This might be one of my all-time favorite Scishow episodes. Really underscores just how insanely precise and careful much of science is. Makes our own anecdotal experiences seem as flimsy as they really are.
I agree - this was brilliant! I'll watch again a couple of times and then return to it again to grasp the delicious respect for detail. And it's really far away from my own field!
Excellent episode. Also makes the point that a lot of science is about trying to disprove science... then failing to a high degree of certainty. There aren't absolute truths, but reducing uncertainty far far below probability of 1% well exceeds our flimsy confirmation biases.
I agree, but I wish he had included a caveat about how inaccurate we can be. That same Standard Model he's talking about made a prediction that differs from the experimental result by 120 orders of magnitude. That is... very wrong
The strontium clock is so accurate that you can measure how much it speeds up when you raise it out of earth's gravity well a fraction of a meter. That makes it the world's most expensive altimeter.
Could this detect mass concentrations under the soil? Could a Strontium Clock give a better view, than Ground Penetrating Radar on ancient buildings? Also, the Apollo missions detected mass concentrations while orbiting the moon, was this the method they used?
DAD: "Son, I said meet me here in 300 million years... NOT 300 million years and 1 second!" SON: "Sorry Dad, but my Strontium watch is getting repaired so had to use my old Cesium clock."
I really loved all the analogies in this video, which gave these incomprehensible numbers some more context. The best part was the "elephant on the moon" analogy at the end, neatly wrapping everything up in a bow.
I'm pretty sure more than a few scientists do make absurdly precise measurements just to one-up each other. Academics can be petty too... really petty. People like to think of scientists as brain robots, but you get the same spread of personalities that you would in any industry.
that was the biggest suprise for me when i first got into the university. i thought everyone will be a stereotypical scientist yet it is a very good representive mix of society(as much as a male dominated field can)
Actually no you don't have the same spread by a hell of a long way. For a start the number of people with Asperger's in the general populace is about 0.3% with a further 1.3 having Autism (and no they are not the same condition). However the papers here are going with the idiocy in DSM-5 in combining the two despite the fact it is only used in the USA and has been rejected by other governmental health authorities in favour of the ICD-10. blogs.scientificamerican.com/budding-scientist/students-with-autism-gravitate-toward-stem-majors/
And yet, we humans are too stupid to invent *organic plastic* that composts to soil. Instead we let a greed driven economic system run amoc and burn up the planet and cover the oceans with a decomposable nightmare. Scientists should really stop celebrating themselves. Most of you are working for psychopaths, either being to scared or to corrupt to say NO.
@@bobrolander4344 and what have you designed to save the world? You ask a lot of the creature you call human. We build upon discovery. We learn how to do something and share the knowledge. Scientist created plastic as something that doesn't need replacement like a paper plates. Plastic bowls that don't rust and the price makes it affordable to the point where people just throw the containers away. When margarine came on the market in plastic bowls my mom saved them and when the glass bowls were getting broken by us young ones those margarine bowels became bowels we ate our morning cereal in until I left my parents house. People need to put the trash in its proper place rather than just dumping their waste into the streams, rivers and oceans. Thrid world countries are the biggest polluters of waterways.
I make my boyfriend watch Scishow with me. He has a PhD in Physics with a focus on high energy particles. He sits with me, nods his head, and chuffs in approval. I meanwhile try to understand what the hell is going on. Thanks SciShow for bringing us closer together 😅
Next week, he will ask you to watch some drama movie together. You cried because you are so touched by the story, meanwhile you bf fell asleep beside you.
I married my (now ex) husband because he's WAY smarter than I am, but,... One day, he took me up to A Mountain so we could watch the seasonal monsoon flood the arroyos. Lighting struck and he mentioned how far away it was. I corrected him saying, "Actually, it's 5-7 seconds per mile, (not one) depending on atmosphere." I hear him mumbling to himself, "... Speed of light,... mumble, mumble,... speed of sound, mumble, mumble, mumble,..." Then he goes," Oh yeah, you're right." That was SUCH a turn on!
@@RobertSzasz indeed! It occurred to me after a while, when I remembered having seen this great video from Applied Science about this very problem: th-cam.com/video/vvzWaVvB908/w-d-xo.html
For GPS, only the satellites need to be accurate. What your phone does is compare the time being broadcast by multiple satellites. If your phone knows where each satellite is supposed to be and what time it's saying it has, you can triangulate your position.
They way they said it was misleading, but what they meant was, your phone's GPS clock time is set using GPS signals. It's a bit complicated, but by receiving 5 signals with a timestamp and exact known location (orbits for GPS satellites are REALLY well known, and are pre-loaded into your GPS), using relativity, you can deduce the current time and position. GPS uses more than 5 for error correction, but the idea is the same. This works because, just like in a 2d area, if you know your exact distance to 3 points, you know where you are, exactly, in 3 dimensions the same is true with 4 points, and in 4 dimensions (3 space+ time) with 5 points. Your phone most likely uses a MEMS oscillator to keep time.
@@aribafaheem7847 It is an example of how small the margin of error in the calculation is. If the answer was 147.81 million km (our distance to the sun) the margin of error is 2 nanometres (the diameter of dna).
The picture at 0:39 is from the construction phase of the ATLAS detector, one of the big experiments around the Large Hadron Collider. We are currently preparing the production and construction of an upgrade to its tracking system, that will make it even better!
@@stephlrideout Building a particle accelerator in space would not be very useful to be honest. Space is already a way better accelerator than anything humans can build (super novae for example). The cosmic particles that hit earth's atmosphere at any time have higher energies than the ones we use in accelerators. So you would have a huge background from cosmic particles. EDIT: I initially also mentioned the location of the LHC being underground to avoid noise from cosmic particles, but as @BlueCosmology rightfully corrected, this is not the case for the LHC. I was thinking of neutrino experiments when typing this ^^
@@Zaczac111 I'm studying engineering and all that rounding pisses me of! The take the unit weight as 10, when is actually around 9.81, I was doing an exam and i used both numbers to compare them, and the results give 30 centimeters of difference! That amount could probably make the whole structure colapse!
@@tlf4354 Well designed exams are used to test your problem solving skills not your arithmetic skills. Once you accept that you won't suffer from rounding effects during exams.
