In the Minecraft Wiki entry for pistons, under the heading "Pushing Blocks", it says the following:

Some blocks cannot be pushed by Pistons and the piston head will not extend:

  • Obsidian, Bedrock and Nether Portals to avoid abuse

I can see how pushing Bedrock blocks might be considered bad, because there may be ways to punch holes into the Void or move the bedrock to the surface and build indestructible structures with it. I can also see why Nether Portals shouldn't be pushable, since they are a technical block and should remain within the Nether portal frame.

However, it's not clear to me why pistons shouldn't be allowed to move Obsidian blocks. What sort of "abuse" would be possible if pistons could move obsidian? Were players previously doing bad things with this ability, requiring this limitation to be put in place?

closed as not constructive by GnomeSlice, fredley, Ash, user9983, Invader Skoodge Mar 5 '12 at 16:03

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  • 2
    This question is really borderline. It's kind of a "why did they do it that way anyway?" but it's also actually answerable, unlike most of those. – Invader Skoodge Mar 5 '12 at 15:32
  • @StrixVaria: Yeah, I was worried it may sound too open-ended or unanswerable, but the phrasing of the wiki entry seems to suggest that there's a specific form(s) of abuse possible that this design choice was intended to stop. I just haven't been able to figure out what. – gnovice Mar 5 '12 at 15:37
  • It's because of nether portals. The interaction between moving obsidian blocks and nether portals is probably too difficult to code. As I was writing that up as an answer, I realized that this question is indeed off topic. – Invader Skoodge Mar 5 '12 at 16:03
  • @StrixVaria: I guess I can see your point, but I had thought that the more open development process of Minecraft would make a question like this more answerable than it would be for other games. They provide source code, get feedback from users, and have even had users contribute to the game. As such, I thought that the reasons for certain design choices would be more apparent than they would be for other games, making it possible to give a non-speculative answer to this question. But, I'll defer to the community on this one. – gnovice Mar 5 '12 at 16:14
  • It probably doesn't apply in this case, as most of the community will agree with the 5 close votes, but don't always assume that 5 close votes == the will of the community. – au revoir Mar 5 '12 at 16:41

If your shelter is made out of obsidian is it very hard to destroy (in multiplayer this can be an advantage). If pistons could push it, it would be easier for griefers to destroy your buildings, that is why they are made impossible to push.

Another reason could be that you could use obsidian to build stuff that is not supposed to be build but which do have pushable elements in it. For example a self building house. (cobblestone generator and a hell lot of pistons + redstone clock). If obsidian would be pushable it would be impossible to stop the wave of cobblestone (until its 12 blocks away from the piston of course ;) )

I agree with you, the wiki is a bit vague, but thats wiki :)

  • You said 16 blocks. The limit is 12. Also, furnaces stop pistons. – Timtech Aug 19 '13 at 19:20

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