The earliest mention of time travel

The origins of our fascination with time travel

Humans have been captivated by the prospect of leaping forward and backward in time for thousands of years. Georgia Institute of Technology Science Fiction Studies Professor Lisa Yaszek recounts how the concept has been utilized by storytellers from 400 BCE to modern-day to explore our relationship with the supernatural, technology, and the past. In a way, this historical recounting is a journey through time.

Five potential ways to achieve time travel

While the author discounts the possibility of traveling to the past, it lays out five hypothetical modes of catapulting into the future: speed, gravity, suspended animation, wormholes, and light. Each has some scientific basis, but none are realistic for humans. Read the article to learn where they offer promise and where they fall short.

A scientific analysis of famous time travel stories

This 8-minute video explores how time travel influences the narrative arc of several movies, books and video games, from Harry Potter to A Christmas Carol. (Warning: it contains spoilers!) J.K. Rowling and Charles Dickens set myriad parameters as they’re worldbuilding to avoid paradoxes and create quasi-logical timelines. By drawing diagrams as he’s speaking, the video breaks down how time works in some of popular culture’s most beloved fictional universes.

Is time travel really possible?

The laws of physics, as currently understood, don’t categorically reject the possibility of time travel. But, scientists are skeptical, especially when it comes to traveling to the past. Hopping between past, present and future would require the world to have some wacky yet-to-be-discovered physical properties like negative mass, negative energy, and infinite density. Time travel also introduces philosophical questions about free will, causality, and chronology.

Tips for writing time travel stories

Are you thinking of writing a story that involves time travel? You might want to read this guide first. It offers questions to consider, mistakes to avoid and strategies to employ to ensure you avoid paradoxes, plot holes and implausibilities.

What Stephen Hawking said about time travel

When renowned theoretical physicist Stephen Hawking did not rule out the possibility of time travel in his posthumous book Brief Answers to the Big Questions, many hopefuls got excited. But, unfortunately for them, Hawking believed that yet-to-be discovered laws of physics will prove time travel impossible. This piece outlines some practicalities about the speed of light and wormholes that lend way to Hawking’s prediction.

According to special relativity, time travel cannot change history

Although time travel is allowed—because all moments of the past, present, and future exist simultaneously and are locked in place—you will be unable to alter events beyond those that you changed because you were there before your travel to the past, including doing something to change your existence.

Humans have speculated about alien life since ancient times

Around 50 B.C.E., Roman poet and philosopher Lucretius shared the idea that alien life was possible, which was put forth by Greek philosopher Epicurus. The writing is believed to be the first straightforward assertion in Western literature that aliens must exist.

Philosophers have debated the nature of time since at least the 6th century B.C.E.

Greek philosopher Parmenides of Elea was skeptical of time and reasoned that if it were real, then the present would emerge from nothing because the future did not yet exist. Just as the color red is our perception of a specific wavelength of light, others have suggested time is a psychological projection based on how we interpret the world.

Ancient ghost stories appeared in texts like 'The Odyssey'

Sharing ghost tales has been around for centuries. Ancient Mesopotamia, Rome, and Greece each had their own chilling stories about encountering spirits. Find mentions of specters in some of history’s most famous writings like the "Epic of Gilgamesh" and "The Odyssey."

Yoga dates back to about 1500 BCE

The earliest known mention of the word is in the Rig Veda, one of the four canonical Hindu texts. Rishis, or sages, then documented its evolution in the Upanishads, the Hindu scriptures. Much of the modern understanding of Yoga comes from “Yoga Sutras of Patañjali,” which outlines the practice’s eight elements, including physical postures and breathwork.

Near-death experiences have been reported across cultures for millennia.

The ancient Greeks and Romans were known to take vacations.

According to the special theory of relativity, because the passage of time depends on how quickly objects move through space, people will not agree on the order of events they observe if they are moving at different speeds.

Understanding how and when time began requires a theory of quantum gravity

Rewinding the universe to the big bang compresses all matter, energy, space, and time into a single point, necessitating a model that combines general relativity with quantum mechanics. Although physicists understand time to have begun when the universe did, a clear understanding of the mechanisms involved remains unclear.

