I do not recall the beginning of this conversation, but I do recall that we were eating pizza at the dinner table when Tabitha anticipated my turn in the dicussion.

Tabitha(6 years old): I know what you’re going to say, Daddy. “Counting never ends.”

Me:I suppose that sounds like something I would say, yes.

T: What’s the biggest number, though? Googolplex?

Quick tutorial. A “googol”—spelled that way—refers to this number: , or “a one followed by a hundred zeroes”.

It is, of course, a very big number. Far too big to be practical in any meaningful sense. The very *idea* of such a large number having a name is fascinating to children. Most children (in my experience) encounter *one googol* in their social interactions with other children. The *googol* does not appear in the Common Core State Standards.

A “googolplex” is , or or “a one followed by a googol zeroes”. You cannot write this number out in standard form.

You may Google *googol* for lots of interesting characterizations of how extremely silly this very large number is.

For example, you will not live for *one googol *seconds.

Indeed, the universe has not existed for *one googol* seconds (not even by the greatest estimates of its age—not even close).

You get the idea.

Me:Well, like you said I would say,counting never ends,so no googolplex is not the biggest number.

T: If you counted by 10,000 could you ever get to googolplex in your life?

Me:No.

T: If you counted by 11,000?

Me:No.

T: 12,000? 13,000?

Me:No. Even if you counted by googol, you couldn’t get to googolplex in your lifetime.

T: Well, what if you counted by googolplex?

Me:Well sure. It would the start of your count, wouldn’t it?

She decides to demonstrate this (Side note, we have been *counting by* various numbers of late).

T: Googolplex.

She smiles broadly, congratulating herself for successfully counting to what she has perceived to be the largest number.

We discuss further the existence of a largest number. Then Tabitha makes a claim that takes us in a different direction.

T: Eventually, numbers just go back to the beginning.

Me:So if you keep counting, you get to zero?

T: No.

Me:One?

T: No, Daddy! Don’t you remember there are numbers before zero?

# So what do we learn?

Big numbers are fun. Boy howdy are big numbers fun. Children love to talk about the biggest number, and whether one exists. There is all kinds of lovely thinking going on when they ask these kinds of questions.

Talking about big numbers often leads to talking about infinity. If there is no biggest number, it is because numbers go on forever. The only thing Tabitha has experience with that goes on forever is a loop. She drew on that loop metaphor in imagining that numbers go back to the beginning eventually.

# Starting the conversation

Listen for the *biggest number* talk. It often surfaces when children are comparing their athletic prowess (*I can jump 2 sidewalk squares!* *I can jump 100 sidewalk squares!* Pretty soon, someone is claiming to be able to jump *googol *or *infinity *sidewalk squares.)

When it surfaces, support it. Play and explore with your child. Answer questions. Ask questions. Talk about it and have fun. Look stuff up together when the questions go past your own knowledge. Shoot me a question here at Talking Math with Your Kids if I can answer any of those for you.

Sydney is the same age as Tabitha. One night, we talked about how numbers go on for infinity. The look of awe and how Syd’s eyes bugged out of her skull, I was utterly delighted. It was that look of fascination that got me excited.

The boys talk about ‘a billion one hundred’ all the time – looking forward to chatting more with them about this, next time it comes up. Thanks.

Wait, numbers don’t wrap around? They do in computer science! For an illustration, see: http://www.csi.ucd.ie/staff/jcarthy/home/CourseNotes/Web%20Info%20Representation_files/image006.gif

You might be amused by this skit from Mr. Show about the biggest number

My ten year old son is fascinated (and has been for a while) by the ideas of the number googol and googolplex. He also had a silly counting routine when he wanted to cheat at hide and seek. For example, if he was to count to 30 he’d say ‘ one, two, skip a few, now I am at thirty!’

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