I'm an Astrophysics major in his last year of university... and I was today years old when I found out that use of the word "moment" implies direction and strength of the field in question... I can't believe how many physics classes, and how many chemistry classes I've gone through that discuss electric or magnetic dipole moments and not once have I heard discussion as to why it's referred to as "moment" before now. Thank you SciShow, for giving me the most important bit of information I could have grasped from this video while barely mentioning it as an aside.
Park Tamaroon It’s actually only true for a certain kind of balance - the inertial balance. It works by measuring the rate of vibration in a spring. This is different than the balance with two arms, which effectively measures the gravitational mass. It’s also different from a spring scale, which measures weight.
tim314 Nope, spring scales measure inertial mass. The force exerted on the scale is equal to an object’s inertial mass times its acceleration due to gravity (~9.8 m/s/s on the surface of earth). In the same way that a heavier (greater inertial mass) moving object is hard to slow down (it has more inertia, and therefore requires more force to decelerate), the scales require more force to stop the object from continuing to move downwards under the acceleration due to gravity. You can think of the gravitational mass more as an object’s ability to cause other objects to accelerate towards it. In an ideal world you could put an object of known gravitational mass in a perfect vacuum with your object of interest and look at how they accelerate towards each other to calculate the gravitational mass of your object. In the case of the experiment they talked about here, they essentially used the entire earth as that object of known gravitational mass I think.
It's amazing how accurately us humans can observe and measure the universe. These measurements are what our modern understanding of the universe hinges on, and what really gives me great trust in our theories.
Uncomfortable addendum: there will likely be billions of bloody half-elephants appearing spontaneously on the moon while you're waiting for the whole one.
The time you'd have to wait for that to happen is mindbogglingly large. Don't hold your breath. Or maybe do, because the chance that you would spontaneously disappear out of nowhere is actually larger, because there is less particles in a human than in an elephant.
For personal use, I tend to define morning as when it gets light enough for me to see a bit, which of course happens a few minutes before the sun pokes over the horizon.
So, here in the Netherlands we've got these things, they're called clouds. Only these aren't normal ones, they're special. We can get cloud coverage that's miles high and completely homogeneous. Aka it's literally as if someone painted the sky, it's a completely even monotonous grey. And the best part is, it can last for days in a row! #wheresmyvitDat??
Well, at first humans considered it morning when the sun rises, but once the world got more connected in modern times, we started using our own clocks, not the sun, to tell time, thus making (at least now) the sun rising in the morning
It's the morning that displays the sun. From the moon the sun will be seen as a white disk surrounded by darkness with no morning. "By the sun in its morning brightness, and by the moon as it follows it, by the day as it displays the sun’s glory"
So may crazy things. First I'm thinking how crazy it is that we have technology that can watch a cesium/strontium atom so closely, then I'm thinking how crazy it is that we can achieve a temperature of 15 NANOkelvins, and the many more crazy things throughout the episode. Science is wild.
6:04 - "That's equivalent to measuring the distance to the Moon to within the width of a single red blood cell." Measuring the distance to the Moon should have been the sixth thing - we know that to within a few millimeters. Apache Point Observatory Lunar Laser-ranging Operation (APOLLO) is a system that uses an intense but *extremely* short pulse of laser light fired at the Moon to measure its distance. The pulse is fired off, bounces off the retroreflector left by Apollo astronauts, and returns to the observatory. Because even lasers disperse over that distance, and the amount of light bouncing off the small retroreflector is so minute, the test may end up getting only one photon back. The window for that photon to travel to the Moon and back is so small though that we're able to get the range down to just a few millimeters. Light travels one millimeter in about 6.7 picoseconds, so the duration of the pulse and timing for which we can register the returning photon is extremely tight. I'm sure some folks are wondering how do we know that photon is from the same pulse, not some stray photon - I know I did. The test is performed when the retroreflector is in the shade, either due to the phase of the Moon or a lunar eclipse, and it's performed more than once. The laser pulse is extremely brief, is polarized (as you'd expect from laser light), and it was emitted over a very narrow frequency band - essentially, a very pure color. Taken together, these things let them eliminate 'contamination' of the test with stray photons.
Really good research. There are couple of other experiments in General Relativity used to highlight how precise the theory is, but they are harder to understand. This video really does cover the most important ones. The only additional bit of information worth adding is that we do have some shared components between Standard Model of particle theory and General Relativity, under umbrella of Gauge Theory. I would argue that makes Gauge Theory best verified theory we have, but that's just semantics, honestly. Standard Model and General Relativity individually make way more specific predictions that we've verified.
Gonna be honest, those super cesium clocks could be used to add elevation to GPS, which could be critical for emergency calls that need to account for floors.
4 ปีที่แล้ว +11
I have always been able to accurately determine the "g-factor"... or something like that.
11:50 the way he says everything, idk, i think i picked up on it in an emotional video on vlogbrothers but i cant put my finger on why or what it was for, it just sounds satisfying to me :o
that's what i thought exactly! although the presentation of expanded uncertainty could have been more simplified e.g.: using a "±" sign, instead of brackets (even tho it's already implied). still one of my favorite video by scishow.
Great episode, thanks for posting. I would like to point out one small error. At around 3:15 you mention that the gravitational effects on time dilation at earth's surface are waiting for more precise clocks (if I understood you correctly). But this has long been demonstrated by the Pound-Rebka experiment back in 1959, with detection of a slight change of light wavelength over the height of a building. Mathematically, this directly correlates to time dilation. Other tests have shown this effect over a few meters in a lab.
The sun doesn’t rise in the morning. We define morning as the time the sun rises. Morning comes later and later everyday as the Earth’s rotation slows, so it isn’t a specific duration.
In a billion years the sun won't rise in a 24 hour day. It'll rise after 2.4 days. Just in the last 600,000 years we've seen about 24 hours of slowdown if the 1.8 milliseconds loss every 100 years is correct. It makes me wonder how fast the planet was spinning 3.8 billion years ago. The math turns out to be *-6,333.3* days, or 17.35 years younger for every rotation of the planet. Pretty sure the math is correct I just think they're off on how old the earth really is. Something else to point out if you follow the decrease in our magnetic field Right now it's on average 0.1 to 25 gauze on our planet It decreases on average 5% per century a while ago to 5% per decade within the last 80 years or so. 100,000 years ago it would turn out to be 11,470,000 gauss It would only take 1 million gauss to destroy our bodies. Even if my math was off by 80% we'd still be dead. How do you explain the discrepancies in the age of our Earth the speed of our planet doesn't match up our magnetic field doesn't match up amount of salt in the oceans doesn't match up
A video explaining the metrology reference standards our standard units are based on (length, time, force, voltage, current, etc) would be very interesting.
