We know that matter can only travel one way through a Stargate, ie. from the dialing gate to the destination. What happens to things that enter the wormhole from the destination side?

For example, if someone dials a gate that has tipped on its side (as in the SG-1 episode Hundred Days) and walks through, what happens when he reaches the other side and gravity causes him to immediately fall back into the gate?

Does the matter disappear, or does it pass through to the other side of the destination gate, as if the wormhole were not there?

Related: How could Ernest Littlefield have reintegrated on Heliopolis?

  • I have no source, so I'm not posting it as an answer, but I think I remember that everything that tries to use the gate backwards gets disintegrated (don't ask me where its relativistic energy goes to, it's just gone).
    – bitmask
    Apr 9, 2012 at 10:30
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    I always thought it would pass through the event horizon unaffected, and come out on the other side of the gate (not the other side of the worm hole).
    – Xantec
    Apr 9, 2012 at 11:45
  • @bitmask Teal'c once commented on it. It's not simple disintegration, but the object is destroyed in some way. I can't remember the exact quote or episode, though...
    – Izkata
    Apr 9, 2012 at 11:46
  • @Izkata: It vanishes/is destroyed/burns up. Something like that.
    – bitmask
    Apr 9, 2012 at 12:29
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    I guess that would explain the lack of bullet holes on the back wall of the gate room.
    – Xantec
    Apr 9, 2012 at 13:49

5 Answers 5


I do not think it is completely clear. As you suggest, in A Hundred Days they seem to indicate that the MALP is destroyed because it is falling back through the event horizon from the other side. Also, Teal'c goes to great lengths to secure himself above the event horizon to not fall back through upon arrival, leading us to believe falling back through would lead to his destruction/disintegration.

However, in the episode New Ground (Episode 3.19) we clearly see Nyan (the Bedrosian archaeologist) put his hand into the event horizon of the incoming wormhole from Earth with no ill effect. Maybe some small contact is okay, but attempting to completely enter the wormhole from the wrong side is not.

Taking the evidence from the two episodes above, I think we can hypothesize that touching or entering the event horizon of an incoming wormhole is not actually harmful. The Stargate itself must simply store the data from objects entering the event horizon in its buffer, regardless of whether the wormhole is incoming or outgoing. Since the Stargate only transmits discrete objects (and not pieces of objects), it does not attempt to forward the partial object and so the the object can easily be pulled back out. Once the entire object enters the wormhole the wrong way, however, the Stargate stores that data in its buffer and looks to send it on to the receiving gate. This is impossible if you've gone through the event horizon of an incoming wormhole since the Stargate cannot send the data on via an incoming wormhole, so the object is lost.

It is open to interpretation, I think, as to whether the object that entered through the event horizon of an incoming wormhole is still stored in the Stargate's buffer or not. If so, then once the incoming wormhole disengages, if someone wanted to retrieve the object, they could reconfigure the DHD to extract the data from the buffer (see, Episode 5.14, 48 Hours). However, the object would be lost if the Stargate is activated, clearing the buffer. It also may be lost after some amount of time (McKay has hypothesized that the buffer is only able to store data for 48 hours). (Once a new Stargate series launches, I'm totally pitching an episode in which the team hides in the buffer of a Stargate to elude an enemy.)

Of course, it is well known that if you touch the wormhole while it is being established, you are toast.

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    Partially entering the event horizon of an incoming wormhole is completely fine at all times. It's used in -tons- of episodes to prevent the wormhole from closing. The problem comes when fully passing through the even horizon, to the point where you would be transferred to the other gate.
    – Izkata
    Apr 10, 2012 at 0:00
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    @Izkata Right, that is what I was saying. If you partially enter, it doesn't attempt to send you on, if you fully enter it attempts to, but cannot, so you may or may not be stored in the buffer.
    – user5730
    Apr 10, 2012 at 0:10
  • I'm fairly positive that the Puddle Jumper in Episode 5x5 of Stargate Atlantis - "Ghost in the Machine", entered the Stargate from behind. I recently watched it, which is why I stumbled onto this question :).
    – VxJasonxV
    Jul 22, 2012 at 9:17
  • @VxJasonxV: I have just checked, and it does not. Mar 23, 2015 at 21:50
  • 3 years later, and since the Stargate series' have been removed from Netflix, I will give you the benefit of the doubt.
    – VxJasonxV
    Mar 24, 2015 at 6:14

It is really debatable. Taking into consideration how smart the ancients were, I don't think the screenwriters got this part right. The ancients would have put ALLOT of safety measures in place.

