What Happens if You Focus a 5W Laser With a Giant Magnifying Glass? Negative Kelvin Temperature!
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- čas přidán 15. 05. 2024
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In this video I show you what it means to have negative temperature by focusing a laser beam down to a single point. I show you what happens if you try to focus a light down to a single point, then I show you how a laser is different due to population inversion.
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I see a lot of people are having trouble with this video. First, I am very much aware that the reason the laser it getting hotter when it is magnified is due to the reduced area. That isn't the point of this video. The point is to try to explain why it doesn't break the laws of thermodynamics! Now for the negative kelvin explanation, statistical mechanics tells us that at infinite temperature all atomic states will be populated equally. The Kelvin scale was built upon classical mechanics where it would be impossible to achieve a state in which there are more atoms in a higher state than a lower state. However due to quantum mechanical effects, we know that we can stimulate atoms to be in a higher energy state simply by shining light near them that is at the same wavelength as the light it would emit at that state (stimulated emission). So in a laser, the stimulated atoms actually achieve a population inversion where there are more atoms in a higher energy state than a lower one. This is where the negative temperature comes from. In this case we have to define temperature as negative or else we get into problems that break the second law of thermodynamics. It doesn’t matter that my laser has poor optics. What’s important is that lasers can break the conservation of etendue due to the fact that they have light that doesn’t spread, the reason they have light that doesn’t spread is because of population inversion, and this is why we have to say they have negative temperatures (or they behave as if they have negative kelvin). We can never achieve negative temperature in a non-quantum mechanical system thus anything the laser shines on is always at a positive temperate no matter how hot you get.
Of course the reason the laser gets hotter when it’s focused is due to the reduced surface area of the light. That was not my point though. The point of the video was to explain why it doesn’t break the 2nd law of thermodynamics. Please research “conservation of etendue” to understand why you can’t focus a flashlight down to a point that is hotter/brighter than the flashlight surface. This is a very good example of how the second law of thermodynamics can never be broken no matter how hard you try.
Ayyy
HIIIIIIIIIIIiiiiiiiiiiiii :) cool study
You should have mentioned etendue in the video! Perhaps even link to the xkcd "what if" essay on this topic. Also, cross reference the Nottingham video on negative temp. and population inversion.
The Action Lab negative zero is equal to zero so saying the hottest temperature possible is negative zero kelvin is to say that zero kelvin is the hottest possible temperature which is completely nonsensical because zero kelvin is the absence of any vibration within the molecules and the complete opposite of hot by every sense of the term
Edit: I made this comment fully believing it to be true but I have learned more about the subject and found out that I was wrong, but I don’t think I should delete the comment because it is important to admit your mistakes and not hide them
Every ant killer with a magnifying glass knows you’re just concentrating the energy into a smaller point. It’s like shooting a gun. You take the full force of the bullet in the kick back of the gun but the gun body doesn’t go through your hand. The bullet is smaller and concentrates the energy.
If you break thermodynamics, I'm not buying you a new one.
Congrats. You have ((3!)²/2)-9 likes.
Edit: I now have ((3!)²/3)+2 likes! Thanks
Edit 2: damn this comment is 5 years old, 14 year old me was probably better at math than I am now
Or 9 likes
Jloc in that case I'll just get it insured then!
It’s not even that hot he is over estimating it if you want to see an actually smart laser CZcams channel go checkout styropyro
You're not my real mom.
Sweet, now we can finally build that Predator shoulder cannon.
u n d e r r a t e d
You welcome.
US army already owns it
Word
I love that this was under that huge technical explanation of who what how 🤣🙃😂
To prevent the flashlight beam from spreading out, you could easily place a fresnel lens in front of the beam to straighten the light into a single direction, then just put the magnifying glass after that to concentrate all the light from the flashlight down to one point.
I was just thinking the same thing and went looking for the comment to thumb-up it 👍
@@mihailghinea I suggested using an aluminum lined funnel to concentrate the light output of the high-lumen LED light. A conical Erlenmeyer flask that is painted on the outside with silver paint could also work--although it would probably be best to remove the base of the flask--which would require more work.
It work ether if you put two magnifying glass at the right distance
then do the same thing to the sun
That's exactly what I was thinking. Like a 6x6' fresnel. I love melting coins with fresnel lenses it's wild.
I google searched "What happens when you point a laser at a crystal ball". I found this and learned so much. Awesome video.
I never thought Kelvin could be negative. I mean, he has such a good outlook on life.
Took me a second
You mean such a positive outlook?
Oh I get it because Kelvin isn't a person, it's a measurement. But you're making it sound like a human that is optimistic. (Screams in braille)
P
Scientific dad-jokes = whoosh
“-0 Kelvin”
understandable, have a great day
Lol
"if anyone has any questions please post them down below"... Nope. Everyone is fine down here. I didn't burn down my house. I used the second law of energy to make the light force to flow into the dark force with negative zero Kevins.
Y E S
This is why I have trust issues
But I've met girls hotter than -0 Kelvin.
Literally the best CZcams channel to be sure you are going to learn something new every single video!
I plan to view this several more times so I can get a better grasp on this. I heard about the Kelvin temperature scale when I was taking chemistry in university in 1976 and was always fascinated with it.
the units aren't super important although 0k is absolute 0. other than that this didn't make a whole lot of sense to me
I wouldn't listen to this guy. In the last video I watched he talked about relativistic mass which doesn't exist. I played this one to see if I would be blocking this channel because it's wrong about stuff and yes I will be. He is wrong about the flashlight, I have no idea why he is going on about breaking thermodynamic laws by simply focusing energy, and he is wrong about negative kelvin. You should check out the fermilab channel for better info on a lot of things.
@@odizzido Negative Kelvin is absolutely a thing, there are numerous scientific papers about it. However, it's unintuitive based on classical scientific models. Sixty Symbols has a video about Negative Kelvin that is actually quite informative!
@@DapperDanLovesYou I don't remember what these comments are really about anymore but I do enjoy educational content so I will check that video out, thanks :)
A flash light emits defused light and so does the sun...
