10 Things Stephen Hawking Taught Us About the Concept of Time Travel

Summary

Renowned physicist Stephen Hawking explored the concept of time travel, highlighting Einstein's theory of time dilation and conducting a party experiment for time-travelers. Hawking suggested that while traveling back in time might be impossible due to paradoxes and destructive radiation, traveling to the future could be achieved through near-light-speed travel or massive gravitational effects. He theorized about the possibility of future time travel using a train circling Earth at high speeds, illustrating the potential for time dilation. Hawking's work, including his contributions to black holes and singularity, has been pivotal in advancing our understanding of the universe.

Takeaways

• 🕰️ Time dilation, as demonstrated by Einstein, suggests that time moves slower for objects moving at high speeds, opening the door to the possibility of time travel.
• 🤔 Stephen Hawking was skeptical about time travel to the past, using a party experiment to illustrate that no time travelers appeared, despite the invitations being sent post-event.
• 🌌 Hawking proposed that tiny quantum tunnels could theoretically connect different times and places, but they are too small for human travel.
• 🚫 According to Hawking, time travel to the past is likely impossible due to paradoxes and the destructive effects of natural radiation on potential time machines.
• 🚀 Hawking believed that traveling to the future is possible, citing the Earth's mass and its effect on time, as well as the example of time dilation near a black hole.
• ✈️ To achieve time travel, a spacecraft would need to reach speeds 2,000 times faster than the Apollo 10, which is currently the fastest manned spaceship.
• 🔄 Hawking introduced the 'Mad Scientist' paradox to argue against the possibility of time travel to the past, suggesting that causality would prevent such events.
• 🌐 The Global Positioning System (GPS) provides evidence of time dilation, with satellites experiencing time at a slightly faster rate than on Earth, supporting the idea of future time travel.
• 🚄 Hawking envisioned a futuristic transportation system where a train traveling near the speed of light could transport passengers into the future.
• 💡 Stephen Hawking's work, including his theories on black holes and singularities, has been instrumental in advancing our understanding of the universe and the potential for time travel.

Q & A

What is time dilation and how does it relate to time travel?

Time dilation is a concept in physics where time moves slower for an object in motion relative to an observer at rest, especially as the object approaches the speed of light. This phenomenon is a key aspect of Einstein's theory of relativity and suggests that time travel into the future might be possible as one could theoretically experience time at a different rate than someone at rest.

What was Stephen Hawking's stance on the possibility of traveling back in time?

Stephen Hawking was skeptical about the possibility of traveling back in time. He conducted an experiment by hosting a party for time travelers and not sending out invitations until after the event, expecting that if time travel were possible, someone would have attended. No one showed up, which he used to argue against the feasibility of time travel to the past.

What is a wormhole and how does it relate to time travel according to Hawking?

A wormhole, as described by Hawking, is a theoretical 'tunnel' in spacetime that could theoretically connect two distant points in space and time. He suggested that capturing and enlarging a wormhole could potentially allow for time travel, but also noted that such a feat would likely be impossible due to the paradoxes it could create and the natural radiation that would destroy it.

Why did Hawking believe that time travel into the past might be impossible?

Hawking believed that time travel into the past might be impossible due to the creation of paradoxes, such as the 'grandfather paradox', where a person could theoretically prevent their own existence by altering the past. Additionally, he argued that natural radiation would seep into a wormhole, creating a feedback loop that would destroy it.

How does Hawking's concept of 'Mad Scientist' paradox illustrate the problem with time travel into the past?

The 'Mad Scientist' paradox is a thought experiment where a scientist creates a device to travel one minute into the past. The paradox arises if the scientist encounters their past self and decides to kill them, which would prevent the scientist from ever creating the time machine in the first place, thus invalidating the initial premise.

What evidence does Hawking provide to support the possibility of time travel into the future?

Hawking points to the Global Positioning System (GPS) as evidence of time travel into the future. The GPS satellites experience time at a slightly faster rate than on Earth due to their higher velocity and weaker gravitational field, necessitating regular time corrections to maintain accuracy.

What is the significance of the Earth's mass in relation to time as per Hawking's theories?

According to Hawking, the Earth's mass has a gravitational effect that drags on time, causing it to slow down relative to space. This effect, known as gravitational time dilation, is a consequence of Einstein's theory of general relativity and supports the idea that time travel into the future is possible.

What is the concept of the future travel transportation system proposed by Hawking?

Hawking proposed a theoretical system where a train traveling at near-light speed around the Earth could function as a time machine. As the train approaches the speed of light, time on board would slow down relative to the rest of the world, allowing passengers to effectively travel into the future.

What is the minimum speed required for a spaceship to achieve time travel according to Hawking?

