May 19, 2010, at the Linda Hall Library of Science, Engineering & Technology
Science fiction has introduced us all to the idea of traveling into the past - but is it really possible?
Sean Carroll, Research Professor Physics at Caltech, explores how time travel would possibly work in the context of Einstein's theory of general relativity, including the hypothetical idea of wormholes connecting distant regions of space. Dr. Carroll also discusses the logical structure of time travel, and what it implies about predestination and free will. In the end, time travel is probably not possible, but by taking the idea seriously we help understand how the universe works.
Ah way back when Sean was still in the 4:3 timeline.
And somehow it seems right.
That's actually a 4:3 ratio
i wish i could go back in time and give this man a glass of water
It's on the podium with him already lol
@@joshuaadams3891 Wasn't there for a couple of months
i think it’s great we still have videos like this around from before we could time travel
Right? And floating skateboards.
😆
To quote Douglas Adams, time travel was discovered simultaneously at every point in the time continuum.
I love how his words are mainly used to justify more words and some more words . It’s kind of like he is just stood there chatting sh*t.
@@transatlanticsilkcottonfabrics the results of time travel are all decided by what type of imaginary time travel people are dreaming about!
Work: “can you be here in 20 min?” Me: “That’s outside my light cone”
technically you cannot here the voice of somebody outside your light cone, nor you have any information about them or their reality
@@Staarkalinou good one.
Dude…your light cone is showing..
rkalinou 😢H09=❤
You're fired
I watched this at 2am while drunk hoping it would lull me into sleep but it was so interesting I stayed awake for the entire lecture. There's something about the way Sean Carroll talks that really resonates with me.
I made a travel back in time in the year 2010 and was able to see a conference of S. Carrol...
On KZhead 😂
And you weren’t able to do anything to change it 😅
@@dfv15 I just listened, had no questions..
It must have been a great trip and experience! Good for you, wish he would come to a place near me
What if you went back in recent time and killed yourself (before you lost all that crypto with FTX) and then replaced yourself and make a better financial decision?
I wish KZhead would remember the timestamp that i fell asleep at so i can finish the lecture 😭😂
I'm the same with audio books
Audio books Co.e with timers and u can save YT vids
Set a timer on your phone where the ‘When Timer Ends’ setting is “Stop Playing”. Then you always know it’s within 30 minutes or whatever your timer is.
You can probably do this with a device that can tell when you fall asleep. Doesn't apple watch do that?
I usually try to screenshot when i feel the sleepy coming. 😂
When first started watching this, I was tempted to stop because I felt it was going to be above my head. Ironically, this man took a magnificent approach of explaining these laws of physics, in a way that I actually understand everything.
What are the laws of physics, exactly? Who wrote these so-called "laws?" Evolutionist athiests "believe" in this and often rely on the "Laws of Nature." But if you ask them, "What is "Nature?" they give the dumb buck look. It's a magical wall they cannot penetrate. Science is a circular reasoning mental exercise of futility designed to break your mind.
I think Sean is keeping something back. He has obviously travelled through time. Here in 2023 he looks at least 10 years younger than he did last week.
About 13 years younger to be exact…
😂
When you read this I'm in the past you are in the future .
@@bltn7469 🤣
and 30 years older than he will look next week, when he gets back to two years ago.
Thanks for uploading this talk so we can all (re)watch it.
Don't be a dick
Proof that he will present anywhere. Kudos.
It appears to me, that trying to travel backwards in time, is like trying to travel out of a black hole.
