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The Brain: What Is the Speed of Thought?

Faster than a bird and slower than sound. but that may be besides the point: efficiency and timing seem to be more important anyway..

When Samuel Morse established the first commercial telegraph, in 1844, he dramatically changed our expectations about the pace of life. One of the first telegraph messages came from that year’s Democratic National Convention in Baltimore, where the delegates had picked Senator Silas Wright as their vice presidential nominee. The president of the convention telegraphed Wright in Washington, D.C., to see if he would accept. Wright immediately wired back: No. Incredulous that a message could fly almost instantly down a wire, the delegates adjourned and sent a flesh-and-blood committee by train to confirm Wright’s response—which was, of course, the same. From such beginnings came today’s high-speed, networked society.

Less famously but no less significantly, the telegraph also transformed the way we think about the pace of our inner life. Morse’s invention debuted just as researchers were starting to make sense of the nervous system, and telegraph wires were an inspiring model of how nerves might work . After all, nerves and telegraph wires were both long strands, and they both used electricity to transmit signals. Scientists knew that telegraph signals did not travel instantaneously; in one experiment, it took a set of dots and dashes a quarter of a second to travel 900 miles down a telegraph wire. Perhaps, the early brain investigators considered, it took time for nerves to send signals too. And perhaps we could even quantify that time.

The notion that the speed of thought could be measured, just like the density of a rock, was shocking. Yet that is exactly what scientists did. In 1850 German physiologist Hermann von Helmholtz attached wires to a frog’s leg muscle so that when the muscle contracted it broke a circuit. He found that it took a tenth of a second for a signal to travel down the nerve to the muscle. In another experiment he applied a mild shock to people’s skin and had them gesture as soon as they felt it. It took time for signals to travel down human nerves, too. In fact, Helmholtz discovered it took longer for people to respond to a shock in the toe than to one at the base of the spine because the path to the brain was longer.

Helmholtz’s results clashed with people’s gut instinct that they experienced the world as it happened, with no lag between sensation and awareness. “This is altogether a delusion,” German physiologist Emil Du Bois-Reymond declared in 1868. “It appears that ‘quick as thought’ is, after all, not so very quick.”

With their simple tools, Helmholtz and others could manage only crude measures of the speed of thought. Some of them came up with rates that were twice as fast as others. Researchers have been trying to get more precise results ever since. Today it is clear why they have had such a hard time. Our nerves operate at many different speeds, reflecting the biological challenges of wiring all the parts of the body together. In some ways evolution has fine-tuned our brains to run like a digital superhighway, but in other ways it has left us with a Pony Express.

Thought may not be instantaneous, but it is rapid enough to seem like it is most of the time. The need for speed in the nervous system is not hard to understand. Many animals depend on their nerves to sense danger and to escape from predators; the predators, in turn, depend on their nerves to mount a fast attack. But speed also influences us in surprising ways.

In one common experiment for studying the speed of thought, researchers briefly show test subjects a lopsided, upside-down U and then ask them which leg of the figure is longer. It turns out that the subjects’ reaction times say a lot about their lives in general. People with faster responses tend to score higher on intelligence tests. Some psychologists have argued that a high processing speed in the brain is a vital ingredient for intelligence . Responses slow down when people suffer certain psychological disorders like depression . More puzzling, people with sluggish reaction times are more likely to die of incidents like strokes or heart attacks .

High speed is also crucial to the way we perceive the world . Three or four times a second, our eyes dart in a new direction, allowing us only about a tenth of a second to make sense of what we see in each spot. And we make remarkably good use of that time. Recently, neuroscientists Michelle Greene and Aude Oliva of MIT ran an experiment in which they briefly showed people a series of landscapes and then asked questions about the scenes. For example, was there a forest in the picture? Did it look like a hot place? People did well on these tests even when they glimpsed each of the pictures for less than one tenth of a second .

We are able to understand the world so quickly because of some clever speed boosters built into our eyes. Tim Gollisch of the Max Planck Institute of Neurobiology in Germany recently discovered evidence of one of these. He extracted retinal tissue from amphibians and exposed the living tissue to a series of simple geometric patterns. Then he recorded how the nerve cells fired in response. He noticed that each neuron started firing a little earlier or a little later, depending on which picture he showed. The shifts were distinctive enough that he could predict a shape just by looking at the timing of the neural reaction. Although this test involved amphibians, Gollisch proposes that the results would hold true for human brains as well. They might not wait for all the signals from the retina to arrive before they begin building a representation of the world. They might get a head start with the very first bits of information.

