Hot answers tagged

39

Smoke. There was significant smoke across the USA, which attenuated the light from the sun/moon due to increased scattering. The smoke particles effectively cause the light to reflect in different directions, so you see more colors. See below for the HMS Smoke Polygons for the day, which clearly shows smoke over your region from the intense smoke/wildfire ...


22

Absolutely not. First of all, "rare earth magnet ore", meaning the ores of metals like neodymium (Nd) and samarium (Sm), is not magnetic at all. It only becomes a magnet once you make a magnet out of it. For example, one such magnet is Nd2Fe14B and it only becomes a magnet after neodymium is combined with iron and boron. Naturally occuring neodymium ore ...


20

Is there geological (or other physical) evidence here on Earth that confirms the moon once collided with the Earth? No, there isn't. This is, however, plenty of evidence that the moon formed due to a collision of a third body (sometimes referred to as Theia) with the Earth, and the moon formed from the ring of debris that resulted from the collision. This ...


11

The Moon is not "full" of helium-3. 3He is at most fifty parts per billion of the lunar regolith1 and that "high" concentration pertains only to permanently shadowed craters. The Moon is bombarded by a steady stream of helium-3 while sunlit. Some of this incoming helium-3 is temporarily embedded in the lunar regolith. Without this steady supply, the helium-3 ...


11

No. Cosmic radiation are high-energy particles that create particle showers high up in the terrestrial atmosphere. Those particle shower are heavily beamed downwards, and although in principle some secondary shower products feel the local magnetic fields, effectively are not affected by the natural terrestrial field, let alone weaker local fields. Those ...


9

This is based on the overly-simplified model of tides being the result of tidal bulges. As I explained in my answer to a related question on the physics.SE sister site, those tidal bulges do not and cannot exist. Instead, the tides are dynamic responses to the tidal forcing functions from the Moon and the Sun, with the orbits of the three bodies about one ...


8

The composition of Moon rocks is pretty much the same as that of Earth. However, none of the processes that concentrate specific minerals in one location (i.e. into a mineral deposit useful for mining) exist on the Moon. This is due to the lack of tectonic activity. Therefore in the Moon you would expect the rocks to be much more homogeneous than on Earth. ...


7

Yes. The moon is lit by the sun, so as its position relative to the sun changes, so does the angle from which it is lit. I recommend reading the Wikipedia page on lunar phase for a good overview, some data, and some good references. This diagram from that page more or less sums it up — the bottom row shows how the moon looks from the earth over the course ...


6

It depends on the season and even more on latitude. At any given time, the same side of the Moon faces the Sun. Where you stand on Earth doesn't change which part of the Moon is lit, but if you think about the orientation of people on the earth, people in the Northern and Southern Hemisphere are "upside down" to each other and people on the equator are ...


6

It is unlikely anything other than salt would be derived from sea water. The largest deposit of gold is dissolved within the worlds oceans - in terms of tonnes of metal. The problem with extracting the gold from sea water is the concentration is so low it is uneconomic to do so. It's why we keep mining hard rock sources of most metals. This problem exists ...


5

The single biggest difference is the lack of chemical weathering in lunar soils which are subject to physical weathering almost exclusively. If you exclude biological processes, terrestrial rocks undergo significant weathering from water and atmosphere, which the moon lacks. For example, both earth and moon contain feldspar-rich rocks, however, clays, the ...


5

What is the Moon's distance from viewer at horizon? As noted by others, the moon follows an elliptical orbit, which will lead to the greatest change in distance regardless of the observation angle. However, we can place some upper and lower bounds on what the distance at the horizon would be by using the maximum and minimum orbital radii (the apogee and ...


4

Just a shot in the dark, as the journal in which this article has been published has no online presence and is not available in paper form in my institution, but it might refer to an article by a Richard L. S. Taylor from 1990 called 'The Damocles Hypothesis', published in the journal "Space" (journal edited by the University of London it seems). Follows ...