35:58 If I understand the geometry of black holes correctly, not even faster than light travel would help you escape from beyond the event horizon. Because all possible geodesics inside the event horizon point directly to the singularity, no matter what speed youre moving, even greater than light, all motion in any direction will only bring you closer to the singularity. Its not like a whirlpool in water, where you can imagine swimming against it to move into a direction thats not the center, and the speed of the flowing water is what determines whether you can get out or not. That analogy does actually apply but only outside the event horizon, in the ergosphere where frame-dragging exists as we know it. But instead of water flowing its spacetime itself thats flowing. Inside the event horizon there is no light cone anymore, space and time lose meaning or they get twisted into a horrible mess. Or the light cone becomes a light beam of infinitesimal size, pointing directly into the singularity. However way you think about it
you dum
nope. think of yourself in a space ship that looks like any ship of days past with a mast and a figurehead, a sail and an anchor, as well as a deck and a crew. you're sailing on the outer boundary of the ergosphere, if you can define such a place. you have an anchor with a chain of near infinite strength, with a spot light shining directly up the chain. while that chain is in the ergosphere, you still expect the light to hit the bottom of your boat, regardless of the direction the ergosphere moves, because that chain will curve to match the movement at a certain point, the anchor and spotlight hit the event horizon and the light is no longer traveling fast enough to overcome the gravity from the singularity, just like if you were to spray a squirtgun at the moon, it's just going to fall back down. that doesn't mean the path to the moon doesn't exist, only that the propellant needed for your water is not sufficient. think about the chain, it hasn't broken, it just experiences spaghettification. a geometry that follows the chain would lead out the event horizon. the concept of the ergosphere is the embodiment of that geometry. as the black hole spins, the centrifugal force is an additional boost to the momentum of light, allowing it to break away from the singularity at a point where it would not have broken free otherwise. so while your ship may be able to pull the anchor out and see the spotlight again, the thing would have sent your ship spinning like a whip as it acted like a sail in the gravity and to pull it out, you would turn into a black hole. but a theoretical geometry does exist, it just doesn't come easy.
@@Mitchell_is_smart._You2bs_dumb I'm not reading all that shit, you dont even use physics you just use dumb analogies and there are no par breaks
There is no faster than light travel. The speed of light is the limit.
@@jhkuno88 Cherenkov radiation, tachyons
Very interesting. Great lecture!
The Spielberg movie he was talking about was Interstellar. It was going to be Spielberg before Nolan took over. Very cool.
We should start up a list of things we have a name for, but which don't actually exist, you know, like psychokenesis, levitation, ghosts, time travel, big foot, the loch ness monstucker, spider man, the list goes on.
Common sense
Spider-Man totally exists, good sir! Why, he saved me from falling out of a window yesterday. How dare you insinuate such a thing!
this spider verse had me wondering if there is a spider out there in the Simpsons universe that was bitten by Radioactive Man and if he teams up with spiderpig?
So refreshing to read something logical on this thread...!!
My will to survive?
I love the confidence here not to admit that there may be things he doesn't know. It's like some tribal leader 5000 years ago saying we will never get to the moon because boats only move on water. 😅
One thing I find interesting, is that if you could travel back in time and would find yourself there, what would the both of you be made of? If you could duplicate matter like that, you could basically create infinite amounts of it, which would mean that there would be a huge exploit in our universe. Either, matter/ energy is constantly flowing through our universe and no particle is actually the same from one moment to the next, or then something would happen to either one of the versions to make it disappear, because you couldn't have the same matter in two places at once. Also, the only way I can even begin to imagine time travel to the past is by removing oneself from the confines of whatever here is, and going outside space time, and placing themselves back into space time in a different location. Here again, you would be creating matter out of nothing, thus duplicating yourself, thus possibly creating a paradox of who is the real slim shady and actually owns the atoms one is made of.
You are never the same matter from day to day because every molecule that we're made of gets replaced from day to day. Particle isn't at two places at once, it's either in the future or in the past.
@@AthenaShelly I don't think you understand what is being said here. You are made of matter, regardless of where it is now. You are not taking into consideration whether a person travels back in time for example only one second. Are the molecules the same as they were a second ago? If so, there are now two of you made from the same molecules, and you both exist for a second, until the other you disappears. Hence, you have two sets of you, made from the exact same molecules. Heart muscles for example don't get replaced in years. The water in your body right now might be somewhere else in a few days. Still, the water in your body has to change into water that exists in the universe. if it doesn't come from outside of the universe, it has to have existed in this universe since the beginning. It doesn't come from nowhere. Thus, if you take yourself into the past, have you brought back molecules that already exist somewhere in the past universe, or are molecules made out of particles that aren't actually the same, meaning, that is what we see actually an effect of something happening to our universe, or is everything the real concrete thing in this universe, not touched by any other effects?
