Why do mirrors flip horizontally (but not vertically)?

Why do mirrors appear to flip images horizontally but not vertically?
physicsgirl.org/
Instagram: / thephysicsgirl
Facebook: www.physicsgirl.org/facebook
Twitter: www.physicsgirl.org/twitter
Help us translate our videos! kzbin.info_cs_p...
Featuring guest Meg Chetwood @megatronvolley
Thanks to Kyle Kitzmiller
and Veritasium / veritasium
Music: "Rhythm Changes," "Locally Sourced"

[@StarMonkies]

I am more confused about how mirrors worked than before I saw this video.

[@thewhopper256ify]

All she needed say was that mirrors show exactly what they see. Go to a mirror and try it; the mirror will show exactly what it sees.

[@errornotfound4004]

A mirror shows a reflection, simple. She just over complicated it

[@daemonCaptrix]

A mirror copies all the light that hits it and sends it back where it came. It's not flipping anything. It's like a rubber stamp on paper, but with light.

[@bigmacnash2146]

LOL ITS JUST ONE ASSUMPTION :P HOWEVER NICE FOR DA CLEARUP. N DAT GALZ R STILL HOT AS FUG. IM JUST HONEST N YEAH A DUDE. ++ (COULDNT JUST FOCUS N WHAT SHES TALKING)

[@DevashishGupta132435LC]

me too

[@kmckinlay8070]

I require some time to reflect on this video.

[@deathstarcake5776]

Did you just...

[@shamsterthehamster]

Perfect pun doesn’t exi...

[@Introvertrains]

You're gonna be a great dad

[@MisterTutor2010]

You must be PUNished :)

[@parinitiverma9895]

I mirror your move

[@Lozzie74]

I’ve studied physics at school and at university (I’m an engineer). I’ve never been able to articulate the explanation to this problem, and I never realised it was a z-axis flip. What a fantastic explanation!

[@Andrew-ku5sl]

I think this part makes it all make the most sense. That it’s a z-axis flip.

[@grahamhodge8313]

I'm glad that you came away enlightened. From the comments, I think most of us did not.

[@musknoer89]

It is not a z-axis flip. The mirror is simply reflecting light. I can not understand why so many people have troubles undertanding that.

[@prehensiledale1215]

@@musknoer89 the mirror reflects light VIA the z-axis, which is why it is correct to call it a z-axis flip AND the mirror simply reflecting light.

[@musknoer89]

@@prehensiledale1215 that doesn't make sense and is simply wrong which is why I pointed that out. Try standing slightly on an angle the left or right of a mirror and point a laser at it. If it is a flip in the z-axis, the laser should reflect towards you. Do you really think the laser will be reflected directly back at you? The angle of incidence equals the angle of reflection. Calling it a flip in an axis is nonsensical when talking about a mirror.

[@davewylie7771]

I had a physics teacher explain this in high school. And I understood it but really had to think it through every time it came up, lol. This made it really clear. Thank you! Very well done.

[@maniatic007]

I tried this and somehow I got stuck inside the mirror, how do I get out?

[@izaicslinux6961]

get yourself a De lorean

[@izaicslinux6961]

+Madscientist with a doc brown.. and a idiot sycopath

[@mattyboii09]

HAHAHHAH

[@justin9774]

119 llɒɔ

[@wkrijthe]

;) ...gniniart fo sraey sekat kcutsnu gnitteg yletanutrofnU .taht tuoba yrros ma I

[@rajeevk.pathak771]

Great! If one were to hold the mirror ABOVE our head, with the reflecting side downward facing us, then the "vertical" flipping would occur...the image would be upside-down or "inverted". The fact is that the mirrors flip only that component of the object which is perpendicular to it...we call it 'lateral inversion' in common physics parlance! Way to go, Physics Girl!

[@shinronin7312]

cant you just lie down? that mirror is pretty heavy🥂🥂🥂

[@rocroc]

The is the "BEST" explanation and should be locked at the top of the comments. Thanks.

[@jimwhelan9152]

@Amethyst not sure what you mean by "normal line" but a convex mirror reverses in the plane of the mirror just like a flat mirror. For a concave mirror things are complicated by the fact that the light is focused and then spreads out again. The appearance of the reflected image depends on where your eye is relative to the focal point. Past the focal point the image is rotated as well as flipped. Your image will be upside down.

[@whatdoyouthinktodd]

I have a better idea Don't worry about what the mirror does to your image just worry about the person in the mirror 🍦

[@chrisg3030]

Your point complements her explanation nicely. That image you see from below is also flipped in the z direction, the component perpendicular to the mirror plane, towards you. Just like the others she demonstrates.

[@holoholokalei3286]

Interesting that you haven't mentioned a "true" mirror, which is created when you have two mirrors perpendicular to each other. With a mirror in the z direction it flips the z flip of a single mirror, thus showing the true image as if you were standing behind the mirror loking through it. Letters appear in the proper order and direction. My aunt used this type of mirror to apply her makeup so she'd see herself exactly as others would view her.

[@longnguyenson646]

Can you provide me with a link of a product in real life? I want to know the keyword so I can get one.

[@tomcz1098]

you can do this today with an LED or TV screen with a cam that you configure to flip he image horizontally - Voila

[@vinnylamoureux1187]

And then we would all be more confused than ever. If I hold a mirror above my head, I dissappear. Only my bald head is up there and, since I can't see it, I have disappeared. So there !!!

[@NathanielKlemm]

Still one of my favorite Physics Girl videos - maybe even my favorite. Get well soon, Diana!

[@10ON10]

*Instructions unclear, Now I am trapped in the mirror and typing from there...*

[@toastiesburned9929]

...ereht morf gnipyt dna rorrim eht ni deppart ma I woN ,raelcnu snoitcurtsnI

[@vult07]

S

[@fallinginthed33p]

That's a horror movie plot in the making.

