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'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.
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.
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"
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).
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.
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.
To be clear, the clocks in our phones and computers are not "based on cesium" clocks in terms of their design. They are based on crystals and in some cases MEMS devices. Better to say, "the time kept in our phones is based on time kept by cesium clock". Clock refers to the mechanism of time keeping, not the time value itself.
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
Didn't Einstein prove have a better hypothesis about how gravity works? That it isn't a force but is rather just the effect of objects traveling in straight lines in curved space, which would explain why massless objects are affected by gravity. This seems to make more sense than trying to prove that there is such a thing as gravitational mass and that it is equal to inertial mass.
The next step is figure out a way to correct the speed the earth turns by changing it's mass so it syncs better to our strontium watch. If we use a rydberg propulsion based engine we must be able to find the magnetic G spot for the engine very accurate and sync it even better.
#1 I remember reading an article on the NIST site where they mentioned having to adjust one of their cesium clocks when they moved it upstairs a floor or two. #3 Rydberg is pronounced sort of like Rood-bairj, where the j on the end is like a consonant "y" in yes.
@@davidgustavsson4000 How do you pronounce "twenty" in Danish? forvo.com/word/tyve/ ordnet.dk/ddo/ordbog?query=tyve How about "cozy" forvo.com/word/hyggelig/#da Contrast that with the Norwegian. ordnet.dk/ddo/ordbog?query=hyggelig Det er tydeligt at du ikke kender din danske. I am also aware that my Danish grammar is not perfect. Danish is not Norwegian, certainly not rikssvenska. And I am familiar with the snobbish attitude certain Swedes have towards regional accents or dialects. Southwestern Sweden once was Denmark.
3:55 No, a balance definitely measures gravitational mass, not inertial mass. I'm not sure how that line made it through the editing process. Just think about what a balance actually does. It doesn't compare the resistance to acceleration of two objects. It compares the force of gravity on the two in a given location. Gravitational mass is precisely what a balance measures.
It's a bit more subtle than that, since a balance works by, well, balancing two forces and this requiring that F=0=ma. Thus, inertial mass does matter for balances. I'm thinking, but haven't proven, that the way a balance operates will precisely cancel the gravitational effects of both masses and leave just the inertial mass, but you may also be right. Point is, it's more subtle
@@andreweberlein1509 No it isn't. Acceleration is not being measured, force is. Or if we want to be more specific, torque is being measured. If the torque about the pivot is nonzero, then the beam will rotate. Since the two lever arms are of equal length, and the force of gravity is perpendicular to the lever arm when the scales are balanced, the torque can only be zero if equal forces are exerted on both pans. There is no requirement that the pans have the same inertia. Inertia would only affect the rate at which the lever arm rotates, not the direction of rotation. Consider that balances do not even tell you their moment of inertia, because it is not relevant to using them. If you had two objects being compared on a balance with equal gravitational mass but differing inertial mass, the beam still would not rotate, because there would be no torque. But if the two objects had different gravitational mass and equal inertial mass, the beam would rotate toward the object with greater gravitational mass.
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.
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.
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?
I’ve got a question: if gravitation is particularly weak for fundamental forces, why is it the only one that can form black holes? Is it just because it interacts with everything? Or is it something else?
Maybe I'm getting this wrong, but if @ 10:58, there is that big a gap in terms of measurement certainty, isn't that evidence that the standard model is missing something?
That was cool. I wonder if current physics will be looked upon like general relativity looks upon Newton's laws. It's not wrong or small, but looks like foundation stones to a building. You can't fathom the greatness of the later by looking at the first.
"The best mechanical watches gain or lose a second within a day or two." Then I have a remarkably good watch. I set it twice a year because of Daylight Savings time, using my computer's clock, which is synced to a time server that is set by one of those Cesium occilation clocks. I set it a few hundred milliseconds off (specifically, whatever my reaction time is on that particular day plus whatever lag time exists between the actual cesium clock and the light from the display hitting my eyes), and I've only ever seen it more than 10 seconds out when it's been low on batteries and doing a weird thing where it doesn't react for 4 seconds, then suddenly catches up. My watch is better than the best watch. Cool.
“Mechanical watch” specifically means one with a mechanical timekeeping mechanism. If you have a quartz watch, even a cheap one is more accurate than even the best mechanical watches.
@@ragnkja Ahh, that explains it, thanks. Mine's a relatively fancy one from Tissot (commemorating my graduation from uni), but I'd imagine it uses a quartz system if the mechanicals are so much less accurate.
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?
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'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/
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!
@@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).
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
@@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.
@@RobertSzasz indeed! It occurred to me after a while, when I remembered having seen this great video from Applied Science about this very problem: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-vvzWaVvB908.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.
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.
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.
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.
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 ^^
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??
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.
This is the wrong order of magnitude for what he was talking about, but the tiny pressure of your eyelids necessarily pushes them back a tiny amount. I wouldn’t mention something so negligible, but it feels within the spirit of the video to do it this time 😉.
@@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.
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.
*_...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..._*
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.
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?
There is not an atomic clock IN your mobile cell phone or in your satnav for that matter. The GPS satellites have atomic clocks in them and your phone or GPS can access those, but the clock in your phone is otherwise just quartz.
How does one define the number of oscillation. Why does X time of oscillation equals a second. Why not x+1 time equals a second. Is there some math and physics in choosing x value or is it entirely arbitrary according to our old measurement of seconds.
This is what I believe the reason is. Take it with a grain of salt. We had the length of a second, then later decided to define it REALLY well. Turns out what we had as a second was about X oscillations, so they changed the definition of a second to X oscillations.
@@dylanpainter4803 , yeah, like the metre is defined as a specific number of wavelengths of a specific colour of light emission. It USED to be based on 1/10,000 the distance from the North pole to the equator through Paris.
Am I the only one who clicks on these kind of videos, gets lost somewhere, and then just listens without understanding and then just hope to absorb the information as a baby
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.
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.
