astronomical day


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astronomical day

[‚as·trə′näm·ə·kəl ′dā]
(astronomy)
A mean solar day beginning at mean noon, 12 hours later than the beginning of the civil day of the same date; astronomers now generally use the civil day.
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In the previous work [32], we considered the phenomenon of "palindromes", which stands for a high probability of similar histograms to be found upon comparison of two data series: first, representing the results of measurements of [sup.239]Pu [alpha]-decay over astronomical day (since 6 to 18 h by local, longitude, time) and, second, measured over astronomical night (since 18 to 6 h, in continuation of the first series) and inverted.
Thanks to the Earth's erratic rotation, the countdown to 2009 lasted a moment longer as British physicists and official timekeepers around the world inserted a leap second to bring the most accurate atomic clocks in line with the astronomical day.
The cold weather came despite the spring equinox, seen by some as the first day of spring, when the astronomical day and night are equal.

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