*_...never had reason to believe an electron is a sphere of charge-as the sphere would have to convolve on itself more-than-rotation (it's made of energy moving at the speed of light), while maintaining sphericity..._*
2:42 "Above the coldest possible temperature" I forgot if SciShow already did a video on this, but fun fact; it's actually possible to go into negative Kelvin. It's kinda a technicality, but also really true. Temperatures (especially of gasses as I understood it) are measured by the _average_ kinetic energy, which means that if you play your cards right you can get some particles in your gas with quite a bit above 0 K, practically no particles at 0 K, and finally a lot of particles below 0 K (which *averages* out to 0 K)
Anytime I see "really true" I know something else is true. The explanation is a tautology. It simplifies to "negative absolute temperatures exist because of negative absolute temperatures". The concept of absolute seems to be missing something here ...
@@ianmcgregor576 I´m not sure it needs negative energy though. Just enough particles at low enough energies to, together with the much higher and definitely above 0 K particles, average out to 0 K. It´s probably because I mix temperature and energy as interchangeable, but aren´t or something like that. Like a single particle has energy, but a collection has temperature and there are whole complicated but complete rules when to use which.
@@AndrewBlucher Probably the part of the sentence directly in front of where you tuned out.... "It's kinda a technicality" A quick duckduckgo search reveals an article at the Max-Planck-Gesellschaft; "According to the physical meaning of temperature, the temperature of a gas is determined by the chaotic movement of its particles - the colder the gas, the slower the particles. At zero kelvin (minus 273 degrees Celsius) the particles stop moving and all disorder disappears. Thus, nothing can be colder than absolute zero on the Kelvin scale. Physicists at the Ludwig-Maximilians University Munich and the Max Planck Institute of Quantum Optics in Garching have now created an atomic gas in the laboratory that nonetheless has negative Kelvin values." www.mpg.de/research/negative-absolute-temperature
USAA freezes my web page every time I see the ad. I will forever find their competitor and give them the money, USAA so obviously wants - for this slight.
Nice, those are great measurements indeed! A few minor remarks: 1. LHC is not the experiment, ATLAS is (in this case). The LHC is "just" the apparatus to accelerate the particles. 2. The clocks in phones and such are based on oscillations in a piezoelectric crystal, which is a different kind of timekeeping that atomic clocks do
I'm sure many pre-humans measured length by breaking objects to size. That log is too long; that twig is too short; that branch is close but will be perfect when I break a piece off.
Though all this really depends on how you define, measure. Most animals and even plants respond to changing time frames, sometimes without outside signals. Is that measurement?
@@phishENchimps I'm sure that a lot of them do know that Flat Earth is nuts, yet they don't mind making themselves look like nuts by pretending to be nuts.
1 metre is defined to be the distance light in a vacuum travels in one 299 792 458th of a second. Which makes the speed of light _exactly_ 299 792 458 m/s.
@@indigo-lily I'm not sure what you mean. As far as I know every measurement system bases its length unit on the meter. So what do you want to measure the length of a meter with?
We know the speed of light exactly, because that's what the meter is based on. What you should be asking is "how precisely do we know how long a meter is?", and that answer would be related to how precisely we know how long a second is, which would be the cesium atom oscillation thing.
That's what I thought. The only thing a balance does is eliminate the effect of the gravitational field strength changing, e.g. on top of a mountain as opposed to sea level, but you're still comparing the gravitational force on your object compared to that on a standard object.
@@Markle2k No it isn't. Except for perhaps a brief moment while the scales are moving, nothing is accelerating. All that is being compared is the force on one tray to the force on the other. In other words, it is comparing weight. Because both weights are being measured in approximately the same location, we assume the gravitational field is the same on both trays, and therefore we can interpret the balance as comparing gravitational mass. But there is no sense that we can interpret them as comparing inertial mass, except that we know from other experiments that the two are equal.
Yep, reckon he misread the script. The cartoon balance shown is useless in zero gravity, he knows that. It compares gravitational mass. Just a blunder that should have been caught in the edit.
All of these measurements are still wildly inaccurate when compared to the accuracy with which my girlfriend can describe just how wrong I am in an argument.
I'm sure some of these are scientists being competitive about who can make the most precise measurement. But hey, the results are useful, so no big deal.
The end was a great explanation of why scientists go around saying they're happy to be shown wrong, and the wronger the better. It really is scary/depressing thinking that as we confirm things to a more and more accurate level, we're running out of the avenues that give us hope for understanding the things we know we don't understand in our lifetime. The easy, feasible avenues, at least.
Holy moly this was a banger of an episode, I love the facts with the big numbers, they make me feel smart. if I counted all of my whoas It would take the same amount of time to watch the entire marvel movies library from the first Captain America movie all the way to Avengers: Endgame a million times. :3 lol
Dear SciShow While I understand error calculation/ uncertainty, I have no idea what Hank was trying to say in relation to the Rydberg Constant uncertainty. His analogy about the distance to the moon and blinking didn't make any sense to me and beyond that, I had no idea what concept he was trying to communicate. But I can be pretty thick sometimes, so it might not be his fault (but it could also be just a bad example/ analogy).
"...we understand the universe ridiculously well." Bold statement. We only understand 6% of the universe and still don't completely understand the little blue dot we live on.
6% Huh. Is that an actual figure, or an exaggeration much like the one your post is about? We do understand the universe very well compared to a pet goldfish.
@@GodlessVoice also if the universe is infinte not even 1% would be achiveble since there is always more to discover even if its just black void but even if its not endless knowing 6% off the universe is still ridiculously much since the intire universe is so so SO big like if we even knew just 6% off the stars in our galaxy thats still probably still more than 1 billion stars and taking the intire universe into accound well you get my point thats what makes it "ridiculous"
So the sun always rises in the morning does it? Everywhere? Hmmmm, I guess you don't know anyone from Tromsø. Good video overall but you get a big [F] for fail today.
Of the quadrillion times that the sun HAS risen in the morning for the rest of humanity in world history, in order to account for the population in the Arctic and Antarctic Circles during the depths of the solstices I guess Hank should say "one quadrillion minus ~20,000,000"
Interesting point. Since morning is often defined as when the sun rises, does Tromsø have "mornings" in middle of summer and winter? I thought the original statement about sun in the morning was a tautology. Now I wonder if there is another definition of "morning" that has meaning near the poles!
