If a photonic being cries outside of a holodeck, are the tears real liquid, or do they simply disappear after they leave physical contact with the photonic being?
Depends on the type of Holodeck tech used, folks sometimes forget that there are different types.
If it uses some kind of protomatter like the Enterprise Holodecks it could leave a residue of protomatter, if it's just magnetic fields and light nothing would remain, if it's a Omicron Field it's not limited to a holodeck, but were would lose conference outside the field, but would leave Omnicron particle residue, and Isomorphic projection tears would last until someone shuts them off.
Holodecks don't use protomatter - if you don't know the process the Lukari developed, it's dangerously unstable and prone to all manner of unpleasant effects up to and including spontaneous explosion.
Comments
If it uses some kind of protomatter like the Enterprise Holodecks it could leave a residue of protomatter, if it's just magnetic fields and light nothing would remain, if it's a Omicron Field it's not limited to a holodeck, but were would lose conference outside the field, but would leave Omnicron particle residue, and Isomorphic projection tears would last until someone shuts them off.
Last instance of Protomatter I'm aware of was Genesis.