Modern physics suggests that many universes with different physical laws could exist

Physicists suggest that quantum fluctuations in the early universe could have given rise to these universes. Ancient Greek philosophers like Chrysippus proposed a version of the multiverse over 2,000 years ago—millennia before its adoption into various theoretical frameworks today.

For most of recorded history dreams were considered divine in origin.

India has a century-old parallel form of science fiction

One of its earliest works was Rokeya Sakhawat Hossain's 1905 feminist utopia "Sultana's Dream." This rich visual essay shows how the genre, while taking inspiration from its western counterpart, evolved from India's distinct cultural, social, and political realities.

The Antikythera mechanism: The oldest-known analog computer

A device now considered the world's oldest computer was pulled from a shipwreck more than 120 years ago. Known as the "Antikythera Mechanism," it is now believed to have allowed precise tracking of astronomical positions, and its sophistication overturned understanding of Ancient Greek capabilities.

Experimenting with space-time

Einstein's theory of general relativity—that mass literally bends space and time—can be difficult for the human brain to imagine. This interactive resource lets you create celestial objects, imagine their effect on space-time, and see how they interact with each other (best viewed on desktop).

Branching timelines are allowed and resolve grandfather paradoxes in physics

According to quantum physics, traveling back in time to kill one's grandfather would not cause a paradox because time travel would bring one to a new timeline, where the person killed is not one's grandfather. Alternatively, causality would not be violated because the universe would prevent the murder from occurring.

The grandfather paradox of time travel

If you went back in time and killed your grandfather when he was a child, what would happen to you? One of your parents would never be born, so you wouldn't be born either. But, if you're never born, how could you kill your grandfather in the first place? This so-called grandfather paradox is something physicists, philosophers and sci-fi writers constantly ponder. Read the piece to learn how they've been trying to reconcile it.

Fantasy is heavily influenced by myths, legends, and folk tales

In fantasy, anything is possible, mirroring the supernatural worlds of history’s earliest stories. The narrative voice of fantasy is often similar to early tales, too, with an affinity for the magisterial rather than the contemporary.

The word ‘fantasy’ wasn't used to describe the genre until the 20th century

The word—at least as a word used to describe fiction—didn’t appear in the Oxford English Dictionary until 1949. Scholars believe that’s due to the arrival of the Magazine of Fantasy and Science Fiction, an influential publication, and the rise in fantasy’s popularity following World War II.

The earliest evidence of cancer was found in a 1.7-million-year-old fossil—discovered in the toe of an ancestor of modern-day humans.

A timeline of computer history

The earliest computers bear little resemblance to the computing devices that most people rely on today. This timeline graphic from the Computer History Museum tracks their evolution, from the early days of bulky mainframes that only experts generally used through to the personal computing revolution and on to the modern mobile era. Readers will learn important context ahead of the next major computing platform shift.

Because some models of the universe do not incorporate time, it may be an emergent property born from our limited perception of the universe, rather than a fundamental property of reality.

The 'definitive' history of magic mushrooms

Where did magic mushrooms come from, and how did they get their magical reputation? This article explains the history of the psychedelic fungi from pre-history to now. The earliest concrete evidence of psychedelic mushroom use is 12,000-year-old murals in Northern Australia that portray mushroom iconography. Considering how many species seek out and consume psychoactive substances, such as Siberian reindeer, it's possible human use of these psychedelic mushrooms may predate these murals.

The earliest record of dream interpretation dates to Ancient Sumer, an analysis of a Sumerian priest king's dream around 2700 BCE.

The wave nature of matter can produce phenomena like negative time and retrocausality

Within quantum mechanics, matter simultaneously exists as both fixed particles and extended waves, allowing it to emerge across barriers—just as sound travels through walls—before it fully enters the obstacle. The resulting measurements can show that particles spent negative time within a barrier, with the future occurring before the past.

The hour originated from an ancient Egyptian astronomical system

The movements of astronomical objects, measured in a day and a year, form the foundation of our sense of time. The Egyptians divided each day and night into 12 time eras, using arbitrarily selected stars as references rather than movements of specific celestial objects.

