How Can You See the Sun and the Moon at the Same Time?

by Ray Sanders on September 19, 2011

Want to stay on top of all the space news? Follow @universetoday on Twitter

A daytime Moon over New Zealand in August 2010. Credit: NASA/Phil Davis

Did you know that you can see the Moon during the day?

Many people only notice our Moon at night, when there is considerably more contrast between the Moon and the night sky. Being the second brightest object in the sky (after the Sun, of course) and with Venus visible during the day to trained eyes, it’s no real surprise that the Moon is visible during the day.

Why then, do so many people act surprised when they notice the Moon during the day? What makes it possible for the Moon to be visible during the day?

Understanding how and when you can spot the Moon is a matter of knowing the different lunar phases, specifically the relationship between the Sun, Earth and the Moon during each phase. The image below shows the simple geometry responsible for each of the Moon’s distinct phases.

In the diagram it’s pretty easy to see that when Earth is between the Sun and the Moon, we see a full moon. When the Moon is between Earth and the Sun, we see a new Moon. The other phases are simply transitions from new to full and from full back to new.

Schedule of Moon Phases. Times shown indicate when the moon is overhead.

Schedule of Moon Phases. Times shown indicate when the moon is overhead.

Based on the orbital geometry of the Moon, there will certainly be times where the Sun will partially illuminate the Moon, during the day and at night. What makes the lunar cycle even more interesting is that the moon rises about an hour later each day, and yet invariably, a full moon rises near dusk and sets near sunrise. The reverse is true in that a new moon rises near sunrise and sets near dusk.

Looking at the above diagram though, a question comes to mind…
Why don’t we have a lunar eclipse during each full moon, or a solar eclipse each new moon?

I’ll explain the conditions needed for a solar or lunar eclipse in an upcoming article.

In the meantime enjoy the transition from waning gibbous to waning crescent over the next week and get your telescopes out during the weekend of the 25th. The Moon will almost be at its new phase.

If you’d like to learn more about moon phases and when the moon will be visible in your area, the US Naval observatory has a great calculator at: http://aa.usno.navy.mil/data/docs/RS_OneYear.php

About 

In addition to being a published astronomer specializing in variable stars, Ray Sanders has blogged for Universe Today, and The Planetary Society blog, among others. He runs his own blog, Dear Astronomer, teaches classes for CosmoQuest, and is a NASA/JPL Solar System Ambassador.

Anonymous September 19, 2011 at 2:27 PM

I just got a $827.89 iPad2 for only $103.37 and my mom got a $1499.99 HTV for only $251.92, they are both coming tomorrow. I would be an idiot to ever pay full retail prîces at places like Walmart or Bestbuy. I sold a 37″ HTV to my boss for $600 that I only paid $78.24 for.
I use http://alturl.com/qeff9

Anonymous September 19, 2011 at 2:42 PM

SPAM!

IVAN3MAN_AT_LARGE September 19, 2011 at 8:25 PM

Yo Ray, according to the IAU Style Manual, the astronomical object Sun should also be capitalized.

Ray Sanders September 19, 2011 at 10:41 PM

Ivan, we use a different style guide, but I did look it up and you are right.
I usually follow the rule of “If in doubt, leave it out” ;-)

Anonymous September 20, 2011 at 7:02 AM

The Capital S for Sun, M for Moon, E for Earth seems to be modern English, the lower case initial letter seems to be old English (according to the old astronomy books in my library) or modern American.

Queequeg de la Pequod September 19, 2011 at 9:46 PM

Hi friend, there is the other half of the story when you can see the Moon in daytime. Time is at new Moon around noon, but when the Moon is around 10-degrees from the Sun (so you will not be overly blinded). Cover the Sun with your hand, or don’t. This is best done on a clear day. With a little practice, the new Moon can be seen with the naked eyes. (Hint: Earthshine.)

