I could be lazy and just ask(as opposed to traditional reasearch). It was a great entry, you have a good sense of humor and it makes some what boring stuff a bit easier to read.

-So do all (1 through 103) atoms have a set half life?

-Is raditaion somewhat like a decompisition by-product?

-What do atoms decompose/change into? (ie: Do specific atoms always
change the same way into the same thing at the same time(half life)?

-If we know how/when an atoms "dies" do we know how they are "born"?
(ie: Is there a fianite number of atoms,can new atoms be created, do we know how their created)


If this makes no sense at all I can possibly reword.

Those aren't silly questions at all! I'm flattered you ask them, as some of them are quite a bit outside of my own knowledge ... but let's have a look at 'em ...

"-So do all (1 through 103) atoms have a set half life?"
Not quite. Only atoms that are unstable have a half-life, and by that I mean atoms that will decay spontaneously (without being hit, or "bombarded," by some other energetic particle or photon). What might be confusing is that there are radioactive isotopes of "normal" stable elements. For example, potassium has radioactive isotopes, but the "normal" potassium (potassium-39) is not radioactive and will not spontaneously decay (unless you bombard it with something, but let's not get into that). There are some isotopes of potassium that are radioactive and will decay spontaneously, some more than others. For example, you'd have to wait a while to get potassium-40 to finally get up and go ... it's half life happens to be about 1.3 x 10^9 years (that's 1.3 billion years, if you mean billion like we do in the USA). By contrast, potassium-42 has never been accused of over-staying its welcome, and has a half life of just 12.36 hours. So, the short answer is that not all elements in the entire periodic chart (that is, elements 1-103) have half lives, but nearly every one of those elements has an isotope that is radioactive and has a half life. Many elements have isotopes found naturally that are unstable and will decay over some period of time, while some elements do not have stable isotopes at all and are quite rare (or are made in a nuclear reactor). Makes about as much sense as a screen door on a submarine, doesn't it? This is why nuclear engineers are often fond of a good now and again.

"-Is raditaion somewhat like a decompisition by-product?"
That's surely one way to think of it. I'm not really sure what the proper physics way of thinking about it is, but that sounds like you're getting the fact that radiation is a result of radioactive decomposition (or rather, radioactive decay is the term used).

"-What do atoms decompose/change into? (ie: Do specific atoms always
change the same way into the same thing at the same time(half life)?"
They change into other elements, and sometimes into isotopes of the same original element, depending on how the decay happens. These new atoms are called "daughters" or "daughter products" - a term you may have heard before. Frequently the daughter products are radioactive themselves (sometimes much more so than their parents), and may even be so short-lived that they essentially decay instantly into yet another daughter, and so on until something more stable finally is made. (Anyone who has many daughters might appreciate the irony of the phrase, "stable daughter" as well as the appropriateness of how long it takes and how destructive it might be to get to one ... just kidding, of course).

Depending on the type of decay (i.e. the type of "radiation"), partciles are "radiated out" or ejected from the atom as it decays - these are either alpha, beta, gamma, neutron. Check out this article - A661727 - for more on that. By the way, specific radioactive isotopes do not always decay into the same thing(s), but have probabilities associated with how they decay (there may be more or less of one thing or another, or there may be more energetic examples of one thing versus another). This stuff also depends on the environment the isotope is in, such as how much and how many other radioactive isotopes are in the same environment, including those ever-increasing daughters that would make even Topol lose faith with God at the prospect of marrying them off. (I hope someone gets that joke - think about a movie/musical from back in the early 70s).

"-If we know how/when an atoms "dies" do we know how they are "born"?
(ie: Is there a fianite number of atoms,can new atoms be created, do we know how their created)"
Whew. Not sure I can tackle that one. I'm not sure I understand your phrasing, atoms "dying" and "being born" and their "creation" - but it seems to get to the heart of Einstein's famous equation that relates mass and energy. That's E=mc^2 of course, but the meaning of it is rather more significant. Since thermodynmics tells us that energy can neither be created nor destroyed, that might imply that mass can neither be created nor destroyed (just changed into energy) - that's as far as my logic takes me with that. To be quite honest with you, this gets way out of my field very quickly - you'd have to ask someone else more knowledgeable about this part of physics than I, as to whether there is a finite amount of mass/energy in the universe (I think this is the current cosmological theory). All I can tell you is that we can tell when atoms change into other atoms (either through decay, fission, fusion, transmutation) or when they're destroyed (as in matter/antimatter collisions) because they always give off some form of energy through radiation when they do. I *think* there are some exceptions to this having to do with subatomic arrangements and physical isomerism (there's another term for it I can't remember), but that might be just something I barely remember reading about in some journal a year or so back.

