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Comment by pythonlion | Hacker News Reader

It is a hole through space, not through time. Am i right?

From the abstract of the Nature article linked by @comboy below (http://www.nature.com/articles/srep12488):

> the magnetic field from a source at one end of the wormhole appears at the other end as an isolated magnetic monopolar field, creating the illusion of a magnetic field propagating through a tunnel outside the 3D space.

Seems that there's no actual tunneling, just the illusion of tunneling.

The article is in the journal Scientific Reports, not Nature. Nature Publishing Group is the publisher of that journal.

Also, note that Scientific Reports has no requirements for a paper to be super-novel/cool/hot topic, in contrast to the actual Nature journal. Anything which is decent science will get published in SRep; it's NPG's version of PLOS One.

It seems Nature's strategy is working here, since many news outlets and the general public don't seem to be aware of the difference.

Relativity actually tells us what real "holes in space" do. I'm not kidding. And the answer is that they explode as they collapse, releasing massive amounts of energy as the vacuum is disturbed, because any macroscopic spatial distortion is massively, massively energetic, in the sense where all my uses of the word "massive" is not actually metaphorical. Explosions equivalent to rather enormous amounts of mass, as energy.

No, there's no hole through space here.

How would you do a calculation on that (energy from collapsing hole through spacetime)? I've googled to get somewhere but I can't find anything useful.

When taking General Relativity I did that calculation as part of the take-home exam. It's mostly a matter of calculating the curvature tensor of a wormhole and finding that it is freaky, so the energy-momentum tensor that would satisfy the Einstein equation would need to include negative energy and/or momentum (the Einstein equation basically says curvature tensor = energy tensor(1)). Then exactly how the thing would unravel is a matter of computation, but unravel it would.

Or one could presumably find a form of matter that has negative energy density and start building wormholes.

1) The energy tensor has energy as the time diagonal value, and momentum as the space diagonal values.

Protip: googling for the energy required to create such a wormhole is a better solution. That lands you on this BBC story[1] where they've interviewed well-known physicists, and state that

"As a very rough approximation, you would need the energy the sun produces over 100 million years to make a wormhole about the size of a grapefruit."

[1] http://www.bbc.com/future/story/20140326-will-we-ever-travel...

So approximately the energy equivalent of the mass of 2 earths.

Seems doable.

Ianahep, but maybe work backwards from gravity vs spacetime equations? I'm assuming gravity is the exchange mechanism that drives this, so if you needed x gravitational field to produce y displacement, then given y displacement you have some energy equivalent of x in mass?

A starting point is "stress-energy tensor" as a keyword to search.

Depends what you mean by a "hole through space"? Yes, its a physical passageway that itself consumes space, like a physical tunnel you would drive your car though. The magnetic field is traveling through space, through a shielded device that also takes up space.

Think of this like Fiber Optics, they are "wormholes" for light, or Electronic wires, they are "wormholes" for electricity. The wormhole is just a metaphor for the illusion.

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