Neil deGrasse Tyson - Can We Go Back in Time Using a SpaceTime Machine? 

On the bright side, at least we can go back in time in a way through RU-vid, music, movies, and art

As a kid I wanted to go back in time to see a dinosaur. Now I wanted to go back in 2020 to appreciate, and save someone. I would do anything to bring him back. I just wanted to see him even one last time.

"I want to go back in time. Not to change anything, but to feel something again.”

I desperately wanna go back to January 2019 to enjoy my good times again. I really wish we can refresh time and enjoy life again.

I desperately want to go back in time.

If going back in time is possible, then that means the past still exists. If the past still exists, then that means we are functionally immortal. We exist within our frame of reference ( our lifetime) and we always will.

Neil explains in a way that anyone can understand 🙌🏽

I love to listen to Neil explain stuff. Most of the time it's a struggle just to keep up but every now and then a light goes on in my brain (which doesn't have any of this higher knowledge in it) and I actually understand and see what he's saying.

Time travel is such an interesting topic

Blows my mind how our interpretation of the universe mathematically makes us right in solving and making calculations on hypothesis

Would have loved him as a science teacher

I wish the same. My fiance just passed away and not even have the time to say goodbye. She died before I can say it one more time😢😢😢

I always assumed that if you managed to go back in time, you'd probably be in a separate reality, not the original one you were from. Basically a branched reality where things and events transpire differently. That would explain the grandfather paradox.

A new thing I just thought of: what if it's only possible to view the past, but the second you stop moving, your real time catches back up with you?

I wonder if this could be done on a "micro" scale instead of using light years and endless space (not knowing exactly where you will end up) but something much smaller where you could control precisely where you enter and exit the "wormhole" in question required to travel back and forth in time (miniature black hole etc)

I have a very basic question that I have wondered for a very long time. If I travel at the speed of light from earth. This would mean everyone on earth is also travelling at the speed of light relative to me. So how can my clock tick slower (or not tick at all) while Earth's clock tick normal. I mean why would time stop/slow down for me and not for Earth? Why and how would I travel in future in that case? I mean who is to say who is travelling at the speed of light? Since it is all relative?

A hypothesis: time does go backwards but that started with antiparticles at the "big bang" and they are going backwards in time from there, we only can see the forward traveling particles. We can see the backwards type particles very rarely but most are at the other end of time.

I think the paradox would be dealt with, IF each movement back in space-time then created a whole new branch of space-time at that point. So, you go back to 1900 and from that point there becomes now two divergent space-time branches. The original branch then remains unchanged because your self is no longer on that branch after whatever point you leave. Each time you move forward or backwards a new branch is created, meaning you keep moving `forward` in a relative sense through each new branch you create, regardless of where it is on the timeline. In that case, you could kill your parents before they had you and avoid a paradox, because `you` weren't born on the space-time branch you killed them on and *that* space-time branch still exists unchanged to the point you left it. There's not a shred of scientific evidence to support that idea though, so it's kind of just mental fluff. What would it take to overcome that paradox?

I have no real interest in actually learning about space but boy do I enjoy listening to Neil explain things.

it’s super sad and corny that i even searched this up, but rn i’m at a moment in my life where tbh i need this. last summer i was the happiest i had ever been, and its been killing me that i took that time for granted. there were people and different aspects of life during that specific summer that made me just extremely happy, but now i feel as if i can’t get that feeling back again. friends tell me “oh yeah it was just your ex” but if anything she’s just an aspect of that. life isn’t the worst right now and i’m happy that i met people on the journey to where i am right now, im just not as happy as i was back then, and i can’t stress how happy i was. i hope someone can relate to this because honestly i haven’t put this much thought into a comment ina while lmao. TL;DR, i searched up how to time travel stupidly because i miss a period of my life from the past.

Traveling at the speed of light is the most difficult part. Everything will seem stretched out and that'll make if almost impossible to physically locate where you wanna go in time. Unless the machine is preset to that particular place and time.

I like Doc browns explanation (basis in fact or not) of sending Einstein (the dog, not the physicist) one minute into the future, so that he skips over that minute, and reappears when Marty and Doc's (perception of) time catches up.

This is fascinating!!! Time travel has always been the most interesting scientific possibility for me!!!

Neil is one of my favorite people in the world! I think that if everyone would listen to him, instead of what's "self-destructive" in the world, we would have a chance at world harmony. He brings harmony into the world with his knowledge and character.

So are we really traveling into the future, or are we really experiencing time differently?

