Thread by @seb_g

1/ Tell Your Kid That Infinity Comes In Different Sizes

#parenting #learnmath #mathtwitter

Your kid probably knows infinity as the “largest number ever”.

Get ready to blow their mind - there are actually different sizes of infinity.

2/ If infinity is a number greater than any assignable quantity or countable number, how can there be different sizes?

Let's work through an example:

3/ Step 1: Ask them to imagine that they are going to count dogs and to write down the number of dogs they have

Let them start counting dogs 1, 2, 3, 4, 5... and have them write it down as they go (do a column on a piece of paper).

4/ And then let them keep going for a while. Then ask them how many dogs they would get if they continued counting forever. They'll probably say infinity. And if they don't, you can tell them.

So eventually you get an infinite number of dogs.

5/ Step 2: Then ask them how many paws a dog has

They will probably answer the number 4.

6/ Say "Great!", and then have them write the number of paws two finger widths away from the list of number of dogs. So 1 dog gets 4 paws. And 2 dogs get 8 paws. If they haven't learned to skip count yet, you can help them. Otherwise, let them keep counting.

7/ After you let them go on for a while, ask them how many paws they would get if they continued counting forever. They'll probably say infinity. And if they don't, you can tell them.

Step 3: Finally ask them how many paws an infinite number of dogs will have

8/ They might struggle, so you can gently ask them to draw a line from 1 dog to 4 paws. Then 2 dogs to 8 paws. So on and so forth until they run out of the examples they wrote.

Which is when you ask them if the infinity of paws is bigger or smaller than the infinity of dogs.

9/ They should realize that an infinite amount of dogs will have a bigger infinite amount of paws than the number of dogs.

10/ If not, tell them. Then ask them to come up with a similar example where if you have an infinite amount of something that it could be compared to a smaller or bigger infinite amount.

11/ If you found this entertaining, jump back to the top tweet (see below) and retweet it to help other parents & guardians with math curious kids can share the fun !

12/ Initial tweet:

https://twitter.com/seb_g/status/1512661770736914441