Wormholes
Definition: A Wormhole is a hypothetical cosmic object that is considered as a shortcut between two similar dimensional points (By this, I mean that a wormhole connects two distinct points in one universal space, time or two different universes. I will come to this point later as I have a different opinion in the above statement that is the generally accepted one).
A Brief History of Wormholes
Wormholes were first theorized in 1916, though that wasn't what they were called at the time. While reviewing another physicist's solution to the equations in Albert Einstein's theory of general relativity, Austrian physicist Ludwig Flamm realized another solution was possible. He described a "white hole,"(what we call today as a wormhole) a theoretical time reversal of a black hole. Entrances to both black and white holes could be connected by a space-time conduit.
In 1935, Einstein and physicist Nathan Rosen used the theory of general relativity to elaborate on the idea, proposing the existence of "bridges" through space-time. These bridges connect two different points in space-time, theoretically creating a shortcut that could reduce travel time and distance. The shortcuts came to be called Einstein-Rosen bridges, or wormholes.
Wormholes were first studied mathematically in relativity as early as 1921 by the German mathematician Herman Weyl. However it wasn’t until Thorne began studying them in the 1980s that they started to be taken seriously by relativists. Thorne’s friend Carl Sagan, one of the great popularisers of science of the twentieth century, was working on a science fiction novel Contact, which was later turned into a Hollywood movie. Sagan wanted to feature wormholes in the novel, so asked his friend Kip Thorne to look at wormhole solutions to Einstein’s equations. Shortly after, Thorne proposed the idea of a traversable wormhole that would allow an explorer to travel through a wormhole in both directions from one part of the universe to another very quickly. A whole new area of physics research was spawned.
Till now, only one type of wormhole is discovered (calculated would be more appropriated though). It’s called the Einstein Rosen Bridge (because it is the only kind of wormhole till known till now, many times, wormholes are only called as Einstein Rosen Bridge. Sometimes, it’s a misconception though).
The name wormhole is derived from the behavior of a worm taking a shortcut through the bulk of an apple to get to its opposite side.
The Wormhole Theory
We might imagine a 2D wormhole as a tunnel or passage between two points on a curved flat land also termed as hyperspace. A full three dimensional wormhole would have entrances and exits that are three dimensional spheres rather than two dimensional rings like the mouths of the tube. Such lower dimensional, humanfriendly, visualizations are termed embedding diagrams, and the iconic wormhole image is usually shown as the well known Schwarzchild embedding diagram, which is the wormhole for a static, non-rotating, Schwarzchild black hole. The tunnel might be a straight stretch, but it could also wind around, taking a longer path than a conventional rout might require. An observer passing through such a wormhole could, in principle, traverse the wormhole in less time than it would take to travel from point A to point B through normal space-time outside the wormhole. Moreover, if A and B are sufficiently distant in space and the wormhole length is sufficiently short, an observer could potentially traverse the wormhole in a time less than it would take to send a light signal from A to B through normal space. Wormholes could thus be used as a cosmic wonder to effectively bypass the limitation that no object can travel faster than the speed of light in special and general relativity. Faster than light travel itself presents many paradoxes, since it could be used to send messages and information back in time. Certain other uses of wormholes could also potentially allow observers themselves to travel into the past.
A Brief History of Wormholes
Wormholes were first theorized in 1916, though that wasn't what they were called at the time. While reviewing another physicist's solution to the equations in Albert Einstein's theory of general relativity, Austrian physicist Ludwig Flamm realized another solution was possible. He described a "white hole,"(what we call today as a wormhole) a theoretical time reversal of a black hole. Entrances to both black and white holes could be connected by a space-time conduit.
In 1935, Einstein and physicist Nathan Rosen used the theory of general relativity to elaborate on the idea, proposing the existence of "bridges" through space-time. These bridges connect two different points in space-time, theoretically creating a shortcut that could reduce travel time and distance. The shortcuts came to be called Einstein-Rosen bridges, or wormholes.
Wormholes were first studied mathematically in relativity as early as 1921 by the German mathematician Herman Weyl. However it wasn’t until Thorne began studying them in the 1980s that they started to be taken seriously by relativists. Thorne’s friend Carl Sagan, one of the great popularisers of science of the twentieth century, was working on a science fiction novel Contact, which was later turned into a Hollywood movie. Sagan wanted to feature wormholes in the novel, so asked his friend Kip Thorne to look at wormhole solutions to Einstein’s equations. Shortly after, Thorne proposed the idea of a traversable wormhole that would allow an explorer to travel through a wormhole in both directions from one part of the universe to another very quickly. A whole new area of physics research was spawned.
