Talk:Outer space

Uncategorized

Shouldn't the possiblity of Creationism be included? I mean, it makes it sound like the Big Bang is 100% assured of a thing. Not that I'm religious, but I'm speaking on behalf of those who are, and to keep Wikipedia an unbiased place. Also... why is this page so short? --CrazyCasey 17:57, 5 July 2006 (UTC)

I agree with CrazyCasey- all Wikipedia articles should be unibiased, and I think removing all references to any sort of belief set would be great. --User:Chronology of Life

Religion doesn't belong in this article. Religious views can be applied to everything, doesn't mean we should list them in every article. It's not a matter of bias, but of Undue_weight. With the way outer space is related to physics and astronomy (specially the cosmology which we discuss), utilizing anything but a scientific tone would be giving whatever other view undue weight in the article. Star Ghost 02:01, 20 July 2006 (UTC)

Please leave my "See also" to the Karman line in: I was trying to search on the no-accent name and missed because the link was re-labeled with the accents. I will propose a rename on the page. -- Fplay 22:55, 21 December 2005 (UTC)

If I explode then will blood come from my eyes? What if the pressure was removed very slowly, from 100 kPa at a rate of say 1 kPa a minute and supposing I had breathing equipment? --Username132 00:17, 29 January 2006 (UTC)

What is the density of air in outer space?

0gm^-3?

There isn't air in outerspace... --CrazyCasey 17:57, 5 July 2006 (UTC)

Maybe he meant matter? There are a few lonely atoms wandering around. I remember seeing this kind of statistics in some physics book. Star Ghost 02:01, 20 July 2006 (UTC)

I have placed uncategorized and undated posts in this section. Please sign all comments with 4~ and place in a new subsection.statsone 06:15, 10 July 2007 (UTC)

Conflict with religion

I don't think this section is relevant, does anyone protest it's removal?

Link Removal

I have removed the links to website in anther language for 2 reasons. One is they were the same site. Second, they were in another language. More appropriate to be placed in that wiki's language site.

Also, please sign all comments with 4 ~'s statsone 15:43, 22 July 2006 (UTC)

Wikipedia already has a terrible bias towards Evolution and its many unproven theorys and dating methods. As usual this has a terrible effect on readers as more and more people begin to accept these things as fact when any knowlegable evolutionist knows they are NOT facts at all. There is plenty of science that is real fact and disproves the whole "really old earth" theory. "Zealotii 09:45, 15 October 2006 (UTC)"

In space on the Moon?

Is one in space when on the Moon? I'd say one isn't in space when on a celestial body. Although of course there are border cases, like being on a asteroid. And on Earth you enter space when the air gets too thin, but on the Moon there is no atmosphere. Or is that not the criterium? DirkvdM 07:42, 1 August 2006 (UTC)

The answer would depend on the audience. I, for example would think "in space" means in freefall and outside the atmosphere of any nearby planets, but I think the Man on the Bondi Tram would think that "space" is anywhere beyond Earth, or altenatively, anywhere where a space suit was needed. (days after writing I noticed I didn't sign this) --Polysylabic Pseudonym 04:58, 5 August 2006 (UTC)

Assuming that one is not in space when on the moon, if one was to travel up from the lunar surface, at what point would he/she be "in space"? Would it be the same point at which a person leaving the earth's atmosphere is considered to be in space? Vsst 02:53, 20 March 2007 (UTC)

This kind of thing isn't a question of fact, but a question of definition, and is really rather arbitrary. If you want to know whether someone is in space because you want to know whether he'll burn up or get slowed down by the atmosphere, or whether he needs a space suit, he's in space on the moon. If you want to know whether someone's in space because you need to know whether her microgravity experiment will be successful, she's not in space on the moon. As to where space begins, the article explains why that's a gradual thing which also depends on what you mean by "space". --Slashme (talk) 06:40, 11 June 2009 (UTC)

Vacuum

The_monkeyhate, do you have any grounds for your assertion that unprotected humans would freeze in milliseconds in space? It's flatly contradicted by the NASA doc cited. SeanWillard 23:57, 12 October 2006 (UTC)

Their orbits never "decay" because there is almost no matter there to exert frictional drag.