My double will have to fight me for those atoms
@@Lawhnothing is being “created” in this situation. they aren’t new particles, they’re the same particles from the future. just because a particle’s future is contemporaneous with its present does not mean that it has been duplicated, or that the second particle is different, or that it’s stolen from some other universe. if this is to make sense, you should be able to draw a world line from past to future to past again. in doing so you will see that nothing is ever duplicated, the particle’s personal history simply folds over itself.
Simply? Using this word makes me doubt your understanding of your lack of understanding, or maybe you are a genius, I can't know since I'm not one. If I travel back in time one second, there will be two of me for one second. I would have aged one second more than otherwise. The two of me consist of what we would consider to be the same matter, separated by time and space as well. Has the matter somehow reversed it's linear directional travel through time, or has it been taken from time and space and placed back as a separate entity entirely, as you say folded. What does this reflection consist of? There is now for a moment more matter in the universe than there was before, and how will this affect the surroundings? Will there be a balance of matter outside of time, where if you take some matter from the future and put it in the past, that there is no resulting issue in that? This doesn't make sense but it's funny enough to say out loud. If I have to pay for a car and I have half of the money and a time machine, what theory would support the idea that I would go to the car dealership, wait for my time travelling self to come back with my money, hand the cashier two half stacks of money, and then I would take the car and leave. Of course in I guess my logic there is a problem here, since I would eventually have to get the money into the time machine, so the cashier would not be able to hold on to it without destroying the universe or something. But the point of this thought experiment is to go deeper into the balance of things. The doubling and removal of matter. @@tonoornottono
Here’s one reason, in physics. one could not visit their past self: Conservation of mass- In physics and chemistry, the law of conservation of mass or principle of mass conservation states that for any system closed to all transfers of matter and energy, the mass of the system must remain constant over time, as the system's mass cannot change, so the quantity can neither be added nor be removed.
law is a strong word. its more like a suggestion really
Two pair of doxes walk into a bar. Bartender says get out.
I can't get enough of Professor Carrolls lectures. He speaks so well and is a fantastic teacher. Love his use of real world associations. Some serious & some humorous.
Paradoxes would be the least of your worries. Your biggest worry should be how do you survive in deep space and how do you get back to Earth after your time jump. The Earth is moving...very rapidly...all the time. And BTW, you would also still have the angular momentum and velocity that the Earth, the solar system and the galaxy had when you jumped.
Gravity as a fictitious force. Main article: General relativity The notion of "fictitious force" arises in Einstein's general theory of relativity. The way all masses in free fall descend at the same rate led Albert Einstein to wonder whether gravity could be modeled as a fictitious force. When F = ma, the size of the force can be measured by the size of the mass and how much the mass is being accelerated at. But all masses in free fall accelerate at the same rate of acceleration, that would mean if gravity is a force then that force changes for each object. He noted that a free falling observer along with various items in a closed box would not be able to detect any force at all, for they would all have no weight. W = mg then W zero = mg zero. In other experiments using a scale various items have various weights. Therefore now when using a scale F = ma is true, where equal acceleration truly produces different real weight forces from different masses, and F can now be measured; hence, weightless free falling reference frames are equivalent to force free inertial reference frames (the equivalence principle). Developing this insight, Einstein formulated a theory with gravity as a fictitious force, and attributed the apparent acceleration of free fall due to observers watching from a non-inertial reference frame while they are being accelerated by a force, and to the curvature of spacetime, which is a force free inertial reference frame. This idea underlies Einstein's theory of general relativity. NIST WTC FAQ 31. How could the WTC towers collapse in speeds that approximate that of a ball dropped from similar height in a vacuum (with no air resistance)? NIST --> "Since the stories below the level of collapse initiation provided little resistance the building section above came down essentially in free fall."
@@davidmudry5622 Gravity is not a force, gravity is the effect that a mass has on space itself.