\|/ defused light
• dot is source
A laser is concentrated light. Ideally, we want all the laser rays to be parallel (direct light)
||| direct light
• dot is source
however when I look at a laser dot ( just how you showed us with laser close and far away) I see the dot get smaller at a distance... That means, the rays aren’t emitting perfectly parallel from the source(laser) but most-likely they are converging a bit.
/|\ converging light rays
• dot is source
now a magnifying glass also converges the light (but much more drastically) depending obviously by the type of lens. so laser plus magnifying glass will look something like this.
. -small dot is where the light focuses
/|\ -converging lines due to refraction
- -horizontal line is magnifying glass
||| -parallel light is laser rays
• -big dot is source
now we do the same with a diffused light source.
o - o is light on wall
\ | | | / -some lines refract to parallel
- -horizontal line is magnifying glass
\|/ -defused light rays from source.
• -big dot is source (sun or flashlight)
a ‘theatrical spot light’ is kinda like a laser but even though it emits rays more parallel than the flash light, it still does not converge the light rays all on one very small spot like a laser does.
now you must also understand what happens when light goes past its focus point
i’ll copy the laser diagram and extend the light past the wall.
\|/ -rays diffuse past the focus point.
x - x is the focus point
/|\ -converging rays due to refraction
- -horizontal line is magnifying glass
||| -parallel light is laser rays
• -big dot is laser source
as we see, rays past the focus point will start to diffuse out. I have seen this happen with cheap lasers where the rays aren’t perfectly parallel (the rays converge a bit)
when i point the laser at certain distances it it will make different size dots.
at point blank the dot is source size
at a bit more far, the dot is smaller because the rays are converging closer a bit /|\
if we can find the right distance to find the focus point, thats were will get the smallest spot of light.
if we give even more distance and so the light can pass its focus point, then we will see that the laser light will start to diffuse out just like flashlight rays \|/. Becoming practically a red spotlight (if it’s red laser)
you will notice this by seeing bigger less intense spots on walls(i did this outside from balcony to distant buildings)
at a very far distance the laser light gets so diffused out that the spot totally disappears giving this cheap laser a limited range. good quality lasers will try to emit as best they can (perfectly) parallel lines so that their focus point can be as far away as possible to give them a much better range(not the only reason).
lasers aren’t just perfectly parallel rays, they are also very many rays in a very small area(intensity aka concentrated light)
and usually the laser has a color because its mostly just one type of light that the laser is shooting. white light is all colors of visible light.
on this video i don’t get what you are going on about with negative kelvin etc
lasers just focus and concentrate light.
A laser ‘BEAM’ is focused and concentrated light!
light from the sun or a flash light is drastically dispersed(not concentrated and focused)! that means there are “MORE RAYS” of light hitting a “SINGLE SPOT” with a laser source(i’m ignoring the frequency) than with a flash light or sun source
also if what you say is true, then why isn’t your laser hot enough to burn right through your wall in less than a nanosecond, since you say its ‘beyond’ infinite kelvin..
why does it take time to burn the wood? maybe because it not as hot as you claim..
its just many concentrated rays on a smaller spot area than the source area.
lets say the source rays is 3 dots
••• (front view of the laser hole)
if we focus those rays in a single spot
• (view of spot on the wall)
thats 3 rays overlapping the ‘same amount of area of just one ray source area.
so technically that spot is 3 times hotter
than the one spot from the source, but has the same energy of all the 3 source dots added together.
now the light coming from the sun is just like many dots emitting light ••• but every dot emits diffused(scattered light)
sun surface is made of many ‘dot light sources’ that emit diffused light.
like this:
\ | / \ | /
- • - - • -
/ | \ / | \
\ | / \ | /
- • - - • -
/ | \ / | \
and the sun at a distance is just considered a dot light source as well.
sun:
\ | /
- O -
/ | \
like we see stars
so the only reason why we see stars even though they are so very far away and emit defused light, is because they are so VERY VERY‘BIG’( the stars)!!
the surface of the stars that point at us is SOOOO ‘vast’ that we can consider that light source area to be a flat area light(background from CG 3d lighting), therefore its emitting many (nearly) parallel rays towards us (but not converging rays. they are still diffusing a little) and since none of those rays are focusing, it wont burn anything and even if u did focused those rays that do reach our planet, the amount of rays(intensity)wouldn’t be much because most the rays from that star are lost and dispersed in different direction and so we are only receiving a very very small percentage of that light sources rays.
another thing to consider is the angle of attack of the rays with the lens of magnifying glass.
Noice
Holy shit
He is trying to explain why it doesn't break the second law of thermodynamics, the dot of concentrated light can't get hotter than the source of the light, because heat energy can't be created nor destroyed. If you have two tasks of water, one empty and one full and you connect them the full one will fill the empty one until they're both of equal volume (temperature, of course this is just an analogy).
I still have to understand how lasers and flashlight rays made parallel with a special lens are different.
You didn't mention that laser light is coherent but that a collameter is required to direct them into a solid beam. Lenses are used to direct the light and clean up the beam even further. Ussually a three lense or a combination single lense. But I know your point (no pun intended ) was about thermal dynamics. Now his laser if it was a true 5 watt would have created a plasma on the surface which is a direct result of the physics you were trying to break down.
Holy L O N G comment B O I
He:
"negative temperatures are hotter than positive temperatures"
My brain:
*Exploding*
Loll true
Wait, is it really negative, or is it just an integer overflow
Negitive kelvin is impossable
@@UraniumWolfy Not below 0 kelvin, just below 0 degrees
@@somerandomguy7068 0 Celsius *
This is an awesome experiment I wish you had an infrared thermometer where you could measure the heat with a infrared temperature gauge gun or whatever and get it focused on after you put the magnifying glass in front.
Why do I get the feeling the anhilation of this universe is going to be caused by someone making a CZcams video.
*”Hotter than infinity”*
Other side of the world:
Where is this laser coming from?
Sounds like a cat call!
@@benheideveld4617 thanks, captain obvious
@@benheideveld4617 wut
Ben Heideveld ???
