Talk:Weightlessness

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[edit] Why do you provide inaccurate information?

At low altitudes gravity decreases by 78 ppb per meter, centrifugal force increases by 157 ppb per meter, so jointly they give the change of -234 ppb per meter, which is -0.7 ppm per 3 meters. 83.4.250.70 21:23, 1 August 2007 (UTC)

[edit] Suggested Microgravity experiements

A similar variant to the NASA's Vomit Comet Program is the ESA's A300 Zero-G Program.--ConradKilroy 16:30, 25 June 2006 (UTC)


The concept of weightlessness in an orbiting spacecraft is well explained and understood. One point which seems to be missed in this article is as follows: Does an astronaut experience weightlessness when the spacecraft is travelling in a straight line under its own inertia from the earth towards the moon? I shall be grateful if someone can throw light on this query. -- Dadakr 00:39, 17 December 2005 (UTC)

I thought that when using SI units it was unnecesary to put in these constants as the system is designed around them --sodium

SI doesn't eliminate the constant in this case. It does for F=ma, for instance (this is F=kma in other unit systems) but not for F=k/r^2. In this case k=-G M1 M2, where G is 'big G', the gravitational constant, and M1 and M2 are the masses of the gravitating bodies. -- DrBob

How does a wood block experience anything? -phma

Presumably it does so in ways that only another wood block could understand.

You are obviously taking an analogy (i.e. the woodblock) too seriously. This means that you are either very slow and stupid, or else you are so logical that the concept of metaphor is simply beyond the comprehension of your over-developed brain.

It would be preferable if you would avoid personal attacks in this forum. Especially when you can't manage to add your own signature. — RJH 17:53, 13 Apr 2005 (UTC)
Actually, I support Overlord359's comment. phma was being a jackass.

"Lesser symptoms [of weightlessness] include... weight loss...." You don't say! I know it's pedantic, but would "body-mass loss" or something be less stupid-sounding? 143.252.80.110 19:53, 4 January 2006 (UTC)

[edit] Hot air

How does hot or warm air from a heater or any other source of heat behave in a spaceship experiencing zero gravity?--Light current 03:05, 26 February 2006 (UTC)

Convection is the transfer of heat by mixing and flowing currents. Free Convection doesn't happen in microgravity, since there's no gravity to pull cold air, which is denser and less bouyant, down and get the currents moving. However, most heaters have fans that help them draw in and recirculate air (forced convection), so they'd probably continue to work, though not as well as they would on the ground.
Conduction is the direct transfer of heat when two molecules bump into eachother. Conduction does work in microgravity, but the one-molecule-at-a-time transfer of heat away from the source is much less efficient than convection, so heat builds up in the air around the heat source. You can get superheated pockets of air that way, which are a hazard space agencies have to be concerned about.
As an example, a lot of computer cooling systems work partly by free convection and have to be redesigned so the computers don't melt themselves. Corvi 00:12, 7 March 2006 (UTC)

[edit] proposal to rename Vomit Comet to Reduced gravity aircraft

There is a proposal to rename Vomit Comet to Reduced gravity aircraft.
Please comment at Talk:Vomit Comet. --Jtir 20:58, 29 October 2006 (UTC)

[edit] Criticism of the terms "Zero Gravity" and "Microgravity"

this section should be deleted, or greatly reduced/altered —Preceding unsigned comment added by 192.211.25.9 (talk)

You did delete this section, at 00:10, November 29, 2006, along with some other sections like "European Space Agency A-300 Zero-G". I'm restoring most of those changes. I agree that the "Criticism" section is too long and could make its point with fewer words. However, I think the criticism is valid -- "zero gravity" is a misleading term. I don't agree with completely deleting the section on the ESA program. Let's continue to discuss here. --Jdlh | Talk 20:17, 29 November 2006 (UTC)

Sorry about the ESA deletion, it was unintentional. The point in Criticism is valid, but I think it should be more of a footnote. As it stands, it is the lengthiest section of this article. The explanation sounds very original, and the editor used way too many "quotation marks" in my opinion. It reads like a rant. "For a weightless astronaut to say that they are in zero gravity is the same type of error as saying that an object that has a length of 0.3048 meters is identically one human foot in flesh and blood." should be removed. The editor makes the same point in each paragraph, which sounds redundant. The last paragraph should be removed. All in all, this section just doesn't sound encyclopedic. Just my opinion.