@@MichaelClark-uw7ex I said gravity does not pull but the official 9/11 explanation said the pull of gravity got stronger and stronger as each floor became part of the downward force.
@@davidmudry5622 That was a mistake, momentum increased as each floor pancaked, gravity is constant. I'm pretty sure physicists know a lot more about gravity than the 9/11 commission
Time only flows one way, like a river. If you want the river to flow in a different direction you need to change the shape of everything surrounding the river
Ok! Let's do it!!
Liquid is quite flexible. Perhaps time is as well. There is a lot we do not know. Which is fine because it would be pretty dull with nothing left to learn.
Thanks, Michio Kaku.
Or go fast
Our preception of time flows only one way. Actual time doesn't exist
Knowledgeable and understandable
The main problem understanding time travel is that we don't really understand what any kind of travel is, at a fundamental level. We know how to travel through space, if we want to, I can get up and walk over there, but we don't really know what that means at a fundamental level. So, the reason we don't know the answer is that we don't really understand the question sufficiently well. For instance, there are two quite different notions of "going back in time". According to one of them, I, as I am now, could somehow be transported back into the Middle Ages and find myself living in that time, complete with my memories of the future. According to the other notion, you could somehow "wind time back", so it is the Middle Ages again, but you won't be present there. You won't exist until you are born much later. The difference between these two notions corresponds to two very different ways of understanding time. One is that time is something that you travel through, albeit with no choice. The other is that somehow you are in time, but it passes. It makes all the moves, so to speak, you don't move within it.
Amazing talk
22:44 at what moment does the traveling clock start to differ from the stationary clock?
the moment one clock travels a different distance
In the depths of paradox, where timelines entwine, The mysteries of time travel, a complex design. A journey through epochs, past and future's embrace, Yet the paradoxes of time, we must carefully trace. The past is a realm where we yearn to explore, To rewrite the chapters, to even the score. But change the past's thread, a paradox unfurls, Affecting the future, in unpredictable whirls. The butterfly's wing, a small act in the past, Can lead to a tempest, a change unsurpassed. The ripple effect, in time's endless sea, A paradox that challenges what's meant to be. And what of the future, that enigma so grand, Can we alter its course, with a time traveler's hand? A paradox arises, a loop to contend, For how can we change what's yet to ascend? The grandfather's paradox, a conundrum profound, If you travel to kill, does logic astound? If you end your own lineage, your existence denied, A paradox that leaves the mind mystified. The twins of relativity, time's constant refrain, One travels through space, the other remains. A paradox unfolds, as time slows and bends, In the depths of the cosmos, where reality rends. In the heart of these paradoxes, we find the key, To the essence of time, its enigma and decree. For as we journey through its intricate weave, The paradoxes of time, they ask us to believe. In the dance of past, present, and future's embrace, The paradoxes of time travel, a celestial chase. A reminder that time, in its essence and prime, Is a riddle we unravel, through the corridors of time.
This is just more fantastical bs hiding behind poetry. Easy to spot. Eminem would crush you. Why are you posting about time travel on a truther site?
This is incredible!
Since gravity can change the direction of space-time, what can the three other forces do? Can we have an effect on space-time by applying the weak or strong or electric-magnetic forces? What if all four were utilized simultaneously but at different angles and intensities? Could we precisely steer space-time?
I travel back in time when I'm laying in bed trying to fall asleep.
Because there is no actual time, if we ever were to travel though what we perceive as time, it would actually be traveling to previous conditions. Both the "Past" and "Future" are information so if you did manage to seemingly travel to the past what you would be doing is accessing the information set of our physical reality in a particular position in the universal information set. Like skipping to chapters on a DVD to your favorite scene. As for not being able to travel faster than the speed of light, there are short cuts that allow you to get from point A to point B faster anyway, if not instantly, and that is utilizing columnar standing waves aka "Wormholes". These waves are like a tesla tunnel that can get you from earth to a distant star system 444.2 light years away without the bother of having to travel from here to there. The amazing thing about standing columnar waves is they can reach through incredible distances without distortion or interference from the physical world in between the two ends. It has been said that mathematics and geometry were not invented, they were discovered. This is a clue to how apparent time travel would be possible and how you would go about doing it and once our quantum AI computers reach singularity we can just sit down and ask it how to do it. In the meantime why not just put to bed all of your preconceived notions about the great pyramids and reexamine them with all of the above in mind.
