I know you didn't name it. It'd be named the Birthday McBirthday Face if someone on the internet named it.
My beef is with it being called a paradox. A logical thinker wouldn't think that because it'd be illogical. The math itself shows that. The whole premise is that this is logical. It's a thing one might not expect at first blush but makes sense after some thought, but it's not a paradox.
Google def of Paradox: "a seemingly absurd or self-contradictory statement or proposition that when investigated or explained may prove to be well founded or true."
So you may not like it being called a paradox, but based on the definition above, I think it fits.
Out of more than six billion people, we're testing to see if a number of them share a very finite commonality; were more than one of them born on one of 365 days, and it's not even a preference. It's not something we could change our minds about due to external or internal influences. I was born the day my body came out of someone else's body. That's it. It's a done deal. And it's to see if one person will share a birthday with at least one other. It's not to see if two people were born on one specific day, say, 1/1/84. No, it's to see if any day, regardless of year, is shared. The constraints are very loose. That's another reason it works like it does. The whole thing is set up to work like it does. That is not a paradox.
Yes, it is, and I am not sure you truly understand it because you're fixated on six billion people. The number of people has nothing whatsoever to do with it. It's simply this: assuming birthdays are random, how many people would you have to randomly pick before there's more than a 50 percent chance two of them share the same birthday. Population size is not important.
In one sense, it's similar to how a polling firm like Gallup can survey just 2400 people out of a population north of 200 million (excluding children), and produce accurate assessments of what everyone is or does or thinks.
But we don't have to rely on me. There are websites after websites which explain why this is not a paradox.
We'll have to agree to disagree on this one. I think it fits the definition, you don't, let's just RDWHAHB.
That said, it isn't seemingly absurd or self-contradictory to me, but I see a lot of people for whom it is.