Using a fast code helps speed up thought, but to a large extent the brain—like a telegraph network—really depends on efficient pathways. Impulses from the retinas, for instance, have to travel up the optic nerve to the thalamus, which relays the signals to the visual cortex in the back of the brain. Then they ripple forward to other brain centers, where we use the visual information to make decisions and take actions. One way to hasten that journey is to use fast wiring. In 1854 physicist William Thomson showed that the wider a telegraph wire, the faster its signal and the farther the signal could travel. That same principle applies to nerves. The fattest axons, such as Betz cells in the brain, are 200 times thicker than the thinnest ones.

In principle, our thoughts could race far more efficiently if all the axons in our brains were thick. But the human brain has at least a quarter of a million miles of wiring—more than enough to reach from Earth to the moon—and is already packed tight. Sam Wang , a Princeton University neuroscientist, calculated how big our brain would be if it were built with thick axons. “Making an entire brain out of them would create heads so large that we couldn’t fit through doorways,” he concluded. Such a brain would also consume a tremendous amount of energy.

Given the constraints of biology and physics, our brains appear to have evolved to run very efficiently. For instance, neurons in the brain tend to be joined together into small networks, which are then linked to one another by relatively few long-range connections . This kind of network needs less wiring than other arrangements, and therefore shortens the distance signals need to travel.

Our brains also speed up through practice. Rene Marois , a neuro­scientist at Vanderbilt University, measured this effect by having people perform a basic multitasking test : They had to identify which of two possible faces appeared on a computer screen while responding to one of two possible sounds. In just two weeks of training (encompassing eight to twelve practice sessions), the test-takers were able to do both tasks in rapid succession almost as quickly as doing either one on its own. With practice, Marois speculates, the neurons in the brain’s bottleneck regions , primarily in the prefrontal cortex, require fewer signals and less time to produce the right response.

Sometimes our brains actually need to slow down, however. In the retina, the neurons near the center are much shorter than the ones at the edges, and yet somehow all of the signals manage to reach the next layer of neurons in the retina at the same time . One way the body may do this is by holding back certain nerve signals—for instance, by putting less myelin on the relevant axons. Another possible way to make nerve impulses travel more slowly involves growing longer axons, so that signals have a greater distance to travel.

In fact, reducing the speed of thought in just the right places is crucial to the fundamentals of consciousness. Our moment-to-moment awareness of our inner selves and the outer world depends on the thalamus, a region near the core of the brain, which sends out pacemaker-like signals to the brain’s outer layers. Even though some of the axons reaching out from the thalamus are short and some are long, their signals arrive throughout all parts of the brain at the same time —a good thing, since otherwise we would not be able to think straight.

So when Helmholtz recognized that thought moves at a finite rate, faster than a bird but slower than sound, he missed a fundamental difference between the brain and a telegraph. In our heads, speed is not always the most important thing. Sometimes what really matters is timing.

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What is the speed of thought?

It may feel like thinking happens instantaneously (for some of us), but there's actually some lag time.

Christian Jarrett

Asked by: Geethu Thomas, Surrey

Scientists have approached this difficult question by timing how long it takes us to become consciously aware of sensory information. By some estimates, we can experience sensory stimuli that’s presented for as little as 50 milliseconds (about one-twentieth of a second). It is thought that our brains can, in fact, respond to information that’s much briefer than this, lasting less than a quarter of a millisecond.

In terms of sensing and then responding, a good measure is the sprinter reacting to the starting gun, which can be done in about 150 milliseconds. One limiting factor is how long it takes information to travel down our nerve pathways. In the 19th Century, Hermann von Helmholtz estimated this to be 35 metres per second, but we now know that some well-insulated nerves are faster, at up 120 metres per second.

Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.

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This Trick Flips Space and Time

By Meddling With Spacetime Dimensions, We Could Finally Reach Warp Speed

New research shows that the “superluminal observer” needs three separate time dimensions for a warp-speed math trick that would please even Galileo.

