Mordred

In my spare time I will be writing a series of useful articles to help answer common questions. As these are being designed for forum reference I feel strongly on cooperative review. Here is the first. Please look over and feel free to make suggestions. Any solid contributions will be accorded credit at the end of the final product. (Key note all articles MUST comply with textbook descriptives, they are being designed as teaching aids) [latex]\textbf{The Cosmological principle}[/latex] is defined as "at sufficiently large scales, the universe appears as homogeneous and isotropic." [latex]\underline{Homogenous}[/latex] is oft defined as " no preferred location" [latex]\underline{Isotropic}[/latex] is oft defined as "no preferred direction" Obviously at smaller localized scales we can see numerous examples of systems that are inhomogeneous and anisotropic (planets, stars galaxies and large scale structures). However if you increase the radius of measurements sufficient enough those non uniform regions essentially become negligible or more accurately averages out. A good analogy is look at the surface of a lake. At small scales you can discern waves and ripples. As you increase in height or distance from the lake those non uniform regions become a uniform appearing surface. The cosmological principle works the same way. The scale commonly used is 100 Mpc mega parsecs. Speed of light in a vacuum: [latex]c\ =\ 2.99792458\ \times\ 10^{8}\ m\ s^{-1}[/latex] The parsec (symbol: pc) is a unit of length used in astronomy, equal to about 30.9 trillion kilometers (19.2 trillion miles). In astronomical terms, it is equal to 3.26 light-years, and in scientific terms it is equal to 3.09×1013 kilometers The cosmological principle has an added reward in that complex systems can be modelled as good approximations with far less complicated mathematics. However it should be noted that if measurements and observations disagree with the cosmological principle those metrics become invalid. We're lucky though as the body of evidence fully support the cosmological principle. A commonly referred to example being the CMB. Cosmic microwave background. Although the temperature images look chaotic, the difference in temperature of the blue regions and red regions are roughly 1/1000 of a degree. Certainly supports the cosmological principle. The cosmological principle is of importance in telling us that the Universe did not have an origin point nor is the result of an explosion. This is of primary importance in regards to expansion and inflation. Lets detail this a bit further. Take any number of points, three or more. As the volume of space increases, the same ratio of change will occur between any two points and the angles between those points also do not change. This mathematically is only possible via a uniform change regardless of location. A good analogy is the balloon analogy or the raisin bread analogy. http://www.phinds.com/balloonanalogy/: A thorough write up on the balloon analogy used to describe expansion http://tangentspace.info/docs/horizon.pdf:Inflation and the Cosmological Horizon by Brian Powell The other consequence of the cosmological principle is that the universe cannot have a rotation. All rotating bodies have a center of rotation and rotation imparts a preferred direction.

I do a lot of work with robotics in plant automation applications. The ones I deal with typically use ladder logic, ie Allen Bradley RS5000, and SLC 500. The other big names is Siemens. You would find SLC500 easier to learn. Keep in mind many robotic applications also incorporate data collection, so having C++ is also a good skill. Some industrial applications uses SCADA. (I've worked with well over 20 programming laquages, mostly relay/ladder logic, here is the thing. Choose one to learn. Once you can program in one laquage adapting to other lanquages is fairly straightforward. If you want a cheap method to learn ladder logic, but a low cost zelio smart relay or for AB, a picosoft relay. It will include the programming cable and software. Cost of under 200.00. SLC500 is around 2k, controllogix is roughly 3 to 4 k. (Wouldnt recommend the expensive ones to start) Good textbook on Automation systems is http://www.amazon.ca/Automating-Manufacturing-Systems-Plcs-Hugh/dp/0557344255 (Key note for robotics you will need a strong electrical, hydraulic and pneumatic understanding.) As well as calculus.