[@thatHARVguy]

Say "hi" to Mirror Julie.

[@datdudeinred]

You've been watching too much of the flash mate 😂

[@mountainman615]

Growing up. She must have driven her parents insane with questions! I love how she thinks!

[@peterfitzpatrick7032]

She was a "why?" child rather than a wild child ... 😏

[@garymartin9777]

Yea but she's so darned cute what parent could get mad at her?

[@mrx-od3ji]

@@garymartin9777 i think she is right.

[@stephencummins7589]

I can’t stop smiling at how brilliant she is.

[@curtis8906]

absolutely.. I think to she drove her parents insane with questions. I know that's why she is so smart, ask questions to find out the answers.. She ROCK's..

[@RobertU125]

I love this explanation! Anyway, I hope you are recovering well. The science communication community is not the same without your enthusiasm and creativity

[@keithlevkoff8579]

I love your videos.... You always seem to cover interesting topics, but far more important, you both make them fun and explain them in normal language that is accessible to everyone. (I do technical writing for a living and I KNOW how difficult that can be to do.)

[@bldallas]

This has always baffled me, when I overthink it. I also believe this is the reason so many people (myself included) don’t like how they look in photos. We are used to seeing ourselves in mirrors, but pictures are not a mirror image. Most people’s hair, facial features, expressions, etc. are not exactly symmetrical. So even though our photos generally perfectly fine to those around us, to us, they look a bit odd.

[@RaineStudio]

In fact, we have spent many years visually compensating for our asymmetries as apparent in a mirror. When we see a photo (or correcting mirror, or live camera display), the asymmetries are exaggerated because they go in the opposite direction.

[@bldallas]

@@RaineStudio spot on

[@davidcureton9258]

Oh boy… I just commented almost exactly the same experience before I saw yours

[@StefanHoffmann84]

If this is the case, why nobody gots confused about selfies vs "normal photos"? If your theory is correct, other people should feel (or don't like) your selfies, because a selfie is a mirrored image, i.e., the same as when you look into the mirror. I never heard anyone saying, "oh man, in this group photo, you look nice, but the selfies you showed me, something seems odd". Do you disagree?

[@MiooshSlayer]

@@StefanHoffmann84 because after you take a selfie the device flips it horizontally so the saved image is now normal like how people view you irl.

[@w0mbatina]

What the hell? The mirror doesnt "flip" anything, it reflects. And do people really not understand how a mirror works? I mean, the video is well made, even if it is confusing as hell, but why the hell do we even need this? Its just sad when you think that people need a 4min video on mirrors.

[@bswalem]

People have to understand that there are unintelligent people in this world, there always has been and there always will be (relative to the average IQ at any given period). Just because something seems obvious to you, doesn't mean there aren't many people who struggle intellectually who would benefit from this knowledge. I don't understand how you can't get this.

[@w0mbatina]

bdalem Because its mirrors. They are intuitive to everyone without a serious mental disability. And besides, how does explaining it wrong benefit anyone? And to top it of, this is a pretty confusing video thats hard to follow.

[@AlmightyUniden]

w0mbatina It honestly baffles me that someone might not understand how a mirror works and after reading some comments on facebook and on here... it's truly sad some people struggle with a concept as simple as a mirror. She didn't even explain it properly.

[@whosmakingthatsound]

I completely agree with you. Just raising the question of "why do mirrors flip things?" adds more confusion to the topic since, like you said, a mirror doesn't flip anything, it just reflects.

[@daggawagga]

Not everyone has good geometric / spatial awareness dude. At some point it became obvious to you. Just like there are things which are complex to you and obvious to these people.

[@VictorCampos87]

I wondered about this as a child. Then I realized that the mirror was being consistent. What was above reflected above. And what was on the right reflected on the right. And, in a certain way, I realized that my doubt came from an incorrect perception of reality I was seeing. But this Z-flip explanation helped a lot to figure the whole picture.

[@californiaplant-basedeater2761]

"Why doesn't the mirror show me standing on my head" is not a question I've ever asked myself.

[@wedmunds]

This went from "duh" to "wtf" real quick.

[@khary30]

personally, it went from wtf to "ah"/"duh" once she said it's flipped in the z-axis

[@JesseTheGameDev]

" To face yourself... You have to turn around". That was deep.

[@cheath8705]

Jesse Stewart - As Captain Jean-Luc Picard would say: Well, they say if you travel far enough, you will eventually meet yourself.

[@androidedoidao]

* vsauce soudtrack stars playing *

[@noodoo19]

The mirror lies, and it toys with your mind.

[@bilalbhatti9898]

That is when it all made sense to me!

[@alwaysopen7970]

The earth is flat.

[@kupa121]

I'm actually more surprised about the fact so many people don't understand how mirrors work

[@pdp6839]

This is probably one of the best videos I've ever watched. It's so simple, yet completely mind blowing. I could never think of something like this. Absolutely loved the video and subscribed.

[@DB-ho8cc]

Should write on a clear sheet and present it to the mirror without flipping to make your point.

[@stspy212]

"..... damn it!" Physics Girl, probably

[@RCHomemadeHobbies]

😟🤯

[@Novasky2007]

Big Brain

[@evalsoftserver]

I think it's because the Mirror is a Translational symmetry rather than Rotational symmetry of the image

[@podunkis]

This is exactly what I was going to post. Glad your post is at the top. :)

[@kant12]

Why in the world have I never wondered about this.

[@physicsgirl]

I hadn't until someone asked me!

[@gotentk4]

cuz they're not flipped. theyr'e just mirrored

[@Taricus]

I JUST asked the same question LOL!

[@Jon58004]

It's because you simply kant.

[@clansman89]

kant Because it's the simplest physics.