Lets get one thing straight. If you could travel faster than light you would indeed be traveling backward in time. However it is IMPOSSIBLE to also remain in the same place. In other words you would not be able to travel through time alone. Which means you will always travel a DISTANCE in order to go backward. If you tried to return to your starting position you would in fact have to travel through the Bulk( If it is a thing anyway). The only way that this works is if you travel to a distant point faster than light,( So you travel back in time) then you would have to turn around and travel back to you starting point at sub-light speeds taking the length of time equal to the distance traveled. The wormhole is only possible for that brief period that you travel at FTL speeds. You would end up at your destination near instantly. At least this is the way I think about it. It could also be the case that the only way to travel through time is to use an engine that would instantly launch you through a wormhole to the same point in space but backward in time, however this would require all the energy of the universe, I suppose it might be possible to only create a local distortion but I doubt it. Locally it would create a new separate timeline, if in fact you could build up enough energy sitting still (relatively speaking) to instantly launch into the past. It would have to be a instant transition otherwise you would end up as paste on the bulkhead. I still think my first thought is more accurate though

Time is a noun that we created. Saying you can go anywhere in time is like saying you can go in feet or meters. They are also nouns we created. Time is the distance between 2 events. Just like meters is the distance between 2 points. It's a measurement, that's all.

Great video. Thank you for sharing this that was very interesting and fascinating.

I believe there is a theory that, with a block universe (past present and future all exist), you or something going back in time would have already done that, thereby solving the “grandfather paradox”. In effect, the universe and causality may be “protected” up until the point that a Time Machine is invented or, say, a black hole “time Machine” is used. But that just how I unrest and it. Isn’t the dunning Krueger effect awesome? Lol.

Time dilation is something to avoid with FTL travel, I mean you want to get home when all your loved ones are still alive or the entire human race for that matter. So, faster than light without time travel.

I have been diagnosed wth Huntington in 2010. I went through a series of unfortunate additionate events (for one, i have food allergic allergies after forgetting to take a medication). Would love to return to 2009 to make things easier)

Pls do and stay there, Neil.

Its so fascinating to listen about time travel, thanks for such content. If there is indeed space time to be invented in future, it could be done outside Suns Gravity field where Voyager are travelling now. If somehow we get something stationary at Sun's Lagrange point and shoot anyone back to earth by heavy detonation to move anything back to earth from there, they could have experienced huge time travelling, if i'm not missing. Till next century humans may get that technology. Hopefully if survive.

Time isn’t linear, humans just perceive it like that because we are born, live and die creating a past, present and future but time and space are one it exists all at once.

When I first began to learn programming I wrote a python script to calculate time dilation when traveling to and from alpha centauri and one of the things I observed was when moving at 99% the speed of light any small increments to speed can yield massive differences in the result. Now this was years ago but I somewhat recall the result was like 125K years into the future moving at 99% but as soon as I start adding that .9's I was easily able to produce leaps in the millions.

i need to go back in time now more than ever.

I believe that if you go back in time, whatever actions the future you takes in the past creates a different timeline separate to the one you traveled back from.

We like to dream of going back, but it usually implies being young again and avoiding the mistakes we made. I'm reminded of the old Twilight Zone episode "Of Late I Think of Cliffordville," which turns out rather badly for the time traveler.

I love listening to Dr Tyson!✌️

The Paradox that no one talks about in travel across temporal regions is that the organization of matter is typified by the expansion of space and time. Whereas matter from a more distant space-time expansion traveling to a past space-time point would not fit or resonate the matter itself would not interact properly with matter temporarily compressed to its viewpoint

Well ya gotta remember that what we think of as the past present and future actually ALL coexist simultaneously. We only conceive those notions because of the speed of light. So if you were to “go backwards in time” you wouldn’t be aware of it - you’d literally be reliving the “past” all over again - making the exact same choices, meeting the exact same people etc. This is why you couldn’t go back and change things. This is also why you can’t go back to a time before you were born.

You don’t go back in time, you can catch up the past if you go faster than the speed of light. When you overtake the past, turn back or stop to see the past. You than can only see it but not interact with it as you see in movies!

It's too difficult to imagine to time travel to the past. How do we travel back in time physically? How do we set specific day/time? Where on Earth will you locate? etc... First we must figure out how to travel to the past, then a million more questions to answer.

Time that has passed no longer exists.... You are constantly moving into time as it is created and passes.

Time is fascinating. I worked the subway stations for nearly 10 years. From one end of the city to the other. Every so often I would notice the city would be saying that, "Today just flew by" or "The day was just dragging along." How can an entire city complain about the same time paradox unless it was effected by it. Maybe a time distorted bubble the earth passes through in its revolution around the sun. Maybe random waves of time distortion hitting the earth? Maybe they're randomly given off by the sun. Maybe they're from outside our Terran system and reach us in intervals. ???? Ti-i-i-ime, is on my side. Yes, it is!

