Our free downloads are not free for Big Picture Science. We use an automatic file delivery service, and its cost more than tripled recently. If you have gotten one of our free downloads, would like to get one in the future, or you just want to support us in providing free files, please consider adding this donation to your shopping cart. It costs $2.00 USD. If you would like to donate more, add more than one donation to your cart. We very much appreciate your support. Donating is completely volunteer – you can get free downloads whether or not you donate.