[@mickeyrube6623]

My first thought when I read the title: "But mirrors do flip vertically, like when you see the reflection of the trees on a lake..."

[@LucidDreamer54321]

As Patrick Swayze would say, “I look in the mirror and all I see. Is a young old man with only a dream.”

[@schwaner1000]

Just stand on a mirror and your reflection will be flipped vertically.

[@dixie_rekd9601]

make sure you have clothes on of course.

[@superstellar243]

Thanks man to tell that to a girl, as I wanted to. This video is a joke.

[@jeffc5974]

That's just changing the coordinate system. It's still flipping in the Z direction.

[@Smesp]

Thank you.

[@javascriptsophie4958]

no mirrors don't flip anything mirrors actually reflects light where it hits it

[@One_Angry_Man]

I started confused and ended up frustrated. That's why I subscribed.

[@campkira]

mirror mean it just reflection not flip.... got nothing to do with what direction....

[@anshumanagrawal346]

Honestly, she caused some of the confusion intentionally, if she just wrote something in the mirror which was written on a transparent paper it would have made it clear

[@monad_tcp]

I was frustrated, then I broke the mirror, and it was an entire room mirrored in my direction and the mirror was just a glass window.

[@toastiesburned9929]

Try watching PBS spacetime for a few days. You think you understand, and then you get lost, but then find your way again and by the end of the video it leaves you with more questions than answers.

[@thv7933]

Bruhh..this is easy...my father also taught me this

[@daviddavis5150]

My thoughts and prayers are with you! Get well soon!

[@staragape7999]

I think writing on a clear piece of plastic/glass and holding it to the mirror would be a nice way of showing this as well. Reads correct in front of you, reads correct in the mirror all at the same time.

[@arooobine]

Directions unclear. Now I'm stuck doing a handstand on a mirror surrounded by food, looking like a doof.

[@Z8MB1ET0WN]

this is literally the greatest comment in the history of comments

[@98tam]

😂😂😂 Genius comment

[@chelleturtle1121]

Lmaooooo

[@spectrelex3051]

LOOL😂

[@shinku5463]

Well at least its not a particular body part stuck in a mirror.

[@BluesyBor]

2:32 ... I don't like it when mirror images start to act on their own. I really don't... :D

[@mireazma]

:))

[@CrArC]

@BluesyBor I don't suppose you've watched the film "Mirrors" (2008) then. It's an effective way to develop a phobia of mirrors, I'll say that much.

[@Mimirai]

Mine does it all the time... We cant really talk with each other because of this.

[@felixfourcolor6806]

so creepy ~

[@ttp_007]

Here is my explanation. The mirror does nothing but reflects light. Since everything we see is the effect of light reflecting over an object's surface, mirrors do the same thing. But it has to do with the direction we learn to read, and the bounced image (light) is coming from the mirror, thus you would need to be behind the mirror to see the image correctly. The arrow example helps us better understand it. The arrow shows the direction in which the image (light) is traveling to. The same thing applies to a light beam of a flashlight hitting the mirror. To our eyes it changed directions, thus to see the same way the mirror we need to be at the mirror's location, or the origin of the location the light is shining FROM.

[@randomshittutorials]

For those who don't understand it after seeing this. I get you. She didn't explain the process behind it is what causes this confusion. Try to visualize light coming out of each cell in your body (straight line) onto the mirror. Then reflecting straight back at you. Your right hand will still be on the right. It didn't cross over to show your left hand, but your right hand itself is flipped. I think a light animation would help most people out here, but this girl is just facinated with her discovery and tries her best :")

[@lee4macs]

This is what I have always visualized. This video only confused me lol.

[@lee4macs]

It’s a very counterintuitive explanation

[@juanjosefarina]

It's the same I've always understood, and most surely what is really true. What she says never maked sense.

[@NotParticularlyAmused]

I would speculate she isn't a physicist but just a youtuber who has taken an interest in physics, so she most likely doesn't have a deep understanding herself and explains things to the depth of her understanding.

[@govinda_bhatt]

😂😂😂@@NotParticularlyAmused I think she understands but somehow for content

[@JunaidAnwar]

Me thinking I understood it, goes to explain a friend and gets confused further.

[@bogasaiteja8968]

🤣🤣

[@The_Tormented_One]

😂😂😂 Same bro

[@josiahhill4993]

The question is flawed. The mirror doesn't flip anything, it mirrors.

[@malekzalfana9940]

then add to it [in our perspective]

[@salvandorum]

More precisely, it laterally inverts.

[@bansheeraz]

THANK YOU!

[@javascriptsophie4958]

exactly it reflects light where it hits it

[@TheNelser01]

Same thing. If you teach children, the word flip is synonymous with reflect or mirror. She is making something non-intuitive simple to the average kid or adult.

[@BlimGlim]

This should have been a 1st of April upload, answering questions that no one was simple enough to ask.

[@johnspisak9729]

You make everything fun and interesting. Including the things I've already thought of and the things I haven't thought of yet. Ponder that for a while.

[@Hyf5]

But what if i flipped the mirror off ?

[@sundevilification]

PLEASE BE CAREFUL.

[@NJ-wb1cz]

It will flip you on.

[@SopanKotbagi]

You just made my day!

[@krumplethemal8831]

you get seven years of good luck..

[@lito11111940]

But what if i flipped the mirror off ? 7 Days bad luck !

[@SimonClarkstone]

You missed one small demonstration: write the word on transparent plastic, and don't turn it around; the word appears the correct way round in the mirror.

[@robertbilling6266]

+Simon Clarkstone Actually if you have a sticker in the back window of your car intended to be read from the outside, it looks right in the mirror.

[@SimonClarkstone]

Yep.

[@solimander1]

+Simon Clarkstone - Good idea - I was thinking along these lines, but didn't quite graduate to clear plastic (I was thinking thin paper with dark ink and light shining from your side.).

