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@rafaelgonzalez4175

14 күн бұрын

Why is it round up to 3/ms. I would like everyone to know photons can not be measured from the side. Just observe a beam of light. Simple. The very worst part of this video is that the Light from space was thrust forward by unknown force. Splitting of an atom. Or burst of Gas. Either way the universe has frequency and other photons. The universe also has Nebulae. Gas clouds Photons pass through. Light speed is false. I will say it until I die. To calculate the speed of light you need a true particle. Alone in space there is more than one single particle. In space the particle could bounce off of reflective surfaces. Such as the moon. That also questions a laser hitting a target on the moon. If it misses the target it would still bounce back after the surface of the moon absorbed the velocity a bit to reduce the bounce back. There are so many values that can disprove light speed. Fix your thinking. Make it correct. Don't make it valuable to profits.

@c.jishnu378

13 күн бұрын

Also why is your mic magically colour changing?

@TheLostDarkly

12 күн бұрын

There is a book called Lightspeed by John Spence (ASU professor who has since passed) that recounts the history of how we came to measure the speed of light. It's a quick and interesting read that I highly recommend.

@Alexagrigorieff

12 күн бұрын

1 metric angular minute would be 1 kilometer. Coincidentally, 1 angular minute (1/(90*60)) is 1 nautical mile.

@rafaelgonzalez4175

12 күн бұрын

@@Alexagrigorieff Except there are not 60 secs in a minute or 60 minutes in an hour because there are not 24 hours in a day. I have measured it to 23.72 hours in a day. And three days of the year do not see a full day night cycle. Which is why we add an extra day to the calendar every four years.

In case you are wondering, the second is define using a caesium atom

@Chivoton

10 күн бұрын

And the second is also related to the earth’s rotation, which is decreasing. 😅

@spvillano

6 күн бұрын

Both are sources for the measurement of the second, the caesium resonance being a finer standard of precision this week - until something more precise is discovered and rendered reliable. Indeed, I recall proposals to utilize pulsars for time standards, despite their rates also slowing - ever so slowly. But, it does outline one of the arbitrary units selected by humanity - the second. As opposed to coming up with a time standard based upon universal constants, which will never vary as long as we're inside of this universe. At least, they'd better not vary, variable constants would put physics into a cocked hat and take chemistry with it.

Wh-that’s my credit card number!

@sgiri2012

14 күн бұрын

Then expiry date and CVV of your card 😂

@shauryakad5342

14 күн бұрын

😂😂

@troubledouble106

14 күн бұрын

Tell us the four digits in the back of the card. Just wanna know

@Jussimasa-bs9mc

13 күн бұрын

​@@sgiri2012 Yes it is important for science! :D

@sgiri2012

13 күн бұрын

@@Jussimasa-bs9mc 😂 I think so

Yesterday I was talking with Feynman. He said that Mahesh is not interested in Heisenberg Uncertainty Principle, I said to him that no, he loves quantum physics. But he is not ready to believe it. I hope you will make video about explaining Heisenberg Uncertainty Principle and its relationship with enstiens relatively or only explaining it. [Oh, you wonder that how I talked to Feynman? That's because I stole your secret - Magic Mushrooms 🤫🙃]

@advaith_arun

13 күн бұрын

Mom bro is again talking to himself 😂.. but ya he should definitely make a video on The Uncertainty Principle

@well-thy

13 күн бұрын

Hey there! It's me, Feynman. I remember our chat, and I'm still convinced you're dodging the Uncertainty Principle like a quantum ninja! Even Einstein agrees with me. Prove us wrong, Mahesh! Drop some quantum knowledge on us. Until then, I'm in quantum superposition, waiting for you to embrace the uncertainty! Cheers, Feynman (and a very amused Einstein)

@AshirvadTripathi

13 күн бұрын

@@well-thy Yeah, even I am in superposition. I am happy and thankful for his great knowledgeable videos but I am also a bit sad because his quantum mechanics videos are getting too late. Quantum Physics was a bit confusing for me. I always got confused on basic quantum assumptions and theories like "Electron spin". I always wondered how an electron can spin, untill I found his video mentioning about it. His video on Quantum Mechanics (video on electron spin) made me to subscribe and follow his channel. I Hope he post that video soon🤞.

@auriuman78

12 күн бұрын

😂😂😂 you stole Mahesh's secret shrooms stash?

@revmsj

10 күн бұрын

I use an ouija board…🤷🏾‍♂️

But you know what would not be changed by our arbitrary units decisions? The fine-structure constant!

@Alexagrigorieff

12 күн бұрын

That's fine

@june2892

12 күн бұрын

A bunch of thieves. The inventor of interstellar Propulsion Process and spacecraft Photon 137 alpha , commonly known as the Aurora Borealis Launch Vehicle.

@arnoygayen1984

11 күн бұрын

All constants without a unit are independent of our choice of units. The same goes for the fine structure constant.

@VARUNRAJS-IMS

10 күн бұрын

But one would still be able to change it's value if one were to go to different number system, e.g. if we were in octal number system we'll be writing the number differently.

@Rangsk

10 күн бұрын

@@VARUNRAJS-IMS We'd be writing the number differently but it does not change its value.