In countless episodes there has been stated that you must enter fully into the event horizon of the gate before you can reappear on the other side. So, I can draw the conclusion that the event horizon is part of the gate not of the wormhole. The wormhole ends at the gate, witch just materializes/dematerializes the information (people, objects) trough the event horizon.

I figure the logical safety measure would have been not to let anything pass trough the wrong way (if you try to enter the event horizon you would just press against a solid surface).

  • 7
    "The ancients would have put ALLOT of safety measures in place." These are the same people who designed a device which produces a meters long, all-annihilating wave on the other side. And there's no built in way to prevent your gate from being dialed. Safety third.
    – Schwern
    Dec 11, 2014 at 9:14
  • That the event horizon is a part of the gate and not the wormhole is made apparent in 48 hours when Teal'c got stuck in the stargate buffer.
    – a20
    Sep 26, 2021 at 11:13

I happen to be rewatching Season 1 at the moment. A lot of things change from first appearance, like zat'nik'tel disintegration. This is one of them. In Children of the Gods, Apophis and his group of Jaffa actually back right through the still-connected incoming event horizon, both on Earth and Abydos. It's highly likely they were making things up as they went along, especially in the early seasons. I'm making a list of 'rules' and noting discrepancies. I have three already: the CotG wormhole anomaly, Teal'c's growing knowledge of Goa'uld tech that he previously had no idea was more than "magic", and the current anomaly of the dominant Earth-Gate and the DHD - the SGC's Stargate still functions with the Antarctic Gate connected to its DHD.

So while at first it seems to be possible to re-enter and use a wormhole both ways, but eventually that changes.

  • 1
    In the remastered version they fix that and restore a scene where the Jaffa use a portable dialing device to reopen the gate going in the other direction. And also remove some cringe worthy dialog and scenes forced on them by showtime. The showrunners consider the new version canon and fought to make sure they could release it. Jun 27, 2021 at 11:35

If I recall, it tries to send it, but matter sent through the wrong side cannot reintegrate and is just a particle shower on the other side iirc. I think it was explained better in either the early episodes or a really late one.

  • 2
    Pure off-hand speculation isn't that useful as an answer. Maybe you can improve your post by backing up your assessment with a concrete episode or quote?
    – bitmask
    Sep 24, 2012 at 4:59
  • I would like to see a source for this. If this actually were the case, an insect entering the gate from the wrong side would be enough to detonate the gate on the other side, due to the enormous amount of energy contained in mass.
    – a20
    Sep 26, 2021 at 11:16

I know this is an old thread, but it is possible it is using what's know in the telecommunication industry as "Store and forward" which is a telecommunications technique in which information is sent to an intermediate station where it is kept and sent at a later time to the final destination or to another intermediate station. In this case similar to what they did in Atlantis, with the McKay/Carter Intergalactic Gate Bridge. But in this case it has nothing to forward too so the gate simply holds the "data". Again this is just speculation, and I am not a scientist, nor do I play one on TV.

  • But the bridge only involved forwarding data from the front side of the gate. Do you have any evidence that it would work from the back side? Mar 23, 2015 at 15:13
  • @curiousdannii That's the point Pirho is making; that the Gate doesn't know where to send information that enters from the back, so it just keeps it indefinitely (or until the pattern buffer is wiped). This is speculation, but in my opinion it's good speculation Mar 23, 2015 at 15:15
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    @JasonBaker I know that's what Pirho is suggesting. I'm asking whether there's anything to support this speculation. It would be equally plausible to suggest nothing gets buffered from the back side. Unsupported speculations don't really count as good answers and shouldn't be upvoted. Mar 23, 2015 at 15:18

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