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  1. nearc

    B Prerequistive for posting in Special and General Relativity

    i am far from an expert in Special and General Relativity, however, my attempts to learn from this forum are hampered by the large volume of posts involving common misconceptions and lack of understanding of the material. while the members of the forums patiently [usually] help our novice and...
  2. nearc

    I Modeling a simple N-body in a hypothetical relativistic dark flow

    i assume there are already several basic relativity models, at least one for mercury? i would prefer an N-body model one that would allow me to add an additional uniform velocity in one direction, but any model would be a starting point.
  3. nearc

    I Modeling a simple N-body in a hypothetical relativistic dark flow

    Looking for existing examples of or guidance on building computer simulations of simple N-bodies in relativist situations. Of particular interest is the simulation of a planet orbiting a star whilst that trivial solar system is caught in a dark flow of relativist velocity; maybe .8 or .9 C. Not...
  4. nearc

    B The Universe without Cosmic Inflation?

    obviously i cannot speak for mr smith, however, i like the use of his phrase "too convenient" as it gets the point across without being as blunt as i would have been, moreover, the phrase is accomplishing its goal by keeping people questioning the validity of using inflation
  5. nearc

    B The Universe without Cosmic Inflation?

    that's what i thought thanks for the clarification. i was tempted to use the analogy about how babies are produced during sex but babies can also be produced without sex, however, in that analogy inflation would be intercourse so there are some obvious crass images plus the very short duration...
  6. nearc

    B The Universe without Cosmic Inflation?

    unless i'm very confused [which is often] i thought matter forms when the temperature drops. there might also be some need for expansion or even complicated cooling/heating but ultimately once things are cool enough and there is enough room matter can form? we tie matter formation into...
  7. nearc

    B The Universe without Cosmic Inflation?

    for my own clarity, are you saying inflation is required to produce matter or inflation affects the production of matter?
  8. nearc

    I Spacetime Of Flatland

    since we are using "flatland" as the reference point you might want to explicitly restrict interactions to only the 2D. since in the book a 3D object was allowed to interact. if that is possible then the gravity of an object outside the the 2D land could change the physics of the world
  9. nearc

    Vernal Equinox

    not sure quite what you are looking for but i recently used this site to help me convert from silly celestial to galactic coordinates, however, points far above or below the galactic plane does not yield the correct longitude. http://www.atnf.csiro.au/people/Tobias.Westmeier/tools_coords.php
  10. nearc

    B History of RA [why is the vernal equinox used?]

    i failed to find the history of RA [right ascension] and why the vernal equinox was picked as the starting point on the web or in the forums here. does anyone know the origins of RA? picking a solstice or equinox is obvious but why the vernal? maybe because spring in the northern hemisphere...
  11. nearc

    Announcement Changes to member Profiles

    there needs to be a "i wish i was still in school" option
  12. nearc

    I Best way to filter NED redshift data

    thanks help_bot, i think that is friendliest response, i've ever received here. i've tried various things, right now i'm grabbing tiny pieces of the data [~100,000 data points at a time] and sorting out only the redshifts with the SPEC flag. SPEC means it was measured with a spectrometer...
  13. nearc

    I Tight grouping of exoplanets 295RA 45dec

    wow, i'm not paying attention, thanks again
  14. nearc

    I Best way to filter NED redshift data

    i'm using http://ned.ipac.caltech.edu/ui/?q=byparams to extract redshift data. while i'm very happy there is now lots of data available, data requests need to be limited in size or you get an error. i would like to examine the patterns of redshift vs longitude, but that is too much data, i...
  15. nearc

    I Tight grouping of exoplanets 295RA 45dec

    thanks a bunch, that makes sense, however, the following figure suggests its center is around 37 DEC is that correct? https://en.wikipedia.org/wiki/Kepler_(spacecraft)#/media/File:Kepler_FOV_hiRes.jpg
  16. nearc

    I Tight grouping of exoplanets 295RA 45dec

    thanks for pointing out the typo, meant to say 295RA, fixed my replies but can not change original title [edit: yes, fixed original OP title] should we close this and reopen a new thread? also the link defaults to something other than i copied, but that is just one external link an only needed...
  17. nearc

    I Tight grouping of exoplanets 295RA 45dec

    i'm having bad memories of undergrad when a geology TA took off points on my lab report for not specifying the subducting pacific plate was on earth edit: now that i know people are responding to the incorrectly used graph instead of the OP, this comment may not apply my apologies
  18. nearc

    I Tight grouping of exoplanets 295RA 45dec

    lets not be earth-sized-centric here ;) the tight grouping is mostly average-sized if not slightly smaller than the rest of the exoplanet data: graph planet size vs RA and DEC and you will see most of the grouping at RA295ish and DEC45ish fall in the middle and definitely not on the large...
  19. nearc

    I Tight grouping of exoplanets 295RA 45dec

    most of the planets in that direction are a little smaller than average
  20. nearc

    I Tight grouping of exoplanets 295RA 45dec

    most of the planets in that direction are a little smaller than average
  21. nearc

    I Tight grouping of exoplanets 295RA 45dec

    does anyone have any information on why the vast majority of exoplanets are located in one spot? any papers on the topic? the following link does not graph RA vs DEC but instead does something about planet size, if you wish to use it please select RA for the x-axis and DEC for the y-axis, both...
  22. nearc

    Where can I get help with David Bachman's A Geometric Approach to Differential Forms?

    thanks, i think that was for first edition but i'm not sure
  23. nearc

    Where can I get help with David Bachman's A Geometric Approach to Differential Forms?

    thanks, latex fixed, now i need to ponder the triangle approach
  24. nearc

    Where can I get help with David Bachman's A Geometric Approach to Differential Forms?

    this starts as a calculus question, but springs into where i can get help with david bachman's A GEOMETRIC APPROACH TO DIFFERENTIAL FORMS second edition. looking at paul's notes cheat sheets http://tutorial.math.lamar.edu/cheat_table.aspx we have ## \int \frac{1}{\sqrt{a^{2}-x^{2}}} =...
  25. nearc

    how fast is fast?

    how fast is fast?
  26. nearc

    Support PF: Buy on Amazon.com from here

    if it is ok, i will share your amazon affiliate account info with the supercomputing challenge [ http://challenge.nm.org ] and i will ask them to put your website on [ http://challenge.nm.org/resources/ ] since many students and a some teachers [like me] could use the expert help found on these...
  27. nearc

    Support PF: Buy on Amazon.com from here

    FYI, it looks like it will work with amazon smile too, i copied the /?tag=viglink20267-20 and put it at end so it looks like http://smile.amazon.com/?tag=viglink20267-20 now i can support my favorite* non-profit and PF! *in case you are interested i'm supporting the Supercomputing Challenge...
  28. nearc

    Gravitational equations used in model of orbiting bodies

    velocities are not being added to masses, if you are referring to: m_{ix_{new}}= m_{ix_{old}}+ v_{x_{new}} that is the x position of mass i, being adjusted by the the velocity which is multiplied by the time step [remember the time step is built into G]. velocity multiplied by time yields...
  29. nearc

    Gravitational equations used in model of orbiting bodies

    the only equations i can find with inconsistent are: v_{x_{new}}= v_{x_{old}}+ F_{x_{new}} v_{y_{new}}= v_{y_{old}}+ F_{y_{new}} can you point out how the other ones are also inconsistent? are you saying these equations are wrong?: F_{x_{new}}= F_{x_{old}}+ Fcos(\Theta)...
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