entropydave

...seems that the moderator has sensibly removed the remarkably stupid posting that was made by "ass_pirate30" whoever he is....

thanks Mod!

...good answer!

Yup, still no input!

...and I thought you chaps had some answers.....!

Hi,

I did have a piece of shareware that allowed one to simulate galaxy collisions - for the life of me I can't find it now!

I do have one called "galaxy32.exe" but it is 10 years old and not the one I was using....

It was freeware BTW.

If anyone knows of the s/ware (or equivalent) can you please let me know?

thanks

dave

well, this must be a veryunpopular topic or question! No responses at all!

Gravity is faster than light if you consider black holes where light/photons doesn't even escape. Contrary to popular believe gravity is the fastest thing in our universe' date=' not light. An inference from the experiment is that causality is not universally true, and a good arguement for free will.

 

"we see the world as we assume it exists" ...Bohr[/quote']

 

good point - remember, the universe is NOT a perfect vacuum, therefore c will be lower than the defined physical value - I cannot say how that impacts on the propagation of gravity.

I went to a lecture yesterday given by Prof Bernard Pagel on neutrinos and we briefly touched on young galaxies, notable 1 Zwicky 47 which is around 500 million years old and he remarked that the metallicity of the stars were pretty much zero - I briefly discussed with him that I cannot accept that there were huge blobs of primordial matter, from the Big Bang, that was still unseeded by elements higher than Li. He agreed that this was a mystery and that maybe there was some other answers, like all that we see are very large, very old white stars mixed in with small amounts of 2nd & 3rd gen stars.

I cannot see how a large and very old white star could remain on the HR diagram without long ago supernovaing or cooling to form neutron stars or whatever....

Any ideas? Because he sure didn't!

the world may never know.... seriously, I am only 13, I havent learned about this yet. Can you explain? And don't use baby words. i'm NOT a baby. I am as intelligent as a 26 year old man

Oh, well that's ok then... please note, not a "25 year old man", or "a 27 year old man" (or indeed woman) but a "26 year old man"

...sounds like the sort of thing a 13 year old would say!

well, if u aske me id say theres one type of iron- Fe element. Are the "two types of iron" iron compounds or iron mixed with something?

Taenite is high in nickel, (>10% or so) Kamacite is lower in nickel - or the other way around!

i need nitric acid to etch a meteorite (iron)

ferric chloride is just as good - degrease a polished slice, use a swab of cotton wool to apply the ferric chloride and then rinse v. thoroughly with deionised water, then a rinse in 95% isoprop, then a gently bake at about 110- 120 deg c.

That'll work nicely!

Thanks jdurg! Trouble is, I would have definately inhaled the thorium oxide - I remember the white powder on my specs! There was a cloud of white dust because the silly beggar shook it up and then puffed it...

crap.

never even thought about getting it checked.... that's all I bloody need!

good advice - I think I should take it.

your friend[/i'] did this? cancer isnt fun and games, man. how long ago was this?

...well, not a friend exactly, but we are talking about a fellow classmate - remember it clearly - would have been about 1976/77. One would gently squeeze the washbottle and the Rn gas would be puffed out.... I don't smoke and I don't have any coughs or bronchial problems....yet.

Should I raise this long-ago event with my GP? I have been dealing with precancerous colonic polyps for 3 or 4 years ("drug and scrape"...)

...I just recalled an incident that happened when I was at school, about 30 years ago or so.... we used to have a Radon generator which was a plastic wash bottle with a load of Thorium oxide (or some white, thoriated powder, presumably Thorium oxide). You left it to accumulate Radon gas and would use in certain practicals in physics. I remember my friend shakking it up and puffing the boody thing in my face - I must have inhaled a cloud of this stuff.... thank heavens for Health & Safety regs, eh?

A friend dragged me into his shed a few weeks ago. His grandfather used to paint Rolexes with RaCl2 containing paint. Surprise, surprise, he pulled out some lead sheet. Inside there was a vial containing approx. 5g of the stuff. I don't have a calibrated detector on me, but he wants me to have it. OK, I'm a sensible chemist and serious element collector, but what would you do with the stuff?

I'd melt it and electrolyse it and get some pure metallic Ra....(I know I know, it's mixed with ZnS....!)

Yep, I have just measured it from behind - gold is a pretty effective absorber of gamma and it is about 0.5 - 0.75microSv/hr.