Write it in your manifesto, jackass.
At the start of "Principia Mathematica" Newton says "For the purpose of this demonstration I must assume that space and time are fixed and immutable" so it must have occurred to him that they might not be.
Time is the Movement of an object within a given Space .
So we are moving thu space and time. Since every thing in the known cosmos is moving thu time and space. And always has. What would happen to an object or person if we stop them moving relative to the universe. Would it stop moving in time?
Good question. I can't think of a way to stop moving though. It might be impossible.
@@whichgodofthousandsmeansno5306 Absolutely it's impossible. we'd need to factor The size location and trajectory of every atom in the cosmos just for a reference point to start with. and that's not to mention that we don't know if the same sheet of time travels through multiple dimensions. and if we can stop relative to this dimension. that maybe its not gonna stop relative to another dimension. And in effect void any attempt to measure it.
At the cost of potential over simplification, do you mean: Traveling through more space mean experiencing less time while experiencing more time mean traveling through less space? The aether is real, it just lacks the properties first conceived. The higgs field is the aether. Traveling through the aether you experience less time, though you may not know it. Remaining motionless relative to the aether you experience more time. This is the way I've thought about it for 20+ years, but I still don't know if it's correct.
When I traveled back in time, I made a successful campaign for exposing time travel as just pure fantasy, so nobody much believes in it any more, just a few who continue to prefer fantasy over reality.
What do you mean? Time travel is entirely possible. Many scientists concur with this. Not with the tech we have now mind you, but that could change. Just because you don't like it, doesn't make it fantasy.
@@mywifesboyfriend5558 yeah, scientists believe a lot of things are possible, (in theory) such as time dilation, when matter is caused to speed up to close to the speed of light. Einstein believed you could use the measurement of the speed of light multiplied times itself to calculate the amount of energy that is bound up in mass. But writing something on paper doesnt mean it's real. Time travel certainly isnt. Ghosts arent. Levitation isnt, unless you consider the short distance one magnet can repel another magnet. But maybe mind reading is real. Right now I can read your mind, and i can tell you believe ALL of those impossible phenomena.
All else aside, if a particle (or person) could travel back in time to meet its past self you then have 2 particles - did you just create more mass than you started with (repeat, rinse to get many particles from your time machine)? How can the universe now have (slightly) more mass than was originally in the sum of the mass in the universe?
where you think dark matter comes from? 🤔
Your reply is interesting in that it is very book worm ish. Ask yourself this - what force or intelligence is it that tells a photon to change from a particle to a wave and back again? Of course, the answer is easy. Photons don't exist. No paradox. Just like electron probability clouds. Total nonsense. Physics is fake.
Excellent content
Awesome video!
How much energy was captured per cubic centimeter?
That was great!❤
I love this man. He is so knowledgeable and speaks clearly.and honestly.
He makes physics entertaining.
Glad he doesn't mumble and lie .....
Okay, I’m only ten min in and already fascinated by this lecture, so maybe he gets to the later, but how would we ever really know if we didn’t or couldn’t effect the timeline??
information about the past is still out there and if we manage to curve space time to travel faster than light we can travel in the past but we will only be there as observer
the light cone demonstration basically destroys the entire dream of time travel. still an awesome video
The light cone is a false demonstration. The light from the light source would radiate equally in all directions, therefore it would be impossible to go outside it!
Well, I guess my perception of time is just as unreliable as my ability to draw a straight line. But it's fascinating to think about how our understanding of time has evolved over the centuries, from Newton's absolute time to Einstein's theory of relativity. It really shows that even our most fundamental concepts can be challenged and refined as we learn more about the univers
Gravity as a fictitious force. Main article: General relativity The notion of "fictitious force" arises in Einstein's general theory of relativity. The way all masses in free fall descend at the same rate led Albert Einstein to wonder whether gravity could be modeled as a fictitious force. When F = ma, the size of the force can be measured by the size of the mass and how much the mass is being accelerated at. But all masses in free fall accelerate at the same rate of acceleration, that would mean if gravity is a force then that force changes for each object. He noted that a free falling observer along with various items in a closed box would not be able to detect any force at all, for they would all have no weight. W = mg then W zero = mg zero. In other experiments using a scale various items have various weights. Therefore now when using a scale F = ma is true, where equal acceleration truly produces different real weight forces from different masses, and F can now be measured; hence, weightless free falling reference frames are equivalent to force free inertial reference frames (the equivalence principle). Developing this insight, Einstein formulated a theory with gravity as a fictitious force, and attributed the apparent acceleration of free fall due to observers watching from a non-inertial reference frame while they are being accelerated by a force, and to the curvature of spacetime, which is a force free inertial reference frame. This idea underlies Einstein's theory of general relativity. NIST WTC FAQ 31. How could the WTC towers collapse in speeds that approximate that of a ball dropped from similar height in a vacuum (with no air resistance)? NIST --> "Since the stories below the level of collapse initiation provided little resistance the building section above came down essentially in free fall."
@@davidmudry5622 Your principal premise is wrong. Mass matters. In space, two 10 gram weights will attract each other with a force 4 times as strong as two 5 gram weights, provided that all external influenceces are excluded.
@@davidhess6593 Newton said all objects in free fall have the same acceleration because a big mass might be heavier but it's also harder to push. Einstein laughed his head off, LOL, and said there is no weight in free fall, what an idiot Newton is. Any comments ?
@@davidhess6593 Q. 3 different sizes of drones are hovering inside a bus at the same distance from the back of the bus, and suddenly the bus accelerates. F = ma, what forces are on the drones during this acceleration?
@@davidmudry5622 Virtually none until the drones hit a passenger, a seat or the bus windshield.
Around 46:00 ... I'm guessing he's hinting to the movie Interstellar?
Are theories that do not exclude true timetravel (relativistic timetravel or "timetravel" is alright) just incomplete?
I would think everything to do with theoretical physics is incomplete. My take is that multiverse theory solves all paradox. However, I see no way to verify it.
thnx, nice talk. So you can proove that the future is really uncertain because every future event in my light-cone depends on a lot of other light-cones some of these are outside my horizon. My past is my past light-cones. A big question may be welther my future events are not certain. These have to be created. The 3+1 dimensions fabric is not static and has be created.
What if I went back in time and killed myself as a baby? If I did go back in time and killed my grandfather wouldn't that cause the time line to split causing an alternet time-line where I was never born but the time line I came from would continue on as if I never traveled back? Or would this time line be destroyed because there might be able to only have one time line.. No alts for some reson?
Time travel forward= to go about things through out your day in the most efficient and correct way possible puts you ahead of any other that has to rework something because they had to redo something.Time travel back=failure lack of completion of a process ,unforseen ,refuse help,forgiveness,distruction
If it is the expansion of the universe that creates the arrow of Time, would you not have to shrink the universe to go back in time?
I've always wondered if Time Dilation accounts for the Fermi paradox. Beings in another galaxy travelling slower than we are, or with less gravity, would not have experienced as much time as we have, and wouldn't be as technologically advanced. So they wouldn't have mastered interstellar/intergalactic communication or travel.
I thought that at near light speed the time between observing the ship leaving from Earth and seeing it in front of you on Alpha Centauri could be arbitrarily short. With light taking zero time between observation and arrival. So it is true that the Earthling could reach Alpha Centauri in time for the Friday party if a near light speed autocraft is employed. I guess it depends on which "now" you accept when referring to things which happen on Alpha Centauri. It just seems impolite to refer to things on other planets happening "now" when we know that our observations are very old. * I think I am wrong. Anyone know where? I'm wondering why it is not sensible to call "now" on Alpha Centauri, the time at which light arrives when it leaves right now. Since all other now's are inaccessible. But if I send a message to Mars, I wouldn't say it arrived "right now" until 3 minutes after I sent it. So the "now" of anything is at least double what we can observe on their clocks from here. We see their clocks light distance behind and the soonest we can have any sense of being in the "now" on Alpha would be another light span of time. It makes no sense to call "now" on Alpha anything less, because we will never experience a "now" on Alpha any time sooner.
Knowing what happened in the past is useful in realizing that whatever you can help prevent you from doing it again. Like pulling wings off flies. In the present you choose not to do that anymore. It won’t change the fact you did it once, but knowing you did allows you to choose not to do it again. As a kid I was stupid and did reckless things. knowing that, I matured and have no need to do them again. As an adult I now do NEW stupid things. Which hopefully I will not do again - in the future 😊
Sometimes learning the hard way is the best way... as long as no one was killed or seriously injured in the process.
Don't feel bad, no matter how stupid the things that you do now, it's not as dumb as trying to create black holes...I'm just saying.
Way I look at it, we kearn the hard way so we can teach the younger generation not to make those same mistakes, or have to learn the way we did. That's one way to progress in this life. Just a thought.
I like to play with the idea that traveling back in time would not affect a collectively-perceived chain of events. I enjoy the idea that it instead would be more akin to a copy of you going backwards (or two copies of the same person swapping places) and taking the place of the you at that time, and in doing so the copy of you that traveled back would reverse its information to be of the exact same of the you at that point in the past. Although with this idea, the same chain of events would occur. It's a neat thought experiment.
Perhaps the current state of the environment is just the most likely outcome of every possible interaction of "time travel."
Backwards is not likely. First: how could you ever slow time beyond completely stopped? And I don't see any way of even slowing time slower than the constant pace everything moves at. Even if something is moving along the timeline slower than you, how could you reduce your speed not only to match it but actually travel slower? Now I'm talking "light speed" if indeed it could be done, however we do know that, the faster a object of mass moves the more massive it becomes... these are real serious and as of now and probably forever will remain impassable obstacles, if we choose speed and momentum as our field of experimentation. But what about electromagnetic energy?
I wonder. If one guy stands on earth with a flashlight and jumps. The light from his flashlight is moving from the audience at the 'speed of light' plus 'jump'. A second guy stands on his shoulders and jumps. Light from his flashlight is moving away from us at the speed of light plus jump plus jump. We would perceive the light as moving away from us faster than light? I mean they are at the same starting point.
Time is a perception of photons. If you instantly move far enough from the earth, you will be in a position to perceive the light reflected from the earth at that earlier point in your referential time line. From there, you have to work out how to "rewind" the photon path allowing you a means of following that referential photon wave/emission back to the event.
I travelled 8 hours ahead in time when my alarm clock went off
I thought I was an idiot, but some of these questions. Damn. Also this man is a saint. Totally patient and great at explaining things.
If time is a reference frame in space then what you would need to prove is that the past and future are a perimeter in space. Faster than light travel should be like a Pull in fabric. I think entropy should be mapped on a hypersphere
If you go back in time, it’s completely possible to change everything about your original timeline if going back in time means going into a parallel universe that doesn’t interfere with the original
@notfiveo time travel decisions are only relative to the person traveling except in the universe’s that are affected due to unlimited possible universes…does that make sense?
@Dracarys yeah except, when you bring about the changes to the parallel universe by changing the past, the one thing that changes in the original universe that does affect others is that you are no longer present in the original universe, right?
@@raheelsarvana I suppose that would be the case though it wouldn’t change the original timeline for you to be gone and would only have an effect on the future that hasn’t happened yet.
Yeah that's what the videos saying dummy
No it doesn't, get your head out of your ass, there is no time travel. @@MadBull.34
Speed of lite or speed of perception?
If time is what prevents everything from happening at the same "time", then it is the limit of the speed of light that gives time that property. If light had no upper speed limit, causality could not exist nor could our universe exist. So, space is required for "room" in which "things" can exist, but without time, space is essentially useless, hence we must have "spacetime" in order to have a universe in which separate events can occur. This may appear to be obvious, but I have always somehow believed that time is the key "ingredient" which makes our universe possible.
