I was visiting MIT last week and was lucky to receive two “dark matter boxes” from the MIT Physics department:

Tonight we finally had some time to sit down and talk about them. It was a fun conversation about both math and physics.

We started by just talking about what the boys saw written on the boxes and about what some of the terms met. At the end of this part of the conversation my older son asked a really great question!

So, at the end of the last video my older son wondered why the box said that the universe was made up of 23% dark matter if there was only one particle of dark matter in the box. Basically 0% of the box is dark matter – how do you get to 23%?

The boys have some pretty cool ideas as to how to resolve this mystery š

The last thing that we talked about was how to understand the exponent . It turns out that there are (at least) two places in the universe where a number close to appears. First, the mass of the Earth is approximately grams. Second, the diameter of the observable universe is about meters. We use those ideas to try to wrap our heads around .

So, a really fun conversation touching on a bunch of fun topics. I’m happy that my son wondered about how one particle per box led to 23% of the universe being dark matter – that was a really fun surprise. Happy, too, to have found a few ways to talk about – you don’t see that number too often!

Thanks to MIT’s Physics department for the boxes – look for my younger son’s dark matter store coming soon š