[@solimander1]

+Robert Billing Also, very interesting!

[@aryanarora7046]

+Robert Billing does it also look right to our eyes?

[@steveherrick6584]

This blew my mind in its simplicity that I had never realized this. I shared this on facebook and one of my friends responded in such a way that led me to think they hadn't actually watched the video. And I was thinking about how I could explain this beyond what you said and it occurred to me to find a piece of clear plastic with writing on it and face it toward me so that the writing was the correct orientation and then stand in front of a mirror. Even understanding your video, my mind still expected that the writing would be backwards in the mirror - not that I doubted you, but it is so ingrained in my thinking that the mirror flips things horizontally part of me expected to see it reversed. It of course reads with the correct orientation in the mirror. Thanks and I hope you're feeling better.

[@imlistening1137]

Yay! I’m 65 years old and I finally understand this! Thank you, Physics Girl!

[@EddyProca]

I've seen and read so many explanations of this and I kind of understood but it was still hard to imagine. With your explanation, it just clicked. Thanks!

[@physicsgirl]

Glad you liked it. This was the best explanation I could find before making my video kzbin.info/www/bejne/i5y5aWqOeJZoerM, but I still had a few questions.

[@iamjimgroth]

Exactly what I was thinking. I could instantly relate as soon as she mentioned flipping through herself in Z. :)

[@rayquaza396]

The mirror is flipping the image in the Z-direction. Thank you Diana! You just answered my question that's been lingering since high school!

[@davecarsley8773]

You never tried Google?

[@geoculus5606]

@@davecarsley8773 People sometimes get busy with life and don't get around to getting all the little questions they have answered as soon as possible.

[@nameless1016]

but i still dont know why i get 7 years of bad luck if i break one...

[@carlodave9]

I have what's known as a "true" mirror: two mirrors that seamless intersect at 45-degrees. It corrects the z-axis inversion. I'm surprised she didn't use one in the lesson. When you look at it it shows you exactly how you look to other people. You stand in front of your objective self. It's like seeing yourself in a photo or video, but in perfect, life-size, natural 3-d. And as up-close as you dare to get -- which is VERY freaky. You wanna know what you look like when someone moves in for a kiss? Yikes!). I like to surprise my students with it at the beginning of the year. Being early teens, they cannot get enough of the effect. A couple of them in every class come in early enough to adjust their hair. Why not see it as it really looks?

[@1SqueakyWheel]

@@carlodave9 The correction done by the 45 degree mirror can be quite confusing to some people though. If you ever want to see a woman get angry with a mirror, ask her to apply her makeup using a 45-degree corrected mirror... unless she is the really adventurous sort, she will never want to try that again. LOL There's also the coordination issue... like when one tries to fly a remote control model aircraft, and loses their orientation once it's turned around to come back towards them... as such, this is where trainers tend to crash a lot. A simpler example would be when you indicate to a friend that he or she has a piece of icing on their left cheek, you will generally point to your right cheek indicate it. And even though you may actually say "left cheek" , they will almost always still check their right cheek because you pointed to your left one, unless you're compensating for this response by pointing to your right, which most people innately do... due mostly to our conditioning from normal single-plane mirrors, but also because that is how we relate, as this young lady in the video describes our left/right biased mental symmetry.

[@troyarmatti7167]

I'm so glad to finally know this. This has been troubling me for over 40 years. Now at last I can sleep easily never having to think about this again. Thank you.

[@Andrew-ku5sl]

I think the z-axis flip thing makes it all make sense the most.

[@ragibansari1804]

Place the mirror above your head. Then look at it... You are vertically flipped😊

[@fuzzypenguino]

Or stand on it

[@vcthnp]

Instructions unclear Mirror pieces stuck in the face

[@fuzzypenguino]

Or stand *over* it

[@sanveersookdawe]

I just had a mini mind explosion!

[@harrisonkey698]

ooh

[@TechInspected]

I tried paying attention to the girl but got distracted by all the physics.

[@PrakharPal]

+The Technoclast hats off

[@kapitanjojo126]

Damn, The opposite happened to me!

[@thethinkinlad]

+Taran Singh I'm a multitasker 😏

[@EpicTheRozjebywator]

+The Technoclast you've made my day :D

[@pranamd1]

+The Technoclast My faith in humanity is restored....now to scroll down and read some more comments to obliterate it again.

[@aryansoni9782]

This video has actually made me understood about why do mirror flip horizontally and also I am able to learn about reflection for my Physics unit waves. Thank you.

[@kosmokritikos9299]

Not too many even know what a large format view camera is, but with that camera, composition and focusing is done on a ground glass panel at the back of the camera onto which an in image is projected through the lens. That image is flipped both horizontally and vertically.

[@FernieCanto]

This damn question haunted me for so long, and all answers I could find on the Internet were so vague and esoteric and confounding that it only puzzled me further. Then this video comes up and, wow, it's *that* simple? Incredible. This has been one of the most interesting, informative and thought-provoking science videos I've ever seen on KZbin. Kudos!

[@physicsgirl]

Thank you for the nice comment! Glad the video cleared things up.

[@SoothWaves]

Physics Girl I think that was sarcasm....no wonder you do science about mirrors...

[@FernieCanto]

***** You are entirely wrong, *and* you suck at detecting sarcasm.

[@FernieCanto]

***** Because random, unknown KZbin commenters are totally trustworthy, of course.

[@lcapillon]

It's not science. Trust me, I'm a soon-to-be engineer, she just gave you 1% of the real explanation.

[@monkeywrench4169]

What if you hold the mirror upside down?

[@AMessful]

You're a king under all physicians. With joyful laughter, I solute you.

[@Appleholic1]

lol lol

[@elsarodriguez9930]

😂

[@spooky1000]

What if you turn the mirror inside out ?

