Hi everyone, this is Pamela and I am here to talk to you once again about my favorite sponsor of our show and this is bark box.

We've been super lucky to only get sponsors who are companies that we really love and I love bark box because my dog loves bark box.

For an extra free month of bark box visit barkbox.com slash astro and you'll get your free month when you subscribe to a six or 12 month plan.

I have a 12 month plan. Each month I get a new box that has a few different treats that are all natural.

They're made here in the States and Canada. There's a couple of toys and it's a different theme each month and I never quite know what we're going to get into.

So there was the school box month where there was a pencil and then there was the Thanksgiving box which included a carrot that is my dog's favorite toy.

There's usually a couple of different toys but only one of them becomes his favorite toy and the other great thing about getting these every month is it's my personal reminder to go out, pick up all the rest of the toys that have been scattered in the house and the yard and throw them in the box.

And throw them in the washing machine and he has new dog toys to play with while everything tumbles and dries. So go get your dog a bark box. They have them set up for all different sizes. Pick if you have large medium small.

They even have programs for the destructor dog. So go get yourself a happy dog. Subscribe to bark box. Go to barkbox.com slash astro.

Your dog will love you and you know my dog will love you anyways. Thanks.

Astronomy cast episode 442 Magnetic pole reversal. Welcome to astronomy cast or weekly facts based journey through the cosmos where we help you understand not only what we know but how we know what we know.

My name is Fraser Canem, a publisher of University and with me is Dr. Pamela Gay, the director of technology and citizen science at the astronomical society, the Pacific and the director of cosmocost. Hey Pamela, how you doing?

I'm doing well. How are you doing? Fantastic. Just a big reminder to everybody. Of course the eclipse 2017 August this year. If you're planning on attending, there's a really cool project that you're going to want to get involved in called the Eclipse mega movie.

And it's sort of a collaboration from the astronomical society of the Pacific and Google and Berkeley. I think and they're going to have amateur and professionals photographers across the United States across the eclipse line gather together and take a bunch of pictures and then merge those pictures together into one mega movie that shows the whole eclipse.

So I'm going to be doing it. And there's a lot of cool science that can come out of this from basically depending on where you are, you can see how the light is getting refracted based on do you see Bailey's beads do you see what are the nuances of how you experience the eclipse and we're going to be able to catch that and do that science.

So if you're planning on seeing the eclipse not necessarily with us, but anywhere across the the US when it happens and you think you've got the right gear like a DSLR and reasonable lens, then do a search for eclipse mega movie and you should be able to find the project inside up.

All right. So if you look back into the geologic record of the earth, it appears that our planets magnetic field flips polarity every few hundred thousand years or so. Why does this happen when it's supposed to happen next is dangerous. All right, Pamela set the stage earth magnetic field. Let's start there.

The earth is a big magnet sort of so so magnetic fields are generated by lots of different things and one of the easiest things to make a magnet out of is flowing current. This is an electromagnet we've probably all done this at some point in school where you take wire you wind it around your fingers, you run electricity through it and suddenly you can fling paper clips at one another.

This is what you do with electricity in middle school. Now with the earth you built you build an electromagnetic rail gun. Exactly.

Yeah, this is this is the purpose of science class in middle school build weapons.

So our earth doesn't exactly have wires attached to a battery, but what we do have is molten metal and molten metal has lots of readily flowing electrons. That's a fancy way of saying current and thanks to convection.

This molten metal is is looping through the interior of the planet and this process is we believe generating our earth's magnetic field.

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