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George Jones

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Everything posted by George Jones

  1. I hove been careful here. Other stuff that we now see will become brighter and less red as we watch over centuries. This is very counterintuitive! As we watch, the universe expands, which seem like it should make all object dimmer and more red, because expansion increases distance and "stretches" light. This other stuff, will become less red, less red, ...., more red, more red, more red, ...
  2. Do mean in principle, or in practice? In principle, nothing that we can see now will become invisible to us. In fact, some, but not all, stuff that now is invisible to us will become visible. In practice, some stuff that we see now will become dimmer and dimmer, and more and more redshifted (as Andrew has said).
  3. In an expanding universe, I think that we will now see it lasting (1 second)*(a_now)/(a_then), where a_now is the present scale factor of the universe, a_then is the scale factor of the universe when the 1-second pulse was emitted.
  4. The October issue of Astronomy Magazine, which arrived in the post a few days ago, has an excellent article on the James Webb Space telescope. The article was written by John Mather, who is the senior project scientist for James Webb, and who won the Nobel Prize for work that first observed the variations in the Cosmic Microwave Background (CMB).
  5. I went to high school in the 1970s in a small (pop. 8000) industrial town in Canada, but the high school was first-rate, and many of its teachers were first-rate. I took computer science classes in high school from 1976 to 1978. By today's standards, the circumstances were strange: the programming language used was Fortran (in high school!); the programs (penciled-in computer cards) were physically sent by Greyhound Bus to a university in another city, and the cards and hard-copy output were returned by bus. The turn-around time was a least 3 days per run, sometimes to find "execution suppressed" because of a syntax error. The teacher, a computer science graduate from the University of Waterloo, had us work on several projects simultaneously, so that we were always sending and receiving stuff. Good courses and teacher.
  6. I keep my NexStar 8 SE on the tripod in my shed, so that I do not have any cool down time. Even though I am 5' 4'' tall, and weigh 130 pounds, I find it easy to carry out the whole unit into the garden. I do have to do an easy star alignment. About 5 minutes after I go out the door of my house, I am observing with my scope at ambient temperature.
  7. Here is a slightly different question: in terms of absolute numbers, has the number of manly visual astronomers gone up or down? Is it possible that, over the past 20 years or so, the number of astronomers of all sorts has gone up, the percentage of mainly visual astronomers has gone down, but the number of mainly visual astronomers has not gone down? I do not have a feel for the answers to these questions, and I am interested in hearing what people think. Personally, I am a purely visual. I have have taken zero pictures using my scope, not even with a mobile held to the eyepiece to capture the moon. This may because I don't own a mobile. My work day consists of doing technical stuff with books, lab equipment, and computers. When i get home, it is a nice change of pace to go out with my scope, and do visual observing while pondering the universe.
  8. I easily do the same, even though I am 61 years old, 5' 4'' tall, and weigh 130 pounds. I keep mine set up in a shed, so I do not have to wait for it to cool down, I do the star alignment, as I don't have Starsense. About 5 minutes after I go out my door, I am aligned and observing.
  9. There are too many books to read. Here are some examples, going form newest to oldest by publication date. "The End of Everything (Astrophysically Speaking)" by Katie Mack https://www.astrokatie.com/book "Our Mathematical Universe: My Quest for the Ultimate Nature of Reality" by Max Tegmark https://en.wikipedia.org/wiki/Our_Mathematical_Universe Going back years, both John Barrow and Paul Davies wrote many interesting books. Example include "The Universe that Discovered Itself" by John Barrow "About Time" by Paul Davies.
  10. Steven Weinberg, who I considered the greatest living physicist, has died. His non-mathematical "The First Three Minutes" is a wonderful account of the evolution of the universe during the first three minutes after the Big Bang, Weinberg also wrote a series of wonderful very advanced advanced books. Some personal thoughts. I twice saw Weinberg give technical talks. Even though I love Weinberg's advanced books, I say the following. I am glad that: 1) they are on my shelf; 2) I am not taking a course that uses any of them as the text; 3) I am not teaching a course that uses any of them as the text. Weinberg explains (at a technical level) some things better than anyone. Sometimes I read a passage in Weinberg, and I think to myself "Wow, I finally understand what is really going on." There are, however, passages in Weinberg's books that I find difficult to understand. Also, sometimes it is difficult to see past the clutter of Weinberg's notation. The lecture notes for a course that Weinberg taught in 2017 (at the age of 84!) were turned into his second to last book, Lectures on Astrophysics. The section on white dwarfs and neutron stars helped me when I had to scramble to prepare an upper-level COVID-related and unexpected teaching overload last fall. I like the personal aspect of the final paragraph of the Preface,
  11. The way I like to put it: when we look at galaxies through our telescopes, we are looking at quantum fluctuations blown up to galactic proportions by the expansion of the universe! Mind blowing!
  12. Pieter van Dokkum, the lead author of the research explained at this link, takes this as evidence for dark matter and against MOND (MOdified Newtonian Dynamics). From the link From the Introduction section of the actual 2021 research paper, and, from the paper's Conclusion,
  13. A report on a Zoom talk about dark matter research that I "attended" last fall:
  14. And before it was a solid state universe, it was a valve universe.
  15. Entangled particles cannot be used to transmit information faster than the speed of light.
  16. I had great fun giving the talk (wife: "Don't get him started on physics!"), and people asked great questions. I hope soon to elaborate a bit on some of my answers.
  17. And my students do just this. I teach a second-year e&m lab course that performs one experiment per week. In consecutive weeks, the students measure ϵo and µo using https://media.vwr.com/interactive/p...h_2014/files/assets/basic-html/index.html#289 and then compare to the speed of light. For µo , we send up to 20 amps through the metal rods.
  18. Welcome to SGL. My in-laws live north of Toronto, near Canada's Wonderland.
  19. I just came in, and the last thing at which I looked was the Blue Snowball. I am sure that my 60-year-old eyes can see some tint in the image produced by my 8 inch SCT.
  20. Yes, these guys are outside our Local Group. They're being whisked away from us at about 700 kilometres (430 miles) per second by the expansion of the universe. Mind-boggling stuff!
  21. Nice. A favourite of mine at the eyepiece.
  22. Nothing relaxes me as much as my observing sessions do.
  23. Years ago, while teaching an astronomy course to about 120 university students and talking about the light-gathering power of telescopes, I said "To some extent, it's not the length that matters, it's the width." The class broke into loud laughter. Ever since, I have been careful not to phrase it like this.
  24. In the months leading up to COVID, I gave a couple of public talks on gravitational waves. I don't know if a non-maths talk on what's below would be interesting or appropriate. Gravitational Waves and Gravitational Wave Astronomy Gravitational waves, first observed in 2015, are produced when compact objects like black holes and neutron stars merge. Just as useful information can be extracted from light wave signals, useful information also can be extracted from gravitational wave signals.
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