What is Astral Light?
The astral light corresponds in the case of our globe, and analogically in the case of our solar system, to what the linga-sarira (Subtle body) is in the case of an individual man. Just as in man the linga-sarira or astral body is the vehicle or carrier of prana or life-energy, so is the astral light the carrier of the cosmic jiva or cosmic life-energy. To us humans it is an invisible region surrounding our earth, as H. P. Blavatsky expresses it, as indeed it surrounds every other physical globe; and among the seven kosmic principles it is the most material excepting one, our physical universe.
The astral light therefore is, on the one hand, the storehouse or repository of all the energies of the kosmos on their way downwards to manifest in the material spheres — of our solar system in general as well as of our globe in particular; and, on the other hand, it is the receptacle or magazine of whatever passes out of the physical sphere on its upward way.
Thirdly, it is a kosmic "picture-gallery" or indelible record of whatever takes place on the astral and physical planes; however, this last phase of the functions of the astral light is the least in importance and real interest.
The astral light of our own globe, and analogically of any other physical globe, is the region of the kama-loka, at least as concerns the intermediate and lower parts of the kama-loka; and all entities that die pass through the astral light on their way upwards, and in the astral light throw off or shed the kama-rupa at the time of the second death.
The solar system has its own astral light in general, just as every globe in the universal solar system has its astral light in particular, in each of these last cases being a thickening or materializing or concreting around the globe of the general astral substance forming the astral light of the solar system. The astral light, strictly speaking, is simply the lees or dregs of akasa and exists in steps or stages of increasing ethereality. The more closely it surrounds any globe, the grosser and more material it is. It is the receptacle of all the vile and horrible emanations from earth and earth beings, and is therefore in parts filled with earthly pollutions. There is a constant interchange, unceasing throughout the solar manvantara, between the astral light on the one hand, and our globe earth on the other, each giving and returning to the other.
Finally, the astral light is with regard to the material realms of the solar system the copy or reflection of what the akasa is in the spiritual realms. The astral light is the mother of the physical, just as the spirit is the mother of the akasa; or, inversely, the physical is merely the concretion of the astral, just as the akasa is the veil or concretion of the highest spiritual. Indeed, the astral and physical are one, just as the akasic and the spiritual are one.