✅ Quick Facts:

• In new research, the lead scientist explains why just one space and one time aren’t enough for this scenario.
• Symmetry is a physics concept that goes all the way back to Galileo’s time.

The secret to faster-than-light physics could be to double down on the number of dimensions. Specifically, the solution may lie in three dimensions of time , with just one representing space. The math is deep and complicated, but the ideas may be within our grasp after all. And there’s one math trick at superspeeds that may just “flip” your lid.

The key idea at play is that of a “superluminal observer,” according to research published in December 2022 in the journal Classical and Quantum Gravity. “Superluminal” means faster than light, from super - meaning “more” or “most,” and - luminal like, well, Lumière from Beauty and the Beast, and the lumens that power your home movie projector. The superluminal observer is a hypothetical thing that is looking at the universe while traveling faster than light. It’s you in your Star Trek warp-speed shuttle.

Superluminal observers are cool because, in a way, they marry together two very different sides of physics: general relativity and quantum mechanics . General relativity is the work embodied by Albert Einstein, which governs how spacetime functions as bodies move around the universe at subluminal, or slower than light, speeds. Quantum mechanics explains how subatomic particles behave, or don’t behave, in very strange ways on the smallest of scales.

The research team—led by theoretical physicist Andrzej Dragan of the University of Warsaw and the National University of Singapore—has theorized that many parts of quantum physics, like indeterminism and superposition , can be explained if you take general relativity and apply its principles to the superluminal observer. In other words, how messy does spacetime get if we take our shuttle up to warp speed? Is everything suddenly in multiple places at once?

Dragan’s new work indicates that it’s at least a possibility. Perhaps more interestingly, the way general relativity becomes quantum phenomena at speeds greater than light doesn’t seem to introduce any causal paradoxes. In earlier work , published in the New Journal of Physics in March 2020, Dragan and his coauthor studied “just” one space dimension and one time dimension, known as 1+1. In the new paper, the researchers upped the ante to include one space dimension and three time dimensions, or 1+3.

When Time and Space Flip Math

Why do we need three time dimensions? To understand, we have to talk about some math. “[D]espite our common perception, time and space are strikingly similar according to relativity, and mathematically the only difference between them is the minus sign somewhere in the equations,” Dragan explains to Popular Mechanics in an email. That’s a small difference in complicated math, but think of the algebra example of the difference of two squares: x² - 16, for example, is the result of (x - 4)(x + 4). With one flipped sign, the middle term in the polynomial falls away.

But when the observer is going faster than the speed of light, the difference in signs also changes. That’s because time and space must flip in the math. “The time of the superluminal observer becomes space of the subluminal one, and their space becomes time,” Dragan says. In other words, the regular, non-light-speed observer’s space and time turn into the time and space, relatively, of the faster-than-light observer. “So their corresponding signs have to interchange.”

In a 1+1 scenario, that means the two dimensions are the same, making it redundant. If 50 = 50, does it matter which 50 is which? (In logic, we call this a tautology.) That means that if we want to truly study space and time as different things, we have to add a second “set” of two dimensions: space and time 1, together, represent space; while time 2 and time 3, together, represent time . It’s not quite the difference of two squares, but we have two balanced sets of dimensions.

The Symmetry in Physics

There’s another interesting aspect to this research, because Dragan’s team wants to show that even at superluminal speeds, physics shows symmetry.

“The idea of symmetry in physics can be traced back to Galileo,” Dragan says. “He noticed that no matter what velocity we move at, as long as that velocity is constant, our physics remains the same. A parrot flying in a moving ship experiences the same dynamical laws as at ‘rest’ on Earth.”

✅ Galileo Galilei was an influential Italian scientist who lived during the 16th and 17th centuries. As an elderly man, he received a life sentence for going public with his belief that Earth orbited the sun!

But our conceptions of physics are limited by the long-running (and reasonable!) belief that nothing can travel faster than light, Dragan explains. That means the superluminal observer, by definition, exists as a kind of exception into which we must work to extend the idea of symmetry. Does it make sense that a superluminal observer would still be subject to symmetry? Is the parrot traveling faster than light still the same as the parrot in the ship or on Earth?

