11 Subatomic Stories: The Heisenberg uncertainty principle
ฝัง
- เผยแพร่เมื่อ 16 มิ.ย. 2020
- The Heisenberg Uncertainty principle is one of the counterintuitive ideas that arises from early twentieth century quantum mechanics. In episode eleven of Subatomic Stories, Fermilab’s Dr. Don Lincoln explains what the principle is, how many people get it wrong, and how to understand it properly.
What is quantum mechanics really all about?
• What is quantum mechan...
Can leptogenesis explain why there is something instead of nothing?
• Can leptogenesis expla...
Neutrino Oscillation Calculator (Provided by Wolfram Alpha)
demonstrations.wolfram.com/Ne...
Fermilab physics 101:
www.fnal.gov/pub/science/part...
Fermilab home page:
fnal.gov
CMB image credit: European Space Agency, Planck Collaboration
Neutron star image credit: NASA
Flashlight vector graphic by Vecteezy - วิทยาศาสตร์และเทคโนโลยี
![[Full Episode] MasterChef Junior Thailand มาสเตอร์เชฟ จูเนียร์ ประเทศไทย Season 3 Episode 1](http://i.ytimg.com/vi/Qs5zdBqLn_8/mqdefault.jpg)
![[TH] 2024 PMSL SEA GF D3 | Summer | มาร่วมเป็นพยาน กับวินาทีแชมป์!](http://i.ytimg.com/vi/JCYvEsFlwx8/mqdefault.jpg)
This may continue as far as im concerned. This is a great series!
That’s amazing how generous people are these days!
it pieces everything together
Agree 100% with no uncertainty :)
Ive been following fermilabs for a few years now, but this series is just so chill. Im always learning, but in this format it feels great!!!!
Please specify. Thanks.
Ana M. Abreu. 08/21/20.
2:30
That's what I learned in high school as well. Finally in digital signal processing course at the university I learned how waves work and immediately knew that's the real thing behind Heisenberg's theory.
I got taught a lot of outdated and/or incomplete information regarding physics in school.
Wave mechanics is just one representation of quantum mechanics. I think the reason is even deeper. I think the true essence of quantum mechanics is the non commutative algebra of observables.
It’s a thing but it’s not the thing. The thing is non-commuting operators
Best Heisenberg Uncertainty Principle Explanation I have heard so far! Thank you! I love the series!
Thank you! I learned about the Fourier Transform 20 years ago in college but never imagined that it would relate to the Heisenberg Uncertainty Principal. I love it when something you learn connects to something else, even years later! Thank you good sir!
Thank you Dr. Lincoln, I could watch and rewatch this series forever. It’s one of the best about physics.
Edit: Corrected mixup names. Sorry.
Fadi Fortuna hahaha! Corrected. One of my physics teacher was a *Don Franklin* and I always mixup names.
I have to say that was one of the best explanations of the real meaning behind the uncertainty principle I have ever heard. Thank you Dr. Lincoln. I really appreciate you taking the time to sit down and chat about these various topics. They have all been good, but this was the most enlightening for me personally.
This was a great episode, I was likewise told an incorrect interpretation of the uncertainty principle. I think Sub atomic stories is your best series yet.
This video is the best explanation of the Uncertainty Principle I've ever seen. It really should be interpreted in the context of Fourier Transformation.
Please keep making these videos. They help me connect the different parts of physics together and just makes it even more interesting! Good work! :D
Yes, I love these chats. I have learned a lot about things I read about 45 years ago. Keep it coming. Thanks and stay safe.
Thank you so much for explaining this. Having taken calculus courses, this makes sense. This also demystifies the point so that it is a clearly understood principle with discreet variables rather than the mystical paradox it is often presented as.
Funny thing is, if you dig deeper into quantum mechanics its not founded on discrete variables and becomes mystical (from our classical view) again.
I'm just not sure about the Heisenberg Uncertainty Principle but I am certain your explanation is easy to understand and makes sense.
This was a particularly charming episode of subatomic stories. ❤️
What an intelligent and informative series this is. It is presented by an exceptional teacher! Thank you...
OML this is such a great explanation! I always saw Heisenberg uncertainty explained as a measurement problem. The wave freq vs localization makes so much more sense! Thanks!
The neutron star question litteraly BLEW MY MIND😦😱🤯
This is a quality episode. Keep up this extra level of explanation.