@Sebastian Castillo I thought he was talking about "Where's this laser coming from" could be like something a guy says when looking at a random girl who he thinks it's hot, also known as cat calling. The laser, of course, would be his erection. "Where's this erection coming from?"
I'm probably thinking into this too much, though. Or just my dirty mind.
Mom: *eat the food its not that hot*
The food: *hotter than infinity*
That's every mom lol
Kris. Burnt food is worse than nothing but actually something is better than that food is cold weather food from Antarctica
ʏ ᴛʜᴏ ᴍᴜᴍ
444th like?
Dude I don't know what you expect you can't just get to eating the pizza rolls immediately
This would be great to use in the garden to target weeds or unwanted plants.
This is the best explanation I have found of laser weapons. Yes, laser weapons are real! 😁
Everyone gangsta until 0 has positive and negative forms
Wtf. Your profile picture looks like if my sleep paralysis demon's mother had a Facebook account and wanted to post a picture of her son for the first time.
I LOVE IT.
And I thought math was already hard...
@@lepotato135 uuuhh that's the chad
@@kosminn Pretty sure they changed their profile picture lmao.
It’s so Gangsta it’s...SIKKK...
...SSSIKKKNESSS....
First I didn't understand anything. Then I thought I understood something. Then I realized i understood even less. Negative learning.
Yep. This will just go on and on and then you're old, confused and realize you're never going to have the slightest clue what the f#*% is actually going on in the universe -- and then people will start to call you 'wise'.
Shifter C025914 To be ‘wise’ is to simply acknowledge you have no idea what the fuck is going on, but pretending like you do.
@N3ptune
Basically paraphrasing Plato. XD
You just reading my thoughts
I laughed until I cried. That is so true. Negative learning,
That was an excellent video. I learned some things. I never thought about how the 2nd law of thermodynamics pertained to focusing light. Also, I never thought of negative Kelvin temperature before or making a theoretically infinite hot spot with a laser. I'll have to rewatch this video to get a better understanding of this.
Thanks.
Ed Schultheis, PE
Mechanical engineer & manufacturing consultant for 35 years
Schultek Engineering & Technology, Inc.
try your best to forget all that he said because the explanations were utterly wrong. of course you can focus light to a smaller spot to the original surface, it just depends on the curvature of the lens (and eventually also the wavelength and coherence). and focusing something to create a hotter spot does not break any law of thermodynamics.
When I have a question about something I tend to lean towards your videos! I praise the fact you're smart enough to do these things about by yourself:) 5hank you always!! And the talk of temperatures will throw a lot of people off, haha but, trust me you made perfects sense to me! Can't wait to watch all the other vids! :) keep up your good work!
I wonder if a laser could be shrunk to a minuscule point that it could maintain its focus even through water. Maybe sell that idea to BAE 🙃
I'm sure I'm not the only one thinking: *Use another magnifying glass*
Shhhhh he’s not actually incredibly smart he just copies other you tube videos and quotes wiki
Adding another wont change anything
Use 3
No, you aren't the only one...
@@dakotayupyupyup8377 He is smart enough to actually perform these experiments and learns how they all work and explains them in every video. And, no I'm not a fan so I'm not being bias.
this man's bravery is so high that he does not even fear an actual fire in his house
Conservation of energy and thermal dynamics. A splash of entropy, and quantum mechanics! Love this teaching video! Thank you!
This just sounds like integer overflow, but in real life.
To be fair, a lot of things make it seem more and more like this is a simulation... Integer overflow here, 0k being the limit, Lightspeed being the limit, all those limits actually...
@@catdisc5304 other way around. Simulations look like life more hence why opposite is also true
I have a question, not about the comment, or even about the video, but I remember another video by the action lab which explained negative light. Problem is, I can't find that video again to prove to my brother it exists. Help please?
👀, that's because it is
@@amazingfireboy1848 That sounds interesting, I'd like to know too. Sorry I don't have the answer, just leaving my comment in case someone replies.
Me: just studied about negative numbers
You: -0 exists
Me: illegal
Arturo How Long Did It Take U To Finish That Reply
@@Name-cz5jj 5ish minutes? Dang. I thought it would have only taken a couple
Or maybe... -0 has infinite possibilities. Making it infinity.
(Im joking)
Short words
0 can be negative or positive because it is the origin between negative and positive
I know you're trying to make a joke...
And i just found 2 undertale fans in a row
Always funny to listen to your explanations - you never miss the opportunity to strangely subvert physics!!!
yeah... the science explanation in this video is complete bullshit
He did not subvert it. The things he talked about are taught in seconds or even the first year at any university
@@str0fix to assign temperature to laser radiation based on black body approximation is complete lunacy. One has to go energy transfer route to find if ignition point can be reached for particular material. And here is the problem of current generation of Americans - you possess the knowledge, but lack understanding of that knowledge!
Dang this is cool I used to love setting things on fire as a kid! Awesome vid man
100W laser on a 1cm² area is colder than a 100W laser on 0,1cm² area, but both are 100W
is like the 1kg of feathers and 1kg of lead joke, both have the same energy but one is more dense than the other
Wow
Ok?
Exactly. Light from the flashlight (the "source") can be focused onto a small area and result in a higher temperature at that smaller "point" than the surface of the source.
@@Name-cz5jj I'm adding that to my SciFi novel thanks. Dyson Beam.
@@Name-cz5jj the name is Dyson Sphere.
Thanos: *Snaps*
*population doubles*
Thanos: “Negative Infinity Stones!”
XD
Stolen
@@pressaltf4forfreevbucks179 no one cares.
Edit: one person cares.
Panik
@@vixen878 your mom
Your spinning platform, if it's motor driven, wth the plate directly attached to the motor shaft, and powered by Direct current your introducing a whole other rotating magnetic field. Plus two different sized brushes effect your current. You got me experimenting now! Lol thank you! 😊
This is a super cool demonstration, and you've provided an excellent explanation as to why you can't get something hotter than the source with magnifying glasses. Thank you!
