Zhao Rong smiled and explained to the three women and his assistant, "You all guessed wrong. The scientific name for this gadget is 'space capsule.' However, it doesn't fly in space, nor does it fly through the air. Of course, it neither sails in water nor runs on land. In a moment, you will see that this gadget can travel swiftly through the earth, just like a mole."
When the three women and the assistant heard that this so-called space capsule could move through the soil like a mole, they couldn't understand the principle behind it. They asked, "Zhao Rong, all vehicles need an environment with very little friction to move. The less friction there is, the faster it can go. For instance, planes are faster than cars because air resistance is lower than the friction on the ground. But now you're saying this thing moves through the soil? Zhao Rong, you have to know that the resistance in soil is extremely high! How could it possibly build up speed? That seems completely impractical."
