# A knotty problem

**URL:** <https://boards.straightdope.com/t/a-knotty-problem/792448>\
**Category:** Factual Questions\
**Created:** [July 30, 2017, 4:59pm UTC](https://boards.straightdope.com/t/a-knotty-problem/792448 "2017-07-30T16:59:01Z")\
**Posts on this page:** 1\
**Page:** 2

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**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\
**Post date:** [August 3, 2017, 12:58pm UTC](https://boards.straightdope.com/t/a-knotty-problem/792448/21 "2017-08-03T12:58:32Z")

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> [@Indistinguishable](#):
>
> . . . and in this way one could prove that any two cardinalities whose sum is zero are themselves zero, but this is obvious on its own terms anyway (if a union of two sets is empty, both the sets were themselves empty, clearly).

[silly time]  
I recently tried to form the union of **Senegoid** and anti- **Senegoid** (kind of like that scene merging good-Kirk and bad-Kirk, with similar motivation) and all I got was the empty set as a result. This assumes that my original “Universal” set consisted of all material stuff, while my result was just a lot of heat and noise. We find, therefore, that the set of all material stuff is not closed under the Union operation.  
[/silly time]

ETA: So. I join the ranks of swindlers now. If only I could make some money off this. 🙂

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