What is the celestial sphere?

The spiritual spheres must consist of something tangible―or the earth could not hold them around it.

The medium before-mentioned says that we have neither cold, heat, nor storms of any kind. Now we beg to differ, for we are here and know about it. That we do not have the coarser earthly storm, we admit―that the elements do not war so violently as on earth, we also admit, but it is not one eternal, everlasting day of intense light here, no more than there. We have a soft dew and many light clouds―we also have gentle rain and sometimes there is quite a breeze, for we have a spiritual atmosphere. Of course, it is very refined and rare, but it is as real to us as the earth's atmosphere is to earth. We also have heat and cold. In fact, heat and cold do not really originate on earth at all, then why suppose that we are not to a certain degree subject to them both? But such is the case, whether accepted by (hu)man―or not, he will soon find it out when he gets here. 

Moreover, we must have homes wherein to educate and care for children, youths and maidens. They are coming here at all times and seasons.

Now if your astronomers can see with the aid of the telescope, nebulae, millions of miles from the earthly sphere, why should it not be accepted that we here in the celestial life have fleecy clouds and gentle rain? exceedingly rarefied to be sure to suit the rare condition of our ethereal atmosphere. Our atmosphere is, after all, something more than ether—it is ethereal, but more dense―or different from the fundamental ether.

―Herr Franz in Spirit