How does a two-way mirror work? - Big Questions - (Ep. 24)

[@Goblin_Mom]

The only problem with your technique for checking is that if someone is watching you, you have now pressed your face right up against a mirror that suddenly has someone looking at you from the other side, and getting really close to a piece of glass and unexpectedly seeing someone right there is probably the easiest way to make me shit my pants.

[@Tfin]

You're only doing it if you already suspect someone is there.

[@Goblin_Mom]

I'd still drop a deuce at the sudden appearance of a human inches from my face like that

[@hermes2002000]

That would only be a problem if you had no idea it was a 2 way mirror. Just by trying it, you show suspicion there is someone there...

[@Goblin_Mom]

Gustavo Moreira Y'all seem to be underestimating how horrible the idea of coming close to a pane of glass and finding a face directly on the other side is to me. Honestly the anticipation would probably make it even worse than if it were a complete surprise. Sudden, unexpected something would be startling; long moments of anticipation, my imagination filling in the gaps of what could be there, the time between me registering something there and realizing that it's just a human, not whatever monstrosity my imagination was able to come up with, that's why I would poo my pants.

[@beans8474]

​@@Goblin_Mom the 300 iq play by the guy watching is to press his face in the glass

[@BinkieMcFartnuggets]

So it's basically the same as when it's pitch black outside and no one can see me staring inside their house, but I can see them.

[@MagikarpMan]

A bit Sus ngl

[@JennieKerfuffle]

What an odd coincidence. When light bounces off my mirror, I, too see a very handsome bearded man (which is concerning because I am a teenage girl...or maybe it's not concerning at all).

[@sensibleb]

You might want to invest in some tweezers. No judgement here, though.

[@barduk4]

a teenage girl has more facial hair than i do ;-;

[@leechtamer]

Do you live in Night Vale?

[@weshard1]

The two-way/one-way mirror I installed only cost a fiver on eBay.

[@alannar.8701]

leechtamer And now, the weather.

[@spandanmusser]

This guy is so funny. I'd love to see him do more of the mental floss videos.

[@Wafflical]

Why would it be called a two-way mirror? Wouldn't that mean that it's either a mirror on both sides, or transparent on both sides? One-way makes way more sense.

[@markstanko8312]

Two-way mirror means that it works in 2 ways, it both reflects and is transparent at the same time.

[@Wafflical]

Mark Rocknrolla Ok, that makes sense.

[@babis8142]

so what would you call a normal mirror? A no way mirror?

[@Wafflical]

babis8142 Well, if you took it off the wall and looked at the back of the shiny metal part, that side would also be a mirror. So it's a two-way mirror.

[@markstanko8312]

babis8142 No it'll be called WHAT THE FUCK WERE YOU THINKING?

[@skylerluu703]

Wow, working with mirrors is a job I could really see myself doing. 😂😂😂😂😂😂😂

[@chimchimswife7361]

Skyler Luu thats the best pun ever😂

[@MrHeems]

When I was a little kid my parents took me to the Ripley's Believe It Or Not museum. Unbeknownst to me they had a two way mirror. While taking the tour i was lagging behind my parents and i came to a mirror on the wall, nothing suspicious. There was nobody around so I did what kids do, and picked my nose. A little while later i came around to the other side and realized the show i had given people. Thank god this was before the time of camera phones.

[@ferafish213]

About the fingernail test: www.snopes.com/crime/warnings/mirror.asp There are two types of mirror. The first is the kind you normally see, with the reflective stuff on the back of the glass. The second has the reflective stuff on the front of the glass. Now, the second kind is more expensive, and not typically used if it's not needed. It is also the kind used in two-way mirrors among other things. The fingernail test can be used to tell the difference between the two types of mirrors, but a number of factors can make it look like you're touching your reflection when you aren't. The ways listed in the video are the best methods to test for a two-way mirror. Another big hint is if it's oddly bright. For example, bars aren't known for being well lit. If you walk into a really bright bathroom, be suspicious.

[@JennieKerfuffle]

I have a burning question. What is room temperature? Is room temperature subjective to your location? Like, in Alaska, "room temperature" is probably much lower than what would be considered room temperature in the Saharan Desert.

[@RDSk0]

Long story short, "room temperature" can mean either: a) Exactly 20*C=68*F. b) The temperature in the room

[@pythor2]

It's not subjective. Room temperature in most calculations is just one temperature, 25C.

