If you dig a hole deep enough in American, eventually you would come out in China. This is theoretically possible if the hole is angled in the right way, but if you dig straight down and through the exact center of the earth from anywhere in the 48 contiguous United States, you'd come out in the Indian Ocean. Only in parts of Argentina or Chile would a straight hole emerge in China.
In geography, the antipodes of any place on Earth is the point on the Earth's surface which is diametrically opposite to it. Two points that are antipodal to each other are connected by a straight line running through the centre of the Earth.
The App will show you the antipodes of each point on the Earth's surface by two maps in one page.