I agree, it does need to go. Not only is it too long, it offers no citations and sounds like all original research. While the criticisms do seem valid, it seems it is nothing more than one person's point of view. Kelvinator 21:33, 10 December 2006 (UTC)

This entire section is uncited, and without a citation it violates WP:NOR. If anyone wants it back in, please provide citations. Sethie 18:56, 25 December 2006 (UTC)

I am the one who added that Criticism section. I fail to see how anything I wrote qualifies as original research. The whole section was to point people back to the accuracy of very old research. My comments were based on the nature of gravity and acceleration that were published in 1687 by Isaac Newton. The reference is his Principia. The section talks about well proven knowledge that is over 300 years old. And I don't see anything new in discussing orbiting objects either. Newton's Principia discussed how the Moon orbits the Earth. The physical principles are the same. If the Moon were somehow stopped in its track, it would come crashing straight down into the Earth. Newton was well aware of this. I post it to Wikipedia and somehow it is seen as Original Research. I hope you can see that the entire section is essentially an explanation of Newton's ideas about gravity and acceleration. And a different way of explaining someone else's research does not in itself constitute new research. As for anyone who may still hold that the section was original, I offer this quote from the WP:NOR page:
"The original motivation for the NOR policy was to prevent people with personal theories attempting to use Wikipedia to draw attention to their ideas."
In contrast to this, the section at issue had the intent of drawing attention to the well-published and well-tested ideas of Isaac Newton.
There have been other complaints about the section also:
- It is too long,
- It is redundant, with the same point being made in each paragraph,
- Way too many quotation marks are used,
- It doesn't sound encyclopedic / it reads like a rant,
- It has no citations.
The length has a specific purpose in that most people hold misconceptions about weightlessness and this section strives to clear up such misunderstandings. That is not as easy a task as learning something from scratch. Added to this is that the topic is about an environment that people don't typically experience. They often have a lot of difficulty relating to it. Therefore much of the section length is spent in reframing the issue into situations that people CAN relate to, such as riding an elevator or watching an airplane fly.
As to redundancy, I agree that the point can be made with much fewer words. Ideally, the section would not be needed at all because there would be no misconception about weightlessness being "zero-gravity". But that is the very problem. There is a HUGE misconception. NASA itself promotes these erroneous views. To delete the section is to perpetuate the error. But Wikipedia serves to help us with the receding of the veil of ignorance. Newton did a huge effort toward that end back in the 1600's. My effort was simply to point back to a little piece of what Newton taught us, and what some of us have forgotten.
Quotations are used around terms that are being criticized as erroneous. Think of it as a quarantine of viral memes.
As to criticism that it doesn't sound encyclopedic, I am open to any and all improvements to the section. Particularly with any perception that "it reads like a rant".
Finally, the issue about citations has already been addressed with WP:NOR response above. Now if anyone would like to add the reference to Newton's Principia, I have no objection. But it is all just basic physics that is typically taught in late high school / early college.
I would like to see the section added back in, unless anyone has a substantial rebuttal to my response here.
Tdadamemd 23:54, 4 January 2007 (UTC)


Actually you haven't addressed the citations issue, you just.... ignored it.
Find a source which says, "Zero gravity/microgravity/weightlessness is an innacurate term," that will solve everything real quick.
I don't believe you can. I believe you are taking a bunch of different facts, which you could most certainly provide citations for, and then YOU are making all sorts of connections and conclusions between them. It's really, really simple- find a source that says exactly what you want to say, or leave it out. Sethie 01:02, 5 January 2007 (UTC)
Tdadamemd, thanks for your interest in this article and your contributions to Wikipedia. I share your criticism of how NASA and others use the term "zero gravity", but I think that Sethie is correct in saying that what we need is a published, verifiable source that makes that criticism. Then I'd support summarising the criticism that source makes, and citing that source. What you had here sounds like it was your own words, published here for the first time. That is what I think of as original research which the Wikipedia has a policy against. Does that make sense? --Jdlh | Talk 21:34, 5 January 2007 (UTC)
My God! Sometimes I am such a hard-ass. Great post Jdlh- you said the exact same thing, with such a more pleasant tone. Thanks. Sethie 08:06, 11 January 2007 (UTC)
No one has expressed support for my reply here, so to honor the criticisms I decided to repost the original Conflict section as a link external to Wikipedia. I hope everyone here sees that as a viable solution.
The section can be reincorporated when satisfactory references are found.
Tdadamemd 08:31, 11 January 2007 (UTC)
Cool- works for me! Sethie 08:33, 11 January 2007 (UTC)
Hey hey! Over at Sci.space where the section was reposted, one of the veteran members offered a reference that was published in Omni magazine back in 1993 that makes the same type of criticism of the terms "zero gravity" and "microgravity". The author is none other than Jim Oberg, widely held as a leading authority on spaceflight.
Here is his contribution: Jim Oberg reference to his 1993 Omni article
I trust that this will more than suffice as consensus for meeting Wikipedia standards for getting the Criticism section reincorporated as part of the article.
Tdadamemd 03:04, 12 January 2007 (UTC)


