Issac Newton discovered universal gravitation in 16th century when he observed an apple fall from a tree.
But Prasnopanishad(6000 BC) described the force that pulls objects down and keeps us grounded on earth without floating.
In Prashnopanishad chapter 3 while describing the panchapranas, the apana vayu is said to be residing in the anus and genitals – paayoopasthepaanam.
It is responsible for throwing out from the body faeces, urine, semen, menstrual blood and foetus. Further, the upanishad says : prithivyaam yaa devataa saisha purushasya apaanamavashatabhyaantaraa
The devata that is in earth she supports this apana. She helps apana for throwing out from the body. Space travellers face difficulty in excretion due to absence of gravitational force there. The link between apana and the earth aiding it is quite clear in this upanishad.
Further in his commentary to this upanishad, Adi Shankara ( 5th century BCE ) says
‘tathaa prithivyaam abhimaaninee yaa devataa prasiddhaa saishaa purushasya apaanavrithimavashtabhyaakrishya vasheekrityaadha evapakarshanenanugraham kurvati vartata ityarthaha. anyathaa hi shareeram gurutvat patetsavakashe vaa udagacheta’.
This devata blesses by supporting apana by pulling in the downward direction. Or else, the body would have floated up.