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George Orwell



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Is Time Travel Possible?

Is Time Travel Possible?

By Sarah Scoles — Scientific American

The laws of physics allow time travel.

So why haven’t people become chronological hoppers?

In the movies, time travelers typically step inside a machine and—poof—disappear. They then reappear instantaneously among cowboys, knights or dinosaurs. What these films show is basically time teleportation.

Scientists don’t think this conception is likely in the real world, but they also don’t relegate time travel to the crackpot realm. In fact, the laws of physics might allow chronological hopping, but the devil is in the details.



Time Travel
10 mind-blowing theories

By Adrian Sharp — List Verse

Imagine a world where you could travel back in time, witness historical events, and even change the course of history. A world where the impossible becomes possible, and the laws of physics bend to your will. It’s an idea that has captured the imaginations of scientists and authors for centuries. Whether you believe that it’s possible or not, these ten mind-blowing theories will give you something to think about.



Spacetime: Real and Physical?
or just a calculation tool?

By Ethan Siegel — BigThink

Einstein’s relativity overthrew the notion of absolute space and time, replacing them with a spacetime fabric. But is spacetime truly real?

There’s more to the Universe than the objects within it. There’s also the fabric of spacetime, which has its own set of rules that it plays by: General Relativity. The fabric of spacetime is curved by the presence of matter and energy, and curved spacetime itself tells matter and energy how to move through it.

But what, exactly, is the physical nature of spacetime? Is it a real, physical thing, like atoms are, or is it merely a calculational tool that we use to give the right answers for the motion and behavior of the matter within the Universe?



On the Origin of Time
Thomas Hertog on Stephen Hawking’s Final Theory

By Michael Shermer — Skeptic

Perhaps the biggest question Stephen Hawking tried to answer in his extraordinary life was how the universe could have created conditions so perfectly hospitable to life. In order to solve this mystery, Hawking studied the Big Bang origin of the universe, but his early work ran into a crisis when the math predicted many big bangs producing a multiverse — countless different universes, most of which would be far too bizarre to harbor life. Holed up in the theoretical physics department at Cambridge, Stephen Hawking and his friend and collaborator Thomas Hertog worked on this problem for twenty years, developing a new theory of the cosmos that could account for the emergence of life.

Shermer and Hertog discuss: what it was like working with Stephen Hawking • Darwinian model of cosmology • time • What banged the Big Bang? • cosmic inflation and multiple universes • how to reconcile Einstein’s relativity theory of gravity and quantum theory • Hawking’s no-boundary theory • why the universe appears designed • Feynman’s sum over histories approach to quantum physics • Is there purpose in the cosmos? • Why is there something rather than nothing?

Watch the YouTube video!



Why Does Time Slow Down
as you approach the speed of light?

By Doing Maths

Most people have heard that time slows down as you approach the speed of light. But why? This video looks at why this happens and explores the maths behind calculating how much time will slow down as you travel.

Watch the YouTube video!



Time Dilation
Why an accelerated frame of reference slows down time

By But Why?

Everything is relative. Or so that’s what Einstein postulated over 100 years ago in his theory of special relativity. Just like how another objects observed velocity depends on the velocity of the observer, so too does the observed velocity of light.

As we change frames of reference, the observed velocity of light needs to remain the same and this transition causes what can be considered a dilation of time.

But why does Time dilation happen at all?

Watch the YouTube video!


The Physics and Philosophy of Time

By Carlo Rovelli — The Royal Institution

From Boltzmann to quantum theory, from Einstein to loop quantum gravity, our understanding of time has been undergoing radical transformations. Carlo Rovelli brings together physics, philosophy and art to unravel the mystery of time.

Watch the YouTube video!



What’s Time?

By Lee Smolin — Science for Free

Lee Smolin was one of the initiators of two research programs: loop quantum gravity and deformed special relativity. He has the last few years been pioneering a new direction based on the hypothesis that time is a fundamental and irreducible aspect of nature, and that the fundamental laws of nature evolve irreversibly.

Watch the YouTube video!



Scientists Create Slits In Time
a mind-bending physics experiment


Researchers replicated the classic double slit experiment using lasers, but their slits are in time not space.