I request you to make a video on " HOW LONG IS 1 SECOND" It would be a great Idea

@garvitgarg6109

13 күн бұрын

do consider it

@shardulkamble5780

11 күн бұрын

I think that its approximately 1 second long

@aryangupta4372

10 күн бұрын

photon clock example

@ebenolivier2762

10 күн бұрын

I second that.

@chriswebster24

9 күн бұрын

@@shardulkamble5780I just did the math, and your answer seems to be very close. How did you know that?

The definition of the second also impacts this value.

@xalaxie

11 күн бұрын

yes, exactly. I was going to say the same thing, but thought someone else must have made that comment already

@Mahesh_Shenoy

8 күн бұрын

True. But the definition of meter was directly co-related with the planet's size. The definition of the second directly with the planets rotation rate. So maybe a more wholesome video could have been how the planets size and it's rotation rate controlled the value of speed of light! :)

@spvillano

6 күн бұрын

@@Mahesh_Shenoy it's fortunate that the planetary size is unalterable and perpetually static. Perish the thought if the planet were shrinking! Oh, crapmuffins! Oh well, go with a fraction that's approximately correct enough to fudge in, use SI for everything else, pretend it still isn't an arbitrary unit of measure... Largely because, it's a pain in the ass to keep changing standards of measurements and when the metric system was invented, we had absolutely no clue what many constants were, such as oh, ℏ or G and heaven help us, we're talking about C, just to muddle even Planck units that are constant based, rendering constants variable until we finally make up our minds. But then, I'd really be growing to hate life if I had to buy lunch meat in Planck mass units...

Mahesh is a prime example of a person who does not take knowledge for granted. Learning the value of c is knowledge. But mahesh really wants to know "why" it is. Thanks to these kind of people we take knowledge to the next level.

I am an American, and I have done a fair bit of construction, along with fine woodworking and metal fabrication. I can say from my experience, that the metric system is far superior when doing small measurements. For example, drilling and tapping holes is extremely easy. An m6 bolt is 6mm, and the drill size is 5.5mm. Easy peasy. Precision measuring in fine woodworking is way easier too. .5mm is much easier to see on a ruler than 1/16. However, for construction, the cm is an awkward size for cutting boards to. .1mm is too precise, and .5cm is not precise enough. 1/8" is just right. It's just easier using inches. I've tried both. Plus, at this point, all of house construction is based off sheet goods being 4' x 8'. We couldn't switch to metric now if we wanted to. Sheets have to be 4x8 to match the framing. Swapping now would be chaos the likes of which we never seen.

when calculating location at sea, one minute of arc is one NAUTICAL MILE. but that's probably approximate. your videos are startlingly educational. i really thought i was too old to learn anything else! thank you.

@CatFish107

10 күн бұрын

Make sure it's minute arc of latitude, not longitude.

As a child, I thought it rather curious that the earth’s circumference was conveniently a round 40,000 km.

that's why they say that physics is just a Model to understand the universe and not just "the way things are" .......

Love your explanation. Always exciting to listen. Thank you.

very well explained. thanks!

That's why the speed of light has this value in this particular units. Now, why is the speed of light what is is, regardless of the units. Well, it had to be some value, sure. But the speed of light was PREDICTED theoretically, independently of any measurement of the speed of light. The Maxwell equations for electromagnetism has a solution in the vacuum, that is, they give the evolution of the electric and magnetic field with time in a case where there is no charge or magnetic dipole around. That's an electromagnetic wave. The speed of that electromagnetic wave comes that equation, in function of 2 2 other universal constant, seemingly unrelated to light: ϵo and μo, (the permeability and permittivity of vacuum), who describes how good of an insulator and how much magnetic resistance the vacuum has. These values were measured with physical experiments like measuring electric fields around a charged object and magnetic fields around a wire with a current. Seemingly nothing to do with the speed of light. In fact, the fact that the theoretical speed of the electromagnetic wave happened to be exactly what we had already measured to be the speed of light was a strong hint that the light is an electromagnetic wave, something that was not known back then.

@tillyjames

13 күн бұрын

That's more the question I was hoping to be answered! But still a fascinating video. Thanks for the info!

@blackhogarth4049

12 күн бұрын

​@@tillyjamesYeah. I actually expected the video to be about this.

@fuseteam

12 күн бұрын

But as you said those two constants were measured sooo :D

@adb012

10 күн бұрын

@@blackhogarth4049 ... Of course. As I said, the speed of light had to be something. What I found very interesting is that the theoretical prediction of the speed of an electromagnetic wave in the vacuum, in function of these 2 constants that involved no measurement of the speed of light, matched perfectly with the measured value of the speed of light, that nobody knew was an electromagnetic wave. It must have been an amazing "aha!" moment.

Another very interesting question here would be: Where does the second come from?

