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

http://www.bbc.co.uk/h2g2/guide/A546068

Comments wellcome.

HELL

Right, something I actually know about and can comment on

*Warning, nitpicking post follows*

Para 1: I'll re-write this, if you don't mind...

'Radioactivity' is a term coined by Pierre and Marie Curie, and is used to describe a weird phenomenon that happens with certain substances. Along with improved understanding of atomic structure (at the turn of the 19th century) strange "new kinds" of radiation were being discovered (like cathodic-rays and X-Rays). The physics behind them remained obscure and mysterious. The materials investigated by the Curies emitted radiation similar in character to X-Rays, but generated by an unknown process [1]. Substances emanating this weird radiation were simply called 'Radio-active'. 'Radioactivity' is used to denote the presence of this radiation.

Footnote 1: At the time X-Rays were generated as a by-product of cathodic-rays (protons) acting on certain metals, whereas this strange X-Ray-like radiation did not need to be generated, it simply was found emanating out of certain materials.

(Cathodic-rays, these would be electrons surely?)

Today, 'radioactivity' is a collective term referring to several types of radiation (namely...

"Atomic nuclei are mainly made out of neutrons and protons" - you could probably drop the "mainly". Yes I know that you can make exotica such as muonium, antihydrogen etc., but there isn't a lot of it about

"instable" - should be "unstable".

"He nucleus" - might be better to say Helium nucleus, given this is a general guide and most people are probably not familiar with the atomic symbols. Ditto the other elements mentioned.

"...emmitting a load of neutrons. Which is a process..." - would sound better as "This is a process...".

"...or Potassium 40 (Million years), are very little radioactive..." - I'd re-write this as "are not very radioactive". You could maybe put in a footnote along the lines of "so long as the mass of the lump of material concerned is below the critical mass". Of course, this means that you have to introduce the concept of critical mass at some point...

"All elements have at least one radioactive isotope...". Could maybe mention that 14C is used for carbon dating here.

Neutron radiation - high ionisation potential? I thought neutons were, well, neutral

Looking good so far

Jamie

Yeah but Neutrons can sputter stuff off molecules charging them. Ionizing them.

I'll fix the other stuff tomorrow.

Thanks Jamie for your comments.

Good nicght,

HELL

Ill come back tomorrow then In meantime, I think a bit more info/history about Family Curie is required to do the entry, and indeed their awesome work, justice. Catch you later,
vp

you might want to change the reference to carbon dating into a link to the edited entry at http://www.bbc.co.uk/h2g2/guide/A637418

Thanks jamie again, I have incorporated most of the changes you suggested. The "'mainly' made out of protons and neutrons" part I intend to leave as it is for the giggle-factor.

I am not thinking about including the concept of critical mass here. The reason: This entry is about radioactivity, not on nuclear reactions or decays or radioactive elements - of course some parts overlap, but the critical mass is not necessary to explain radioactivity.

Neutrons and Ionizing: See my first reply.

Vogonpoet: Yeah - I too love bios and the Curies have an interisting one. A Biography on Marie Curie (and Pierre) is currently underway, but on a separate entry. I'll include a short footnote in this one.

Xy: Link - of course - included.

Thanks for your comments.

HELL

Hell, there are a few places where your English is not quite right. I know you won't mind me pointing them out. Some of them were already pointed out by Jamie, but I'll mention them again.

"By the time the advances on the atomic structure were being made" - this just doesn't sound right. Try "When atomic structure was first being investigated"

on the turn of the 19th century --> at the turn of the 19th century

physics behind that --> physics behind them

similar to the by then known X-Rays --> similar to the recently discovered X-Rays

"1:1 to 1,5:1" would be better phrased as "between 1:1 and 1.5:1"
(note the comma is not correct)

is called the alpha decay" --> is called alpha decay

is called the beta decay --> is called beta decay

anti-neutrino), this --> anti-neutrino). This

emmitting --> emitting

The alpha radiation --> Alpha radiation
The beta radiation --> Beta radiation
The gamma radiation --> Gamma radiation
The neutron radiation --> Neutron radiation

with wich --> at which

high half-life --> long half-life

radiating like hell). --> radiating like hell.

about a cm --> about a centimetre

medicinal diagnosis --> medical diagnosis

nucler power --> nuclear power

comming --> coming

emanating out of --> emanating from

disaggragate --> disaggregate

Well done, Hell!

Uff... Thanks Gnomon. I should have read it through another fifty times... But then again... Why bother if there's always some vigilant Gnomon in the PR that will do the dirty work for me? Just kidding...

Thanks a lot, typos and mistakes will be corrected ASAP.

HELL

Done.

Nobody else interested in Radioactivity?

Good article, ready for the Edited Guide. Complete, compact and well structured.

Two minor things:

Link to A476723 and A639425 (Power Plant and DNA fingerprintig). You mention both in your text.

Electrons, not protons were/are used to generate X-rays by shooting them on metal.