Hawking suggested that a spaceship would need to travel at a significant fraction of the speed of light, specifically 90% of light speed, to achieve time travel. At this speed, time dilation would be significant enough to allow for noticeable time travel effects.

What is Hawking radiation and how does it relate to Hawking's work on black holes?

Hawking radiation is a theoretical prediction made by Stephen Hawking that black holes are not entirely black but emit small amounts of thermal radiation due to quantum effects near the event horizon. This discovery was groundbreaking as it combined quantum mechanics with general relativity and challenged the prevailing understanding of black holes.

Outlines

00:00

🕰️ Time Travel Theories and Stephen Hawking's Experiment

The paragraph explores the concept of time travel, which has intrigued both the public and renowned physicists like Albert Einstein and Stephen Hawking. Einstein's theory of relativity introduced time dilation, suggesting that time passes slower for those moving at high speeds or near massive objects. Hawking, while skeptical about traveling back in time, conducted a thought experiment involving a party for time travelers from the future, to which no one arrived. He also discussed the theoretical existence of wormholes that could connect different points in spacetime, although they are too small for practical use. Hawking concluded that time travel to the past is likely impossible due to paradoxes and the destructive effects of natural radiation on any potential time machine, but he believed that traveling into the future might be possible due to the effects of gravity and high speeds on time.

05:03

🌌 The Science Behind Time Dilation and Future Time Travel

This paragraph delves into the practical aspects of time dilation and the feasibility of future time travel. It explains how GPS satellites, which orbit Earth, experience time at a slightly faster rate than on the surface due to their higher velocity and altitude. This effect is a direct consequence of Einstein's theory of relativity, which Hawking used to support the possibility of time travel into the future. Hawking envisioned a theoretical system where a train traveling at near-light speed could transport passengers into the future. He also emphasized the need for a vehicle capable of reaching significant fractions of light speed to achieve time travel, using the example of a spaceship that could potentially reach such speeds over a period of years. The paragraph concludes by highlighting Hawking's contributions to science, particularly his work on black holes and singularities.

Keywords

💡Time Travel

Time travel is the concept of moving between different points in time, either to the past or the future, which is a central theme of the video. It is often a subject of science fiction but has also been explored scientifically, particularly in the context of Einstein's theory of relativity. The video discusses the possibility of time travel, referencing both the theoretical and practical challenges, such as the need for speeds approaching that of light and the potential for paradoxes.

💡Time Dilation

Time dilation is a difference in the elapsed time measured by two observers, due to relative motion or differences in gravitational fields. It is a key concept in Einstein's theory of relativity and is mentioned in the video as a foundational element for the possibility of time travel. The faster an object moves, the slower time passes for it relative to a stationary observer, which is exemplified by the video's mention of time moving slower for someone approaching the speed of light.

💡Albert Einstein

Albert Einstein was a theoretical physicist who developed the theory of relativity, which has been instrumental in shaping our understanding of time and space. His work on time dilation is directly related to the concept of time travel discussed in the video. Einstein's theories suggest that time is not absolute but relative, and this has profound implications for the possibility of traveling through time.

💡Stephen Hawking

Stephen Hawking was a renowned theoretical physicist who made significant contributions to our understanding of black holes and the nature of the universe. In the video, Hawking's skepticism about time travel to the past is highlighted, along with his thought experiment involving a party for time travelers. His ideas about the potential for time travel into the future are also discussed, showing his influence on the topic.

💡Wormholes

A wormhole, in theoretical physics, is a hypothetical topological feature of spacetime that would fundamentally be a shortcut through space and time. The video mentions wormholes as a potential means for time travel, suggesting that they could link separate places and times. However, Hawking also theorized that the natural radiation in a wormhole could prevent its use as a time machine.

💡Paradoxes

A paradox is a statement or situation that seems self-contradictory or logically impossible. In the context of time travel, paradoxes often arise when considering scenarios where actions in the past could affect the present in ways that are logically inconsistent. The video references the 'Mad Scientist' paradox, which illustrates the potential logical problems with traveling back in time.

💡Black Holes

Black holes are regions of spacetime where gravity is so strong that nothing, not even light, can escape from it. They are mentioned in the video as a context for time dilation, where time would slow down for someone approaching a black hole due to the immense gravitational force. This concept is used to support the idea that time travel into the future might be possible.

💡Speed of Light

The speed of light in a vacuum is the ultimate speed limit in the universe as described by the theory of relativity. It is approximately 299,792 kilometers per second. The video discusses the necessity of approaching or reaching the speed of light for time travel to be feasible, as this would allow time to dilate significantly, enabling travel into the future.

