Science desk
< June 18	<< May \| June \| Jul >>	June 20 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

June 19

TNT equivalent of antiprotons

I was reading this article which explains that it would take 1x10^11 antiprotons to catalyze fusion in a 3 gram pellet of fusion fuel. So I was curious how dangerous that antimatter would be if containment failed, so I want to calculate the TNT equivalent of that much antimatter. According to this, 1 kilogram of antimatter = 21.5 kilotons of tnt. If there are 7x10^14 antiprotons in 1 nanogram then my calculations say that 1x10^11 antiprotons = 3.07 milligrams of TNT equivalent which shouldn't be too dangerous. Are my calculations correct? If a person was holding 3.07 milligrams of TNT and it exploded, would the person be killed? ScienceApe (talk) 03:44, 19 June 2015 (UTC)[reply]

Your conversion numbers sound wrong - way too low - and in fact, they aren't even the values provided by the source you linked! Double check your math; you did something wrong. Nimur (talk) 06:26, 19 June 2015 (UTC)[reply]

A quick way to remember these numbers is to recall that the Hiroshima bomb released the equivalent energy of about 1 gram of matter. And it was in the neighborhood of 20 kT. So we would be somewhere in the ballpark if it said 21.5 megatons of TNT. (Still off by a factor of 2 or so, though, because a kilogram of antimatter annihilates a kilogram of ordinary matter, meaning you actually release the equivalent of 2 kilograms.) --Trovatore (talk) 06:32, 19 June 2015 (UTC)[reply]

Right, so I just need to double my value. So 1x10^11 antiprotons would annihilate with an equal amount of protons, and release 6.14 milligrams of TNT equivalent. ScienceApe (talk) 10:46, 19 June 2015 (UTC)[reply]

That site gives the 43 kt number for 2 grams (1+1), which is correct: I get 21.47 kt/g. So I get 7.18 mg TNT from 2×10¹¹ proton masses, which is close enough to twice your value. It's 30.1 J, which is trivial: the only danger might be a burn if it were well enough localized. --Tardis (talk) 09:52, 19 June 2015 (UTC)[reply]

I think it is not so trivial. 30 J released in form of ionizing radiation would equal 30 Gray dose if absorbed in kg of matter. The lethal dose for humans is around 6 Gray. If absorbed by the whole body it would give 0.5 Gray dose <-> radiation sickness. Ruslik_Zero 20:14, 19 June 2015 (UTC)[reply]

Yeah, this is why the TNT comparison is misleading. If you blow up that tiny amount of TNT, no, I don't think there's any danger (but I take no responsibility for anyone who tries it). But TNT delivers its energy in quite a different way. The TNT equivalence is somewhat meaningful in the context of a bomb, because much of the destruction is in fact delivered by the overpressure and the shockwave, and TNT can also generate overpressure and shock, and total energy is not a bad predictor of how much of those things happen. But right up next to the high-energy particles, it's a different story. --Trovatore (talk) 20:27, 19 June 2015 (UTC)[reply]

On reflection, I'm not sure anymore that it would be completely safe to detonate 30 J worth of TNT; the bang might be loud enough to be harmful to your ears. I didn't think of that the first time. --Trovatore (talk) 21:46, 19 June 2015 (UTC)[reply]

physics garden

Is a "physics garden" the same thing as a botanical garden. Any differences? --Doug Coldwell (talk) 11:45, 19 June 2015 (UTC)[reply]

Do you mean a physic garden? That is a type of herb garden with medicinal plants.--Shantavira|^{feed me} 11:53, 19 June 2015 (UTC)[reply]

(ec):It's a "physic garden", using the old term for a medical doctor "a doctor of physick", as in the Chelsea Physic Garden, where plants were grown to supply apothecaries. Mikenorton (talk) 11:54, 19 June 2015 (UTC)[reply]

Yes, yes, yes. Ya'all have hit the nail on the head. That does clear it up for me. Thanks!--Doug Coldwell (talk) 11:59, 19 June 2015 (UTC)[reply]

I'm pretty sure the use of physic in this case is the same as in the word physician and not the one in the word physicist, though of course they share the same root; but meaningfully diverged in meaning some time ago. --Jayron 32 14:12, 19 June 2015 (UTC)[reply]