“We argued that this additional limiting assumption isn’t necessary,” Dragan says. He believes symmetry may extend into faster-than-light speeds, and our parrot friend would be just as affected by the same laws of physics while traveling in the warp-speed shuttle.

Toward a Grand Unified Theory

So, this paper isn’t about traveling at warp speed, but instead an analysis of physics to show how we can bring two very different physics branches together. Why is that, itself, so important?

“The idea of more than one time dimension has been considered by others over the years, so that particular premise is not novel,” Harold “Sonny” White, a onetime NASA physicist and the founder of the Limitless Space Institute (LSI), a group that funds and promotes far-out space travel and physics research, tells Popular Mechanics . “But the mathematical framework developed by the authors in this published paper is unique. It would seem the authors’ perceived benefit from the effort is that it establishes a mathematical basis for why we need a field theoretical framework.”

What is a field theoretical framework? It’s the big picture of physics that can bring everything together. “[I]f we envision the standard models of physics as a Venn diagram, there would be two circles side-by-side that touch at a single tangent point,” White explains. “The idea of a grand unified field theory might be envisioned as a larger circle that encircles both the smaller circles.”

By showing their work, these researchers have pointed out a really specific way in which one big basket of physics—rather than two baskets that we aren’t sure how to carry at the same time—would make more sense in practical and mathematical terms.

Okay, sure, you may be thinking: all this superluminal jabberwocky is interesting. But warp speed itself is science fiction, right? (At least for now: White’s LSI funds education that may eventually lead us elsewhere.) The superluminal observer is just a thought exercise ... right?

Dragan isn’t so sure. “The last remaining question is whether superluminal objects are only a mathematical possibility, or they actually exist in reality,” he concludes. “We believe the latter to be that case, and that is the purpose of our further research.”

That means our warp-speed shuttle, once the most far-out thing science fiction writers could even imagine, could embody an elegant theory that brings together two very different kinds of physics. Indeed, objects in the superluminal mirror may be closer than they appear.

Caroline Delbert is a writer, avid reader, and contributing editor at Pop Mech. She's also an enthusiast of just about everything. Her favorite topics include nuclear energy, cosmology, math of everyday things, and the philosophy of it all. 

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Time Slips, the Multiverse, and You

Some believe that time travel is possible. but is it and if so, how.

Posted January 9, 2022 | Reviewed by Jessica Schrader

• The nature of time is one of the biggest mysteries in science. Scientists simply do not understand what time is.
• The universe has a "speed limit" called the speed of light, faster than which nothing in our universe can travel.
• The multiverse theory explains how it could be possible for people to have traveled faster than light speed during "time slips."

The nature of time is one of the biggest mysteries in science. Scientists simply do not understand what time is, at least partially, because it does not behave the same way in all circumstances. For example, did you know that clocks installed on airplanes—or even further away, on satellites—record time at different rates than here on Earth?

We all know that time has a physical component that is measured by clocks. This physical component of time exists because things and people move around in space: the motion of the Earth propels time forward in 24-hour days and 365-day years. We physically experience time because we experience ourselves and things moving around. This is obviously true when you think about different time zones. It isn’t the same time in New York as it is in Sydney because the Earth is moving. In fact, we are all traveling in time at about one second per second. This physical component of time was explained by Einstein who, more than 100 years ago, revolutionized the idea of how time works. He theorized that time and space are inextricably linked together. He also found that the universe has a speed limit of sorts: the speed of light. So while time and space are linked, nothing can travel faster than the speed of light (186,000 miles per second).

But what about otherwise credible reports made by those who claim to have traveled faster than the speed of light? What about reports of actual time travel? The internet is filled with stories about people insisting they experienced jumps in time which are not merely one second per second, but decades or even hundreds of years. These time anomalies, or “time slips,” are paranormal episodes during which someone—or a group of people—somehow experience traveling through time without knowing how or why it occurred.

In one account in Oklahoma in the 1970s, three workers were picking up cattle feeder equipment from a farm and noticed a white house on the property.[1] When they came back the next day, however, the house was not only not there and there was no sign of it ever having been there—yet all three workers saw the same thing the prior day. One possible explanation: the house had existed in a different moment in time, which they collectively experienced as reality.

