The Physics and Philosophy of Time Travel

What if everything we know about time is merely an illusion? Could find a way out of it, by breaking the construct of how the universe progresses? And so, would it be possible to break the natural flow of time?

If you'd like to see more of this kind of video, consider supporting our work by becoming a member today!

Visualization of the Gödel universe

Miguel Alcubierre TEDx talk (in Spanish)

Table of content:
0:00 Opening
1:16 Defining time travel
4:37 Attempts to time travel
6:33 Intelligibility of backward time travel
7:49 Can we break the causal chain?
9:14 Closing

Credits:
Producer: Harry Dewang
Assistant editor: Aulia Prasetio
Motion graphics: Aulia Ramadhan

-----------

Script:

Often when people hear the term "#TimeTravel," it is in relation to a person going either forward or backwards in time, without any physical changes to their body. It would be funny if you travel back in time to see a baby version of you, 20 years ago. But instead, when you jumped out of the machine, you are in the shape of a baby, just like the one you’d like to see in the first place.

In our understanding of the normal flow of time, we are actually moving from the past to the future. There are different interpretations of this, but what people usually refer to as time travel usually means either getting to the future faster or travelling into the past. In any case, instead of the normal flow of time, we change the rate by some X amount.

According to Newtonian mechanics, we either perceive time as linear and deterministic. But ever since Albert Einstein published the theory of relativity, the Newtonian conception of absolute time and space has been replaced by the idea that time has a subjective significance to everyone. In this case, time is one dimension of space-time in special relativity (SR). And of dynamically curved space-time in general relativity (GR).

From here on, the possibility of moving backwards or forwards in time might not be as farfetched as one might think. In this case, it might just be as simple as how ordinary beings can move between different points in space.

There are many different hypothetical answers for time travel, and over the years, those scenarios have been put forward by notable scientists. Essentially, these scenarios are different from the notion of a physical machine with levers and dials that H.G. Wells proposed.

Einstein also previously showed that time actually runs differently in different situations. This basically implies that time passes at different rates for different observers based on their travelling speed.

Here’s a very interesting example. The astronauts onboard the ISS orbit the Earth at 28,000 km/h (17,500 miles/h). Taking into account the conflicting factors of GR and SR, we’ll get the net time dilation effects on the astronauts with respect to an observer on the planet’s surface.

The astronaut onboard the spaceship will get a #TimeDilation of -0.000026 seconds per day. For a typical crew member who stays on the ISS for 6 months, the total time dilation would be about 5 milliseconds. In such a case where the astronaut has a twin, the astronaut has experienced less passage of time than his twin counterpart who remained on the Earth’s surface.

Giving the option to fast-forward through time is a pretty cool idea. Though it would be a one-way process where you wouldn't have the chance to go back. There might, however, be some scientific basis within the theory of relativity, supporting the possibility of time travel under certain scenarios.

There was a scientist named Kurt Gödel in the early 19th century. He showed that there are some solutions to the field equations of GR. It describes space-time so warped that they contain “closed time-like curves”. This is where an individual time-cone twists and closes in on itself. It allows a path from the present to the past or to the future.

Since we're on the topic, we'll mention a few notable attempts by popular scientists on time travel.
In 1994, Theoretical physicist Miguel Alcubierre proposed a speculative scenario. This involves a spacecraft that would contract space in front of it, and expand space behind it. If this shortcut is taken, it will result in effective faster-than-light travel. You might even be able to use it for time travel.

Other theoretical physicists have been thinking about these kinds of shortcuts as well. For example, Kip Thorne and Paul Davies think it's possible to use a wormhole and travel through space-time. In a similar way as GR could be used to make instantaneous spatial travel plausible.

[BeeyondIdeas]

Thanks for watching the premiere and interacting on the live chat ✌

[CherylSlane-lhcy]

Actually, once back in the spirit world you have the ability to travel to any dimension you put your thought to. I’m always interested in this stuff never the less. ❤

[juanmaya]

I just started studying physics and astronomy and as little as Ik about both I fully understood this very informational tbh

[mohammedanwar]

Your videos are very informative regarding complex topics in Science. You explain it in simple terms, which makes us to grasp it better. Keep making such content.

[resmirk]

You explained everything in a very interesting way, it would be better if you could add subtitles to the videos. Thank you 😄

[ashmomofboys]

Just discovered your channel and I’ll be binge watching it all night. Good stuff!!

[phelliskepler]

This video has made me understand the time travel concept. Continue the good work.

[pointofsale]

That was cold AF! My guy the causal loop explanation blessed me for sure. Keep this up my guy

[InterstellarManish]

In the darkest if night, after completing my studies I came here to this video and it opened up my tired and sleepy eyes to accept the scientific and yet to believe truth about time and why can't we move backward to time. Thank you so much brother for your creations. It's time to dive deep in the dreams of future 🙋🏻🤯⚡

[ChristianIce]

If traveling back in time was possible, we would have known already.
You don't have to wait a distant future for an information that could have been relayed to the past.
The other option is that travelling back in time is possible, but strictly forbidden by the Federation of Planets :)

[oldsoldier]

See, the problem here is the assumption that time is ONE dimension of space-time. Time, like space, is actually 3-dimensional. But, we’re only capable of perceiving that one, linear dimension. We’re we able to perceive, and access, the second of time’s 3 dimensions, we would be able to easily shift forwards and backwards through time. Add in the third temporal dimension, and we’d be able to shift “sideways” into alternate timelines. Ancient Greek mathematicians understood the concept, but only bits of their knowledge remain. It’s a puzzle with many missing pieces.

[kameshparashar]

I love how he gave the example of bootstrap paradox using DARK Web Series

[tvb]

Can we all agree that this channel is CRIMINALLY underrated.

[spacify]

Continue making these type of videos. Your videos are really amazing to watch. And this video was well awaited by me and a lot of your subscribers. Though, I have one doubt that - Can't we travel forwards in time already? (Like we see in the case of astronauts who remain for very long periods in space)

[douglasking]

I love the analogy of the time traveller who steps over a time zone dimarkation and back again to 'travel in time'. I know that is not representative of time travelling per se, but at least it's fun.

[rickrobitaille]

Went to a book store today..Chapters and saw a new Steven Hawking book..2021..thankyou 🌐

[tahaabumaye]

Yo, we see ourselves travel in time in video recordings. It's super true because you can watch my recordings on YouTube and rewind it and you'll see me go back in time.

[johndoe-nrju]

I see time travel as you could go to an alternate timeline and do things that were meant to happen (last of present), but you can't change what has happened.

The big hurdle would be finding a close enough timeline and it's position in space considering the universe is expanding and we are rotating a star, rotating a black hole.

[pabloleopold]

Time-travel philosophy is the biggest proof of how amazing the human mind's imagination is at creating things😂😂✌️

[darianaugustine]

MIB 3 did a great job creating a part of this