Comment on my kid is movin to AU
zero_gravitas@aussie.zone 6 days agoThe sun isn’t always a fixed distance from earth. It’s closest in January
Forgive me if I’m just missing a joke, but it’s not about the distance, it’s about the angle. In the summer the angle means the days are longer, and sunlight travels through less atmosphere (and is therefore less attenuated) before it reaches you and gives you sunburn.
Tenderizer@aussie.zone 5 days ago
No, it’s not the angle. The sun’s orbit isn’t exactly symetrical, it’s a bit lopsided. In January the sun is about 5% closer to earth.
In the Northern hemisphere this is during winter, so it’s the best of both worlds. In Australia though it’s the reverse. We get extra dim winters and extra bright summers.
zero_gravitas@aussie.zone 5 days ago
Ah, thank you for the clarification! I hadn’t realised that the eccentricity of Earth’s orbit made an appreciable difference, but apparently yeah, especially at the equator: journals.plos.org/climate/article?id=10.1371%2Fjo…
TimePencil@infosec.exchange 5 days ago
@zero_gravitas
Appreciable difference? Not really. But a 'calculable' difference. Sure!
Be sure to appreciate the HUGE difference of the landmasses in the northern and southern hemispheres.
The primary way heat "gets into" our atmosphere is via re-radiation from the "ground".
Compare the amount of "ground" between N45° and the North Pole, with that of the amount of "ocean" between S45° and the South Pole.
At perihelion (around 4th Jan.) the southern hemisphere is in summertime, but the southern oceans easily absorb any extra solar energy by being 'a little bit closer to the sun'. It's roughly equivalent to having the energy used by an extra 5000 cars arrive as solar radiation... and for *most* of that solar energy be absorbed by the ocean.
The tiny (almost insignificant) effect the earth's orbital eccentricity has on weather and climate is FAR less than that of our planet's axial tilt and the position of our continental land masses.
But, sure, if some researchers wish to tweak the underlying data used for the Milankovitch cycles, then, fine.
But our world is still on fire, and our children's future will be ashes unless we act now.
zero_gravitas@aussie.zone 5 days ago
The 7% difference in insolation between perihelion and ahelion (a figure I’ve seen mentioned in multiple places) seems like it would be significant for sunburn and skin cancer, at least at the population level.
I found an ABC article that doesn’t specifically say the 7% figure, but mentions perihelion as a factor in 10% higher UV in Australia. It downplays the role that extra 10% plays in our melanoma rates, though, and I suppose that’s fair, I don’t think anyone’s getting caught out by burning 10% faster, because they would have gone inside 10% sooner if they had known, haha
source: www.abc.net.au/news/science/…/104870806
TimePencil@infosec.exchange 5 days ago
@Tenderizer
Ummm...
"No, it’s not the angle."
Wrong. Axial tilt IS what causes our seasons, NOT the distance from the sun.
Speaking of the sun, "The sun’s orbit isn’t exactly symetrical..."
The sun's orbit? Around what? The centre of the Milky Way?
@zero_gravitas
Tenderizer@aussie.zone 5 days ago
en.wikipedia.org/wiki/Apsis
You’re not 100% wrong. Zero_gravitas answered my comment about the apsis with a comment about the seasons, and I called them wrong even though technically they were just referring to the wrong topic. I was right though, the perihelion occurs in January and the anhelion occurs in July, and that this means the sun is closer to earth during Australian summer than it is during American summer.