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265

It is a common misconception that something in (Low Earth) orbit (like the ISS) is far away. This is not the case -- orbit is more about going sideways really fast than it is about "being up". (xkcd -- Orbital Speed) The ISS has perigee at 402 km and apogee at 409 km ([1]). Unless you're further north / south than 51 degrees (The ISS' orbital inclination), ...


86

This strongly depends on definition of what smoothness is. The Discover Magazine blog addressed this in 2008 OK, first, how smooth is a billiard ball? According to the World Pool-Billiard Association, a pool ball is 2.25 inches in diameter, and has a tolerance of +/- 0.005 inches. In other words, it must have no pits or bumps more than 0.005 inches in ...


57

Their claim is incorrect. On an astronomical scale, one kilometer is a very small value. In fact, Earth's orbit regularly varies by far more than 1km. According to the NASA's Solar System Exploration website's facts and figures, Perihelion (closest) Metric: 147,098,291 km Imperial: 91,402,640 miles Scientific Notation: 1.47098 x 108 km (0....


56

I could not find any scientific evidence that the earth was once completely covered by water (not lava). However, Australian scientists have hypothesized that the land share on a planet 2.5 billion years ago was only 2-3%. If it is true, then the largest percentage of the Earth that was ocean is 98%. Also: According to the modern scientific views, the ocean ...


46

The Goldilocks zone ("Circumstellar habitable zone") is a real thing: In astronomy and astrobiology, the circumstellar habitable zone (CHZ), or simply the habitable zone, colloquially known as the Goldilocks zone, is the region around a star within which planetary-mass objects with sufficient atmospheric pressure can support liquid water at their ...


46

Yes, the 'ecological footprint' can be useful in suggesting areas where humanity has unsustainable practices which need to be improved. However, the footprint is usually presented in a very misleading way, as it dramatically oversimplifies sustainability and implies that all efforts to achieve sustainability are equal. If such a score was used as a basis ...


36

Well, the answer is that: Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space. -Douglas Adams, Hitchiker's Guide to the Galaxy Nothing else is visible in the frame simply because the angle of the image is too narrow to ...


35

A picture gives a sense of proportion. To the Earth, a rock diameter 13000km, clings a wisp of atmosphere. The troposphere, where everyone has ever breathed, is thinner than 20km. Above, space. The Internal Space Station orbits at about 400 km. THE THIN BLUE LINE: Earth’s thin atmosphere is all that stands between life on Earth and the cold, dark void of ...


31

There are two parts to this question: Does the Book of Job refer to a spherical Earth? If so, did it beat the other contenders to be the first to have the idea? Part 1 I don't propose to properly answer Part 1. This is a question for Hermeneutics.SE, not Skeptics.SE. I will note the obvious: the modern English translation provided is clearly not evidence ...


24

The article quotes a scientific paper as saying: Hansen and colleagues have estimated that Earth's actual average surface air temperature between 1951 and 1980 was approximately 287 K (14 degrees Celsius) (Hansen et al. 2010). The quoted paper Hansen et al. 2010 is confirming a study done back in 1999. For the sake of users who require an absolute global ...


23

The story is slightly less dramatic than it sounds. The runways themselves are not being "shifted" (i.e. construction crews getting out and laying tarmac), but just renamed and signposted. From a Livescience report Runways are designated according to the points on a compass, and the drifting magnetic north means that they, periodically, need to be ...


22

This is known as the Giant Impact Hypothesis or the "Big Splash". As remarkable as it sounds, it is actually is the scientific consensus of how the moon was formed. The Moon is generally believed to have formed from debris ejected by a large off-centre collision with the early Earth. A letter to Nature magazine, August 2001. More evidence for this ...


21

I've long thought this graphic gives a good idea of the issue The problem at an airport is variation in local magnetic declination, not the variation in location of the magnetic north pole. Due to local magnetic anomalies, magnetic compasses rarely point at any magnetic north pole. As others have noted, Runway naming is mostly based on local magnetic north ...


20

No, the Earth is not flat On Christmas Eve 1968, humans took this photograph of the Earth. The round profile in combination with the gradient and the half-ellipsis shape of the terminator, and the dark side of the Earth, are all consistent with the Earth being a spheroid planet. This photograph is incompatible with the notion of a flat planet. A few hours ...


