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George Jones

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Everything posted by George Jones

  1. I agree., and over the next 10 years or so, we will accumulate a lot more data from the LHC, from experiments that attempt direct detection of dark matter, and from other observations. If, at the end of 10 years, we are still in a dark matter muddle, I think we will be in crisis mode. Other physicist would disagree, and would echo SuperTramp. Crisis? What Crisis? Experimental data has already killed off substantial portions of "theory space" for dark matter. Theory space, however, is an expanding universe.
  2. I meant to get to this earlier, but I have been doing a COVID-related overload, and things have been somewhat hectic. The talk included theoretical results of the paper to which I linked in my previous post. The authors of the paper take the view that gravity is okay, and that new unseen and transparent dark matter is needed to account for the motions of stars in galaxies, and galaxies in clusters of galaxies. Observations of the relative abundances of primordial elements, and of the Cosmic Microwave Background (CMB), indicate that dark matter is not made of the particles that account for normal matter's mass, protons and neutrons. To date, we only have evidence that dark matter interacts via gravity, but many physicist think/hope that dark matter interacts via other (quantum) forces. They think that dark matter has quantum interactions, because this would give scenarios for dark matter production in the early universe similar to the production of normal matter, e.g., matter antimatter annihilation/creation that continues until the universe expands enough to stop these processes. Physicists hope that dark matter interacts with normal matter, as this gives ways for experimentally seeing signatures of dark matter. If there are other interactions (besides gravity) involving dark matter interactions, they could be between: 1) dark matter and dark matter (just as there are interactions between normal matter and normal matter), and/or 2) dark matter and normal matter. The very interesting talk was about theoretical models that have both 1) and 2), where 1) is used to generate the masses of dark matter particles, and 2) is used to predict observable effects of the models. Two scenarios were considered for generation dark matter mass. One was a possible a dark electromagnetic-like interaction between dark matter and dark matter. The analogy is not exact, as, unlike normal photons, the dark photons have mass that they acquire from a proposed dark Higgs-like particle. Another possibility is that there is a dark colour-like force. In the normal colour nucleon force, gluons carry the colour force, and thus gluons can interact with gluons. In the proposed dark colour-like interactions, dark gluons interact to form massive dark glueballls. In both types of models, it is proposed that there is a "feeble" interaction between dark matter and normal matter. This feeble interaction can inject energy into the normal universe. If his injection is early enough, it can affect the relative primordial abundances of elements. If this energy injection is later, it can affect the the thermal spectrum of the CMB. If this injection is later still, it can affect the anisotropy spectrum of the CMB. High precision cosmological measurements could reveal these effects. Possible results for the LHC and for high precision cosmological measurements probe complementary interaction strengths. The cosmological results are for weaker interactions.
  3. My earliest memory of students taking pictures with mobiles is from 2006. I was teaching an electronics lab then, and students used their mobiles to take pictures of oscilloscope traces that they needed for their lab reports.
  4. The speaker is one of the authors of the recent paper https://arxiv.org/abs/2003.02273 so I suspect the talk will be an upper-level undergrad version of this. He might not mention the LHC.
  5. Today, at 1 pm local (9 pm BT), I will attend the following Zoom talk. Normally, the talk would be in-person, and I and other folks would get to talk with the speaker over a meal. Because of COVID, the talk is virtual. "Title: Searching for Dark Forces in the Cosmos Abstract: New fundamental forces can play a crucial role in models of dark matter and they are predicted by many theories of particle physics beyond the Standard Model. Such new forces are said to be "dark" if they interact only very weakly with ordinary matter. They could take many forms, with specific examples being similar to the electromagnetic or strong forces, and in some cases they can even be the source of dark matter themselves. In this talk I will describe how such forces might arise and what they can do in the early universe. In particular, I will show how detailed measurements of primordial element abundances and the cosmic microwave background radiation can be used to search for them."
  6. About four or five years ago, my daughter made a drawing of some Harry Potter characters in the bottom right corner of the board of my office. This is the only thing that doesn't get erased.
