Motilal Shastriji explains in his Vigyānbhāshyaṁ of the Shatpath Brahṁaṇā that as we look outwards from the Earth and talk to each other our view is termed bhūgolik or earth-centric and our speech is called Wāk. If we look from the heavens downwards, filtering the cacophony, we hear the natural sounds or what is called Dhwani or music. And this view is termed Khagolik. Thus Vāṇi is the ‘words that are sung’ and it is both Wāk and Dhwani put together. It is the Divine song.
The svars besides sound also contribute the measure of time, called mātrā, to the Wāk. A mātrā is ‘a prosodical unit of one instant’. Phonetically the Svars are of three types viz. short vowels or hrasva, – single meter; long vowels ordīrgha – dual meter and prolongated vowels or pluta of three stops. There are seven short vowels and with the dīrgha added, as we have seen earlier, they are thirteen in number. With the longer, three mātrā pluta versions of the vowels, the count goes up to twenty two.
The consonants combined with these metered vowels give a rhythmic, chanting pattern called the mantrās and these rhythms have seven basic structures called chhands. Now, interestingly the basic count for the number of syllables in these chhands varies from 24 to 48 increasing in steps of 4. These are gayatri (24), ushṇik (28), anushtup (32), brihati (36), pankti (40), trishtup (44) and jagati (48). Pt. Motilal Shastriji has explained these in terms of how the Earth revolves around the Sun. The Earth has a 24o (23.5o to be precise) tilt in its orbit. To us, therefore, the Sun appears to move from above the tropic of Capricorn to above the tropic of Cancer by an angle of 48o approx. in its annual swing. It is this degree of change that the Vedic chhands are attuned to and this is further underlined by the fact that the middle chhand is called brihati (36), meaning ‘the largest’ even though it is in the centre. This is because the Sun is the brightest at the Equator, in-between the two tropics.