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

Thanks for the spelling correction Hell Nice to see another article from your very self.

While I know brems is not of nulcear origin it is something to be aware of when working with some types of emitter. I just thought it might be interesting to mention it that's all (a footnote would be more than adequate). They certainly made a very big point about it in my radiation safety course when I went through it. It is quite a potential hazard when working with phosphorus-32 particularly as this generates very high energy beta-radiation (a few MeV) that can penetrate a fair old distance in open air. If one shields oneself with lead then bremsstrahlung is generated that is just as dangerous as the initial radiation itself. If one uses perspex shielding itself it's not a problem at all. I think they make a big deal out of it with us biological peeps as P-32 is probably the most common radio-nuclide we use - it is widely used in DNA sequencing.
Anyway, no big deal, it was about the only thing I could see that might be worth including that wasn't already there (at least without getting horribly technical).

Personaly I've only ever used tritium and C-14. I find big hairy spiders more scary then them.

hairy spiders....

True, true. Bremsstrahlung footnote underway.

BTW: Have you never used Uranyl acetate?

Bye Orcus...

Nope, why would anyone want to make or use that? Mind you I guess most would say that about what I use and make in my research

We used Uranyl acetate in the first semester as a wet-analysis for sodium... Anyways, it's been a long time ago. (Oh and Caesium in the Physics course)

Never mind...

Marijn: Including neutron capture I guess would go too far since it's not the atom's own neutron it is capturing. EC though is quite common among lighter Nuclei e.g.: Be-7 -> Li-7.

Intermediate half-life isotopes. I have named long and short ones... I think people can interpolate themselves, including the intermediate ones would make the part on half-lives unnecessarily long. I know it's important since they are in the fall-out dust and all that, but perhaps they should be mentioned an entry about fall-out clouds...

The rest I have adapted.

Thanks a lot for all your comments.

HELL

Hi Hell

interesting article, could have gone way over my scientifically-challenged head but thanks to your clear style and choice of content, it remains eminently readable to the uninitiated. Nice work.

In the hope that you will find this useful, one or two suggestions on the English front:

1st para - "Substances emanating this weird radiation were simply called 'Radio-active'." I don't think 'emanate' can take an object. Substances simply emanate, perhaps from something or somewhere but no substance can emanate 'something'. I would assume this should be 'emitting', as found elsewhere in your article.

Sec 2, 1st para - "There are basically five ways an instable nucleus can react:" 'Instable may be a valid alternative to 'unstable' but is there a difference in meaning? If so, are you being consistent?


Sec 2, 5th para - "The rate at wich those elements undergo nuclear reactions is described by the half-life" - One typo and perhaps 'is described AS the half-life.'

Sec 2, 5th para - "The big problem of nuclear waste is that it is basically a mixed salad of all kinds of radioactive stuff, some taking ages to vanish others radiating like hell." - Minor point, but I think the sense is clearer if you add a comma. ie '... some taking ages to vanish, others radiating like hell.'

Sec 3, 1st para

a) - "The Alpha radiation per se is the most dangerous form of radiation" - I would recommend 'Alpha radiation is the most dangerous..." Per se seems to add nothing here, neither does the definite article.

b) - "will cause a long-term exposition to alpha radiation" - should this be 'exposure'?

c) "have a very high momentum" - Forgive my ignorance, but I don't undersand this term. Could it be briefly explained?

Sec 3, 2nd para - "The beta radiation penetrates things about a centimetre" - Definite article? Also, "penetrates things about a centimetre" sounds odd to me. I understand the intended meaning but it sounds odd. Praps just me!

Sec 3, 3rd para - "Exposition to gamma radiation" - as before, 'exposure'?

Sec 4, "In science radioactivity" - again, this is a small point, but I would recommend a comma after 'science' to avoid ambiguity.

Footnote 4 - "subestimated" - Is this a technical term? If I undersand correctly, I think 'underestimated' would be better here.


Hope this is not too pedantic, and good luck getting your piece edited, it certainly gets my vote for a place in the guide.

Spiff

It should be "cathode rays" rather than "cathodic rays".

Yep... You're absolutely right. I like it when people point out my mistakes, in that way my English gets better - really, thanks a lot.

(I'll do the corrections later, though)

HELL

ps: Momentum is the product of mass and velocity (I thought this is a common concept taught in school, that's why I didn't explain it - is there perhaps a more common word that can be associated with momentum?). Fast massive things do more damage than fast not-so-massive things.

pps: 'per se'... I meant: If the alpha rays weren't so easily blocked they would be a lot more harming.

Inertia is another word for momentum, but it would not be appropriate here. Most people think about something with a lot of inertia as "hard to get moving", rather than "hard to stop".

Maybe you can use kinetic energy instead of momentum, I think the energy-dissipation is more important for the damage than the momentum.

Hi

yeah, they did mention it in physics at some stage (never did concentrate much in Physics, I'm afraid ) and I thought I understood the word. I tend to think of it in the day-to-day context of 'getting up some momentum'.

With my layman's *definition* of what momentum therefore was, I didn't really follow - "since the alpha-particles (He nuclei) have a very high momentum."

Oh yeah, I number among those who think of 'inertia' and 'momentum' as being VERY different things! Sorry

at himself.

Spiff

kinetic energy: Do alpha particles have a higher kinetic energy than gamma-photons?

The problem of kinetic energy is that the velocity goes in squared, so it tends to be more important than the mass. E.g. A car of the mass 1 at a velocity 2 has the same kinetic energy as a lorry of the weight 4 and velocity 0.5. But the momenta are different: Car = 2; Lorry = 4. The lorry will do more damage, in spite of the same energy. (Or am I totally insane?)

I'll do the changes later.

Thanks.

HELL

Maybe changing 'momentum' for 'impulse'?

Whaddaya think?

Impulse is one of those words that nobody can remember exactly what it means. I think you should leave momentum as it is. I was taught about momentum in school at age 15 and didn't have any problem knowing what you were talking about. For those who didn't quite understand it, you should put a footnote.

I think this is a good suggestion Gnomon.

Will be done soon.

Thanks

HELL

You need both, as both energy and momentum are preserved.
The (scalar) energy will tell you what inelastic braking reactions are possible, as they always have a threshold value (ionisation-energy for instance). The (vector) momentum is needed to determine the direction of the reactionproducts.

If the energy is not high enough, only elastic collisions are possible.

For this entry it may be enough just to mention energy instead of momentum, and leave out the details.

Looks like a simulpost.

And Hell, I have on doubts about your sanity.

I think this is a good suggestion Gnomon.

Will be done soon.

Thanks

HELL

Rats! Sorry for the double post...

Marijn: ON DOUBTS ?!?!?!?

Glglglglglglg...

Dadadadad....

Gagagaga....

HELL

Done.

OK now?

Sorry to be so late. I have a couple of things, but they can wait.
Or, if you're tired, I could leave you alone.