Is the sun sunnier in southern skies?

September 10, 2007 12:28 AM

Is it true that the skies in the Southern Hemisphere appear brighter and clearer than Northern Hemisphere skies? I have read this several times from various unscientific sources. If so, what is the reason?
posted by vizsla to science & nature (7 comments total)

If it's true, which sounds plausible, it'd be because there's less light pollution, not to mention other sorts of pollution.
posted by kindall at 12:36 AM on September 10, 2007

Well, the Southern Hemisphere has less light polution than the Northern Hemisphere (map), but this wouldn't make the the sun "sunnier" in southern skies — just give one a greater chance of experiencing a clear nighttime sky.
posted by RichardP at 12:42 AM on September 10, 2007

Where I live (New Zealand) there is more UV thanks to ozone depletion. This wouldn't be detectable to the eye though.

NZ comprises a couple of relatively long thin islands surrounded by thousands of miles of sea on all sides, with little industrial air pollution or dust from erosion in the air. So it's plausible that the light would seem harsher and brighter. Visitors do remark on it. And I noticed for example when I was visiting LA a couple of years back that even bright sun seemed dull.
posted by i_am_joe's_spleen at 1:24 AM on September 10, 2007

Sulfur dioxide originates from industrial pollution and is closely linked to haze. The more there is of it, especially in the presence of water vapor, the paler and dimmer the sky is. Google seems to be useless for finding global sulfur dioxide maps and seems intent on returning crap in the searches.

But this is a nice map showing nitrogen dioxide, which is a similar pollutant. As you can see, there are many more sources in the northern hemisphere, while the southern hemisphere is relatively free of it and covered mostly by oceans. About 90% of the world's population is in the northern hemisphere. There's not much surprise the sky is clearer down under.
posted by rolypolyman at 1:33 AM on September 10, 2007

There are also differences between equatorial regions and polar regions. Equatorial regions tend to experience a lot of smoke production from fires, even in the absence of human-made pollution, and the prevailing winds tend to carry the pollution towards the equator. Tropical skies, in my experience, tend to be a hazy, light blue, while closer to the pole (well...the south pole in my case, I haven't really spent that much time in the northern hemisphere) the skies take on a deeper blue colour.

From an astronomical point of view, one would think the equator would be the perfect place to build a big telescope. After all, all the sky, both the southern and northern halves, would be visible to you throughout the year! But, alas, tropical skies are crappy. All the big telescopes tend to be built in more temperate, polar areas, often up mountains where you're above a lot of the haze and pollution.
posted by Jimbob at 3:15 AM on September 10, 2007

Having spent some time in both hemispheres, I haven't observed this. Local conditions have much more effect than what hemisphere you're in.
posted by signal at 6:06 AM on September 10, 2007

I'm going with the light pollution thing.

Grew up in the states, most recently living in NYC, and the best I've ever seen stars is in far-removed mountain areas, like Yosemite.

Have been in South Africa for a month or so now, and was out in northwest SA on safari a couple weeks back. I've never seen the Milky Way like I did that night.
posted by allkindsoftime at 7:12 AM on September 10, 2007