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King_Ghidra
19-04-2005, 14:31:30
So lead is very dense but also pretty heavy. Are there any elements/substances out there which have comporable density but without the weight?

Btw i'm definitely not constructing any radiation shielding, this is purely a theoretical question

Cruddy
19-04-2005, 14:33:24
Yes. That same lead would be weightless in space.

Funko
19-04-2005, 14:33:41
Right... basically no, they are related.

An object has a certain mass. The mass is basically the density (mass per unit volume) times the volume.

The weight is the force that gravity exerts on that mass, and is proportional to the mass...

In space lead wouldn't weigh anything though...

MOBIUS
19-04-2005, 14:34:49
And it would weigh less on Mars and the Moon say...:cute:

King_Ghidra
19-04-2005, 14:35:35
I'm looking for answers useful in an earth situation

MOBIUS
19-04-2005, 14:36:32
Well you weren't very specific...:rolleyes:

King_Ghidra
19-04-2005, 14:37:07
wait, did funko say it's the same

so more density will always mean more weight?

Greg W
19-04-2005, 14:37:29
Basically, yes. The reason things are light is because they're less dense. You otoh must be very heavy. ;)

King_Ghidra
19-04-2005, 14:38:43
but uranium is heavier than lead and yet less dense, i was told

Beta1
19-04-2005, 14:39:21
1 L (a 10cmx10cmx10cm) block of uranium will weigh more than the same size block of lead. It is more dense and therefore the same volume contains more mass and is heavier.

1kg of uranium is a smaller lump than 1kg of lead because it is more dense the same mass is smaller.

weight is just mass*gravity.

What on earth are you up to?

Funko
19-04-2005, 14:39:47
Originally posted by King_Ghidra
wait, did funko say it's the same

so more density will always mean more weight?

Basically...

Yes.

But they aren't exactly the same concepts.

density is just a measure of how much 'stuff' there is in a fixed space. If you have a bag it'll get heavier the more you put in the bag, same thing.

Funko
19-04-2005, 14:40:08
Try magnetic fields for radiation shielding that doesn't weigh much...

MOBIUS
19-04-2005, 14:40:10
Originally posted by King_Ghidra
wait, did funko say it's the same

so more density will always mean more weight?

Yes, every element is made from the same basic building blocks therefore if there are more of these same things or they are more tightly bound together, they will be heavier.

Cruddy
19-04-2005, 14:40:13
You are looking for theoretical answers useful in an earth situation...

... how's about this then; huge airship with a skin made of lead. Inside is helium.

Although very massive, with a dense skin, the overall density of the airship is still very low and it would float up.

Cruddy
19-04-2005, 14:41:07
Originally posted by King_Ghidra
but uranium is heavier than lead and yet less dense, i was told

Bollocks. Someone's very mistaken.

MOBIUS
19-04-2005, 14:41:53
Originally posted by Funko
Try magnetic fields for radiation shielding that doesn't weigh much...

Earth is basically a giant magnet, which is part of the reason life is able to survive the sun's rays

King_Ghidra
19-04-2005, 14:42:47
Originally posted by Cruddy
Bollocks. Someone's very mistaken.

aha, ok thank you.

so basically if it wasn't for the rareness of uranium, it would be a better radiation shield than lead

King_Ghidra
19-04-2005, 14:43:10
Originally posted by MOBIUS
Earth is basically a giant magnet, which is part of the reason life is able to survive the sun's rays

cool

Beta1
19-04-2005, 14:44:46
Originally posted by King_Ghidra
aha, ok thank you.

so basically if it wasn't for the rareness of uranium, it would be a better radiation shield than lead

apart from the fact that it is itself radioactive...

Cruddy
19-04-2005, 14:44:57
Originally posted by King_Ghidra
aha, ok thank you.

so basically if it wasn't for the rareness of uranium, it would be a better radiation shield than lead

Uranium is also radioactive, so it's not as simple as that.

Mostly alpha, which is harmless externally. If you get uranium inside your body it can be very toxic.

Greg W
19-04-2005, 14:45:09
Originally posted by King_Ghidra
aha, ok thank you.

so basically if it wasn't for the rareness of uranium, it would be a better radiation shield than lead :hmm:

King_Ghidra
19-04-2005, 14:46:11
:lol: quoted three times in a row!

yes sorry, i mean purely in theoretical terms of its density, obviously it is itself rather radioactive :D

Cruddy
19-04-2005, 14:47:36
Don't forget - 2 different isotypes of uranium, U-235 and U-238. Different half lifes and radioactive properties.

