Questions from an astronomy hobbyist

After watching the excellent BBC series The Planets, I realized that I know little to nothing about how we actually get rockets off the ground and into space in order for them to explore our solar system. That is probably the case for most people; they're content just to watch the marvel of space travel without understanding it. And I agree--it is wondrous to watch rockets take off, escape the pull of gravity, move into orbit around the earth, and even to watch booster rockets return to their launch pads as was the case with one of the SpaceX missions in 2019 (https://youtu.be/HVqWEoyiaBA). I haven't experienced the need to understand some of what is actually going on, until now. Because I have so many questions; you can't watch programs like The Planets and not have questions. For example, why are planets round in shape, rather than rectangular or octagonal? The answer is gravity. If you want the full answer, google this question and read some of the links that are returned. As it turns out, gravity is the answer to many of the questions about what has gone on and what goes on in the solar system--e.g. the formation of the planets. So what is gravity? My husband smiles when I ask this question; he studied biophysics in college and has a good background in math and physics. There is no simple answer. He reminds me that astronomers and scientists have been studying gravity forever, and will probably still be studying it a century from now. As Wikipedia states:
Attempts to develop a theory of gravity consistent with quantum mechanics, a quantum gravity theory, which would allow gravity to be united in a common mathematical framework (a theory of everything) with the other three fundamental interactions of physics, are a current area of research. 

So, for those of you who understand much more than I do in this field, you'll have to pardon my ignorance. These are my questions listed below, and I'm well on my way to reading about each of them, albeit, reading the articles about them written for lay people. My understanding of the complicated math and physics necessary to understand all of this ended when I was in my second year of college (I hit the math wall when we began to study the derivatives of trigonometric functions). So my interest in astronomy and cosmology is purely that of a hobbyist.

• What are the different kinds of rockets?
• What powers a booster rocket?
• What powers main engine rockets?
• Where are booster and main rockets manufactured?
• Where is the fuel manufactured?
• There is solid fuel and liquid fuel--which ones are used in the different types of rockets?
• Why are nuclear reactors not used to power rockets?
• What keeps rockets going in deep space; why don't they use up their fuel quickly?
• Why do spaceships go into orbit? To save fuel? 
• How did the SpaceX booster rockets manage to get back to earth? Most of the time the booster rockets end up in the oceans and are retrieved by ships for reuse at future launches.
• What is a gravitational slingshot (gravity assist)?
• What is tidal force? (this played a huge role in the formation of the planets)

These are just some of the questions I have, and am currently exploring online in order to find answers that I can understand as a layperson. NASA itself has a very good website that provides a lot of useful information: https://www.nasa.gov/ , and there are other very good websites for astronomy hobbysists as well. 

After seeing the movie Interstellar in 2014, my interest in our universe really took off, if for no other reason than that I wanted to understand some of the concepts brought up in that movie (tesseracts, for example). I bought the book The Science of Interstellar, written by Kip Thorne, and read it carefully. But prior to that, my interest was already piqued by many of the astronomy lectures sponsored by the University of Oslo's Science Library when I worked there as a consultant from 2010 to 2013. There was and is a healthy interest in astronomy and cosmology on this campus, and it was reflected in the choice of invited speakers. And if I think back even further, to when I was a pre-teenager and a teenager, I was already interested in science fiction, reading authors like Ray Bradbury, Madeleine L' Engle, Isaac Asimov, C.S. Lewis, Ira Levin, and others. So the table was set many years ago. At least I know how I am going to use some of my time when I retire; I plan on visiting Cape Canaveral in Florida again (this time I'll appreciate it more), as well as at least one of the astronomical observatories in the USA as well as one here in Norway (not far from Oslo). As one of my former university professors wrote to me recently, 'you'll definitely have no problem keeping yourself intellectually occupied'. I think he's right.

My new interest in one of the oldest sciences--astronomy

My post today will be about astronomy. It is one of the oldest sciences, dating back to some of the earliest world civilizations. This natural science is a study of celestial objects such as stars, galaxies, planets, moons, asteroids, comets and nebulae, as well as of the physics, chemistry and evolution that help to explain their existence (modified from Wikipedia). I am not sure when my interest in astronomy really took hold, but it has developed and grown during the past year, and reached the point where I decided I wanted to buy a telescope so that I could begin to gaze at the sky. Lucky me--my husband decided to make that purchase my Christmas present. So I am now the happy owner of a Skywatcher BK 705 AZ3 Telescope. It is a great telescope for beginners; you can gain more information about it by watching this excellent video: https://www.youtube.com/watch?v=q0YK9968ubY. This telescope costs about three hundred dollars, and allows camera attachment so that photos can be taken if desired. In order to get good camera focus though, you will need to purchase an adapter and an attachment ring, which I have now done. I am waiting for clear skies again in order to take some photos of the moon. Because this telescope has already provided excellent viewing of the full moon this past week; you can see the craters and the lunar landscape. Very cool! We have also managed to view Jupiter with two of its moons (most likely Ganymedes and Europa), but not with great resolution since this planet is quite far from earth and the moons were really just pricks of light; when the two planets are at their closest point, the distance to Jupiter is 365,000,000 miles. The distance between the moon and earth is 225,623 miles at the moon’s closest approach. My husband, who studied physics before moving into biology, has provided me with the mathematical formula to calculate the angular resolution needed to see the moon. It stands to reason that since the moon is closer to the earth than Jupiter, the resolution is better for the moon than for Jupiter. I will eventually take some photos of both and post them here, so you will see what I mean. I would need a much more powerful telescope to get high-resolution views of Jupiter, and it would cost a small fortune.

Interestingly, but perhaps not unexpectedly, there is suddenly a plethora of programs and news articles about astronomy, the planets and moons, space travel, the current space missions—all of which I find so interesting and timely. Here are some links to some great programs and sites if you are interested in finding out more about the ‘wonders of the universe’:

• Wonders of the Solar System TV series from 2010 with professor Brian Cox: http://en.wikipedia.org/wiki/Wonders_of_the_Solar_System   (excellent series—I cannot recommend it highly enough)
• AstroViewer: http://www.astroviewer.com/index.php   
• Universe Today website: http://www.universetoday.com/
•  NASA’s website: http://www.nasa.gov/    (excellent website)
•  SkyWatcher telescopes: http://www.skywatcher.com/products.php?cat=1