[@waaa9waaa9waaa9]

In scientific context it usually means a specific temperature where humans could live normally, around 20-25 C. Otherwise it literally means the temperature of the room you are in.

[@ghuegel]

For determining expiration dates for drugs, the definition of room temperature varies by country. I know that in the US it's 22.5°C and in some hotter places (e.g., Brazil), it's 30°C.

[@starlinguk]

Matthew Motooka Do they keep rooms that warm in the US? How can anyone afford their heating? My thermostat is set to 18C, which is pretty standard around here.

[@allsingersme]

There's also the fact that if you put a finger on a two way mirror, there won't be a space between you and the reflection like there is on a normal mirror.

[@ThatShyGuyMatt]

Craigs really grown on me as a host. Hes perhaps my fav one now (not counting the Green brothers of course).

[@Babagump]

What time is it on the "North/South Pole"... I mean around the point where all the time zones come together...Not magnetic or geographic(if that's not the same one)

[@RDSk0]

I believe its UTC.

[@weshard1]

Party time.

[@MidtownSkyport]

Don't know about the north, but at the south pole it's UTC+12/13. Google "time zone map antarctica", it's pretty interesting and not exactly logical.

[@ewan.cartwright]

but you could dance around the north pole and end up constantly having your watch wrong!

[@Babagump]

thx

[@lunevermeil1400]

When Pa bought this house, there was a bolted door for the bedroom, and a two way mirror. There were also latch rings bolted to the ceiling and floor, positioned to secure someone or something. He quickly removed them.

[@tanner1ie]

They don't show how light specific two way mirrors are in most police shows and films, but in one of the Police Academy films they did :) . In a scene a witness is nervous about identifying a suspect and a cop, Harris i think, reassures the person saying, "Don't worry, they can't see us, it's dark in here and bright out there." The witness then correctly picks the criminal, but just as they do, one of the new police recruits comes into the darker room and turns on a light, revealing the witness and criminal starts shouting he's going to kill the witness, who panics and says, "I was wrong, it was the priest!" :) .

[@Quantiad]

More of this guy please!

[@christine2689]

I like the video presentation. Bite-sized but sufficient in info

[@DtWolfwood]

What of the two way mirror public bathrooms? Now peeps know how to peep into those! XD

[@JulieFromSchool]

sometimes i miss when john used to host most of the mental floss vids but then i remember that he chose prob the BEST POSSIBLE people to step in they're all great

[@ewan.cartwright]

I remember we were doing a play that needed a big mirror as part of the set; we got a one-way mirror. We thought 'Perfect! The audience can't see us, but we can watch all the action!' (I was part of the crew) But it turned out when we had low lighting on you could see right through the mirror and everyone behind it.

[@TG-Maverick22]

Craig is the best!

[@rvrmdude]

I like how you just straight up answer the questions while Vsauce is good sometimes it just goes on and on.

[@jlindsey9946]

Interesting topic never thought to ask this question before...

[@ahorrell]

Craig is great. My favourite non-Green presenter.

[@catinabox3048]

My department uses two-way mirrors for professional development purposes. It allows the entire pool of new grad student instructors and their supervisor to observe the same class session and discuss it afterwards, without the undergrads being intimidated by it. It also gives new instructors the chance to lead a class and obtain feedback from the entire group.

[@EricsWisdom]

nice video, as always

[@LuckoftheKevin]

Why do people forget their dreams so quickly after waking up?

[@hthree7857]

grab paper and pen as soon as you wake up, while you're at that, keep the dream repeating in your mind. then write it down

[@millionsofpeople9414]

i had a dream for an hour, but i still remembered it for a few seconds after i woke up 🤔

[@BakerbrothertvOfficial]

*If you put your finger* on a two way mirror, your finger will *touch the reflection* with *no gap.*

[@RDSk0]

Nope, that's just tells you if the reflective sheet is in front (no gap) or behind (a gap) the glass

[@BakerbrothertvOfficial]

KinRedysko Oh...

[@MrFlameRad]

Spind only super computer robots would see that gap

[@ZBWorth]

If you heard this fact from tumblr, word of advice: Double check every 'fact' post on tumblr. Even the ones with sources. Tumblr is possibly the most gullible website on the internet.

[@BakerbrothertvOfficial]

My mistake.

