What is Lunar: Definition and 113 Discussions

A lunar eclipse occurs when the Moon moves into the Earth's shadow. This can occur only when the Sun, Earth, and Moon are exactly or very closely aligned (in syzygy) with Earth between the other two, and only on the night of a full moon. The type and length of a lunar eclipse depend on the Moon's proximity to either node of its orbit.A totally eclipsed Moon is sometimes called a blood moon for its reddish color, which is caused by Earth completely blocking direct sunlight from reaching the Moon. The only light reflected from the lunar surface has been refracted by Earth's atmosphere. This light appears reddish for the same reason that a sunset or sunrise does: the Rayleigh scattering of bluer light.
Unlike a solar eclipse, which can only be viewed from a relatively small area of the world, a lunar eclipse may be viewed from anywhere on the night side of Earth. A total lunar eclipse can last up to nearly 2 hours, while a total solar eclipse lasts only up to a few minutes at any given place, because the Moon's shadow is smaller. Also unlike solar eclipses, lunar eclipses are safe to view without any eye protection or special precautions, as they are dimmer than the full Moon.
For the date of the next eclipse, see § Recent and forthcoming lunar eclipses.

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  1. D

    I Lunar Slingshot Maglev: NASA's Energy Savings for Mars & Beyond

    Has NASA considered building a maglev on the moon so we can use the lunar mass and momentum to gain higher energy savings for missions to Mars and beyond? A spacecraft can be catapulted toward the destination with its rocket engines off and only turn them back on to course correct or slow down...
  2. S

    I Gas Density of Lunar Crater Rims: Comet vs. Asteroid Impacts

    I mean - when they form. What are typical gas densities at lunar crater rim when the crater is made by a comet? An asteroid? Both a comet and an asteroid, hitting Moon at several km/s, initially heat up to several thousand K, and even asteroid produces some vapour... at hypocentre. However, by...
  3. O

    I Is the eccentricity of the lunar orbit constant?

    The wikipedia article on Lunar distance contains a confusing graph. The graph seems to suggest that the eccentricity of the lunar orbit is maximal in january and ~july, and minimal in april and ~october. I think the eccentricity should be constant. Is wikipedia right or wrong, or is there some...
  4. W

    B Lunar libration time lapse with real photographs?

    I have been trying to find a time lapse animation showing lunar libration made of actual real photographs of the Moon. However, no matter how much I search, I can only find computer-rendered animations. Does anybody know of a video made out of actual photographs of the real thing?
  5. genxium

    I Solving Sub-Problem for OpenAI Lunar Lander v2: Seeking Advice

    I'm currently working on a pet project which is similar to the OpenAI Lunar Lander v2 (hence the problem is in a 2D context), and seeking help for a sub-problem that's been blocking me for a while. At any instant of time, I'm to find Fe: magnitude of main engine thrust, must be >0 Fs...
  6. D

    I Simulation debugging for Apollo Lunar Landing

    My simulator is trying to mimick the actual conditions of the Apollo landing. I have entered in numbers for my runge kutta simulator for LEM mass, dry mass, fuel, thrust of the rockets, fuel burn rate per second etc etc. But I am not able to land, only very close to landing. I copied the...
  7. T

    B Delta-v from Lagrange points to lunar surface?

    What is the delta-v requirements from each of the Earth-Moon lagrange points to landing on the lunar surface? What would be the best software I could use to visualise and calculate that kind of thing? Thanks.
  8. lomidrevo

    B Lunar Crater Radio Telescope (LCRT)

    https://www.sciencealert.com/check-out-this-amazing-plan-to-turn-a-crater-on-the-far-side-of-the-moon-into-a-radio-telescope Original article from NASA: https://www.nasa.gov/directorates/spacetech/niac/2020_Phase_I_Phase_II/lunar_crater_radio_telescope/
  9. Glenstr

    I Objects flying over the lunar surface

    This video has been popping up in my feeds over the last day or so, as I'm sure others here have also seen it by now. Looks like it has been taken with one of these super zoom cameras. After watching it carefully several times, it doesn't appear to be done with creative video editing, which I...
  10. S

