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Help/Advice requested.

Some people I am working with want to set up a "chat app". Currently I don't use one, but others with whom I would like to "chat" are already using Signal, so that seems to be the obvious choice.

So far so good.

But one person who I would like to be in the new group says that he hasn't been able to get Signal to work.

Apparently Signal claims it wants/needs to send an SMS, but can't.

As yet I have no other information, but does that sound familiar to anyone?


Although it was a week ago, I've just learned of the death of the fabulous David Warner. Have a look at his "filmography" and see how many times you've seen him on screen:

Hello! My name is Colin and I am a mathematician.

Today is former England footballer Karen Carney's birthday. I imagine she's having a good day today. How can I help you have a good day?

Seen on the blue site, and thought people here might be able to assist:

"Latex query: I want the Universal Quantifier $\forall$ to look exactly like an upsidedown A... but it doesn't. It looks fainter (different font?). Ideas? Thanks."



It is difficult to get someone to understand something when their salary depends upon their not understanding it. -- Upton Sinclair

So: when you see theorems first read the statements, wrap your mind around them and see why all the hypotheses are needed. But if you want to get good at proving stuff, try to prove them! If you get stuck, read the proofs and learn the methods. Build your skills.

(9/n, n = 9)

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Hardcore math tweet: the importance of knowing lots of small facts.

Working with Todd Trimble on category theory I'm both impressed and also annoyed by how often he can prove things I merely conjecture. Annoyed at myself, that is: why can't I do it?


Can someone tell me the main advantages of gopher versus www ?

Procaffinating: To delay or postpone action; put off doing something until you've had coffee.

Here's a good article by Ehrlich with a lot more detail, and other characterizations of the surreal numbers:

It seems people working on them use NBG set theory to work with proper classes. Someone should redo this work using universes!

(5/n, n = 5)

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Namely, the surreal numbers can be defined by a universal property! For starters, they're an ordered field that's not a set, but a proper class. They contain any ordered field that's a mere set. And the universal property is explained here:


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@feditips that's the most ridiculous complaint. Do what you feel is best.

If they feel that strongly about it, your account isn't for them and they can unfollow it.

Carry on with your good work. You're great.

Indeed, the number of atoms in a gram of hydrogen is about 6 × 10²³. (You may have heard of Avogadro's number - this is roughly that.)

So Boltzmann's constant gives a hint that matter is made of atoms - and even better, a nice rough estimate of how many per gram!

(7/n, n = 7)

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So, does anyone know of any infosec conferences in June 2023?

I would like to avoid sceduling issues....

(Please boost for reach.....)

If you have a friend you trust, visit him often, because shrubs and tall grass grow on the road unwalked. -- Attributed to the Norse god Odin in his proverbs and councils in Håvamål

I only say this because I'm reading a (journal!) paper with silly mistakes in it early on, and can't help but wonder what else is wrong with the paper.

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"Brown M&M test" for academic reviewing: put a silly mistake somewhere early in the paper, and if the reviewers don't catch it then you know they aren't going to catch more subtle, serious mistakes.

In about half an hour, UK pass, starting at 22:17:24, duration 191 secs, visible, Magnitude -1.3

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