[@GbengaOlayiwola]

Lol, um sorry loL

[@exel001]

first part of answer is correct: mirror flips in normal direction. so it can change up and down if we just place the mirror on the ground and stand on it. the second part of the answer is about how we define left and right. and this definition is directly relates to the basis orientation. and the fact that the mirror reflects along the normal leads to a change in the orientation of the basis, that is why it changes left and right for us.

[@hypercvbe]

Wow, I was asking myself the same question long time ago, and had only some premises of explanation. But you nailed it, and I'm glad I've seen this video in my suggestions!

[@xenorama7033]

One way you could put this, too, is to prove that there isn't actually any horizontal flipping occurring at all: The mirror image of your top half is still above the bottom half, so no vertical flipping. However, the image of your right hand is STILL to the right of the image of your left hand. Therefore, NO horizontal flipping either, exactly like the vertical axis. A bathroom door to your left is still to your left when viewed in the mirror, another example of there being no horizontal flipping. If you put a mirror on the floor and stand on it, then you have vertical flipping, as up becomes down. But left is still left, and forward is still forward. If while facing a mirror, you simply turn to the right, suddenly the image of your right hand is not only on your left, but to the left of the image of your left hand.

[@HubertGeorge]

You had me until this: "If while facing a mirror, you simply turn to the right, suddenly the image of your right hand is not only on your left, but to the left of the image of your left hand."... If I turn right my right hand would be behind me, not to my left. Did you mean if you turn 180 degrees?

[@xenorama7033]

No I mean if you turn 90 degrees to the right, resulting in the mirror being on your left. That's what I mean.

[@HubertGeorge]

Ah I see.

[@xenorama7033]

Yeah I kinda tossed that example in at the end, it wasn't very important so I didn't explain it very clearly.

[@mahamahawi3243]

the mirror reverses the front and the back but my question is does it affect our physical image in other words is that others see us the same way when we see ourselves

[@RianKashfi]

That last part sounded so deep. xD "The mirror is showing you what you presented to it."

[@DannyJoh]

I've been trying to wrap ny head around this for years. This was a great explanation! Thanks!

[@frankslade33]

I never thought of that angle, how we flip it horizontally to see it instead of vertically. Fantastic.

[@pkbeast]

An answer to a question I never even thought to ask and now my mind is officially blown. First video I've seen of Physics Girl and wow, what an introduction to the channel !

[@salah3beed]

PKBeast +1

[@collinf714]

Same exact thought. Word for word

[@salaambaalaktrust5046]

I like the girl.

[@atmark666]

this is from old Royal Institution Christmas Lecture. i think it was 80s or 90s

[@fearless4him595]

My first video too. I think I broke my brain.

[@williambarnes5023]

Mirrors don't flip horizontally or vertically. They flip front to back.

[@chrispatriot]

+William Barnes Actually they don't "flip" at all.. It's like the old mind game joke "What goes up and down but never moves?" to wit the answer is : A road... The mirror is stationary and its the light wave which hits and bounces back in an exact opposite direction. Therefore, the only thing which actually changes is our own individual "perception."

[@williambarnes5023]

Chris Banzet No, they absorb photons and emit different ones with reversed chirality. They actually flip them front to back.

[@chrispatriot]

+William Barnes No, they do NOT recreate new photons. Its the same photons being ricocheted back at the observer. And again, they don't actually reverse, there's many scientific documents available that you can read about the subject matter. "chirality" is not the exchange of molecules produced by a mirrored reflection, they merely use the mirror image to create an impression of it being "identical". Chirality is merely the state of equal identity to another molecule - see this definition "Chirality is a property of individual molecules. If a molecule is chiral then we know that the molecule has two enantiomeric forms (which are almost identical but are actually different molecules)."

[@williambarnes5023]

Chris Banzet I'm going to give you a moment to read those "many scientific documents available" yourself.

[@chrispatriot]

+William Barnes I've already spent about 35 plus years reading them, I don't NEED to read them again.. I know what the internet says, and I know what science says.. They're contrasting, and definitely there is a truth, and yours wreaks of Google searching..

[@1SqueakyWheel]

"Because the mirror is just showing you what you've presented to it" Mind blown.

[@jimwhelan9152]

Worthy of note: write a word on a piece of translucent or transparent paper and hold it facing a mirror. Note that the word now seen from the back side of the paper is the same as the mirror image. That demonstrates that the mirror isn't really reversing the horizontal direction.

[@andrewlinn7863]

The confusion comes from a misuse of terms. A mirror reflects what is across from it, it does not flip it.

[@sonnybeach1953]

You could have illustrated the conclusion by showing a piece of paper with the word 'food' written on it with felt tip pen, but the ink bleeds through the paper showing the word on the back side as well as the front. Then, showing the back side of the paper to the mirror would reflect the correctly oriented word to the observer.

[@MrDannyDetail]

More or less what I was thinking. When she showed that she had in fact flipped the paper to show the writing to the mirror I was hoping she'd then point the camera through the back of the paper to show that the writing bleedin through the paper matched the reflection she could see in the mirror.

[@bam9609]

exactly! the same with writing food on a piece glass. if you look at it on the other side of the glass, it will be the mirrored word.

[@EvilStreaks]

yeh but it only correctly reflects the back when you turn the paper horizontally, not vertically. ;/ Other wise the reflection would still be upsidedown. You're just demonstrating that it DOES flip the image on a single axis, not why... ;/

[@MrDannyDetail]

The point is that the mirror does no flipping on any axis, the light being reflected back in the exact same orientation it was presented to the mirror (assuming a flawless flat mirror), you just had to flip the paper (horizontally) for the mirror to reflect it back to you, so you turned it back to front from your own point of view (as the ink through the back of the page would demonstrate), if you flipped it verticallly instead then by definition you have got it into the same position as if you had turned it upside down and turned it horizontally to face the mirror, so the writing facing the mirror is now upside down and back to front, as is the writing in the reflection, and so too would be the writing seen through the back of the paper. So demonstrating both of those things with sufficiently see-through paper, or sufficiently bleed-through-able ink, would clearly show that the reason why it appears to flip the image, is because you have flipped yourself or whatever you present to the mirror, so you are now viewing the thing as if you are looking through it.

