To be clear the international prototype bars themselves are not that very expensive for so much security. It's that once these metal bars were made and length defined according to that, if they were accidentally manhandled or damaged it would be impossible to make exact same replica and hence one would have to redefine the metre. So they ensured (and still do) high security for many instruments were calibrated first by using these as reference.

@rotten-Z

4 ай бұрын

Recalibrating the entire world is a very expensive undertaking. This made the standards themselves very expensive artifacts.

The metre was originally defined as "one ten-millionth of the length of the Earth's meridian along a quadrant", that is one ten-millionth of the distance from the equator to the North pole. The problem was the above definition brought about a degree of uncertainty and some other issues, so the metre was redefined to the current definition. As such, the number used isn't an arbitrary number but is the number that allowed the new definition to be the same length as the old definition.

I want to see how they actually come up with the meter. Show us how you actually did it NPL.

@hongry-life

3 жыл бұрын

It is based on the faulty assumptions that Eratosthenes made.

@hongry-life

3 жыл бұрын

It's called reversed engineering.

@cometrider2000

3 жыл бұрын

Me too I'm searching around to actually see it done. Demonstrated ; duplicated , replicated , constructed something like that please oh Lord . Anything and everything it's so darn difficult to see the proof of it .

@cometrider2000

3 жыл бұрын

I have to have an accurate clock ; by the time I figure out how to build an electric clock , for how long shall that be accurate before that standard is changed .

Where do I buy my new tape measure that works by the speed of light.

@hongry-life

3 жыл бұрын

Tape is not light :) Maybe a laser tool would do.

huh... okay so the speed of light is defined by meters per second a meter is defined as the distance light travels in a fraction of a second and a second is defined by amount of time it takes a cesium 133 atom to complete 9,192,631,770 cycles ... so how much time does it take for a cesium 133 atom to complete one cycle? the answer is 1 / 9,192,631,770ths of a second! is it just me or is this some kind of paradox?? each measurement unit defines the other

@williamvasquez7889

2 жыл бұрын

It’s a paradox 99/6 of the time.

Any measurement unit can be translated into a speed of light of course. Maybe you could also translate feet and yard and cubit in speed of light in another vid and see which numbers you get and maybe find patterns. The metric system is just 1 of systems to look into.

@karlodebeljak2813

2 жыл бұрын

The imperial system is also based on the metric system so it would be pointless. It has been defined by the metric system since 1959.

@williamvasquez7889

2 жыл бұрын

I’m for the Imperial system, but then again I like to watch paint dry.

The metre is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second.

@hongry-life

3 жыл бұрын

Did you calculate it for a royal cubit?

Sir a doubt without knowing a metre how did you told speed of light is 299 792 482 metres per seconf.

@alexanderwu

3 жыл бұрын

If we use the old definition of meter, the speed of light is about 299 792 482 old meters per second, so our new definition of meter is the length that makes the speed of light 299 792 482 new meters per second

@uzairhussain4856

Жыл бұрын

The particular fraction of 1 second was choosen because they knew that in that small interval of time light covers a distance extremely closer to older meter. So with this new definition of meter, speed of light exactly becomes 299 792 482 m/s. The new definition of meter is invariable in space and time.

@alishonibare

9 ай бұрын

@@alexanderwuynjrHahn

Some forget that the speed of light is defined by using the two fundamental constants of permeability (magnetic) and permittivity (electrical) of a vacuum - it has nothing to do with distance, temperature, gravity

@vikasgupta8948

6 жыл бұрын

Anthony Kernich it has the finite speed which you can calculate by maxwell relation, and its constant in vacuum so we can define length by the relation of (1/299792458)seconds

@samisiddiqi5411

4 жыл бұрын

@@vikasgupta8948 yeah okay that's cool and all, but how exactly is this any helpful for the typical surveyor?

How do we establish that the wavelength is in vacuum? And does quantum theory enter into defining what a vacuum is and how to realize it?

Such a big lab as NPL could have done a way better video on the topic. Video starts with a boring 1mn introduction; spends 2mn opening the vault where a local meter is held, and does not even show is clearly (box says "meter with graduations"; but video does not zoom on any). No close view of the bar. No mention of where to find the historical international one (BIPM in France). Jeremy's message is so important; can't udnerstand why this was omitted.

Thanks Dr.Andrew Lewis Robert lambourne Ewan Macfarlan George Butcher

The fraction of time used to define meter is a number indicating speed of light in (meters/second) itself. Isn't it mind bending in a way because to get that number (2972..) one needs to measure distance traveled by light in meters-- the same quantity which we are trying to define

@stardustsyassine

7 жыл бұрын

:D Imagine if somehow time got slowed down (increased acceleration or something), the other two units will change too?