@@kowalityjesus Or simply not confuse dawn with morning. One is a measurable event that may or may not happen and the other is an abstraction, a time period linked to the rotation of the Earth on its axis. He was wrong, get over it.
@@DoctorProph3t That is a moronic fallacy, I can see both the metaphor and the facts of the matter, i.e. the science. So tell me what matters most on this particular channel?
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This might be one of my all-time favorite Scishow episodes. Really underscores just how insanely precise and careful much of science is. Makes our own anecdotal experiences seem as flimsy as they really are.
I agree - this was brilliant! I'll watch again a couple of times and then return to it again to grasp the delicious respect for detail. And it's really far away from my own field!
This is not 'much of science.' This is the pinnacle of science; most of science doesn't come close.
Excellent episode. Also makes the point that a lot of science is about trying to disprove science... then failing to a high degree of certainty. There aren't absolute truths, but reducing uncertainty far far below probability of 1% well exceeds our flimsy confirmation biases.
I agree, but I wish he had included a caveat about how inaccurate we can be. That same Standard Model he's talking about made a prediction that differs from the experimental result by 120 orders of magnitude. That is... very wrong
The strontium clock is so accurate that you can measure how much it speeds up when you raise it out of earth's gravity well a fraction of a meter. That makes it the world's most expensive altimeter.
Interesting way to view things
Could this detect mass concentrations under the soil? Could a Strontium Clock give a better view, than Ground Penetrating Radar on ancient buildings? Also, the Apollo missions detected mass concentrations while orbiting the moon, was this the method they used?
DAD: "Son, I said meet me here in 300 million years... NOT 300 million years and 1 second!"
SON: "Sorry Dad, but my Strontium watch is getting repaired so had to use my old Cesium clock."
Tim Sullivan 😂😂
It's true that such precision is ridiculous for our everyday lives, but science needs such precision.
Valryia we know, it was a funny joke though
That was no reason to crucify me!
Leftatalbuquerque what
I expected Hank to say, “Number 1: The Centimeter. Ooooh, that’s a good one.”
Of course, no one knows exactly how long a centimeter is since the definition changed
Richard Wheeler That’s incorrect. The cm is based on the meter, which is based on fundamental constants.
@@richardwheeler6115 1cm is the distance light travels at 1/29979245800 second in vacuum.
@@richardwheeler6115 you're a little uneducated garden gnome aren't you?
@@EmilM-pb2hn he probably still uses Imperial measurements.
I really loved all the analogies in this video, which gave these incomprehensible numbers some more context. The best part was the "elephant on the moon" analogy at the end, neatly wrapping everything up in a bow.
I'm pretty sure more than a few scientists do make absurdly precise measurements just to one-up each other. Academics can be petty too... really petty.
People like to think of scientists as brain robots, but you get the same spread of personalities that you would in any industry.
That's why the scientific method ALWAYS deserves more trust than any individual scientist. We're all human, as amazing and flawed as that means.
that was the biggest suprise for me when i first got into the university. i thought everyone will be a stereotypical scientist yet it is a very good representive mix of society(as much as a male dominated field can)
Actually no you don't have the same spread by a hell of a long way. For a start the number of people with Asperger's in the general populace is about 0.3% with a further 1.3 having Autism (and no they are not the same condition). However the papers here are going with the idiocy in DSM-5 in combining the two despite the fact it is only used in the USA and has been rejected by other governmental health authorities in favour of the ICD-10. blogs.scientificamerican.com/budding-scientist/students-with-autism-gravitate-toward-stem-majors/
Except unlike the rest of the population scientists ACTUALLY know what the hell they're talking about
Uh no. They make these measurements to test theories. And because some of them have practical applications, like GPS.
One second off in a hundred billion years? I’m sorry I just can’t deal with that unreliability right now.
What is the point of existence.
Can't say that I'd lose any sleep over it.
And yet, we humans are too stupid to invent *organic plastic* that composts to soil. Instead we let a greed driven economic system run amoc and burn up the planet and cover the oceans with a decomposable nightmare.
Scientists should really stop celebrating themselves. Most of you are working for psychopaths, either being to scared or to corrupt to say NO.
@@bobrolander4344 and what have you designed to save the world? You ask a lot of the creature you call human. We build upon discovery. We learn how to do something and share the knowledge. Scientist created plastic as something that doesn't need replacement like a paper plates. Plastic bowls that don't rust and the price makes it affordable to the point where people just throw the containers away.
When margarine came on the market in plastic bowls my mom saved them and when the glass bowls were getting broken by us young ones those margarine bowels became bowels we ate our morning cereal in until I left my parents house. People need to put the trash in its proper place rather than just dumping their waste into the streams, rivers and oceans. Thrid world countries are the biggest polluters of waterways.
@@bobrolander4344 I don't know what's going on where you live, but we have had organic, compostible, bio-degradeable plastic for some time now.
I make my boyfriend watch Scishow with me. He has a PhD in Physics with a focus on high energy particles. He sits with me, nods his head, and chuffs in approval. I meanwhile try to understand what the hell is going on. Thanks SciShow for bringing us closer together 😅
I will try that with my gf, she is doing MBBS.
Hope we'll have some us time.
They are very wholesome indeed! Thank you for sharing - that's awesome and beautiful! 🥰
Next week, he will ask you to watch some drama movie together. You cried because you are so touched by the story, meanwhile you bf fell asleep beside you.
What is your area of expertise?
I married my (now ex) husband because he's WAY smarter than I am, but,...
One day, he took me up to A Mountain so we could watch the seasonal monsoon flood the arroyos. Lighting struck and he mentioned how far away it was. I corrected him saying, "Actually, it's 5-7 seconds per mile, (not one) depending on atmosphere." I hear him mumbling to himself, "... Speed of light,... mumble, mumble,... speed of sound, mumble, mumble, mumble,..." Then he goes," Oh yeah, you're right."
That was SUCH a turn on!
At 1:37; but the clock inside my phone isn’t an atomic clock, but synchronized to a system of them if I understand it correctly.
yep, regular quartz clocks for the phone, atomic ones for the satellites. No cesium in our phones, thankfully.
