Recent content by trekie

I apologize if this has been asked before. I searched on this site and others but didn't find this particular issue. My background is physics and math. My question is near the end of the post. First, let me explain my thoughts leading up to my question. After many years, I'm reviewing the...

Thanks! I understand it much better now.

More than one person has objected to "unwanted heat loss", which is apparently the wrong thing to say in this context. I'm referring to the idea that heat transfer through a finite temperature difference can contribute to the irreversibility of processes (Moran, John (2008). "Fundamentals of...

For Fourier's law ##\vec{J}=-k\nabla{T},## where ##\vec{J}=## conductive heat flux in ##\frac{W}{m^2}## k=thermal conductivity in W/m-K T=temperature, ##\frac{1}{k}\vec{J}## certainly appears to be a conservative field with temperature as potential and for any path from position a to position b...

Thx all for the replies. I should have known the problem was mathematica's [wolfram alpha] behavior when doing certain calculations.

Hi, I'm sure this has been asked many times before, and I tried to find a sticky for this, but can some1 please tell me the easiest way to get latex code to display properly when I'm browsing the math & physics forums? The code usually displays for me as unreadable white marks against a black...

I noticed some unexpected behavior in the real-valued f(x)=(1+x)^1/x, as a function of real numbers, when plotting it on wolfram alpha. I inputed: plot (1+x)^1/x from x=-0.0000001 to x=0.0000001 and saw that it unexpectedly seemed to oscillate near zero. I took a closer look with: plot...

or the mean minimum volume within the region that contains at least 1 star system

aswoods at www.sosmath.com/CBB/viewtopic.php?p=197769#197769 helpfully pointed out that Gradshteyn and Ryzhik 3.381.10, and Wolfram Alpha agree that the integral from 0 to infinity of x^3 e^(-ax^3)dx = 1/3 gamma(4/3) a^(-4/3) so the mean nearest neighbor distance in 3d is: <r> =...

I'm not sure but I think the problem with your approach is: 1. There are 2 star systems within your control volume; the system at the center and the nearest system. 2. your volume as stated doesn't need to be centered on an arbitrary star system, but can be centered at any point. Perhaps you...

since what we really want is the average distance to the nearest star system, and atlasoftheuniverse.com reports 23 star systems within 12.5 ly (35 stars but 3 trinaries, 6 binaries, and 14 singles), we have: rho = 23/([4/3]pi 12.5^3) rho = 0.0028113 star systems/cubic light-year rho is...

Modest at http://hypography.com/forums/physics-mathematics/21509-mean-nearest-neighbor-distance-3d.html was helpful in pointing me to this link...

Hi. In 3 dimensional Euclidean space with the usual metric, d=[(delta x)^2+(delta y)^2+(delta z)^2]^1/2, I'm trying to figure out the average distance between nearest neighbors in a randomly distributed sample of particles. My best initial guess for the average distance from any given particle...

marcus & chalnoth: thx for ur responses, i found them both to be very helpful. u pointed me in the right direction, i think. i don't think i ever studied Fourier spectrometry [and 5000 other subjects], but http://www.astro.ljmu.ac.uk/courses/phys362/notes/ has an excellent analysis. i had to...

2 questions: would u happen to know what information was provided by the FIRAS interferometer on board COBE which is then converted into MJy/sr and then represented in the NASA graph i referenced? can W/(m^2-Hz-sr) be converted into W/(m^2-m-sr) w/o multiplying I_nu (T) by |d{nu}/d{lamda}|...