It’s Friday, and I’m sure you’re thinking about the weekend, so today will be just a review and some more details about the speed of light.
And speaking of light, today is the Vernal Equinox. For the next six months (for those of us in the northern hemisphere), our days will be longer than our nights. No doubt the combination of spring, the Equinox, and the weekend, have you wondering what you’re doing at your computer reading about Special Relativity.
I’ll try to be very brief…
Spring!
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Those who know me know that I’m not big on calendar holidays. Even my birthday tends to pass without fanfare. That comes from being single, the island that supposedly no one is. After a lifetime of Christmas and New Years’ being ordinary days, you get used to it.
But I do honor the Solar Event Days because (as I’ve mentioned many times) light is so important to me (and because I’m a geek). Christmas may not mean much to me, but the Winter Solstice does! The days finally start getting longer! Summer Solstice is a day of mourning for the opposite reason.
Today — the Autumnal Equinox — marks the halfway point.
Tonight’s sky holds a half-moon that looks somewhat like the picture on the right. Can you tell me, just by the picture, is the moon getting bigger or getting smaller?
Of course, the moon isn’t really changing size. We use the shorthand “bigger” and “smaller” to refer to how much of the moon we see. Or more properly, how much of the moon is illuminated by the sun. Or even more properly, how much of the moon’s surface facing the Earth is illuminated by the sun.
You can see why we often just say it’s getting “bigger” or “smaller!” Or we can use the terms waxing (getting bigger) and waning (getting smaller).
So, can you tell, from the picture, is the moon tonight waxing or waning?
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