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<blockquote data-quote="freyar" data-source="post: 6636906" data-attributes="member: 40227">Gravitational time dilation isn't only found near singularities or extremely high curvature.&nbsp; In fact, it's measurable even in the weak gravity of the earth --- GPS units have to account for it.&nbsp; Generically, meaning except in extremely special circumstances, there should be some degree of time dilation, and usually we expect weird situations to include some fairly substantial But I'll freely admit that I didn't look up any wormhole metrics before making that statement, so I went and looked just now.&nbsp; One thing I found was a pedagogical paper by Michael Morris and Kip Thorne, who seem to have pushed the serious study of wormholes in the late 20th century.&nbsp; They make a point of analyzing precisely how to reduce time dilation effects --- since that also reduces tidal forces.&nbsp; There are indeed wormhole solutions with no time dilation, but they have &quot;exotic matter&quot; everywhere.&nbsp; We live in a universe without much exotic matter, so a realistic wormhole solution requires matching onto a long-distance solution with normal matter.&nbsp; Then you do get time dilation.&nbsp; If you want to keep time dilation effects small and the exotic matter localized to the wormhole itself, you need a wormhole that's about 600 AU across.&nbsp; Given that the exotic matter needed to create these things is pretty rare, naturally-occurring wormholes would seem likely to have significant time dilation effects.&nbsp; On the other hand, maybe an advanced civilization could construct one without much time dilation.That's of course depending on whether exotic matter with precisely the right properties to make wormholes exists.&nbsp; It's certainly possible to violate the energy conditions that might look like they forbid exotic matter; indeed, some kinds exotic matter of that type looks to be perfectly fine.&nbsp; But other types of exotic matter seem to cause mathematical inconsistencies, so I can't say about what's needed for wormholes.&nbsp; Morris &amp; Thorne also note that wormholes of the type they study are also necessarily time machines, so that may or may not be a clue that they're not allowed.It's also worth noting that the Morris-Thorne wormholes and the eternal black hole wormholes (called Einstein-Rosen bridges) don't connect two points on the same part of space.&nbsp; They connect two different parts of space.&nbsp; In other words, I travel from earth to a wormhole, go through the wormhole, then travel to planet X.&nbsp; If I want to get back to earth, I can't go the &quot;long way around,&quot; I have to go through the wormhole (or some wormhole) again.</blockquote>

[QUOTE="freyar, post: 6636906, member: 40227"] Gravitational time dilation isn't only found near singularities or extremely high curvature. In fact, it's measurable even in the weak gravity of the earth --- GPS units have to account for it. Generically, meaning except in extremely special circumstances, there should be some degree of time dilation, and usually we expect weird situations to include some fairly substantial But I'll freely admit that I didn't look up any wormhole metrics before making that statement, so I went and looked just now. One thing I found was a pedagogical paper by Michael Morris and Kip Thorne, who seem to have pushed the serious study of wormholes in the late 20th century. They make a point of analyzing precisely how to reduce time dilation effects --- since that also reduces tidal forces. There are indeed wormhole solutions with no time dilation, but they have "exotic matter" everywhere. We live in a universe without much exotic matter, so a realistic wormhole solution requires matching onto a long-distance solution with normal matter. Then you do get time dilation. If you want to keep time dilation effects small and the exotic matter localized to the wormhole itself, you need a wormhole that's about 600 AU across. Given that the exotic matter needed to create these things is pretty rare, naturally-occurring wormholes would seem likely to have significant time dilation effects. On the other hand, maybe an advanced civilization could construct one without much time dilation. That's of course depending on whether exotic matter with precisely the right properties to make wormholes exists. It's certainly possible to violate the energy conditions that might look like they forbid exotic matter; indeed, some kinds exotic matter of that type looks to be perfectly fine. But other types of exotic matter seem to cause mathematical inconsistencies, so I can't say about what's needed for wormholes. Morris & Thorne also note that wormholes of the type they study are also necessarily time machines, so that may or may not be a clue that they're not allowed. It's also worth noting that the Morris-Thorne wormholes and the eternal black hole wormholes (called Einstein-Rosen bridges) don't connect two points on the same part of space. They connect two different parts of space. In other words, I travel from earth to a wormhole, go through the wormhole, then travel to planet X. If I want to get back to earth, I can't go the "long way around," I have to go through the wormhole (or some wormhole) again. [/QUOTE]

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