💡Global Positioning System (GPS)

The Global Positioning System is a satellite-based navigation system that provides geolocation and time information to GPS receivers anywhere on Earth. The video uses GPS as an example of time dilation in practice, explaining how the clocks on GPS satellites run slightly faster than clocks on Earth due to the difference in their relative velocities and gravitational potentials.

💡Hawking Radiation

Hawking radiation is a theoretical prediction that black holes are not completely black but emit small amounts of thermal radiation due to quantum effects near the event horizon. This concept, proposed by Stephen Hawking, is mentioned in the video as one of his significant contributions to theoretical physics and our understanding of black holes.

Highlights

Time dilation, as demonstrated by Einstein, suggests that time moves slower for objects traveling at high speeds.

Stephen Hawking was skeptical about time travel to the past, conducting a party experiment to illustrate this skepticism.

Hawking proposed that time has 'wrinkles' and 'voids' that could theoretically be used for time travel.

Traveling back in time may be impossible due to paradoxes and the destructive effects of natural radiation on wormholes.

Hawking believed that traveling into the future is possible, citing Earth's mass and its effect on time as evidence.

The fastest manned spaceship, Apollo 10, is far from the speed required for time travel.

Hawking introduced the 'Mad Scientist' paradox to argue against the possibility of time travel to the past.

The Global Positioning System (GPS) provides evidence that time runs faster in space than on Earth.

Hawking imagined a futuristic train system that could travel at near-light speeds to transport passengers into the future.

The speed of light is a significant barrier to achieving time travel into the future.

Hawking's contributions to the understanding of black holes and singularities have been monumental.

Hawking's work on Hawking radiation and singularity theorems has greatly advanced our knowledge of the universe.

Hawking's educational efforts, including books and television shows, have made complex scientific concepts accessible to the public.

Hawking's theoretical prediction that black holes emit radiation has been confirmed and named Hawking radiation.

Hawking's work on the nature of time and its interaction with mass and gravity has profound implications for our understanding of the cosmos.

The concept of time dilation and its implications for time travel have been central to Hawking's theoretical work.

Hawking's party experiment for time travelers highlights the practical challenges and philosophical questions surrounding time travel.

Transcripts

The possibility of time travel is often debated and theorized by laymen, but it has also garnered

the attention of the titans of physics.

Ever since Albert Einstein demonstrated that time dilation is a real thing, speculation

has grown about the possibilities of time travel.

Einstein’s work illustrated that the faster someone travels, and the closer they get to

light speed, the slower time moves for that individual.

All the while, time continues to move at the same pace for people on Earth.

Stephen Hawking, the world renowned theoretical physicist, did not shy away from the growing

speculation about time travel.

10.

Champagne Party

Let’s just say Stephen Hawking was a skeptic when it comes to traveling back in time.

To make his point, he conducted a simple, but elegant experiment.

He held a party.

That’s right, in 2009, Hawking decided to host a party with balloons, hors d’oeuvres,

and champagne for guests willing to travel back in time for the party.

Hawking told reporters, “I gave a party for time-travelers, but I didn’t send out

the invitations until after the party.

I sat there a long time, but no one came.”

The Discovery Channel was there to capture the event at the University of Cambridge,

in the event that someone happened to arrive.

Hawking even made sure to provide precise GPS coordinates, just in case someone became

lost through space time.

9.

Time Machines

Although Hawking was immensely skeptical of the possibility about traveling back in time,

he was willing to engage in the notion.

According to Mr. Hawking, everything including time itself has wrinkles and voids in it;

there are tiny tunnels in the quantum world that form, disappear, and reappear.

Theoretically, they would link separate places and, most importantly for time travelers,

time.

However, these wrinkles and voids on the quantum level are far too small for a human to pass

through.

A time machine that wanted to attempt such a feat would need to capture and enlarge a

wormhole enough so that a spaceship could travel through it.

If such a device were to built, Hawking said, “One end could be here near Earth, and the

other far, far away, near some distant planet.”

8.

Time Travel into the Past May Be Impossible

After his theorizations, Hawking concluded that traveling back in time is probably impossible.

He believed that the wormhole would create paradoxes that would prevent it from being

created in the first place.

For example, a person traveling back in time and killing themselves before the creation

of the time machine.

More importantly, Hawking argued that natural radiation would seep into the wormhole and

the resulting feedback would be so strong that the wormhole, and thus the time machine,

would be destroyed.

He went even further, suggesting that the creation of such a device may have dire effects.

Hawking believed it may trigger a bolt of radiation that would not only destroy the

time traveling spaceship, but space time itself.

7.

Traveling into the Future

Although Hawking didn’t believing traveling back in time is possible, he did believe that

traveling into the future is possible.

An example he cites is the Earth’s mass dragging on time.

If the Earth was approaching a black hole, time would slow down for people and the force

of gravity would increase.

