George Jones

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.

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.

Welcome to SGL. My in-laws live north of Toronto, near Canada's Wonderland.

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.

Welcome from Prince George BC.

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!

Nothing relaxes me as much as my observing sessions do.

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.

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.

How long is a typical talk?

Me too! Even if it does reach a conclusion, we might not like the conclusion. Paraphrasing Planck: "Science advances one funeral at a time." Actual version: "A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it."

A CPC 1100 and a SkyShed POD.

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.

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

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.