That's fantastic that you found a source. If you want to incorporate the section, please write it using that article as the source, i.e. don't put in any ideas not found in that article.

Congrats!Sethie 03:40, 12 January 2007 (UTC)

Congratulations on a good find, Tdadamemd. Here are a couple of citations for you to use. Take the wiki source text; it uses templates that do the formatting and are easy to transplant. --Jdlh | Talk 22:44, 13 January 2007 (UTC)

Thanks for the help and support. With all that has come to light here, I'd like to take a step back myself for the time being. I'm sure that there are other Wikizens who will want to make improvements to this aspect of the article. I'll check back on it in a while.
Tdadamemd 19:45, 18 January 2007 (UTC)
Well, I'll take it on. The term 'Zero Gravity' is completely wrong. An astronaut on the Shuttle or ISS is subject to the gravity field of the Earth, which is after all what keeps them in orbit. For Wikipedia to blindly propagate sloppy science would be to make us part of the problem. Even if it's a widely-used term, if it's scientifically incorrect, we would be irresponsible to simply parrot the popular misuse The Monster 16:41, 4 March 2007 (UTC)
Argh -- okay okay, but please emphasise the astronauts truly are weightless, and all this talk about being attracted to the centre of the spacestation is about as relevant as the effects of large distant stars. There is only one bullet point in the article at the moment that is relevant, and that is the small amounts of atmosphere -- if the Earth had no air, you could be in orbit near sea level, or at least as low as Mount Everest. You'd just have to go even faster. But thanks to the edge of the atmosphere, anything in orbit will slow down slightly from the exact speed it needs to keep at that exact altitude. Whophd 09:37, 9 March 2007 (UTC)

Hang on, W=MG so where W=0, yet mass is constant (albeit with small variations) => W/M==0/M=G=0. Non? Alex (unregistered wikiuser whatchamacallit)

Wait a second. This article needs a broader perspective. Arguments about the inaccuracy of the terms "zero gravity" and "microgravity" are well-taken in general, but this article and free-fall are also linked to from articles discussing interplanetary and interstellar space. All the stuff about what "free-fall" means for objects in orbit is effectively irrelevant when you expand your horizons to interstellar travel. The article should focus primarily on orbital mechanics because that's the context of all spaceflight so far, but should not completely ignore situations not involving orbit around a planet, moon, or even the Sun. PubliusFL 19:40, 2 May 2007 (UTC)

[edit] microgravity manufacturing

There must be a section on microgravity manufacturing, from perfect round ball bearings to perfect zero G pharmaceuticals. It's basically the biggest economic reason for a space station. JAF1970 18:53, 14 February 2007 (UTC)

Hey, if you can find the sources and edit the article, please go ahead and do so! It would be a fine addition. I could perhaps find some sources which claim that the microgravity manufacturing claims never had a strong economic base, and were only a cover for the true reasons for doing the space station or shuttle, which were national pride etc. --Jdlh | Talk 07:55, 16 February 2007 (UTC)
I have my hands full with other articles, but I'll try. JAF1970 07:09, 19 February 2007 (UTC)

[edit] The lead section

I pity the poor high school student with an assignment due who comes across this:

"Weightlessness is experienced by people during free-fall. Although the term 'zero gravity' is often used as a synonym, weightlessness in orbit is not the result of gravity itself being eliminated or even reduced significantly (in fact, the acceleration due to gravity at an altitude of 100 km is only 3% less than at the earth's surface . . "

For God's sake slow down! The article hasn't even established a firm grasp of weightlessness and free fall and given examples, before it's hitting the poor reader with provisos, exceptions, variations, the idea of orbiting, the concept of the accleration due to gravity . . . in a 64-word sentence containing at least five important ideas! It needs a rearrangement, give them some familiar examples to hold on to straight after the definition, make sure they get what free fall means -- it's too important to this article to send the reader off via that link to find out what it really means, it needs to be encapsulated in a sentence here, otherwise the lead section can't hold together. Then bring in orbiting and the problem with loose usage such as 'zero gravity'. Also, in terms of style all those brackets — and italics in the Overview — detract from readability. It may be correct, but is it digestible? A lead section should be "written in a clear, accessible style so as to invite a reading of the full article", and I think that unless the reader has already done physics in the last couple of years of high school, they are going to say: no, the effort of working out what this means outweighs the benefit I'm likely to get from it. Rexparry sydney 13:36, 17 August 2007 (UTC)

WP:SOFIXIT. — Swpbtalk|edits 15:35, 30 July 2007 (UTC) 13:41, 17 August 2007 (UTC)

[edit] Wiktionary

Because zero gravity redirects here, linking to this page is under discussion on Wiktionary. I am not a Wikipedian so I am curious how it would be possible to link the other way around, from here to Wiktionary. Besides weightlessness, it would be possible to find definitions for zero gravity and possibly microgravity, with shades of meaning as the article notes. What is the Wiktionary template, and can it be used to define more than one term, if it is prudent to do so? 70.112.121.70 (talk) 07:57, 20 March 2008 (UTC)

Hi, thanks for coming to help us at Wikipedia! There are templates to make links from here to Wiktionary; see Wikipedia:Wikimedia sister projects#Wiktionary. "Links to Wikimedia sister projects are best placed in the section of the article to which they relate, including Lead section, if possible...." I've added some links for "weightlessness", "zero gravity", and "microgravity". --Jdlh | Talk 19:05, 20 March 2008 (UTC)
Cool, thanks. I don't think I've never seen so many such links. Looks like I've got a new project now. 70.112.121.70 (talk) 03:06, 23 March 2008 (UTC)


[edit] Rotating Asteroid

Another way of achieving "weightlessness" would be to stand on the equator of a spherical asteroid rotating at the correct angular speed. If your weight (i.e. your mass times the gravitational field strength) equalled the centripetal force needed to keep you "orbiting" the asteroid's centre, you would feel "weightless". [To analyse this situation, we can use Newton's Second Law, i.e. net force = mass times acceleration. The net force is mg-R (where R is the reaction force exerted upwards by the ground on the person's feet) and the acceleration is r times (omega squared). Weightlessness happens when R is zero, i.e. when mg = mr times (omega squared); g = r times (omega squared). ] If we slightly slowed down the asteroid's rotation, and built a skyscraper on the asteroid's equator, we would find that one's weight would be downwards at the foot of the skyscraper, but one's "weight" would feel "upwards" (i.e. R would be negative) at the top of the skyscraper. In a room at the bottom of the skyscraper, chairs would stand on the floor, but in a room at the top of the skyscraper, chairs would be upside down and standing on the ceiling. If the skyscraper was tall enough, the skyscraper itself would be "weightless". Hence the idea of the very tall (i.e. thousands of miles tall) tower on the Earth, so tall that it would be "weightless", and acting as a "space elevator". These sort of calculations reveal that there is a limit to how rapidly an astronomical body can spin; if an astronomical body spun too fast, it would disintegrate because gravitational forces would not be powerful enough to provide the centripetal forces necessary to keep the material of the body rotating. [Martin] —Preceding unsigned comment added by 91.106.36.179 (talk) 19:14, 23 March 2008 (UTC)

Martin: Interesting! I hope you can find someplace outside of Wikipedia to publish this. Unfortunately, it's not suitable for Wikipedia as-is because it looks like original research, which we don't do; we just cite other work that was published by reliable sources. --Jdlh | Talk 20:49, 23 March 2008 (UTC)