Ray Sanders September 19, 2011 at 11:25 PM

Queequeg – I’ve been a backyard astronomer since childhood. My “holy grail” list is to do the entire Messier Marathon and view Venus and Jupiter in broad daylight. I’ll have to add viewing the new Moon during the day to that list too.

Gadi Eidelheit September 20, 2011 at 9:20 AM

Never been able to see Jupiter at broad daylight, shortly after sunset yes, but not when the sun is in the sky. Venus is easier and I saw it even at noon

Queequeg de la Pequod September 20, 2011 at 3:16 PM

Hi Ray, at 1244 on 9/27, the Sun’s AZ will be 180? and the Moon will be 175? from SE WI. I’ll be watching. I too have been viewing since childhood. ‘Used to lay in the back yard hoping for shooting stars. No light pollution there and the Milky Way stood out like a sore thumb.

Reno Borges September 19, 2011 at 9:56 PM

I think “sun” and “moon” may be used to refer to any star or satellite respectively. Since we, from our perspective on Earth only have one “sun” and one “moon” we use those generic names, capitalized to refer to those celestial bodies. The proper names are “Sol” and “Luna”.

Anonymous September 20, 2011 at 10:18 PM

The Sun does not have a proper name as such, “Sol” is simply latin for Sun. I believe the Romans where responsible for its use as a name for our star. This has then been carried on by others to this day. As i live in the tropics “BIG ANGRY BRIGHT BALL” is somewhat more apt.

Anonymous September 20, 2011 at 5:52 AM

What has always perplexed me is this – The Sun is at 10 o’clock, full and bright, clear sky even. You also see the Moon at maybe 2 or 3 o’clock in the opposite direction (the other side of our vision of the sky from where the Sun is), and it is a Quarter Moon or such! How can this be, what is shadowing the Moon for it to only be a Quarter Moon in full view of the Sun? Always seemed weird to me………..

Anonymous September 20, 2011 at 7:15 AM

Hi Viking1956 When you see a Quarter Moon it is because the Sun and Moon form a 90 degree triangle – to see a Full Moon the Sun, Earth and Moon have to be in a straight line. Remember the Sun always lights half of the Moon’s surface it is just that we can see increasing amount of the Earth facing surface as we move from New Moon through Full Moon and on to New Moon again. Great isn’t it!

Brian – Roseland Observatory.

Lance Stinson September 20, 2011 at 6:05 AM

I walk my 20 mo old son every morning, and many mornings he spots the moon and points it out. Clear as day about 8 am sun is up behind us to the east , moon is in the west.. he doesnt know that many words yet but he will point and say.. moooooon… :)

Gadi Eidelheit September 20, 2011 at 6:21 AM

In Judaism and Islam seeing the new moon on its first day is actually how the new month is decided. Seeing a new moon is quite challenging as about 1-3% is lit and it is very close to the sun. I hope I do not break any low here by pointing to a video I made on a new moon setting. If so Please remove it with no hard feelings
http://www.youtube.com/watch?v=7qh8DS_41Q8

Anonymous September 20, 2011 at 7:18 AM

I am working with an Islamic group explaining how it is possible to see a newer Moon some months than others.

Brian – Roseland Observatory.

Gadi Eidelheit September 20, 2011 at 9:21 AM

I’ve once saw the eclipsed full moon and the sun together. This is quite challenging as during eclipse the moon shall set at the same time as the sunrise, but there was some difference and I was at a 900m altitude which gave me some more visibility below the horizon.

Queequeg de la Pequod September 20, 2011 at 3:21 PM

Hi to all, is there such a thing as a light pollution advocacy who will contact City Hall to encourage the halting of streetlights? In addition, what process actually works? Certainty replies only, please.