Thanks for the stimulating questions! Hope my answers help somewhat!

- JD

I appreciate your time and enthiuseam. Rest assured I'm always a pain in the..neck, it's nothing persional.

-So when the "reaction" takes place the element is forever changed, and many of those new atomic structures can have a LONG half life, so why shouldn't they be clasified as well. If there is a great probability that(for example) A primariarly turns into B, and B is readily found in a "natural" state, shouldn't B get a spot on the table, I mean if it's got a half life of ~4 million years....? Dose this mean there are all kinds of rouge unclasified atoms lurking around. Great!

-I got the joke, nice anology.

For now, even though were close to proof, standard physics are the rules and theoritical physics(super string, M, membrane...) are yet to count as factual. I was more interested in knowing if,since they can smash atoms and watch, if they can see atoms..come together<?>. Apparnetly the answer is no.

"-So when the "reaction" takes place the element is forever changed, and many of those new atomic structures can have a LONG half life, so why shouldn't they be clasified as well."

They are! All the atoms that are formed when something decays are "classified" - that is they all have names, I'm not sure I follow what you're saying here. We already know about virtually all the isotopes that can be and are formed when another isotope decays (one can't say "all" without risking being proven wrong eventually, but for practical purposes here it's OK I think). If one knows how the decay occurs, as in whether the parent atom lost two protons and two neutrons (alpha decay), then one knows what the new element is (likewise for decays involving an electron or positron (beta decay), or just a neutron). One can use a special chart called the chart of the nuclides to see what the daughter product is called. Actually, one doesn't even need this chart - nuclear physics will tell you what it will be.

Here's an example ... Radium is found naturally in Uranium ores, and is part of what we call the "decay series" of Uranium-238, which is naturally occurring in our Earth. Radium is itself radioactive (it was discovered and first isolated in 1898 by Marie and Pierre Curie). Radium-226 decays into Radon-222, which is in turn also radioactive and is responsible, in many cases, for causing lung and other cancers in specific homes and areas of the world where Radon-222 is prevalent (due to natural Uranium-238 found in the Earth). Both Radium and Radon are on the periodic charts, and one can see that they both have the isotopes I mentioned as their masses on the perdiodic chart (it so happens that the two I mentioned are the most stable isotopes of both elements). Here's the nuclear reaction (this won't look too great without a fixed-width font, I'm afraid):

226 222 4
Ra ---> Rn + He
88 86 2

In English, that means that Radium-226 decays into Radon-222 with the release of an alpha particle (which is equivalent to a Helium nucleus, minus electrons). You can see that the numbers up top all add up to be the same on both sides of the arrow, as well as on the bottom. FYI, the top number is the mass number (the mass of the atom) and the bottom number is the atomic number (the number of protons in the nucleus of the atom). So, this is turning into a nuclear chemistry lecture, but the bottom line is that all those elements that are part of a decay series are indeed on the periodic chart, though that particular isotope may not be (that's the difference between the information the periodic chart contains and the information the chart of the isotopes contains).

"A primariarly turns into B, and B is readily found in a "natural" state, shouldn't B get a spot on the table, I mean if it's got a half life of ~4 million years....? Dose this mean there are all kinds of rouge unclasified atoms lurking around. Great!"

Well, B does have a spot on the table; indeed B has a spot on the perdiodic table *and* the table of the isotopes. The afore-mentioned chart of the isotopes tracks things differently, by isotope and not element - therefore, there are many elements repeated on the chart of the isotopes, each one different from the other from a nuclear/atomic viewpoint, but chemically identical to each other (for most properties). I hope this is clearing it up for you, but I fear I might be confusing it more.

"I was more interested in knowing if,since they can smash atoms and watch, if they can see atoms..come together<?>. Apparnetly the answer is no."

If you want to see atoms coming together (fusing), put on some welder's glasses or other very dark stuff and look at the Sun! That's fusion right there. Actually, one probably should not look directly at the Sun.


- JD

There is a very good EG Entry on 'Radioactivity' (including it's uses) (at A661727)..

I was just getting the impression that all the elements with a known half life go through multiple changes....I was thinking the chart should be alot bigger if that's the case.

Looks like I'm doin reaserch after all.

The chart of the isotopes is huge. The full version will cover most of a wall, or a large chalkboard.

- JD

I was starting to think I might have lost my mind.

OK well that may be the case, but, it dosen't apply to this thread.