Till now, only one type of wormhole is discovered (calculated would be more appropriated though). It’s called the Einstein Rosen Bridge (because it is the only kind of wormhole till known till now, many times, wormholes are only called as Einstein Rosen Bridge. Sometimes, it’s a misconception though).
The name wormhole is derived from the behavior of a worm taking a shortcut through the bulk of an apple to get to its opposite side.
The Wormhole Theory
We might imagine a 2D wormhole as a tunnel or passage between two points on a curved flat land also termed as hyperspace. A full three dimensional wormhole would have entrances and exits that are three dimensional spheres rather than two dimensional rings like the mouths of the tube. Such lower dimensional, humanfriendly, visualizations are termed embedding diagrams, and the iconic wormhole image is usually shown as the well known Schwarzchild embedding diagram, which is the wormhole for a static, non-rotating, Schwarzchild black hole. The tunnel might be a straight stretch, but it could also wind around, taking a longer path than a conventional rout might require. An observer passing through such a wormhole could, in principle, traverse the wormhole in less time than it would take to travel from point A to point B through normal space-time outside the wormhole. Moreover, if A and B are sufficiently distant in space and the wormhole length is sufficiently short, an observer could potentially traverse the wormhole in a time less than it would take to send a light signal from A to B through normal space. Wormholes could thus be used as a cosmic wonder to effectively bypass the limitation that no object can travel faster than the speed of light in special and general relativity. Faster than light travel itself presents many paradoxes, since it could be used to send messages and information back in time. Certain other uses of wormholes could also potentially allow observers themselves to travel into the past.
Time machines are unavoidable in our physical dimensional spacetime, Traversable wormholes imply time machines, and the prediction of wormholes spawned a number of follow-on research efforts on time machines.
Both general-relativity theory and quantum theory appear to offer several possibilities for traveling along what is called as a closed, time like curve or a path that cuts through time and space ,essentially, a time machine.
In addition to facilitating effectively faster than light travel, wormholes could potentially be used as time machines, in the following sense first developed by Caltech theoretical physicist Kip Thorne. Imagine an advanced technology capable of creating, manipulating, and containing both ends of a stable, traversible, wormhole. Place one end in a laboratory on Earth and the other on a spacecraft capable of traveling through space at some reasonable fraction of the speed of light. Imagine the wormhole connecting the lab and spaceship is created in some future year, say 2500. Now keep one end on Earth and send the spaceship off in any direction at some appreciable fraction of the speed of light for a finite duration after which it will decelerate, turn around, come back to Earth, and stop, so the wormholes ends are brought back together. Relativity tells us that the clocks of observers left on Earth and those in a relativistically moving spacecraft will begin to differ by an amount that depends on the speed of the craft. Since moving clocks run slow in relativity, a spaceship observer might experience a short subjective duration of say, a few weeks, but thousands or millions of years could pass in the external universe depending on how fast they were traveling. In this sense, time travel to the future is easy, and does not require wormholes, just a ship capable of moving at relativistic speeds. A spaceship executing the above maneuver might find itself thousands or millions of years in the future after stopping. Yet an observer at the wormhole mouth in the laboratory on Earth would still have its clock synchronized with the shipboard wormhole. If the ship finds itself, say in year 3500, after returning to Earth, any observers on the ship could return to the year 2500, traveling 1000 years into the past, simply by stepping through their shipboard wormhole back into the laboratory on Earth. In this way, wormholes could theoretically be used to travel into the past. However, in this case, the shipboard time travelers could never travel to before the year 2500. This poses a striking answer to the question, "If time travel to the past is possible, how come we aren't being constantly visited by time travelers from the future?" For these types of wormhole time machines, the answer is simply, because they haven't been invented yet! Time travel of this sort can never take an observer back to before the original date when the wormhole connection was set up. This is a particularly clever resolution to an interesting time travel paradox (I know I am not very clear here, but just try to get the idea if u didn’t understand completely) But, at the same time we should see that, that way, the vehicle doesn't actually break the rule of the universal speed limit because the ship never actually travels at a speed faster than light. It just takes a shortcut.
However, turning a wormhole into a time machine won't be easy. It would take a Herculean effort to turn a wormhole into a time machine. It's going to be tough enough to pull off a wormhole.
That's because once a wormhole is created, one or both ends of it would need to be accelerated through time to the desired position, according to general relativity theory.
Science fiction is filled with tales of traveling through wormholes. But the reality of such travel is more complicated, and not just because we've yet to spot one.
