Recent content by Zaphodx57x

Does anybody have a link to a precise definition of a "volume limited sample." This pertains especially to sky surveys that catalog galaxies. Due to limited precision, surveys tend to miss fainter galaxies as redshift increases. Thus, very loosely, I think, a volume limited sample filters out...

I am trying to convert the spearman rank test correlation coefficient to a p-value but I haven't been able to find anything online as to how to go about this. I'm not looking for a calculator, I really would like to know how to convert from this correlation coefficient to a p-value. Any help...

In a volume V there exist N particles of diameter d. If we place some detector in this volume, what is the probability that the detector will measure a collision in a time interval t. Or what is the probability that the detector will travel some specified distance into this volume. There...

I have a problem that asks for the surface density of starlight at 8 kpc for a particular spiral galaxy. I have all the information to calculate surface brightness. Does "surface density of starlight" mean "surface brightness", or are these completely different things?

Thank you much.

Given the right ascension and declination of two objects in the sky. Is there a way to calculate the angle between them? If so, do right ascension and declination need to be converted to radians or can they retain their units?

There exists one dust grain of radius 0.1 micrometer per every 10^12 hydrogen atoms. Show that as light travels through a 1 cm layer of this comrpessed gas, only about 1% will be intercepted. Then show how thick a layer would be needed to block 1/e of the rays. I believe the density of...

I made some progress by taking the maclaurin polynomial and only keeping the first couple terms. I can't get anything satisfactory for this one though \lim_{n\rightarrow infinity} [ln(n+1) - ln(n)] = 0 I get to an answer of 2-n or so, maybe I should keep more terms. Anybody help would be...

I'm not sure how to solve these problems. The example given in the book does not use trig functions. Any insight into how I solve these would be helpful. Find the following rates of convergence. \lim_{n\rightarrow infinity} sin(1/n) = 0 My thought would be to do the following...

I was reading today about superfluids and the like. They were talking about how at a certain low temperature bosons will all go into their ground state. I'm trying to get a physical feel for what this means. If a mole of helium 4 atoms(boson) are cooled so that condensation occurs. What...

Thanks for the reply. I'll play with it a little and see what I can get out of it.

I guess profundity is ruled out.

Ok, this might seem like either a really idiotic question or a really profound one. Consider a probability distribution. I'm picturing a normal distribution, is it meaningful to be able to build up a final probability distribution from a set of narrower probability distributions? Ok...

Is that force directly at point A? Is that a second force at the bottom? If I remember correctly, you usually have to find the spot where only components of tension and force in one direction can be calculated. Like, if that force is directly at point A then set up a static equilibrium...

I would start off by making at the very least a rough sketch of the volume you are trying to find, that way you can find out the boundaries you are dealing with.