# Which phases of Earth's moon (if any) would we see from Mercury? **URL:** \ **Category:** Factual Questions\ **Created:** [October 26, 2021, 3:59am UTC](https://boards.straightdope.com/t/which-phases-of-earths-moon-if-any-would-we-see-from-mercury/953212 "2021-10-26T03:59:53Z")\ **Posts on this page:** 6\ **Page:** 2
**Author:** ![garygnu](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garygnu/32/2924_2.png) [@garygnu](https://boards.straightdope.com/u/garygnu)\ **Post date:** [October 28, 2021, 2:22am UTC](https://boards.straightdope.com/t/which-phases-of-earths-moon-if-any-would-we-see-from-mercury/953212/21 "2021-10-28T02:22:37Z")
Would an observer on Mercury ever be witness to a lunar eclipse? I’d imagine both inner planets would be able to see them if the alignments work out. ---
**Author:** ![UDS1](https://avatars.discourse-cdn.com/v4/letter/u/e47774/32.png) [@UDS1](https://boards.straightdope.com/u/UDS1)\ **Post date:** [October 28, 2021, 2:34am UTC](https://boards.straightdope.com/t/which-phases-of-earths-moon-if-any-would-we-see-from-mercury/953212/22 "2021-10-28T02:34:45Z")
You mean, could they see a lunar eclipse occurring on Earth? Could they see the shadow of the moon projected onto the surface of Earth? In principle, yes, they could, if they had sufficiently powerful telescopes. ---
**Author:** ![Saint\_Cad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saint_cad/32/18907_2.png) [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)\ **Post date:** [October 28, 2021, 2:41am UTC](https://boards.straightdope.com/t/which-phases-of-earths-moon-if-any-would-we-see-from-mercury/953212/23 "2021-10-28T02:41:46Z")
> [@garygnu](#): > > Would an observer on Mercury ever be witness to a lunar eclipse? Why not? [We can see those on Jupiter](https://www.space.com/6705-moon-shadows-jupiter.html) with ground-based telescopes. In fact, the first measurements on the speed of light came from observing the transits of Jupiter’s moons. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [October 28, 2021, 12:05pm UTC](https://boards.straightdope.com/t/which-phases-of-earths-moon-if-any-would-we-see-from-mercury/953212/24 "2021-10-28T12:05:22Z")
> [@garygnu](#): > > Would an observer on Mercury ever be witness to a lunar eclipse? I’d imagine both inner planets would be able to see them if the alignments work out. I’m fairly sure the answer is yes. A couple other people answered for solar eclipses. A lunar eclipse is when the moon is eclipsed. Those would not be visible when Mercury and the Earth are at or near conjunction (when they’re more or less lined up with the sun), but at greatest extension, they should be visible. ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [October 28, 2021, 6:18pm UTC](https://boards.straightdope.com/t/which-phases-of-earths-moon-if-any-would-we-see-from-mercury/953212/25 "2021-10-28T18:18:56Z")
Yeah; I just checked the May 2021 lunar eclipse in Celestia, and the eclipsed Moon is clearly visible from Mercury, although it would be much dimmer (and redder) than usual. ---
**Author:** ![pmwgreen](https://avatars.discourse-cdn.com/v4/letter/p/edb3f5/32.png) [@pmwgreen](https://boards.straightdope.com/u/pmwgreen)\ **Post date:** [October 30, 2021, 10:22pm UTC](https://boards.straightdope.com/t/which-phases-of-earths-moon-if-any-would-we-see-from-mercury/953212/26 "2021-10-30T22:22:19Z")
> [@UDS1](#): > > But an observer on the other side of the moon, looking from the same direction as the sun is shining, would obviosly see the wholly illuminated other side of the moon - a full moon. I don’t know why nobody apart from you has mentioned this; while the view from Mercury is always a full or near full moon, the observer will get to see all sides of the moon, including the confusingly named “dark side”, invisible from Earth. [Previous page](https://boards.straightdope.com/t/which-phases-of-earths-moon-if-any-would-we-see-from-mercury/953212.md?page=1)