Whether or not stories like these are to be believed by others, the people who recount them certainly believe them. Given what we know and what we don’t know about how time works, how might these happen?

One explanation is a credible but controversial scientific theory called the multiverse theory. The multiverse theory supposes that an infinite number of worlds exist along different paths in time which arise out of each passing moment, suggesting that different things happen in each universe.[2]

It sounds not only preposterous but also like a lot of work for the universe. Imagine: a new universe traveling along its own, unique timeline created out of every moment of time. This theory suggests there may be an infinite number of universes. It also explains how “time slips” might be real.

Support for the multiverse theory comes from an arcane but scientifically valid Big Bang theory called cosmic inflation.[3] Cosmic inflation refers to a faster-than-light expansion of the universe that may be responsible for spawning an unlimited number of disconnected universes that eternally issue from one another. Cosmic inflation may have happened because, during its earliest instants of formation, the universe was expanding outward from a single point into nothingness. Said another way, the universe’s faster-than-light expansion could be due to the fact that it was expanding into something that was not itself, where the speed of light wouldn’t apply. This may explain just how the universe became so far-flung out of its early chaotic origins.[4]

Whether or not the multiverse, cosmic inflation, and an infinite number of disconnected universes eternally branching off from one another is the way time works remains to be proven by scientists. But the theories are intriguing, and they solve at least one famous problem scientists have with time travel: the grandfather paradox. The grandfather paradox states that if you were to go back in time and kill your grandfather before your father was born, then you wouldn’t exist in the first place to kill him. The multiverse theory solves that paradox in that you could kill a copy of your grandfather in an alternate universe and therefore still have been born in your universe. Of course, it leaves open the question of how you traveled between universes in the first place. Maybe someone experiencing a time slip will one day come back and explain how that works. Maybe you.

Grace Walsh, “Are time slips real? These people certainly think time travel can happen,” Good to Know, January 20, 2020, https://www.goodto.com/family/are-time-slips-real-526367 .

Paul Sutter, “What is multiverse theory?” Live Science, August 23, 2021, https://www.livescience.com/multiverse .

“This is why physicists suspect the Multiverse very likely exists,” Big Think, December 30, 2021, https://bigthink.com/starts-with-a-bang/physicists-multiverse-exists/ .

“Cosmic Inflation,” New Scientist, https://www.newscientist.com/definition/cosmic-inflation/ .

Lisa Broderick holds a B.A. from Stanford and an MBA from Duke. She is a TM Siddha and studied at the Monroe Institute and at the American Institute for Mental Imagery.

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Can anything travel faster than the speed of light?

Does it matter if it's in a vacuum?

In 1676, by studying the motion of Jupiter's moon Io, Danish astronomer Ole Rømer calculated that light travels at a finite speed. Two years later, building on data gathered by Rømer, Dutch mathematician and scientist Christiaan Huygens became the first person to attempt to determine the actual speed of light, according to the American Museum of Natural History in New York City. Huygens came up with a figure of 131,000 miles per second (211,000 kilometers per second), a number that isn't accurate by today's standards — we now know that the speed of light in the "vacuum" of empty space is about 186,282 miles per second (299,792 km per second) — but his assessment showcased that light travels at an incredible speed.

According to Albert Einstein 's theory of special relativity , light travels so fast that, in a vacuum, nothing in the universe is capable of moving faster. 

"We cannot move through the vacuum of space faster than the speed of light," confirmed Jason Cassibry, an associate professor of aerospace engineering at the Propulsion Research Center, University of Alabama in Huntsville.

Question answered, right? Maybe not. When light is not in a vacuum, does the rule still apply?

Related: How many atoms are in the observable universe?

"Technically, the statement 'nothing can travel faster than the speed of light' isn't quite correct by itself," at least in a non-vacuum setting, Claudia de Rham, a theoretical physicist at Imperial College London, told Live Science in an email. But there are certain caveats to consider, she said. Light exhibits both particle-like and wave-like characteristics, and can therefore be regarded as both a particle (a photon ) and a wave. This is known as wave-particle duality.

