18:13 > the definition of 1 second is the time taken for light to travel c metres This is a circular definition, which would allow the quantities of a metre and a second to vary arbitrarily as long as they varied in the same proportion. The second [...] is defined by taking the fixed numerical value of the caesium frequency, ΔνCs, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 9192631770 when expressed in the unit Hz. (Wikipedia)
@@yashgupta6066 my point, simply, is that in order to measure orbital period of Io, one has to note the time gap between two consecutive emersions ( position D from L and K) or two consecutive immersions ( C from F and G). The confusion arises when Roemer is alleged to measure time gap between an emersion and the immersion.
Amazing explanation, keen to see the upcoming videos!
Thanks for making this video public. Must say, I am dreading this syllabus point!
18:13
> the definition of 1 second is the time taken for light to travel c metres
This is a circular definition, which would allow the quantities of a metre and a second to vary arbitrarily as long as they varied in the same proportion.
The second [...] is defined by taking the fixed numerical value of the caesium frequency, ΔνCs, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 9192631770 when expressed in the unit Hz. (Wikipedia)
How about Galilieo's measurement of light and resonant concavities?
Thank you so much for the simple explanantions!
10:18 idk why I found this funny
Shouldn't the mirror be pushed back by 1/4 of wave length? So the total distance it will travel is 1/2 wave length longer than the other one.
Tôi có suy nghĩ dùng cuộn phim chụp ảnh, cho quay với tốc độ cao, thay cho bánh răng và dùng hệ thức t1=t2=S1/v1=S2/v2 để tính vận tốc ánh sáng.
the Roemer thing is explained wrong! you cant observe both immersion AND emergence at the same time.
thats not what he is explaining
@@yashgupta6066 my point, simply, is that in order to measure orbital period of Io, one has to note the time gap between two consecutive emersions ( position D from L and K) or two consecutive immersions ( C from F and G). The confusion arises when Roemer is alleged to measure time gap between an emersion and the immersion.
Excellent Video. Thanks.
5:42 isn't the diagram on the left the true orbital period, and the shortest orbital period would actually be when the Earth is moiving towards Io?
You’re right! Thanks for pointing that out.