The second

[@tijman1]

VIEW video at 1.25 speed

[@051_cse_mathialagant8]

The best explanation is given by this man.Finally I understood the definition of a second .

[@user-iv2yc9yt7j]

First of all thank you for this very clear professional explanations without musics and without females dirty marketings. I have question, at 4:29 the professor says "we can relate this specific energy to a specific frequency". Now the question is "frequency" is related to "time", but the experiment is to produce accurate time, so from where you got accurate time to generate precise frequency?

[@indieshack4476]

Nice explanation by Pat Gill, I thought the pacing was good. For those of you complaining about the pacing, this is Open University content for those studying for degrees - those of us fortunate enough to have attended a bricks and mortar college recall lecturers pacing delivery too quickly to be able to make notes and comprehend the lecture.

[@andrewbrennan8446]

So if there are 9,172,632,770 periods, how fast is that electron moving?

[@EastBurningRed]

According to wikipedia, the radius of a cesium atom is 265 pm. The circumference is therefore 1.66nm. Multiplying by 9,192,631,770 rotations per second we get 15.3 m/s or 55 km/h or 34 miles per hour. Fast but not highway fast.

[@lunam7249]

c/ alpha constant, c x (1/137) = 3E8 /137 = 2.189781 E6 meters per second...really really fast

[@lunam7249]

@@EastBurningRed although the electron is orbiting the nucleus, we are not mesuring this....we measure its jumping up 1 shell level then dropping back down to the start level, this jumping is happenning 9 billion times per second.... the orbit speed = (light speed c / 137), is so fast it makes quantum cloud😮🎉🎉❤

[@henokbrehanu9426]

Why exactly that weird number of oscillations?

[@asolarasolarasolar]

why cesium?

[@alann2595]

Seems they have a really hard time to explain what they want call a second

[@gauriaggarwall4126]

Thank you sir this was very informative and I finally understood this concept! :)

[@seshachary5580]

very educative. thank you. . regards,

[@anhilatorofignorance2584]

Just used 549 seconds to understand one second

[@headshot308ps3]

why is he talking so slow?

[@KD-sn6pg]

His second is slower.

[@pepper669]

His talking is very precise and that takes time.

[@balwinderkaursandhu9853]

thank you sir

[@Axelios]

This video desperately needs volume boosting and equalling between scenes. I can't watch it because some parts are too quiet to hear, even at max volume.

[@Kapil_vidayak_ji]

good sir

[@glennvang1302]

inter -esting... video.

[@Penguin_of_Death]

Poor presenter...