Is this comment written by AI
@@RandomGuyVideos Nope!
Can we get more explanation on -Kelvin? I feel like this needs a follow up video to provide more examples of -degrees K and how +infinite wraps around to -infinite.
In a positive kelvin system, more energy = more entropy. In a negative kelvin system more energy = less entropy. Don’t think negative temperature as cold as both Celsius and Fahrenheit are both above 0 Kelvin
@@BGpilot419 Yeah, there are more in-depth videos (and papers and books of course) in this topic, but you really can't explain it without maths.
Honestly, just explaining it in terms of entropy makes more sense to me, but I took statistical mechanics and thermodynamics in college. I'm not the target audience for this video ;)
@@travcollier I remember having similar classes years ago. To me way too much of it came off as total bullshit that nobody wanted to admit to because way too often the stuff they would claim was a real legitimate mathematical formula did not and never would work in reality due to a number of glossed over or totally ignored other real and provable factors.
@@illbeyourmonster1959 The spherical cow in a vacuum effect ;)
The courses I took were a bit more in depth probably. We didn't get into the really difficult complications mathematically, but a lot of those things were at least mentioned. I also took intro thermo in mechanical engineering and chemical engineering as well as covering it in core physics courses. They are all quite different despite supposedly being about the same topic. Then I spent a few years working for a quantum physicist and learned some of that approach (and info theory) on the same concepts.
FWIW: I'm a biologist, so none of this stuff is really in my wheelhouse. Evolution can be described in thermo + info theory terms though, which was what I was working on with that physicist. I thought it was cool, but most everyone else just asked "what's the point, we have our own terms/maths for that."
Maybe he can do a collaboration with Veritasium
6:51 OK...... SOOK..... tOOK....
Kelvin in nutshell
His sub goal
0K 500K tOOK -OOk
never thought I'd see a video about the circular nature of temperature on a video like this, great content as usual❤
this video raises more questions than answers
the only thing beyond infinity is buzz lightyear
SteakCrew why is this not top comment
Baz lighter
Hey, don't post negative comments !!
Bhaskar Pandey ????
I'm very disappointed
“The dot is never gonna be brighter than the original flashlight itself”
Basically me being compared to my dad.
Are you Kurt Cobains child? I get it xD
Ya I could never leave faster than my dad
Your dad is using you as a fl*shlight?
@@venglomarci he didn't say that he said he is like his dad
-0K?
At the start for the flashlight, could you make a mirror tube between the flashlight and the mag glass? yes, some would enter the mag glass at hard angles, beyond the focus ability, but at least all light would enter the mag glass. The longer the tube, the better? maybe a bunch of optic fibers?
So there is a better way to kill ants
The best way is dont killing ants
Underrated comment lmao
Yea
And also burn down your garden/house in the process
@@eulefan We won but at what cost?
In Soviet Russia, negative temperature does no effect to country. Soviet Russia makes temperature feel more negative about itself.
In America we do umm *cough💀* something...
Who else read this in a Russian accent
Majestic Doge to be honest... yes lol
It is not clear what these 4 idiots are trying to say.
the wizzard ikr what are you trying to say
Oh my God I watch all the time and you're geeky looking as I thought you would look , perfect. Love your videos.
To stop the flashlight from spreading out you need a collimating lens then you could focus it to a point but the point would retain the original layout of the LED's in the flashlight since it is not a point source.
Not possible to amplify the power, in fact power is lost through the atmosphere and the lens of the magnifying glass but, the power that makes it through is focused on a smaller area. We would call this watts per square inch. 5 watts focused on a 1 inch square area spreads the power out over the entire area, focus it down to 0.001 inch and the average relative power is increased 5000 times.
You wouldnt be able to focus it to a point smaller than the fuse on each of the LEDs because thats the limit set by the conservation of etendue
edit: by fuse I mean the wire of the LED
There are several LEDs in that flashlight, what you have to do is use one magnifying glass to straighten up the beams so they dont spread out, and then a second one to focus.
This will lead to a brighter spot as the light emitted from each LED is focussed on the same spot
Wouldn't that invert it and make it more spread out
@@mysterynotch9098 it would, the chain would require 3 mag probably
Absolute zero, or 0 degrees Kelvin, is the temperature where all motion stops. It's the lowest limit on the temperature scale, but recent news articles have heralded a dip below that limit in a physics lab. Is absolute zero less absolute than we thought? At the finite focus there is a dead zone where no heat is emitted, 1 Planck Length before or after the heat reappears and remagnifies.
Wrong, the point at which the light begins to converge or even “straighten out” as you said occurs after the light has already spread out too much to increase the temperature above where it started. If you bring a lens close enough to “catch” all the light, you will only spread it out rather than focus it in any way. The simplest explanation for this is that the second law of thermodynamics always holds true, but another explanation would require advanced analysis of optical wave phenomena.
@@loukgoldberg If the first lens is at the right point, where the source is at the focal point of the lens, and the lens is big enough, it can straighten the whole beam. Then another lens would focus that beam to a tiny spot. I don't buy the argument in the video. In optics you can focus a beam down a wavelength size in theory. Using a setup like @DEADBEEF mentioned we should be able to focus the beam to a smaller spot than the source, since the source is obviously larger than the wavelength of the light. There must be another way to interpret this in terms of thermodynamics.
For some reason, my first thought about flashlight/sun was inverse square law, rather than thermodynamics. Where the energy per unit area is based on the distance from the source, and you cannot amplify that energy without putting additional into the output. But, you can use larger area of capture and focus that on a smaller one. That's how parabolic antennas work. In any case, the output will always be a fraction of the source. Lasers have the same problem over large distances.