[@antivanti]

The thin reflective metal layer is also usually just on one side of a tinted piece of glass. That way the reflected light on that side doesn't pass through the tinted glass at all but light from the observers side is partially absorbed. On the observers side light that passes through the reflective layer gets absorbed just once while your own reflection gets absorbed by the tinted glass twice. At least this is how my very cool looking mirrored pilot sunglasses are constructed =)

[@sooth15]

Regular mirrors also have a backing paint to protect the silvering, where a two way mirror won't. If it does have a protective layer, it will be clear.

[@theotakux5959]

I've never had trouble seeing through two-way/one-way mirrors just by looking at them, but I've only been around them at places like restaurants and other businesses, never places like an interrogation room.

[@adamthornton7880]

Which raised the question of why interrogation rooms are always so dimly lit in cop/detective shows.

[@wisperingiron3646]

It should also be possible to remove the reflection of the mirror using a couple of polarisation filters (one linear filter and a quarter wave filter). In this way both of the rooms can be bright and you can still only see one way through the mirror. Another interesting fact is that you can see the effect of a regular one-way mirror when you are in a bright room at night looking through a window. One the inside you can clearly see your reflection but hardly see anything outside. If you stand outside the opposite will be true.

[@ohohvalerie]

The best way to tell is to put your finger up to the mirror like you're pointing. Whether your finger touches its reflection directly OR there is a gap between your finger tip and it's reflection is the sure-fire way to distinguish the two. I learned this in undergrad while using 2way mirrors for clinical observations.

[@ZBWorth]

Thats false, it only tells you how the mirror is made.

[@blazingfire7517]

The fact that it doesn't work all the time makes 2 way mirrors make much more sense.

Question: Why does pressing our skin against something with a texture for a time leave an impression in the skin?

[@DodiTov]

It's the water in your skin. Our bodies are made of over 80% water, including your skin. The pressure of the surface makes the water move to fill the available area, which makes an impression in your skin. It disappears by the same method, because your skin encloses the water like a balloon.

[@barduk4]

cool now that i know how it works im going to make an inn and put 2 way mirrors in the bathrooms.... i mean... i am glad to have learned something new today it is always such a wonderful time to be able to add knowledge to my brain.

[@mrosales7307]

The real question is . Who is this Meredith and how does she do it all?

[@crazycolbster]

Why does getting your back scratched feel so good?

[@knuxzero1]

I was told as a kid, idk let's say '97, that if you put your fingernail up to, essentially poking a regular mirror, go try in your own bathroom, there appears to be a gap between your fingertip and the reflection of the fingertip. However, now I sort of remember confirming this at this place (Whirly Ball anybody? Actually there's probably only the one here around Dallas, but ANYWAYS as I was saying) that has a one-way/two-way mirror but it possibly a false memory who knows, but the point is if you put up your fingernail like that on one of those mirrors it looks like your fingertip and the reflection's fingers are touching. If someone can actually testify to this or disprove it feel free to let me know, but I remember being told that in school when I was probably 10 or 11 y/o in Health class to check in dressing rooms if the mirrors are have cameras behind them. They usually don't but some places have that to prevent shoplifting -or so I was told- but they have to have signs posted but not necessarily in the dressing room and that's why you can check by poking it. Like I said correct me if I was fed lies as a child.

[@zorod5475]

Who designed the times new roman font. and what was the first publication in that font?

[@loveamerica587]

Would it work good for the pool room? you can change inside still see the swimming pool outside safety concerns

[@CliffRoth]

Forgot the best way to tell: hold your finger to the mirror. If there is a gap between your finger and it's reflection, it is likely a regular mirror as the gap is the glass.

[@lorette2443]

Hi, can we get one bigger image if we assemble 2 or 4 mirrors close to each other?

[@shawniscoolerthanyou]

Bored During School sure asks a lot of questions.

[@BakerbrothertvOfficial]

I too see a *bearded man* in the mirror which is *strange* because I'm only *17*. *The doctors say I'm special.*

[@omerlandau]

1:29 where did that fish go??

[@benaaronmusic]

That fish disappeared like Austin Powers.

[@nothingisright9]

I spent four days watching all the videos uploaded via Mental Floss, and I am surprised that some of the information gets repeated a few times. Just curious, what happened to Hank's quiz series? I am assuming it didn't catch on or it was moved to another channel. Off topic but I kinda want to see what where land mark cartoons or television series. In other words, an evolution of shows from shorts, to two hour dramas; from national funding to cooperation funded; from shows promoting propaganda to cartoons showing controversial issues about the nation that it, itself is aired in. For a list: probably would want to see strange laws in different countries excluding laws due to religion (because that could be a series of episodes). For a misconception: a list of misconceptions about methods of how to tell if people are lying. For a question: Well, Sense Craig AKA "where's John Green?" (As said in the coffee episode) enjoys coffee a lot, I thought It would be proper to ask, what is the best and most effective/efficient thermos

[@rizzoid]

Who would win a staring contest when looking at a mirror? Craig or Craig's reflection? I bet neither would blink.

