Wormholes, time travel, white holes, extra spacial dimensions, parallel universes - all arose as solutions to Einstein's equations of general relativity, meaning theoretical physics predicts they should all be likely to exist in the fabric of space-time. But will we ever be able to open a wormhole into space-time to travel towards a parallel universe, and how would we even know if we did? Russian physicist Alexander Shatskiy from the Lebedev Physical Institute argues we have already seen the evidence that indeed parallel universes exist in the gravitational lensing effects that are able to bend light in a unnatural way.
The first prediction of the possibility of traveling to parallel universes was made shortly after Albert Einstein published his Theory of General Relativity. Austrian physicists Ludwig Flamm found that the field equations of general relativity pointed towards the existence of a structure commonly known today as a wormhole, a connection between two regions of space which would permit faster-than-light travel between them. Matter entering one end of the wormhole would immediately exit the other end, at least as long as the wormhole is stable and remains open during the process.
Shatskiy says the only reason why we haven't been able to directly observe wormholes yet is because they are indistinguishable from the black holes. The only problem is that we seem to know more about wormholes than the actual singularity of the black hole. Furthermore, wormholes are though to be extremely unstable, collapsing out of existence as soon as they form. A way to keep a wormhole open for an indefinite amount of time would involve the use of exotic matter, presenting negative energy and mass.
Ordinary matter has positive energy and mass, meaning that massive objects such as black holes bend light through gravitational lensing much in the same way a optical lens would do here on Earth. However, the unique characteristics of the exotic matter would have the exact opposite effect, deflecting light as it passes through a wormhole from a universe to another. Thus, if a star would shine light into a wormhole, at the other end it would emerge in a divergent pattern to form a bright ring of light.
By detecting such signatures, one might point towards the existence of wormhole. The problem is that black holes and large mass accumulations also have the capability of forming rings of light through the gravitational lensing effect, the well known Einstein rings. While Lawrence Krauss from the Case Western Reserve University seems to appreciate Shatskiy's theoretical study, by pointing out the immense effort made by the Russian physicist to find the signature of real wormholes, critics add that Shatskiy avoided to specify the characteristics of the required exotic matter, and even the basic interactions with light.
Furthermore, it is not known yet if exotic matter even exists, but, even if it does, the signature proposed by Shatskiy is indistinguishable from a series of other signatures routinely detected throughout the universe. They do not dispute the fact that wormholes might exist, but they argue that such a possibility is extremely remote.