This post is based on two articles from the Watchtower society from page 19 paragraph 10 in the brochure, '' A Book for all people" & The September 2016 Study Edition paragraph 12, under the heading Use  Effective Illustrations.

First article
The Watchtower society from page 19 paragraph 10 in the brochure, '' A Book for all people" 

Under The heading " What Holds Up The Earth? In ancient times, humans were perplexed by other questions about the cosmos: What is the earth resting on? What holds up the sun, the moon, and the stars? They had no knowledge of the law of universal gravitation, formulated by Isaac Newton and published in 1687. The idea that heavenly bodies are, in effect, suspended in empty space upon nothing was unknown to them. Thus, their explanations often suggested that tangible objects or substances held the earth and other heavenly bodies aloft. 

For example, one ancient theory, perhaps originated by people who lived on an island, was that the earth was surrounded by water and that it floated in these waters. The Hindus conceived that the earth had several foundations, one on top of the other. It rested on four elephants, the elephants stood on an enormous tortoise, the tortoise stood on an immense serpent, and the coiled serpent floated on universal waters. Empedocles, a Greek philosopher of the fifth century B.C.E., believed that the earth rested upon a whirlwind and that this whirlwind was the cause of the motion of the heavenly bodies. 
Among the most influential views were those of Aristotle. Although he theorized that the earth is a sphere, he denied that it could ever hang in empty space. In his treatise On the Heavens, when refuting the notion that the earth rests on water, he said: “It is not the nature of water, any more than of earth, to stay in mid-air: it must have something to rest upon.”4 So, what does the earth “rest upon”? Aristotle taught that the sun, the moon, and the stars were attached to the surface of solid, transparent spheres. Sphere lay nestled within sphere, with the earth—immobile—at the center. As the spheres revolved within one another, the objects on them—the sun, the moon, and the planets—moved across the sky. 
Aristotle’s explanation seemed logical. If the heavenly bodies were not firmly attached to something, how else could they stay aloft?

Second article
The September 2016 Study Edition paragraph 12, under the heading Use  Effective Illustrations.

12 Effective illustrations can also strengthen a child’s faith in the accuracy of the Bible. For example, consider Job 26:7. (Read.) How might you show that this scripture was inspired? You could just state facts. Instead, why not stimulate your child’s imagination? Bring up the fact that Job lived long before telescopes and spaceships. Your child’s job could be to show how difficult t it might be for some to believe that a very large object, such as the earth, could sit on nothing. The child could use a ball or a stone to illustrate the point by showing that objects with mass have to rest on something. Such a lesson would impress on your child that Jehovah had facts recorded in the Bible long before humans could prove them.—Neh. 9:6.


Also I thought of a though experiment that I really took from the above statement. Imagine their is a base ball that weighed as mush as the earth. Ask the person how would you be able to demonstrate that this heavy sphere can hang on nothing; no solid object!