@@wesleybecker834 nah, most use silicon mems oscillators now. You can kill em with helium
@@RobertSzasz indeed! It occurred to me after a while, when I remembered having seen this great video from Applied Science about this very problem: th-cam.com/video/vvzWaVvB908/w-d-xo.html
For GPS, only the satellites need to be accurate. What your phone does is compare the time being broadcast by multiple satellites. If your phone knows where each satellite is supposed to be and what time it's saying it has, you can triangulate your position.
They way they said it was misleading, but what they meant was, your phone's GPS clock time is set using GPS signals. It's a bit complicated, but by receiving 5 signals with a timestamp and exact known location (orbits for GPS satellites are REALLY well known, and are pre-loaded into your GPS), using relativity, you can deduce the current time and position. GPS uses more than 5 for error correction, but the idea is the same.
This works because, just like in a 2d area, if you know your exact distance to 3 points, you know where you are, exactly, in 3 dimensions the same is true with 4 points, and in 4 dimensions (3 space+ time) with 5 points.
Your phone most likely uses a MEMS oscillator to keep time.
"It's like knowing the distance to the sun, within the diameter of your DNA"
It gives me great comfort, to knows it will be there when I need it.
I didn't really get what that means
Can someone please explain?
@@aribafaheem7847
It is an example of how small the margin of error in the calculation is.
If the answer was 147.81 million km (our distance to the sun) the margin of error is 2 nanometres (the diameter of dna).
@@DrunkenAussie76 Ah, I see. Thankyou so much! ^_^
@@DrunkenAussie76 so they might be off by
.000000002 meters
I think I added enough zeros
That fifth fact was my husband’s PhD thesis! Amazing it’s holding up so well.
I love this video, scientists are awesome! Thanks Hank and the rest of SciShow team!
The picture at 0:39 is from the construction phase of the ATLAS detector, one of the big experiments around the Large Hadron Collider. We are currently preparing the production and construction of an upgrade to its tracking system, that will make it even better!
I can't wait until we're able to build a particle accelerator in space
Hank: smiles.
@ParticleFairy
Why though?
What would you be able to detect then that you cannot detect now? :)
@@MrNicoJac It wouldn't have space limitations as on earth, and it wouldn't need a vacuum pump. Plenty of solar power to run it too.
@@stephlrideout Building a particle accelerator in space would not be very useful to be honest. Space is already a way better accelerator than anything humans can build (super novae for example). The cosmic particles that hit earth's atmosphere at any time have higher energies than the ones we use in accelerators. So you would have a huge background from cosmic particles.
EDIT: I initially also mentioned the location of the LHC being underground to avoid noise from cosmic particles, but as @BlueCosmology rightfully corrected, this is not the case for the LHC. I was thinking of neutrino experiments when typing this ^^
This has to be my favorite episode in recent memory
Scientists: come up with accurate and precise constants/measurements.
Engineers: rounds off those constants/measurements.
Rossdhan Ramos ‘Abstract’ versus functional.
@@Zaczac111 I'm studying engineering and all that rounding pisses me of! The take the unit weight as 10, when is actually around 9.81, I was doing an exam and i used both numbers to compare them, and the results give 30 centimeters of difference! That amount could probably make the whole structure colapse!
@@tlf4354 Well designed exams are used to test your problem solving skills not your arithmetic skills. Once you accept that you won't suffer from rounding effects during exams.
Civil Engineers: Pi is 3.
@@webx135 wth 😂
I'm an Astrophysics major in his last year of university... and I was today years old when I found out that use of the word "moment" implies direction and strength of the field in question... I can't believe how many physics classes, and how many chemistry classes I've gone through that discuss electric or magnetic dipole moments and not once have I heard discussion as to why it's referred to as "moment" before now.
Thank you SciShow, for giving me the most important bit of information I could have grasped from this video while barely mentioning it as an aside.
#6: Ligo - measuring the interferometer arm length to fractions of the proton width.
Groovy
I thought that would be on the SciShow list.
This was a great episode! all those comparisons to distances made everything really easy to understand, wonderful job!!
I'm convinced the collider test in 2016 led us to this bizarro timeline. :P
You've said that in every timeline I've visited.
it takes a lot of respect for science to be this excited about metrology. thanks for being you, Hank. Cheers
I love how excited you got presenting this video 🙂🥰
You're on the level, enjoy the sunrise tomorrow right? 😂🤣😂🤔😉
Love the way Hank Green presents, always energetic and livey!
Hank's loquacious extrapolations are reassuringly insightful and yet illuminating and inspirational.
3:50 - a balance scale measures inertial mass, not gravitational mass.
*Woh-woh-woh-woh-woh!*
You can’t just do that as a hit-and-run.
Park Tamaroon It’s actually only true for a certain kind of balance - the inertial balance. It works by measuring the rate of vibration in a spring. This is different than the balance with two arms, which effectively measures the gravitational mass. It’s also different from a spring scale, which measures weight.
3:56 shows a picture of a two-arm balance scale.
Lol
I'm surprised there aren't more people mentioning this.
tim314 Nope, spring scales measure inertial mass. The force exerted on the scale is equal to an object’s inertial mass times its acceleration due to gravity (~9.8 m/s/s on the surface of earth). In the same way that a heavier (greater inertial mass) moving object is hard to slow down (it has more inertia, and therefore requires more force to decelerate), the scales require more force to stop the object from continuing to move downwards under the acceleration due to gravity. You can think of the gravitational mass more as an object’s ability to cause other objects to accelerate towards it. In an ideal world you could put an object of known gravitational mass in a perfect vacuum with your object of interest and look at how they accelerate towards each other to calculate the gravitational mass of your object. In the case of the experiment they talked about here, they essentially used the entire earth as that object of known gravitational mass I think.
Hank Green way of speaking is so relaxing and as a bonus I learn the proper way to pronounce english word ♥
Flat earthers be like: "Time to stop believing in time and mass because there is gravity in them."
Don't give them ideas !!!
They will outstupid us 😂
@@badoem5353 You're too late. They did that ages ago.
@Greg Moonen Yeah, I know. They can connect with other morons anywhere on the planet.
I wonder what makes flat earthers believe in such odd ideas! 🤔
Never argue with an idiot. They'll draw you down to their level and beat you with experience....
This was pretty great way to explain some complicated things!!!!!
Truly amazing.
Is no one noticing the pun about "pulling a number... out of the blue" when measuring elements on a spectrum of colors?! NO!? NO ONE?!