Judging by the link given above - I think that sitting on a granite bench is more of a problem! Especially to one 'nads!!

I measured thru the glass - no beta and a little gamma will escape...!

Hi everyone, just a query about my ol' 1940s gold Ebel wristwatch.... not, I know they used radium salts for the luminous hands,but I am surprised to see it measures at 15 microSv/hr.....

I presume that's normal, Just wanted to see what you all thought!

You can't turn a neutron into a proton by hitting it with a photon.

 

You can do it by hitting it with an positron though. The positron could emit a virtual W-boson (and turn into a neutrino) which is absorbed by a down-quark in the nuetron turning it into an up-quark. Since the neutron is udd and the proton is uud' date=' this turns the neutron into a proton.[/quote']

 

Thanks! that's a great answer - I suspected that it would not be possible use a photon to convert a neutron into a proton, but I just wanted confirmation.

Blimey, there's some bright sparks on this forum!!!

Good stuff!

Hi,

...was just pondering the endlife of a neutron star.... presuming they rapidly rotate, and that they will absorb ISM and emit radiation, what happens in the long term with these stars? Do they evaporate or grow due to ISM dust collection?

I also wondered whether or not the absorption of a photon onto a neutron would/could change it into a proton, and if so, what energy photon would do that?

You'd think I'd have better things to think about, n'est pas?

h2so4' date=' that isnt true; think of schrodinger's cat.

 

half-life of 210 At is actually 2 minutes. if you get an active enough alpha source you can produce enough of it to see; it's black. in fact, researchers have produced enough to perform some tests on it.[/quote']

... I found "Astatine's most stable isotope, astatine-210, has a half-life of 8.1 hours" at http://education.jlab.org/itselemental/ele085.html

 

I am amazed - I didn't think that there was anything morethan a few nanograms in the Earths crust at any one time.... but I guess if you sythesize it, there's no real limit to the amount you could make... never thought abut that.....

Did you also notice how the Curies died from their radiation poisoning? I'm also pretty certain that the health of their 'friends' after being exposed to the eerie glow didn't turn out so well.

 

If you're thinking about getting pure radium metal' date=' you can't unless you have a license. One gram of the stuff is INTENSELY radioactive in terms of disintegration rate and energy emitted during the decay. As a result, massive NRC and other licenses are required to obtain a sample of the pure metal. In the watch hands, microgram quantities of radium are used. Fleetingly small amounts are enough to make the watch glow for centuries.[/quote']

not only that, they had nasty non-healing burns on them from holdingthis stuff in their pockets.

But, I am not aware that Mme Curie died specifically of radiation poisoning - she lived (I think) to about 75 and died of kidney issues - no doubt not helped and brought on by radiation and by heavy metal ingestion, but not specifically from radiation poisoning. But I do stand to be corrected on this, of course...! I know that their notebooks are still inaccessible due to their contamination and will be like that for about 25,000 years....!

 

No, I know that pure Ra is VERY nasty and not a hope of getting a milligram of RaCl for example - but who'd want that around..... imagine dropping on the floor!

Isn't Promethium self-fissile at quantities >3mg? Pretty horrible (but fascinating) too!!!

 

Dammit! Who wants to be immortal anyway? MAybe I should buy a bunch of old watch hands, macerate them in water, and do some fractional distillation on the stuff. My wife, kids and cats would really appreciate that!!

 

In order to get nuclei of that weight, you need to fuse very large atoms together. A star only produces atoms of any appreciable weight when it is collapsing into a supernova. So I am fairly confident that even in the far reaches of space, elements >115 don't exist.

Yep, as a astrophysics student I concur. Even if they had short 1/2 lives, I suspect we'd detect the daughter nuclei?

cesium would actually burn your flesh off in a few seconds

Yeah, wouldn't it? Jeez, nasty but beautiful.... like some women I knew!

...I'd like to get some Ra but not a bunch of watch hands from the 1940s!!! Any ideas?

I like the way the Curies had test tubes full of polonium salts and soem fluorescent stuff (a Zn compound?) and would entertain their guests with the 'eerie glow'.

In fact, wouldn't mind some Po, but the spark plugs that had it as part of their contacts (ionized the air so it would 'spark' easier was the logic) have all now decayed to daughter products....!