Time Travel I Wanted To Go Back In 1989!

9:17 addressing that paradox what if you did travel back in time but shifted to a parallel universe of course for me it raises the issue of Free Will and our ability to affect events in the universe (time) if the universe has already accounted for any action you may commit.

Awesome. I understood nothing from this video.

Absolutely. Every time I go to sleep and dream about the past I’m going back in time using my very own personal Time Machine. 😆

is 1/4 pi effectively quantum pi? where half pi is a fixed measurement? at plank

I don’t think the question is only whether you can travel back or forwards in time, but if you can, how you then stop in order to do anything worthwhile in the new time you arrive at. You could theoretically travel so fast to travel forwards in time, but you won’t be then in the same place you started at anyway.

Cant tell me I cant go back in time...I just watched a recording/video you made 3 days ago. Now I'm commenting on it. Light and sound waves can be captured onto film and played over and over again....the past constantly being witnessed in the present. Half the stars in the night sky are dead, but ironically thier light still glows brightly. As for interacting will the past...what di you think I'm doing now or should I say was doing🤣

i want see my child hood time early 90s

So if you were one light year away from Earth and had a ship that could travel up to light speed, is it true that the minimum time in years on Earth that would pass while you were getting back is ten?

Fun fact: when you look in a mirror - you are looking back in time.

In terms of paradoxes i believe the universe is what it is, we as humans give ourselves to much importance, so, to me, if we travel back in time we would just erase our original timeline but it wont destroy the traveller

The "my mix" playlist went Dj Screw, Tron derezzed, dj screw, Damian Marley, Niel Degrass Tyson. That's a chill party.

Regarding the grandfather paradox: what if all of time -- past and future -- has already been written and set in stone. I.e. we experience the present moment, but our future is already predetermined. That means, if someone were to go back in time and prevent their own birth, they simply would not exist and so that possibility is wiped out in the first place -- meaning NOBODY has the ability to even attempt that in our universe. However, if someone went back in time and did not affect anything with their birth, then this is allowable and so this person may exist. Basically, anyone that decides to affect their own birth via backwards time travel must fail, or else we wouldn't know about them as they would not exist in our universe at all. There may be people who want to meet their parents, but they would fail to prevent their own birth. It's the only logical way that this paradox can be explained whilst permitting backwards timetravel. In summary, the life you are experiencing right now is only possible because you and nobody else in humanity went back in time to do anything that prevented you or them from being alive.

You can go control the time factor all you want in reality... if you wanna go back in time, just think of a memory and there you go, right into the past... or if you wanna go forward to the future... just wait 1 second and there you go hahaha

If travelling in the past were going to be possible at any time even in the distant future, our future selves would have already visited us. 🤟

In other words, we can go forward in time from the present and the future would become our present, then we can travel back to when we left, making it our "past" but only at the time which was once the present we left.

Going back in time would be cool to see all the people I have lost. Meaning the ones that died to early. But I wouldn’t want to stay in that time frame though. Because one I would see my younger self and there is no room for two of me. Also all the people that love me and ones I love are in this time line. If I can see the ones I lost one more time just to give them a hug…. That would be wonderful and thinking about that right now has me in tears.

If the possibility of traveling back in time exists, there can be no paradox.

Title of the video : can we move back in the time? 80% content of the video: How can we move forward in time?

It is indeed possible to travel backward or forward in time, provided the space craft the passengers that are on board is powered by dilithium crystals to propel the conveyance to the chosen direction of destination. Should the craft experience dire malfunction during transit due to overheating, the auxiliary emergency power unit may always be engaged to carry on with the long arduous journey. 🤔

So is light itself time traveling? Is the light we see from stars in the future or the past?....or the present? Does the time traveling component of the light from stars cancel out the fact that the light from them is from the past thus making it from the present?

My understanding of wormholes is that they are so unstable in theory that the mere act of entering it would cause it to collapse making it essentially useless for any kind of travel.

We need to be able to travel at 10x the speed of light to time travel wormholes are too rare to rely on.

If time is traveling in waves like in the water, that means past exist. Not only do the past exist in this scenario, also alternative worlds because new waves will form just like in the ocean. It goes and come back again and again etc.

