Moon question - daytime - please help.

[Steve Triberfan1]

Yesterday (Thursday) morning around 10AM we had a partly cloudy sky in Alliance Ohio... and noticed the moon through some clouds.

It appeared as a FULL moon. (supposed to be third quarter moon)

Once we viewed the moon about 45 minutes later (in clear sky) it was no longer appearing to be a FULL moon! 
QUESTION: is it possible for light to reflect off the clouds and back to the moon to make the moon appear to be full when is should only be in third quarter phase?  I am 67 years old, and never saw such a thing! Now I wish I had taken some pictures.

-steve/Triberfan
 

[Ghideon]

50 minutes ago, Steve Triberfan1 said:

is it possible for light to reflect off the clouds and back to the moon to make the moon appear to be full when is should only be in third quarter phase?  

Hello Steve. I'll try to answer the directions question and not speculate or try to explain the actual effect. 

I do not think that reflection of light off clouds is a plausible explanation for the observed effect. Some arguments:

-If it would be possible for reflective clouds to light up the dark area of the moon then the same effect would be observable when watching the moon from a snowy landscape. Snow has similar (or higher) albedo* and would reflect the same for more light from earth to moon.
-If the clouds would reflect enough light to lighten up the moon's dark parts then the effect would be visible also where there are no clouds straight above. Light hitting the surface of the moon is not reflected straight back only , it is reflected and spread at other angles as well. You would have seen a full moon also before and after the clouds passed. 

 

That said, earth does illuminate the moon slightly. But the light is much fainter than sunlight:

Quote

Even when the Sun isn’t out at all, there’s still plenty of light on the Moon’s surface thanks to the shining, reflected light from the Earth. It isn’t nearly as bright as sunlight; it’s about 10,000 times fainter. But the light from Earth’s surface, reflected back towards the Moon, can illuminate it all the same. This is why, when the Moon is in a crescent phase, you can still see features on the dark portion of the Moon: we call this reflected, illuminating light the phenomenon of Earthshine.

Source: https://medium.com/starts-with-a-bang/ask-ethan-how-bright-is-the-earth-as-seen-from-the-moon-627eb1554ca9

 

Wikipedia have some info on earthsine: https://en.wikipedia.org/wiki/Planetshine#Earthshine
Nasa page with some pictures and info: https://earthobservatory.nasa.gov/images/83782/earthshine 

 

*) Different types of clouds exhibit different reflectivity, theoretically ranging in albedo from a minimum of near 0 to a maximum approaching 0.8. Fresh snow up to 0.9. (https://en.wikipedia.org/wiki/Albedo)

 

Edited December 21, 2019 by Ghideon
added earthshine

[Steve Triberfan1]

Hello Ghideon,

Thanks for your help in trying to explain what happened. It was indeed an unusual experience.  I wish I had taken pictures to show everyone!

 

Also, I forgot to mention that the ground at our Alliance OHIO location was covered with snow too.... so maybe that effect, along with the clouds reflecting back to the moon.... gave us an appearance of a FULL moon.  Not sure.  Just sure what we saw.  It was an awesome experience!

-steve

[swansont]

10 hours ago, Steve Triberfan1 said:

Hello Ghideon,

Thanks for your help in trying to explain what happened. It was indeed an unusual experience.  I wish I had taken pictures to show everyone!

 

Also, I forgot to mention that the ground at our Alliance OHIO location was covered with snow too.... so maybe that effect, along with the clouds reflecting back to the moon.... gave us an appearance of a FULL moon.  Not sure.  Just sure what we saw.  It was an awesome experience!

-steve

Everyone would see it as full if that could happen, and it wouldn't be intermittent. As Ghideon has said, earthshine is too weak of an effect. 

[Ghideon]

13 hours ago, Steve Triberfan1 said:

I forgot to mention that the ground at our Alliance OHIO location was covered with snow too.... so maybe that effect, along with the clouds reflecting back to the moon.... gave us an appearance of a FULL moon.

I do not think that is a plausible explanation. Let's try some thought experiments to find arguments. This is provided as an example how you could probe this (and maybe other ideas):
1: Assume that clouds and snow in combination reflects more moonlight than snow or clouds in separation, enough to lighten up the dark areas of the moon. If that assumption is correct, how would the night-side of the earth, when lit by moonlight, look like from space ? If areas with snow and clouds are more reflective that snow or clouds there would be bright patches where snow is covered by clouds. I don't not think that matches what is actually observed. 

2: Assume that light from earth could make the dark area of the moon look as bright as the sunlit area of the moon (so that for instance a half moon looks like a full moon). How bright would the earth be when seen from the moon? Almost as bright as the sun?  I don't not think that matches what is actually observed.

3: Use the available incoming light from moon and assume that all of it is reflected back towards the dark area of the moon. Then calculate how much of that light that is reflected off moon again to be visible by an observer back on earth. The calculation would reveal that available light is not enough to make areas of the moon that is not lighten by sun look bright as the sunlit area. I think that this 3rd case could be generalized to mathematically support that reflections between two bodies could not possibly create the observed effect. The second reflection of the observed body will always be darker than the area where the first reflection occurs.

 

That said, I might speculate* a little about the observation. What happens when car headlights are visible through fog? The light is spread out and the amount of spreading depends on the amount of fog. If the car's headlights are not circular but in some other shape, is that shape visible through the fog? With the "right" amount of fog would the shape of the moon be obscured but the light still visible, spread out by the fog, so that the light source (moon) looks circular? The following picture does not necessarily support my statement, it just serves as an illustration: Does the car have circular or non circular lights?

 

 

*) I do not have time to track down any sources supporting my statements. Hence I stat it as questions and not claims and label it speculative at this point.

[Strange]

 

13 minutes ago, Ghideon said:

That said, I might speculate* a little about the observation. What happens when car headlights are visible through fog? The light is spread out and the amount of spreading depends on the amount of fog. If the car's headlights are not circular but in some other shape, is that shape visible through the fog? With the "right" amount of fog would the shape of the moon be obscured but the light still visible, spread out by the fog, so that the light source (moon) looks circular? The following picture does not necessarily support my statement, it just serves as an illustration: Does the car have circular or non circular lights?

That is pretty much what I was about to suggest as well. Maybe also combined with an ice halo, which would always be circular (although much larger than the moon).

[Ghideon]

On 12/21/2019 at 4:21 PM, Strange said:

Maybe also combined with an ice halo, which would always be circular (although much larger than the moon).

That comment made me think in another direction. Could a moon dog* be mistaken for the moon itself? If there are partial clouds and the exact location of the moon on the sky was not known or measured?
Light pillars** are also a related phenomenon.  

Once OP is back maybe some details could be clarified:

-What was the apparent size of the full moon behind the clouds vs the size when sky was clear?
-Was it a fuzzy blob behind clouds or a sharp circular shape?
-Are we 100% sure the object was the moon and not some other object or phenomenon? Just to be clear, Im not talking about flying saucers. Over here we have had light shows etc that could look strange from a distance. Below is an example from London (I hav not had time to find a local photo) 

 

*) https://en.wikipedia.org/wiki/Moon_dog

**) https://en.wikipedia.org/wiki/Light_pillar

 

[Strange]

12 hours ago, Ghideon said:

-Are we 100% sure the object was the moon and not some other object or phenomenon?

It did cross my mind that (depending on the thickness of the clouds) that it could have been the Sun. But I imagine the OP knows the relative positions of the Sun and Moon at that time of day! I suppose it might catch someone out if they weren't sure where they were/which way they were facing.