It's amazing how accurately us humans can observe and measure the universe. These measurements are what our modern understanding of the universe hinges on, and what really gives me great trust in our theories.
CONFIRMED: Eventually there will be a spontaneously out-of-nowhere elephant on the Moon.
Uncomfortable addendum: there will likely be billions of bloody half-elephants appearing spontaneously on the moon while you're waiting for the whole one.
That's actually possible because of entropy.
Well, if the universe will exist practically forever.
@@piguyalamode164 odds are, a new one will spontaneously pop into existence too. We can wait for the elephant over there if ours wears out first.
The time you'd have to wait for that to happen is mindbogglingly large. Don't hold your breath.
Or maybe do, because the chance that you would spontaneously disappear out of nowhere is actually larger, because there is less particles in a human than in an elephant.
By far the BEST episode to date!!!!
I thought that "the morning", is when the sun rises... not the other way around?
Does this semantic argument change the underlying meaning in this case? (hint: no)
For personal use, I tend to define morning as when it gets light enough for me to see a bit, which of course happens a few minutes before the sun pokes over the horizon.
@@patrickmccurry1563 for those of us north of 49, morning is whenever we would normally get up to go to work. The sun may or may not join us lol
So, here in the Netherlands we've got these things, they're called clouds.
Only these aren't normal ones, they're special.
We can get cloud coverage that's miles high and completely homogeneous.
Aka it's literally as if someone painted the sky, it's a completely even monotonous grey.
And the best part is, it can last for days in a row!
#wheresmyvitDat??
So the sun is when the morning rises
The way the check pattern of the background fades out towards the center where it is taken up again by hank's shirt is really /r/oddlysatisfying
i have a feeling, that "talking about the elephant on the moon" might be an entirely underappreciated pun. well done :D
This is honestly the most exciting stuff ever.
Not sure if Sun rises in the morning, or if it's morning when the Sun rises
i reckon the egg came first
Well, at first humans considered it morning when the sun rises, but once the world got more connected in modern times, we started using our own clocks, not the sun, to tell time, thus making (at least now) the sun rising in the morning
Well, since the sun isn't really rising, it must be neither.
It's the morning that displays the sun. From the moon the sun will be seen as a white disk surrounded by darkness with no morning.
"By the sun in its morning brightness, and by the moon as it follows it, by the day as it displays the sun’s glory"
Well, since I work nights, the sun sets in my morning but that’s beside the point.
So may crazy things. First I'm thinking how crazy it is that we have technology that can watch a cesium/strontium atom so closely, then I'm thinking how crazy it is that we can achieve a temperature of 15 NANOkelvins, and the many more crazy things throughout the episode. Science is wild.
Love the chalkboard background, Mr. Green. :)
The chalk boa is awesome - I miss those! ❤️
This video saved my life im trying to get in the honor roll every year and i didn't understand the subject , so now indo understand it tysm!!
At 8:10 you left off the units (one over meters). Don't do this to me ever again.
Exactly. Units give the meaning. Without units it's just a number.
It wasn't important to the point but ok
So how thick are the ice walls surrounding the flat earth?
This is probably my favorite SciShow ep. Great job.
6:04 - "That's equivalent to measuring the distance to the Moon to within the width of a single red blood cell."
Measuring the distance to the Moon should have been the sixth thing - we know that to within a few millimeters.
Apache Point Observatory Lunar Laser-ranging Operation (APOLLO) is a system that uses an intense but *extremely* short pulse of laser light fired at the Moon to measure its distance. The pulse is fired off, bounces off the retroreflector left by Apollo astronauts, and returns to the observatory. Because even lasers disperse over that distance, and the amount of light bouncing off the small retroreflector is so minute, the test may end up getting only one photon back. The window for that photon to travel to the Moon and back is so small though that we're able to get the range down to just a few millimeters. Light travels one millimeter in about 6.7 picoseconds, so the duration of the pulse and timing for which we can register the returning photon is extremely tight.
I'm sure some folks are wondering how do we know that photon is from the same pulse, not some stray photon - I know I did. The test is performed when the retroreflector is in the shade, either due to the phase of the Moon or a lunar eclipse, and it's performed more than once. The laser pulse is extremely brief, is polarized (as you'd expect from laser light), and it was emitted over a very narrow frequency band - essentially, a very pure color. Taken together, these things let them eliminate 'contamination' of the test with stray photons.
It's because of things like this that I like science. Science is awesome.
03:05 So......relativistic altimeter? What is your altitude? In my frame or yours?
Really good research. There are couple of other experiments in General Relativity used to highlight how precise the theory is, but they are harder to understand. This video really does cover the most important ones. The only additional bit of information worth adding is that we do have some shared components between Standard Model of particle theory and General Relativity, under umbrella of Gauge Theory. I would argue that makes Gauge Theory best verified theory we have, but that's just semantics, honestly. Standard Model and General Relativity individually make way more specific predictions that we've verified.
"They put the [sulphur hexafluoride] gas in a container..." then breathed it and had fun singing the bass line of popular songs.
Gonna be honest, those super cesium clocks could be used to add elevation to GPS, which could be critical for emergency calls that need to account for floors.
I have always been able to accurately determine the "g-factor"... or something like that.
How do I always read a comment the second they say it on the video??
its hard to decripe, but i love the way Hank sometimes drags out the last part of a word :3
11:50 the way he says everything, idk, i think i picked up on it in an emotional video on vlogbrothers but i cant put my finger on why or what it was for, it just sounds satisfying to me :o
Finally, An episode of Metrology!
that's what i thought exactly! although the presentation of expanded uncertainty could have been more simplified e.g.: using a "±" sign, instead of brackets (even tho it's already implied).
still one of my favorite video by scishow.
Great episode, thanks for posting. I would like to point out one small error. At around 3:15 you mention that the gravitational effects on time dilation at earth's surface are waiting for more precise clocks (if I understood you correctly). But this has long been demonstrated by the Pound-Rebka experiment back in 1959, with detection of a slight change of light wavelength over the height of a building. Mathematically, this directly correlates to time dilation. Other tests have shown this effect over a few meters in a lab.
The sun doesn’t rise in the morning.
We define morning as the time the sun rises.
Morning comes later and later everyday as the Earth’s rotation slows, so it isn’t a specific duration.
So? I dont think this disproves the statement. It just shows that language is weird
Fine then, Captain Semantics, we know that morning will arrive.
No, we really don't. Go ask some in Antarctica when morning is.