I would like to change "Their orbits never "decay" because there is almost no matter there to exert frictional drag." to "Their orbits never "decay" because the pull of the earth's gravity is canceled by the centrifugal force of their tangential velocity"

I have removed this business. Orbits do decay!. The Hubble Space Telescope gets raised every time it is serviced to keep it in orbit, for example. In geosynchronous orbit, there is a lot less matter than in low Earth orbit, but it still is a issue and all satellites have a rocket and spare fuel to deal with this. --EMS | Talk 17:12, 5 February 2007 (UTC)

Outer space *vs* inner space

I realise that the popular media use the term "outer space" for everything, but it is my understanding that "outer space" refers to space outside the solar system, while inner space (or plain "space") refers to space within the solar system.

--Black Walnut 12:11, 16 January 2007 (UTC)

Hehe. I came to this talk page specifically to criticize the use of the stupid "outer space" term. For such to exist, there must also be "inner space", which is a ridiculous conecpt. Also, religion shouldn't be mentioned. That's ridiculous too. --194.251.240.114 23:19, 25 January 2007 (UTC)

I just checked the internet, and the only places I found "inner space" mentioned where in the titles of science fiction books and movies and in regard to yoga type stuff. Also, according to answers.com, outer space is defined as "Any region of space beyond limits determined with reference to the boundaries of a celestial body or system, especially: 1. The region of space immediately beyond Earth's atmosphere. 2. Interplanetary or interstellar space."

Vsst 00:56, 4 May 2007 (UTC)

I'm Confused

This isn't necessarily questioning the legitimacy of the claim..but a source would be helpful.

• 32 km (105,000 ft) - Turbojets no longer function.
• 34.7 km (113,740 ft) - Altitude record for manned balloon flight

It just seems..odd, to me, that a manned balloon flight could fly above the point where turbojets no longer function.

Not so strange: a turbojet can fly up to the point where it doesn't get enough oxygen in the front to burn its fuel. At that point, the atmosphere is not yet so thin that a hydrogen balloon can't get enough buoyancy to lift. --Slashme (talk) 06:45, 11 June 2009 (UTC)

Milestones to outer space

The 62,000 km figure is totally wrong. Earth has more gravity than the Moon so this point has to be most of the way away from it. 320,000 km Earth altitude is more like it (the distance from the earth to the moon minus 62,377 km). Also, this might make a reader think the moon's zone of influence is a "layer", rather than the small sphere surrounding the moon that it is. Sagittarian Milky Way 09:11, 13 March 2007 (UTC)

Yes, I'm pretty sure the author mis-read the Apollo 8 article about this. Wasn't it 62,000 km from the Moon? Trojan_points#L2 puts it at "61,500 km from the Moon." Sdsds 05:02, 20 March 2007 (UTC)

The thing is, the moon's distance itself varies by almost as much as the 62,000 km, moving the balancing point in and out. Does it even matter? (for example, many of the spacecraft orbits are given only as an approximation). Also, perigee is wrong, I'm going to change it. Sagittarian Milky Way 03:02, 23 March 2007 (UTC)

You're absolutely right: the distance to the L1 balancing point doesn't matter so much. What really matters for most mission planning is the delta v required to get there. If you can get there, and if you're willing to wait long enough, then a clever sequence of gravity slingshots can get you anywhere in the universe using only minimal thrust. (See Interplanetary Transport Network.) In that sense, this point does matter, because it's the nearest place "beyond" the Earth's gravitational domain. Sdsds 00:59, 24 March 2007 (UTC)

Right, the cool thing is that it's a bubble of extraterrestrial gravity, deep inside Earth's Hill Sphere. What I meant though is that since the milestones to space altitudes for the ISS, Mir, Skylab, etc. are approximate then the L1 distance can be too. The section looks much cleaner that way. Sagittarian Milky Way 07:12, 25 March 2007 (UTC)

Microgravity Statements

In the "Satellites" section, I'm not sure the following statement is completely correct:

"A common misconception is that people in orbit are outside Earth's gravity because they are obviously "floating". They are floating because they are in "free fall": the force of gravity and their linear velocity is creating an inward centripetal force which is stopping them from flying out into space. Earth's gravity reaches out far past the Van Allen belt and keeps the Moon in orbit at an average distance of 384,403 km (238,857 miles). The gravity of all celestial bodies drops off toward zero with the inverse square of the distance."

