Recent content by ddoctor

Here is my situation: I am currently a physician now for the last 20 years. I'm 51. I have a B.A. in Astronomy which is my passion. I want to go back to graduate studies in physics/astronomy. I tested this out several years back and took a graduate astronomy course at our local university. I was...

Do what you love. Forget about things like tedium and money. You can't take the money with you. Believe me. I'm an orthopedic surgeon now and after 20 years I am planning to return to graduate studies in physics and/or astronomy (I have a B.A. in astronomy) because astronomy is my passion. Sure...

Hi group, Could someone 'remind me' why the equation u" + u = km/L^2 has the solution of the form u(theta) = km/L^2 + C cos(theta - theta(o)). Any references would be appreciated. Thanks Dave

So basically what you are saying is that C, N, O are not present in the photosphere in sufficient quantities under the right temperature conditions in relation to their respective binding energies to produce significant absorption spectra? However there are a couple of spectral types where you...

Why don't stellar spectra show absorption lines for carbon, oxygen or nitrogen if they are such abundant elements. Is there a 'spectral type' that does? Thanks Dave

ok. thanks! so then i get [(x+1)^2 - (x-1)^2/ (x+1)^2] . after that i expanded the polynomial expressions in the numerator and combined them. that simplifies to sqrt [(4x)/ (x+1)^2] or 2 * sqrt (x)/ (x+1). easy enough.

no idea how to simplify this one: sqrt [1- [(x-1)^2/(x+1)^2]] thanks dave

Hi group, Simple arithmetic problems using PV = nRT or NkT. How do you know when to use pressure units in atmospheres or pascals? For example, in 1 particular problem they give you a pressure in units of Torr, volume in cubic cm and temp in Kelvin and ask for the number of molecules. Couldn't...