Talk:Orders of magnitude (mass)

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Contents 1 Critical density 2 Significant digits 3 GeV to g 4 dosages 5 Systematic Error 6 Other mass pages 7 Why merge? 8 Hydrogen mass 9 Observable universe masses 10 Big Ben 11 add masses

[edit] Critical density

This says that the mass of the observable Universe is greater than the mass of a critical density Universe. Yet the universe is thought to be flat or open, which implies a total universal mass of less than the critical mass, yes?

As far as I've understood it, the Chandrasekhar limit is supposed to be 3 times the mass of the sun, although here it says that the sun weighs 2 times something, and the Chandrasekhar limit is 3 times the same something (i.e. 1.5 times the mass of the sun). Which is correct? --Dolda2000 04:51, 1 Dec 2004 (UTC)

See Chandrasekhar limit, about 1.4 times the mass of the sun. — QuantumEleven | (talk) 14:22, 23 March 2006 (UTC)

[edit] Significant digits

I think that many of the numbers in this table are far too precisely stated, and that it is easy to lose sight of the forest for the trees. They are an annoying destraction which keeps people from seeing the overall picture which this table is intended to present.

Links are included to most of the examples given (and if not, it most likely isn't a precise number in any case). Let the people interested in that number follow the link for more information; reserve this for what it is supposed to show.

I'd say no more than 3 significant digits would work for most of these numbers (maybe 4 or even 5 on rare occasions; e.g., if that results in an exact number (not a measured quantity)).

Various, unharmonized methods of showing approximateness could also then be thrown out, with perhaps a subheading in the caption about the numbers not being precise.

Along the same lines, other than in the first column there should be no scientific notation except at the extremes of the table. Gene Nygaard 12:39, 17 Dec 2004 (UTC)

I think it is convenient to have the accurate values where applicable. The overall picture is clear from the vertical position in the table.--Patrick 00:04, Dec 18, 2004 (UTC)

Gene is right. This article is about relationships, not about individual masses. Maximum precision is definitely distracting and can be given elsewhere—that's what links are for, Patrick! Accordingly, I have improved several entries for better readability.
—Herbee 23:28, August 3, 2005 (UTC)

[edit] GeV to g

would it be possible to have an explanation for the sub-atomic particles' mass being expressed in GeV, either as a footnote, asterisk or a link? It took me a long time to figure out that it was an expression of energy and I think it would be good to inform younger/less informed readers as to the convention. Matithyahu 19:42, 18 Dec 2004 (UTC)

[edit] dosages

Do we really need all the drug and lethal dosage examples? "1.5×10−11 kg: Lethal dose of botulin toxin"; "10−7 kg: "Hit" of LSD (100 micrograms)"; "2×10−7 kg: Lethal dose of ricin (200 micrograms)"; "1–3×10−5 kg: Dose of DXM per labeling on most products (10-30 milligrams)"; "3×10−4 kg: Hallucinogenic dose for mescaline (0.3 grams)" etc.

I ask not because I'm a prude, but because

1. It looks like some high school kid's joke, and unprofessional
2. It's pointless. You can't say "x is about the weight of the hallucinogenic doe of mescaline", whereas saying "x is about the weight of an elephant" makes perfect sense.

— Asbestos | Talk (RFC) 17:00, 31 January 2006 (UTC)

Was hoping someone else would have noticed this. I got suspicious of the drug mob invading this page when it read 'mass of caffeine molecule', and things didn't get much better later on. I completely agree with Asbestos, I'm in favour of replacing / removing some examples. 87.212.128.62 18:05, 12 June 2006 (UTC)

The LSD example should be kept, because it's a drug with an unusually low active dose, but the other drug examples are uninteresting. --4hodmt 13:04, 21 July 2006 (UTC)

That is an interesting property of LSD and should be mentioned in its article. It does not, however, help make the item good for giving the reader a feel for the mass order of magnitude, which is what this article is about. Henning Makholm 19:47, 21 July 2006 (UTC)

[edit] Systematic Error

There is i chance of misleading in the article. I think each prefix-instance (e.g. 10E-3, 10E-6, 10E-9, etc.) should have a unit and i suggest gram (g) after it. I know the SI unit is kg, but you cant have a combination of prefixes, like kmg for kilomilligram. Therefore, the most logical appending unit should be g.