If we look at light as a wave, then there are "multiple reasons" why certain waves can travel faster than white (or colorless) light in a medium, de Rham said. One such reason, she said, is that "as light travels through a medium — for instance, glass or water droplets — the different frequencies or colors of light travel at different speeds." The most obvious visual example of this occurs in rainbows, which typically have the long, faster red wavelengths at the top and the short, slower violet wavelengths at the bottom, according to a post by the University of Wisconsin-Madison . 

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When light travels through a vacuum, however, the same is not true. "All light is a type of electromagnetic wave, and they all have the same speed in a vacuum (3 x 10^8 meters per second). This means both radio waves and gamma rays have the same speed," Rhett Allain, a physics professor at Southeastern Louisiana University, told Live Science in an email.

So, according to de Rham, the only thing capable of traveling faster than the speed of light is, somewhat paradoxically, light itself, though only when not in the vacuum of space. Of note, regardless of the medium, light will never exceed its maximum speed of 186,282 miles per second.

Universal look

According to Cassibry, however, there is something else to consider when discussing things moving faster than the speed of light.

"There are parts of the universe that are expanding away from us faster than the speed of light, because space-time is expanding," he said. For example, the Hubble Space Telescope recently spotted 12.9 billion year-old light from a distant star known as Earendel. But, because the universe is expanding at every point, Earendel is moving away from Earth and has been since its formation, so the galaxy is now 28 billion light years away from Earth.

In this case, space-time is expanding, but the material in space-time is still traveling within the bounds of light speed.

Related: Why is space a vacuum?

So, it's clear that nothing travels faster than light that we know of, but is there any situation where it might be possible? Einstein's theory of special relativity, and his subsequent theory of general relativity, is "built under the principle that the notions of space and time are relative," de Rham said. But what does this mean? "If someone [were] able to travel faster than light and carry information with them, their notion of time would be twisted as compared to ours," de Rham said. "There could be situations where the future could affect our past, and then the whole structure of reality would stop making sense."

This would indicate that it would probably not be desirable to make a human travel faster than the speed of light. But could it ever be possible? Will there ever be a time when we are capable of creating craft that could propel materials — and ultimately humans — through space at a pace that outstrips light speed? "Theorists have proposed various types of warp bubbles that could enable faster-than-light travel," Cassibry said.

But is de Rham convinced?

"We can imagine being able to communicate at the speed of light with systems outside our solar system ," de Rham said. "But sending actual physical humans at the speed of light is simply impossible, because we cannot accelerate ourselves to such speed.

"Even in a very idealistic situation where we imagine we could keep accelerating ourselves at a constant rate — ignoring how we could even reach a technology that could keep accelerating us continuously — we would never actually reach the speed of light," she added. "We could get close, but never quite reach it."

Related: How long is a galactic year?

This is a point confirmed by Cassibry. "Neglecting relativity, if you were to accelerate with a rate of 1G [Earth gravity], it would take you a year to reach the speed of light. However, you would never really reach that velocity because as you start to approach lightspeed, your mass energy increases, approaching infinite. "One of the few known possible 'cheat codes' for this limitation is to expand and contract spacetime, thereby pulling your destination closer to you. There seems to be no fundamental limit on the rate at which spacetime can expand or contract, meaning we might be able to get around this velocity limit someday."

— What would happen if the speed of light were much lower?

— What if the speed of sound were as fast as the speed of light?

— How does the rubber pencil illusion work?

Allain is similarly confident that going faster than light is far from likely, but, like Cassibry, noted that if humans want to explore distant planets, it may not actually be necessary to reach such speeds. "The only way we could understand going faster than light would be to use some type of wormhole in space," Allain said. "This wouldn't actually make us go faster than light, but instead give us a shortcut to some other location in space."

Cassibry, however, is unsure if wormholes will ever be a realistic option.

"Wormholes are theorized to be possible based on a special solution to Einstein's field equations," he said. "Basically, wormholes, if possible, would give you a shortcut from one destination to another. I have no idea if it's possible to construct one, or how we would even go about doing it." Originally published on Live Science.

Joe Phelan is a journalist based in London. His work has appeared in VICE, National Geographic, World Soccer and The Blizzard, and has been a guest on Times Radio. He is drawn to the weird, wonderful and under examined, as well as anything related to life in the Arctic Circle. He holds a bachelor's degree in journalism from the University of Chester. 