Thank you, Dr Lincoln! Like you, my earlier education experience provided “a less than helpful “ explanation of the Heisenberg Uncertainty. And I have still struggled with the details all of these years, especially if trying to describe it to someone else. NOW I feel that I have finally GOT it (at least more) cemented in my head! Thanks to you for taking the effort to help clear this difficult subject 😊 for All of us; great video.
This is the best explanation of HUP I've seen, thank you Dr Lincoln
The best explanation i’v ever seen, easy to understand, thank you sir.
Enlightening!!! Great explanation!!! Amazing series... pls continue posting amazing videos... I have seldom come across such reliable and interesting source of correct explanation for such complex topics.
these videos are actually amazing for deeper knowledge for a level physics highly recommend!
Keep up the great work Don. I love your series.
Great content as always. Thank you so much Fermilab.
Great timing, I was having trouble finding a good explanation of this!
Yes Don - I’m really enjoying the series - Many Thanks
I am certain that I would like to see a massive number of your videos coming forever, you have enough energy to do that !
... The ghost of Heisenberg
It's beyond me how people try to teach this without pointing to the Fourier Transform. I'm glad to see that you did it.
That said, you should have also spoken about information and which domain it's present in a bit more.
Bosons are in the space domain (stretched out) and does not change in time (specific).
Fermions are a little bit in both unless they are at absolute zero and all of their information would be in the time domain (stretched out) and not in space (specific).
Something more,
The uncertainty in energy does point to mass, but it also points to what kind of energy it is.
Please, dont stop doing this videos, are just great.
Lovely explanation, thank you. Please do continue this series.
sir i have recently started following you like from the time of lockdown in my country.
i love physics. I am blown to gain such massive amounts of knowledge that you provide , I admire you so much thanks for giving me a role model.
now i wish to pursue a career in physics.
Do it. You'll never regret it.
Awesome series!! Thanks a lot for doing this and making physics understandable and approachable by anyone!! I used to live near Fermi lab and always wanted to visit. I hope I can one day! Brilliant!
I watch your videos whenever I get the chance and all I can say is --Thanks! I guess I was lucky and got a decent understanding of the Heisenberg Uncertainty principle from my Prof's but I have to admit yours offered a nice, short, and concise conceptualization.
On the pronunciation of ν and other Greek letters. "Nee" is the modern Greek pronunciation, whereas "noo" is a very ancient Greek pronunciation. There are numerous changes in pronunciation that have happened in the history of the Greek language(s), and one of the most notable is called "iotacism", which is really a whole bunch of different changes, but refers to the fact that many different vowels and diphthongs in Ancient Greek have somehow all become "ee" in Modern Greek.
Since the most famous works of Greek literature and philosophy, including early work in math and physics, come from over 2000 years ago, it is Ancient Greek that learned Europeans studied in the middle ages and Renaissance, and it is this tradition that led scientists and mathematicians to think of Greek letters as convenient symbols. Thus, common parlance about how to pronounce Greek letters also comes from this tradition of studying Ancient Greek.
However, it is not so simple as saying that Ancient Greek pronunciations are used in math and physics. The issue is that people in this long European tradition of studying Ancient Greek mostly didn't really know, or even care very much, how Ancient Greek was ACTUALLY pronounced. (To some extent the reconstruction of actual ancient pronunciations is really more of a modern phenomenon that got going with the development of modern historical linguistics in the 19th century; however, there were attempts to do such long before that.) Thus, there are actually numerous traditional pronunciations of Greek that developed in different European countries where people spoke different languages.
These are often influenced by the native languages of the different countries; in particular, (1): Greek words could essentially become like native words of the language of an academic community familiar with them, and their pronunciations would then change according to the same phonetic rules that changed the native language of that community over the centuries, and (2): When Greek words are spelled out "phonetically" in non-Greek writing systems, people tend to read those spellings as if they were native words of their own native language, even if those "phonetic" transcriptions are designed to be read in a certain non-obvious way or were designed for an older version of their native language that had different correspondences between letters and sounds.
