Hopefully Interesting

I'm a little behind on my blogging but a couple of months ago NASA released some information on their new  Kilopower  small reactor for use in space.  So I thought this would be a good opportunity to write something about power generation in space.  Most satellites and probes in the inner solar system use solar power.  This was one of the first practical uses of solar power back when solar panels were very expensive and now that solar panels have gotten much, much cheaper it's even more of a good idea.  The solar panels on your roof are built tough and will weigh about 10 kg for every square meter or, on the Earth.  At 1300 watts of sunlight coming in times an optimistic 20% efficiency for typical solar cells you've got 26 watts per kilogram.  According to Wikipedia more expensive spacecraft-grade solar panels will give you 77 watts per kilogram, but even then the majority of the expense is going to be lifting the weight of the panel into orbit...

There are a lot of countries in the world with declining populations.  Historically this isn't unusual if there's famine or disease or war causing it but in the developed world this is mostly just people choosing to have fewer children.  In Japan it's all the way down to 1.46 children per woman which, since half of kids are male, means that every generation will tend to be three quarters as large as the one before it. There are a lot of reasons for this.  People having better options than they did in the past seems like the biggest one.  There are differences within the industrialized world in many ways involving religion ,  attitudes towards child care , and other thing. But those are societal factors and there are also individual factors at play in a couple's decision to have kids.  People have different personalities and personality seems to have an effect on child bearing just like you'd expect.  Here's a study I recently saw linked on twitter...