User suggestion: gravity controls to support evaporation

[ariel-phet]

We are not going to change the current sim, however a user wrote to me on twitter with the following use case that we might want to support in a future version of the sim when we have more macroscopic scales (to support things like atmospheric science goals)

The user wrote:

Hi PhET, thanks for updating gas properties, what a fantastic resource!

In the previous version I could put the gravity on full power, and add enough particles to make it 'look like' a liquid. I then used this to teach evaporation. It was the best possible way I have found for students 'to see it' and understand how evaporation has a cooling effect.

Is there anyway the gravity feature could be added into the new simulation? Or in fact, an evaporation simulation being developed?

Marking deferred, but putting here to record the suggestion for now.

[pixelzoom]

A clarification about the mention of "future version of the sim" above... Removing the gravity feature was a deliberate choice made during the design process. We decided that gravity was not essential to the learning goals of Gas Properties, and would be addressed in another (new) sim. This simplifying assumption was one of the reasons why we completed implementation significantly sooner than anticipated, and I mentioned at the time that it would not be possible to add it later. The model implementation cannot support it, has no way to add it, and in fact relies on the absence of gravity; the model would need to be rewritten. So hopefully "future version of this sim" actually means "a new sim that addresses atmospheric science goals".

[ariel-phet]

Yes @pixelzoom, exactly correct

"a new sim that addresses atmospheric science goals".

[jbphet]

Got this from a member of the Astrophysical & Planetary Sciences dept here at CU:

I’m very sympathetic for your having to adapt all the PHeTs to a changing
software environment. I thought you should know, though, that
I (and other astronomers and atmospheric scientists) really miss
that the new Gas Law PHeT doesn’t have an option to turn on gravity
like the old one does.

All planets and the earth have atmospheres that get thinner as you go “up”
due to gravity, and so I used that PHeT feature in every planetary science course that I taught.
Very sad that it is gone. Would it be hard to add to the new Gas LawPHeT?

[pixelzoom]

We are not addressing this for the 1.1 release #191.