The standard unit of time in the SI system is the second, historically defined as 1/86400th of a mean solar day. The modern definitions since 1967 is based upon a caesium atom transition. The Earth's rotation is gradually slowing down meaning that in thousands of years' time the second may need to be redefined to bring it back in line with the mean solar day.
The post explains that a year is defined by Earth's orbital motion around the Sun, encompassing three types: the sidereal year (365.256 days), the tropical year (approximately 365.242 days), and the anomalistic year (365.259 days). It discusses their lengths, differences, and the implications for calendars, notably the transition from the Julian to the Gregorian calendar to align with seasonal changes.
Explores perfect numbers, defined as positive integers equal to the sum of their proper divisors. Examples include 6, 28, and 496, with only 52 known today. It discusses mathematical properties, unsolved questions about odd perfect numbers, historical significance, and the connection to Mersenne primes, highlighting their allure across centuries.
The author shares a curated list of five recommended science books, emphasizing that they are well-reviewed and written by experts in their fields. The selection includes titles from prominent scientists including Neil Degrasse Tyson and David Deutsch, targeting a general audience interested in science.
Updated 7 December 2025 The ashen light is a faint glow, which many people claim to have seen on the night side of Venus. The Italian astronomer Giovanni Riccioli (1598 -1671) first reported it back in 1643, 33 years after Galileo had made the first observations of Venus with a telescope and discovered the planet… Continue reading The Mystery of the Ashen Light of Venus
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