  7. Bins in the house, NexStar 8SE on tripod in the shed.
  8. Welcome to SGL. I grew up a couple of hours from Toronto. Because of COVID, I didn't make it to Toronto this summer.
  9. Welcome to a great forum. I do strictly visual, usually in the centre of Prince George BC. I last visited Calgary in summer 2019 when my family and another family camped near Banff.
  10. I recommend some type of 10x50s. These are good general purpose bins (astronomy and daytime uses). I have 10x50s and 15x70s.
  11. I have a NexStar 8SE, and for some time I have been considering getting a CPC 1100. I would dearly love to have a CPC 1100, (I would also keep my NexStar), but I am somewhat worried about the weight of the OTA/mount. My specs: I will be 60 next month; I am 5' 5'' tall; I weigh 130 pounds; I am in good physical condition, and I don't mind lugging somewhat heavy stuff. Thoughts? Thanks.
  12. These are the original boxes for my NexStar 8SE, which I got in the fall of 2009. Two years later, I used these boxes when I made a big move from one side of Canada to the other, 4100 kilometres (2500 miles) as the crow flies. Four years after that, I used them again when I made a small move from our flat to our current house, 3.4 kilometres (2.1 miles).
  13. I teach physics (labs and lectures) and astronomy (lectures), and I mentor (post)grad students who make money teaching physics labs. I love all of this, so I pretty much have my dream job.
  14. I meant something more fundamental. Suppose Mike lives in the northern hemisphere between the Tropic of Cancer and the equator (as I did for two years). Where does Mike see the Sun on a date that is near June 20th, and at a time that is near local noon?
  15. As expected the (tremendously!) helpful folks here at SGL have posted a slew of reasons.
  16. It was clear all day yesterday, and the forecast was for mainly clear all night, so, at 11:00 pm, I set up scope for a visual session with Jupiter and Saturn before bed. By the time I was ready to align the scope, the sky was mainly cloudy, and Jupiter was not visible. i came inside to read, while periodically sticking my head outside to check on the situation. Things did not improve, so at 12:15, I decided to take down and put away the scope. When I finished, I came in through my back deck door, noticed my 10x50s sitting by the door, and thought "I should take these into back garden and see if there is a break in the clouds to the north." There was! I easily spotted Capella, looked left, and immediately saw NEOWISE with my naked eyes from a city of 80000. This was first sighting of NEOWISE, as I've had clouds, clouds, clouds. Put my bins up, and was floored by the sight! I went back inside to get collect my 15x70s and my wife, who was still up in her home office. NEOWISE was spectacular in my 15x70s. My wife saw the comet with her eyes, and with the 10x50s, but she had no interest in trying the 15x70s, If it is clear tonight, I will get my 13-year-old daughter up to have a look. Awesome!!!
  17. I love comets, but I have had days and days and days of early morning clouds, so I am none the Wiser as to what NEOWISE actually looks like. Also, I had hoped to see a shadow transit of Ganymede last night. It was mainly clear an hour before it started, but then the clouds rolled in.
  18. If you have time on your hands, you could wait for 120 million years. Then, the baseline, the diameter of the Sun's obit about the centre of our galaxy (about 60000 light-years), could be used for parallax measurements of distances to far away galaxies. I have been lazy, and I have not calculated if effects of the expansion of the universe would be noticeable with this method.
  19. I like theoretical physics, but I completely agree with In another thread, I wrote
  20. Any attempt at total understanding of this will necessarily be incomplete.
  21. Meaning you want us to recommend books that will put you to sleep? A couple of books that I like for bedtime reading are "Universe: the Definitive Visual Guide" (Marin Rees is editor), and "The Story of Astronomy: From Babylonian Stargazers to the Search for the Big Bang" by Peter Aughton. I find that I can open them at random and start reading. Liking a book, however, is a very personal thing.
  22. I was only nine, but I remember when this happened. A few days ago, I pulled out my copy of he Haynes "Apollo 13 Owners' Workshop Manual An engineering insight into how NASA saved the crew of the crippled Moon mission". I ordered this book from Amazon after learning about it in a thread here on SGL.
  23. The Monthly Notices of the Royal Astronomical Society (MNRAS) is one place. https://academic.oup.com/mnras
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