Railroads and long-distance communication led to the development of time zones, with Greenwich established as the prime meridian—the longitude of 0 degrees—due to British advancements in star mapping and navigation.

Human records of influenza stretch back more than two millennia

Accounts of flu-like illness appear as early as 412 BCE, when Hippocrates described a sudden wave of cough and fever. Centuries of recurring outbreaks culminated in the first clearly documented pandemic in 1580, spreading from Asia into Europe and Africa.

Human records of influenza stretch back more than two millennia

Accounts of flu-like illness appear as early as 412 BCE, when Hippocrates described a sudden wave of cough and fever. Centuries of recurring outbreaks culminated in the first clearly documented pandemic in 1580, spreading from Asia into Europe and Africa.

The underlying fabric of the universe—spacetime—changes shape in the presence of mass and energy, which affects measurements of space and time.

Einstein and the fourth dimension

How Einstein's greatest theoretical achievement contains a simple but mind-bending proposition—the dimension of time is physically connected to the three observable spatial dimensions.

The history of the world map

What did people used to think the world looked like? From the beginning of human history to right before the age of exploration, learn how the world maps were created.

No one showed up to the party for time travelers organized by Stephen Hawking

In 2009, Hawking hosted a reception but only sent out invitations afterward, hoping that time travelers from the future would attend and prove time travel possible. He later joked it was "experimental evidence" that time travel doesn’t exist.

Stonehenge has produced wild origin stories

Built before the wheel was invented, Stonehenge inspired increasingly fantastical explanations—from a 12th-century tale of Merlin and Nephilim giants to 1960s claims that aliens built it alongside the pyramids.

The hypothetical particle that travels faster than light

Astrophysicists inspired by science fiction developed the theory of the tachyon—a Greek word for "fast"—which is a field or particle hypothetically able to travel faster than light. Although no experiments have confirmed any part of it, it's a fun theory to consider.

Four astronomical discoveries from ancient Greece

Modern astronomy relies on making discoveries without being present on the planets, stars, galaxies, and other objects studied. Imagine the difficulty the ancient Greeks had studying them without computers and telescopes. Yet somehow they calculated precise measurements of planetary distances, sizes, and more. Read this page to learn more about early triumphs in astronomical science.

Understanding time dilation

The faster you go, the slower time ticks for you. And the stronger the gravitational field acting on you, the slower time ticks for you. These phenomena – collectively called time dilation – were first explained by Albert Einstein’s theories of general and special relativity. In this 11-minute video, beloved astrophysicist Neil deGrasse Tyson explains them to comedian Chuck Nice.

What is space-time?

Space-time is a complex subject, but this Livescience article makes an effort to disentangle the topic. Somewhat akin to a sheet of rubber that can be warped and bent in parts, space-time is a bit more involved that that. However, the analogy makes this and other aspects of the concept simpler to grasp.

Georges Méliès directed what many consider the first science fiction film

The French director was behind 1897's "Gugusse and the Automaton," a silent film that scholars believe features the first appearance of a robot in cinema and one of the earliest films to feature scientific experimentation.

Many believe modern fan fiction began with 'Star Trek.'

The scientific name for northern lights came from two Greco-Roman gods

Although cave paintings may have depicted them millennia earlier, one of the oldest known references to auroras is a Babylonian cuneiform tablet from about 600 BCE. In 1619, Galileo Galilei named the phenomenon in the northern hemisphere "aurora borealis" after the Roman goddess of dawn—Aurora—and the Greek god of the north wind—Boreas.

A timeline of human fossil discoveries

A key part of writing a coherent story about our origins is finding and identifying the remains of our ancestors and understanding their significance. Scientists will not always agree on identifications and opinions will change as new find are made and new ways of studying them are developed.

A cave painting might be the oldest illustrated story ever recorded

A nearly 44,000-year-old cave painting may be the oldest story ever recorded, offering viewers a tale of human-like creatures on a hunt. This article details the discovery of the cave and its archaeological implications.

Dreams have long been used for religious and political power.

Visualizing Einstein's special relativity

Before Einstein developed his theory of general relativity, he worked out what is known as special relativity—or why time is experienced different for different observers. The breakthrough rests on his theory that light travels at a constant...