It’s a matter of removing the spawn test, and/or replacing the age test with it. The position of the display node is inconsequential.
This is what your flow is doing:
Event 001
Birth 200 particles between frames 20 and 21
position particles at sphere
apply gravity
test particle age; Is the particle more than 1 frame old, plus or minus a random value of 250 (between -249 to 251)?
If true, send to next event…
At this point, you already have the problem of some or all of your particles immediately moving to the next event, before your gravity force has a chance to work it’s magic. If you’re spawning the particles inside a sphere, you’re probably not seeing them, because they haven’t moved passed their initial spawn point.
Event 002
test spawning of new particles
If true, send and spawn particles in next event…
Ahh, but you’re not doing anything with these newly spawned particles.
I would highly recommend watching some tutorials, so that you can get a better idea of the “flow” in particle flow. It would be a lot easier than trying to feel your way around in the dark. Look up Allan Mckay. That’s a great place to start. 