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Illustration of matter pouring into a black hole, crossing the Einstein-Rosen Bridge and emerging into another region of the universe. |Image credit: Robert Lea (created using Canva)
This article was originally published on conversation. The publication contributed this article to Space.com Expert Voices: Columns and Insights.
wormhole People often think of it as a tunnel through space or time—a shortcut across the universe. But this image is based on a misunderstanding of the work of physicists Albert Einstein and Nathan Rosen.
In 1935, while studying the behavior of particles in extreme gravity, Einstein and Rosen Introducing what they call “Bridges”: the mathematical connection between two perfectly symmetrical copies time and space. It is not intended as a passage for travel, but as a means maintain consistency Between gravity and quantum physics. It was not until later that the Einstein-Rosen bridge was associated with wormholes, although it had little to do with the original idea.
But in new researchmy colleagues and I showed that the original Einstein-Rosen bridge pointed to something stranger and more fundamental than wormholes.
The puzzle that Einstein and Rosen were trying to solve was never about space travel, but about how quantum fields behave in curved space-time. Interpreted this way, the Einstein-Rosen Bridge is like a mirror in space-time: a connection between two microscopic arrows of time.
Quantum mechanics governs nature at the smallest scales, such as particles, and Einstein’s general relativity Applies to gravity and spacetime. Reconciling the two remains one of physics’ most profound challenges. Excitingly, our reinterpretation may provide a pathway to achieve this goal.
A misunderstood legacy
The “wormhole” explanation emerged decades after the work of Einstein and Rosen, when physicists speculated on traveling from one side of space-time to the other, Most notably, research in the late 1980s.
But these analyzes also make clear the speculative nature of the idea: In general relativity, such journeys are prohibited. The bridge shrinks faster than light can pass through it, making it impossible to pass. Therefore, the Einstein-Rosen bridge is unstable and unobservable—a mathematical structure, not a portal.
Nonetheless, the wormhole metaphor is prevalent in popular culture and speculative theoretical physics. The idea is black hole Possibly connecting distant regions of the universe—or even serving as time machine — has inspired countless essays, books and films.
However, there is no observational evidence of macroscopic wormholes, nor any compelling theoretical reason to expect them in Einstein’s theory. While speculative extensions of physics—e.g. strange forms of matter or Modifications to General Relativity – Support for such structures has been proposed, but they remain untested and highly speculative.
Artist’s interpretation of using a wormhole to travel through space. |Image source: NASA
two arrows of time
Our recent work builds on ideas proposed by Sravan Kumar and João Marto to revisit the Einstein-Rosen bridge puzzle using modern quantum time interpretations.
most basic laws of physics There is no distinction between past and future, no distinction between left and right. If time or space in the equation is reversed, the law still holds. Taking these symmetries seriously leads to different interpretations of the Einstein-Rosen bridge.
Rather than a tunnel through space, it can be understood as two complementary components of a quantum state. One, time flows forward; on the other hand, it flows backward from the position of mirror reflection.
This symmetry is not a philosophical preference. Once infinity is ruled out, quantum evolution must remain intact and reversible at the microscopic level—even in the presence of gravity.
“Bridge” expresses the fact that two time components are required to describe a complete physical system. In the ordinary case, physicists ignore the time-reversed part by choosing a single arrow of time.
But near a black hole, or in an expanding and collapsing universe, both directions must be included in order to obtain a consistent quantum description. It is here that the Einstein-Rosen Bridge naturally appears.
Solving the information paradox
On a microscopic level, the bridge allows information to pass between objects that appear to us. event horizon – A point of no return. Information does not disappear; it continues to evolve, but in an opposite, mirroring direction of time.
This framework provides a natural solution to the famous black hole information paradox. 1974 Stephen Hawking show Black holes radiate heat and eventually evaporate, apparently erasing any information that falls into the black hole—contradicting the quantum principle that evolution must preserve information.
This paradox only arises if we insist on using a single, one-way arrow of time extrapolating to infinity to describe the horizon—an assumption that quantum mechanics itself does not require.
If a complete quantum description includes both time directions, nothing is really lost. Information leaves our direction of time and reappears in the opposite direction. Integrity and causality are preserved without introducing exotic new physics.
These ideas are difficult to understand because we are macroscopic organisms that experience only one direction of time. On a day-to-day scale, disorder, or entropy, tends to increase. Highly ordered states naturally evolve into disordered states, not the other way around. This gives us an arrow of time.
But quantum mechanics allows for more subtle behavior. Interestingly, evidence of such hidden structures may already exist. Cosmic Microwave Background Radiation – Afterglow big Bang — Shows subtle but persistent asymmetry: Preference for one spatial direction over its mirror image.
The anomaly has baffled cosmologists for two decades. The Standard Model gives it an extremely low probability—unless a mirror quantum component is included.
An echo of a previous universe?
This picture naturally connects to deeper possibilities. What we call the “Big Bang” may not be the absolute beginning, but a bounce – a quantum transition between two time-reversed phases of the universe’s evolution.
In this case, the black hole could serve as a bridge not only between directions in time, but also between different cosmic epochs. our universe Could be the inside of a black hole Formed in another parent universe. This may have formed as a closed region of space-time collapsed, rebounded, and began to expand, much like the universe we observe today.
If this diagram is correct, it also provides a way to look at decisions. Relics of the pre-bounce phase—such as smaller black holes—could survive the transition and reappear in our expanding universe. In fact, some of the invisible stuff we think of as dark matter may be made of such relics.
In this view, the Big Bang evolved from conditions of previous contraction. Wormholes are not necessary: the bridge is in time, not space—the Big Bang becomes a portal, not a beginning.
This reinterpretation of the Einstein-Rosen Bridge offers no shortcuts across galaxies, no time travel, no science fiction wormholes or Hyperspace. What it offers is much deeper. It provides a consistent quantum picture of gravity, in which spacetime embodies a balance between opposite directions in time, and in which our universe may have had a history before the Big Bang.
It didn’t overturn Einstein’s theory of relativity or quantum physics – it perfected them. The next revolution in physics may not get us faster than light, but it may reveal that, deep in the microscopic world and in the bouncing universe, time flows in both directions.