[@nikkigriffin6441]

Another way to tell is the gap test. If for example if there is a spot of dirt (or something else touching the mirror) if you look closely there should be a gap between the spot and the reflected image of the spot. But in a two-way mirror, there is no gap so the spot of dirt would look like it's touching the reflected image. My psychologist office space has a room with a two-way mirror and when I tried it I couldn't see a gap.

[@GeoffShouldWin]

Are fireplaces and effective way to cool your house during the summer?

[@beyourselfth]

You're my favorite.

[@PeterBarnes2]

My favorite number is three. I came to this video expecting to learn about glass. I already know how one-way mirrors work from minutephysics!

[@KyraTheFallenAngel13]

I have a question. Why do we get goosebumps when we are listenting to (certain) music?

[@wblanco329]

Lol this guy is hilarious

[@benrice2793]

BIG Question for next week, what is going on with the fish at 1:31?? Fake fish tank or teleporting fish?

[@virtlink]

I was surprised that you didn't mention the two-way mirror you're looking at to see the script, through which the camera films you.

[@biofungus]

I have a question: how come if you get a nose bleed and some of the blood goes back into your throat, it makes your throat sore?

[@bigfoot722]

Where do the numbers in street addresses come from? Why do they get bigger when you are further from downtown and smaller when you are closer downtown? Are they some sort of unit of measurement?

[@SargentTNT]

How did the shapes get their names?

[@ljmastertroll]

The mirror is hanging on the mounted surveillance camera so I'm safe.

[@Purplesquigglystripe]

Holy fuck! There's a giant mirror entirely covering one wall of my living room.

[@slwilson21]

How are subtitles added to movies and tv shows?

[@victortrejo5725]

I have a question: why do we have 60 seconds in a minute and not, for example, 50 longer seconds or 100 faster seconds? On that route, how did this whole 24 hour thing come about? Did it start with 24 and then get subdivided or start with seconds? Why does second mean 2nd and 1/60th?

[@CarstenSvendsen]

but how does the white interrogation rooms in "Lie to Me" work?

[@vibinwnadia1422]

*checks every mirror in the house*

[@kid12j]

So...that Spongebob episode where Ms.Puff turns on the light on her side of the two way mirror was actually correct...

[@trulystunningdesigns]

When I first read the question, I thought to myself, "A two-way mirror is just glass. It's merely a window." but now, I'm not so sure...

[@Tonzor]

You still havent answered my question which is on the same subject: What would a cube made of two-way mirrors look like? With the "mirrors" pointing inward that is.

[@cynvii]

Okay, I have a question; where did the idea of using flowers (and/or food) i.e. sweetpea, buttercup... maybe cupcake for the food part, as terms of endearment come from?

[@408lynn]

I've met these mirrors in BR of small restaurants and upscale gas stops stores.

[@BQuanchi]

How did he know that I see a handsome bearded man when I look into a mirror? I must be using a two-way monitor while watching this video...

[@rubenlopez670]

Is sneezing attributed to all mammals, and do other animals sneeze?

[@LLyt82]

**Another test is to press the tip of your fingernail against the mirror. If there is a space/gap between your fingernail and its reflection, it's a regular old mirror. However, if your fingernail and its reflection actually touch each other, then it's a 2-way mirror.

[@hazelmaple]

question that has been bugging me forever. what is the speed of time?

[@TSIVF]

1 second per second

[@TheNukedNacho]

Ask Atheon, Time's Conflux

[@lukejohnson6415]

No speed, it can change

[@StrawhatAndrews]

Time doesn't have a speed, time is relative to speed

[@Sensorielle]

Time is relative to gravity and spatial position.

[@emiakari2871]

I have a Big Question. In ancient times (say 2000BCE) what did women do instead of using a pad or a tampon while on their period?

[@dave5194]

Yep, I like to think of them more as a one way window, makes more sense to me. Its the same reason why you can see into someones room at night when its bright inside and not a lot of light is reflected outside and not in the day, when its bright outside and there is a lot of reflected light... not that I stare into people's rooms with binoculars or anything, ha.ha.ha...

