What Causes The Phases Of The Moon?

What causes the phases of the moon? The common incorrect answer is the shadow of the Earth. The phases of the moon are actually just a result of our perception of the moon's half-illuminated surface. When the moon does pass through Earth's shadow the result is a lunar eclipse. This can be spectacular as the moon turns a deep shade of red.

[veritasium]

I think partly it's due to how close people think the moon is to earth (check out that vid if you haven't see it already). If the moon were that close, it would be tough not to cast a shadow on it.

[katieb]

Who else had to do this for school?
👇🏼

[veritasium]

The statement is not contradictory because there are times when the Earth, sun and moon line up, even though the orbital plane of the moon is tilted at 5 degrees relative to Earth's orbital plane around the sun. These are the rare eclipse events.

[Tjita]

Dear Southern Hemisphere,
Please stop depicting the moon upside down.
Regards,
Northern Hemisphere

[veritasium]

it is more or less, isn't it? You can have a new moon around sunset or sunrise but not in the middle of the night because you're right, it would be on the opposite side of the Earth

[veritasium]

1. true 2. yes 3. no - the moon is tidally locked to the Earth, meaning it rotates on its own axis once in the time it takes to orbit Earth. This keeps the same side always facing Earth - check out tidal locking on wikipedia if you want to learn more.

[particleonazock]

2:20 Thank goodness you started talking, I was getting blinded by the light in the background.

[cloverknight]

Guys. The "wHo eLsE iS heRe fRom ScHoOL" comments are old just stop dude

[NickRoman]

Yes, and then if one were to guess, it seems like a reasonable guess. When there is a crescent moon, sometimes you can still see the dark side a bit. If the Earth was close and casting a shadow, you'd more likely have some light reflecting off of the Earth onto the Moon and back.

[veritasium]

@theFounder87 Yes, yes it does. Once a month, which is why the same side always faces us. This is no coincidence, it's due to something called 'Tidal Locking' - check it out on wikipedia if you want to know more.

[etanajohnson]

Nobody:
Not a single soul:
Me: FURRY MICROPHONE!

[buddleiagirl]

Neat. When my daughter was in elementary school, her class had a project where she demonstrated this for class. She stood in front of the projector (the sun) and held a play ball (the moon) in front of her head (the Earth) at arms length. She was able, with the teacher's help, to show this by moving around the projector and spinning while doing so. If you say that your eyes are your hometown, and the moon is where you see it at night, it makes it quite easy for kids to understand this way.

[StratoFear]

I had no idea that so many folks (like, a shocking number) thought that lunar phases were caused by Earth’s shadow

[DavidGloverSydney]

@mreueujj1 Just to clarify this: the "dark" side IS periodically illuminated (when it's facing the sun). But we can't see it because it's facing away from us. So it's better described as the "far" side of the moon.

[gromitmcgorcdnbmzsty]

Hi! I really like the videos you make! You explain better than other videos I've seen around, much better than my physics teacher..
I have a request/suggestion for a video, that'll explain something alot of people make mistakes about: circular motion (an object moving in a circle, both vertically &horrizontally), like clearing the fact that despite a vehicle is moving in a circle in a "constant" speed, it's still accelerating because it constantly changes direction.

Just a suggestion, thanks!

[RCSVirginia]

It was so nice to watch a science video that posed a question to which I actually knew the answer.

[KBACON]

@1veritasium Your explanation is incorrect. The Moon is divided into two hemispheres: the nearside and the far side (what people call the "dark side"). The nearside is permanently locked facing the Earth because when the Moon was formed its liquid core was pull by Earth's gravity towards one side. This is why the Moon is smoother on the nearside. The Moon's hemispheres have days and nights just like Earth, only longer. The night side (the true dark side) will move as the Moon orbits the Earth.

[quick_man]

0:58 this guy doesn't believe in lamps

[localbod]

Thank you for posting this.
It makes so much sense and I no longer believe what I did about the Earth's shadow.

[cheddle]

I love that OP responds to most comments ^.^ I want to know how many people you sampled at the start and how many responded correctly, stating that the phases are caused by the sun facing a different side of the moon to that which the earth is facing, and how many people stated it was due to the earth blocking the sun. I would have expected most people to know the correct answer.