US /'wɔ:peɪdʒ/
・UK /'wɔ:peɪdʒ/
Though you can't step out of the sheet and observe the warpage, what you can do is march around it and measure the circumference.
Same with the warpage in our universe - it stretches or compresses distance between points of space, changing its geometry, in a way that is measurable from within the universe.