ActivityPub Viewer

A small tool to view real-world ActivityPub objects as JSON! Enter a URL or username from Mastodon or a similar service below, and we'll send a request with the right Accept header to the server to view the underlying object.

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{ "@context": [ "https://www.w3.org/ns/activitystreams", { "ostatus": "http://ostatus.org#", "atomUri": "ostatus:atomUri", "inReplyToAtomUri": "ostatus:inReplyToAtomUri", "conversation": "ostatus:conversation", "sensitive": "as:sensitive", "toot": "http://joinmastodon.org/ns#", "votersCount": "toot:votersCount", "Hashtag": "as:Hashtag" } ], "id": "https://fediphilosophy.org/users/kinozhao/statuses/113125319168618589", "type": "Note", "summary": null, "inReplyTo": null, "published": "2024-09-12T15:36:22Z", "url": "https://fediphilosophy.org/@kinozhao/113125319168618589", "attributedTo": "https://fediphilosophy.org/users/kinozhao", "to": [ "https://www.w3.org/ns/activitystreams#Public" ], "cc": [ "https://fediphilosophy.org/users/kinozhao/followers" ], "sensitive": false, "atomUri": "https://fediphilosophy.org/users/kinozhao/statuses/113125319168618589", "inReplyToAtomUri": null, "conversation": "tag:fediphilosophy.org,2024-09-12:objectId=5330724:objectType=Conversation", "content": "<p>A very niche question on <a href=\"https://fediphilosophy.org/tags/computability\" class=\"mention hashtag\" rel=\"tag\">#<span>computability</span></a> theory that I couldn&#39;t find the answer to. On the off chance that someone has a lead:</p><p>In Turing&#39;s 1936 paper he gave a construction of Turing machines, a proof that they are enumerable, and two proofs of the halting problem. When we talk about TMs now we typically talk about TMs that halt (ends with a halting symbol) or does not halt. Turing didn&#39;t have a halting symbol. Instead he distinguishes circular (machines that print only finitely many symbols) and circle-free (otherwise) machines. They are basically the same and play the same roles in the halting problem proof.</p><p>Here&#39;s the thing: Turing&#39;s circular machines correspond to non-halting machines and circle-free machines (ones that go on to print infinitely many symbols) correspond to halting machines. I have a very hard time seeing how this works. Any idea? pointers to secondary sources?</p><p>It all happened in the span of 3 pages which I&#39;ve read 10 times already :(</p>", "contentMap": { "en": "<p>A very niche question on <a href=\"https://fediphilosophy.org/tags/computability\" class=\"mention hashtag\" rel=\"tag\">#<span>computability</span></a> theory that I couldn&#39;t find the answer to. On the off chance that someone has a lead:</p><p>In Turing&#39;s 1936 paper he gave a construction of Turing machines, a proof that they are enumerable, and two proofs of the halting problem. When we talk about TMs now we typically talk about TMs that halt (ends with a halting symbol) or does not halt. Turing didn&#39;t have a halting symbol. Instead he distinguishes circular (machines that print only finitely many symbols) and circle-free (otherwise) machines. They are basically the same and play the same roles in the halting problem proof.</p><p>Here&#39;s the thing: Turing&#39;s circular machines correspond to non-halting machines and circle-free machines (ones that go on to print infinitely many symbols) correspond to halting machines. I have a very hard time seeing how this works. Any idea? pointers to secondary sources?</p><p>It all happened in the span of 3 pages which I&#39;ve read 10 times already :(</p>" }, "attachment": [], "tag": [ { "type": "Hashtag", "href": "https://fediphilosophy.org/tags/computability", "name": "#computability" } ], "replies": { "id": "https://fediphilosophy.org/users/kinozhao/statuses/113125319168618589/replies", "type": "Collection", "first": { "type": "CollectionPage", "next": "https://fediphilosophy.org/users/kinozhao/statuses/113125319168618589/replies?only_other_accounts=true&page=true", "partOf": "https://fediphilosophy.org/users/kinozhao/statuses/113125319168618589/replies", "items": [] } } }