Conversations about the largest number

We're at a restaurant waiting for our food. My 9yo is discussing large numbers. 

Sempi: Did you know that googol is 1 followed by 100 zeroes?

Me: Yeah. 

Sempi: And googolplex means 1 raised to the power of googol. 

Me: Technically it is 10 to the power of googol because 1 to the power of anything is just 1. 

Sempi: Ok. (whatever). 

Me: Also Google is named after googol. 

Sempi: I know. 

Me: Google's first office was called Googleplex, named after googolplex. 

Sempi: Oooh. Cool!

Vian (6yo): Is that the biggest number in the universe. 

Yoshi: I read that there aren't googolplex number of atoms in the universe.

Me: Well technically there is a number that is so unimaginably large. It is called Graham's Number.

Sempi and Vian: Oh. How many zeros does it have? 1000? 

Me: No it is so big that you can't even imagine it. (I try reading the wikipedia entry without success)

Me: I can't quite explain it very well because I don't fully understand it myself.

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Next day I'm walking Vian to school. We're doing imaginative "talk play". Vian is describing a generator in Minecraft that can produce something infinitely. 

Vian: It just keeps generating it forever. Actually that's not true, it only goes up to that number that you couldn't explain. 

Me: Graham's number? 

Vian: Yeah, that. 

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I'm so proud that Graham's number is a casual quantity in our household now.