[@EvilStreaks]

Yeh but you could have just said "because when you face a mirror, your orientation is yaw-rotated 180 degrees from the mirror's which is where the difference comes from. If you turn your back to the mirror, you're seeing what it sees which is not flipped."

[@carlodave9]

I have what's known as a "true" mirror: two mirrors that seamless intersect at 45-degrees. It corrects the z-axis inversion. Im surprised she didn't use one for illustration. When you look at it it shows you exactly how you look to other people. You stand in front of your objective self. It's like seeing yourself in a photo or video, but in perfect, natural 3-d. I like to surprise my students with it sometimes, especially when I have them put their face right into the mirror box. Being teens, they cannot get enough of the effect. A couple of them come in every morning to adjust their hair.

[@snorkfire]

That’s a really great explanation. I have to admit, that’s not the commonsensical view I’d always carried around. But you’re clearly spot on. You might have also read the Food sign thrue the back side to match the mirror image.

[@kleidos]

plot twist: the reflection is a paid actor

[@VoltisArt]

That's no plot twist, it's the foundation of a horror story.

[@sadiaaa1373]

Plot twist: thats not a joke 2:31

[@yojgee]

This is like saying water is wet because it's water.

[@Astronomator]

This is a wonderful video. One effective way to show the reason for the flip is to write words on a clear piece of plexiglass so they can be read from either side. Then flipping the plexiglass allows the "user" to see the letters from the rear (and to see them flipped), and to see that they exactly match what the mirror is reflecting.

[@afrodemon8629]

When she said "That's what's causing all of this confusion." I was like "Nah, you're the one confusing tf out of me."

[@mattmullin33609]

The mirror is not flipping anything and it's not because we are "presenting things horizontally". It's simply light reflecting back in the opposite direction that it hits the mirror. That's it. So, of course, things will appear to be "flipped" when that light bounces back. If you bounce a ball off a wall then it's going to bounce back in the opposite direction from that same point that it hits the wall. The same happens with light on a mirror. Our feet don't appear to be where our heads are (her so-called Y-axis flip) because the reflected light bounces back at the shortest distance that it originates from. A basketball bounces back from the same point it hits the wall... Wondering why a mirror reflects the way that it does is like punching the mirror on the right side and being confused that it didn't crack on the left side instead. It doesn't make any sense and her explanation of this effect made even less sense. This isn't the rocket science that she makes it out to be in the video. It's simply light bouncing back at us on the same point that it hits on the mirror. Simple as that.

[@edc2380]

My mirror talks to me and tells me to do things

[@korakys]

+Ed C23 Remember, just because it's a mirror it doesn't mean you should do everything it says. Also try telling it to do some things for you too, in exchange.

[@SacredDaturana]

+circ1ebreaker Right? Reflections are such freeloaders if you let them. Tell it to kill ITS whole family for a change.

[@JohnnyYenn]

Sometimes it tells me to burn things... :(

[@mrboni5]

may I suggest that you...GET THE HELL OUT OF YOUR HOUSE!!!

[@Bjac0]

My mirror is named, daniel, he says damn in excitement whenever i bury the bodies :) my mom says i'm "special".

[@alextryan]

Glorious. Somehow this never even came up as a question for me -- now my world is changed!

[@BruceBoschek]

Thank you. I never really wondered why, then I did and now you explained it. Satisfying.

[@TechLaboratories]

I think the summary statement "Mirrors generate a z-axis flip" is perfect and succinct in its explanation. I've never been able to articulate that part, though every time I've thought about how mirrors work, that's what I've visualized! Fantastic, thanks for the video and keep them coming!

[@alwaysopen7970]

Does your dog or cat lose sleep over it?

[@dropsdidit7576]

Wtf did i just learn? Still Mind blown lol

[@danzigvssartre]

This video hints at, but poorly explains the phenomena. The proper explanation requires we think in terms of dimensions. To turn a letter in the 2 dimensional plane into it’s mirror image I need to rotate the letter out of the plane i.e. “flip” it over. To turn your left hand into into your right hand you can’t just “flip” it over. You need to do a double flip in 3D space or one “flip” in 4D space. Good luck! This is because your right hand is NOT the mirror image of your left hand. Your hands exist in 3D space not on a 2D plane. Alternatively, to the double flip to turn your left hand into your right, you can do an “eversion” of the hand, meaning turn it inside out. It helps to study topology to appreciate this significance of all this. The confusion occurs when we treat a 2D image of ourselves as if it were our real 3D body.

[@MaxIronsThird]

Z-axis explanation is wrong though. Just turn sideways to the mirror, you still get a mirrored image, and the you on the mirror is still raising the opposite hand.

[@jamesmziegler]

WTF? It reflects exactly. There's no flipping going on horizontally or vertically.

[@carultch]

It flips perpendicular to the plane of the mirror.

[@jamesmziegler]

+carultch The light coming from the mirror, what I consider the reflection, doesn't flip at all. That's exactly why it looks backwards.

[@carultch]

Jim Doe Oh, but it does. The mirror reverses the perpendicular component of the incident light's momentum, and preserves the parallel component.

[@jamesmziegler]

+carultch All you're saying is that the mirror reflects light. Whoopdiedo. We know that already.

[@ailanixx6668]

are you fucking dumb?

