It`s a ….. That the astronomers discovered the planet Neptune not by observing it but by applying mathematics - True Fact - Little-Known fact

True Fact

Explanation:

Neptune was discovered by John Couch Adams in 1846, when he observed that the orbit of the planet Uranus was disturbed and assumed that this must be due to another planet. So, to confirm his suspicions, Adams began a series of mathematical calculations that confirmed his suspicions and allowed Neptune to be discovered.

Neptune was only observed in 1989, by a space probe.

the purpose of the heading in the passage is to identify who is telling the story.

this excerpt is part of the book sugar changed the world (2010) written by marc aronson and marina budhos. as the book has been written by two people, the heading "marc" indicates that this specific excerpt is being narrated by aronson. in the fragment, marc describes his grandfather's story after hearing it from his cousin. however, there are other excerpts where budhos is the one that tells the story of her family.

aronson and budhos, who are husband and wife in real life, decided to write sugar changed the world when they found out how sugar, which had an important role in slavery and economy, changed their ancestors' lives.