There are surely cosmic laws in existence.
If the movement of the luminary bodies didn't change (i.e. sun still rises and sets), and we see similar things occurring on our earth (four seasons: fall, winter, spring, summer), then how can this world be in a fallen state? Even the animals hold fast to their habits and activities (i.e. hibernation) and associate only with their own kind. You would have to say that god cursed man alone yet Gen. 3 says god cursed the ground in his stead.
Serve him by singing songs?
Yeah, there’s cosmic laws but it doesn’t dictate the supernatural/spiritual world.
The fall is most apparent in biological life. It caused pain, suffering, disease, and death. How the fall affected the celestial bodies? My first thought was maybe the law of decay but that law was set at creation, it’s necessary law for life. Theoretically, if Adam and Eve didn’t sin they couldve lived forever so there must’ve been something to counterbalance and restore the decaying energy before the fall. When the children of Israel wandered in the wilderness for forty years their clothes and shoes didn’t wear out, there was clearly divine intervention to prevent that. This is just my answer though I’m no expert. I’ve never really thought about how the fall affected the cosmos but I have wondered why there are more planets besides earth and what’s their role in the universe is.
Venus is associated with femininity and sexuality and Saturn for some reason is associated with Satan. I believe there’s answers to all the questions we have about the cosmos but not everything is going to be revealed to us in this state. If you look to the heavens for answers instead of God then you’re not too far off from astrology.
Why do you think we’ll only serve him by singing songs? There will be singing in heaven, he’s worthy of praise. The only responsibilities in heaven that I can recall from scripture is that we will serve him and he who has been “faithful over a few things, I will make you ruler of many things”.