@MarcusViniciusSilvaDaRosa

14 күн бұрын

It came from the 60th division of the minute, which is known to be used since the ancient times. That's why it's called "seconds", because is the second 60 divisions of the hour. When second was officially adopted as a IS unit, the define the second based on the period of revolution of Earth around its axis, A.K.A., the Earth's day. However, that's very imprecise, since the speed the Earth rotates around its axis varies due to tides, moon, sun and all these stuff. So they define the second as a certain division of the time Earth took to orbit around the sun at the year of 1900. Finally, to make the second a more "natural" unit, like they wanted to do with the IS units in the first place, they define the second based on the inverse of the frequency of a particular electron from cesium-133 takes to jump from one energy state to another. Trust me, this frequency is very wierdly constant, and that's why that's not only the current definition of the second but also the most precise we have came out with

@user-rm5er3rb7t

13 күн бұрын

😂no way you mean that for real: you can just calculate a second from any time period: year, month, hour, millisecond…

@MarcusViniciusSilvaDaRosa

13 күн бұрын

@@user-rm5er3rb7t dont say that. That's actually a great question

@arnesaknussemm2427

13 күн бұрын

It’s the time taken for a Caesium atom to complete 9,192,631,770 oscillations.

@user-rm5er3rb7t

13 күн бұрын

@@MarcusViniciusSilvaDaRosa how that

Great video. The speed of light is also dependent on our definition of the SECOND. You touched on this in the video, that the French considered changing the duration of the measurment of 1 SECOND. The original SECOND, which is what we use today, is based in Babylonian times, when they used a base-60 numbering system rather than our base-10. They subdivided 1 solar-day into 24 hours made up of 60minutes/hour and 60seconds/minute. So if the Earth rotates around the Earth slower or faster, or the revolution of the Earth around the Sun is faster/slower (see difference between solar-day and sidereal-day) the SECOND would be a different duration and our numerical definition of the speed of light would be different. Continuning with this idea, if we used base-60, or base-20, or base-X, rather than a base-10 number system, our numerical value of the speed of light would change. I like to think of the speed of light as 1 planck length/planck time (which is a bit circular in logic, but that's kind of the point of the constant c)

@juliavixen176

13 күн бұрын

The Babylonians didn't use seconds for measuring time. *Nobody* used seconds for time until after the invention of mechanical clocks in the 1500's. And even in the 1600's people only used half or third minute divisions of time. The idea of dividing the (mean solar) hour into "minutes", "seconds", "thirds", and "fourths" was created by Abu Rayhan Muhammad ibn Ahmad al-Biruni in around 1000CE (with regards to the lunar cycle). It was Gauss in the 1800's who proposed using the "Second" as the basis for defining all the other units for measuring time.

Please make complete videos of 11th & 12th physics . The way you teach is just awesome.

Same reason it takes more digits than practical for me to memorize, to define the ratio between pounds and kilograms. They had to maintain consistency with the legacy definitions of the units, when defining the new standard.

Fascinating. Bravo 👏🏻

Hey Mahesh, I just wanted to thank you for your dedication in teaching physics. I relied on most of your lectures in khan academy for class 12. You have explained abstract physics concepts so beautifully.I survived 11th and 12th because of you. Lots of love.♥️

The USA does use the metric system.

I was wondering this seconds before you uploaded it

it's really ridiculous why they haven't rounded to 300K cause neither the pole-equator wasn't measure exactly at the time (using just primitive triangular method) nor the speed of light on that piece of iron :)

@juliavixen176

13 күн бұрын

We could just use "Natural Units" where the speed of light is defined to be exactly "1" ...which is exactly what Physicists do.

Thank you for not using miles, feet , inches amd other nonsesical units

@macheadg5er

12 күн бұрын

and yet you use a 12 hour clock and 90 degree angles etc... lol meter was introduced not because it is better but because the rest of the world wanted to take control. As you can see doing that to time and angles and other areas of measurement is truly nonsensical. You know they actually tried to convert bytes to base 10 and all programmers laughed at them. BASE 16 is much better. BTW he was not kidding when he said 10 hour day they tried to do that and that was epic fail.

@aniksamiurrahman6365

11 күн бұрын

@@macheadg5er Those aren't nonsensical. Dividing a circle into 360 parts is rather so convenient that it's one of the oldest convention, first used by Babylonians 4000 yrs ago, and still being used to this day.

@rickroller1566

9 күн бұрын

@@macheadg5er why would they change bytes to base 10

@BurgoYT

8 күн бұрын

@@macheadg5er360 (so 90) degrees is handy, has a lot of factors

@ginbei711

4 күн бұрын

​@@macheadg5er did you know that feet, mile, inch etc that US love so much is defined by metric/SI units since 1959

Great, now I need a Helium Neon laser and some Cesium-133 to brag about the fish I caught yesterday

8:11 can't they redifine it to 3*10^8m/s instead? Because that is also very close to that, so it wouldn't make much diffrence

@anurupsil8216

14 күн бұрын

I think they did it because, we already had many calculations and other things done with the previous value of the meter. Using the value 3*10^8 will change the defined meter length with a larger value. So we had to redo all those calculations. So they used the value 299792458.

@3141minecraft

14 күн бұрын

@@anurupsil8216 but the diffrence is very small. It is only 0.07% which is very tiny difference, so it shouldn't be a huge problem.