The first problem is size. Primordial wormholes are predicted to exist on microscopic levels, about 10^-33 centimeters. However, as the universe expands, it is possible that some may have been stretched to larger sizes.
Another problem comes from stability. The predicted Einstein-Rosen wormholes would be useless for travel because they collapse quickly.
General relativity can't account for exotic matter ,according to general relativity, exotic matter can't exist. But exotic matter does exist. That's where quantum theory comes in. Like general relativity, quantum theory is a system for explaining the universe, kind of like a lens through which scientists observe the universe.
However, exotic matter has only been observed in very small amounts ,not nearly enough to hold open a wormhole. Physicists would have to find a way to generate and harness large amounts of exotic matter if they hope to achieve this quasi-faster-than-light travel and, by extension, time travel.
Furthermore, other physicists have used quantum mechanics to posit that trying to travel through a wormhole would create something called a quantum back reaction.
In a quantum back reaction, the act of turning a wormhole into a time machine would cause a massive buildup of energy, ultimately destroying the wormhole just before it could be used as a time machine.
However, the mathematical model used to calculate quantum back reaction only takes into account one dimension of spacetime.
The Mathematics Behind Wormholes
Einstein’s equation allows us to solve for the metric of our spacetime, although we’ve already seen that this is typically a very difficult procedure. In Thorne’s 1988 paper, Wormholes in spacetime and their use for interstellar travel, he turned this procedure on its head. Instead of inputting matter into the equation and solving for the metric, he inserted the metric describing a wormhole into the left hand side of Einstein’s equation, and then derived conditions for the matter that would be required to create this wormhole. This is a much simpler procedure since we no longer need to solve a complicated set of coupled partial differential equations.
Thorne and his graduate student Mike Morris proposed what is now called the Morris-Thorne metric, which is given in spherical polar coordinates by:
This metric describes two separate regions of universe, connected by a tube. These different regions can either be interpreted as two separate universes, or the same universe at a different place in time and space. The function b(r) describes the shape of the wormhole, and the throat of the wormhole, where the two different parts of the universe are connected, is located at r0 where b(r0)=r0. This function has to obey a condition called the flare out condition, b′(r)<1, which ensures that the throat remains open.
This equation (Einstein’s field equation) describes how matter bends spacetime and how spacetime tells matter what to do. It has many solutions. Among them, solutions that describe wormholes.
My Theory
So, I think I will now just start about what I think is possible. I don’t know if people have ever thought of it before or not, but it seems more likely that this is thought by many people before but somehow, found out the mistake in it and left it as its too simple.
Ok, Back to the definition. It says that a wormhole can connect any two points in space, time or even two different universes. Now, here is my controversy.
As per the MWI (Many Worlds Interpretation) Theory, there are many different universes (some anonymous scientist calculated that there are currently around 10^500 universes present) with different laws of physics that govern them (some have totally opposite laws of physics than us). But the wormhole theory states that it can connect even these universes. Surely, if these universes are connected by a open, freely permeable wormhole, than the region around it would have a totally different physics than that in both the universes. This scenario is so complex to imagine and understand that, I think, we might prefer to take a more easy-to-understand scenario. This is a simple solution.
The freely permeable mouth of the wormhole should be covered with a kind of membrane that will allow only organic matter and bosons to pass through it. It will be a kind of semi permeable or more probably selectively permeable membrane. This would indeed solve many problems (but even create some, especially, with mathematics and higher dimensions).
Another case where this could be applicable is with time. The definition also states that wormholes can connect two points in time, but a freely permeable wormhole would not be able to do it sensibly. Mainly, due to the thermal difference in the past (or future) and present.
Do Wormholes Actually Exist?
Wormholes may still be incredibly speculative objects, and the technology required to build one is far beyond anything human civilisation would be capable of for many millennia. But studying them has been a very fruitful area of research for physicists exploring the mathematical properties of general relativity. Pushing a theory to its limit and looking at extreme examples allows us to explore where a theory might break down. Usually the ideas of science fiction are inspired by cutting-edge physics; this is a fascinating area where science fiction has inspired a whole new exciting field of cutting edge research.
