You type “why is the sky blue” and — blink — you get answers from millions of pages.
A search engine does not look at the whole internet when you ask. That would take years! It gets ready long before you type.
🧠 Big idea: Crawl → Index → Rank. Three steps. We'll play with each one.
Step 1: Crawling 🕷️
A crawler (also called a spider or bot) is a program that opens a page, reads it, then follows every link to a new page — over and over, forever.
Tap a glowing page to let the crawler visit it. Follow the links!
Pages crawled: 1 / 5
The crawler starts at Home. Which page can it reach next?
🕸️ Links are the crawler's roads. A page with no link pointing to it is very hard for a search engine to find!
Step 2: Making an index 📇
After crawling, the engine writes down which words appear on which page. That giant list is the index — like the index at the back of a textbook.
This page is about the sky. Tap the 3 important words a search engine should save. Skip the boring joining words.
skyfacts.sg/blue
“The sunlight is scattered by the air, so the sky looks blue.”
📇 THE INDEX
empty…
Pick a word to add it to the index.
⚡ Why an index? Searching 3 saved words is lightning fast. Re-reading the whole internet would take years.
Step 3: You ask a question ❓
What you type is called a query. The engine looks up your words in the index and pulls out every page that matches.
Try it! Type a word like sky, blue, sun or rainbow and press Search.
🔍
The index is waiting for your word.
💡 Notice: the engine never re-reads the web when you press Search. It only checks its index — that's why it answers in under a second.
Step 4: Ranking the results 🏆
Thousands of pages may match. Ranking decides the order. A page climbs higher when it really answers the question, is easy to read, loads fast, and other trusted pages link to it.
Query: “why is the sky blue”. Use ▲ ▼ to put the best answer on top, then tap Check.
Best answer at the top, least useful at the bottom.
🔗 A link is a bit like a vote. If many good pages link to one page, the engine trusts it more.
Step 5: Top result ≠ always true 🧐
A search engine is a clever machine, not a teacher. It guesses what is useful — it cannot promise something is true. So you check too!
Which search would help you find how tall Mount Everest is?
Clear words = better matches in the index.
Two pages both answer your Science question. Which do you trust more?
Ask: who wrote it, and why?
✅ Smart searcher habits: use clear words, open two or three results, and check who wrote it.
The whole journey, in order 🚀
Tap the pipeline to send one question through the machine.
Watch which step happens before you even ask.
🎉 You now know how search engines work!
Next time you search, you'll know exactly what the machine is doing behind the screen.
1Crawl — spider bots follow links from page to page, all day, every day.
2Index — the important words on each page are saved in one giant list.
3Query — your typed words are looked up in that index, not on the whole web.
4Rank — the best, clearest, most trusted pages are put on top.
5You check — clear words, a few results, and look at who wrote it.
🌟 Try this at home: search the same question two different ways — “sky blue” and “why is the sky blue” — and see how the results change. Now you know why!