For instance, I tend to pronounce μ and ν as "myoo" and "nyoo", which arguably makes sense for 3 reasons: (1) These are the ways I first heard these letters pronounced, (2) These are reasonable readings of the traditional "phonetic" spellings "mu" and "nu", according to modern English spelling-sound correspondences, and (3) The very ancient Greek "oo" sound (υ) became fronted to sound more like the French "u" or German "ü" in most situations even before Alexander the Great in Attic (Athenian) and Ionic Greek. While this sound eventually came to sound like "ee" in Modern Greek (after staying around through much of the Middle Ages), that is not what happened in French. In French, an old Latin "oo" sound (French is descended from Latin) became a fronted, much like what happen in Ancient Greek. When the English language became flooded by French loan words after the Norman conquest, and after various vowel changes in the English language between then and now, these "u"s from French are now generally pronounced as "yoo" (which is the reason why "u" is often pronounced "yoo" in English and "myoo" and "nyoo" are reasonable English pronunciations of the spellings "mu" and "nu"). It also seems quite natural that the French would match up the Greek "υ" sound with their own basically identical fronted "u" sound, and with this traditional correspondence of this fronted "u" sound to an English "yoo", it only seems reasonable that the same thing might happen in English to the Greek "υ"-sound, especially if they were often introduced to it by the French. It's actually quite likely this is not true, because the Romans invented the letter "y" to transcribe the fronted Greek "υ" sound, and this is pronounced "ee" in the French words derived from Greek, at least when they come from Greek words that were borrowed into Latin; however, there were multiple attempts in the Renaissance to reform pronunciation of Ancient Greek to more authentically match ancient pronunciation, and my "myoo" and "nyoo" pronunciations might somehow be descended from such an attempt, similar to how the reformed pronunciation proposed by the Dutch scholar Erasmus's 1486 reconstruction of Ancient Greek pronunciation (which was adapted and popularized in England by Cheke and Smith in 1540) started a tradition of pronouncing Greek in English speaking countries that was then greatly distorted by vowel changes that happened in the last 500 years, such as the tail end of the "Great Vowel Shift". (Although I said there were multiple attempts to reform the pronunciation, I think most of them were based on Erasmus's reconstruction. It should be noted that I actually just looked Wikipedia because I realized that I was starting to write about things I didn't really know.)
These traditional pronunciations also may have influences from the Latin pronunciations of Greek words (since the Romans incorporated lots of Greek words first, and then Latin became the language of learning in Europe for centuries), as well as from various later versions of Greek, such as Byzantine Greek and Modern Greek. (Keep in mind it's a continuum, languages change slowly over time; they don't just suddenly morph into different languages.) This influence from later versions of Greek no doubt comes from things like the person who corrected his pronunciation from "noo" to "nee", i.e., it comes from the idea that whatever they say in Greece now must be the actual "correct" pronunciation (with some maybe even thinking it's the original pronunciation, due to not considering language change). The idea of "correctness" is fundamentally pretty arbitrary, so it's hard for me to say that it's wrong to think that, but it is a bit misguided to assume that everyone should just change their pronunciation to match the Modern Greek pronunciations without justifying why this is better.
An example of influence from later versions of Greek, and also somewhat from Latin, is the pronunciations of the Greek letters φ="phi", θ="theta", and χ="chi" with the English "f", "th", and "k", sounds. The romanizations "ph", "th", and "ch", were invented by the Romans to transliterate Greek. In Pre-Roman Greek (and probably also in Early the Roman Period), these letters were pronounced like "p", "t", and "k" (followed by a puff of air, like how we pronounce them at the beginning of words in English); however, between the Roman and Medieval periods, the pronunciation of these sounds softened to sound like "f", "th", and a raspy sound similar to the Spanish "j" or the German "ch". These new pronunciations were prevalent in Greece throughout the entire history of the English language, and the fact that we write our "th" sound the way do is probably by analogy to Medieval Greek (since "th" was the normal romanization of θ, which was pronounced this way). Back in Middle Ages, when English had that raspy sound like German and Spanish do, it was often spelled "ch", as it still is in German, by a similar analogy with Medieval Greek, (although the spelling "gh" is what we generally see in Modern English spellings of words that used to have this sound, like "though", and "night"). The medieval and Modern Greek pronunciations of these sounds (which are "unvoiced fricatives", by the way) have almost always been the preferred pronunciations of these sounds in medieval, Renaissance, and modern times alike, no doubt because that has been the pronunciation in Greece throughout all of these time periods, despite that the fact that these are not the pronunciations that Homer, Plato, Aristotle, Euclid, or most of the other famous Ancient Greeks would have used.