The findings pave the way for advances in analog computers that manipulate data imprinted on beams of light instead of digital bits – it might even make such computers “learn” from the data. They also deepen our understanding of the fundamental nature of light and its interactions with materials. 



Is Time an Illusion?
try figuring out the time on the moon

By Miriam Frankel — The Conversation

Without a sense of time, leading us from cradle to grave, our lives would make little sense. But on the most fundamental level, physicists aren’t sure whether the sort of time we experience exists at all.

This is the topic of the first episode of our new podcast series, Great Mysteries of Physics. Hosted by me, Miriam Frankel, science editor at The Conversation, and supported by FQxI, the Foundational Questions Institute, we talk to three researchers about the nature of time.



An Entirely New Way of Measuring Time

By Mike Mcray — Science Alert

Determining the passage of time in our world of ticking clocks and oscillating pendulums is a simple case of counting the seconds between ‘then’ and ‘now’.

Down at the quantum scale of buzzing electrons, however, ‘then’ can’t always be anticipated. Worse still, ‘now’ often blurs into a haze of vagueness. A stopwatch simply isn’t going to work for some scenarios.

A potential solution could be found in the very shape of the quantum fog itself, according to a 2022 study by researchers from Uppsala University in Sweden.



Quantum Mechanics
how the Future Might Influence the Past

By Huw Price and Ken Wharton — The Conversation

A growing group of experts think that we should abandon the assumption that present actions can’t affect past events. Called “retrocausality”, this option claims to rescue both locality and realism.



The Lunar Time Zone
try figuring out the time on the moon

By Geof Brumfiel and Carmen Molina Acosta — NPR

With multiple missions to the moon in the planning phase, it’s time to set a Lunar time standard.

“We need to define a time on the moon,” says Javier Ventura-Traveset of the European Space Agency (ESA). Without it, Ventura-Traveset warns, docking spacecraft could tumble into each other, astronauts might get lost on the lunar surface, and of course, nobody will know when they can take their lunch break.



Time Is Not What It Used to Be
Children and Adults Experience Time Differently

By Eötvös Loránd University

Time can play tricks on us. Many of us experienced the illusion that those long summers during childhood felt so much longer than the same 3 months feel like now as an adult. While we can argue why one summer may appear longer than the other and how the perception of time can compress and dilate durations depending on various factors, we can easily set up an experiment to gain more insights.

The researchers just did that. 



Prague Astro Clock 1410


Our Time Perception Flips at Midlife

By Ann Douglas — Psychology Today

We start thinking about how much time we have left—and how to use that time.

  • Midlife is a time of self-reflection—a time for considering one’s past, present, and future.
  • Time perception flips. Instead of someone focusing on how long they’ve lived, they start thinking about how many years they have left.
  • This encourages them to zero in on the relationships and activities that matter most.


Mind-Bending Physics of Time

By Sean Carroll

Theoretical physicist Sean Carroll discusses the concept of time and the mysteries surrounding its properties. He notes that while we use the word “time” frequently in everyday language, the real puzzles arise when we consider the properties of time, such as the past, present, and future, and the fact that we can affect the future but not the past.



Three Time Dimensions
one space dimension

Clock Time Relativity Concept Art

By University of Warsaw, Faculty of Physics

A Revolutionary New Physics Hypothesis

How would our world be perceived by observers moving faster than light in a vacuum? According to theorists from Warsaw and Oxford universities, such a view would differ from what we encounter daily, with the presence of not only spontaneous phenomena but also particles traveling multiple paths simultaneously.

Futhermore, the very concept of time would be completely transformed!



Twisting Up Atoms Through Space and Time

Twisting Up Atoms Through Space and Time

By Dina Genkina — Joint Quantum Institute

One of the most exciting applications of quantum computers will be to direct their gaze inwards, at the very quantum rules that make them tick. Quantum computers can be used to simulate quantum physics itself, and perhaps even explore realms that don’t exist anywhere in nature.




This $42 Million-Dollar Timekeeping Device
runs for 10  millennia

By Allison Eck — PBS NOVA

Could this “10,000-year clock,” which looks like it’s straight out of a Star Trek episode or the set of Interstellar, inspire people to start thinking long-term?

Mindfulness gurus tell us to focus on the present, but what if we chose to be much more forward-thinking? How would society function if we saw a year as not 12 months, but a sliver of a century?