Yeah isn't there those BBQs where you put a sausage or so in a parabolic mirror's focus? Only works in sunshine of course, although you could probably construct a larger one that also works with cloudy weather 🌭
I mean hey, if you made this thing huge it should even work with moonlight 🤔 Unlike the light through clouds, the latter would even come from one direction, with the moon being fairly far away - although the sunlight gets scattered by the moon before being reflected, as it isn't a giant mirror 🌝 By the way just FYI there's cool videos on "what if the Moon was a disco ball" 🕺🏿
You're right, he's wrong. The energy sums, it cannot go away. It can be hotter in the point of focus, however the total energy will not change. Imagine glass if water. If you move all the heat to top part it will become steam, but the bottom part will turn ice. The total energy will remain same and heat will come to equilibrium with time, turning it back into glass of water. The dude needs set of lenses to actually focus light from led
Maybe because laser runs into objects in the atmosphere or space over large distances.
Hmm what would happen if the laser didn’t hit objects like dust and particles on its way to an object like pure light? With no interruptions what could we do with that? Would the outcome be different? Hmm
@@freerise8754 I tell what happens, photons, as predicted by so much hated theory of relativity, are being fased oud by their relativity effect, on which I wrote dissertation years ago
I'm glad someone had a flashlight like mine. I need a get a new one now though I dropped it in water somewhere in a mud pond and could never find it. Can't wait to learn about cold.
As a math guy, it's _fascinating_ to see a physical representation of a number ring, where negative numbers become greater than infinity. I'm reminded of how complex algebra (imaginary numbers) was adopted by electrical physics. It's great to see these abstract concepts mathematicians dream up to be shown to have practical real-world applications.
In this home we follow the rules of thermodynamics
Homer
I ruin your 69
What I got from this video is that the concept/definition of temperature and the Kelvin scale were not designed to work with quantum mechanics and lasers. You basically have to jury rig Kelvin to get it to work, but you also have to deal with nonsensical sounding results like this.
No, kelvin actually makes perfect sense in quantum mechanics.
Quantum mechanics in itself is nonsensical so don't look for some satisfying answer.
Kelvin is actually a good scale to use since the negative temperature shows clearly that there is something fundamentally different going on with the laser, as opposed to just 'being hotter', to put it crudely.
@@JeromeADavis Nk, you're wrong, quantum mechanics are just really complex
@@jacky9575 That's what's I meant by nonsensical. Things that defy human intuition will make it seem weird or impossible. You have to accept that to even try to understand it, and you still ain't because you can't. Even a top scientist in the field will just break down and cry about this topic.
I am going to make a BFG out of this contraption, Thank you for teaching me this.
My guy, literally calculating a number AFTER infinity itself...
Well that's not the big deal, there are different infinities in math and things like ordinals
Infinty with extra steps.
The problem is, there is no real number after infinity
And telling -1 is bigger than any positive number is not true
@@FreeGroup22 This is thermodynamics bro, not algebra.
pretty sure you misquoted the 2nd law there when erroneously claiming it's impossible with a normal flashlight. simply get another, closer, lens to collimate the rays before focusing them to a point, and done. the second law doesn't say you're not allowed to build refrigerators. it simply says they don't build themselves. and what you do with a lens is not "increasing temperature" but redistributing its target area. it's still the same energy being impacted on the target, just instead of flooding the room with low energy _per area_ you focus it on a single spot that then gets way more energy _per area_. your laser itself literally proves it's possible to make the target of some radiation "hotter" (= more energetic) than its source: otherwise "pumping" wouldn't be a thing.
oh btw the source you quote (apart from the link being 404) literally says "lasers cannot have negative temperature" (because they're not in equilibrium but keep being pumped), while sources _they_ quote say they do, so even they don't seem to be sure.
they also don't explain how all of their samples don't immediately go to ±∞K as soon as they allow them to equalize temperatures with the environment. in fact, shouldn't a simple laser pointer's dot have infinite temperature because you have ~+300K in the environment and allow that to equalize with the "negative temperature" in the laser?
i think the term might simply be misleading, what you really have here is an "inverted energy distribution" or "negative statistical-entropy-per-delta-energy coefficient", is it not? maybe it shouldn't be called "temperature" if it's... not that :P hey even defining it as a function of *coldness* (thermodynamic beta = 1/kT) makes way more sense. the "temperature" bit really just feels like a desperate attempt by companies like QM to shoehorn an abstract concept such as population inversion back into a "layman's understandable word" but ignoring the facts: a) that's not what that word means in a layman's understanding, and b) it doesn't make much mathematical sense either given beta works way better for all of those calculations.
about your own pinned comment i can for some reason not reply to: the second law of thermodynamics says that entropy in an *isolated system left alone* cannot decrease. but when you're pumping electricity through LEDs that you then focus onto some target to heat, that's not that. it's neither isolated, nor being left alone, nor actually entropy decreasing (you're simply converting electrical energy in the battery/power plant/whatever into kinetic energy in the target, actually *increasing* overall entropy. btw if you look at the actual complete system like that, you'll of course find that your target can't receive more energy than your electrical power source provided, satisfying the 2nd law). pretty sure that's what the QM folk mean by "pumping doesn't count": technically you're dealing with population inversion and all that in a part of your overall system, but not in an isolated system doing that "naturally".
Finally someone who fully understands my confusion
Yeaaaa.. exactly what I was thinking
nice explaination, but i still don't understand either the video or your comment cuz of my smol brain lmao
thank you for doing that so i didnt have too.
I think you are correct in that collimation is the answer to what is happening with the laser and does not happen with flashlights or the sun.
Just change or remove the reflector or use a larger lens that's wider than the beam of the flash light. You can also use multiple lenses or lenses designed specifically for the light source. SOLVED
Thanx. I have been looking all over for an explaintion.
Your comment on the flash light intrigues me, the LED’s can be focused with a reflective mirror with greater efficiency than with your magnifying glass!
Well that's the whole point of why telescoping flashlights exist. I have one for example that basically looks like a beam when fully zoomed out (not quite a laser but still way smaller and brighter). Pull it back in and it disperses in all directions as normal.
The best you can do is to have an image as bright as the source, using ellipsoidal mirrors.
*styropyro walks in*
styropyro: _"Hey."_
I understood that reference
@@samyakjain7474 I did , too.LOL
@@samyakjain7474 But rules have been changed. Once there, a return may no longer be possible.
