Your professor has accidentally stepped through a time portal in his physics lab. You’ve got just a minute to jump through before it closes and leaves him stranded in history. Your only way back is to grab enough colored nodules to create a new portal to open a doorway through time. Can you take the right amount of nodules to get back to the present before the portal closes?

Learn how to solve this time travel riddle by Dan Finkel. Watch this animation by Artrake Studio, then pause at these instructions to find your solution:


Next, try solving the alien probe riddle, the rogue AI riddle, the frog riddle, the fish riddle, and more TED-Ed brain benders on this site.

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