Hast thou perceived the breadth of the earth? - How far the earth extends. To see the force of this, we must remember that the early conception of the earth was that it was a vast plain, and that in the time of Job its limits were unknown. One of the earliest and most obvious inquiries would naturally be, What was the extent of the earth? By what was it bounded? And what was the character of the regions beyond those which were then known? All this was hidden from man at that time, and God, therefore, asks with emphasis whether Job had been able to determine this great inquiry. The knowledge of this is put on the same foundation as that of the depths of the sea, and of the dark regions of the dead, and in the time of Job the one was as much unknown as the other. God, who knew all this, must, therefore, be infinitely exalted above man.

The breadth of the earth? - At that time the circumference of the globe was not known, because the earth itself was supposed to be a vast extended plain, bordered all round with the ocean and the sky.

Hast thou perceived the breadth of the earth?.... Which may be put for all the dimensions of it, length, breadth, diameter, and circumference, but especially it regards the surface of it, and the measurement of that; hast thou gone over the whole face of the earth and measured it, all its parts, its hills and dales, rocks and mountains, and took a survey of all the cities, towns and villages, woods, forests, fountains, rivers, &c? no; if a man lived as long as Methuselah, and spent all his days in this way, he could never be able to do it; and some parts are inaccessible, and not to be measured by the most skilful geometer;
declare, if thou knowest it all; the whole earth and every part of it, and all that is in it. Whether the other hemisphere and the antipodes were known in Job's time is a question; however not America, or the new world, which is a late discovery; and even now, in our most exact maps of the world, some parts are marked with "terra incognita", the unknown land.

Hast thou--as God doth (Job 28:24).

Breadth - The whole compass and all the parts of it?