A Hypothetical Question About Antimatter That Does Not End Well

The What If? series by xkcd's Randall Munroe and Henry Reich of MinutePhysics (previously at Neatorama) takes on hypothetical questions no matter how dumb they are. Many of the answers end with "we'd all die," and that explains why this one is so short. The question is, "What if everything was antimatter, EXCEPT Earth?"

Now, antimatter is a difficult concept which they do not try to explain to us, otherwise the video would be hours long and no one would watch it. I don't understand antimatter, either, but if we just fall back on science fiction involving a mirror universe or an alternate reality in which everything is backwards, we can follow the video. You probably won't understand antimatter any better afterward, besides learning it's not a good thing for earth. But listen carefully, and you'll glean some neat stuff, like how at dawn we are facing the direction the earth is moving. We also learn that Munroe, a former NASA engineer, would really like to see another space telescope.