@anurupsil8216

14 күн бұрын

@@3141minecraft Another reason could be because the factorization of ...456 has a 2³, ...457 had a 3², but ...458 only has primes of powers of 1. If it mattered to the physicists... now they considered both of these reasons and considered the optimal value.

@MarcusViniciusSilvaDaRosa

14 күн бұрын

​@@3141minecraft actually those 0.07% make a lot of difference, because the margin of error would be on the meter scale, and we are using it to define the meter itself! That would throw most equipements to dumpster because most of them measure on the scale of centimeters or less. If the meter would be severly affected, imagine the smaller derivatated ones

@3141minecraft

14 күн бұрын

@@MarcusViniciusSilvaDaRosa Nptice: re-defining the speed of light as 3*10^8 m/s changes the meter by a factor of 3*10^8/299792458 So, if we multiply the things that we mesured by that factor should fix that issue.

Nice video. I guess you intend to follow up with another video about the derivation of the speed of light in a vacuum based on how James Clerk Maxwell did it. It is worth it.

Maybe it's that ...456 has a 2³ in its factorisation, ...457 had a 3², but ...458 only has primes to the power of 1. If that's important to physicists...

@JoeAuerbach

14 күн бұрын

That was my thinking as well. I think they probably liked the specific mathematics of it

@artsmith1347

13 күн бұрын

According to WolframAlpha, the prime factorization of 299792458 is 2 × 7 × 73 × 293339 For the speed of light, they should have used a number whose reciprocal has a relatively small number of nonzero digits. The people who came up with the metric system were as loony as the people who defined an inch as the length of three barely corns. Their first attempt: 1/10-millionth of a distance 1) no one had ever measured directly and 2) was inaccessible to anyone who lacked the resources complete a multi-year surveying effort. Their second attempt: the length between two scratches on a bar they squirreled away and made inaccessible. The "experts" who defined the meter were not practical people. A number that factors to 2 × 7 × 73 × 293339 was not a practical choice.

@litigioussociety4249

3 күн бұрын

​@@artsmith1347 Probably because someone was obsessed with the number 73 like Sheldon Cooper.

Quickly becoming my fav physics YT personality

Thank you for interesting content

Wow I knew about the old definition of the meter, but I had no idea how they actually defined it in the first place. The idea that it was to be based on the size of the earth is fascinating, and extremely ambitious.

@MarcelinoDeseo

13 күн бұрын

The base metric units have just been redefined based on the physical constants.

Great video Mahesh

@Mahesh_Shenoy

14 күн бұрын

Thanks ^_^

There's another twist to this story. The actual circumference of this quarter globe measured from the pole, we now know to be 10,002 km. Which means we now need to change the size of our meter. And redefine the speed of light

@adammurphy5350

13 күн бұрын

Meter is already redefined: length of the path travelled by light in vacuum during a time interval of 1/299792458 of a second I.e. the reason the quarter globe is 10002 meters is due to the meter being refined

@Desertphile

13 күн бұрын

The speed of light remains the same regardless of how long a meter is: c is a constant that humans have measured with extreme precision.

@Alexagrigorieff

12 күн бұрын

@@adammurphy5350 whoosh

@__christopher__

12 күн бұрын

@@adammurphy5350 The change to the meter based on the speed of light wasn't that large. Indeed, when the metric system was defined, they measured the meridian precisely for that purpose, and simply made a measurement error.

@rafaelgonzalez4175

12 күн бұрын

@@adammurphy5350 And which 60 sec rule did you use. The 60 sec rule that aligns with the 60 minutes to make an hour? What if there were no 24 hours. Oh wait that is not a what if, that is actual fact. There are not 24 hours in a day. Which concludes there are not 60 minutes to the hour. Which concludes there are not 60 secs to the minute. I have to now ask. What needs to be refined. The Calendar or Time?

Big fan of your videos ❤❤

Thank you for explaining also the reason why the circumference of the earth is pretty close to 40000km (actually 40075.017 km at the equator, and 40007.863 km through the poles)

@kingpiggins292

3 күн бұрын

That's pretty cool I'm assuming the "minor" difference in thickness is due to the centrifugal force as the Earth spins which is kind of crazy to visualize

The decision to define the distance from pole to equator as ten million meters was probably also partly for convenience, as this set the length of a meter to around the same length as a yard (which is about 0.914 meters) and roughly the same order of magnitude as a foot. Also it meant that the height of people would generally land somewhere between 1 and 2 meters and that you could reasonably approximate meters with taking steps (if somewhat longer than you normally would). So, it was all around a pretty convenient length to choose.

Why is your mic magically colour changing?

@jdsaaa66767

13 күн бұрын

Because it's a magic mic

You are awaome ....man ! I enjoy every video you do !

A metre based on one ten millionth that distance is close to a yard, a familiar unit at that time. Btw, metre, not meter: a meter measures things; a metre is a unit of measurement.

@wmpx34

6 күн бұрын

Metre is the British spelling

My supposition on the slight, 2 unit, increase in the ratio between the meter and the speed of causality: the “second” unit, for time, has gone through similar standard updates. The number we have is probably an adjustment due to the second slightly changing.