Didn't astronauts still "float" while travelling to the moon at a constant velocity without a "free fall" state?Drawingnearisgood 16:30, 4 May 2007 (UTC)

There are a number of ways to be in "free fall" within the gravitational zone of a planet. One is to be in a stable circular orbit around the planet. One is to be traveling on a parabolic ballistic trajectory, typically near the surface (if necessary using thrust to overcome atmospheric friction). A special case of this is going straight up and down. If you go straight up fast enough, you're beyond escape velocity, and you just keep going. You're still slowing down (i.e. not "constant velocity"), just like a stone that is tossed straight up into the air, but you're not slowing down enough to keep you from completely leaving the region. Also, just like if you get thrown into the air, you won't feel the gravity, hence "free fall". --Slashme (talk) 07:08, 11 June 2009 (UTC)

Centripetal/Centrifugal Confusion

The article states that:

"A spacecraft has not entered orbit until it is traveling with a sufficiently great horizontal velocity such that the acceleration due to gravity on the spacecraft is less than or equal to the centripetal acceleration caused being its horizontal velocity (see circular motion)."

This sentence is slightly incoherent and slightly sketchy on the physics. If you choose to describe it in the Earth's "inertial" reference frame, it is in - circular -orbit when the force of gravity is of the exact magnitude to act as a centrifugal force (put in better English though). Or, in the craft's reference frame, "until the centrifugal force cancels out the gravitational force". The non-circular case is a bit more complicated and doesn't really belong here. 163.1.99.20 21:27, 11 June 2007 (UTC)

I agree. In fact, if the acceleration due to gravity is less than the centripetal acceleration anywhere in the orbit, then the opposite must be true at some other point in the orbit. To quantify this:

• Call the minimum radius Rmin (radius of the Earth + some atmosphere). A reasonable condition for calling a spaceship in orbit is that the perigee >= Rmin. The necessary condition in terms of Vh (horizontal velocity) is then not trivial and requires a bit of understanding of central force problems. Assuming the typical simplifications (Newtonian gravity, spherical mass, etc.) one arrives at the inequality (please check math before including in article):

1/2 ((r/Rmin)^2 - 1) * Vh^2 - (G M / Rmin + 1/2 Vr^2) >= 0.

• Solving this yields:

Vh >= sqrt[(2 G M/Rmin + Vr^2) / ((r/Rmin)^2 - 1)]

• Basically, there is no simple way of stating the condition for orbit. Someone with more experience should decide how to modify the article. Jtepper (talk) 07:47, 25 December 2009 (UTC)

Free fall

The section for Sateliites describes satellites as being in Free Fall. This seems to be wrong. They are not in free fall ( only under the influence of gravity) butin orbit. Comments?statsone 06:20, 10 July 2007 (UTC)

Unless you're operating a thruster to maintain it, orbit is synonymous with freefall. —Preceding unsigned comment added by Nentuaby (talk • contribs) 01:33, 16 October 2008 (UTC)

Absolutely. The problem is, colloquially, "free fall" might be interpreted to mean falling closer and closer to the surface of the Earth/other body. Nonetheless, the terminology is justified because in a scientific setting, free fall is used synonymously with inertial frame. In other words, the satellites are moving under nothing but their own inertia through the gravitational field. Jtepper (talk) 08:05, 25 December 2009 (UTC)

Capitalization

Shouldn't the words "Outer" and "Space" both be capitalized since it designates a place name? SharkD 03:52, 22 August 2007 (UTC)

Wikipedia's style [1] says no. Just what has been agreed on. --statsone 05:44, 22 August 2007 (UTC)

But Outer Space is a region, not a celestial body; and it is certainly well known. SharkD 06:28, 22 August 2007 (UTC)

This is where it does get tricky. I would take it as small case only because it is wikipedia. You may want to post a discussion on the style talk page and ask for comments--statsone 06:33, 22 August 2007 (UTC). [2]

Well, if outer space were capitalized, then interplanatary space would need to be capitalized, too. I guess I'll leave it at that. The reason I ask is because I was once corrected for not capitalizing it. SharkD 06:52, 22 August 2007 (UTC)

Vacuum in Space

For the cite needed, I found 1×10^-15 Torr [3]. ( Do a search on "pressure in interstellar space" in google). Converting back to Pa, I get 1.333×10^-21 Pa which is different from what is listed. Looking back at the history of the article, there have been many numbers --Statsone 14:41, 23 September 2007 (UTC)