This also shows influence from native language phonology. English has the Modern Greek φ аnd θ sounds, but no longer has the χ sound; French has only the φ sound; and German has the φ and χ sounds, but not the θ sound. As it happens, all these languages use the Ancient-Greek-like ("p"), "t", "k" values when they don't have the Modern-Greek-like sounds (or rather, people who aren't studying Greek seriously use these sounds for the stray Greek words and letters that come up), though I think Germans often match French and use "k" for the χ-sound, even though they theoretically know how to say a sound like the Modern Greek sound. (This probably mostly has to do with the fact that the German "ch" sound usually only occurs in certain parts of words, at least in "standard" dialects.)
Finished your course on the great courses. Excellent. You are a great teacher!
Cool....didn't know about the time/energy application of Heisenberg's Uncertainty Principle...I LOVE learning new (to me) aspects of scientific principles (and getting more accurate explanations)....Thank you!
Very well explained, better than my former college professors. You have a gift for teaching.
Although I would add that the "wrong" observational explanation you provide is also true, however it would be true in principle also for classical systems, while -as you explained- the Heisenberg uncertainty is rather an intrinsic feature of matter.
I love this series. A bit over my head, but every time I watch an episode I feel a little smarter for the bits I DO understand.
Wow, what a great video and series! Much thanks :)
I love these videos! Thanks for sharing. 👍
Another good one Doc ! Funny, I'm enjoying physics more now in my 70's then I did in university (slide rule generation). Take care.
That's awesome explanation for this principal
Nicely stated, Dr. Don. Very nice. Glad to see that the zombie cat wasn't even mentioned!
Dr. Lincoln great episode+ Thank you so much :)
Wow are you good at explaining things. I love your videos. Thanks from an old (OLD) guy and retired engineer!
Wow - this makes the comments a few weeks ago about the mass of the W and Z bosons make SO much more sense! Thank you!
What does it really mean to add the wavefunctions ? Are we combining the electrons?
Dr. Don Lincoln,can we substitute position and momentum at the same time in Max Born`s equation?
I love it when Don uploads
That's what she said.
I studied engineering in college decades ago, which made a video I watched on TH-cam several years ago make the Uncertainty Principle click. It said the same thing you did, that the momentum and matter (i.e. position) waves are Fourier duals.
Dr. Don, You're a national treasure!
I love the Questions ! Its super entertaining. Please keep it up?
I would really apreciate it if you would make an entire Video about the CMB. I am curious to learn more about it.
Another great video! Thanks for sharing!
I understood some of this so I have a bit of a better understanding which is cool. I still have a long way to go. Thanks for getting me just a little bit further :)
Wow, this video tied together quite a few facts about quantum physics and the universe that I've heard before in independent contexts.
This is a great series. Thank you for the lectures Don. Defund science outreach never!
Dr. Lincoln, I LOVE looking at the books on your book shelf. I suggest Martin van Crevelds "supplying war" for a different way to look at warfare.
You and Matt are the best - thanks much
Bumper sticker seen on a physics prof's door: "Heisenberg may have slept here!"
There's a 3Blue1Brown (math-animation&explanation) video about the uncertainty principle, and where it shows up both inside and outside of physics: "The more general uncertainty priniciple, beyond quantum"
I love watching all these, but I'm an old man and I'd be lying if I said I understand all this stuff, but I think I kinda get some of it , so keep em coming please.....
I've run out of Fermi lab videos to binge watch during quarantine. Pls help
There are more science channels to the rescue:
Sci Show / Microcosmos (general popular science)
Kurzgesagt (scientific stuff with a moral)
Launchpad Astronomy (accurate science facts on astronomy)
PBS Spacetime (specialized science, math free)
Isaac Arthur (science and speculation on the future of humanity)
Many of Brady Haran's videos with the University of Nottingham
Royal Institution (recorded public lectures)
Anton Petrov (astrophysics papers summarized)
i love the series, but i can only watch one at a time because they have so much that blows my ,mind i need a good long period to think about it before i dare watch another!!
this series is great
Excellent video!
Excellent. Thank you.
--------------------
For me personally modern physics & its vastly developed fields are important for curbing aside all forms of anthropic misconcepts of the post Aristotle periods.