Personal problems, maybe because I'm too stupid:

'Nowadays the gamma-rays are generated in other safer ways.' You needn't tell in the article, but I'm curious: which ways?

'Neutron-Radiation [...] combines long range penetration and high ionization potentials' -- this is not consistent. Either they interact heavily or not with the penetrated matter. If they fly through me without hitting me (often), how can they be dangerous?

I don't understand the last sentence. Which 'other' uses?

Scouts, pick it!

Good article

Might add Electron Capture (EC) to the list of decay mechanisms for sake of completeness.

Nice article . But what about positron emission?

OK.. OK.. OK..

EC and positron decay included for the sake of completeness. I originally left it out because they are not the most known, and I was afraid that it could confuse a lay-reader. But I agree... What's the point of an entry on Radioactivity if it is not complete (at least to some extent)?

Cefpret: You can very effectively generate X-Rays by shooting protons at a metal plate too... But I'm afraid you are right: historically electrons were there first (hence I adapted the footnote, thank you). With this we come to the 'generated in safer ways' part you were asking about. Some X-Ray machines had a Caesium or Radium chamber made out of lead which had a hole that was eventually opened when the radiogram had to be taken. The problem is the security of that chamber - many leak, and the usual waste problem. Nowadays gamma-radiation is generated by the same good old colliding stuff against metal plates method. It is a bit more expensive and needs a lot of electricity, but it can be dosed better and only switched on when needed. And - of course - no nuclear waste.

Neutrons: Neutrons have a mass comparable to that of the alpha particles (roughly 1/4 of the mass). On the other hand they are much smaller (i.e. they penetrate your skin better). Common fast neutrons from the fission process are not really the biggest problem. The biggest problem is when they get moderated (e.g. by water - remember human body = 3/4 water) and slowed down. Slow neutrons are very reactive (This is also the reason why the critical mass is substantially reduced in water).

Bye,

HELL

Ahh, now some things got clearer.

However, the sentence 'Nowadays the gamma-rays are generated in other safer ways' should be directly after 'For this reason cancer radiotherapy is still a valuable tool in medicine', because in radiography you still need radioactive substances, don't you?

And I still don't understand the last sentence of your article. Waste from other uses than power plants?

Oh yes, sorry, I was going to get into that too, but somehow I forgot... Must be the neutrons...

Yes, I meant the waste arising from other uses than power plants.

People forget that there is also this other nuclear waste which can be quite substantial. It is not as dangerous as power plant waste, but still it can do some lots of environmental mess.

And yes, you're right, I'll put the sentence on the correct place.

Thanks Cefpret,

HELL

OOps no.. sorry... the other way round.

You still need radioactive elements for diagnosis and for some forms of cancer therapy.

The safer modern ways you use for radiography.

Clear? OK then... Thanks.

HELL

Would mentioning Brehmstraalung (braking) radiation be appropriate? If one works with a high energy beta-emitter such as P-32 (which penetrates way more than a centimeter by the way - but i guess you are being general) then one must be wary of this as you can generate X-ray brehmstraalung instead of your beta-particles if the wrong type sheilding is used.
Just a thought.

Other than that - nice article

OK... The correct spelling though is Bremsstrahlung (thought you might wanta know...).

I'll figure out a way to include the bremsstrahlung.

Nice seeing you here Orc's.

Bye,

HELL

Hi Hell, a nice entry.
Even after the other comments, I can add some also.
In atomic nuclei you say: 'There are basically three ways an instable nucleus can react:' followed by five methods. I am not sure about electron capture, whether it should count as radioactivity. In that case you might also count neutroncapture creating an unstable atom.

In the section with half-lives, you might mention a few elements with intermediate half-lives of 20 to 50 years like Cesium, Strontium or Cobalt, as these are normally the most dangerous in fallout.

I would not say alpha radiation is the most dangerous per se. It only is dangerous if it is created within your body. From outside it cannot even pass your skin.
Next to Alpha and Beta you may also put gamma and neutron in bold.
Also some reasoning why neutron radiation has such a long range (it has to hit a very small nucleus, without influence of electromagnetic attraction or repulsion).

maybe an extra anecdote: for building laboratories where radiation is studied, long searches are made to find sand, clay and stone with as few natural radiation as possible, as the natural radiation can otherwise be more intense the the radiation to be studied!

Some extra I find when checking again. You keep saying 'emmittor', but on the other hand it is 'emission'. Should it be 'emittor'?.

Keep up the good work!
Marijn

Well, brems-radiation has only very marginally to do with radioactivity. Radioactive radiation is defined by its origin, not its wavelength. And here brems-radiation is something totally different.

Since an Edited Guide entry should be concise, I recommend to leave that out. You may mention the term itself in the second footnote.

Question to Orcus: This 'radioactively generated' brems-radiation may be measurable, but is it so much? I know that in usual cathodic x-ray emitters the cooling system is very big, as is the voltage to accelerate the electrons, because efficiency is pathetic. But I like to learn though...