Aren't the vacuums created here on Earth much weaker than the vacuum of outer space? The whole "what would happen if exposed in outer space" bit seems to discuss the effects in vacuums created on Earth, which I suspect would not be the same in outer space. Please correct me if I am wrong. ~ UBeR (talk) 17:08, 15 February 2008 (UTC)

No, they are not much weaker. In fact, laboratory equipment is capable of generating much stronger vacuums than what humans are generally talking about when we mention space (the vicinity of Earth and the Moon). More practically, most vacuum chambers are relatively weaker, but for the practical purpose of describing the effect on bodies or equipment, both they and outer space may be treated as zero pressure.Nentuaby (talk) 01:39, 16 October 2008 (UTC)

Expanding the Article

A way to flesh out this article would be to add: some definition of how crafts move in space being that there are no molecules; how much gravity exerts its force to the moon and an explanation on how that force extends to "stationary" satalites; and how distance is measured in space. I am not an astrophysicist, just a curious person, so I would appreciate those additions as I do not consider any to be "undue weight". Agreed? —Preceding unsigned comment added by 67.173.2.11 (talk) 01:37, 8 November 2007 (UTC)

space vs outer space

There's a large number of wikilinks to space that ought to be linked here instead. Anyone have any idea how these can most easily be fixed? --jwanders^Talk 10:44, 21 February 2008 (UTC)

Frankly, I just searched for cislunar space, something decidedly more specific from outer space, and was re-directed here. cislunar is a unique area that should have its own page or at least a mention on this page. (cislunar is the area between the earth and the moon) 128.205.11.224 (talk) 07:44, 24 April 2008 (UTC)

"Cislunar space" was supposed to redirect to "geospace." I've fixed the redirect. I redirected it because all the article said was that cislunar space was the space between the Earth and the Moon, which was a bit like saying that Grant is buried in Grant's tomb. Serendi^podous 18:58, 19 November 2008 (UTC)

Escape velocity

The article starts with a pretty odd definition: the relatively empty regions of the universe outside the escape velocities of celestial bodies. Physically, what does it mean to be outside a velocity? (I'd answer: nothing, but maybe someone can enlighten me). Isn't there a better definition? --Cyclopia (talk) 22:26, 17 October 2008 (UTC)

You're right (and here I am inserting the link without noticing the nonsense). I've spent a while figuring out how to fix it, almost deciding on replacing 'escape velocities' with 'gravitational influence' which I think is what the author intended. Then comparing with the article I find that this sentence contradicts the gist of the article, which emphasises being away from ""Earth"" rather than celestial bodies. That, I think, is the common usage, and whatever view you take it's a vague concept. To be honest, I'm not sure why it merits an encyclopaedia page.--Alkhowarizmi (talk) 10:18, 18 October 2008 (UTC)

It should be "atmospheres". Serendi^podous 10:50, 18 October 2008 (UTC)

It surely is better, but later there is a section on the geospace where it is pretty clear that there is still substantial atmosphere in what is called outer space nonetheless. I try to detail a bit the definition. --Cyclopia (talk) 11:29, 18 October 2008 (UTC)

Nice improvements (both)--Alkhowarizmi (talk) 14:45, 18 October 2008 (UTC)

Milestones section

I've removed the Milestones section. Much of it was unreferenced, a lot of it was probably outdated (records usually need to be updated every year, which is a tedious task) and much of it seemed pointless (why go from Lunar apogee to Martian perigee? Venus is actually closer to Earth). Much of the information in that list can be easily expressed with the image I've placed at the top of the page. Serendi^podous 19:10, 19 November 2008 (UTC)

How is Torr a relevant unit?

Why should Torr, an aged non-SI unit be used in the article? —Preceding unsigned comment added by Askeuhd (talk • contribs) 23:38, 21 November 2008 (UTC)

I have no idea what a "torr" is, but no other science-related article I've worked on has used it, so I don't think it's needed. Serendi^podous 13:26, 22 November 2008 (UTC)

The Torr is basically a mmHg, and is often used as a customary unit in vacuum technology. I've used vacuum pumps on freeze driers that had gauges calibrated in mTorr. But yes, it shouldn't be used here IMHO. Go SI. --Slashme (talk) 07:18, 11 June 2009 (UTC)

Karman vs. Calgary - edge of space poll

The work described in the referenced space.com article[4] is quite interesting, and should definitely be covered somewhere in this article. However with due respect to the space.com journalist that article is not particularly scientific, and the von Karman aeronautics/astronauitcs definition is still more practically useful. Should the lead of this article return to citing von Karman's defintion?