Cosmological principle the universe has no preferred location or direction Comprises two principle terms. Homogeneous no preferred location Isotropic no preferred direction. What this means is uniformity in overall energy density/mass distribution. Now the Einstein field equations and the FLRW metric are both interchangeable. They both involve the ideal gas laws. Cosmology describes the universe as a perfect fluid. pv=nRt Each contributor (particle etc) has an equation of state. http://en.m.wikipedia.org/wiki/Equation_of_state_%28cosmology%29 in GR energy density corresponds to pressure via the stress energy tensor. [latex]T^{\mu\nu}=(\rho+p)U^{\mu}U^{\nu}+p \eta^{\mu\nu}[/latex] http://www.th.physik.uni-bonn.de/nilles/exercises/ss04/gr05.pdf http://en.m.wikipedia.org/wiki/Stress%E2%80%93energy_tensor for the metric tensor portion above. http://en.m.wikipedia.org/wiki/Metric_tensor_(general_relativity) The full subject is too lengthy to post all the relationships. http://en.m.wikipedia.org/wiki/Metric_tensor_(general_relativity) I have numerous articles covering this under my signature for direct GR to cosmology chapter 9 covers this. http://www.blau.itp.unibe.ch/newlecturesGR.pdf"Lecture Notes on General Relativity" Matthias Blau However this book is rather advanced. I have some simplifications in these two articles. Site Articles (Articles written by PF and Site members) http://cosmology101.wikidot.com/redshift-and-expansion http://cosmology101.wikidot.com/universe-geometry page 2 FLRW distance to FLRW metric http://cosmology101.wikidot.com/geometry-flrw-metric/ these articles all cover the above the beginning chapters covering the Cosmological principle. Unfortunately the range of your questions require individual threads to properly answer each one even in narrative form Cosmological principle covered, Mass is resistance to inetia, you can have particles that are not matter with mass aka bosons. Elementary Matter particles are fermionic Google Pauli exclusion principle. Matter particles of the same state occupies space only one fermionic particle of the same state can occupy the same space. Any number of bosons can occupy a given volume. The entire universe is not being sucked into blackholes. Electrons go around the nucleus due to electromagnetic charge. Planets and moons is due to gravity. No one knows for sure past the event horizon. We can't measure it directly

You don't one essential detail. The research for a preferred location (center) has been done. None is found. More models than I can count tried having a inhomogeneous and anisotropic universe. As such this has been extensively looked into by BOSS. Planck,WMAP etc. The cosmological principle is extremely well tested.

Cosmology is based on observational evidence. Not believability. All observational data shows a strong agreement with no center, no preferred direction and no preferred location. The latest Planck dataset places this to near 100% accuracy, or as close as any model gets to that accuracy they always allow for some % of error. Read this particular article as well, it was written by Brain Powell who has a PH.D in Cosmology. http://tangentspace....ocs/horizon.pdf:Inflationand the Cosmological Horizon by Brian Powell You'll note the same details in the Lineweaver and Davies articles

The universe BB model was not an explosion nor does the universe has a center. It is a rapid expansion of space. Not a kinetic type explosion. Here is some material please read the misconceptions of the big bang Lineweaver and Davies in particular. Misconceptions (Useful articles to answer various Cosmology Misconceptions) http://www.phinds.com/balloonanalogy/: A thorough write up on the balloon analogy used to describe expansion http://tangentspace.info/docs/horizon.pdf:Inflation and the Cosmological Horizon by Brian Powell http://arxiv.org/abs/1304.4446:"What we have leaned from Observational Cosmology." -A handy write up on observational cosmology in accordance with the LambdaCDM model. http://arxiv.org/abs/astro-ph/0310808:"Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe" Lineweaver and Davies http://www.mso.anu.edu.au/~charley/papers/LineweaverDavisSciAm.pdf:"Misconceptions about the Big bang" also Lineweaver and Davies The balloon analogy is also handy

Neither time nor space is being created... the geometric volume of space simply increases. One of the most common mistakes is to try and define space with some fabric like property. Space itself has no energy or fabric. It is a geometric volume that is simply filled with the energy-mass from the rest of the universe. That being said the superluminal velocity measurements of expansion is a consequence of the separation distance and the Hubble flow. Hubble's law. The greater the distance the greater the recessive velocity. [latex]V_{recessive}=H_Od[/latex] the subscript o meaning the hubble parameter today, which is constant only in time..meaning at a particular time Its not a constant as per se a consequence of Hubble's law is that when recessive velocity becomes greater than the speed of light, this region is described as the Hubble radius or sphere. However the recessive velocity is not an inertial velocity hence as mentioned, as only the volume is increasing and expansion is not a consequence of inertia, GR and SR do not apply. This recent article written by a physicist friend of mine, covers this in excellent and well written detail. With very little math involved as his target audience is the general public http://tangentspace.info/docs/horizon.pdf :Inflation and the Cosmological Horizon by Brian Powell this is another good article http://arxiv.org/abs/astro-ph/0310808 :"Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe" Lineweaver and Davies We This is incorrect we can see farther than the Hubble sphere, Much farther. We can measure recessive velocities at z=1080 at around 3c. See the first article I posted to see why. correct