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Traveling Faster Than Light Would Mean Experiencing Multiple Timelines Simultaneously

Mind blown., fruit of the luminal.

An international team of physicists has cooked up with a new theory that could allow for objects to travel faster than the speed of light — and while they say it wouldn't technically violate the laws of physics, it would lead to phenomena so mind-bending that it'd make the end of "Interstellar" look normal.

To wit, according to ScienceAlert 's analysis of the team's new paper in the journal Classical and Quantum Gravity , travelers moving faster than the speed of light would "experience" multiple timelines at once.

How, you might ask? Through a "1+3 space-time" framework, which flips the idea of three spatial dimensions and one time dimension in favor of three time dimensions and a single spatial dimension.

"The other three dimensions are time dimensions," said coauthor Andrzej Dragan from the University of Warsaw in Poland   in statement about the work. "From the point of view of such an observer, the particle 'ages' independently in each of the three times."

1+3 Space-Time

Does that make any sense from our puny human perspective? We're honestly not sure.

But it is a mind-bending exploration of an exotic what-if, not to mention yet another example of researchers playing around with the decidedly "Star Trek" concept of faster-than-light travel. An added bonus? In theory, the scientists say, the framework might even help reconcile Einstein's theory of relativity with quantum mechanics, two sets of rules in physics that have yet to play nicely after many decades.

"This new definition preserves Einstein's postulate of constancy of the speed of light in vacuum even for superluminal observers," Dragan said in the statement. "Therefore, our extended special relativity does not seem like a particularly extravagant idea."

Look, it sounds very cool. But then again, so did "Tenet" — and we all saw how that one turned out.

More on quantum physics: Physicist Says the Laws of Physics Don't Actually Exist 

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Faster than Light

We all know/believe that as we approach the speed of light, time will become infinite and we may not be able to reach the speed of light. In other words nothing can travel faster than the speed of light . But in our last blog, Time Machine will remain fiction forever, we have expected to understand time better at infinity or near speed of light with the Teleportation and it’s timeline example. Let us try to understand with some examples the results of traveling at speeds near speed of light, at speed of light and beyond the speed of light.

We have seen in the previous blog that one second of earth’s time can be equal to 1 minute or 1 hour or 1 year of another planet or vice versa. There is actually a formula to calculate the exact slowness of time (also called time dilation) known as Lotentz Transformation factor credited to dutch scientist Hendrik Lorentz.. We now know that time becomes slower and slower as we reach the speed of light . This formula uses the speed of the time traveler (‘v’ in below formula) to determine how slow his time will run.

Lorentz transformation factor

Here c is the speed of light and v is  velocity of an object or Time Traveler. We usually consider the value of speed of light, c ,  equal to one, and change v  proportionately, so that calculations becomes easier. For example if speed of light is 1, the ‘v’ would be 0.5 for half the speed of light, 0.9c would be 0.9 times speed of light. We see that when v = c or in other words   both v and c are equal to one, the Lorentz factor becomes infinite. [ 1/ sqrt(1- (1/1)) ; 1/0 = infinity ]

Though the time becomes infinite, we can actually calculate time dilation upto or very near the speed of light. We have Lorenz transformation factor which we can use to calculate the factor of time dilation (how slow the time will become). I have calculated Lorentz transformation factor below for some values that we can consider as equal or near equal to the speed of light.

Calculating Time Dilation using Lorentz factor

In the above table, we can see that when the speed of time traveler is 0.9 times the speed of light his clock will run 2.3 times slow than that on earth, i.e earth’s 1sec = time traveler’s 2.3sec. Similarly we can keep on adding 9 at the end of that number to increase precision and actually calculate how slow the time traveler’s clock will run with respect to time on earth.

We had all expected that the time will become slower and slower as we reach the speed of light and we may not actually reach the speed of light. But as we can see the amount of time dilation increases by only 3.16 times  approx (time becomes slow by 3.16 times)  as we keep on adding 9 to increase the precision. That means we can actually calculate the time dilation at the speed of light and time may not actually be infinite .