:PauseChamp:
And also if you applied the same method and put that laser with the magnifying mechanism in the vacuum of space the temperature that would be getting off the that device would be immense
LEDs and lasers emit light at a single frequency. (In fact, the 5W laser is an LED device.) Because both the flashlight and laser are LED based, both emit light at a single frequency. Each of the flashlight's LED bulbs are actually three individual LEDs in red, green, and blue so that when combined, the light appears white to our eyes. The only real distinction between the two devices is that the laser LED emits light that is coherent. That is, it comes out as a narrow beam. (But the beam disperses the farther it travels, and even at close range, you can see that the beam produces an oblong spot that is larger than the laser's LED.) This results in the laser's power (5W) being concentrated on a tiny area (what appears to be a few square millimeters). So, if you apply optics to the light coming from the 35W LED flashlight so that its light is focused onto a few square millimeters (similar in size to the laser spot), you would actually have MORE power per square millimeter, and would have a device that would produce higher temperatures than the 5W laser.
It's all about watts per square inch. If you have a 35W flashlight, and you have the proper optics (i.e., multiple lenses) to focus the energy onto a small point, when the energy concentration is sufficient to cause the temperature to exceed the material's combustion point, you get smoke and fire. It is not about the surface temperature of the source, it's about the energy concentration. In fact, I've done it. You just need the right optics. I've also done it with a good old-fashioned camera strobe flashing through a telephoto lens, properly focused, onto a piece of cloth. Even though the flash lasts for only 1/10,000 of a second, you can cause combustion if the optics are set properly. Frankly, I think the discussion about thermodynamics and positive/negative infinity Kelvin temperatures is completely irrelevant to whether you can cause a fire with a flashlight.
The point of the idea (in the video, but not fully explained) is when you have only one lens focusing black body radiation from an object, it's impossible to focus it and have a light density greater than the emitter itself. That can be changed if using more lenses. But for lasers, as the light is emitted already in parallel, it is possible to focus it, with only only lens, to a density greater than the surface emitting the light.
Sorry but LEDs do not emit at single frequency and coherent does not equal narrow beam.
This is the video I'm going to show to anyone who's not familiar with the concept of negative temperature. Thanks for making it so very simple!
Why to call a higher positive temperature negative? Whats the difference between positive temperature and negative temperature?
It is simple though also impossible to understand properly. I have no idea what's actually going on here because it is impossible to go below 0k because this is the point at which the system has no energy and therefore no energy can be removed so it can't be colder. Given this, the video seems to make no sense. Help?
This isn't a remotely simple explanation. There's no discussion of why having all particles in a highest state means infinite temperature or why that then wraps around to negative infinity, then negative integers. It's not a good explanation at all.
@@jamieg2427 it is simple, just unfortunately at the expense of any way to comprehend it. If you add explanation it becomes less simple, yet easier to understand. Strange, to be sure, but, i think, true.
Was it simple? I didnt understand shit!
I can normally follow what you’re saying in your videos, but this one left me very confused. I would have thought the reason you can focus the laser is just because you can get the whole beam hitting the magnifying glass all at once instead of just a small part of spread out light from the flashlight. This would then have more to do with the optics of the laser compared to the flashlight rather than temperature?
Yet it violates law of conservation of energy.
From what I understood you’re right, focusing the beam is what’s increasing the temperature at the site of “impact”, but what he’s explaining is what’s happening inside the beam itself. Whatever the beam hits, no matter how focused it is can only get so hot, but basically lasers are fukkin weird
@@Gay_Priest 31 subs , what vids do u make
@@BROCKSGAMING a random video of Skylanders Spyro rotating to the leek dance song
@@abcxyz- Not if you take into account the amount of energy used to pump photons through the lasing medium and compare the input/output difference.
1:40 if you had a very large magnifying glass or a lens with different optics you could focus all of the light down to a small point that would be brighter than the light the flashlight would be able to light up in the same surface area, as the light from the flashlight alone would be spread over a larger area.
Assuming you had a Gaussian beam with an M^2 of 1, which you don't, you could use a simple waist calculation to determine the focal width based on the lambda and the radius of curvature of your lens.
Not gonna lie.
In elementary school, I did this to my Woody doll, like in the movie.
Oh no.
w h y
Im guessing C stands for "Cid"
so it was ... brain freeze?
Easy there Sid
7:15 : SOOK....TOOK - OOK - SOOK - OK!
* Ground starts shaking *
* negative temperature demon appears *
Kelvin is a scale for super subzero temperature. For things like super conducting magnets. Another word for degrees.
I like to render patterns of light in 3D with virtual light transport, it's very beautiful, especially when you make them pass through virtual lenses. I just use free renderers, now (mostly Cycles and luxrender for blender), but I used payware ones before. Anyway, it's fascinating to me. To make it light in 3D with volumes. you can do the same IRL of course, but there isn't a lot of pictures of that, I mean, with smoke and to visualize the complex patterns in a volumetric form.
The dot can be brighter, as the energy is being focused into a smaller area. There is less total energy after focusing, but it can definetly be brighter.
and hotter... just need a magnifying glass bigger than the angle of the emitter and glass that wont absorb photons lol
So why it doesn't work with flashlight?
@@justincase1898 because flashlights and the sun have positive energy while lasers have a negative energy. Don't ask me what that means, I just know that's the answer lol
@@MuhammadAli-qh8tg Not negative energy. Only negative temperature.
The second law of thermodynamics forvids you to focus the light from the flashlight to a smaller area than the surface of emition. Doesn't matter what array of mirrors and lenses you use
The Action Lab: "And what this means is that negative temperatures are hotter than positive temperatures."
Me: steps outside in Wisconsin winter* "such warm. moar physic."
😆😂😂🤣🤣🤣🤣🤣🤣🤣🤣
@@null360 You're all hysterical with this... Meanwhile I'm trying to remove the dent in my face my palm left in it.
I'll probably have to rewind this video to understand but it was good, very good!
