Member • Aug 2, 2013
Member • Aug 2, 2013
But if a second was not known, from where 24 hours came into existence ? 😨anoopthefriendMy best guess (this is purely without refering any legitimate sources) is that people who observed the sky understood that it took the Moon 24 hours to revolve around the Earth - this happened very slowly indeed and was perfected over the eras.
Member • Aug 2, 2013
That's what I mentioned -Abhishek RawalBut if a second was not known, from where 24 hours came into existence ? 😨
this happened veryAnd I believe that the larger entity was discovered prior to the smaller entity. Necessity is the mother of invention. When you read the link to show the history of clock face, you'd see how they've used the mechanical motion to derive a minute hand from an hour hand, and later on a second-minute hand (now known as second hand) from the mechanical motion of the minute hand.
slowly indeed and was perfected over the eras.
Member • Aug 3, 2013
Member • Aug 7, 2013
ConquerorWell Cesium is the most stable element in earth Standard temperature Pressure condition
That is why we use Cesium as reference
Man assumed second by comparing the actual solar time with the vibrations of Cesium crystals
We had better understanding of solar time since ages
Member • Aug 8, 2013
Can you pls post the source of this post?Nayan GoenkaI am not sure about this element. But i heard that they studied vibrations of krypton crystals when exposed to some kind of solar energy set up. this gave them one cycle and the time taken by that one cycle came to be known as 1 second.
Member • Aug 8, 2013
The second (abbreviation, s or sec) is the Standard International ( #-Link-Snipped-# ) unit of time. One second is the time that elapses during 9,192,631,770 (9.192631770 x 10 9 ) cycles of the radiation produced by the transition between two levels of the cesium 133 atom.#-Link-Snipped-#
There are other expressions for the second. It is the time required for an #-Link-Snipped-# to propagate 299,792,458 meters (2.99792458 x 10 8 m) through a vacuum. This figure is sometimes rounded to 3.00 x 10 8m, or 300,000 kilometers (3.00 x 10 5 km). One second is equal to 1/86,400 of a mean solar day. This is easy to derive from the fact that there are 60 seconds in a minute, 60 minutes in an hour, and 24 hours in a mean solar day. This definition is, however, subject to limited accuracy because of irregularities in the earth's orbit around the sun.
Engineers and scientists often use smaller units than the second by attaching power-of-10 #-Link-Snipped-# s. One millisecond is 10 -3 s; one microsecond is 10 -6 s; one nanosecond is 10 -9 s; one picosecond is 10 -12 s. During these spans of time, respectively, an EM field propagates through a vacuum over distances of approximately 300 kilometers, 300 meters, 300 millimeters, and 300 micrometers.
The second is sometimes specified as a unit of angular measure, especially in astronomy and global positioning. In these contexts, it is also known as an arc second or a second of arc, and is equal to exactly 1/3600 of an angular degree or 1/1,296,000 of a circle. Sixty arc seconds comprise an arc minute; 60 arc minutes comprise an angular degree. One arc second of latitude at the earth's surface corresponds to a north-south distance of only about 31 m.
