New Nebula Types

posted on April 12th, 2010, 11:26 am

FO is harder SciFi than StarTrek itself. Things in FO seem to be intentional, sometimes even logical.

Couldn't be happier about that.

Oh:

http://www.dummies.com/how-to/content/chemistry-for-dummies-cheat-sheet.html

These books are made for this.

posted on April 12th, 2010, 1:01 pm

This is only a special case stated as isotherm...I did not say T is constant. Of course (and even in an idg) the temperature increases whenever you compress a gas...The volume is reduced and the pressure is increased...afaik there is no real process where only pressure and volume change...an easy example is ice skating...you slide because the high pressure melts the ice directly under the blades...

Ehm, we are talking about an ideal gas in an isolated system (Isoated because the nebula will not interchange warmth with anything outside, except of radiation, which we ignore here). Isolated => Temperature does not change from outside. What about a temperature-change from inside effects (still ideal gas).

1st Kinematiks: The kinetical Energy Ekin = mv²/2 = 3kT/2 meaning v²~T. When particles get faster, temperature rises. Ideal gas means, that molecules are arbitrarily small balls, that can exclusivly interact through fully elastic collision. Famous image are a few jumping balls in a box (forget about gravity, friction,... ideal!). The box has a volume. Compression is reducing volume, while letting all molecules stay inside the volume. Now, when all balls are coincidently on one side (happens often with few molecules, more seldomly with large numbers, but that does not chenge the principle), insert a wall that cuts off some space (ever played jezzball?). The balls are not touched, so they won't change their actual speed or direction, themperature is not changed . Just volume is reduced. The number of balls per volume increased, more bounces of balls at the walls per surface, meaning higher pressure.

2nd Energy conservation: In my before post I assumed that all the work (=energy used for compression) was transfered into the pressure and not changing the Temperature. Now assume that some of the work is transferred into rising the temperature. Meaning less work transferred into pressure. [pV =NkT] In other words the increase of p will not compensate the decrease of V any more. pV is not constant but decreasing. pV decreasing => NkT decreasing. So now we have something odd. Deacreasing of V now implies decreasing of T. But took away energy from pressure increase to increase Temperature. Thats an contradiction. The assumption cannot be nature.

If you now ask where the energy for temperature increase comes from...

On a realistic gas, particles are interacting, every particle in it's neighbors interaction potential. A energetically negative (binding) potential. If molecules come closer in average - meaning th gas is kompressed - they are in average more in their neighbors potentials, their av. potential energy sinking. Due to conservation of energy their av. kinetic energy will rise accordingly, meaning it will get hotter there.

A real gas provides the properties you ask for.