@Andrew0you0tube

6 жыл бұрын

clyton dantis there is no "meter/second" but there is "metres/second"

@james-ch

6 жыл бұрын

clyton dantis metre not meter

@abhishekjain6452

6 жыл бұрын

clyton dantis no the speed of light isn't defined by metre. It's defined by more fundamental physical constants that have nothing to do with length measurement.

@vikasgupta8948

6 жыл бұрын

Its em wave we can find the speed of light by using maxwell equation I thik you got it :)

A meter is defined in terms of second, one of the basic SI units. Doesn't that make it a derived unit?

Can I, as a citizen, replicate the meter with something cheap? Or do I need extremely expensive equipment to recreate it at home? I would love to do an experiment myself

@samisiddiqi5411

4 жыл бұрын

Nah bro you need to find instruments that calculate the speed of light.

@wakkowarner9522

3 жыл бұрын

Just measure the distance between north pole and equator, and divide by 10,000,000 lol

@lunam7249

Жыл бұрын

yes..make a cheap pedulum with twine, measure and cut it 1 meter long, the pendulum will now swing exactly 1m second a cycle

ok but why 299,792,458?

Since the rate of time changes based on the gravitational field, does this mean that the length of a meter here on Earth is different than the Moon?

@yoppindia

7 жыл бұрын

Morbius907 Good question, closest answer I can give is that you will carry the clock and the instrument to measure with you so you won't feel any change.

@james-ch

6 жыл бұрын

Morbius907 metre not meter

@alexanderwu

3 жыл бұрын

When the rate of time changes, the rate of space changes as well. When time is moving slower, distances become longer

@_.Infinity._

3 жыл бұрын

@@alexanderwu not to mention time dilation. We assume that the speed of light is constant in every direction, for which there is no proof, its just conventionally taken so. For e.g. if we send a signal from earth to moon that time on earth is 12:00 p.m. and say, it took n seconds to reach moon so when the guy on moon see this he will say somehing like "ok check" and add 2n seconds to his clock after setting it to 12:00 p.m. but what if it took the signal which is travelling at the speed of light 2n seconds to reach from earth to and then instantaneously reaches from moon to eaeth. For us the duration is same and we will never know.

@alexanderwu

3 жыл бұрын

@@_.Infinity._ I mean if it makes no difference... Occam's razor

so how do we define speed of light .what defined first and how do we define something without know something .we used speed light to define meter what's the first

Would the length of metre change if the wavelength of light is changed??

@TheLionOfOrange

2 жыл бұрын

late reply but, no. The speed of light in a vacuum is a constant. If wavelength changes, the frequency changes (inversely) proportionally such that the speed is unchanged

@williamvasquez7889

2 жыл бұрын

@@TheLionOfOrange And it is forbidden to urinate against the wind.

@serversurfer6169

Ай бұрын

No, that only affects how powerful the metre is. 🤓

gasdive: Yas and no. c is considered as a universal constant (like Avogrado's number, and Plank constant which are deeply involved in redefining the kg). The meter needs the second; the definition of second could affect the definition of m. That's why many people consider that the real base unit is c (what is ... a speed). For practical reasons, we had to re-define an existing unit. We can not change the world and say "hey, you will stop using the meter, and start using c*t". But from scientific point of view, yes, the basic unit is now c, and m is derived from c. And there is a difference between the technical, and the legal definition. The natural fundamental entity is c; but the legal term will stay m ... even if it technically depends on an other unit. Same mess is about to happen soon for the poor old kg. Wikipedia ... SI_base_unit ... The pciture top right shows that few units are really fundamental: only K, and s at the moment. kg also is, for now, but this will (has to) change very soon. Not speaking about meter (which is your question), A, mol, and cd are already derived from other sources. The relationship between kg and mol and A will probably be reversed; maybe making the mol a new independant root unit, like K and s. You have to understand that the meter is not a subset of the second, because c introduces new concepts that were compeltely absent in the second. m or c can not be replaced by s. They are bonded by the definition of speed formular (V=D/t). Defining only one does not work. You have to define two elements. They are related, by essence. We could as well state about the meter, and c, and then derive time from speed and length (this would be unpractical, and unreliable ... but it could be feasable). Amongst other things, I had, personally, the idea that, if we can define the new kg by counting carbon atoms in a cube, or silicon atoms in a sphere ... we could technically define the meter as being the multiple of the size of a given atom. Such a definition would be a pure length, but would probably be less practical (and less precise), otherwise, the BIPM would have thought about it before me :) We have defined the time according to atoms; and think hard about doing the same for weight; why not length ? (the technical issues would be about the cristal regularity, and variation with temperature). Then c would be a consequence of s and m. Its just better pratical, and more precise (and cheaper) to use s and c. The BIPM does not like the watt-balance ... because it's too expensive, and too hard to duplicate. Takes 10y to build one. By comparison, you can build a good atomic clock within a day, by reusing spare parts from other projects.

