well there is no other explanation. The hadith, well explains all in a really 6th century way. It seems as if when the sun sets, it literally has set someplace and is asking the permission of God to rise again. Maybe if the arabs new about the americas in the far far west it would have been different. anyhow, there are a few points in the hadith. Like "the sun prostrates underneath the throne of God". Throne of God is not a tangible throne rather a symbol of authotity/rule/power whatever you wana call it. And we know that trees, plants etc all prostrate God in their own way.
There may be more to say on this ... InshaAllah ... I'll put up some thoughts only and you can make up your own minds.