They are a mathematical curiosity, not a thing that could actually exist.
If you could rewrite the laws of physics there are lots of cool things you could do, wormholes would just be the start......
Then explain how you conserve energy when you move an item out of a gravity well via a wormhole.
Or the even bigger problem I explain here: https://news.ycombinator.com/item?id=12301781
Consider an obvious example: a wormhole which connects two points on earth separated by 1m of real distance, at the same height.
Theres no violation of conservation of energy because you did not gain or lose gravitational potential energy, and your start and end momentum is conserved.
But that's not what people mean when they say wormhole.
https://en.wikipedia.org/wiki/Kip_Thorne#Wormholes_and_time_...
Wormholes for matter and energy are not incompatible with physics. We just probably won't ever see one like the one he proposed, because creating it would require manipulation of matter or gravity at extreme scale.
But, it is wrong to say it is impossible. It is theoretically possible.
What's there to argue with? He doesn't claim wormholes can exist.
> because creating it would require manipulation of matter or gravity at extreme scale.
Not extreme scale, using a type of energy that doesn't actually exist. i.e. it's not about the quantity of energy, it's the type. It's a mathematical result, not an actual thing.
> But, it is wrong to say it is impossible. It is theoretically possible.
No, it is not possible. See my other replies in this thread.
"...calculations in semiclassical gravity suggest that quantum effects may be able to violate this condition in curved spacetime. Although it was hoped recently that quantum effects could not violate an achronal version of the averaged null energy condition, violations have nevertheless been found, so it remains an open possibility that quantum effects might be used to support a wormhole."
Wormholes are more than likely impossible because to hold one open for travel, you would need some sort of negative matter/negative energy. That isn't forbidden by physics, but it's unlikely that it exists since we haven't seen any. Without negative energy/matter to hold a wormhole open, even if you could create one, just a single proton or electron would cause the wormhole to become unstable and collapse in on itself, and doing so faster than the proton could travel through.
No, it does not. See my more detailed reply here: https://news.ycombinator.com/item?id=12301781
Say you are in a gravity well with one side of the wormhole, and the other side is outside the well.
You could "lift" matter outside the gravity well without spending energy.
There are other problems as well: Gravity has no discontinuities, as objects move, the gravitational field moves with it. You never have a situation where gravity just suddenly shows up. (The same is true for an electrical field BTW - you can never create one, you can only move an existing one (i.e. split up the positive and negative parts). A magnetic field can be created, but that's because you always create a north and south at the same time. If magnetic monopoles existed you could not create just one, you could only separate the two halves.)
Anyway, a wormhole would allow you to have a gravitational discontinuity and that's impossible, it would create a gravitational wave with an infinite frequency. As you know a true square wave is physically impossible - the fourier transform requires an infinite frequency - but that's what you are doing by moving matter via a wormhole.
How is that? Wouldn't the gravitational force just propagate across the wormhole, making for a continuous gravitational gradient?
Maybe we're talking about separate conceptions of what a "wormhole" is here. For one example of what I'm picturing, you could have a one-wormhole universe as a three-dimensional hologram along the surface of a 4D hypertorus. You can go "through the doughnut hole" to get somewhere quicker than you could by going "around the doughnut", but that doesn't mean that there's a discontinuity anywhere on the surface of the hypertorus. Gravitational waves from one point-source would be propagating both "into" the wormhole (along the inside of the doughnut) and "through regular space" (along the outside of the doughnut) and eventually encountering themselves at the destination and maybe constructively or destructively interfering, but they wouldn't be forced into a square wave at any point.
That would be even worse. Let a strong gravitational force go through the wormhole and drop something near it (not through it).
Then move the wormhole (and the gravitational force) elsewhere, lift the object, and bring the wormhole back.
Normally the thing that generates gravity has inertial mass, so it costs energy to move. Not with a wormhole. If you speculate that it should have inertial mass, then how much?
I would think that whatever method you have of moving a mouth of the wormhole, would have some interactions with the masses providing the gravitation.
Also, I'm not 100% sure that a wormhole would not have something like an inherent mass, because iirc there are solutions where a black hole mass is entirely because of the way spacetime is set up, without any particles needed? I'm not sure about that, but I think that is what I read..
Is this a thought experiment you came up with on your own, or do you have a paper you're citing? If the latter, do you have a link?
That would be even worse. Let the strong gravitational force of the Earth go through a wormhole located on a small platform in deep space, and drop a rock near the wormhole (not through the wormhole).
Then move the wormhole (and the gravitational force) elsewhere, lift the rock off the platform, and bring the wormhole back.
A wormhole is in no way a gravitational discontinuity, the toplogy for them is well defined. The creation of a wormhole would be a bit tricky, as this does require a discontinuity, but there's no reason to think that's impossible. After all, a gravitational singularity is also a discontinuity, and physicists have no problem with that.
Here's a concrete example:
https://en.wikipedia.org/wiki/Ellis_wormhole
That's a wormhole with a well-defined metric that satisfies the Einstein field equations.
That would be even worse, I replied to the same thing here: https://news.ycombinator.com/item?id=12301858
> A wormhole is in no way a gravitational discontinuity
A movable one certainly is, and a non movable one doesn't make any sense from a relativity point of view.
> Ellis Wormhole
Did you read your own link? "and there is no gravity"
There's a reason they say that. And there is no place in the universe without gravity. It's a mathematical solution, not a representation of the physical world.
Do you agree that you can't "leave the universe" in the sense of travelling past the information-propagation wavefront of the Big Bang—even in a case where our universe begins to shrink and that wavefront starts to come toward us?
If yes, then a non-movable wormhole can be justified exactly like that: it's part of that same wavefront—part of the topological outer surface of the universe, not an object "in" the universe.
The "no gravity" line there means the stress tensor is zero, and this is a so-called "vacuum solution." Essentially all closed form solutions to the field equations are vacuum solutions because it's almost impossible to write a closed form solution otherwise.
Sorry. The gravitational field of the object you just sent through the wormhole, not the gravitational field of the wormhole itself.
The ultraviolet example is the opposite: The universe acted in a certain way, so we looked for math to match, which happened to have a strange property to it.
Here first we found the strong property and are looking for the universe to match.
You can do the first, but not the second.
The Higgs boson also comes to mind.