@lunam7249

Жыл бұрын

the carbon cube and sphere already done....the cube very interesting, 12 grams , i forgot the details but it was 6.6666666665435cm per side "cubed" made exactly 1 mol down to 1 atom count!! it was so exact they thought it would upset the power of big country labs over little country labs...plus carbon is so cheap....the sphere was similar however, one touch with toilet paper would remove the first layer of outside atoms, so that plan was eliminated

@lunam7249

Жыл бұрын

2:29 "ITS MISSING!!!!"😂😂😂😂🎉🎉

Class 11 physics meter concept is finally clear as compared to class 9 😎

This is difficult for me to actually see a visual demonstration of this measurement unit , so far everything is leading me to this unit of time that you have to construct . I will only accept some thing that is physically tangible or visible . How and where can I see this done, I'm not quite grasping how I can see this here

@williamvasquez7889

2 жыл бұрын

It is also difficult to say 13x7=28.

this is not he one way speed of light instead its the two way speed of light.. nobody has ever measured the one way speed of light. so we actually dono how long is one meter ACTUALLY is

@williamvasquez7889

2 жыл бұрын

What about the speed of a snail?

@prabhuprakashjoseph8060

2 жыл бұрын

little faster than the speed of your brain

The candela is the most enlightening.

Since the metre is defined in terms of a period of time in seconds times c, wouldn't that make it a derived unit rather than a base unit?

@beer_4781

7 жыл бұрын

the way you put it it would. but what do you derive it off. how do you measure space using time? they are different dimensions. like trying to determine how tall a House is by measuting its width. the path light travels in a Second is a distance, it is equal to 299 thousand something something meters. this path is also roughly 3 Times as many feet. but it is still the same path. Take this one exact fraction of that path an you get a meter. and a Second is defined by the number of oscilations between the core and Last Electron of a Cesuim atom. Look it up.

@yoppindia

7 жыл бұрын

Marko Rajić Does the oscillation of cesium atom remain same if I place it next to black hole or if I travel at speed of light? So the derived unit calculation will change based on location and speed.

Thanks

Not a good definition. Why would you define the speed of light to be the distance travelled in 1/(24*60^2) of an earth day? Our current time system sucks. Since metric uses base ten, shouldn't we define it using decimal time, 1/(10^5) of an Earth day? And should it even be defined according to an Earth day? If you change to dozenal time (as I think we should), a second would be 1/248832nd of an Earth day, or 1/10^5 in dozenal. But it would still be defined on an Earth day, which is still not good.

@beer_4781

7 жыл бұрын

that is not the definition of a Second. it is a Lot of oscilations of the core and Last Electronics of a vesuim 131 i beleive, Atom. Look it up.

@stpat7614

7 жыл бұрын

Since the metric system uses base ten, why not define it as the distance light travels in 1/10^n of an Earth day for some very large integer n? Better yet, it on some unit of time that applies to the whole universe. Deriving a metre from an Earth day makes no sense as we start mapping the universe.

@beer_4781

7 жыл бұрын

it is the time it takes for 9 192 641 770 oscilations of the Last Electron of a Cesuim 133 to happen. that defines the second. Not a Solar day. Not earth. Cesuim. And also meters used to, a very long time ago, be determined by long steps. Than the meter long Iridium paladium Bars and now 1/299 thousand something of the distance that light travels in a vacuum in 1s.

Come on man, how the hell am I supposed to find the length of my house with the speed of light?

@hongry-life

3 жыл бұрын

A laser tool could do.

3:44 how the hell is the speed of light "fixed" when it literally slows down in water?

@EnigmatiCognition

3 жыл бұрын

“The meter is the length of path traveled by light in VACUUM during a time interval of 1/299,792,458 of a second"

@GlenwingThink

3 жыл бұрын

It isn't. But when people say "speed of light" it's usually shorthand for "the speed of light *in vacuum* ", which _is_ fixed.

@hongry-life

3 жыл бұрын

@@GlenwingThink How does gravity alter the trajectory of light? Plus unless the natural charge of the earth + the charge of the atmosphere at that certain height is calculated with you cannot be sure of the said speed of light.

Sir, could we have a practical plz!!!!

Uh……what?

How can you use 299,792,458 m/s as a calculation of a metre when it literally uses the metre in of itself???

@mert7742

3 жыл бұрын

im confused tho have u learned the answer

@williamvasquez7889

2 жыл бұрын

I’m confused too. Which came first the chicken or the egg?

Second

Woah😶

@williamvasquez7889

2 жыл бұрын

Woah ain’t that a kick in the head🤡!

Very disappointed with this grossly incomplete presentation.

@williamvasquez7889

2 жыл бұрын

So am I. Hey! Let’s party🎂🤡!