Talk:Earth/Archive 2

message: How did the Earth form? What aspect of the Earth or its location do astrobiologists hypothesize as having been crucial to the development of its most idiosyncratic feature--life. How did life emerge and when. Have there been any noteworthy biological events since the appearance of the first cell? How does the emergence and history of life relate to geological and climate evolution? How often is Earth hit by asteroids? What have been the consequences? Do we expect more? 
How did scientists determine the average density of the earth? - The average density is Mass divided by Volume. To find the volume you need the radius which you can find by measuring the curvature of the Earth like Eratostenes did about 230BC. Then you know the volume of the Earth (assuming it is sufficiently spherical). To measure the mass you need to know the gravitational constant which was measured sometime I believe sometime in the 18th century. You apply Newton's law for gravity (the one with inverse-square radius) and you have the mass.
How many human-made satellites are there and when did the first one (sputnik) go up? 
If you count every single piece of manmade debris - millions. Sputnik - October 4th 1957. 
How do people study the Earth? What kind of scientists study it? What questions plague us, if any? What are predicted fates of the Earth? What about the ozone hole? What about the Kyoto protocol? What about geomagnetic reversals?168... 05:22, 17 Jan 2004 (UTC)
thread_title: Missing info

message: Nearly all humans live on Earth: 6,327,152,352 inhabitants (November 1, 2003 est.)
:Wow, that's an incredibly accurate "estimate"?? And what does it mean "nearly all humans live on Earth"?? Even those who are not on earth would not consider someplace outside earth their permanent residence. Certainly a more specific observation could be made (e.g. number of humans on average who are living in space at a given time). Revolver 01:19, 16 Mar 2004 (UTC)
replies: text: This issue has been raised in talk: before. Note that the very next line of the article explains what "nearly" means; "In orbit about Earth: 2 astronauts (November 28, 2003), on board the International Space Station." Whether being on board a permanently manned space station for a portion of a year counts as "living" there is apparently a matter of debate, but I believe it should count; scientists who spend the winter at the Antarctic research base are often described as "living" there for the winter, and the situation is quite analogous IMO. Bryan 01:50, 16 Mar 2004 (UTC)
thread_title: Humans living in orbit

message: Bryan Derksen, where are you getting that mean temperature from? Averaging the min and max gives 258, not 282... If that average temp. was obtained thru a different method, care to mention the source? --Cantus 06:00, 25 Mar 2004 (UTC)
replies: text: I don't know the source offhand, but the mean temperature of a planet is not necessarily just the max temperature plus the min temperature divided by two; those two extreme temperatures occur under exceptional conditions at just two particular locations on Earth's surface. Averaging them and calling that the mean would be like trying to determine sea level by averaging the height of Mt. Everest and the depth of the Mariannas Trench, so I'm not surprised it differs. :) Bryan 06:21, 25 Mar 2004 (UTC)

text: has the mean temperature as 287 K, which is pretty close to the figure that was in the article. Bryan 06:28, 25 Mar 2004 (UTC)
thread_title: Temperature

message: : Most of them have reported a heightened understanding of its value and importance, reverence for human life and amazement at its beauty, not usually achieved by those living on the surface.
Does this need to be in this article? Do we even have a source for it? Edward 10:01, 25 Jun 2004 (UTC)
replies: text: I was unsure about where to place it, the Earth actually felt like the most relevant. We probably don't have a source for the "most" bit - that would be 200+ people and there wasn't a study about it, but so far I've read such things said by both space tourists, by Glenn and a couple other American astronauts and by several Russian cosmonauts as well. Some of them mentioned that these feelings are common among other spacefarers too. I think this is quite important fact, even if it sounds a bit silly and pompous. This can also be connected to the (missing?) article about Pale Blue Dot. Paranoid 12:55, 25 Jun 2004 (UTC)
thread_title:  Irrelevant 

message: Someone attempted to add a comparison of the torques felt on the Earth by different astronomical objects in order to explain why the moon has a stabalizing effect on the axis of the Earth. For one thing, this is rather technical information and might not fit very well into this page, but worse than that, the numbers quoted were simply very wrong. It is clear from the scale of the numbers stated that the author was merely comparing the force exerted on the Earth from various astronomical objects.  However the force is not the same as the torque. The torque depends not on the total force but on the difference in the force applied to one side of the equatorial bulge rather than the other. Because it is so close, the moon has the largest gravitational gradient across the Earth of any astronomical object (followed shortly thereafter by the sun). Hence, the Moon exerts the largest torque on the Earth and that is why the moon acts to stabilizes the Earth's axial tilt.
However, other factors are also important. For example, relatively constant torques, such as from the Moon and Sun tend to cause axial precession and not nutations or axial tilts. For other planets (e.g. Mars) the total torques exerted depend more significantly on where it is in its orbit with respect to its nearest neighbors (e.g. Earth and Jupiter). It is when such time varying torques are a significant component of the total torque that one tends to promote chaotic shifts in the planet's axis.
Dragons flight 18:56, Sep 11, 2004 (UTC)
:I agree that I did not take into account the variability of the torques (only the Sun and Moon apply constant torque), but that is a minor quibble --it is the very variability of these "pulse torques" that drives rotation into an eventual chaotic regime. After thinking about it some, I must admit Dragons flight is right that it is the tidal forces I should have used. It is thus right and proper to remove the erroneous sentence. It was a tad too technical anyway, and did'nt fit well with the flow of the text.
:Urhixidur 03:01, 2004 Sep 12 (UTC)
Seems that the complex and as stated controversial subject of chaotic instability of Earth's axial tilt under moon should be moved to another article, maybe to axial tilt, rather than in this long general article. -Vsmith 01:49, 17 Oct 2004 (UTC)
thread_title:  Torque Comparison 

message: Cantus wrote: Encyclopedias are not written for aliens or animals.  So what's wrong with aliens (or animals) reading Wikipedia? — Monedula 11:55, 12 Sep 2004 (UTC)
thread_title: Humans/We

message: I removed the word "billion" in the second most recent edit as of when this edit to the talk page was made, but then someone started to include both forms?? Any comments about whether the word "billion" should be kept?? 66.245.126.161 15:47, 9 Oct 2004 (UTC)
thread_title:  Billion 

message: Earth is almost never called Sol III. Google hits:
;Earth: 11.100.000
;Terra: 4.650.000 (most indirectly related)
;Sol III: 4.340
The latter is almost exclusively science-fiction. It is not enough to be featured in the first line in the article about Earth. An obscure SF-term is not notable enough for that! Gerritholl 09:47, 16 Oct 2004 (UTC)
replies: text: How about "Dirt"? Google shows 654 hits for "Planet Dirt" :) -- Arwel 22:50, 28 Oct 2004 (UTC)
thread_title:  Sol III 

message: I've seen no mention of the number of artificial satellites orbiting Earth. I think it is definitely worth noting that our planet has thousands of bits of metal that we put up there ourselves orbiting it, even if only from an astronomical standpoint. --Jacius 22:30, 24 Oct 2004 (UTC)
replies: text: I don't think it's possible to know how many "artificial satellites" there are, in the sense of separate objects in orbit which were put there by humans. Back in the 1960s there was an experiment which involved releasing millions of "needles" (or exploding a satellite into very small fragments, I forget which) into orbit to see how they behaved. This has polluted certain orbits ever since, and was a particularly stupid idea. -- Arwel 22:53, 28 Oct 2004 (UTC)
thread_title:  Artificial Satellites 

message: It would be good to link the various moon navigator's together, and provide a small page explaining them(it could be called Wikipedia:moon navigator).  Right now, it's not obvious what purpose it serves.  I don't have time to do it right now, but I'll do it if no one else gets to it. JesseW 13:39, 29 Oct 2004 (UTC)
thread_title:  moon navigator 

message: The template seems to have been corrupted. I don't know how to access it so I copied the infobox from before the template move (11-4) and pasted it back into the article. -Vsmith 01:00, 14 Nov 2004 (UTC)
replies: text: Looks like an anonymous user chopped off the last few lines of the template, which removed the table-termination code (as well as the "edit this template" link that would have made it easier to fix :). The entirety of the article wound up being engulfed by the table as a result. I've fixed it now. Bryan 02:04, 14 Nov 2004 (UTC)
replies: text: Thanks. I had figured that was the likely problem, just couldn't find the template file to fix it. I'm learning... -Vsmith 03:20, 14 Nov 2004 (UTC)
replies: text: Whenever you see something in curly brackets like , you can usually find it at http://en.wikipedia.org/wiki/Template:this. The exception is when it's explicitly in another namespace, such as , a trick that's used in many of the "voting" administrative pages to keep things tidy. That doesn't come up in regular articles, though. Bryan 03:48, 14 Nov 2004 (UTC)
thread_title:  Infobox template 

message: Rather large for an article don't you think?
http://commons.wikimedia.org/upload/f/f4/The_Earth_seen_from_Apollo_17.png  
Zen Master 05:15, 19 Nov 2004 (UTC)
replies: text: The image that's actually displayed on Wikipedia is only 110kB, though, since it's been thumbnailed. You only download the 5MB version if you click through the thumbnail. Bryan 08:00, 19 Nov 2004 (UTC)
replies: text: yeah but still too big, and links to too big of a file. I guess wikipedia gets their bandwidth for free.  Zen Master 08:16, 19 Nov 2004 (UTC)
replies: text: I think it's donated by Bomis. — David Remahl 08:21, 19 Nov 2004 (UTC)

text: Personally, I think it's good both for the reason that extra resolution is always better for free content when possible(makes reuse easier), and the impression that the earth is as big as it is is strengthend by having an image that can't easily be displayed on one screen. ;-) JesseW 08:43, 19 Nov 2004 (UTC)
replies: text: I agree about the resolution, but what about modem or other slow users and if wikipedia's bandwidth really is free may I have some too?  Zen Master 10:05, 19 Nov 2004 (UTC)
replies: text: I just added a note to the caption.(On Template:Planet Infobox/Earth)  Re: free bandwidth; you just did, and do everytime someone looks at your User page. ;-) JesseW 05:47, 20 Nov 2004 (UTC)
thread_title:  That Image of Earth is 5 MBs... 

message: I've heard talk about a hollow Earth theory.. and I've done little research on it with Google. I'm not sure if it's complete bogus or if it's true, but some people seem to believe the theory (and some claim to have traveled inside Earth). Shouldn't something about this theory about Earth be included? --Mike 07:43, 21 Nov 2004 (UTC)
replies: text: There's an article about it at Hollow Earth. Oddly enough, it's not linked to from this article; I'll fix that. Bryan 08:47, 21 Nov 2004 (UTC)
thread_title:  Hollow Earth?