Sure you can, use a round sleeve or tube and put that flashlight inside it and contain it into the magnifying glass.
it is impossible to make it hotter than the fuse of the individual LEDs. (but its possible to make it hotter than the average temperature at the opening because the light has already spread a lot)
Curious to see what would happen if you tried microscope lenses for the magnifying glass.
They both are the same thing
Start nuclear reactions
@@LorenzoJamaika who is right?
To negative infinity and beyond!
Microscope lenses are terribly lossy and with a laser you would probably burn the internal optics rather quickly. Magnifying glasses are much more efficient. Better yet get a thin curved lens to minimise loss or a collimating lens followed by a magnifying glass.
Where are u late af squad
Here
Here too
Here lol
ZAC KNIGHT here
Probably here
The term "hot" is relative, not absolute.
As we get closer to any heat source it "feels" hotter but the energy output remains the same.
Great video helped me learn a few new things keep up the great work
What if I magnify a fleshlight? Does it make it tighter?
XxMsrSzprzxX yes
Grandpa always said marry a girl with small hands
Have you checked out the crazy to hot matrix?
Hahahahaha
XxMsrSzprzxX I still have blisters on my tongue
*THE SUN IS A DEADLY LASER!*
Not anymore, there's a blanket
Now the animals can go on land, come on animals, lets go on land!
We have to make a religion out of this
The sun is dead
The sun is a firin iz lazzzaarrr
I was thinking if you surrounded the sun in mirrors then made a tiny area for the sun to seap light out and reduced it to a a tiny point using a giant magnified glass then made it tinier and tiner until it's a tiny point wouldn't it be hotter?
Of course, we don't have that kind of technology, but yk just thought I'd put my theory out there 🤔 😅
Unfortunately, at some point, the light would be unable to get bundled up further. The more you bundle up the light, the higher the spread becomes, making it harder and harder to bunch up. The surface area and the spread of the light are inversely proportional. Let me show you:
Remember this: Systems with lenses and mirrors are reversible (reverse the direction and it will look the same).
Now imagine a small light bulb. The light at the light bulb has immense spread, and it pretty much shoots out in all directions. Now position this light bulb in the center of a very big parabolic mirror. The light will hit the mirror, and it will get “straightened out.” But at what cost? The cost is the increase in surface area. The light bulb had light concentrated very closely, but the spread near the bulb was very high while the mirror reflected the light into nearly parallel light rays, but now they might be many magnitudes further apart from each other.
And because this system is reversible, you can imagine yourself shining light into the mirror and trying to bundle it into a single point. If the light you put into the mirror is even just very slightly not parallel (even just a tiny spread), then the spread will get magnified by a ton after converging to the focal point. The size of this pseudo light source at the focal point is determined by the coherence/spread of the light you put into it, and it is impossible to bundle it up more than that.
You simplified weaponizing Lazers image how effective this would be when it's amplified and targeted electronics and gas lines. Just make it bigger and aim from it sky😮
Can you explain negative temperatures more, please? I'm a bit confused with negative and minus temperatures.
-50°C is still positive, because it is still ~223 K above absolute zero. Negative temperature is not cold, it is in fact hotter than the system temperature. In negative temperatures, the heat flows backward, from the negative temperature to the positive one. This idea seems to be a bit unintuitive because you think of temperature as hotness. In quantum physics, temperature is viewed in terms of the entropy of the flow of energy. Entropy flows from the source of heat outward and loses energy. In negative temperatures, energy flows from the system back to the source of heat, adding energy to the quantum state. Edit>> That's my basic armchair understanding of it. I'm a chemist, not a quantum physicist, so my description could be wrong. Someone please correct me if it is.
This guy bellow is pretty fast at typing
@@deluxeassortment When the original poster was asking about negative temperature, they meant negative KELVIN temperature. That's the entire subject of the video, so I'm surprised you misunderstood the question.
@@jamieg2427 i think they know that
Nothing can exist at 0K, and existing at energies below that is out of question.
The simplest explanation as to why is doesn't break thermodynamics is that thermodynamics has to do with the energy of a system. The system is not your target, it's your target + your environment, i.e. your garage. Lenses don't change the amount of energy the system receives, only the energy the target receives. There's 0 need to bring negative temperatures in this as they're totally irrelevant here.
Also, heat is not the only measure of energy in the system. And creatinf a single point with a higher temerpature than the average temperature of a large surface does not imply that point has more energy than the source.
I have no comment on the negative temp, infinite temp... and negative 0 temp claims, but if they make as much sense as the second law violation claim.... they are bunk
You're looking at the wrong law. Focusing light to a point hotter than the source wouldn't break the conservation of energy, aka the zeroth law of thermodynamics. It would break the second law which states that a closed system will tend toward max entropy. Statistically all the energy will spread out evenly, eventually leading to one uniform, lukewarm temperature.
If you could make energy flow from a colder place to a hotter place by simply holding up a magnifying glass, you could decrease entropy indefinitely. That would break the second law.
@@shadrach9654 Negative temperatures are a real phenomenon, or at least it's a term that physicists use for a real phenomenon. Maybe the label doesn't make sense to how you and me understand temperature, but maybe that's ok because it apparently can't be described by classical mechanics to begin with. It is only described by quantum mechanics, and god knows our intuitions are entirely useless when it comes to qm.
@@volbla my father with a phd in materials science and engineering disagrees with you, and the video, on very nearly every scientific claim made.
Your referencing valid laws of nature, but your apllication of them is wrong, they just dont mean what you think they mean.
Seems like this video is some sort of comment bait for the algorythm.
@@volbla that is true, and doesnt refelct the claim made in the video, which is thay if a point can be hotter than the source....
Amazing young man. I have my grand children watching him.
Light is actually a visible heat and when you focus the light on one point using the magnifying glass 🔎 heat is focused on one point thus become powerful and so it burns some objects 🔥
The temperature scale needs major revision, its a carry over from ones devised centuries ago when all we needed was to determine relative termperatures commonly found on earth that we deal with day to day, not the extremes. Infinite temperatures, -0, -infinity temperatures are a terrible horrible no good _linear_ scale that are just mathematical placeholders for a much better scale that has yet to be introduced.
