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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...

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.

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...

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

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...

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...

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

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

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

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...

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

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...

wow, I'm not paying attention, thanks again

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...

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

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...

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

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...

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

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

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...

thanks, i think that was for first edition but I'm not sure

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

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}}} =...

how fast is fast?

thanks

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...

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...

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...

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)...

i see the two initital distance equations where wrong and i fixed them, can you point out the other ones that are wrong? also i still don't know why a simulation with F=GM1M2/R^2 does not work but one with F=GM1/R^2 does?

In practice I’ve found that a valid gravitational model of orbiting bodies only works when the force is computed with only the other mass and not both masses. Thus, the original equation does not work but the modified one does. Is using one mass ok or am I doing something wrong? thanks. [also...

i would like to start with a simplified spiral galaxy. starting with a random distribution and ending with a stable spinning spiral. the number of bodies can be small, just large enough to show the intended behavior of the system not to recreate an existing galaxy.

while it may turn out to be a hideous or impossible task to bring this down to the high school level [heck it might be too hard to get down to my level ] i would like to try. as a reference point, the milky way is 100000 yr across, so the gravitation of a star on one side will take 100000 years...

I would like some introductory level references for building an n-body gravity simulation. I work for the supercomputer challenge [ http://challenge.nm.org/ ] and I build the teaching models each year we use to train teachers in computer modeling and provide as an example model for the students...

what about transverse redshift?

how do we explain other things like redshift/blueshift for example?

thanks for the help and clarifications. i was wondering how the bell paradox http://en.wikipedia.org/wiki/Bell's_spaceship_paradox might play into this? it might require adding acceleration however.

Traveling signal “paradox” Most relativity paradoxes are not true paradoxes they merely require some clarification about frame of references, stationary observer, etc… I hope some folk could help me clarify my “paradox” or point out where someone as already discussed this concept. We...

yep that's it, mathematica likes to switch things?

thanks simon, are you referring to $$e^{\text{ix}}=x \cos + i x \sin $$

thanks to simon I've figured out the simple elliptic however i now have a more difficult version: $$\int_0^{2 \pi } \sqrt{\left(1-\frac{60}{61} \cos (x-179)\right) \left(1-\frac{60}{61} \cos (x-t)\right)} \, dx $$ using mathematica i can find the solution to $$\int...

yep sounds like we still need to wait a bit but thanks

i did a search for juno flyby here and did not find anything, hence this post: i've not been able to find any info on the juno flyby anomaly. i know there was a hiccup but did we get any data? was the observed anomaly match the predicted anomaly?

thanks for your help, but I've looked through some basic elliptical integrals and I'm not finding anything like (cos x)^.5 the basic form is 1-(sin x )^2 also what I'm working with is not an ellipse it is a circle. the difference is that instead of a constant radius from the center tracing...

can you give me some good lead for elliptic integrals? thansk

thanks i'll reflect on this, but i suspect that this would only be useful in the case where i have right angles

yes, r1=r0+x, but there are no right angles in the figure

hopefully this is the right place for this question, the first part is a trig/geometry question but it is really a integration question: i'm trying to find another way to compute d1 without using law of cosines because i don't know how to integrate (cos a)^.5, if someone knows how to do that...

like i said i might be using the wrong term, let me elaborate: if we had a ring like an 'o' the center of mass would be in the center and if we removed part of the ring and had a 'c' shape the center of mass would be shifted slight to the left but still somewhere in empty space. would could...