    I Uncovering the Mystery of Lunar Perigee Frequency | 2020 Insights

    Hello- I was looking at a table of the dates of lunar perigees for 2020, and I noticed that most of the perigees were between 27 and 29 days apart. So the perigees do not appear at a constant frequency, which I did not expect. There are even a pair, between June 30 and July 25, which are...
  11. russ_watters

    Stargazing Potential Impact of Meteoroid During Lunar Eclipse on January 21, 2019

    Anyone else watching the lunar eclipse tonight? It starts at about 9:30PM EST, with totality at 11:41. It's cold and windy in PA, but at least it's mostly clear. Here's a couple of pre-eclipse photos:
  12. Chatterton

    Writing: Input Wanted Lunar Orbital Rings: Calculating Height and Rotation for Earth-like Gravity

    I'm working on a story set on the moon post-industrialization. The moon has an orbital ring with a spinning exterior to simulate Earth gravity. People work on the surface in lunar grav, then go up to live on the ring under conditions more favorable for human bodies. Two questions I need to...
  13. Mikaelochi

    B A Question Concerning Lunar Eclipses and Aristarchus's Work

    I have recently been reading To Explain the World: The Discovery of Modern Science by Steven Weinberg. I am currently in the midst of Chapter 7, Measuring the Sun, Moon, and Earth. On Page 66, Weinberg comes to "what in some respects is the most impressive example of the application of...
  14. J

    Can total lunar eclipse and partial lunar eclipse happen at the same time?

    Can total lunar eclipse and partial lunar eclipse be happened at the same time? So, do we call it partial lunar eclipse when the total lunar eclipse happen just before?
  15. F

    I Lunar apsidal precession relative to equinox

    The period of the lunar apsidal precession is about 8.8506 years measured against fixed starts. How can I accurately convert this to the period between alignments with spring equinox? Thanks.
  16. Charles Link

    B Tonight's full moon and lunar eclipse

    Hello, I don't see any other post about tonight's full moon and lunar eclipse, so I thought I would mention it.
  17. J

    I Reference point of geocentric lunar latitude?

    I'm attempting to use an algorithm translated from Jean Meeus: Astronomical Algorithms. The algorithm in question finds a geocentric position of the moon given a certain day. I have been able to find the geocentric longitude of the moon, but I don't know what this longitude is in reference to...
  18. A

    I Length of lunar month immediately after moon's formation?

    Does anyone know how long the lunar month was when the moon was formed? I can't get the equation to work. I'm looking for speed of the moon when it was created at about 1/10th the current distance from the earth. Thanks.
  19. A

    I Could ice exist in Lunar lava tubes?

    http://en.wikipedia.org/wiki/Lunar_lava_tube Given that they are expected to be at about -20C and parts of them will be in permanent darkness. If ice can exist at the Lunar poles: http://nssdc.gsfc.nasa.gov/planetary/ice/ice_moon.html then why not there? If water molecules migrate from the...
  20. Charles Kottler

    B Is a lunar space elevator a realistic proposition?

    I recently came across this article (from 2005) outlining a proposal for a lunar space elevator: http://www.niac.usra.edu/files/library/meetings/fellows/mar05/1032Pearson.pdf Their is nothing in the article which stands out to me as being unrealistic, although the cost estimate ($10B) might...
  21. G

    I Lunar versus Solar orbit at solstices

    Disclaimer: The questions below were raised by an article that's most definitely pseudoscience. The questions themselves have nothing to do with what makes it "pseudo", though, so don't let that put you off, please. :)Quoting from [crackpot link removed by mentor] (I'd advise you only to read...
  22. G

    Determining the surface area on a 5 sided lunar esque shape

    Homework Statement I'm trying to figure out the surface area on a 5 sided shape where the sides can all be modeled by "lunes". The shape will end up looking like a banana peel. We are modeling the sides of the shape as lunes with varying angles on a sphere of radius 3 inches. I'm trying to...
  23. Greg Bernhardt

    Insights What Can You Learn About the Moon?

    Greg Bernhardt submitted a new PF Insights post The Moon Quiz Continue reading the Original PF Insights Post.
  24. Z

    B Are Lunar Phases Affected by Earth's Orbit and Rotation?

