Can You Solve the Giant Spider Riddle?
Chat With Your XTutor About This Video Lesson
Lesson Article
A Tale of Competing for the Crown
Once every century, the world’s greatest spiders gather to compete in a series of grueling games. The winner will become the next arachno monarch, able to command all the world’s spiders to their will. That day is today, and for the first time, you’ve cast your name into the ring. From Anansi to Arachne to Aragog, all of the titans of the spider world are here, and at first, no one even notices itsy-bitsy you. But after wowing the crowd with your web design and sticking it to the competition in the long-distance sling, you’ve qualified for the finals. Now all that remains is to face off against the reigning champion, Queen Shelob, on the Whirled Wide Web, and win the title from her.
The Web
The web stretches over a large chasm, with intersecting strands coming to a single point on the other side. Moving across each strand requires a careful dash, and you must keep going until you stop at the next hub where two strands cross. By ancient spider code, only one competitor may traverse the web at a time. You must take turns, moving forward until one of you reaches the other side.
The Challenge
The challenge of Spider Supremacy is to catch Shelob, the spider, by your tenth move. You begin two spaces away from Shelob and the layout of the web is such that every move you make, Shelob can get to an adjacent intersection two away from you. This means that trapping her in a corner is surprisingly tricky, as she can always escape easily. However, there is a point where all the strands converge, which is easy to see is important, but the challenge is figuring out exactly what to do with it.
The Checkerboard Pattern
To make it easier to work with, you can re-visualize the problem by coloring every intersection one of two colors, such as red and blue, where the same color never borders itself. This creates a checkerboard pattern, which is much easier to work with.
Trapping Shelob
At the beginning of the game, every time you move to red, Shelob will be on blue, and every time you move to blue, Shelob will be on red. This means that, unless something changes, you can never move onto the same intersection as her. This is where the point comes in. As indicated by its unique color, it is the one place you can break the pattern and change the rhythm of moves. Therefore, you should waste no time in getting up there.
Shelob could now be in any one of these red spaces, and you have at most 6 moves left to catch her. With the colors we’ve added, we can now focus on the one thing that matters the most: changing the color pattern. Shelob is on red, so you should move onto red on the second or fourth strand. This means that Shelob can never move to any of the spots neighboring you, giving you a kind of net to use to catch her.
Algorithmic Approach
At this point, you may have luck choosing your moves through intuition. However, if you want to get algorithmic about it, you can track the probability of each move.
How far away is she horizontally and vertically? On your move, shrink the larger of the two numbers, and no matter which direction she runs, she will have to hit an edge. Eventually, you will have backed her into one of the two corners and catch up to her at the last possible moment. You snatch the ceremonial sash from your opponent and wrap it around yourself. You are now the Spider Supreme, leader of all the world’s eight-legged wonders. Just remember – with great spider power comes great spider responsibility.
Discussion Questions
- What do you think makes spider supremacy an interesting game?
- How do the spider competitors demonstrate their skills?
- How did you come up with a strategy to win the game?
- Can you think of any other strategies that might have worked in this situation?
- What do you think are some of the responsibilities of being Spider Supreme?
- How do you think the spider competitors feel about competing for the title of Spider Supreme?
- How does it feel to have won the title of Spider Supreme?
- Do you think you would have done anything differently in the competition if you had a second chance?
Lesson Vocabulary
Spider – An arachnid that has eight legs and typically spins webs to capture prey – A small spider crawled along the wall.
Supremacy – The quality of being superior to all others in authority, power, or status – The emperor declared his supremacy.
Arachne – In Greek mythology, a mortal girl who challenged Athena to a weaving contest and was turned into a spider as punishment – The story of Arachne is a cautionary tale about pride.
Aragog – In the Harry Potter series, a giant spider who lived in the Forbidden Forest – Harry and Ron encountered Aragog during their time at Hogwarts.
Anansi – In West African folklore, a spider and trickster figure – Anansi was known for his clever tricks and stories.
Shelob – In the Lord of the Rings series, a giant spider that inhabited Cirith Ungol – Frodo and Sam had to find a way to get past Shelob in order to continue their journey.
Whirled – A form of dance popularized in the 1950s that is a blend of swing and jitterbug – He went to the sock hop to learn how to whirled.
Wide – Having a large distance from side to side – The lake was wide enough to fit an entire fleet of boats.
Web – A structure made of threads spun by a spider or other organism – The spider moved quickly across her web.
Chasm – A deep opening in the earth’s surface – We had to cross a narrow chasm in order to make it to the other side of the mountain.
Strand – A single thread composing a larger item – She had to carefully untangle the strand of hair from the brush.
Finals – A set of examinations given at the end of an academic term – She was nervous about taking her finals next week.
Intersection – A place where two or more roads, paths, lines, or objects come together – We waited at the intersection for the light to turn green.
Re-visualize – To view something in a new way – He tried to re-visualize the problem in order to come up with a solution.
Colors – The visual effect of light wavelengths on the eye – She loved watching the colors change as the sun set.
Pattern – A design or arrangement of repeating elements – The wallpaper had a beautiful pattern of flowers.
Net – A structure made of rope or string woven in a square or diamond shape – He cast his net into the lake and waited for a catch.
Intuition – The ability to understand something instinctively, without the need for conscious reasoning – She had a strong intuition about the outcome of the election.
Algorithmic – Relating to a mathematical process or procedure used to solve a problem – The computer used an algorithmic process to complete the task.
Probability – The likelihood of an event or action taking place – The probability of winning the lottery is very low.
Move – To change the position of something – She moved her furniture around to redecorate her room.
Horizontally – In a line or direction parallel to the horizon – He laid the board horizontally on the ground.
Vertically – In a line or direction perpendicular to the horizon – The rain fell vertically from the sky.
Edge – The line where two surfaces or objects meet – He balanced on the edge of the cliff.
Corner – The point created by the meeting of two lines or surfaces – She put the book in the corner of the room.
Sash – A band of fabric worn around the waist or over the shoulder – She wore a beautiful sash to the party.
Responsibility – The state of being held accountable for something – It was his responsibility to take out the trash.
Share This Lesson:
- Categories: TED Ed, Thinking, Learning, & Solving, Video Lessons
- Keywords: algorithmic, anansi, arachne, aragog, chasm, colors, corner, edge, finals, horizontally, intersection, intuition, move, net, pattern, probability, re-visualize, responsibility, sash, shelob, spider, strand, supremacy, vertically, web, whirled, wide