7:53 which is actually pretty cool
Pun intended? 🤔
@ThatOneNoob504 negative temperature should be pretty cool, indeed
"Does that (law of thermodynamics) apply to lasers as well?"
I'm gonna go out on a limb here and say yes.
Nope. 🤣
There's an exception for every law. It depends on the bribery involved💰.
Another set of factors not discussed are the light defuser in the flashlight scattering light that is already incoherent light, whereas laser beams are coherent light. Coherent light is implicitly more affected by quantum mechanics; photons being pumped between orbits of electrons and atomic nuclei and being combed straight via electromagnetic influence on both the photons’s wave and particle traits no doubt interact with subatomic particles and whatever waveforms or lack thereof that define the behavior of quarks. But then I am only a former English major who got an A+ on a term paper I did on lasers 42 years ago. No bonafides as a physicist.
I had a hard time understanding this, but it sounded really cool anyway!
I love this video! I’m also fond of Inspector Gadget and Buzz Lightyear.
That... didn't explain this to acceptable satisfaction.
I agree
Yess, I am kinda like more confused after watching this than i was before
Its very hard to do, en.wikipedia.org/wiki/Etendue if you understand the mathematics go right ahead.
to me is simple BS
@ADITYADIVINE It's just the scale we use, and it's statistically based. i.e. There's isn't actually a "temperature" value that every atom has. The 2nd law of TD just uses that already weird value we use in temperature to come up with it's laws. Those laws are emergent properties, not actual "things" in the world. I think that's where you're going wrong with thinking about infinite temperature, temperature is emergent, not fundamental. In fact, all physics laws are emergent. Even those that physicists hold as fundamental.
temperature going from a high positive value to a high negative value suddenly makes me think of integer overflow in computer science. Obviously not related at all, but it's funny to imagine that you're just overflowing the variable used to hold the temperature for that object.
Nuclear Ghandi sort of thing?
Simulation theory proven????!??!??
No.
@@ghqebvful yes exactly, integer overflow was what caused Nuclear Gandhi. In real life, it also has caused rockets to explode I think, as well as missiles to accidentally hit civilian targets.
Yaaas
R2Bl3nd makes sense if we are living in a simulation.
Like a venturi for light, concentrating it, is why it gets hotter, like sticking your thumb over a hose and gaining more water pressure... energy behaves the same through every form I've come to realize... nice work
Try getting a concave lens and put it on the point of death to make an insanely thin laser that stays like that forever.
Everybody gangsta till he uses negative kelvin
Negative kelvin is impossible
@@Tylorean it could be, but that would mean that everything would move backwards if it was in the negative kelvin scale
@@FirestarDoppelgangerhmm yes moving on a negative distance
@@FreeGroup22 You can move in a negative distance, that's just related to your point if reference.
@@welcometoreality437 nope, moving backwards does not mean that you're moving a negative distance, the only thing you can say is that you changed your position to negative coordinates
6:41 *OK.........SOOK.........took*
I tried not to read it like that 😂
what did sook took
This is mindbending. I ❤ it.
Use a Reflective Inner Tubing.. then connect the Two.
The laser is a point source which is collimated. This keeps it narrow for an “infinitely” long period. The laser you are using already had a mirror that is giving it a desired beam width. All you are doing is focusing it smaller so more energy is hit that spot. You aren’t creating more energy or heat, but collimating the available energy to a smaller surface area. Reverse inverse square law. Negative temperature has nothing to do with this experiment, you are using higher levels physics incorrectly.
Plus the reason you cannot achieve the same temperature as the sun with one source glass as you did is because again of the inverse square law which states the energy over twice the distance from its source is spread over 4 times the area, so you get 1/4th the intensity. By the time it hits earth the energy intensity is super small.
You LED light could do more damage if you were able to collimate it using a multi mirror set up to do so. Then from there bring it down to a point source.
Just using one magnifying glass doesn’t prove or disprove the statements you made.
I was just about to make the same comment.
This isn't higher level physics
When yo mama threatens you to get a good edumaction 😂😂😂
True. The source and the focused point are both the same heat energy. Its just more concentrated ill say.
Man nice I am in love with physics....
Tiny correction: You actually can't have a temperature of infinite Kelvin because when you add energy into matter (-> in this case heating it up) it's Wavelength becomes smaller and smaller until it eventually reaches the Planck length (the smallest length possible in the universe as for our current understanding) at this point you could add more energy into the system but it would become hotter than absolut hot, also known as "Planck Temperature". We would no longer consider it as temperature because our current models don't apply there.
I take it this is what would happen if you managed to get more atoms into the higher state in a non-quantum system? Planck temperature? Or would the atoms just disintegrate as there’s too much energy for it to hold together?
@@Gay_Priest If I got this right. Matter above this temperature is no longer Matter. So there would be probably no atoms (but they would have already fallen apart before this point is reached)
@@zeg2651 I think if you could somehow get matter to that level you’d be right, but matter and energy are related according to Einstein and there’s a maximum frequency things can vibrate with heat energy at before the wavelength reaches the Planck distance, the smallest distance possible. At that point I believe any matter, no matter what it is would just start disintegrating rather than get any hotter, kind of like boiling the hell out of water will never get it above boiling, it’ll just boil faster.
Then again I’m not a physicist and I could be completely wrong. All I know is that light is both a wave and a particle at the same time, and normal physics doesn’t apply to it
I think if you put too much energy at a single point it would start produce matter from the vacuum. There was even an idea to do that type of experiment with a very powerful lasers.... but then it was scrapped, because "it's too expensive".... it seems for our politicians, understanding the fundamental building blocks of the universe is not very important.
@@Slav4o911 Too expensive? More like they can't risk the public getting any solid information on the results.
That would be catastrophic for them.
Action lab: (starts berning something with a laser)
Me: alright so how can we make this into a weapon.
Make the lens the same way we make reentry capsules for space travel. Shallow convex curve on the bottom and and a tapering cone on the other. It should channel the light to an even smaller point.