MOBIUS
19-04-2005, 14:47:59
Why do I get the feeling that this is one gigantic 100-0 on K_G's part and the density at issue our answering his questions?:hmm:

Greg W
19-04-2005, 14:48:14
Have you been drinking KG? :hmm:

King_Ghidra
19-04-2005, 14:49:39
Originally posted by MOBIUS
Why do I get the feeling that this is one gigantic 100-0 on K_G's part and the density at issue our answering his questions?:hmm:

no, no, i'm a bit funny on apparently obvious science issues, had a very poor education/didn't pay attention/am a noob

MOBIUS
19-04-2005, 14:49:43
No, should I have been?

Funko
19-04-2005, 14:50:41
The reason dense things make good radiation shields is there is more 'stuff' for the radiation to bash into on the way in.

The problem with using potentially radioactive elements for radiation shielding is that even if you use safe versions bombarding them with radiation can cause them to become radioactive versions.

Gold is a nice stable dense element - but rather expensive.

Cruddy
19-04-2005, 14:52:15
What might be best ; some form of convertor. Something that takes the radiation and converts it into a useful source of energy.

King_Ghidra
19-04-2005, 14:53:41
Originally posted by Funko
The reason dense things make good radiation shields is there is more 'stuff' for the radiation to bash into on the way in.

that was the conversation i was having with my cowie which effectively started this whole line of questioning

Gold is a nice stable dense element - but rather expensive.

aha, excellent suggestion!

protein
19-04-2005, 15:00:16
You are my density.

Gary
19-04-2005, 15:00:22
Who'd have thought it'd take this many posts to get agreement on them being proportional ?

MoSe
19-04-2005, 15:04:24
Originally posted by Beta1
1weight is just mass*gravity.

thus

weight/volume = mass/volume * gravity

that is

specific weight = density * gravity

Funko
19-04-2005, 15:07:44
Originally posted by Gary
Who'd have thought it'd take this many posts to get agreement on them being proportional ?

I said that in the second reply (and only 'cause I typed more than the first reply was I second)

MoSe
19-04-2005, 15:30:05
Originally posted by King_Ghidra
aha, ok thank you.

so basically if it wasn't for the rareness of uranium, it would be a better radiation shield than lead
it would be the leading shield

King_Ghidra
19-04-2005, 15:31:40
oh god

Funko
19-04-2005, 15:31:58
Originally posted by protein
You are my density.
:beer:

Qaj the Fuzzy Love Worm
19-04-2005, 17:35:09
I say, if you can figure out a way to stabilize neutronium at atmospheric pressures, that'd be your best bet for radiation shielding.

Lazarus and the Gimp
19-04-2005, 19:38:23
What about cheese?

BigGameHunter
19-04-2005, 19:39:50
I've called Homeland Security. Sorry.

Lazarus and the Gimp
19-04-2005, 19:43:07
Is cheese banned in the US?

Lurker
19-04-2005, 19:43:33
:lol:

Venom
19-04-2005, 19:50:13
I just read all of this thread and I hate myself for it.

Gary
19-04-2005, 19:54:34
Only cheese eating surrender monkeys

KrazyHorse@home
19-04-2005, 20:16:26
There are reasons other than pure density which affect the shielding properties of materials. Boron, for instance, is ridiculously good neutron absorber despite not having a very high mass density.

Venom
19-04-2005, 20:18:30
That's because Boron puts the radiation to sleep. HARR!

Qaj the Fuzzy Love Worm
19-04-2005, 21:50:35
Speaking of being put to sleep...

BigGameHunter
19-04-2005, 22:58:12
Don't feel bad, K_G...this stuff makes my head hurt too.

Good thing we're charismatically rich and dumb people throw lots of money at us to be so...

Provost Harrison
19-04-2005, 23:07:39
Originally posted by King_Ghidra
So lead is very dense but also pretty heavy. Are there any elements/substances out there which have comporable density but without the weight?

Btw i'm definitely not constructing any radiation shielding, this is purely a theoretical question

I think I see density right here in this post :p

BigGameHunter
19-04-2005, 23:10:54
Like I said...

Provost Harrison
19-04-2005, 23:17:26
It's why liberal arts f**kwits should just leave science well alone :p

BigGameHunter
19-04-2005, 23:19:07
Oh, we did, Mr. Wizard. While you were busy not showering and trembling over the limitless fun of the periodic table of the elements, we were off reading poetry and picking up on girls who actually drank, smoked and had sex!

Provost Harrison
19-04-2005, 23:21:07
Someone has to keep society going while you lot sponge off humanity :p

BigGameHunter
19-04-2005, 23:21:44
Glorious, isn't it?

King_Ghidra
20-04-2005, 09:39:36
Originally posted by Provost Harrison
I think I see density right here in this post :p

yeah, welcome to the thread motherfucker, did we wake you up?

you can slump back in your corner now