 Greetings and welcome to the Introduction to Astronomy. In this week's Exploration of the Solar System, we are going to talk about the Sputnik satellites, the first satellites to be put into space. Now, while this may not really be directly exploring the solar system, this is the beginning of the space age, and the beginning of the study of the universe from space. So let's look at the two Sputnik spacecraft, and Sputnik 1 was the very first craft to be launched and to attain Earth orbit. It was launched on October 4th of 1957, and we see a replica of it here in a museum. And it is really just a 22-inch aluminum sphere, very small object, that orbited Earth only for about three months. It was in a very low orbit, much like our International Space Station is currently, and that is about a 96-minute orbit. Well, our International Space Station takes about that long to orbit Earth as well. Now, being in a low-Earth orbit, it didn't last very long. It only orbited for about three months, and then returned to Earth. Now this was not a scheduled return, what happened is it got too close to Earth's atmosphere, and the drag on the spacecraft eventually pulled it down, and it burned up in the atmosphere on its way back to Earth. So that, but it was very important because this was the first satellite, and the beginnings of all of the other study that we will look at over coming lectures. Now not that much later, in fact just a month later was Sputnik 2. Now Sputnik 2 launched in November of 1957 and actually carried the first passenger into space, not a human, but Leica. The dog pictured on the stamp here commemorating the travel into space, the first living organism to travel into space. And that the Leica only survived about four orbits, unfortunately, and in fact there never was a way to really bring the dog back down to Earth, and in fact the plan had the dog survived longer, would have been to give it poisoned food to save it from burning up in re-entry and dying there when the craft came back to Earth. So that wasn't needed, unfortunately, due to other malfunctions in the system. The dog did not survive more than just a few orbits, but it did give us clearly some of the very first information of how a living organism would really be affected by the weightlessness in space, so monitoring the vital signs of Leica would really help us understand perhaps how humans might adapt to space in the coming years and as launches would come and actually bring humans into space just a few years after this. So again, let's take a look at our summary, and really Sputnik, again, is not an exploration of the solar system directly, but it is the start of the space age and of the exploration of space by craft. We looked at Sputnik 1, which was the first artificial satellite launched into space and orbited Earth for just a few months, and then Sputnik 2, which launched the first living creature into space. And as we continue on, we will concentrate more on the craft that actually explored objects like our moon and the planets over the coming lectures. So that concludes this lecture on Sputnik. We'll be back again next time for more exploration of the solar system. So until then, have a great day, everyone, and I will see you in class.