[@charlietuba]

You can also touch a pencil point to the mirror. If there is a gap between the pencil point and its reflection, then you have a regular mirror. If there is no gap, it is most likely the mirror is two-way one.

[@brandonperalta409]

Another great way to check for one way mirrors is to place your fingernail on the glass. In a regular mirror, your fingernail and it's reflection should have a tiny space between them. In a one way mirror, the fingernails will come into contact.

[@ZBWorth]

Thats false, it only tells you how the mirror is made.

[@jasong6471]

question for future episode - How does a ship sail into the wind?

[@fep_ptcp883]

What is the theoretical maximum mass (and diameter) for a star?

[@amandar198913]

I have a question! It may be a stupid one but I've heard many different answers and I think you guys at mental floss are much smarter. Why do we yawn? And is it really contagious?

[@thombingham-hall1408]

whats up withe the fish at 1:31

[@missyevitt1771]

How is sound recorded on a record?

[@Louiseybabes271298]

Also to test if a mirror is one/two way by putting the end of your fingernail on it and if there is a gap it is a normal mirror but if not someone is probably watching you

[@innocent_fugitive]

My trick for finding two-way mirrors: Put your finger against the surface of the mirror; if there is a gap between your finger and its reflection it's likely a regular mirror. No gap, it's likely two-way unless you are somewhere where they are likely to have expensive, first-surface mirrors. This isn't foolproof though. See Snopes for the whole story.

[@Belboz99]

I usually use the term "one-way mirror" because there's 2 sides, and only 1 is acting as a mirror. One direction is a mirror, one direction is a window, and one direction is a band... oh... wait...

[@hoodedbob]

How were different languages originally translated?

[@Ryesagain]

Ive seen a tip on two way mirrors; and thats if you put your finger on the glass and the reflection is touching your fingertip, it is a two way mirror. Though I might have it wrong/backwards, and that if the reflection has a slight gap, about the thickness of the glass it is a real mirror. Is this a tip for fingur-ing it out or am I misinformed??

[@reinaldomartinez13]

finally answers

[@UchihaMember23]

If you put your finger on a two-way mirror, your finger will be touching its reflection, but if you put your finger on a "normal" mirror, it would look like there's a gap between your finger and its reflection,. :)

[@sarahbyington2440]

They look darker too. To me it was very obvious that it wasn't a normal mirror, not as bright and "reflective" as a normal mirror. FYI two way mirrors are used for more than just police interrogation. When I was in speech therapy they used them so the supervisors and my mother could watch. My 8 year old self figured it out within the 2nd session.

[@BlazingLightSword]

Supposedly there's a way to test if a mirror is a two-way mirror, with just 1 finger. If you touch a mirror with your finger and there's a gap between your finger and the reflection, it's a regular mirror. But if you touch one and there isn't a gap between your finger and the reflection, it's a two-way mirror. I can't remember if I've actually tested this myself, so I can't say it 100% works...

[@ZBWorth]

It's false. It only tells you how the mirror is made.

[@NayNayyyyyyyy]

EVERYONE YOU CAN ALSO CHECK BY PUTTING YOU FINGER ON THE MIRROR IF IT TOUCHES ITS A ONE WAY IF NOT ITS A TWO WAY

[@tr3kfan940]

My big is were chickens ever wild and, if so, when did they become domesticated?

[@maxmey10]

What came first clothes or a blanket?

[@3benjamins]

I have a question: Why do birds fly in v-shaped formations when they are migrating?

[@Chouetterargentee]

Can't you put your fingertip against the glass and judge whether or not it is a two-way/one-way mirror based on whether there is a gap between your finger and the reflection or not?

[@ZBWorth]

Nope, thats false. All that tells you is the way the mirror is made.

[@elmore83]

I can't vouch for the science behind it, but I've heard this before and I do know that I tried it with the 2-way mirror at my old job and there was in fact no gap, as opposed to the gap when I've touched any normal mirror. I would say it's probably at least "common" for 2-way mirrors to be built like this, if not a fool-proof way to tell.

[@cecilyk2406]

is the whole 'no space' thing true?

[@michaelwoodard7011]

Question: When you wake up in the morning, or if you leave a dark room after a while, why does light "hurt" your eyes? And, why does it help to keep one eye closed for a little bit while you adjust?

[@andrewcaldwell5026]

The distance between your finger and it's reflection only tells you how thick the glass is