14
votes
Accepted
How did the year 1904 not have 367 days?
We changed from the Julian calendar of 365.25 days to the Gregorian calendar of 365.2425 days because the old calendar gave us too many leap days.
The mean tropical year has ~365.24219 days, so the ...
- 13.1k
9
votes
How did the year 1904 not have 367 days?
Because the year is actually slightly less than exactly 365.25 days, the standard "one leap-day every four years" pattern makes us overshoot a little; if we didn't fix it, the days would ...
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6
votes
Accepted
How is a comet visible when far from the Sun
We can see it because it refects the light of the sun. It doesn't reflect much light (most comets are dark grey to black on their surface), but as you mention, it is exceptionally large (for a comet)....
- 115k
6
votes
Accepted
Doesn't Gregorian Calendar being started each year on 00:00 cause a huge error in the future?
The Gregorian calendar is designed to approximate the average tropical year, that is the average length of time from one spring equinox to the next.
The actual average length of a tropical year is 365....
- 115k
4
votes
Period-Luminosity Relation of Cepheids via Gaia Data
Here is a similar plot I adapted from Clementini et al. (2019). It shows mean absolute Gaia G-magnitude (derived from Gaia-DR2 parallaxes) versus period for 998 known Cepheid variables. I guess that ...
- 146k
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