• Support - as proposer (sdsds - talk) 03:15, 24 April 2009 (UTC)
• Neutral - I understand the argument, but I prefer the well-defined, measurement-based boundary to the previous, somewhat arbitrary, definitions. It makes more sense to me. But I recognize it might be unscientific, so I'm staying neutral on this. --Waldir ^talk 21:16, 25 April 2009 (UTC)
• Support. Kaman's definition should be in the lead; alternate definitions may be mentioned, but that appears to be the official one. Serendi^podous 21:39, 25 April 2009 (UTC)
• Use both, something like "The FAI defines the edge of space as being the Kármán line, 100 kilometres (62 mi) above mean sea level, however in 2009 scientists at the University of Calgary discovered that the edge of space is actually at an altitude of 118 kilometres (73 mi)." Perhaps the definitions used in the USA should also be mentioned after this sentence. --GW… 21:54, 25 April 2009 (UTC)
• Oppose - How is an exact measurement from a scientific device unscientific? I think the exact measurement should be in the lead, and the previously accepted definition be covered elsewhere in the article. Dionyseus (talk) 03:53, 26 April 2009 (UTC)
  • But the exact measurement has not replaced the accepted definition. --GW… 07:05, 26 April 2009 (UTC)

Not yet perhaps. Dionyseus (talk) 07:43, 26 April 2009 (UTC)

I mailed David Knudsen, one of the authors of the original research, and he had the following to say:

While I'm flattered to see our measurement of the "edge of space" in the article, I have to confess I don't believe the result is fundamental enough to be included as part of the top-level definition of "outer space". I feel that the reference in the top paragraph should be removed.

I'm pleased to see our result in the "Boundary" section and I would only suggest a few tweaks:

I would say that the results were *reported* in 2009, since the experiment itself took place in 2007.

I'd suggest "The boundary represents the midpoint of a gradual transition over tens of kilometers from the relatively gentle winds...etc

This was only the second time that direct measurements *of charged particle flows* have been conducted in this region...

Also, the best reference is:

Sangalli, L., D. J. Knudsen, M. F. Larsen, T. Zhan, R. F. Pfaff, and D. Rowland (2009), Rocket-based measurements of ion velocity, neutral wind, and electric field in the collisional transition region of the auroral ionosphere, J. Geophys. Res., 114, A04306, doi:10.1029/2008JA013757

--Slashme (talk) 07:22, 11 June 2009 (UTC)

He also sent me a follow-up email, with the following comment: "I might add one point about why I think the Calgary measurement is not fundamental enough to be used as a definition. The problem is that with only one pass through that region lasting only twenty or so seconds, we have very little idea of how that transition altitude might vary, either over time or with latitude." --Slashme (talk) 05:58, 17 June 2009 (UTC)

Temperature in space

There has been some action in the article on the temperature of outer space. The temperature reported is the temperature that a piece of metal near the earch would acheive. But, by this logic, space has no particular temperature: a piece of metal at a different location (farther from the sun, closer to the sun) would have a different temperature, and another object at the same location in steady state with solar radiation would have a different temperature (that's why we are going to fry the earth with global warming by altering the greenhouse effect).

The temperature of space is typically referred to the temperature of a typical point in space far from a source of radiation such as the Sun, another star, or a galaxy. This temperature is the temperature of the microwave background, ~3K. Interstellar space (within our Galaxy) has temperatures ranging from a few K in Molecular clouds to 10,000K in Emission nebulae. David s graff (talk) 22:35, 29 May 2009 (UTC)

Geospace

I think there have been edits at cross-purposes in the second paragraph of the Geospace section. I would fix it, but I'm not sure how. Here is the paragraph:

Although it meets the definition of outer space, the atmospheric density within the first few hundred kilometers above the Kármán line is still sufficient to produce significant drag on satellites. Most artificial satellites operate in this region called low earth orbit and must fire their engines every few days to maintain orbit. The drag here is low enough that it could theoretically be overcome by radiation pressure on solar sails, a proposed propulsion system for interplanetary travel. Planets are too massive for their trajectories to be affected by these forces, although their atmospheres are eroded by the solar winds.