And Heisenberg's Uncertainty, although at Quantum levels, but it also reminds us of indeterminism in evolutionary history, which many branches of different human hybrids have falsely treated with certainty/ deterministically.
cheers Dr. Don!!
For all who say ni
Buy them a shrubbery
I was sooooooo hoping that someone would say that.
Indeed.
Down chew poot very yubbles inta they aquasian?
Then it wouldn't be constant, would it?
Who the hell are you? We're the knights that say "nu".
embustero71 -sorry, crunchy frog excursion
Wow
Great work
Keep it up Sir
brilliant explanation
I enjoy the series, I understand very little of it, but I like it.
Way above my understanding.
hey D.lincoln i want to ask u about the Axion particle and if it is maybe the answer for the missing antimatter in the universe
At university (before the top quark had been discovered) I came up with the idea of gravity being the cause of all forces, which in turn gives rise to particles.
The idea is that space is moving (in 3 dimensions) and that movement causes areas of space to be both expanding AND collapsing.
Collapsing space accelerates towards the speed of light which results in tiny areas (points) of the field of moving space appearing "permanent".
That is, a particle is not an actual "thing" but an area of very fast moving space.
Given the explanation you used to describe the adding of wave functions, I would suggest to have included reference to Feynman's Path Integral.
I am frankly concerned and curious as to why this particular channel doesn't have a higher subscription rate. Its FermiLab folk!! Not some goober with a grasp of physics but no clout( yes that sort of thing counts in believability and school choices).
I've heard of this guy before I came across the channel.
Now I'm not saying the other lads aren't on the ball or inaccurate, hell some of their info was probably from FermiLab. I'm just saying history, pedigree, veracity means a lot. It's just human nature I suppose.
Anyway I read about1 Enrico Fermi in the 4th grade for kicks instead of sports. As a result I had a career, family, a measure of success somewhat larger then Max Planck's rather intriguing constant though I prefer the unredacted version just to terrorize students and new teachers.
I expect a more rarefied appeal from Utbes proudly jaded Higher Branch MatheAddicts.
Please excuse my waaaaay too stylized writing. I've not had coffee yet.
Hi Mr. Lincoln. -douglas
My thinking uncertainly exact! It doesn't get better than Fermilab and having someone that can reveal things without excessive "dumbing down" is great at the same time not throwing a blizzard of integrals that glaze my eyes over.
That's awesome you use Wolfram Alpha
Hi Mr Don.
what sizes do elementary particles have?
For example, the electron is considered as point like particle, but, if it is pointlike, then it should be a black hole, which in turn should evaporate quickly.
So, electron is considered pointlike because we cannot measure size, or, it really does not have any length?
As the wave goes along from crest to trough, is there enough energy built up at crest / trough to create a particle, which in turn reduces the energy until the wave again builds up the energy and repeats the process?
Thank you Sir at last after long time now understand what is Heisenberg uncertainty principle. I need a clarification, can Heisenberg uncertainty principle address teleportation from quantum level to molecular level, like predicting velocity of an moving object and relative velocity required by the mass to travel along with predicting the position of objects moving in a path
Wow, this video did me better than the entire course of physics in my college.
can you explain the uncertainty principle for the time and energy relation in terms of the wavefunction as well?
THANK YOU... PROFESSOR LINCOLN...!!!
Probably answered in a previous video, but...
What happens as particles cool down near absolute zero? Don't their position and momentum both become more restricted and well known? (i.e. both become less uncertain at the same time?)
Their momentum becomes more certain, and their position less certain.
At absolute zero, there are so-called zero oscillations. They are exactly the size (energy) defined by the heissenberg uncertainty principle. For example, if you have an atom in a lattice (eg. crystal of ice), then each of those atom vibrates with the energy of hf/2 (planck's constant times frequency over two), which is the h/2 uncertainty defined by heissenberg. Then, even at zero kelvin, the atom oscillates (in 3D it would be 3hf/2, for three dimensions) around the equilibrium with an unknown direction of the oscillation (front-back, up-down, left-right or its combinations).
Edit: the correct term is zero-point oscillation in English, sorry for that.
What is the corresponding equation for angular momentum? Delta L Delta theta < hbar/2? Are there other equations for other conserved quantities like electric charge and quantum info?