Did You Change Your Clocks Again?
but why?

By Leda Gore — AI

A bill passed to end daylight saving time. Here’s why you still have to change your clocks.

The ritual of “falling back” – setting clocks back one hour to mark the end of daylight saving time – officially takes place at 2 a.m. Saturday. The hour clock change doesn’t alter time itself, of course, but shifts more daylight into the morning instead of the evening.



Why Time Passes Faster As You Age
Mind time cannot be measured on a watch.

By Ephrat Livni — QUARTZ

Mind time and clock time are two totally different things. They flow at varying rates.

The chronological passage of the hours, days, and years on clocks and calendars is a steady, measurable phenomenon. Yet our perception of time shifts constantly, depending on the activities we’re engaged in, our age, and even how much rest we get. 




What Is Happening “Now” Is Relative
In special relativity, the statement that two events happened at the same time is meaningless.

By Sabine Hossenfelder — BIG THINK

  • We always see things as they looked a little bit earlier, but we don’t normally notice this in everyday life. It gets even weirder, though. 
  •  In special relativity, the statement that two events happened at the same time is meaningless. 
  • Every event is “now” for someone.


“Absolutely, the NOW doesn’t exist, but subjectively we perceive each moment as special.”
— Sabine Hossenfelder, Existential Physics


Does the Past Still Exist

By Sabine Hossenfelder




TIME: A Discussion
Carlo Rovelli and Oliver Burkeman talk about time

By 5×15

Watch the FREE video!




The Nature of Time

By Carlo Rovelli



What Is Time? What Is Space?

By Carlo Rovelli

“A novel image of the world is taking shape in fundamental physics: a world without time and without space. Time and space as we know them will disappear from the scientific picture of the world, in the same way in which the centre of the universe did”.

In this agile text, derived from a long interview, Carlo Rovelli, theoretical physicist and pioneer of modern quantum gravity, describes his personal and intellectual journey, starting from the rebellion of his young years and the discovery of the “enchanting adventure” of theoretical research, till the vertiginous hypotheses of today’s physics. In a simple language, Rovelli introduces us to a “space” made of grains, a “time” which is the result of our ignorance, to hot black holes and how to think about the beginning of the universe.

But he also discusses the value, the risks, and the fascination of this quest. Science, for Rovelli, is a continuous exploration of new ways of thinking the world, the desire of looking “beyond the hill” and seeing the world always with new eyes, the choice of never giving up dreams.




The Illusion of Time?

By Carlo Rovelli


Four Thousand Weeks
time management for mortals

By Oliver Burkeman

The average human lifespan is absurdly, insultingly brief. Assuming you live to be eighty, you have just over four thousand weeks.

Nobody needs telling there isn’t enough time. We’re obsessed with our lengthening to-do lists, our overfilled inboxes, work-life balance, and the ceaseless battle against distraction; and we’re deluged with advice on becoming more productive and efficient, and “life hacks” to optimize our days. But such techniques often end up making things worse. The sense of anxious hurry grows more intense, and still the most meaningful parts of life seem to lie just beyond the horizon. Still, we rarely make the connection between our daily struggles with time and the ultimate time management problem: the challenge of how best to use our four thousand weeks.



What Is Time, And How Do We Know It Exists?
We experience its flow constantly but it’s not obvious what time actually is.

By Alfredo Carpineti — IFLSCIENCE

Time. We can’t get enough of it. We are desperate to make it flow faster or slower, and yet we are reminded again and again to live in the now. When it comes to big philosophical questions, the concept of time and related ideas like past, present, and future are among the big hitters. Is the future already written? What do we mean by the present? Does the past exist?  



What Is Planck Time?

By Andrew May — Space.com

The almost impossibly brief Planck time has been known since the 19th century. Originally dismissed as a mere curiosity, it may hold the key to understanding the universe.

Planck time is an incredibly small interval of time that emerges naturally from a few basic quantities in theoretical physics. When it was discovered by Max Planck at the end of the 19th century, it seemed to be no more than a scientific curiosity. But today it plays a tantalizing role in our understanding of the Big Bang and the search for a theory of quantum gravity



Superposition of Photon
Goes Forward and Backward in Time

By Dr. Alfredo Carpineti — IFLSCIENCE

Experiments demonstrate that it is possible to put a photon in a superposition of processes going in opposite time directions.

