I have HRG in mind for this thread but obviously, fair game for everyone. Warning....if you haven't seen Avengers: Endgame, and don't want spoilers, stop reading now. I figure enough time has passed since that movie came out that I don't feel bad talking about it here.

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Ok, so in the movie, the six infinity stones (soul stone, reality stone, space stone, time stone, mind stone, and power stone) were formed at the beginning of the universe. Thanos collects them all and with the combined power, snaps half the living things out of existence. In Endgame, they are trying to undo this snap. One of the ways they do it is by going back in time to where they first run across the various stones.

Time travel inherently presents theoretical problems, and there have typically been two ways of dealing with it. First, there's just one timeline, and every time you move backward or forward in time, it's along that same timeline. Which means that if you go back in the past and affect something, it will have repercussions in the future. One obvious problem is that you could go back in time and accidentally impact your own existence. Back to the Future addresses time travel this way, as Marty McFly accidentally interfered with his father and mother getting together, and so much of the movie is spent with him trying to make that happen. He succeeds in a way that turns his father from a bumbling stooge into a confident, successful man, so when Marty goes back to 1985 (his original time), not only does he and his family exist, but they are wildly successful and the tables are turned on antagonist Biff.

But Endgame approaches time travel differently. Instead of being one timeline, there are multiple. Every time they go back in time, it launches a new timeline - a new universe, as it were. So Captain America ends up running into, and fighting, himself at one point. Meaning there were, at that junction of space-time, two Captain Americas there. Suppose the Cap that went back in time got stuck there...forever on that timeline there would have been two Captain Americas living in that world, and none in the original world.

In that scene, Loki ends up grabbing the tesseract, which houses one of the infinity stones (the space stone). And then he disappears. We do not know where he went. But let's say that these stones are used to transport someone back in time, even just 30 minutes. 30 minutes prior, the infinity stones existed, but now an entirely "new" group of infinity stones have been transported to that point in time from 30 minutes into the future. So the original timeline now has zero infinity stones, but the world of 30 minutes prior suddenly has...two complete sets of infinity stones. How is THAT supposed to work? Let's say Thanos has all the infinity stones and goes back in time 30 minutes. Now there are two Thanos' back in that alternative timeline, and two full sets of infinity stones. Then let's say he goes back one minute again - that also opens up a different timeline, and now there are THREE sets of infinity stones. Let's say he keeps doing this, incrementally back in time. There could theoretically be thousands of Thanos' with thousands of complete sets of infinity stones. Given that these stones harnessed the fundamental aspects of the universe, it would seem impossible for there to be multiple sets of these stones - after all, which power stone, for example, is the most powerful? Theoretically, Thanos could do this trillions of times, then collect all the sets of infinity stones, and travel back to his original timeline, and distribute infinity stones to trillions of people. Most of them wouldn't be powerful enough to wield them, but still.

Now, here's the real problem. The combined set of these infinity stones is so powerful that its user could theoretically snap the universe out of existence. So if Thanos went back in time and used his infinity stones to snap another universe (the alternative timeline) out of existence, Since the universes are now connected - via Thanos' time travel, which must have created some portal, some tunnel, between the two - why wouldn't such a snap destroy BOTH universes, BOTH timelines?

All of this is to say....there are fundamental problems with the idea of a multiverse. Either they are completely disconnected realities or they are connected somehow. If they are completely disconnected, then we have no way of knowing anything about them. If they are connected, then there has to be a way for us - theoretically - to travel back and forth between them, and for one universe to influence another, and so what happens in one universe can impact another in the multiverse.

HRG - help us understand this better!

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Ok, so in the movie, the six infinity stones (soul stone, reality stone, space stone, time stone, mind stone, and power stone) were formed at the beginning of the universe. Thanos collects them all and with the combined power, snaps half the living things out of existence. In Endgame, they are trying to undo this snap. One of the ways they do it is by going back in time to where they first run across the various stones.

Time travel inherently presents theoretical problems, and there have typically been two ways of dealing with it. First, there's just one timeline, and every time you move backward or forward in time, it's along that same timeline. Which means that if you go back in the past and affect something, it will have repercussions in the future. One obvious problem is that you could go back in time and accidentally impact your own existence. Back to the Future addresses time travel this way, as Marty McFly accidentally interfered with his father and mother getting together, and so much of the movie is spent with him trying to make that happen. He succeeds in a way that turns his father from a bumbling stooge into a confident, successful man, so when Marty goes back to 1985 (his original time), not only does he and his family exist, but they are wildly successful and the tables are turned on antagonist Biff.

But Endgame approaches time travel differently. Instead of being one timeline, there are multiple. Every time they go back in time, it launches a new timeline - a new universe, as it were. So Captain America ends up running into, and fighting, himself at one point. Meaning there were, at that junction of space-time, two Captain Americas there. Suppose the Cap that went back in time got stuck there...forever on that timeline there would have been two Captain Americas living in that world, and none in the original world.

In that scene, Loki ends up grabbing the tesseract, which houses one of the infinity stones (the space stone). And then he disappears. We do not know where he went. But let's say that these stones are used to transport someone back in time, even just 30 minutes. 30 minutes prior, the infinity stones existed, but now an entirely "new" group of infinity stones have been transported to that point in time from 30 minutes into the future. So the original timeline now has zero infinity stones, but the world of 30 minutes prior suddenly has...two complete sets of infinity stones. How is THAT supposed to work? Let's say Thanos has all the infinity stones and goes back in time 30 minutes. Now there are two Thanos' back in that alternative timeline, and two full sets of infinity stones. Then let's say he goes back one minute again - that also opens up a different timeline, and now there are THREE sets of infinity stones. Let's say he keeps doing this, incrementally back in time. There could theoretically be thousands of Thanos' with thousands of complete sets of infinity stones. Given that these stones harnessed the fundamental aspects of the universe, it would seem impossible for there to be multiple sets of these stones - after all, which power stone, for example, is the most powerful? Theoretically, Thanos could do this trillions of times, then collect all the sets of infinity stones, and travel back to his original timeline, and distribute infinity stones to trillions of people. Most of them wouldn't be powerful enough to wield them, but still.

Now, here's the real problem. The combined set of these infinity stones is so powerful that its user could theoretically snap the universe out of existence. So if Thanos went back in time and used his infinity stones to snap another universe (the alternative timeline) out of existence, Since the universes are now connected - via Thanos' time travel, which must have created some portal, some tunnel, between the two - why wouldn't such a snap destroy BOTH universes, BOTH timelines?

All of this is to say....there are fundamental problems with the idea of a multiverse. Either they are completely disconnected realities or they are connected somehow. If they are completely disconnected, then we have no way of knowing anything about them. If they are connected, then there has to be a way for us - theoretically - to travel back and forth between them, and for one universe to influence another, and so what happens in one universe can impact another in the multiverse.

HRG - help us understand this better!

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