But if you just said shrew the old number and fixed it at 3*10^8 m/s the old meters would only be off by 1- 299792458/300000000 = 0.00069180666 or about 0.7 mm. I am sure some scientists would be mad at that but if we just clarify what meter were using for a few years while everyone adjusted then we could have such a nice number to represent length until science dies or whatever. And if we did it for the other units like the second, then all of the units and their definitions could be so simple to remember a little kid could remember it. It may even make science just that much more easier for beginners. Personally I am on the team that if it would make 100 scientist mad for every one kid with dyslexia it helped, its worth it.

@SaltHuman

13 күн бұрын

lol

@juliavixen176

13 күн бұрын

We could just use "Natural Units" where the speed of light is defined to be exactly "1" ...which is exactly what Physicists do.

I have a lot of question to that Standard meter bar... E. g. The accuracy was allegedly in 3-digit nanometer range. But how the heck could somebody derive that length from this bar? I mean, the grooved marking lines alone would be several ten micrometer wide. I have the feeling, nobody never ever _used_ these old bars actually.

@JoeAuerbach

14 күн бұрын

You just set the definition to include or exclude the grooves (I believe they excluded it).

@b.s.7693

14 күн бұрын

@@JoeAuerbach and even then you get too much deviation. Due to the grainy structure of metals, even super fine hand made grooves look like inversed rocky mountains at the corresponding maginfication (as a materials scientist, I look at such images every day). It's so hard to define a "line" this way at this level of accuracy... Don't know how they would have handled that. Further, back in the days, the only had light microscopes which can't do more than 1000x. It's barely enough to make out features in the micrometer range. Forget about nanometers...

@anurupsil8216

14 күн бұрын

In fact, the first value of the meter was considered to be 1/40,000,000 of the Paris meridian. Now the Paris Meridian is a 'Meridian Line' passing through the 'Paris Observatory' in Paris, France - 2°20′14.02500″ East Longitude. It was a long-standing rival to the Greenwich Meridian as the world's 'prime meridian'. "Paris meridian arc" or "French meridian arc" (French: la Méridienne de France) is the name of the meridian arc measured along the Paris meridian. where it was calculated by the 'arc measurement method', which is a standard trigonometric process. It is a precise process.

@b.s.7693

14 күн бұрын

@@JoeAuerbach for reference, you can find an image here (I can't link directly, so copy the string): chemie-master[dot]de/pse/lr_urmeter.jpg There was always a group of lines, so bold that you can see them with bare eyes. No matter if you include or exclude them, it seems impossible to me to derive a length measurement in +/- 0.1 microns from that (this was their alledged accuracy).

@TannerJ07

14 күн бұрын

@@b.s.7693they were not handmade, precise tools created the marks.

how was it that a second was defined? if earth was bigger/smaller would the second also have been defined differently? and how would that affect the speed of light constant number that is produced? curious if that would counteract the change in the size of the meter.

@juliavixen176

13 күн бұрын

The SI second in the 1800's was 1/60 of 1/60 of 1/24 of the "Mean Tropical Day". (The location of the Sun in the sky viewed from the surface of Earth.) (Distinct from the "Sidereal Day")

Short form: we can’t explain why this constant is exactly that speed

Never thought about the fact that 1m = 1 decimal arc second of latitude. I always assumed they took the paris distance and just chose a power of 10 that had a useful length. Millimetres (1/1000)m are useful for measuring small things. Metres are useful for measuring things at an intermediate size. Kilometres (1000m) are useful for measuring travel etc.

I'm about 10 seconds in and I hope to God everybody realized that you're talking about.It's based on our measurement system!

Societies around the world came up with 7 days per week. People like using units they’re naturally comfortable with. It’s probably why no one minded when the definition of the “foot” had to change on every king change, because the actual length wouldn’t change too much. The fraction the French earth-measurers chose was highly likely to make the new meter in the same length class as the yard.

12:30 you need the distance from the angle point,to measure arc lenght

8:02 You're right, based on the uncertainty you provided (299,792,456.2 ± 1.1 m/s), rounding to 299,792,458 m/s wouldn't be the most appropriate way to represent the measurement. Here's why they likely chose 299,792,458 m/s: Uncertainty: The uncertainty in your example is 1.1 m/s. This means the true value could be anywhere between 299,792,455.1 m/s and 299,792,457.3 m/s. Rounding to 299,792,458 m/s would lose some information about the uncertainty. Significant figures: Scientists use significant figures to indicate the certainty of a measurement. In your case, considering the uncertainty, the speed of light would likely be reported as 299,792,456 m/s (keeping only the first digit after the decimal point that falls within the uncertainty range). Historical context: It's possible the actual measurement they were referencing had a different uncertainty value. Back in 1983, when the meter was redefined based on the speed of light, the uncertainty in the measurement was likely much smaller than 1.1 m/s. This could explain the specific value of 299,792,458 m/s being chosen for the definition. Overall, if you're referring to a specific measurement with an uncertainty of 1.1 m/s, then reporting 299,792,458 m/s wouldn't be the most accurate way to represent the data. Reporting 299,792,456 m/s (or following proper significant figure guidelines) would be more appropriate

At this point it is a necessity that you do a Q&A episode

Am I the only one that wishes we adapted that full metric system? All those beautiful round numbers! Did rounding the speed of light change the meter enough to make the earth’s circumference 40,008km, because I don’t like that. Can we start over again?

