Moon unusually bright - why?

Over the past couple of nights I have noticed that the moon seems unusually bright - real searchlight bright, so that it’s difficult to pick out the craters because of the glare.

I also note that there is a lunar eclipse coming up this weekend. My question is - are these two phenomena related? Thinking about the geometry, if the moon is about to enter the earth’s umbra, then it must currently be almost directly opposite the sun from the Earth. In which case, reflected light is coming as near as possible “straight back at us”, maximising reflectivity as we get to see all the bright bits, and not the shadows thrown by the surface irregularities.

Does this make sense? Is it a recognised phenomenon? Or are my eyes deceiving me? My brain can’t work out whether the moon is currently “more aligned” in any real sense than a regular full moon.

According to Larry Niven’s “Inconstant Moon” (made into an episode of “The Outer Limits”) it means that the sun has gone supernova, and the other side of the earth has been destroyed. You have a few hours until it reaches your side of the earth, at which point you’ll fry too.

Good luck.

(I also recall the story stating it could have been a really large solar flare. That’s possibly more likely.)

The moon rides higher in the sky in fall and winter. That reduces atmospheric scattering, and makes the moon appear brighter and more silvery.

Shoot! I opened this thread to post a reference to the Niven story! I even remembered the title without resorting to a web search. (And ISTR that in the story, the sun had gone nova.)

It is most likely that you are just noticing the effects from Squink’s words as we come out of the summer months (assuming you are located north of the equator) when the moon takes a lower path in the nighttime sky only. (The moon can be out during the day, too, you know.) Perigee can increase the moon’s brightness, and its effects are most noticed during the full moon phase.

While there is an upcoming lunar eclipse, the alignment is subtle. Besides, to get the most direct moon rays, you’d have to be located in the Tropics. By the time of this lunar eclipse, the moon will be positioned just above the celestial equator - in Aries*. In brief, this means those residing just north of the equator would receive direct rays…only and only when the full moon culminates on the meridian (at the peak of its path across the sky). …assuming the full moon is not in eclipse at that time!

*FYI: Aries used to lay on the celestial equator, for those who may have been aware of this fact. But, it shifted due to the earth’s “wobble” (precession of the axis)…skipping more detail.

Hope that sheds some light on the question…

  • Jinx

Thank you MattTheCroc!

Very weird… I read that Larry Niven story probably 20 years ago, not thought of it since… until this morning when reading about the current solar activity (which perhaps contributes to the current bright moon?). I was trying to remember what the story was, and hey presto, in you stepped :slight_smile:

By the way…I agree with you, I remember it as that the sun had not gone Nova, it was ‘merely’ a huge flare…

Another effect is that the Moon, for some reason I don’t know, reflects light preferentially straight back in the direction it came from. An effect of this is that (so I’ve read) the full Moon is *ten times brighter * than the half Moon. You can also see in some Apollo lunar surface photos, that the terrain surrounding an astronaut’s shadow is much brighter than that farther away.

This looks similar to the effect where sunlight is reflected back off morning fields, but this is due to the shape of water droplets, and I’m sure that’s not the reason.

But I think because of this, the brightest Moon would be one that’s just barely outside the Earth’s shadow. But since it’s a couple of days before opposition, the atmospheric scattering explanation sounds more likely.