4

The Moon's orbit is elliptical, not circular, and the maximum and minimum distance from the Moon to the center of the Earth (apogee and perigee, 405,385 and 363,630 km respectively) are much larger than the radius of the Earth (6370 km). Therefore, the distance you are asking for is very variable and it does not depend so much on the position of the Moon ...


4

This has sat untouched for a while, so I did a quick search and found this article which sums it up nicely. They key factors with regard to earth science would be: 1) Less extreme tides. The tides would only be linked to the sun and would not be as strong. They would also peak at noon. This has obvious implications for any coastal processes that rely on ...


4

Yes, earthshine is completely normal. It is simply illumination of that part of the moon that is facing away from the sun. This illumination is sunlight that is reflected towards the moon by the Earth. Strictly speaking, it is that reflected light from the Earth that is itself reflected back to Earth so that we can see it. The intensity of Earthshine is ...


4

I'd like to expand on jamesqf's answer. But first, lit side of the moon and the dark There are no "lit" and "dark" sides of the moon. It rotates, and whatever is dark now will be lit in two weeks time. There are definitely near and far sides of the moon though. The problem with the Earth is that it's a dynamic planet with plate tectonics, continental ...


4

There are craters on the Earth, Arizona's Meteor Crater being perhaps the best-known example. The reason that there aren't a lot more (obvious) ones is that the Earth has lots of dynamic processes, ranging from weather to plate tectonics, that gradually erase them. The Moon doesn't have these things, so craters last for billions of years.


4

Even in the exosphere, at 1800 deg centigrade, the only components of the Earth's atmosphere that can currently attain escape velocity are hydrogen (3 kg per sec), and and helium (next to nothing). The notion that the Earth's atmosphere would be stripped away by solar wind but for the protective magnetic shield, is a myth. So there is no 'characteristic time ...


4

The apparent angle of the moon is a function of the 28-day lunar orbit, the time of day/night one is looking at the moon, and the latitude from which it is viewed. So, for example, the current (14 May 16) view of the moon is that it is on its side, 'boat shaped' on the equator, but will appear progressively more sideways the further towards the poles that it ...


3

You can think of it as the "reverse" of moonshine. When you walk outside at night and there's a full moon, you can actually see quite a lot around you. Same thing - this happens on the moon when there's a "full earth" that lights up everything around. And since you're on earth, you see this from the outside, on the moon.


3

Melting lunar dust of basaltic composition will result (unsurprisingly) in basalt lava. There might be some volatile loss - if for some reason the basalt had some H2O or CO2 trapped in the solid you will most likely lose it. It's probably not going to change its chemical properties much though. On Earth, as lava cools down fast, for example when it's ...


3

Here's a quick-and-dirty estimate. The gravitational self-energy of a uniform-density sphere is $$ U = \frac35 \frac{GM^2}R $$ Let's assume Theia had the same mass and density as Mars, and that Gaia contained the rest of the mass of the Earth-Moon system. The binding energies for the four bodies are then theia/mars 4.82e+30 joules gaia 1.90e+32 ...


3

As noted in comments, the earth rotates on its axis in about 23hrs 56 minutes. This is known as the sidereal day, that is, the day with respect to background stars. (that's not quite true, but it's good enough unless you're dealing with periods of thousands of years with high accuracy - see the linked wiki article if you care about the detail). At the same ...


3

It appears the Earth's magnetotail, which is a part of its magnetosphere, is on the Earth's nightside; lengthwise exceeds 6,300,000 kilometers (3,900,000 miles); and is the furthest known observable feature of Earth. I am unable to explain why is it commonly not included in the "spheres" of Earth Science. Note: The gravitational pull of Earth in theory ...


3

Which Earth minerals would Moon colonists miss the most? tl;dr All of them. As mentioned in the other answers here, it's about economics. Extracting an element from a mineral requires energy, chemical processes, equipment, waste management, etc. This has to be done per amount of rock. The more of the element in interest you have in your rock, the more ...


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