    My first question is: Shouldn't the lunar phases be thrown off by Earth's orbit of the sun? As in, after 6 months of orbit, since we are on opposite sides of the sun, the phases would be reversed so that the moon being in the same position relative to the Earth as it was before the 6 months...
  25. C

    Why Does the ELP2000-82b Lunar Theory Differ from Jean Meeus' Adjustments?

    Good morning, I was wondering if someone can help me in this subject. I recently programmed the entire ELP2000-82b lunar theory in a dll. My problem is the reduction of the obtained positions to the mean equinox of date. The theory is referred to the ELP2000 inertial frame. A simple adjustment...
  26. F

    What is the cause of variations in lunar eccentricity?

    I'm still working on understanding some of the subtleties of the lunar orbit. We know that the lunar nodes ( where the lunar orbit crosses the plane of the ecliptic ( a cryptic term for the plane of the Earth's orbit.)) shift progressively and complete a cycle in 18.61 years: the period of...
  27. F

    A What is the cause of lunar nodal and apsidal precession?

    Over the last year or so I've been doing quite a bit of reading trying to find out what is actually causing lunar nodal precession. There seems to be a lot of handwaving but no definitive answer, which I find rather odd. Maybe I've just not found the right source. Google seems obsessed with...
  28. pioneerboy

    Lunar and Planetary Laboratory vs. Steward Observatory

    Hi there, The University of Arizona has these two institutes (among many others, of course): - Lunar and Planetary Laboratory, LPL for short - Steward Observatory As far as I understand, both are into space research and astronomy. If I wanted to join either one or the other, I would have no...
  29. H

    Lunar super eclipse Sept. 27th. 2015

    Below is the link to the Lunar super eclipse Sept. 27th. It won't happen again until 2033. http://finance.yahoo.com/news/theres-rare-supermoon-total-lunar-205421688.html?amp;soc_trk=ma&soc_src=mail&soc_trk=ma
  30. D

    What is the mass of the lunar lander using the PhETLunar Lander applet?

    Homework Statement Using the PhETLunar Lander applet, we are to find the mass of the lunar lander. We know the maximum acceleration of the module's engines and gravitational acceleration of the moon. Homework Equations F=ma mgh=1/2mv^2 f*t=p The Attempt at a Solution Everytime I try to...
  31. WHT

    Do lunar forces have more of an effect than we know?

    Head's up, as this scientific finding is making the rounds. http://www.cnet.com/news/the-moon-is-shrinking-and-the-earth-is-shaping-it/ The claim is that the oriented gravitational pull shapes the landscape of the moon. Except for the established effect of tides, it's odd that scientists do...
  32. C

    Lunar and Solar eclipse - same times a year?

    Hi, Just wondering: The lunar orbit around the Earth is tilted 5.1 degree with respect to the Earth's orbit around the sun (as described in the video), so only at 2 times during the year the Earth is aligned with the sun such that lunar eclipses can happen IF the moon is behind the Earth...
  33. davenn

    Nice lunar and planetary conjunction

    the Moon is currently very close to Venus and Jupiter in the sky this pic I did last nite 20-6-2015 Tonite the Moon will have moved eastwards ( to the right) and will be directly above Jupiter cheers Dave
  34. C

    ELP82b / Lunar tables doubt....

    Hi, I'm programming a simple DLL to use VSOP87 and ELP82b. I can get the correct x,y and z values without a problem referred to J2000, I think. But I'm getting a constant error when applying the correction for the nutation and precession in ELP82b. Actually, I'm getting even worst values than...
  35. L

    Lunar lander velocity before hitting ground

    Homework Statement A lunar lander is descending toward the moon's surface. Until the lander reaches the surface, its height above the surface of the moon is given by y(t)=b−ct+dt2, where b = 770m is the initial height of the lander above the surface, c = 62.0m/s , and d = 1.02m/s2 . Part B...
  36. davenn

    Total Lunar Eclipse 8th Oct 2014

    hi guys and gals a total lunar eclipse will be visible for all Pacific and parts of it for most of USA parts of South America, Central Asia cheers Dave
  37. T

