Comments on: Is the sun sunnier in southern skies?

Question: Is the sun sunnier in southern skies?

vizsla — Mon, 10 Sep 2007 00:28:55 -0800

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?

By: kindall

kindall — Mon, 10 Sep 2007 00:36:12 -0800

If it's true, which sounds plausible, it'd be because there's less light pollution, not to mention other sorts of pollution.

By: RichardP

RichardP — Mon, 10 Sep 2007 00:42:28 -0800

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.

By: i_am_joe's_spleen

i_am_joe's_spleen — Mon, 10 Sep 2007 01:24:28 -0800

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.

By: rolypolyman

rolypolyman — Mon, 10 Sep 2007 01:33:09 -0800

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.

By: Jimbob

Jimbob — Mon, 10 Sep 2007 03:15:19 -0800

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.

By: signal

signal — Mon, 10 Sep 2007 06:06:36 -0800

Having spent some time in both hemispheres, I haven't observed this. Local conditions have much more effect than what hemisphere you're in.

By: allkindsoftime

allkindsoftime — Mon, 10 Sep 2007 07:12:24 -0800

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.