[@jazzdad52]

I tried to understand, couldn’t until the handstand at the end. BRILLIANT EXPLANATION!! We are not vertically symmetrical, but we think we are horizontally symmetrical, because our left (eye) looks similar to our right (eye) . Lie down on your side facing the mirror, you will think you see yourself flipped vertically. Hope you get well soon!

[@punundrum1]

I just found your channel and enjoy what i do and don’t understand…. Yet. You give such good examples, i lack the basics yet to grock it.

[@oscarandgroucho]

My mirror used to flip me vertically, but not anymore. I think I gained too much weight.

[@jibran4794]

😂

[@mecca777]

my mirror can flip an 8 ball to a kilo ok, hand me my beer back.

[@TaiFerret]

Mirrors can flip vertically. You just have to lay it flat on the ground.

[@Chronokinetic]

This comment needs to be higher up.

[@jtherrington77]

Finally! I have been asking myself this question for years. This explanation was perfect! Thank you!

[@mangolassi_0613]

If you get it could you possibly explain whatshe meant with the glove at 2:19 ?

[@jtherrington77]

@@mangolassi_0613 The main idea is that when you turn a glove inside out, the reversal is happening through the circular hole through which you put your hand. In order to see this in a mirror, you have to orient the circle (the part where your wrist is) towards the mirror. If *you* point the fingers of the glove upwards, the circle through which you invert the glove gets oriented along the Y-axis, and in the mirror, the hole essentially looks like a line instead of circle. And when you invert the glove along the Y-axis, meaning take off the glove by moving it along the Y-axis, the fingers flip and point downwards because you have oriented the circle of the glove along the Y-axis. Hope that helps.

[@mangolassi_0613]

@@jtherrington77 i do get some part of what you said, but i don’t get how the glove is being inverted thro the y axis. I mean isn’t the circle still orienting towards the z axis through which it is inverting frontally and then kind of reversing it’s direction?

[@jtherrington77]

@@mangolassi_0613 I don’t know how to explain it any better without using a visual aid like she did.

[@mangolassi_0613]

@@jtherrington77 ahh ok thanks tho for trying💜

[@55nsmooth]

I couldn't care less which way the image flips as long as your image is in it. You are gorgeous.

[@bizmuthhelm9115]

There is a way to cancel the z-axis flip, and it is freaky. You cannot do things like brush your hair, but the words will be correct when you read them. Here's how you do it. Instead of a single mirror, use two mirrors the same height, arranged as in a corner away from you, so that they meet at a 90° angle. If the edges are cut straight there will be a vertical seam smack down the center of the image that is barely noticeable. Now when you raise your right hand, your reflection raises the other hand. Also you see the true face everyone else sees, and it is not the face you have been looking at all your life. No, that beauty mark is over on the other side of your nose, and that's where the rest of the world has always seen it.

[@hogarthheathan]

always wondered why that happens, why does the mirror choose that image and not the other way around, if things are equal whats the difference.

[@bizmuthhelm9115]

hogarth heathan, each time an image reflects it flops. With 1 mirror, the image flops once, and must rotate it the full 180°. With 2 mirrors the image is reflected twice, and each mirror only rotates the flopped image 90°. So 180 degrees of image rotation, but with two flops instead of one. This effect is exaggerated in the extreme when you bring the mirrors to a parallel orientation with the reflections facing in, then look into either mirror, at the reflection of the other mirror. As you bring the mirrors close to parallel it seems that there are endless reflections, and every other one is flopped.

[@iPhr0stByt3]

That's not correct. With 1 mirror, the Z-axis is flipped. With 2 mirrors arranged as you described, the z-axis is still only flipped once, but now you are ALSO flipping the image horizontally - making you appear as you would to someone else, but your image is still wrong - flipped in 2 ways.

[@bizmuthhelm9115]

iPhr0stByt3 what the heck are you trying to say that I didn't already say? When looking into a mirror you are on this side not that side. We all get that, but the effect of your z(in front of or behind the mirror) axis is effectively cancelled by the two mirror arrangement. What you see is what a person opposite the mirrors from you would see if the mirrors were removed, your true image, not the incorrect reversed image a single mirror suggests.

[@TIMEtoRIDE900]

So you could read stuff thru a Periscope, which has 2 mirrors, but the angles are vertical, not horizontal.

[@elviswjr]

I've never thought of mirrors as flipping things horizontally, they're merely showing things where they are. Another way to put it is that when you touch a mirror, the reflection of your finger is right where your finger actually is, just a mirror image of it. If it was flipped, it would be on the other side. Basically, to me, a horizontally flipped reflection would be like watching yourself on your phone with a front facing camera. In other words, my mind isn't fooled. Never has been. The image in the mirror has always looked like what it is, a mirror image, not a window you can look through. I thought everyone else saw them this way too but I guess not.

[@sihoonoh9021]

That's true. The reason why we think letters Get horizontally flipped in the mirror, is because we think the 'original' image is what other people see, whose point of view is horizontally flipped from ours.

[@johngillanders9694]

Thanks so much for explaining this! I had wondered about this for years and had concluded it was related to our eyes being horizontal but you debunked that one right away 😂, I should have thought of that! I appreciate the clarification about why things appear laterally flipped.

[@Hmm...Whats-Their-Name]

3:12 literally just went "OOOOH!" in my room by myself.

[@kennie1312]

Imagine being vertically symetric lmao

[@plutosgardener2631]

@Sune Wallentin Goettler i need a science fiction with these beings in it please

[@cplcabs]

Its not flipping, its reflecting.

[@user-qx7tm5df8j]

the physical pain watching this video 25 seconds is unbearable..