These answers are most useful in my research. Thanks!--Doug Coldwell (talk) 15:19, 19 June 2015 (UTC)[reply]

A physic was also a medicine or drug see [1]. People in the north of England used to say in the early 20th century that there was "physic in the sea", meaning that seawater (and bathing in it) had curative properties (see Wakes week#History). The word comes from Middle English at a time when there was no such thing as a physicist. Richerman (talk) 23:28, 19 June 2015 (UTC)[reply]

Rather, that branch of applied mathematical methodology that we call "physics" today was historically described as "mathematics" or "natural philosophy." It probably did not really become widely known by the name "physics" until very recently, perhaps as recently as the nineteenth century or even the early twentieth century in some circles. (For example, Henry Cavendish was a philosopher and his publications were printed in the Philosophical Transactions of the Royal Society; but the professorship named in his honor at Cambridge was the Cavendish Professor of Physics. Somewhere between there, "physics" evolved out of "philosophy" in common parlance, referring to the exact same subject matter).

There were physicists long before we had a name or English word for them!

Nimur (talk) 05:52, 20 June 2015 (UTC)[reply]

That's what I meant, In the Middle Ages there were Natural philosophers but no Physicists. Richerman (talk) 07:55, 20 June 2015 (UTC)[reply]

Nathan Bailey in his 1731 work "The universal etymological English dictionary, Volume 2" has "Physick (ars physica, L.,φύσις Gr,) in a limited and improper sense, it is applied to the science of medicine; the art of curing diseases; and also the medicines prepared for that purpose" compare "Physick, Physicks (φύσις Gr. nature) natural philosophy or physiology, it is the doctrine of natural bodies, their phenomena, causes and effects; their various affections, notions, operations, etc. or is in general the sciences of all material beings or whatsoever concerns the system of the visible world". Mikenorton (talk) 10:39, 20 June 2015 (UTC)[reply]

A "physics garden" sounds like someone would be growing calculi. ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:30, 20 June 2015 (UTC)[reply]

Why would anyone want to grow Kidney stones ? Richerman (talk) 07:48, 20 June 2015 (UTC)[reply]

Maybe there's a shortage. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:18, 20 June 2015 (UTC)[reply]

They make for nice stepping stones in the Liverpool. StuRat (talk) 23:09, 20 June 2015 (UTC) [reply]

I went around such a garden recently and it had a big section which had a couple of guards beside it and railings around to stop children as the plants were all extremely dangerous ones like belladonna and mandrake - though what they ever used mandrake for in medicine I'm not sure perhaps they added a few more poisonous ones for effect :) That's the sort of thing they used to grind up to give people in the past. Dmcq (talk) 16:26, 21 June 2015 (UTC)[reply]

From mandrake

“

Mandrake has a long history of medicinal use, although superstition has played a large part in the uses to which it has been applied. It is rarely prescribed in modern herbalism.[citation needed]

The root is hallucinogenic and narcotic. In sufficient quantities, it induces a state of unconsciousness and was used as an anaesthetic for surgery in ancient times.[14] In the past, juice from the finely grated root was applied externally to relieve rheumatic pains.[14] It was also used internally to treat melancholy, convulsions, and mania.[14] When taken internally in large doses, however, it is said to excite delirium and madness.[14]

In the past, mandrake was often made into amulets which were believed to bring good fortune, cure sterility, etc. In one superstition, people who pull up this root will be condemned to hell, and the mandrake root would scream as it was pulled from the ground, killing anyone who heard it.[3] Therefore in the past, people have tied the roots to the bodies of animals and then used these animals to pull the roots from the soil.[3]

”

Nil Einne (talk) 22:05, 21 June 2015 (UTC)[reply]

Both belladonna and mandrake are natural and organic. According to the pro-marijuana leaflets that appear on my car every week, it is logically impossible for a natural and organic plant to cause any harm to a human. 199.15.144.250 (talk) 12:00, 22 June 2015 (UTC)[reply]

Careful 199.15.144.250. Your comment is very close to trolling. --Aspro (talk) 18:15, 22 June 2015 (UTC)[reply]