@@CorwynGC or anyone who lives any distance from the equator, frankly.
In a billion years the sun won't rise in a 24 hour day. It'll rise after 2.4 days. Just in the last 600,000 years we've seen about 24 hours of slowdown if the 1.8 milliseconds loss every 100 years is correct. It makes me wonder how fast the planet was spinning 3.8 billion years ago.
The math turns out to be *-6,333.3* days, or 17.35 years younger for every rotation of the planet.
Pretty sure the math is correct I just think they're off on how old the earth really is.
Something else to point out if you follow the decrease in our magnetic field Right now it's on average 0.1 to 25 gauze on our planet It decreases on average 5% per century a while ago to 5% per decade within the last 80 years or so. 100,000 years ago it would turn out to be 11,470,000 gauss It would only take 1 million gauss to destroy our bodies.
Even if my math was off by 80% we'd still be dead. How do you explain the discrepancies in the age of our Earth the speed of our planet doesn't match up our magnetic field doesn't match up amount of salt in the oceans doesn't match up
It's really fascinating! You can imagine what they thought 100 years ago but you can't imagine what they'll think 100 years from now.
Huh?
9:15. KILROY!
Doctor Ness Prophet YES! Was gonna have to comment if someone else hadn’t 😂 “Kilroy was here!”
Yep. Funny how that's still showing up after all these years.
Baruch Ben-David Kilroy will find himself on the hulls of interstellar vessels thousands of years from now.
Whenever I hear about sulfur hexafloride, I think of that one Adam Savage clip and it brings me joy
"Keep track of those darn things" kinda like being a parent lol
“Hey honey.”
“Yes dear?”
“Where did Billy go?”
*”DAM IT-“*
The outro about elephants gave me goosebumps.
"There's no elephant. Not yet"
Is there going to be an elephant on the moon soon...?
Possible, yes. Probable, no.
@@naverilllang: It's due after the cow but that won't jump because the steaks are too high.
A video explaining the metrology reference standards our standard units are based on (length, time, force, voltage, current, etc) would be very interesting.
*_...never had reason to believe an electron is a sphere of charge-as the sphere would have to convolve on itself more-than-rotation (it's made of energy moving at the speed of light), while maintaining sphericity..._*
Scientists did the measurements 100 billion times over and found that NO ONE ASKED
2:42 "Above the coldest possible temperature"
I forgot if SciShow already did a video on this, but fun fact; it's actually possible to go into negative Kelvin. It's kinda a technicality, but also really true.
Temperatures (especially of gasses as I understood it) are measured by the _average_ kinetic energy, which means that if you play your cards right you can get some particles in your gas with quite a bit above 0 K, practically no particles at 0 K, and finally a lot of particles below 0 K (which *averages* out to 0 K)
How would a particle have negative energy though?
Anytime I see "really true" I know something else is true.
The explanation is a tautology. It simplifies to "negative absolute temperatures exist because of negative absolute temperatures".
The concept of absolute seems to be missing something here ...
@@ianmcgregor576 I´m not sure it needs negative energy though. Just enough particles at low enough energies to, together with the much higher and definitely above 0 K particles, average out to 0 K.
It´s probably because I mix temperature and energy as interchangeable, but aren´t or something like that. Like a single particle has energy, but a collection has temperature and there are whole complicated but complete rules when to use which.
@@AndrewBlucher Probably the part of the sentence directly in front of where you tuned out.... "It's kinda a technicality"
A quick duckduckgo search reveals an article at the Max-Planck-Gesellschaft;
"According to the physical meaning of temperature, the temperature of a gas is determined by the chaotic movement of its particles - the colder the gas, the slower the particles. At zero kelvin (minus 273 degrees Celsius) the particles stop moving and all disorder disappears. Thus, nothing can be colder than absolute zero on the Kelvin scale. Physicists at the Ludwig-Maximilians University Munich and the Max Planck Institute of Quantum Optics in Garching have now created an atomic gas in the laboratory that nonetheless has negative Kelvin values."
www.mpg.de/research/negative-absolute-temperature
USAA freezes my web page every time I see the ad. I will forever find their competitor and give them the money, USAA so obviously wants - for this slight.
+1
This is the best Sci show episode
So instead of "The Sun will come out tomorrow" we should be singing about the Standard Model?
Nice, those are great measurements indeed! A few minor remarks: 1. LHC is not the experiment, ATLAS is (in this case). The LHC is "just" the apparatus to accelerate the particles. 2. The clocks in phones and such are based on oscillations in a piezoelectric crystal, which is a different kind of timekeeping that atomic clocks do
What’s crazy is that he’s saying all these numbers and my brain is like “huh”
That duck face DP is really telling.
I've been here for a trillion years through the joy through the tears.
So we measured time before we measured length.
@@AxxLAfriku 🎵 with a big iron on his hip 🎶
And we still haven't measured mass with a universal thing. Still have to use those faulty chunks of platinum
I'm sure many pre-humans measured length by breaking objects to size. That log is too long; that twig is too short; that branch is close but will be perfect when I break a piece off.
Though all this really depends on how you define, measure. Most animals and even plants respond to changing time frames, sometimes without outside signals. Is that measurement?
@@Restilia_ch This has changed, recently. Now mass is defined off of some plank constant.
I was about to say there are actually 7 SI units but these are the most most accurate measurements. Well played.
Fun thing about General Relativity is that Einstein predicted everything in it with mathematics. His Math has yet to be proven wrong.
While the math may be flawless, the axioms he chose may be wrong.
This is a very satisfying video
I wanna test out Hanks Large Headron Collider...
no matter how small your... thing is... you can't shoot it at another thing to try and split it.
I'm sorry.
@@LetsPlayCrazy No you are wrong. Ram Ranch has already disproven your theory.
I read that as a Tank of Large Hadron Colliders! I'd like to see that 😀😁😄😃😆😂
You'd have to do an ex-spear-iment
This was WAY more interesting than I expected.
Meanwhile, Flat Erf proponents can't even predict where the sun goes at night.
a few FE'ers are crazy and believe it. others just do it for mental exercise. crazy. but thats what people do.
@@phishENchimps I'm sure that a lot of them do know that Flat Earth is nuts, yet they don't mind making themselves look like nuts by pretending to be nuts.
The scishow team has done a great job, again
How precisely do we know the speed of light?
With 0 uncertainty. It's 299792458 m/s, by definition of the meter.
