A long, thin wormhole, similar to some strange form of optical fibre, could allow us to send light pulses through time.
Wormholes are tunnels that connect two points in space-time, as predicted by Einstein’s general theory of relativity. If something could cross one, it would open up fascinating possibilities like time travel and instant communication.
However, Einstein’s wormholes are notoriously unstable, and they do not remain open long enough for anything to pass through. Kip Thorne of the California Institute of Technology and his colleagues hypothesized in 1988 that wormholes could be kept open by using a type of negative energy known as Casimir energy.
According to quantum mechanics, the vacuum of space-time is teeming with random quantum fluctuations that generate energy waves. Now imagine two parallel metal plates in this vacuum. Because some energy waves are too large to fit between the plates, the amount of energy between them is less than the amount of energy surrounding them. In other words, there is negative energy in the space-time between the plates.
Theoretical attempts to use such plates to keep wormholes open have so far proved untenable. Now Luke Butcher at the University of Cambridge may have found a solution.
“What if the wormhole itself could take the place of the plates?” he says. In other words, under the right conditions, could the wormhole’s tube-like shape generate Casimir energy? His calculations show that if the wormhole’s throat is orders of magnitude wider than its mouth, it does indeed generate Casimir energy at its center.
“Unfortunately, this energy isn’t enough to keep the wormhole stable. It will collapse,” says Butcher. “But the existence of negative energy does allow the wormhole to collapse very slowly.” Further calculations indicate that the wormhole’s center may remain open long enough for a pulse of light to pass through.
A wormhole is a space-time shortcut, so sending a light pulse through one could enable faster-than-light communication. And, because the two mouths of a wormhole can exist at different points in time, a message could theoretically be sent through time.
Butcher warns that much more research is needed to confirm that other parts of the wormhole besides the center remain open long enough for light to pass through. He must also determine whether a pulse large enough to transmit meaningful data can pass through the slowly collapsing throat. And, of course, we are a long way off translating the theoretical equations into a physical object.
“Does this mean we have the technology for building a wormhole?” asks Matt Visser at the Victoria University of Wellington in New Zealand. “The answer is still no.” Still, he is intrigued by Butcher’s work. “From a physics perspective, it may revitalise interest in wormholes.”
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