In a 4-cup glass measuring pitcher, pour the cranberry juice, fresh orange juice and fresh lime juice. Stir with a long spoon until the mixture turns one even rosy-orange color, about 15 seconds.

Cover the pitcher and refrigerate the juice mixture for at least 30 minutes, or up to 2 days, so it is properly cold before you pour.

Fill four tall glasses to the rim with ice cubes.

Divide the chilled juice mixture evenly between the four ice-filled glasses, about 3/4 cup in each; the ice will crackle slightly as the cold juice hits it.

Top each glass slowly with 1/2 cup ginger beer, pouring down the inside of the glass rather than straight down the middle, so the fizz builds instead of foaming over.

Drop 6 to 8 fresh cranberries into each glass; they will bob near the surface rather than sinking to the bottom.

Cut four thin wheels from the orange and perch one on the rim of each glass.

Serve the mocktail right away, while the ginger beer is still visibly fizzing.