Anonymous September 20, 2011 at 4:24 PM

If you’re interested in the problem of light pollution & light trespass, and what can be done to mitigate it, check out the International Dark-Sky Association: http://www.darksky.org/

Queequeg de la Pequod September 20, 2011 at 8:09 PM

Thanks for your reply. I studied their site and others a while back. What I need is the cavalry. If I say to them “Fido, Attack!” it doesn’t look to me that they will. Also, some municipalities have enacted laws against light pollution, ours hasn’t. Decades of working with governments regarding National Security, emergency communication towers and wireless misconceptions have convinced this retiree not to get on that horse again.

Karl Erikson September 21, 2011 at 5:53 AM

one reason for people being surprised is that in the 1960′s , Science Teachers taught us that the Moon and Sun were rotationally opposite around the Earth , another words when the Sun was visible the Moon was on the opposite side of the Earth and when the Moon was visible , the Sun was on the opposite side of the Earth , so lo and behold when these students of science finally gaze above in 2011 they are awed at the fact that they can see both a full Moon and the Sun at the same time …. i know i was quite surprised when i noticed this maybe 3 years ago …. so what other “lies” were we taught in school is all that came to mind …. that “we are the only life form in the Universe” …… well , i had an encounter in 1960 that forever dispells that “lie” .

Anonymous September 22, 2011 at 5:35 AM

Teaching was quite different on many subjects in the 1960′s (from my understanding).

I wouldn’t consider “we are the only lifeform in the Universe” a lie. Perhaps just a omission of collective 1960′s ignorance. These days, there is enough evidence to put forward a pretty good case for the opposite. This is especially true for primeval life (think single celled organisms or slimes. Yet we don’t know for sure.

When it comes to spectacular or other extraordinary experiences, I have found that it is best to err on the side of caution and careful analysis. The more extraordinary the event, the greater the body of proof that one should generate in order to conclude that the experience actually occurred. Remember that our memory can play tricks on us. Each time you remember something, you are actually reconstructing the memory; changing the experience!

For example, something mundane and recent should be easily within the realm of possibility. Say my trip to Tim Hortons last morning (We have these coffee shops every block here in Canada). I can be reasonably sure I visited this place as I often do so. If I need proof of the specifics I can look at my receipt collection. It will indicate the time, date and what I purchased and from where. This is reasonable evidence for an un-extraordinary event.

Unfortunately (or fortunately, depending on how you swing this) an alien visitation would be an extraordinary experience. Not many people would claim to have this or related proxy experiences. This should immediately put up some mental red flags – since alien visitations are not part and parcel of the human experience, it is very unlikely that something like this occurred to you. This would be my basic assumption I would begin to reconstruct the experience from; no matter how convincingly otherworldly it may have felt.

First thing I would do is ask myself: “on what basis do I come to such an fantastical conclusion? What is my hard evidence?”

I surmise my memory is pretty good. I’m in perfect shape (bodybuilding, running), no aliments, do not smoke cigarettes or marijuana, rarely drink, eat a hunter-gather diet, and have no history of delusions or other mental sicknesses. Even so, I know my senses can play tricks on my brain, fatigue and other external influences can distort them. In addition, my memory is imperfect at the best of times.

Again, does my hard evidence collaborate what I remember? If you have photos, video, audio, written records or recorded testimonies, do they match your recollections? If so, are they consistent with each other? Look closely at the photos. Are they clear? Is there other possible interpretations to explore? Have you consulted several experts? Not UFO-fanatics but meteorologists, aerospace engineers, metallurgists and even locals who may be familiar with the site in question.

Remember that an alien visitation claim is highly extraordinary – you would be the first if it’s true – no other visitation has ever passed the basic tests as described above. If you have nothing to go on other than your memory then you have no case. If I can’t even present an argument to myself, how can I be so sure what I’m claiming isn’t utter nonsense? Despite perfect health (and I mean absolutely perfect) I would not trust such a wishy-washy basis (memory of one or a couple individuals). No case means no way of investigating your experience in the real, physical world. To others, I would just sound crazy.

Extraordinary claims require extraordinary evidence!

Comments on this entry are closed.

Previous post:

Next post: