 This week I'm talking about the baby universe! It's so cute! I just want to couple it. Its full name is the Cosmic Microwave Background, if you must know. It's adorable and a little bit lumpy. It's when the universe was only around 380,000 years old or so and considering the universe is 13.8 billion years old, these are definitely adorable baby pictures. The Cosmic Microwave Background is the furthest back we can explore using light and all those tiny little fluctuations in color that you see actually correspond to tiny fluctuations in temperature in the early universe. Like many baby pictures that were taken in the 90s, we started off with disposable Kodak cameras and Polaroids. Similarly, the very first few baby pictures of our universe were taken using some low-res versions of cameras before we were able to upgrade to high-res versions. Only that when we were taking our early baby pictures of the early universe, we weren't using Kodaks or Polaroids. We were actually using space probes, starting with Kobe back in 1989, WMap in 2001, and Plank in 2009. Each successive space probe gave us a better and better image of what our baby universe looked like and looking through the images from Kobe to WMap to Plank, it's absolutely beautiful to actually study the sort of lumpiness of our universe and all those tiny little fluctuations that take place. Notably, WMap and Plank were closer to tricorders than cameras and they were able to take a census of all the energy and matter in our entire universe, which scientists have now used to produce some pretty ugly-looking pie charts that explain what the universe is made up of. These baby pictures of the universe tell us a lot about what could have happened before the pictures were taken and also what has happened since the pictures have been taken. But how has babby formed? Before this babby, I'm sorry, baby picture of the universe was taken, the universe was very hot and dense, it was a hot plasma of protons and neutrons and electrons and photons. It was a bit like an opaque fog, not unlike San Francisco at the moment. This was a super tense baby of a universe. The photons in the early universe must have been a little bit depressed because they couldn't travel very far without running into an electron. Thankfully, with a bit of time, the universe took a chill pill and cooled down to 2700 degrees Celsius, which allowed the electrons to actually pair up with the protons and create hydrogen, which then further allowed the photons to party throughout the entire universe without bumping into electrons as much, which also made the universe change from being opaque to being transparent. When these photons were finally free to travel around the universe unrestricted, that's when we were able to take this baby picture of the universe. Because the universe is now very old, it's 13.8 billion years old and much of the light since then has redshifted due to the expansion of the universe. We can only see this light in microwave. This is not the thing that helps you get linguazines every weekend, although that too, like yourself, is made of star stuff. But this is the thing that actually sits in the electromagnetic spectrum between infrared and radio. That's all from me this week. I hope this was a set of baby pictures that you actually enjoyed looking at, unlike all the people who annoy you with them on Facebook. So remember to subscribe on YouTube, donate to the Patreon campaign, and leave a comment.