The last sentence seems to be saying that other planets within Earth's geospace are not affected by... some forces that are presumably described elsewhere. Most likely this is because other planets within Earth's geospace tend to collide with Earth, kill everyone, and leave no one to edit Wikipedia. --99.33.25.89 (talk) 20:11, 22 November 2009 (UTC)

I hadn't given this article a read through in a while; hadn't realised how badly written it is. Yes, you're right; that line belongs in interplanetary space, not geospace, and the bit about the planets being too massive to have their orbits affected by the solar wind was just lunatic. I'm not particularly massive, but it would still take a hurricane to knock me over. That something weighing a few octillion tons would not be adversely affected by the pressure of a wind that is all but pure vacuum isn't something that needs mentioning, methinks. Serendi^podous 20:46, 22 November 2009 (UTC)

Definition

Per WP:V and MOS:BEGIN, the intro of this article should give a concise definition based on verifiability, not truth. Google searching for "define" gives a pretty unambiguous definition[5] as "area outside the earth's atmosphere", even when you get past the mirrors. The problem of defining as above any bodies atmosphere is what about the moon and other bodies without atmospheres? I think we mean beyond anything that is a celestial body, not its atmosphere. Fountains of Bryn Mawr (talk) 19:18, 3 December 2009 (UTC)

So according to this definition, the surface of Venus, with its 90 atmospheres of pressure and 900 degrees Fahrenheit temperature, would be space? We have to deal with this somehow. Otherwise the definition makes no sense. Serendi^podous 19:27, 3 December 2009 (UTC)

Venus is a celestial body, so its confines (including its atmosphere) would not be outer space. So that part (which you deleted) would be part of the def. celestial body its self is key to this article's def, but that article (Astronomical object) has many problems as well (trying to clean that up led me here - funny how that happens). Fountains of Bryn Mawr (talk) 22:55, 3 December 2009 (UTC)

The Outer Space Treaty includes the Moon and other celestial bodies in its definition. Thus I'm not sure astronomical objects should be excluded from this article.—RJH (talk) 18:53, 25 December 2009 (UTC)

Throwing in another stab at a def. The concept of Space "the unlimited expanse in which everything is located" redirects here. "Space" is the more notable term being defined here[6] over "outer space"[7]. In fact this whole article should probably be moved to a more inclusive title such as Space (universe), since Outer space has a more narrow def and to me is a real 1950s term, no body calls it that anymore. The rest of the article should probably be cleaned up because it tends to define the more narrow term "outer space". Fountains of Bryn Mawr (talk) 19:22, 23 January 2010 (UTC)

Inflated balloon on top of a mountain

Hi there, this might be some kind of a mental black-out on my side, but concerning the passage

"This decrease in pressure was further demonstrated by carrying an inflated balloon up a mountain and watching it gradually deflate, then reinflate upon descent",

why would an inflated balloon deflate when it is carried up a mountain? Because of the lower surrounding air pressure, it should actually expand even more. I don't have the cited reference at hand. 84.63.98.54 (talk) 16:51, 29 December 2009 (UTC)

Yeah you're right. Good catch. It should be corrected now, per the cite.—RJH (talk) 20:48, 30 December 2009 (UTC)

Intergalactic space

I am not a specialist, maybe that's the reason, but this sections seems very confusing. In the first paragraph it says that "intergalactic space is very close to a total vacuum". In the second - that it's in fact plasma and IGM which is up to 100 times denser than the universe on average. So which is it? And if IGM is so dense then where does the low average density of the universe come from?
The first paragraph is especially confusing. Consider the second and the third sentences: What is this "is probably nearly empty" in the third sentence trying to say? That voids are about as empty as intergalactic space, or emptier or denser? Then, in the next sentences all of a sudden comes the bit about the average density of the Universe. Why Universe if we are talking about intergalactic space here?
So, after reading this sections I still have all the questions:
Are "intergalactic space" and "void" one and the same thing or not?
If not, do they differ in density and what is the average density of each?
Are intergalactic space and voids the closest things to a total vacuum or are they filled with relatively dense IGM?
92.243.183.1 (talk) 12:42, 19 April 2010 (UTC)

What heats up IGM?

From the section on Intergalactic Media (IGM): "The reason the IGM is thought to be mostly ionized gas is that its temperature is thought to be quite high by terrestrial standards (though some parts of it are only "warm" by astrophysical standards)."

Why is the IGM so hot? What is its heat source way out between the galaxies, so far away from stars?

Please add the answer (and linked source), to the article's IGM section.

Phantom in ca (talk) 02:26, 7 November 2010 (UTC)