Does a person under the effect of Astral Projection count as on a different plane for another caster on the same plane as their physical body?

Question

I asked this question regarding the gate spell targeting someone using astral projection and the results were inconclusive. One thing that I realized however, is that gate can only summon someone on a different plane as the caster.

When you cast this spell, you can speak the name of a specific creature (a pseudonym, title, or nickname doesn't work). If that creature is on a plane other than the one you are on, the portal opens in the named creature's immediate vicinity and draws the creature through it to the nearest unoccupied space on your side of the portal.

This makes the original question even more complicated, but also poses a question for other spells such as sending which might fail if a target is on a different plane than you:

if the target is on a different plane than you, there is a 5 percent chance that the message doesn't arrive.

And also scrying which can only target a creature on the same plane:

You can see and hear a particular creature you choose that is on the same plane of existence as you.

There may be other such spells, so I'm asking in general if a caster is attempting to target someone whose physical body is on the same plane as them but under the effects of astral projection, will that target count as on a different plane or on the same plane?

Answer 1

There are two bodies, and Gate would work.

Astral Projection:

"You and up to eight willing creatures within range project your astral bodies into the Astral Plane.... Your astral from is a separate incarnation.... If a creature's original body or its astral form drops to 0 hit points, the spell ends for that creature." PHB 215 (emphasis added by me)

From the spell description we can conclude that a creature under the effect of Astral Projection has two separate corporeal forms located on two separate planes. Essentially, they are split into two separate creatures sharing a single consciousness.

Gate:

"When you cast this spell, you can speak the name of a specific creature. If that creature is on a plane other than the one you are on, the portal opens in the named creature's immediate vicinity and draws the creature through it to the nearest unoccupied space on your side of the portal." PHB 244 (emphasis added by me)

As a reminder, a creature affected by Astral Projection is both on their original plane when having cast the spell, and on the Astral Plane. Therefore, if you are casting Gate from the original plane targeting a creature affected by Astral Plane, they do count as being "on a plane other than the one you are on" as defined by the Gate spell.

What would happen is their astral body would be pulled through the Gate to your plane (a plane other than the Astral Plane). Then, as per the Astral Projection spell:

"If you enter a new plane or return to the plane you were on when casting this spell, your body and possessions are transported along the silver cord, allowing you to re-enter your body as you enter the new plane." PHB 215

As far as other spells...

Consider which body would be effected by that spell, if not both of them. Each spell would need to be considered individually and the outcome should be determined by your best judgement.

In the case of Sending, I suspect the message would reach both bodies (given the 5% chance to not reach the astral body), but would not be heard by the unconscious physical body.

In the case of Scrying, you would end up reaching the unconscious physical body should the spell succeed.

Answer 2

Separate Bodies, Choose your Targets Wisely

Astral Projection states (PHB, 215)

Your astral form is a separate incarnation

When under Astral Projection, you basically have two separate bodies: The Astral Body and the Physical Body.

If you are trying to target someone and they are under Astral Projection, you have two options:

1. Target the Physical Body(Default)
2. Target the Astral Body (would need to know if advance that they are under Astral Projection to do this)

Determine Planar similarities based on where you are and which body you are targeting.