/Björn Brian

No, that's not logical. The only legal base unit is the kilogram. --Heron 21:40, 20 February 2006 (UTC)

[edit] Other mass pages

There are individual order of magnitude mass pages e.g. 1 E2 kg and 1 E-27 kg. Doesn't this page cover all of them already? Shouldn't they be merged with this, or removed? --PhiJ 18:02, 20 March 2006 (UTC)

Exactly what I was thinking... —Doug Bell ^{talk•contrib} 18:10, 20 March 2006 (UTC)

[edit] Why merge?

Why were the individual mass pages merged here? Certain articles used them to provide a means of comparing objects of similar mass, but now one is led to the top of this page, and the reader needs to scroll down. I didn't find any discussion of the reason. Alternatively, could this article's table be adapted to use section headers so that redirects could at least link to the right part of the table? Yet another alternative might have been to make the indicudual mass pages templates and transclude them here. -213.219.186.138 19:23, 16 April 2006 (UTC)

I proposed it above, and then nobody disagreed, so it got done. Interestingly enough, the opposite consensus was agreed on Talk:Orders of magnitude (length). Maybe they should be the same, and it should be remade. Anybody disagree? --PhiJ 16:50, 24 April 2006 (UTC)

No disagreeement. And yes please undo the merge or remake the pages somehow. I'm the same anon as above BTW, only the IP changed. -213.219.184.105 22:50, 14 May 2006 (UTC)

Yes, please undo merger. --mav

[edit] Hydrogen mass

The article says "1.674×10−27 kg Hydrogen atom, the lightest atom 1.675×10−27 kg Neutron (939.6 MeV/c²)." How can a neutron weigh more than hydrogen, that doesn't make any sense. - PiMaster3 19:35, 21 April 2006 (UTC)

A neutron is actually very slightly heavyer than a proton. A hydrogen atom contains a proton and an electron, which weighs practically nothing compared to a proton, so the mass of an electron, added to the mass of a proton is less than the mass of a neutron. --PhiJ 18:56, 22 April 2006 (UTC)

[edit] Observable universe masses

I've removed both of the universe masses because they don't seem to make any sense. For one, they aren't well defined at all. It isn't clear whether mass should be taken to mean the mass of baryonic matter or the mass of all matter. Or is it something like Ωρ_critV_observable, which really doesn't make too much sense for Lambda-CDM? I assume that the "mass of the critical density universe" refers to the observable universe, with Ω_mat = 1 and Ω_vac = 0, otherwise we can just alter the vacuum energy density and get whatever we want with Ω_total = 1. But even ignoring these problems, it seems that the mass of the observable universe given, when compared to the mass of the critical density universe given, must result in Ω ending up much larger than 1 - it seems that it results in it being more like 2.

If you want to add these back, you should clearly define what the values are, and add either reliable (and recent!) sources for the values, or calculate the values in the Observable universe article, which shouldn't be too hard. On the other hand, I may just be rambling incoherently, and I really should go to sleep. --Philosophus ^T 10:36, 21 July 2006 (UTC)

I think it does have some encyclopedic value to have a ballpark estimate of the "largest meaningful mass", to use in conversations like "Let's sift the ocean for plutonium that formed spontaneously in the water by quantum tunnelling, and build a bomb!" - "Dude, that would need (calculate, calculate, find comparison value in encyclopedia) ... sifting significantly more seawater than the mass of the entire universe". For such purposes one does not need very precise numbers. It could be labeled "Baryonic matter known to exist in the observable universe" if you would prefer at least to have a precise-sounding definition. Henning Makholm 11:09, 21 July 2006 (UTC)

That is somewhat what I am saying. I will probably add it within the next 24 hours, but am not in a state to do so right now. Order of magnitude figures are great, and are somewhat the point of this article, but they need to make sense, and not create issues like this. To do this correctly, I will add justification to the Observable universe page as well. --Philosophus ^T 12:13, 21 July 2006 (UTC)

[edit] Big Ben

I have changed "Bell of Big Ben" to "Big Ben (Bell)," as Big Ben is the name of the bell, not the tower.

[edit] add masses

Put some weak particles in: axions, Goldstone bosons, etc. -lysdexia