FYI: There were a few times near the end of the video where you said 10 million instead of 10 thousand.

awesome man awesome videos

The decimal division of angles was actually used in France for official topography until 1993. It can be found on some (older?) pocket calculators as an option, as well as degrees and radians. The name of the unit is "grade", subunits being milligrades and so on…

@transfixit

13 күн бұрын

It's still used :) and still available on calculators

Keep it comin

Well, the speed of light in a vacuum is constant, irrespective of the units you choose to use. And the meter was originally based on the circumference of the Earth.

Like always, a very good and interesting video Mahesh! Keep up the great work

perhaps this is the reason why scientists using c = 1 or c = 100% rather than that specific number

@fuseteam

12 күн бұрын

Nah that just cause that simplifies calculations

@spvillano

6 күн бұрын

@@fuseteam who wants simple? Why, it'd be even more entertaining to use everything based off of constants, such as Planck units. Now, the punchline being, think about ordering lunch meats and produce in Planck mass units... Some years ago, a physicist was charged with a minor traffic violation, running a red light. He tried a blue shift defense, alas, the jurist wasn't as conversant in physics as he could have been, otherwise the national debt would've been eliminated by one physicist's defense that he was speeding, so that red appeared green...

@fuseteam

2 күн бұрын

@@spvillano the planck units are exactly wat c=1 is, which greatly simplified physics calculations ;)

Fascinating to consider the relationship between meters (or cm) and milliliter and grams - at least I once learned that a cubic cm of water = 1 millileter, which is same as 1 gram of mass. Which leads down the rabbit hole of mass vs weight

Hello mahesh sir,.... Here's a small doubt.. maybe out of context... If 2 electrons are approaching each other with velocity v then their distance of closest approach is given by using the relation total K. E = potential energy of system of 2 electrons i. e. ½mv²+½mv²= ke²/r...from which r= ke²/mv² But if I try to solve the question using the perspective of first electron , then the relative velocity of second electron should be 2v , therefore, the relation will be ½m(2v) ²= ke²/r....from which r= ke²/2mv²...why the both results are different....? Could you please clarify.. where am I wrong in the analysis?

Great video. I am always amazed to see just how human-centric our science is. It makes sense, I mean our reference point is a human reference point. Thanks for another entertaining video!

Now the question rise in my mind, how did the scientists measured the length to the pole. which instruments did they used for it? And what about the speed of light. which technology is been used for its measurement?

The reason they rounded it up to 299792459 and not 299792457 was to reconcile the relationship of the inch to the centimeter to a wholesome 2.54!!! I figured it out! So that is why they did that number it’s closest to the original meter length that rounds not just the c definition but also metric to imperial units 😊 current inches per second is an integer. However , since 12 inches to a foot and 5,280 feet to a mile is not divisible into that integer the miles per second of c is not an integer but that’s ok neither is the km/s an integer either Edit: ooops false alarm my calculator was rounding it sorry

Good video!

actually, the first value of the meter was considered to be 1/40,000,000 of the Paris meridian. Now the Paris Meridian is a 'Meridian Line' passing through the 'Paris Observatory' in Paris, France - 2°20′14.02500″ East Longitude. It was a long-standing rival to the Greenwich Meridian as the world's 'prime meridian'. "Paris meridian arc" or "French meridian arc" (French: la Méridienne de France) is the name of the meridian arc measured along the Paris meridian. where it was calculated by the 'arc measurement method'.

@ahoj7720

13 күн бұрын

When I was in elementary school in Paris, in the late 1950's, we recited "Le mètre est la dix-millionième partie du quart du méridien terrestre" (The meter is the ten millionth part of one quart of the Earth's meridian)...

@anurupsil8216

13 күн бұрын

@@ahoj7720 that's great

That makes me wonder why a measured distance over 1 second instead of a different number was the definition. A different amount of time might make the speed of light more rounded

Actually GR requires a variable speed of light depending on the amount of gravity there is. The parameters to measure light’s speed change so light’s speed itself changes. It’s not complicated. The combined effect of time speeding up away from the center of a galaxy according to GR while the measure of distance increasing away from the center of the galaxy according to GR makes causation much faster. This is the reason for faster than expected motion of the outer spiral arms of galaxies and superluminal motion appearing to be faster than the speed of light while maintaining the speed of light because causation itself is faster. It’s also the reason we can see distant starlight in 6,000 years because light travels faster between galaxies where there is very little gravity to slow it down.

Alternatively, we could look at the speed of light's definition in terms of seconds. Humanity had a sort-of metric system prior to the french revolution, which was units/subunits be maximimally divisible by integers, into integers for easy math. This led to a lot of things divisible by 12, 24, 60, 360. The second was defined as the **second** subdivision (1/60) of an hour, which itself was defined as 1/24 of a rotation of the earth, relative to the sun (not a sidereal day). So if earth rotated just a bit faster, we'd have c==3E8 m/s exactly. Or if we based hours on sidereal day length, and it was just a little longer...

