Were other dimensions affected by Thanos' Snap?

Question

In Doctor Strange, we are made aware of the different universes and especially the one one in which Dormammu resides, which is the Dark Dimension.

Were beings in other dimensions also affected by the Snap Thanos did in Avengers: Infinity War? Were beings like Dormammu also affected by the Snap or were they more than just a creature and the Snap did not have any effect on him?

My knowledge says Thanos himself says the following in Avengers: Endgame:

The universe required correction. After that, the stones served no purpose beyond temptation.

Which confuses me, are other dimensions also affected?

Answer 1

Yes

Exhibit A:

The Quantum Realm is considered a separate dimension, as part of the Multiverse in the MCU.

• https://marvelcinematicuniverse.fandom.com/wiki/Multiverse
• https://marvelcinematicuniverse.fandom.com/wiki/Quantum_Realm

The quantum realm is first introduced in the MCU in the Ant-Man movie. It is explained by Dr. Pym that the quantum realm is a distinct reality, although he does not state explicitly that it is a different dimension. From the transcript (emphasis mine):

• Dr. Hank Pym: It means that you would enter a quantum realm.
• Scott Lang: What does that mean?
• Dr. Hank Pym: It means that you would enter a reality where all concepts of time and space become irrelevant as you shrink for all eternity. Everything that you know, and love, gone forever.

In the Doctor Strange movie the Quantum realm is shown again when the Ancient One first tells Strange of other dimensions. This is confirmed in the Director's commentary:

This image here is obviously a nod to Ant-Man and the Quantum Realm, acknowledging that as one of the mysterious realms of existence.

-Scott Derrickson, director for Doctor Strange

Here's a video showing Both the Ant-Man and Doctor Strange movie scenes having to do with the Quantum realm. Strange enters the Quantum Realm at the 0:47 mark and exits at 0:55.

Exhibit B:

In the SDCC 2019 panel, Infinity War and Endgame writers Christopher Markus and Stephen McFeely confirmed the snap is interdimensional.

Did the Quantum realm get snapped? The writers say the stones do no differentiate, so Scott surviving was the lucky flip. Ant-Man was really lucky, it seems.

Answer 2

It would be highly unlikely that Thanos' Snap affected other dimensions. Firstly, we have no indication he even knew there were other dimensions; the closest we see to him seeing this is when he fights Strange. However, most of what Strange does there is just ordinary "magic".

Thanos is also correcting the universe to help save it and the life within it. If he were to affect some of the other dimensions which don't have direct life, for example, the Mirror Dimension, that might cause more problems than it solves.

Thanos: Little one, it's a simple calculus. This universe is finite, its resources finite. If life is left unchecked, life will cease to exist. It needs correction.

_{Avengers: Infinity War}

Some of the dimensions are also more parallel worlds than life giving places, for example, the Astral and Mirror Dimensions. It wouldn't make sense to affect those in the first place as they don't harbour life.

And lastly, of the other dimensions we see only the Dark Dimension has any life within it (that I'm aware of) and that life is only Dormammu. It wouldn't make sense to kill him for the reasons of the Snap in the first place. And as he and the Dark Dimension exist outside of time it might not even be possible. Strange was only able to affect Dormammu in Doctor Strange because he took the Time Stone into the Dark Dimension. It's possible that the Time Stone can't affect it when outside of it and as such the might of the other 5 Infinity Stones is not enough for a full Snap.

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I just want to tack a note on the end though that with Doctor Strange in the Multiverse of Madness coming out in a few years we might get a more explicit answer then. Even though it is likely to be set after Avengers: Endgame.

Answer 3

Short answer, No!

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Doctor Strange's action in Avengers: Infinity War

During the short one-to-one fight that ensued on Titan between Doctor Strange and Thanos, Strange did try to trap Thanos in the mirror dimension. And as the Ancient One puts it:

The Ancient One: You’re advancing quickly with your sorcery skills. You need a safe space to practice your spells. You are now inside the Mirror Dimension. Ever present but undetected. The real world isn’t affected by what happens here. We use the Mirror Dimension to train, surveil, and sometimes to contain threats. You don’t want to be stuck in here without your sling ring.
_{Doctor Strange}

This supports the point that trapping Thanos (iff Strange was successful) would've prevented him from Snapping life from our dimension.

NOTE: Scott Lang's survival could've been the key that the Snap doesn't affect other dimensions. But since this theory is officially rejected by the writers, this one instance in the movies [kind of] supported the claim.