What if all time is NOT singular and linear, but exists in parallel? If I were to travel back in time, for example, me, I am still progressing forward in my own timeline, but I am doing so from a relatively prior branch point in another timeline. I could, then, alter things in the second timeline, without affecting my initial one. A new question is: From the second timeline, can I ever branch back to my initial line, or as I continue to progress, instead, branch to a third timeline?

My theory is time travel into the past is possible and even if we changed something that happened in the past there is a way that things could work out without causing any paradoxes. For example, let's take the famous grandfather paradox. Let's assume that someone has traveled back in time and killed his grandfather. In that scenario, his actions won't be affected to his timeline or future. It will only make a branch alternative timeline, which is connected to the main timeline, where his grandfather is dead. In that way they all make sense.

If somehow I could go back in time into my former body and take certain possessions I have now, I would *love* to travel back to 2008.

When I want to go back in time, I watch old black & white 1930's movies. They're a way to look into the past, way before I was born.

Superb video we need more like this explanation ❤

We can't go back to the past, but we do repeat it.

Of course we can go into the future, we're doing it now. But backwards? .... Maybe in the quantum realm with retrocausality.

I find it almost amusing, that videos like this, kind of imply that one day, maaaaay be, we could. However, the theory about that is that if one day we did, we'd have known about it by now

I don’t think it is possible to physically go back in time, although I wish it were. If it was possible it would really mess things up. However, I do think it is possible to view the past. I really hope I live to see this come to fruition.

What about going to the past by reversing your entropy?

If you could travel back in time. Would you experience an unending sense of Deja Vu? Since you would be putting yourself back in a point in time that you have already lived.

Even if you, for example, travel fast around the earth? Would you still go to the future while people in a stationary position - let's say, some one in an stationary "satelite ship" at the same orbit as you, but in a stationary position in reference to earth's rotation?

The question is:Will this time machine be the type that goes to a time togheter with the person who traveled? Because if not, how will the person go to a time and come back?

Every time you sleep, your mind leaves the present, then travels in the future but your body advances through the normal flow of time. At wake moment, your body catches up with your mind. Time travel is not yet a scientific reality but it is a spiritual one. 🤭

The grandfather paradox is simple, if you went back and stopped your parents from meeting eachother it would change that timeline but not the one you lived, so you would still exist in your own timeline!

Its about time i started sharing

Flight of the navigator movie covered future travel very well.

If there was something that forced you to land outside your past light cone when you travel to the past, then the Grandfather Paradox is solved, too. Isn't it?

The simplest example of why backwards time travel is impossible is if it were, we would certainly have been visited by future time travelers, and probably often.

Thank you mr.neil for this video i wish time travel was possible i wish to visit my mom in 2004. Before she past away from leukemia

I really want to go back in time ⌚

Thanks again that was very awesome to see

You want to be careful going through wormholes. John Crichton went through one and his life was turned upside down. Two species that were warring with each other both chased him everywhere to get his wormhole knowledge. On the positive side of things, he hooked up with a really hot alien girl that sounded very similar to an Australian.

Pink Floyd explains TIME ,On the Dark side of the moon album. I'm staying with that explanation. Love and peace from Perth Australia 😎💕🖐🎶🎵🎶

"We can easily move forward in time" [shows picture of a spaceship that looks vaguely like an Imperial Star Destroyer] The one thing Star Wars doesn't have is time travel. It would have made more sense to show us the Enterprise, which has travelled in time (usually backwards, but it always manages to return to the present) more than once.

I can confirm that time travel is possible as I am from the year 2250 and through the theories explained here we were able to go back in time. This has proved useful as hopefully in the past we can prevent the current future from occurring as the lizard people have taken over and I was sent in the past to prevent them from taking control.

If you go through a worm hole you haven't traveled faster than the speed of light as the path you took to get there was effectively shorter. Yes you could arrive there faster than a beam of light seeing off from the same point, but you haven't traveled the same distance. It would be like 2 runners on a running track, one runs around whilst another walks across the middle, they didn't go the same speed

I would love to go back to when my children were still kids

slowing your rate of aging or making your clock tick slower isn't traveling into the future. do you think the items in your freezer are traveling into the future? do you think you're traveling into the future when you go to sleep at night? As I see it, time is just the product of us keeping track of changes. it's not some dimension that we can travel through or anything can extend into. everything is very much stuck in the present. your claim of being able to travel into the future is limited to moving a few nanoseconds, a negligible about of time that is very easily inside any marine of error, if you travel at or faster than the speed of light, which is a very impossible feet.

Thanks to Donald Trump, we have gone back 150 years.

oh so thats why i'm in the future of my gps navigation.. it always tells me to turn left or right some time after i should have done it.. amazing and sometimes i will text my mom before she ask me something