There is a lot of confusion when it comes to Lokas. People identify with their material bodies and therefore assume that the material sensual universe is the be all of everything. Lokas do not exist on the physical plane, therefore they are not observable by material scientific instruments. Remember that one of the reasons that your body is cremated is because your subtle body detaches itself from the material body. You are not the body! Why would it be necessary to go to a physical location if you are no longer attached to a physical body?
Remember also that the physical elements are combinations of the subtle elements. For example, the subtle element water does not directly equate to the physical element water; the physical element water is a combination of different subtle elements in different proportions (although predominately the subtle element water). It is the subtle body that goes to the various heavens.
Swami Vivekananda writes (Complete Works V5 pp 101-103, Available here under the heading Epistles – First Series, letter LVII Blessed and Beloved – (http://cwsv.belurmath.org/volume_5/vol_5_frame.htm):
…but Mr. Tesla was charmed to hear about the Vedantic Prâna and Âkâsha and the Kalpas, which according to him are the only theories modern science can entertain. Now both Akasha and Prana again are produced from the cosmic Mahat, the Universal Mind, the Brahmâ or Ishvara. Mr. Tesla thinks he can demonstrate mathematically that force and matter are reducible to potential energy. I am to go and see him next week, to get this new mathematical demonstration.
In that case, the Vedantic cosmology will be placed on the surest of foundations. I am working a good deal now upon the cosmology and eschatology (That is, doctrine of the last things — death, judgement, etc.) of the Vedanta. I clearly see their perfect unison with modern science, and the elucidation of the one will be followed by that of the other. I intend to write a book later on in the form of questions and answers. (This was never done. But from his lectures in London in 1896, it is easy to see that his mind was still working on these ideas. (See also Vol. VIII Sayings and Utterances & Letter to Mr. Sturdy.)). The first chapter will be on cosmology, showing the harmony between Vedantic theories and modern science.
Brahman equate to The Absolute
Mahat or Isvara equates to Primal Creative Energy
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Prana and Akasha equates to Force and Matter
The eschatology will be explained from the Advaitic standpoint only. That is to say, the dualist claims that the soul after death passes on to the Solar sphere, thence to the Lunar sphere, thence to the Electric sphere. Thence he is accompanied by a Purusha to Brahmaloka. (Thence, says the Advaitist, he goes to Nirvâna.)
Now on the Advaitic side, it is held that the soul neither comes nor goes, and that all these spheres or layers of the universe are only so many varying products of Akasha and Prana. That is to say, the lowest or most condensed is the Solar sphere, consisting of the visible universe, in which Prana appears as physical force, and Akasha as sensible matter. The next is called the Lunar sphere, which surrounds the Solar sphere. This is not the moon at all, but the habitation of the gods, that is to say, Prana appears in it as psychic forces, and Akasha as Tanmâtras or fine particles. Beyond this is the Electric sphere, that is to say, a condition in which the Prana is almost inseparable from Akasha, and you can hardly tell whether Electricity is force or matter. Next is the Brahmaloka. where there is neither Prana nor Akasha, but both are merged in the mind stuff, the primal energy. And here — there big neither Prana nor Akasha — the Jiva contemplates the whole universe as Samashti or the sum total of Mahat or mind. This appears as a Purusha, an abstract universal soul, yet not the Absolute, for still there is multiplicity. From this the Jiva finds at last that Unity which is the end. Advaitism says that these are the visions which rise in succession before the Jiva, who himself neither goes nor comes, and that in the same way this present vision has been projected. The projection (Srishti) and dissolution must take place in the same order, only one means going backward, and the other coming out.
Now as each individual can only see his own universe, that universe is created with his bondage and goes away with his liberation, although it remains for others who are in bondage. Now name and form constitute the universe. A wave in the ocean is a wave, only in so far as it is bound by name and form. If the wave subsides, it is the ocean, but those name and form have immediately vanished for ever. So though the name and form of wave could never be without water that was fashioned into the wave by them, yet the name and form themselves were not the wave. They die as soon as ever it returns to water. But other names and forms live in relation to other waves. This name-and-form is called Mâyâ, and the water is Brahman. The wave was nothing but water all the time, yet as a wave it had the name and form. Again this name and form cannot remain for one moment separated from the wave, although the wave as water can remain eternally separate from name and form. But because the name and form can never he separated, they can never be said to exist. Yet they are not zero. This is called Maya.
The Brhadaranyaka Upanishad (IV. iii. 38, and IV. iv. 1-2) describes how the various organs of a man withdraw from the body at the time of death. In the Chandogya Upanishad (V. 10. 1-4) it describes the journey after departing the body. It also describes how when a jiva, who goes to heaven, is wrapped in a thin body of water and dwells in lokas with a thin body of water.
Water, however, does not mean the gross element water. As pointed out in Sankara's commentary to Chandogya Upanishad (V. 4. 2) (Swami Gambhirananda translator):
…[it is] sraddham, faith in the form of water—(the subtle water which is the result of the oblations poured in the Agnihotra sacrifice, is called faith because it is offered with faith…And it is well-known that ‘faith indeed is water; those waters having started from faith (and being associated with special sanctifications) ascend upward.’ (The gods pour as an oblation, that faith in the form of water.)
So the jiva, wrapped in the subtle waters of faith, ascends to the lokas, which are on a spiritual plane, not the physical plane of the observed universe.