No observational evidence for wormholes currently exists, but mathematical solutions describing wormholes have long been known to be valid theoretical solutions to Einstein's field equations of General Relativity. However, wormholes made completely of normal matter with positive energy density would be inherently unstable, and would be likely to collapse in the presence of nearby matter or matter that tried to traverse the wormhole. However, stable, traversible wormholes could exist if their entrances and exits were held open by exotic matter with a negative energy density. Examples of such exotic matter include the quantum field configuration responsible for the Casimir Effect in quantum field theory. Whether such exotic matter could occur naturally in high enough densities to permit a stable wormhole to form via ordinary physical processes or whether it could be created artificially with sufficiently advanced technology remain open theoretical questions. Astronomers and astrophysicists are actively speculating about how to test for the existence of wormholes observationally. If they exist, perhaps some objects currently thought to be black holes are actually wormholes. Because the metric describing how space-time distances and durations are computed would be different outside of certain kinds of black holes and wormholes, observations could potentially distinguish between the two by observing how gas and dust emits light as it orbits close to a candidate compact object. Observers could also use the way that light from background stars is gravitationally lensed if a wormhole passes between it and us along our line of sight, since this is potentially different than the lensing caused by a black hole. Still, the spatial resolution required to observationally distinguish between black holes and wormholes is currently beyond our capabilities, which would likely require future generations technologies such as constellations of coordinated, space based, radio telescopes that use very long baseline interferometry in order to probe spatial scales as small as the innermost stable orbit or the event horizon of the black hole, to see if space-time and matter behave as expected for certain kinds of black holes or wormholes. Needless to say, if wormholes are ever discovered observationally, Nobel prizes are certain to be on the horizon !
My Theory
So, I think I will now just start about what I think is possible. I don’t know if people have ever thought of it before or not, but it seems more likely that this is thought by many people before but somehow, found out the mistake in it and left it as its too simple.
Ok, Back to the definition. It says that a wormhole can connect any two points in space, time or even two different universes. Now, here is my controversy.
As per the MWI (Many Worlds Interpretation) Theory, there are many different universes (some anonymous scientist calculated that there are currently around 10^500 universes present) with different laws of physics that govern them (some have totally opposite laws of physics than us). But the wormhole theory states that it can connect even these universes. Surely, if these universes are connected by a open, freely permeable wormhole, than the region around it would have a totally different physics than that in both the universes. This scenario is so complex to imagine and understand that, I think, we might prefer to take a more easy-to-understand scenario. This is a simple solution.
The freely permeable mouth of the wormhole should be covered with a kind of membrane that will allow only organic matter and bosons to pass through it. It will be a kind of semi permeable or more probably selectively permeable membrane. This would indeed solve many problems (but even create some, especially, with mathematics and higher dimensions).
Another case where this could be applicable is with time. The definition also states that wormholes can connect two points in time, but a freely permeable wormhole would not be able to do it sensibly. Mainly, due to the thermal difference in the past (or future) and present.
Do Wormholes Actually Exist?
Wormholes may still be incredibly speculative objects, and the technology required to build one is far beyond anything human civilisation would be capable of for many millennia. But studying them has been a very fruitful area of research for physicists exploring the mathematical properties of general relativity. Pushing a theory to its limit and looking at extreme examples allows us to explore where a theory might break down. Usually the ideas of science fiction are inspired by cutting-edge physics; this is a fascinating area where science fiction has inspired a whole new exciting field of cutting edge research.
No observational evidence for wormholes currently exists, but mathematical solutions describing wormholes have long been known to be valid theoretical solutions to Einstein's field equations of General Relativity. However, wormholes made completely of normal matter with positive energy density would be inherently unstable, and would be likely to collapse in the presence of nearby matter or matter that tried to traverse the wormhole. However, stable, traversible wormholes could exist if their entrances and exits were held open by exotic matter with a negative energy density. Examples of such exotic matter include the quantum field configuration responsible for the Casimir Effect in quantum field theory. Whether such exotic matter could occur naturally in high enough densities to permit a stable wormhole to form via ordinary physical processes or whether it could be created artificially with sufficiently advanced technology remain open theoretical questions. Astronomers and astrophysicists are actively speculating about how to test for the existence of wormholes observationally. If they exist, perhaps some objects currently thought to be black holes are actually wormholes. Because the metric describing how space-time distances and durations are computed would be different outside of certain kinds of black holes and wormholes, observations could potentially distinguish between the two by observing how gas and dust emits light as it orbits close to a candidate compact object. Observers could also use the way that light from background stars is gravitationally lensed if a wormhole passes between it and us along our line of sight, since this is potentially different than the lensing caused by a black hole. Still, the spatial resolution required to observationally distinguish between black holes and wormholes is currently beyond our capabilities, which would likely require future generations technologies such as constellations of coordinated, space based, radio telescopes that use very long baseline interferometry in order to probe spatial scales as small as the innermost stable orbit or the event horizon of the black hole, to see if space-time and matter behave as expected for certain kinds of black holes or wormholes. Needless to say, if wormholes are ever discovered observationally, Nobel prizes are certain to be on the horizon !
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