In the end of Avengers (2012) movie,

BLACK WIDOW: I can close it! Can anybody hear me? I can shut the portal down!


IRON MAN: No, wait!

CAPTAIN AMERICA: Stark, these things are still coming!

IRON MAN: I got a nuke coming in, it's gonna blow in less than a minute. And I know just where to put it.

And then Iron Man carried the nuke inside the portal. The nuke hit the Chitauri mothership, which terminated the Chitauri army on Earth.

After they waited for some time for Iron Man to return, Captain America said, "Do it," and Black Widow hurriedly closed the portal.

Why were they in such a hurry? The Chitauri army was down. The situation was fully under control. Iron Man wasn't back yet. Why couldn't they wait for 10 minutes or half an hour until Iron Man got back or for Thor to go look for him and broadcast the Chitauri space location to Heimdall? I mean, if Chitauri started coming down again, they could always stop waiting and close the portal immediately.

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    Because the Chitauri might have another million soldiers on the other side of the portal?
    – Valorum
    Commented Oct 13, 2017 at 17:17
  • 8
    Debris... blast-wave/fallout... that's off the top of my head... there's also the fact that Chitauri, Tony, and nuke aside, they have no idea what's through there...
    – Radhil
    Commented Oct 13, 2017 at 17:17
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    @Valorum Read the question again.. if Chitauri started coming down again, they could always end that wait time to close the portal immediately.
    – user931
    Commented Oct 13, 2017 at 17:31
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    @Discovery - This is, of course assuming that the first Chitauri soldier through doesn't blast her head off.
    – Valorum
    Commented Oct 13, 2017 at 17:32
  • @Valorum When she was first going to close the portal, there was an army swarming around her. They didn't blast her head off. I think, she was more capable of protecting herself than what you think.
    – user931
    Commented Oct 26, 2017 at 3:18

2 Answers 2


This is addressed in the film's script. In short, the shockwave caused by the nuke and the secondary explosions of the Chitauri vessels was visible from the surface. Captain America wanted to shut the portal before it arrived.

EXT. SPACE: We then see Tony's horror. AN ARMADA. The black sky is filled with what must be ninety ships in a vague cluster. Most of them hang still in the air. Some move swimmingly about. IRON MAN lets go of the missile. It whistles off into the blackness as IRON MAN IDLY falls back down the portal's opening. The missile reaches the MAIN SHIP. The MAIN SHIP IMPLODES, causing the entire ARMADA to burst into a supernova, creating a spectacular heavenly display.

... [shortly afterwards]

EXT. MANHATTAN ­ DAY: Thor and Cap see the supernova coming towards them. Thor nods to Cap.


  • 13
    A shockwave in a vacuum. Yes, I know, it's a comic book, stop trying to make sense of the physics... Commented Oct 14, 2017 at 4:27
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    @StephenCollings Also Iron Man "IDLY falls back" in space, where there is no Gravity.
    – Ghos3t
    Commented Oct 14, 2017 at 5:07
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    @user258365 the portal was still open, so gravity from Earth could conceivably be felt.
    – jaxad0127
    Commented Oct 14, 2017 at 6:24
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    @jaxad0127: In the director's commentary on the movie, Joss says "I love the way the gravity catches him just as he goes through. Those little bits of physical reality in what is an absurd, ya know, portal-through-space concept are extremely necessary" (at 2:07:25s). So no, gravity didn't take effect until he was already through. That's why it's "idly" until he gets to the portal. But drifting and falling in space are basically the same thing. In orbit, for example, you're falling but going so fast sideways that you miss the planet. Commented Oct 14, 2017 at 7:57
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    @Ghos3t He may have been falling back from throwing the missile. Conservation of momentum.
    – jpmc26
    Commented Dec 23, 2017 at 5:57

Rewatching the scene in question (1:20), the nuclear explosion combined with the ships themselves exploding produced a sizable blastwave, which passed by just after the portal closes. Closing the portal with the timing they did saved New York from an a significant amount of additional damage, not to mention fallout.

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    @Discovery - You don't normally do it over major cities.
    – Valorum
    Commented Oct 13, 2017 at 17:37
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    @Discovery Nuke testing in the sky was done very high up over very remote locations, and still did plenty of damage. While technically in space, the proximity of the portal meant that the practical detonation altitude was still fairly low. We also don't know what energy the ships may have added. What we do know though, is the blast passed right by where the portal was, and had it not closed, would have gone through
    – Mwr247
    Commented Oct 13, 2017 at 17:40
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    michaeljohngrist.com/wp-content/uploads/2009/giant%20holes/… -- This is where an island was, before it was nuked off the planet, from 500m up. Commented Oct 13, 2017 at 21:43
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    @djsmiley2k That's from an air blast, not a space detonation. Space blasts are done from 20 km up to 400 km altitude. There is no appreciable amount of air in a space detonation, so no appreciable shockwave.
    – reirab
    Commented Oct 13, 2017 at 22:05
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    Actually there were nuclear tests done in high orbit and the effects were found to be devastating enough that it scared the countries into not doing it again. Operations Dominic I and II, and Starfish Prime. What they found is that the high altitude and the van allen radiation belts AMPLIFIED the effects to nigh uncontrollable levels, which means the nukes would have been very indiscriminant on who they hit. At the very least.. it would have shut down the space program for ALL countries if they continued. So that wasn't a no, but a HELL no.
    – whiskeyfur
    Commented Oct 13, 2017 at 22:16

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