> .. is nonsense. For instance, many core tools of mathematics, measuring systems, astronomy, etc. were developed by Sumerians and Akkadians living in Mesopotamia in 4000–1000 BCE.

It is not "nonsense". Your knowledge of Hindu astronomy is limited. I suggest you to read up on Hindu Astronomy and Measuring systems here: http://www.crystalinks.com/indiastronomy.html

"Ancient India's contributions in the field of astronomy are well known and well documented. The earliest references to astronomy are found in the Rig Veda, which are dated 2000 BC. During next 2500 years, by 500 AD, ancient Indian astronomy has emerged as an important part of Indian studies and its affect is also seen in several treatises of that period. In some instances, astronomical principles were borrowed to explain matters, pertaining to astrology, like casting of a horoscope. Apart from this linkage of astronomy with astrology in ancient India, science of astronomy continued to develop independently, and culminated into original findings, like:

The calculation of occurrences of eclipses
Determination of Earth's circumference
Theorizing about the theory of gravitation
Determining that sun was a star and determination of number of planets under our solar system
There are astronomical references of chronological significance in the Vedas. Some Vedic notices mark the beginning of the year and that of the vernal equinox in Orion. This was the case around 4500 BC. Fire altars, with astronomical basis, have been found in the third millennium cities of India.

Yajnavalkya (perhaps 1800 BC) advanced a 95-year cycle to synchronize the motions of the sun and the moon. A text on Vedic astronomy that has been dated to 1350 BC, was written by Lagadha."

Read up on Kalpa and Yuga: https://en.wikipedia.org/wiki/Kalpa_(aeon)#Hinduism and https://en.wikipedia.org/wiki/Yuga

and the "Hindu units of Time": https://en.wikipedia.org/wiki/Hindu_units_of_time

Also read this book on Hindu cosmology and astronomy: https://www.abebooks.com/book-search/title/the-theogony-of-t...

You can find an archive of the entire book for free here: https://archive.org/stream/theogonyofhindoo00bjrn/theogonyof...

Some quotes from the book:

"The antiquity of the Hindoo Astronomy has
long been a disputed point among the learned of
Europe. Cassini* Bailly,^ Gentil,* and Play/air^
maintain, that there are Hindoo observations
extant which must have been made more than
3000 years before Christ, and which evince even
then a very high degree of astronomical science."

"Davis, who has also taken up this question, calculates that the celebrated Hindoo astronomer
Parasura, judging from the observations made by
him, must have lived 1391 years before Christ
(Asiatic Researches, vol. ii. p. 288), and consequently had read in the divine book of the heavenly firmament, long before the Chaldees, the
Arabs, and the Greeks."

"The religion of the Hindoos, which is called the
Brahmin, is the most ancient of the present systems
of religion upon the earth, and probably one of
the oldest ever known ; in this respect, therefore,
it is deserving of a high degree of attention. The
doctrine is based upon the books of religion held
sacred by the Hindoos, called Vedas, written in
the ancient Sanscrit, which bears the same rela-
tion to the present dialects of the Sanscrit, the
Hindostanee, Bengalee, Tamul, &c, as the Gothic
does to the Swedish, and the Latin to the French
and Italian, (fhe Hindoos maintain that the
Vedas (four books) are contemporary with the
creation, and were revealed by Brahma himself)
The sacred volume begins with these words : —
" (There is only one God, Brahma, omnipotent,
eternal, omnipresent, the great soul, of which all
other gods are but parts\" Nevertheless the
Vedas do not address their hymns to this only God, but to things created by him, as the sun, the
moon, the stars, the earth, fire, &c. ; so that this
religion, although Monotheistic in its fundamental
principle, is tinctured with a kind of Sabceism,
which probably constituted the early religion at
the time when the ancestors of the Hindoos still
dwelt in that country from which they came to
India (from 2500 to 3000 years before Christ).
The Vedas also contain a Cosmogony, the most
ancient that is known."

Also, please don't ignore the fact that most of Hindu knowledge of Mathematics, Astronomy, Science, Philosophy or Religion was transferred by word of mouth for millennia. It was only around 2000-1500 BCE that this knowledge was transferred to scriptures which were written in Devanagari (Sanskrit). Most of these scriptures did not survive, but the knowledge did, because of the stress on rote learning of Mantras (which apart from extolling God and God's virtues also included Scientific/Mathematical concepts). There are many Mantras that have been passed on for generations but the actual scripture is lost.

The problem is that the West had not (and still has not) translated a lot of the Sanskrit scriptures (maybe due to lack of interest) that exist today. The Government of India had setup an ASI (Archaeological Survey of India) to look into translating these scriptures and excavating a lot of ancient cities but due to immense corruption not much progress has happened in this regard. Look up the excavation videos of Submerged City of Dwaraka and why it was abruptly stopped (https://www.youtube.com/watch?v=NVIsjx5X3QM).