This week 6-year-old Kambreigh Schooley asked us why she can sometimes see the moon during the daytime…What a great question!
To answer this question you need to first remember that one half of the moon is always illuminated by the Sun.
As the Moon travels around Earth in its 29 day orbit, the portion of the illuminated half of the moon that is visible to us is always changing, creating the different moon phases as we see in the diagram below.
Phases of the Moon. Click to enlarge. Image courtesy www.wikipedia.com
Moonlight is light from the sun bouncing off of the moon and reflecting back to us on Earth. It’s very bright! Full moons are the brightest moons because virtually all of the illuminated portion of the moon is visible to everyone on the night-time side of Earth. First Quarter and Third Quarter moons only show us half of the sunlight side of the moon.
Because nighttime moonlight is so bright and beautiful it’s easy to overlook the fact that moonlight is also bright enough to be easily seen against the blue sky during the day.
Moon as it appears in the daytime sky. Click on image to enlarge
Now back to the question about why the moon is sometimes visible above the horizon during the daytime hours. Take another look at the moon phase chart above. Imagine yourself standing at the various locations on Earth indicated by the time of day.
You can see that at the 12 o’clock noon position, you’re directly under the Sun, and if you happen to be looking up on the day of the New Moon, you’ll not only be looking toward the Sun, you’ll also be looking in the direction of the dark half of the moon. Not much fun there.
Now imagine yourself at that noon location on Earth, but the moon’s phase is either First Quarter or Third Quarter. Can you see the moon? Sure! Your line of sight permits you to see the moon quite well, even though it’s daylight.
It’s generally been my experience that the best time to try daylight observations of the moon is in the week following Full Moon. Look in the west or southwestern skies during the mid-morning hours. If the skies are clear, you’ll have no trouble seeing the moon, in broad daylight.
Tags: astronomy, moon phases
Actually, the moons orbit around the earth is 27.3 days not 29.
Busted! You got me, Tyler.
Yes, the moon makes a full 360-degree trip around the Earth (its “orbital period”) in 27 days 7 hours and 43 minutes.
However, the time interval between Full Moons, the measure of how long it takes for us to perceive that the moon has made a full circuit around the Earth, is 29 days 12 hours 44 minutes. That’s known as the “synodic period” of the moon.
If we tried measuring the moon’s motion with its orbital period the phase of the moon would never match from one orbit to the next. By using the synodic period it is possible to make uniform statements about the “age” of the moon during each lunar cycle.
But nonetheless, you got me, and it was technically inaccurate to refer to the moon’s “orbit” as being 29 days long.
Thanks for keeping us honest!
How long do you spend a day coming up with stuff like this?
Wow this is sooooooo cooooool and i dont cosider myself a nerd nerd (no offense) but when it comes to space i lose my coolness
The “Cosmic Quiz” questions are solicited through a partnership with a local tv station from viewers. Selected questions are answered by a variety of staff members, including our Director and our Education staff. We love answering questions from the public about astronomy and space science, and would spend more time doing it if we could.
hi im only thirteen and im doing this kind of project, do you know what my activity will be? plz help me i cant think of any activity about “moon in the morning”
We are not in the habit of doing students’ school work for them, but if you give us more information about the nature of your project, we can probably give you some ideas on how to get started.
dont worry i did all of my work i just need an activity (science expirement) about moon in the morning…………….. i was actually thiking of a flash light presenting a sun, a mirror present a moon, and a light paper presenting a the sky.
I know that you can occasionally see the moon during daylight hours, but my question is can one see a FULL moon during daylight hours? I am asking this because one of my teachers told me that you can’t because the earth, moon, and sun are aligned at 180 degrees which would prevent us here on earth from viewing a full moon while the sun is up. Is this true? I feel like I’ve seen it before and think that this 180 degree thing doesn’t hold true because earth is tilted 23.5 degrees.
@Erin:
Your teacher is mainly correct. However, if the moon were 180 degrees away from the sun, it would be in Earth’s shadow (a Lunar Eclipse). A Full Moon occurs when the Sun/Moon angular separation is close to 180 degrees, but not exactly (say 176 degrees). Ignoring atmospheric refraction, if you were in the right place, you could actually see both the sun and Full Moon at the same time, but they would both be on exact opposite sides of the sky and just above the horizon (example: sun due east, 2 degrees alt, moon due west, 2 degrees alt).
Earth’s 23.5 degree tilt effets where the Full Moon will be at in the sky, but it does not change the illumination of the moon’s disk. Angular separation is angular separation, and Earth’s own axial tilt has nothing to do with it. If the sun and moon are separated by 135 degrees (gibbous moon), and you take into account Earth’t tilt, you would only notice a change in the moon’s location in the sky. It’s percentage of illumination would still be the same, as the two bodies are still separated by 135 degrees.
What you’ve probably seen is a nearly-full gibbous moon, just a couple of days before or after the Full Moon. The gibbous moon is visible either a couple of hours before sunset or a couple of hours after sunrise, and at first glance appears to be full. Upon closer examination, you will see the terminator clearly (the divider between the day and night hemispheres).
This morning, I saw the moon during daylight hours in a way that I never have before. It showed above the mountains and the moon was as bright and as solid appearing as it looks at night. I know that this full moon was a couple of days ago. I have never had any trouble being able to see that the moon isn’t really full if I look carefully. But I couldn’t see that this morning. The moon looked full and as vibrant as it does on a clear night. Very different experience that I will not forget.
Why do I see the moon in the west just before night fall (7/3/2011, 9:00pm Texas)
Vicky,
Refer to the image at the top of the post.
When you’re looking towards the Moon near sunset (sometime between 6pm and 9pm) soon after the New Moon, you’re looking almost as much in the direction of the Sun as you are in the Moon. With each passing day the Moon will move a little more to the east until on the day of the Full Moon the Moon rises in the east as the Sun sets in the west.
The Moon keeps moving around Earth in an easterly direction until the next New Moon and the cycle begins again.
ok ive seen the moon in the sky before but ive pointed it out to my friends and they all say that they can’t see it. I know i saw the moon.
When I see the moon in the morning in the uk what would someone in Australia we. Can they see the moon at the same time and if so how?
Fran,
Great question!
Australia is a big place – depending on where you are in Australia your time shift from UK time can be between 8 hours ahead of Universal Time (e.g., Perth) to 10 hours ahead of Universal Time (e.g., Sydney).
Because Australia is on nearly the opposite side of the globe from the UK, it would not be uncommon for it to be daytime in the UK when it is nighttime in Australia, and vice versa.
You would see the same phase of the Moon from either location.
The only real difference is that between the locations you’d see a left-right reversal of the lit/unlit portion of the Moon, because of your northern hemisphere vs. southern hemisphere viewing perspectives. Moon phases and their exact time of occurrence are determined by the geometry between the Sun, Earth and the Moon, and are not related to your location on Earth.
If you are careful with when you try to do it, you can sometimes see the Moon simultaneously from Australia and the UK, but you generally need very flat horizons to do this.
For example, in the UK on February 7th of this year at 7:30 PM a Full Moon will be visible rising in the east while at the same instant it is 5:30 AM on February 8th and the same Full Moon would appear to be setting in the northwest.
Happy Moon-gazing!