19

To restate your question, How can we statistically describe the intervals between mega-volcano eruptions? Do they follow a particular probability distribution with known parameters? Can we use this to make any conclusions at all about Yellowstone? We know of three eruptions 2.1 million years ago (mya), 1.2 mya, and 0.64 mya. This is an interval of 900,000 ...


18

I think vartec has the best answer so far. The quoted tolerance (specifications link) of 0.005 is for total size, not smoothness. The spec says 2.25+.005, not +/-, is that a typo or does it mean the balls must be at least 2.25 but not more than 2.255"? Most balls are actually manufactured to a higher tolerance, with good ones being under 0.001". The pic ...


15

According to Essentials of Oceanography (2012) at page 13 The physical expanse and distribution of the early ocean is a matter of some controversy. Most researchers hold that masses of rock have always protruded through the ocean surface to form continents. However, some recent studies suggest that water may have covered Earth's entire surface for some ...


15

No, continental rocks are not the same as ocean floor. Continents are mostly made up of minerals like granite, which are lighter than ocean floor minerals like basalt (sima, short for Silicon/Magnesium). Continental material is mostly sial (short for Silicon/Aluminium) which is lighter. Partially molten mantle material is pushed up at mid-ocean ridges, ...


12

In addition to @hdhondt's answer (+1) The evidence for the existence of Pangea lies in the existence of matches between fossil records and rock formations in continents that are now thousands of miles apart, in addition to Wegener's observation that the (continental shelves) of the existing continents match quite closely like a jigsaw. If Pangea did not ...


11

The claimed air density is about 520 times higher than air denisty now. This means that, according to the ideal gas law, you need 520 times the air pressure - roughly 520 bar. Now the critical point of nitrogen (main consituent of air) is about 33bar, the critical point of oxygen about 50 bar. Both critical temperatures are far below 0°C. So at this density,...


11

Yes, based on modelling, the rotation of the Earth was slowed down by 0.06 microseconds per "day". That is, a day would be made about one seventeen millionth of second longer than it otherwise would be if the dam had not been built. Business Insider references NASA's Jet Propulsion Laboratory (JPL} - the original link is broken, but the JPL still ...


10

Esker has no evidence to support the idea of the Earths atmosphere being more dense in the Jurrasic than it is now, other than the assertion that dinosaurs are too large to have existed otherwise. However this assertion has little support, as evolutionary adaptions (such as the unidirectional breathing discussed in the previous question) are able to explain ...


10

What the text says There is an English translation of The Aryabhatiya with notes is available online. Regarding the spherical Earth, the text says (page 64 of the book) The sphere of he Earth, being quite round, situated in the center of space, in the middle of the circle of asterisms, surrounded by the orbits of the planets, consists of water, ...


10

The calculations leave out important factors as to why you can still see things lower than 300 feet. This is a replication of the Bedford Level experiment It's a well known, classic experiment done many times that is in no way shape or form "theoretical" If light traveling through the earths atmosphere actually moved in a perfectly straight line ...


9

By the very definition offered in the article: Geo means Earth and Patho means suffering. It means suffering from the earth which causes stress in the form of illness. The Earth has no nervous system and is not scientifically known to suffer, although we can certainly imagine it doing so. That's a feature of human psychology, which is what this boils ...


8

Yes, the Earth was entirely ocean before any continents existed. The continental crust started forming 3.7 billion years ago. The first "micro continents", even if they were tall enough to have dry land, would consist of islands - not a sizable barrier to make you consider dividing the ocean into different places around it. That is, even if you had some ...


8

Here is a paper which was written to refute Gentry's theory: "Polonium Haloes" Refuted A Review of "Radioactive Halos in a Radio-Chronological and Cosmological Perspective" by Robert V. Gentry by Thomas A. Baillieul Copyright © 2001-2005 [Last Updated: April 22, 2005] It introduces rocks as follows. About the Rocks Geologists classify ...


7

Radio-isotope dating is not just performed on meteorites, but also on terrestrial rocks. The dates obtained are consistent, with meteorites slightly older than the earth. Are you suggesting the earth was also formed with lead already present? Isochron dating avoids contamination problems. Meteorites are often dated by iscohron lead-lead methods, and hence ...


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