BLUEMOMENT

Mention the Equinox

Too little, too late. I feel deflated.

.... Old hat now. Been on the radio all day.
Donald

I'll try harder with 'the Nichts'......

And there was I thinking that the equinox was when the sun crosses the equator and day and night are equal length.

I forgot about defraction, or was it refraction? The atmosphere bending light, which I forgot I knew about from doing celestial navigation years ago. Anyway, equal days and nights don't happen on the equinox, not even at the equator.

My head hurts now

Although some of the inequality of the days and nights at the equinox is indeed due to refraction allowing us to see a sun which is in fact below the horizon, much more is due to the asymmetry of how we define day and night.

Consider the case of a hypothetical day when the time between the sun's hemidiameter crossing the horizon in the morning until it crosses it again at night is exactly half the time between that noon and the next. The length of day and night would still not be equal, because the day starts when the sun's rim appears above the horizon and ends when its rim disappears, so that day would be longer than that night.

Alan_D wrote:Although some of the inequality of the days and nights at the equinox is indeed due to refraction allowing us to see a sun which is in fact below the horizon, much more is due to the asymmetry of how we define day and night.

Consider the case of a hypothetical day when the time between the sun's hemidiameter crossing the horizon in the morning until it crosses it again at night is exactly half the time between that noon and the next. The length of day and night would still not be equal, because the day starts when the sun's rim appears above the horizon and ends when its rim disappears, so that day would be longer than that night.

That's all well and good - but whit if its pishing doon?

Claymore, are you confusing metrology with meteorology? I can sympathise, I have had trouble with my vowels since primary school.

Probably his teeth....
Donald

Ah can see youse fekkers need wan o ma basic fact o'life talks.
If yer wantin sae see ra sun - be that refraction, reflection or fekkin rephrasin, tae tell youse wither er not its day er fekkin nicht, there's rules.
1 - ef ets pishin doon yer hardly likely tae see ra fekkin sun.
2 if ye cannae see whether its dark or light, get alang tae specsavers
3 - if yeve time fer seeing tae ra minute whether we're gettin equal amounts, yer no busy enuff
Xxx