Question from the video (Why does E= mc²):The energy of Mass (m)is 10J and it loses photons of 2 and .02 J energy. Then why it's mass is not decreased it remains still same in (1/2)mv² but in case 1 the mass decreases . Please sir answer

Cesium light was also used

So, if we switched to metric time, a second would be shorter, and the speed of light would be 259,020,683 m/s ?

@juliavixen176

13 күн бұрын

We can use whatever numbers we want if we're making up new units. Most physicists like to use "Natural Units" where the speed of light is exactly equal to "1".

Grammatical error in the title for later reference, "Why is the speed the of light 299,792,458 m/s? (and not 300,000 km/s)"

@h14hc124

13 күн бұрын

For those still not spotting it - "Why Is the Speed *the* of Light"

I never knew I wanted to know this, but I'm glad blue I know this😮😊😊

I have a question, if we are moving fast shouldn't we arrive at a destination earlier but then why, if we move at the speed of light the time of our destination time moves faster than our personal time. Imagine we are revolving around the earth at the speed of light so our personal time should move slower than the time on earth but the earth itself revolves around the sun which is also moving through space. Even if the space is contracted. What would happen to our position relative to the earth even if we are moving along with the earth and revolving at the speed of light simultaneously

The last 15 minutes, i felt like i was sitting in my high school physics period!

Time & Space, existed at the point, we can't measure Time if can't measure space and vice versa, so ultimately we have to lock one entity either Time or Space, that's why we have first marked 1s then measured space that light travels in 1s. If our time measurements is not accurate then speed of light would also be incorrect or different

I think that the speed of light can be calculated using Maxwell's equations that describe electromagnetism. The equations say that the speed of all electromagnetic waves, including light, equals the ratio of two empirical constants. One constant has to do with the permeability of empty space to electric fields, the other to the permeability to magnetic fields. Of course, one can always ask why these constants take the values they do. Now we have two questions needing answers, whereas there was only one such question about the spssd of light!

12:26 but right angle of arms of what length will subtend an arc of 1km?

@benjamindees

10 күн бұрын

radius of the Earth

In US high schools are students studying science subjects allowed to use metric or are they forced to do calculations using the quaint imperial system?

@parsasaray

13 күн бұрын

my school actually forced us to use the metric system

Actually, the speeed of light not only contains the meter, but also the second. Which means that the speed of light not only depend on the size of the planet, but also on its movement (which decides the average length of a day) and the fact that the Babylonians happened to use a base 60 system (that's the reason why an hour has 60 minutes and minute has 60 seconds), as well as whatever history is behind the day having 24 hours.

This number is just due to the units we use to measure time and distance. But why does it actually have that exact speed which we observe? Like, why is it not half as much or twice as much etc.?

I read somewhere that the speed of light was approximated to that ending with 8 not 7 all because it was easier to convert the current value into inch, and the inch/s would also be a integer, now why inch? Well i think it was because it was in use in that time? Maybe?

I have a followup question... If the speed of light determines the length of a meter (distance), then what determines the unit of time? My understanding is that it is based off vibrations of a Cesium atom. Well, a vibration is simply a motion back and forth, right? The frequency is determined by the distance back and forth, right? Well...If the distance is determined by the speed of light and the second is also determined by the speed of light, aren't we using the speed of light to define itself? Can you please help explain this?

@MarcusViniciusSilvaDaRosa

14 күн бұрын

No. We are not using the speed of light to define the second. We are using the amount of times an electron of the cesium 133 attom takes to jump from a certain energy state to another. When this electron jumps exactly 9,192,631, 770 times, that's how we define that exactly one second has passed. In no moment we need the speed of light to know this value

@ronrothrock7116

14 күн бұрын

@@MarcusViniciusSilvaDaRosaElectron jumps? No, I don't think you have quite the right perception. It is vibrations. Electrons only jump once to a lower orbit and won't do that again unless additional energy is applied to the system. That is something different.

@MarcusViniciusSilvaDaRosa

14 күн бұрын

@@ronrothrock7116 jumping, vibration, the logic will lead to the exact sane conclusion. Vibrations are basically frequency of something. Frequency are measured in Hz or (1/s). They do not use meters on their definition. So we don't have to know the distance between the two energy states that the electron is vibrating, only the ammount of time it does it and set that as exactly equal to the frequency in Hz, which leads to the definition of the second

@ronrothrock7116

14 күн бұрын

@@MarcusViniciusSilvaDaRosa You are making my point, but not seeing it. A frequency is recurrent "bouncing" back and forth (or a non-circular orbit). That is a distance. The string on a guitar vibrates back and forth over a distance and the frequency is how often, but it doesn't change the fact that there is a distance portion to this system we are describing. The electron is traveling a different distance in order to get a vibration frequency. If we assume the electron is jumping orbits like you said, the jump is the distance. Electrons have a total distance they travel over that number of vibrations in 1 second. If the distance were greater the frequency would be lower because it would take longer to travel. So distance is what determines the frequency.

