After a long hiatus…

Hi folks, this is me again, some time ago since my last post. This is just a new entry to leave a comment about the future of this little blog of mine.

Time flies, things happen in live that make your time a scarce resource. I’m not quite sure if I will be posting again or this will last much, but I think that if I do, I’ll just use this blog to note down some resources, some activities that I’ll dedicate to in my spare time that have to do with Physics . Somehow, as a place to register (just for myself) my activity in subjects that interest me (Physics and Maths), but I’m pretty sure I won’t try to post long entries explaining complicate (or simple) concepts of Physics, as might have been my initial intention some time ago. That way lead me to abandon the blog as I didn’t have much time to review books, videos, etc. and prepair the blog entries. So I’ve decided to come back but just to do what I could be doing with a small notebook: include a link to a Physics related webpage that I’ve found, include a link to a video or set of videos that I’m interested in, etc.

Another objective that I want to keep on pursuing is writing in English oftenly. BUT, as English is not my mother tongue and I used to dedicate some time searching for the accurate word to say something and it consumed time…, from now on I will post without playing much attention to my incorrect use of the language (if it happens, which I have no doubt that will occur, sorry!). I want to use the blog for myself, in a fresher, quicker and more useful way for me.

Anyway, if you want to read my activity here or leave interesting comments, you’re welcome!

–Javier

Was Einstein right?

This is the title of chapter #19 from the course “Dark Matter, Dark Energy: The Dark Side of the Universe”, already commented in previous posts. This time some of today’s notes have to do with to great physicists. Apart from equations or theories that try to explain our Universe, it is also important to know a little bit of History of Science and be aware of these names:

  • Urbain Le Verrier: Le Verrier is mentioned in this chapter as he was the guy that made a prediction about the existence of a planet, not known in the first half of the 19th century. That planet was Neptune. He was also the first to report that the slow precession of Mercury’s orbit around the Sun could not be completely explained by Newtonian mechanics and perturbations by the known planets. You know, the same precession that was explained later by Einstein`s General Theory of Relativity.
  • Mordehai Milgrom: Israelei physicist that proposed the MOND or Modified Newtonian Dynamics as an alternative explanation to Dark Matter. MOND is a hypothesis that proposes a modification of Newton’s law of gravity to explain the galaxy rotation problem.
  • Vera Rubinshe was the astronomer that pointed out the phenomenon known as the galaxy rotation problem (already mentioned): discrepancy between the predicted angular motion of galaxies and their observed motion.
  • Jacob Bekenstein: another Israeli physicist famous because he contributed to the foundation of black hole termodynamics. He was the first one to suggest that black holes should have an entropy.
  • The bullet cluster: two colliding clusters of galaxies into one, whose Gravitational lensing studies are supposed to provide the best evidence of Dark Matter.
  • The Friedmann Equation: it is a well-known relationship between the energy density of the Universe, the expansion rate (Hubble constant) and the curvature of space. It governs the expansion of space in homogeneous and isotropic models of the universe within the context of general relativity. That is:

(8πG/3 ) ρ = H2 + K

  • The Cassinni probe: spacecraft mission launched in 1997 to study Saturn and its moons.

Although I would recommend purchasing the original videos from The Teaching Company, this chapter can be seen on YouTube here (part 1) and here (part 2).

An additional comment/confession that I’m not sure if I’ve already done before: you may realize that some of these notes or definitions are in some parts copy-pasted directly from Wikipedia. This is because I’m just trying to have short notes to illustrate (mainly for myself) what I’ve been reading/watching/working on… And what a better definition (of course, not always) that the one that appears on the Wiki, validated many times before… 

The Great Courses (so far)

I am a convinced follower of The Teaching Company video courses, known as “The Great Courses”. I have already visualized some of them, all related to Physics:

As I am in an advanced point in this last course, I’ll just leave here the contents of the course and in a later post I’ll write down the main concepts that have appeared in the later chapter I had seen (it’s a pity that I haven’t done this before), chapter #18 “Quintessence”, with some links to the explanation of those concepts. Here it is (extracted from Sean Carroll’s personal site):

  1. Fundamental Building Blocks
  2. The Smooth, Expanding Universe
  3. Space, Time, and Gravity
  4. Cosmology in Einstein’s Universe
  5. Galaxies and Clusters
  6. Gravitational Lensing
  7. Atoms and Particles
  8. The Standard Model of Particle Physics
  9. Relic Particles from the Big Bang
  10. Primordial Nucleosynthesis
  11. The Cosmic Microwave Background
  12. Dark Stars and Black Holes
  13. WIMPs and Supersymmetry
  14. The Accelerating Universe
  15. The Geometry of Space
  16. Smooth Tension and Acceleration
  17. Vacuum Energy
  18. Quintessence
  19. Was Einstein Right?
  20. Inflation
  21. Strings and Extra Dimensions
  22. Beyond the Observable Universe
  23. Future Experiments
  24. The Past and Future of the Dark Side

Hello darkworld!

Day #1 of this site: About me… page. Explanations there.

Let’s begin blogging!

Regards,

Javier