    Help: Projectile Motion with Forces Problem -- Lunar Lander

    1. I have a physics problem that I am having trouble understanding. Here it is: Your lunar lander (with fuel and crew) has a mass of 14,700 kg. It is initially in a circular orbit around the Moon (i.e. Viy = 0 m/s) at an altitude of 30 km above the lunar surface. To land on the Moon, you...
  38. D H

    Simple explanation of the lunar highlands problem

    Why does the farside of the Moon have a thick crust with a landscape dominated by lunar highlands while the nearside has a much thinner crust with a landscape dominated by maria? This is what the authors of a paper recently published on the arxiv (and accepted for publication in the...
  39. C

    Lunar Eclipse: Umbra and penumbra radii

    Homework Statement Find the radii of the umbra and penumbra circles drawn drawn perpendicular to the EMS axis, formed at a distance equal to that of the moon from the Earth. Homework Equations (From: http://www.opticiansfriend.com/articles/equations.html#Shadows) D2 / L1 = (P + U) /...
  40. C

    Mass attenuation problem, protecting the lunar base against radiation?

    Homework Statement To protect the lunar base against space and sun radiation, astronauts covered it with 4m thick layer of regolith (moon soil). However, they found that they level of radiation was still 50% higher than on the Earth's surface, which they want to match. How many more meters of...
  41. jhae2.718

    Lunar Atmosphere Dust Environment Explorer

    LADEE, the Lunar Atmosphere Dust Environment Explorer, is set to launch tomorrow from NASA Wallops Flight Facility on an Orbital Sciences Minotaur V launch vehicle. It's a neat mission with some good science on it. Launch is scheduled for tomorrow, Sept. 6, and will be shown on NASA TV...
  42. jim mcnamara

    New lunar mascon model proposed

    http://www.sciencemag.org/content/early/2013/05/29/science.1235768 This is the result of fine-grained mapping of the gravity anomalies on the moon. They propose a bulls-eye model of impacts to account for the anomalies. I'm not competent to judge. The idea appears interesting to me.
  43. G

    Are lunar landings without chemical rockets possible?

    If a satellite tries to land on the moon without rockets to counter the force of gravity, it comes in too fast and crashes into the surface destroying itself. A satellite would be orbiting at approximately 1.8 km/s or so at a 50km altitude, and come in for landing from that height which would...
  44. karush

    MHB Lunar Gravity velocity on impact

    Lunar Gravity, On the moon, the acceleration due to gravity is $-1.6m/s$ . A stone dropped from a cliff on the moon and hits the surface of the moon $20s$ later. How far did it fall? What is the velocity at impact.? well here I presume since the rock is just dropped that $v_0=1.6m/s$ but the...
  45. S

    Stargazing Solar and Lunar Eclipse - size of moon

    If during a solar eclipse the moon tapers one moon diameter, wouldn't a lunar eclipse taper one Earth diameter?
  46. D

    Lunar Lander Formulas for Fuel / Masses

    Homework Statement I am currently working on a computer science program which calculates the landing of a craft on a given planet. The user will enter in various known variables. I need some direction on what formulas to use for my program. I am strong in computer science however I...
  47. M

    Is lunar effect on humans lunacy?

    I have done some reading, and found articles with little to no references (to scientific journals) that proclaim that although humans are mostly water...the moons gravitational pull has very little, if any, effect on our bodies. I don't believe that there is more crime during full moon's, for...
  48. M

    Designing an Effective system for lunar robots

    I am interested in knowing a little bit more on what would be the wisest way to create a lunar robot with the proper shielding for lunar conditions to do things like mining and lunar exploration. Also what kind of batteries would be best for these conditions? Also, say that there are robots...
  49. M

    Effects of Solar Flares on the Moon and Equiptment used for lunar exploration

    I would like to know what the effects of a solar flare would be on equiptment used for lunar exploration, say a robot to be specific. What kind effects would this have on the electrical system? I also read a NASA article describing a large solar flare that created a long enduring proton...
  50. J

    Stargazing Ever wonder what happens during a lunar eclipse?

    Being on the east coast of the US, I won't be able to see it. Those on the west coast will though. Here is how it will happen. Once in a blue moon, the Earth darts out of its orbit temporarily and blots out the sun. When that happens, you can see all of the sunsets on the Earth reflected off the...