Two different groups have tested a seemingly counter-intuitive property of the quantum world: That it’s possible to put a photon, a particle of light, in a superposition of states going forward and backward in time. This is not time travel and won’t lead to communicating with the past – but it is an intriguing demonstration of how time can be thought to work at a quantum level.



Why Does Time Move Forward?
But not Backward

By Sabine Hossenfelder — BigThink

Sabine Hossenfelder explains it all!



An Entirely New Way of Measuring Time

By Mike McCray — Physics

Marking the passage of time in a world of ticking clocks and swinging pendulums is a simple case of counting the seconds between ‘then’ and ‘now’.

Down at the quantum scale of buzzing electrons, however, ‘then’ can’t always be anticipated. Worse still, ‘now’ often blurs into a haze of uncertainty. A stopwatch simply isn’t going to cut it for some scenarios.



The Thorny Problem of Keeping the Internet’s Time
An obscure software system synchronizes the network’s clocks. Who will keep it running?

By Nate Hopper — The New Yorker

In 1977, David Mills, an eccentric engineer and computer scientist, took a job at comsat, a satellite corporation headquartered in Washington, D.C. Mills was an inveterate tinkerer: he’d once built a hearing aid for a girlfriend’s uncle, and had consulted for Ford on how paper-tape computers might be put into cars. Now, at comsat, Mills became involved in the arpanet, the computer network that would become the precursor to the Internet. A handful of researchers were already using the network to connect their distant computers and trade information. But the fidelity of that exchanged data was threatened by a distinct deficiency: the machines did not share a single, reliable synchronized time.



How Do We Know That Time Exists?

By CORDIS — Phys.Org

The alarm goes off in the morning. You catch your morning train to the office. You take a lunch break. You catch your evening train back. You go for an hour’s run. Eat dinner. Go to bed. Repeat. Birthdays are celebrated, deaths commemorated. New countries are born, empires rise and fall. The whole of human existence is bound to the passing of time.

But we can’t see it and we can’t touch it. So, how do we know that it’s really there?



Why Does Time Go Forwards, Not Backwards?

By Martha Henriques — BBC

The arrow of time began its journey at the Big Bang, and when the Universe eventually dies there will be no more future and no past. In the meantime, what is it that drives time ever onward?


Time Reborn
From the Crisis in Physics to the Future of the Universe

By Lee Smolin

A radical new view of the nature of time and the cosmos.

What is time?
This deceptively simple question is the single most important problem facing science as we probe deeper into the fundamentals of the universe. All of the mysteries physicists and cosmologists face—from the Big Bang to the future of the universe, from the puzzles of quantum physics to the unification of forces and particles—come down to the nature of time.
The fact that time is real may seem obvious. You experience it passing every day when you watch clocks tick, bread toast, and children grow. But most physicists, from Newton to Einstein to today’s quantum theorists, have seen things differently. The scientific case for time being an illusion is formidable. That is why the consequences of adopting the view that time is real are revolutionary.




The Nature of Time

By Lee Smolin



A New Theory of Time

By Lee Smolin



A World in Time

By Lee Smolin




“The past is another country: they do things differently there.”
— L.P. Hartly, The Go-Between


Until the End of Time
Mind, Matter, and Our Search for Meaning in an Evolving Universe

By Brian Greene

Until the End of Time is Brian Greene’s breathtaking new exploration of the cosmos and our quest to find meaning in the face of this vast expanse. Greene takes us on a journey from the big bang to the end of time, exploring how lasting structures formed, how life and mind emerged, and how we grapple with our existence through narrative, myth, religion, creative expression, science, the quest for truth, and a deep longing for the eternal. From particles to planets, consciousness to creativity, matter to meaning—Brian Greene allows us all to grasp and appreciate our fleeting but utterly exquisite moment in the cosmos.



The Richness of Time

By Brian Greene

Join a physicist, a neuroscientist, and a linguist as they explore the deep enigmas of time. Time feels like it flows, but does it? Time seems to have a built-in direction, from past to future, but is that real or merely a quality imposed by the human brain? Time on earth elapses at a uniform rate, so why does the human experience of time seem so varied? How do various neurological afflictions change the perception of time? And underneath it all, how does human language impact our ability to think about time and fully experience its rich and mysterious contours?