[@danzigvssartre]

To turn a “q” into a “p” I need to flip it by rotating it out of the plane by 180 degrees. When I see my mirror image I think it is me rotated 180 degrees and looking back at myself. But it is not, since if I was looking back at myself and both my “selves” raised our right hand we would raise the contralateral hand but in a mirror when I raise my hand I see the ipsalateral hand go up. This is because a mirror is a reflection in the plane and not a rotation in 3D space. To see yourself in a mirror is not the same as seeing yourself in 3D space as others see you. I noticed this when I once looked at my cat in the mirror. She had asymmetrical markings on her face and she looked weird, yet this is the only way she would see her face. In short, flipping is not reflecting.

[@p.k.4412]

Where do these people come from. Maybe another flat earth 🌍 conspiracy

[@xylitus2830]

P. K. Flat earthers have members all around the globe. A globe is spherical. Flat earthers proved wrong.

[@hj8607]

In big print put number 813 on a piece of paper, underline number . Hold in front of you in front of mirror . With fingers on sides turn the paper over , top to bottom, to show to mirror . The number in mirror will be 813 (not E18). But the line, of coarse, will be on top . A vertical FLIP .

[@twinheatingairconditioning135]

Miss her as physics girl i hope she can recover she seems like a wonderful person our prayers are with her

[@toujourslamour7573]

Very nice explanation, Physics Girl. Thank You!

[@BobKerns4111]

YES! Someone finally gets it right! Further (and you hint at this with turning the glove inside-out), it converts right-handed coordinate 3D coordinate systems to left-handed. If you have X and Y axes on a piece of paper, which way does Z go? Two choices, toward or away from you. This video would be a great step toward introducing 3D vector cross products.

[@touristguy87]

The Z axis can go only one way, normal to both the x and y axes. The question of which is the positive Z axis is answered by the right-hand rule. By convention. In engineering terms it is orthogonal to both the X & Y axes. By the way. I'm quite sure that someone "got it right" long before this. Thank you for playing.

[@Physics072]

@@touristguy87 I think many lay people got it wrong but its not there fault. It depends on how you present it. Its not incorrect to say the mirrored image will appear horizontally flipped compared to a photograph. It will, it does not say who is doing the flipping or why. Most people experience life looking at others and knowing that the hand on the right is really that persons left hand. (well some people are just terrible with left and right period) but you get the point. Some where along the line people started saying the mirror does the flipping. One can make a case that the mirror is responsible for this illusion and most people can get by in life just fine remembering that that a mirror image means its flipped on the horizontal axis and bi-convex lens creates a real but inverted image (Flipped on both axis) Again its "Appears" to be z axis flipped but its not actually doing that either (that is part of the illusion) Do you really think the mirror is pulling your eyes to the back of your head and then re-bending your arms to bend the opposite way? That is not what is happening in reality, but it sure looks that way as the video demonstrated.

[@maek234]

When she flipped the paper upside down my mind literally broke. I thought it was fake for like 30 secs because I wasn't used to it

[@edumaker-alexgibson]

Instructions unclear. Now trapped in the mirror, and everyone around me has a goatee and is weirdly keen on violence.

[@junkmail4613]

Just came here to say, "Get well kiddo!"

[@krmusick]

That bit with the glove was/is brilliant.

[@krmusick]

+Appleholic1 You have obviously never had to explain things to a young inquiring mind. The visual analogy is brilliantly simple in a repeatable and reversible way to show what is happening with the reflection. This video wasn't made for people that understand the concept, it was made for those that don't. Just because you have a clear understanding doesn't mean everyone does.

[@bonbonpony]

+DIAFYFC And actually the only correct one in the entire video.

[@yhadisaputra]

Physics: Complicating Everything Since The 1600's

[@maxducoudray]

Physicists: enjoying complications since the 1600s

[@ArchWayE]

🤣😂🤣😂

[@nishtakasundass6669]

Physics is theoretical but the fun is real😂😂😂😂

[@spacebarbarian._]

It's the same physics that developed tech nd made it possible to write this comment

[@nishtakasundass6669]

@@spacebarbarian._ Of course!!!! *physics is more than just important*☆

[@somefreshbread]

If you hold a transparent piece of paper up that says FOOD to a mirror, when you look through the paper, it'll look the same as it does in the mirror. That's the bit that helped ME understand.

[@drock5404]

The t-shirt thing cleared it up for me. Thanks for an answer to a question I've never asked myself!

[@karlhendrikse]

I think all the people saying this video is too obvious have never even considered the question it's trying to explain the answer to. It's not about how mirrors work, scientifically. It's about *why* we instinctively perceive mirrors to flip things horizontally rather than vertically, psychologically. Anyone who claims to never have been confused by that "paradox" is either lying or has never thought very much about mirrors.

[@enshk79]

Karl Hendrikse you serious?

[@raulj5313]

Mirrors dont flip, they reflect. The end.

[@Bongoslam]

^This

[@andrewthenoble]

What do you mean by reflect? This video describes what a reflection actually is. A reflection is an image reversed in the direction perpendicular to the mirror surface. Saying “mirror’s reflect” is really just saying they flip in the z-direction. Asserting that mirrors don’t flip is incorrect.

[@raulj5313]

@@andrewthenoble a mirror reflects the exact image that's in front of it. Mirrors dont flip. The end.

[@andrewthenoble]

Raul J You’re completely missing the point. How would you describe a reflection without using the word “reflect?” This video is describing what it means for something to be reflected. Your comment is the equivalent of saying the definition of a reflection is “a reflection.” That doesn’t explain what is physically happening.

[@raulj5313]

@@andrewthenoble what? Lol. I said "reflects the exact image". The content is about reflection, so therefore there is no reason for me to be more specific about a mirror. Also, i'm not going to waste my time with someone who spells "your" the wrong way. Enjoy your day.

[@Dausuul]

That's brilliant. I'd wondered this occasionally and never figured it out. Now it makes total sense.

[@CutcliffePaul]

Of course! The best explanations leave you wondering what it was you didn't understand before considering them. 🤯