There is one more reason why time dilation cannot continue to increase forever . Whenever we need to reach a number we reduce one from it and divide it. We will get a precision upto one less digit than the digits in that number. E.g. speed of light is 2,99,792 km/s (6 digits). To get a number very near to that number we reduce 1 from that number and divide it by the number. We get only five 9s after the decimal and six 9s can be considered being reached that number and any more 9s are unnecessary.

299791/299792=0.999997

When we again look at the chart we can see that at six 9s in the precision we only get 11min47sec of time dilation i.e 1sec of earth time will be equal to 12 minutes approx. of the time traveler. That means if nothing can travel faster than the speed of light except light itself, then there cannot be time dilation more than 12 minutes anywhere in the Universe or it is possible to travel faster than light.  That also means that the e.g. of Time Traveler in last blog where earth’s 1sec = Time Traveler’s 1 hr is not really possible! (It would be 1 hour, if we considered speed of light in meter/second or even more with different units). 

But what if the Time Traveler is traveling beyond the speed of light itself? As we have seen above, Lorentz transformation factor is based on the speed of light and anything beyond speed of light or at speed of light cannot be handled by this formula. So we can’t just keep on increasing precision! Instead we can try and understand our universe directly with the time dilation example used in previous blog irrespective of speed of Time Traveler.

I would once again like to thank Sir  Larry Randles Lagerstrom , for the online course “Understanding Einstein and Special Theory of Relativity” on coursera.org, without which I could not have understood Lorentz Transformation and other aspects related to Time and Special Theory of Relativity. I have not yet completely understood the whole course, I keep watching the video lectures to better understand it.

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Faster-Than-Light Particle Fits With Special Theory of Relativity, Physicists Say

The hypothetical faster-than-light particle known as the tachyon may marry with the special theory of relativity, according to a team of physicists, making its existence more plausible.

What the hell is a tachyon?

Tachyons are a type of hypothetical particle, meaning their existence remains a matter of speculation. The tachyon is also proposed to be superliminal, meaning it always travels faster than light. A hypothetical, superliminal particle… we pray that Lin-Manuel Miranda never makes a musical about exotic physics.

There is no evidence that tachyons exist, as is the case with plenty of particles proposed to make up our universe. Some physicists believe tachyons exist because they would offer solutions to certain problems in particle physics and field theories. But the recent team’s research, published this week in Physical Review D , claims that previous doubts of tachyons’ plausibility were unfounded.

Special relativity and the limit of lightspeed

In 1905, Einstein produced his theory of special relativity, which describes the relationship between space and time ( E = mc 2 — sound familiar?). A fundamental part of the theory holds that the speed of light can be approached, but not reached, by material objects.

Unlike other hypothetical particles such as axions and dark photons —both types of dark matter candidates which are not proven to exist—there are several reasons why tachyons may not exist. For one, according to a University of Warsaw release , the ground state of the tachyon field was thought to be unstable. Additionally, depending on the observer’s position, a different number of particles would be observed, and lastly, the particles’ energy could assume negative values. In the recent work, the team posit that the issues with the particle could be resolved by knowing both the initial and final states of the system. In that case, the “tachyon theory became mathematically consistent,” the release stated.

The new research also conjures up “a new kind of quantum entanglement” that mixes past and future, the university release stated, which does not exist in conventional particle theory. “The idea that the future can influence the present instead of the present determining the future is not new in physics,” said Andrzej Dragan, a physicist at the University of Warsaw and co-author of the paper, in the release. “However, until now, this type of view has at best been an unorthodox interpretation of certain quantum phenomena, and this time we were forced to this conclusion by the theory itself.”

But nothing can move faster than light…right?

The short answer is no, nothing can exceed the speed of light: 983,571,056 feet per second, or 299,792,458 meters per second. The longer answer is that it’s complicated; for example, quasiparticles created by clouds of electrons act as if they travel faster than light , though they do not.

And while we’re musing on hypotheticals: If some other intelligent beings in the universe have figured out how to travel faster than light, evidence of their triumph may be detectable in the gravitational ripples produced by their technology, as proposed by a recent team of physicists .

Like the tachyon itself, the work is very speculative. But such is the domain of these hypothetical particles. Researching stuff that moves faster than light was always going to require some imagination.

lightspeed Particle physics special relativity tachyons

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