For total angular momentum there is a similar inequality when looking at angular momentum in perpendicular planes. en.wikipedia.org/wiki/Uncertainty_principle#Examples
For charge and quantum information there is no such uncertainty inequality, since they are not operators in quantum mechanics. Their conservation is explained in different terms.
Look up "commutator relations". Any two non-commuting observables have an uncertainty relation.
Can you please make a video on invisible quark, because I can't find a good explanation of it on the internet.
Well I'm a little clearer. I get the FFTs, used those in the past. So there's a trade off between positional and energy information. Certainly the analogy of hitting the particle with a photon is wrong but I suppose it's a place to start. Not one that my A-Level Chemistry teacher used, but I remember the first test we had in A-Level Chemistry and there was a very high uncertainty factor indeed. It was a brutal shock that made us realise just how much harder A-Level was than O-Level/GCSE (UK school examinations).
Hey Dr. Don. In your response to the last question in this video you said that the CMB is due to the annihilation of matter with antimatter in the early universe. Some sources say that the CMB is caused by the (re!)combination of electrons with protons to form neutral hydrogen when the universe was about 300K years old. Do these 2 mechanisms (matter/anti-matter annihilation and electron/proton recombination) both contribute to the CMB? If so, are there two distince CMB signatures that reflect the different initial energies and origination times? Thanks as always for a very interesting series!
Does this also relate to entangled particles? Do they share common wave function in some way?
check out the pbs spacetime video on collapsing the wave function
I've always understood it as since having a wavelength and thus motion, there's necessarily a tradeoff between knowing how fast they're moving during a period of time, or where there were at a specific instance in time.
I sort of think of knowing the location exactly like looking at a picture of the particle. Yes, you can clearly see where it is when it's not moving.
Maybe this is a flawed intuition, in which case anyone should feel free to let me know what i got confused here. :)
Thank you for the video Dr. Lincoln and thd team!
Begin to read the basic math I forgot for all the years I do not use it. Then it will be Feinman's lections next. All this because of your videos.
I wrote the question onece but it was long and vague. My bad.
So here is new question: What is energy?
P.S. Yes birds are curious about physics too. We need to fly somehow.
For a particle physicist the answer is very simple: energy is a wave's frequency in time, while momentum is a wave's frequency in space. This is also compatible with relativity, where you'll find energy in 4-momentum vector as "momentum in time axis", as opposed to more familiar momentum in space axes. And it's also seen in Noether's theorem connecting symmetries with conserved quantities: momentum conservation comes from space shift symmetry, while energy conservation comes from time shift symmetry.
@@thedeemon Thank you!
@@thedeemon But then another question raise: what is wave's amplitude (in soace and time)?
@@owlthemolfar4690 In QM wavefunction has a complex number as its value at every point in space. Amplitude (length) of this complex number is related to probability of finding the particle there, while its phase (angle) is related to its dynamics, how it evolves. There's hardly any more physical meaning to it rather than just an abstract number.
@@thedeemon Thank you for the second time!
I'm not sure it's been said, but I've always thought a good way to explain it to people who don't get it is to imagine taking a picture of a bright yellow/green tennis ball, thrown in no specific direction in a clear blue sky. The more crisp the picture, the less information you have on the direction/momentum of travel. However, if you get the blurr effect of movement, you get a more accurate indication of those measurements, but less information on its exact location.
I'm not sure how accurate that is? But it always made sense in my head, at least.
Dr Lincoln thank you for your fascinating video series. I have been puzzled since high school at the extremely uniform masses of the electron and proton. You have made the mass uniformity of the electron perfectly clear. However I have learned from your videos that the internal mechanisms of the proton are very complex. Is the proton mass as equally uniform from proton to proton as the electron?
Yes.
We now know what the Heisenberg uncertainty principle says. Thanks!
Next can you give us an overview of the evidence for it? Thanks in advance.
What is a mechanism of stretching the wavelength of the photon due to space expansion?
sir can you explain tachyons? how do they go back in time?
also if it is so do they go before the time even started?
Dr. Lincoln, can you do an episode on spin? I've heard a bunch of explanations but never managed to really understand it and I'm probably not the only one 🙂
is the "t" in the "deltaEdeltat>=h/2" considering relativity? By that i mean does it equals 0 or infinity for a non-virtual photon, like one from a lightbulb?
Thanks Don