Sending Secret Messages with Patterns

But here's what's fascinating: different lighthouses use different flashing patterns. One lighthouse might blink twice quickly, while another blinks slowly three times. Sailors learn to read these patterns like a code. Without ever saying a single word, the lighthouse sends a message across miles of dark ocean using only light.

How can a simple light send a message? It's just light turning on and off — how does a pattern of flashes carry information that a sailor can understand?

💭 Thinking Questions

• What do you think makes the lighthouse's flashing pattern useful for sending information?
• Why do you think different lighthouses use different patterns instead of all just staying on?
• Can you think of other times people use patterns of light or sound to communicate a message?

Scientists and engineers have discovered something powerful: patterns can be used to encode and transfer information from one place to another. A pattern is something that repeats or follows a set of rules that someone can recognize. When we agree on what a pattern means, it becomes a way to send a message — even without words.

Think about a traffic light. It doesn't talk to you, but you understand its message because it uses a pattern of colors: red means stop, yellow means slow down, and green means go. Everyone who sees the light agrees on what each color means. That shared understanding is what makes the pattern work as a way to transfer information.

What engineers do: Design solutions for transferring information

Engineers don't just study how things work — they design solutions to real problems. One important engineering practice is figuring out how to send a message from one place to another when people can't talk directly. In this investigation, you'll think like an engineer and design a pattern-based code using a flashlight.

The Challenge: You and a partner are in separate rooms. You each have a flashlight. You need to send a simple message — like a number between 1 and 5 — using only the flashlight. You cannot talk, write, or use any other tool.

Materials you would need:

• 🔦 Two flashlights (one per person)
• 📋 Paper and pencil to design your code
• 👤 A partner in a different part of the room

What you would observe: When both partners agree on the same pattern code beforehand, messages are received correctly. When they use different codes or no code at all, messages get mixed up. The investigation shows that a shared, consistent pattern is essential for transferring information.

In this investigation, you are practicing the Science and Engineering Practice of constructing designed solutions. Engineers look at a problem — "How can I send information across a distance?" — and then design a pattern-based system to solve it. They test it, find problems, and improve the design. This is exactly what real engineers do when they create technologies like traffic lights, fire alarms, and even Wi-Fi signals.

When scientists and engineers study pattern-based information transfer, they find that every successful system has three essential parts: a sender, a signal (the pattern), and a receiver. The sender creates the pattern, the signal travels through space (as light, sound, or another form of energy), and the receiver detects and decodes the pattern.

Let's look at data from a real investigation. Imagine a class of 4th graders tested three different flashlight codes to send the numbers 1 through 5. They recorded how many messages were received correctly out of 10 tries for each code system.

The data clearly shows a pattern in itself: the simpler and more consistent the code, the more accurately the message was received. Code A worked best because it used a very simple, clear rule — each flash means one number. Code B was harder because the receiver had to tell the difference between short and long flashes, which sometimes got confusing. Code C barely worked at all because there was no shared pattern.

This tells us something important about how information transfers work. The code doesn't need to be fancy — it needs to be clear, consistent, and agreed upon by both the sender and the receiver. When a pattern follows strict rules, the receiver can decode it. When a pattern is unclear or changes without warning, the message gets lost.

This is why Morse code was so successful for over 150 years. The system was standardized — everyone around the world learned the same code. A dot-dash-dot always meant the letter "R," whether you were in America, Europe, or on a ship in the middle of the Pacific Ocean. The pattern was universal, clear, and consistent.

The crosscutting concept in this lesson is Patterns. Scientists look for patterns because patterns help us understand, explain, and predict the world around us. In this lesson, we've seen that patterns can also be used to transfer information. But patterns that carry meaning show up all across science — not just in communication.

Let's look at how the idea of "patterns carry information" appears in different areas of science:

Notice the pattern within the patterns: in every example, a repeating or structured arrangement of signals carries specific information. The details change — sometimes it's light, sometimes sound, sometimes lines on a label — but the underlying idea is the same. A pattern that both the sender and receiver understand can transfer information reliably. Scientists look for this kind of crosscutting connection because it reveals deep principles that work across many different situations.

Engineers design pattern-based communication systems to solve real problems all around us. Let's look at some examples of how people use patterns to transfer important information every single day.

Engineering Design Challenge

Now imagine you are an engineer who needs to solve this problem: Your school needs a way to communicate different messages during an outdoor field day, but it's too noisy for anyone to hear announcements. You need to design a pattern-based system using only colored flags.

Think through the engineering design process:

This is how engineers think about every communication system — they identify the problem, design a pattern-based solution, test it with real users, and improve it based on what they learn. The best solutions are simple, clear, and easy for everyone to understand.