@@joeybf That doesn't really answer the question, it just rewords it: how precisely do we know the length of a meter?
1 metre is defined to be the distance light in a vacuum travels in one 299 792 458th of a second. Which makes the speed of light _exactly_ 299 792 458 m/s.
@@indigo-lily I'm not sure what you mean. As far as I know every measurement system bases its length unit on the meter. So what do you want to measure the length of a meter with?
We know the speed of light exactly, because that's what the meter is based on. What you should be asking is "how precisely do we know how long a meter is?", and that answer would be related to how precisely we know how long a second is, which would be the cesium atom oscillation thing.
Hank's really having fun doing this wonderful episode!-
Does a balance really measure inertial mass not gravitational mass? I think that's wardbacks.
That's what I thought. The only thing a balance does is eliminate the effect of the gravitational field strength changing, e.g. on top of a mountain as opposed to sea level, but you're still comparing the gravitational force on your object compared to that on a standard object.
Well it is comparing the amount that they are being accelerated by the gravitational field, isn't it?
@@Markle2k No it isn't. Except for perhaps a brief moment while the scales are moving, nothing is accelerating. All that is being compared is the force on one tray to the force on the other. In other words, it is comparing weight. Because both weights are being measured in approximately the same location, we assume the gravitational field is the same on both trays, and therefore we can interpret the balance as comparing gravitational mass. But there is no sense that we can interpret them as comparing inertial mass, except that we know from other experiments that the two are equal.
@@EebstertheGreat And what happens in the free-falling elevator thought experiment? Same gravity field.
Yep, reckon he misread the script. The cartoon balance shown is useless in zero gravity, he knows that. It compares gravitational mass. Just a blunder that should have been caught in the edit.
That was a great episode! Thank you!
I’d love more episode’s on physics :)
Goddamn I love science
@11:49 "Lightning! Lightning! Lightning!"
-James Chumphrey, Donut Media
All of these measurements are still wildly inaccurate when compared to the accuracy with which my girlfriend can describe just how wrong I am in an argument.
Sounds like there is a lot of potential there! Where she is looking, ed. ☺️
From my experience women can repeat "you are wrong" ad infinitum, yet when you ask them to explain why, they remain silent...
Tony Long Find her G Factor and that might help.
@@Bigbuddyandblue 😆
Simp
I thought Gravitational Waves (LIGO experiment) would make an appearence here.
Amazing video!
Random fact: The Paris Agreement on climate change was signed by the largest number of countries ever in one day.
th-cam.com/video/0-1aVVEKep0/w-d-xo.html
@@DanielSMatthews
Bruh
13:41 Everyone in the community: Where is that damn elephant?
Elephant: Not where you are looking.
I'm sure some of these are scientists being competitive about who can make the most precise measurement. But hey, the results are useful, so no big deal.
The end was a great explanation of why scientists go around saying they're happy to be shown wrong, and the wronger the better. It really is scary/depressing thinking that as we confirm things to a more and more accurate level, we're running out of the avenues that give us hope for understanding the things we know we don't understand in our lifetime. The easy, feasible avenues, at least.
None of those measurements were 69. Couldn't have been that great!
Dude
Holy moly this was a banger of an episode, I love the facts with the big numbers, they make me feel smart. if I counted all of my whoas It would take the same amount of time to watch the entire marvel movies library from the first Captain America movie all the way to Avengers: Endgame a million times. :3 lol
Am i the only the one who watches things i don't even know?
i'm i
This is why we all watch SciShow - to learn stuff we don't know!
isnt that the point? learning?
This one was reeeeeaaaaallly good!
Cheers from Germany :-)
Gabrielerklärt hello
From Canada :)
Dear SciShow
While I understand error calculation/ uncertainty, I have no idea what Hank was trying to say in relation to the Rydberg Constant uncertainty. His analogy about the distance to the moon and blinking didn't make any sense to me and beyond that, I had no idea what concept he was trying to communicate. But I can be pretty thick sometimes, so it might not be his fault (but it could also be just a bad example/ analogy).
5 measurements I'm glad I didn't have to know in physics class....non-advanced math physics. ☺
At 4:33 Intertial Mass should be Inertial Mass.
Yay no Imperial system!!
Robby Ramirez Except the thumbnail is an inch ruler
Football fields of freedom! And Olympic swimming pools!
Too bad the world has been dumbed down so far people dont realize the importance of fractional measurements.
This was a really interesting episode! Thanks for the hard work.
"...we understand the universe ridiculously well."
Bold statement. We only understand 6% of the universe and still don't completely understand the little blue dot we live on.
6% Huh. Is that an actual figure, or an exaggeration much like the one your post is about? We do understand the universe very well compared to a pet goldfish.
I have an incredibly good grasp on the English language, but I don't know every word in the dictionary. Both can exist simultaneously.
@@09patrick22barnes95 last estimations made by Stephen Hawkins
@@cultiumera it is, but not what I would call "ridiculously well". 🤔
@@GodlessVoice also if the universe is infinte not even 1% would be achiveble since there is always more to discover even if its just black void but even if its not endless knowing 6% off the universe is still ridiculously much since the intire universe is so so SO big like if we even knew just 6% off the stars in our galaxy thats still probably still more than 1 billion stars and taking the intire universe into accound well you get my point thats what makes it "ridiculous"
That was an amazing episode
So the sun always rises in the morning does it? Everywhere? Hmmmm, I guess you don't know anyone from Tromsø. Good video overall but you get a big [F] for fail today.
Clearly a simple phrase, I feel your dedication to correctness is blinding you to metaphors.
Of the quadrillion times that the sun HAS risen in the morning for the rest of humanity in world history, in order to account for the population in the Arctic and Antarctic Circles during the depths of the solstices I guess Hank should say "one quadrillion minus ~20,000,000"
Interesting point. Since morning is often defined as when the sun rises, does Tromsø have "mornings" in middle of summer and winter? I thought the original statement about sun in the morning was a tautology. Now I wonder if there is another definition of "morning" that has meaning near the poles!
@@kowalityjesus Or simply not confuse dawn with morning. One is a measurable event that may or may not happen and the other is an abstraction, a time period linked to the rotation of the Earth on its axis. He was wrong, get over it.
@@DoctorProph3t That is a moronic fallacy, I can see both the metaphor and the facts of the matter, i.e. the science. So tell me what matters most on this particular channel?
Fantastic episode