# “Hot” coffee cup

**URL:** <https://boards.straightdope.com/t/hot-coffee-cup/996406>\
**Category:** Factual Questions\
**Created:** [January 20, 2024, 7:45pm UTC](https://boards.straightdope.com/t/hot-coffee-cup/996406 "2024-01-20T19:45:03Z")\
**Posts on this page:** 1\
**Showing post:** 69

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**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\
**Post date:** [January 21, 2024, 3:41pm UTC](https://boards.straightdope.com/t/hot-coffee-cup/996406/69 "2024-01-21T15:41:20Z")

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> [@LSLGuy](#):
>
> anti-matter annhilator or whatever

I feel like this deserves more attention.

The heat capacity of water is 4 J/g/K, so if we assume that our insulated container cools by about 1K every 400s, we need an energy input of 10^-2 J/g/s.

If we take the obvious approach of using half anti-water to make our coffee (containment and modulation of the annihilation is left as an exercise for the reader), and noting recent expert commentary that we can probably get 92% efficiency…

[Nuclear fission / fusion? - #45 by Pasta](https://boards.straightdope.com/t/nuclear-fission-fusion/996046/45)

…we have 8 x 10^13 J/g available.

So we can keep our coffee warm for 8 x 10^15 s, or 250 million years as a rough approximation. Of course, the volume of coffee would steadily decrease, which is a drawback to this method.

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