Block of the Week: Observer

Last week, we talked about the weird way that sand can spawn floating in the air during world generation but drop down as soon as you disturb it, causing landslides. The more experienced of you will know that this happens when you change an adjacent block in some way.

That's a pretty handy property, which can be used to make all kinds of interesting creations. Until pretty recently, if you wanted to make your own block update detector then you had to manually set it up using complex redstone mechanisms, but version 1.11 of Minecraft introduced a block that does everything for you. And it just so happens that it's this week's Block of the Week - the Observer!

The observer is placed just like a piston - the direction that it's facing matters. An observer isn't quite omniscient, y'see - it has an arrow on the top that points in the direction of the block that it's observing. That can actually include another observer, so if you set two up pointing at each other then they'll endlessly beep on and off.

We won't go deep into exactly how observers work on a technical level, because you'll glaze over fast (the full information is on the Minecraft wiki if you want some bedtime reading). But you should know that the observer block actually works a little differently between the Java edition of Minecraft and the Bedrock edition that runs on phones, tablets, and Windows 10.

That means that they don't detect exactly the same things. Both will detect a piston extending, and neither will detect a note block being played, but only the Bedrock edition will detect flowers being added to a flowerpot and only the Java edition will detect a potion being added to a brewing stand.

When an observer does detect something, it will emit a strong redstone pulse for two ticks. That can power redstone dust, a comparator, a repeater or anything else you attach to it. They're great for letting you know when your tree farm is growing, or if water is flooding an area, or even if that cake you spent ages gathering the resources for is being eaten.

Want more ideas? We've got them! You could detect a chest being open and closed, a furnace beginning to smelt, the growth of cactus or sugarcane, endermen stealing blocks from your base or the ignition of TNT. You could build a system that notifies you when water freezes or ice melts, or when rails change orientation. You can even get alerted if some nefarious intruder sleeps in your bed - the three bears would have found that one handy.

Those are our ideas - what are yours?