Antigravity may not exist—I'm inclined to believe that it doesn't, anywhere that we know about—but it continues to be useful for writers of speculative fiction. If you can toss off a mention of an antigravity device or a gravity generator, it saves you from having to think up an explanation for, say, travelers on a large spaceship sticking to the floor while they move about the ship. Likewise, hackers who can crack passwords in a matter of seconds or minutes may not exist, or barely exist, but they're useful in stories as a way of skipping ahead.
Thanks for the review!