The terms created, stretched etc is VERY misleading. Space itself has no substance, fabric or energy. Space is simply geometric volume that is simply filled with the contents of the universe. However an important consequence of having a region of volume is that you will have a vacuum energy-density at the very least. This does not mean that the volume has a fabric or energy property. A volume of space is simply a filled region. Space geometry changes due to gravity is simply a descriptive of its energy-density distributions. The term warping of space is also a poor and misleading descriptive.

I've spent a few years collecting good articles to teach online students Cosmology, according to textbook standards. Here is a collection of articles Misconceptions (Useful articles to answer various Cosmology Misconceptions) http://www.phinds.com/balloonanalogy/ : A thorough write up on the balloon analogy used to describe expansion http://arxiv.org/abs/1304.4446 :"What we have leaned from Observational Cosmology." -A handy write up on observational cosmology in accordance with the LambdaCDM model. http://arxiv.org/abs/astro-ph/0310808 :"Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe" Lineweaver and Davies http://www.mso.anu.edu.au/~charley/papers/LineweaverDavisSciAm.pdf: "Misconceptions about the Big bang" also Lineweaver and Davies http://arxiv.org/abs/1002.3966 "why the prejudice against a constant" http://arxiv.org/abs/gr-qc/0508052 "In an expanding universe, what doesn't expand? Richard H. Price, Joseph D. Romano http://arxiv.org/abs/1301.0219What's in a Name: History and Meanings of the Term "Big Bang" Helge Kragh http://arxiv.org/pdf/0906.1442v1.pdf Is it possible to see the infinite future of the Universe when falling into a black hole? Training (textbook Style Articles) http://arxiv.org/pdf/hep-ph/0004188v1.pdf :"ASTROPHYSICS AND COSMOLOGY"- A compilation of cosmology by Juan Garcıa-Bellido http://arxiv.org/abs/astro-ph/0409426 An overview of Cosmology Julien Lesgourgues http://arxiv.org/pdf/hep-th/0503203.pdf "Particle Physics and Inflationary Cosmology" by Andrei Linde http://www.wiese.itp.unibe.ch/lectures/universe.pdf:" Particle Physics of the Early universe" by Uwe-Jens Wiese Thermodynamics, Big bang Nucleosynthesis http://www.gutenberg.org/files/30155/30155-pdf.pdf: "Relativity: The Special and General Theory" by Albert Einstein http://www.blau.itp.unibe.ch/newlecturesGR.pdf "Lecture Notes on General Relativity" Matthias Blau http://arxiv.org/abs/1201.4598 "Introduction to Loop Quantum Cosmology by Abhay Ashtekar http://arxiv.org/abs/hepth/9912205 : "Fields" - A free lengthy technical training manual on classical and quantum fields Historical article links http://www.astrosurf.com/luxorion/hubble-law-redshift1929.htm Reprint of one of Hubbles papers. http://www.marxists.org/reference/archive/einstein/works/1910s/relative/relativity.pdf An authorized reprint of Einsteins Special relativity paper. http://apod.nasa.gov/diamond_jubilee/debate20.html The "Great debate of the 20's" jubilee reprint article available http://www.drchinese.com/Bells_Theorem.htm Good reference site covering Bells theorem. http://www.intechopen.com/download/pdf/41230 good historical coverage of many of the key figures in Cosmology history http://arxiv.org/abs/1302.1498 " “The Waters I am Entering No One yet Has Crossed”: Alexander Friedman and the Origins of Modern Cosmology" written by Ari Belenkiy http://arxiv.org/pdf/1212.5499.pdf "The Contribution of V. M. Slipher to the Discovery of the Expanding Universe" by C. O’Raifeartaigh http://www.gutenberg.org/files/17384/17384-pdf.pdf "foundations of geometry" David Hilbert