Carlo Rovelli Interview
“reality is not things but connections.”

By New Scientist

Inspired by the art of Cornelia Parker, physicist Carlo Rovelli explains the idea of relational quantum mechanics – and how it could resolve some key problems concerning the nature of reality.



Time Travel: A History

By James Gleick

James Gleick delivers a mind-bending exploration of time travel—from its origins in literature and science to its influence on our understanding of time itself. Gleick vividly explores physics, technology, philosophy, and art as each relates to time travel and tells the story of the concept’s cultural evolutions—from H.G. Wells to Doctor Who, from Proust to Woody Allen. He takes a close look at the porous boundary between science fiction and modern physics, and, finally, delves into what it all means in our own moment in time—the world of the instantaneous, with its all-consuming present and vanishing future.



Portal Opens to Extra Time Dimension
just what we need, eh?

By Zeeya Merali  — Scientific American

Opening a portal to an extra time dimension—even just a theoretical one—sounds thrilling, but it was not the physicists’ original plan. 




Time Isn’t Simply Just Another Dimension

By Ethan Siegal — BIG Think

We live in a four-dimensional Universe, where matter and energy curve the fabric of spacetime. But time sure is different from space!

  • According to Einstein’s General Relativity, matter and energy curve the fabric of spacetime, and that curved spacetime determines the motion of matter and energy. 
  • But while spacetime itself is four dimensional, it can be decomposed into three spatial dimensions and one time dimension. 
  • Even though we understand the mathematics governing them magnificently, time has some fundamental differences from every other dimension; here’s what everyone should know.


Where Do Space, Time and Gravity Come From?

By Quanta Magazine

Einstein’s description of curved space-time doesn’t easily mesh with a universe made up of quantum wavefunctions. Theoretical physicist Sean Carroll discusses the quest for quantum gravity with host Steven Strogatz.



The Biggest Ideas in the Universe

By Sean Carroll — The Royal Institution

Join Sean M Carroll as he explores deep questions about the cosmos, laying out the framework of classical physics from Euclid and Galileo to Newton and Einstein.



Felt Time
The Psychology of How We Perceive Time

Felt Time: The Psychology of How We Perceive Time by [Marc Wittmann, Erik Butler]

By Marc Wittmann 

An expert explores the riddle of subjective time, from why time speeds up as we grow older to the connection between time and consciousness.

We have widely varying perceptions of time. Children have trouble waiting for anything. (“Are we there yet?”) Boredom is often connected to our sense of time passing (or not passing). As people grow older, time seems to speed up, the years flitting by without a pause. How does our sense of time come about? 



Time Warped
Unlocking the Mysteries of Time Perception

Time Warped: Unlocking the Mysteries of Time Perception by [Claudia Hammond]

By Claudia Hammond

Why does life seem to speed up as we get older? Why does the clock in your head move at a different speed from the one on the wall? Why is it almost impossible to go a whole day without checking your watch? Is it possible to retrain our brains and improve our relationship with it?



Your Brain Is a Time Machine
The Neuroscience and Physics of Time

Your Brain Is a Time Machine: The Neuroscience and Physics of Time by [Dean Buonomano]

By Dean Buonomano 

Neuroscientist Dean Buonomano embarks on an “immensely engaging” exploration of how time works inside the brain. The human brain, he argues, is a complex system that not only tells time, but creates it; it constructs our sense of chronological movement and enables “mental time travel”—simulations of future and past events. These functions are essential not only to our daily lives but to the evolution of the human race: without the ability to anticipate the future, mankind would never have crafted tools or invented agriculture. 



Timeless Reality
Symmetry, Simplicity, and Multiple Universes

By Victor J. Stenger

Quantum physics has many extraordinary implications. One of the most extraordinary is that events at the atomic and subatomic level seem to depend on the future as well as the past. Is time really reversible? Physicist Victor J. Stenger says yes. Contrary to our most basic assumptions about the inevitable flow of time from past to future, the underlying reality of all phenomena may have no beginning and no end, and not be governed by an “arrow of time.” 



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