Naturally, a black hole is a dangerous method so Hawking proposed the potential of traveling

near the speed of light.

As one nears the speed of light, Hawking argued, time would slow down in order to protect the

speed, and also to make it physically impossible to ever break it.

Therefore, Hawking believed, “that a human traveling near the speed of light could reach

the end of the galaxy within their lifetime.”

6.

The Spaceship

The fastest manned spaceship was the Apollo 10, and it climbed to a speed of 25,000 mph.

In order for time travel to be possible, humans would have to design a spaceship that travels

2,000 times the speed of the Apollo 10.

That’s… that’s pretty fast, you guys.

It will also need absurd amounts of fuel to make it through a wormhole while not sacrificing

any of its speed.

It’s unlikely that even Elon Musk will be able to accomplish this feat in the coming

years, but someday it’s certainly a possibility.

5.

Paradoxes

Hawking came up with his own paradox named the “Mad Scientist” paradox to further

describe the unlikely possibility of traveling into the past.

He assured us that he didn’t like the stereotype that scientists are “mad,” but in this

case he agrees that the misconception is real.

Suppose that this scientist created a device that would allow himself to travel just one

minute into the past, witnessing his alternate self.

What would stop this mad scientist from killing his earlier self?

Hawking argued that the mere possibility invalidates the fundamental principle of the universe

that cause happens before effects.

Hawking said, “I think something will always happen that prevents the paradox.

Somehow there must be a reason why our scientist will never find himself in a situation where

he could shoot himself.”

4.

Global Positioning System

Unlike many of his colleagues, Hawking firmly believed that time travel into the future

is possible.

Hawking noted that Albert Einstein was the first to fully grasp the concept of time and

prove that there are places where time slows down and others where it speeds up.

As a result of Einstein’s work, Hawking was convinced that traveling into the future

was possible.

Hawking suggests that a fuller understanding of Global Positioning System (GPS) is all

the proof necessary to conclude that future time travel is possible.

A network of satellites orbiting around the Earth make satellite navigation possible.

They’ve also revealed that time runs faster in space than on Earth.

The satellites contain very precise clocks and yet, “they all gain around a third of

a billionth of a second every day.”

The system has to correct for the drift, otherwise that tiny difference would upset the whole

system, causing every GPS device on Earth to decrease in accuracy by about six miles

a day.

Some might suggest that the problem lies with the clocks, but the truth is that they run

fast because time itself runs faster in space than on the blue planet below.

The Earth’s mass literally drags on time, slowing it down like a stretch in a river.

Einstein understood this better than anyone, and Hawking believed that his scientific predecessor

proved that time travel into the future is possible.

3.

Future Travel Transportation System

Hawking not only gave us hope that time travel is possible, he dreamed up a system of traveling

into the future.

Science fiction writers take note.

Hawking imagined a train track that goes around the Earth.

This particular train would need to get as close as possible to the speed of light in

order for it to become a time machine.

Passengers on this train would have a ticket to the future.

The train would accelerate around the Earth again and again, getting faster and faster

each time.

As the train gets close to the speed of light, time will start flowing slowly on board, relative

to the rest of the world.

Hawking predicted everything on the train would go in slow motion.

If said train left the station on January 1, 2050 and circled the Earth over and over

again for 100 years, before coming to a halt on New Year’s day 2150, it would only feel

like a week had gone by for our passengers.

They’d leave the train having traveled 100 years into the future.

2.

Speed of Light

The biggest obstacle in our way of traveling into the future is manufacturing a vehicle

that can travel extremely fast.

Not Ferrari fast, or spaceship fast; we’re talking speed of light fast.

As mentioned earlier, if a spaceship were constructed it would need to go significantly

faster than the Apollo 10, the fastest manned ship on record.

Hawking supposed that based on the ship’s size, it would take awhile to reach the speed

necessary for time travel.

After one week, according to Hawking, it would reach the outer planets, then after two years

it’d reach half-light speed and be outside our solar system.

Finally, after two years it would be traveling 90% of the speed of light.

That would place the ship’s passengers 30 trillion miles away from Earth, and the ship

would finally begin to travel in time.

“For every hour of time on the ship, two would pass on Earth.”

1.

Stephen Hawking

There are few who did more to make the most obscure and complicated science accessible

for those who wanted to learn more about our universe.

Stephen Hawking did it all; writing books and creating televisions shows that helped

educate the masses.

One of his greatest contributions to his field comes in his expertise on black holes.

Hawking made a theoretical prediction that black holes should emit radiation, which is

now known as Hawking radiation.

His contributions to singularity also cannot be understated, working on several groundbreaking

theorems.

Hawking was a titan in his field, and there’s been no greater voice in understanding the

cosmos, and man’s place

in it.