@MarcusViniciusSilvaDaRosa

14 күн бұрын

@@ronrothrock7116 aaaahhh no? This distance you are talking on the guitar string only defines the amplitude of the vibration, not the frequency itself. Your analogy does not stand. Amplitude is measured in m, a distance. Frequency is 1/s. The same guitar string could make the same frequency with different amplitudes, so it does not depend on the distance it bounces. The same logic could apply to the electron, specially knowing that electron suddently jumps from state to another without passing from the middle points between these states

Now I am waiting for a video about the history of one second definition/redefinition.

Don't know yet if you touch down on this as I am only a third through, but the Longitude/Latitude of the Giza Pyramids is the speed of light withing a 20 degree margin of error

So should we redefine units to force simplicity? It's not making the size of the earth change rather giving the measure a new unit. Either new 'time' standard, or new 'length' standard or both?

Mahesh that was really interesting.

Make video on schrodinger wave equation

Isn't it because of fundamental constants of electric and magnetic fields?

@ExistenceUniversity

14 күн бұрын

100% The permittivity and permeability of free space. But the only reason it is in meters and seconds is because we measure the earth in meters and our earth rotation is in seconds.

@Mahesh_Shenoy

14 күн бұрын

Yes. The physical distance that the light would travel in 1 second purely depends on electric and magnetic fields. But the length of this distance in meters depends on how we define meters. And the point of the video is that that is arbitrary and is connected to how and why we define meters.

@b.s.7693

14 күн бұрын

@@ExistenceUniversity exactly that.

@anonymes2884

14 күн бұрын

No, it absolutely *isn't* _because_ "of fundamental constants of electric and magnetic fields". Constants are either theory dependent elements of our _models_ of nature OR empirically determined facts about the universe (e.g. the permittivity of free space is now _defined_ in terms of c so it certainly isn't its "cause" and the permeability is an empirically determined fact i.e. it's an experimentally measured property of the universe). In other words, the "fundamental constants of electric and magnetic fields" _and_ the speed of light are _both_ what they are simply _because_ of the universe we live in. Meaning neither is the _cause_ of the other except in our models and nature doesn't care about our models - always remember that a map is not the territory it depicts.

@ExistenceUniversity

14 күн бұрын

@@anonymes2884 You are wrong.

Sir I am thinking that electron can spin and that has prove by it's wombling so can we say that electron are not the fundamental particle. And it is possible that I can be wrong become I am in class 11 I don't know many things about electrons.

to sum it up for people who still dont understand: scholars hated adapting to every measurement known before since they were not at all precise, so they created one arbitrarily, from scratch, to be the most precise one. thats it.

Blessed with another video! today is a good day

"just saying" no such thing as objective vacum. love you way of phrasing and approach of thinking anyway

How much "smaler" the earth would be if c=300.000.000km/s or how much longer a meter would be?

I am presenting you my intuition about what photon exactly is and tried to combine wave and particle nature in one thread. When we think about particle nature of light, then we assume light as a particle because in some experiments like photoelectric effect, quantisation of light was seen that was not possible if light shows wave nature here. (According to current understanding). In wave nature intensity means greater amplitude while in particle nature , intensity means number of photons. But how this can be possible that a same quantity is defining two completely different things!! Here is my intuition.. let suppose we have a wave with intensity A and frequency F. During phenomena like photoelectric effect, the light wave gets split into numbers of low intensity wave(n) but with same frequency. Each wave have intensity(a) equal to intensity of actual wave divided by total number of new waves formed a= A/n But they also have same frequency. In short the energy of larger wave get equally distributed among smaller waves. Match this process with particle nature. If we increase intensity, number of photons will increase. Same is also happening here, as intensity will increase total numbers of waves will also increase. And how much amplitude would be at each wave will decided by its frequency that is constant for all of them. Conclusion:- The Photon are not very different from waves. They are just the quantised form of light when light get split. (Photon is wave with quantised energy). This unite dual nature of light and also explain why energy of photon(smaller wave) do not depend on intensity rather on frequency. E=hf ( Because frequency of wave determine how much energy to come in smaller waves from larger one) Please reply sir ❤

Another fun fact is that the French National Assembly actually had a numerical error when going through France and calculating Earth's circumference. Which is why Earth's circumference is 40,075km instead of 40,000km

"A rose by any other name is still a rose, and smells as sweet"! Same with 'c' ! I think the poets understood this much before the scientists! Thank you Mahesh for this thought-provoking video.

Maybe if the Earth was bigger, the roation will be slower, day would be longer and so would be a second and finally the speed of light would be the same number.

@suneelsingh9580

10 күн бұрын

The value of second depends on Caesium frequency

It seems you can define the speed to be anything you want. Speed is based on an interval of distance and an interval of time. Change either of those intervals and you get a new speed. It also seems that the speed of light doesn’t have to be the same for all observers, if you define the meter to be 1 wavelength of light or the second to be based off the frequency of light.

@Haris-bg4jy

5 сағат бұрын

You can't really define a meter with those variables. The wavelength and frequency of light exist in a range of possibly infinite values, the definition of a unit of measurement must be a constant value. Changing the definition just changes the symbol we use for the thing and not the thing itself, I can define an year to be 5 revolutions around the sun and suddenly I'm a 5 year old now, but it still means the same thing.