I always thought that if i went back in rime and presented some events it would create an alternative timeline of events
It's one thing to achieve time jumps or connections through time and another talk about the paradoxes of time I'd like to know that the person speaking has some experience rather than just theoretical steering out of a window of what real people are doing in the real world
Very good
Excellent lecture, thanks! A small inaccuracy about GPS though (33:26)....the receiver does not beam anything, it only passively receives signals....nor does it have any (accurate enough) clock to compare against....the received signals have encoded the time they were beamed and the position they were beamed from....given multiple available signals, the receiver's chip performs triangulation calculations to compute its own position.
The GPS receiver has a stable quartz clock. It constantly sets its time by using at least 4 satellites. By using at least 4, the overlapping signal spheres means it can pinpoint itself and calculate and correct for its own clock inaccuracy (because it can trust the satellite clocks) Therefore, all gps receivers are as accurate as an atomic clock. Otherwise, they would be very inaccurate
I think it's fascinating that we have to adjust the time on GPS satellites (in order to compensate for the relativistic effects of time dilation and frame-dragging), not because time is flowing any differently on-board the satellites, but because it _appears_ to be flowing differently from our perspective here on Earth. Relativity is weird!
@@simesaid We have grown up thinking time is unwavering- maybe in our experience we think it is, although 'time flies' is a great hint. Once you realise that the speed of light is fairly constant - and that different observers experience time _relatively_ which makes this true - it makes far more sense.
@@simesaid According to the experiment on an airplane flying around the earth time is really flowing different at a higher speed and different gravity. If it is time that is flowing different or the clock that is behiving different at speed is a question though in my oppinion. There is often two sides to a coin.
It is fascinating but with GPS we are talking micro seconds. When you get into the time dilation effects from near light speed travel that is when things get really interesting. Einstein's thought experiments were able to simplify mind boggling concepts. Then, he could math it.
Listen, people. You can find the evidence that time travel to the past is possible and The Block Universe theory is a real too. Our present time is not the "first" but seems like a movie or song with a replay on. Because of Kim Wilde, The Terminator, Back to the Future, Poland. They are connected by an extraordinary but the tragic story that happened in the late 1970's between Kim Wilde and the certain polish-american soldier who came from the 21st century. He probably died on 26th October 1979 but she never found out. Her music career - especially the song "Cambodia" - or movies like Terminator & BTTF (M. Biehn and Michael J. Fox were choise because of him) are the consequence of this story that has been encoded in these famous movies, a date of October 26 for example (release date of T1 or BTTF's title itself). The common elements between T-1 and BTTF-1 are the coded description of this man's life in the really closed timelike curve and the entire BTTF trilogy also "predicted" his whole life, including the meeting with Kim Wilde on the final scene in BTTF 3: Wild(e) West and 7th September (his future date of birth) = Space & Time. Spacetime. That's all for now.
Surely everything you could possibly do, including e.g. breathing, would therefore not be possible, as even the most simple thing would have some effect on everything that happens after it.
Go in the reverse and it’s the same.
I've been traveling in time for the last 60 years, I haven't run into those paradoxes. Or even one!
The Gita makes the case of Time travel perfectly clear, not only is it do able, it’s quite normal! What exists has never not existed. Make of that what you will!
I'm inspired by this to write a short time-travel novel. Here it is: Larry built a time machine. He got in it and went back to 1600. He walked around in "Merry Old England" for a few days, surreptitiously taking photos and audio recordings, and then he popped out of existence. Why? Because he transmitted a whole stew of infectious diseases to the Merry Old English of 1600, to which nobody in the world had the least immunity, the diseases proceeded to spread throughout the world and nearly all humanity died, including of course Larry's great-great-greats.... The End
The most significant problem is that our universe, galaxy, solar system and planet are all in constant movement. We are always traveling at very high speeds and never return to the same position. If we moved in time where would reaper. We would require a type of anchor on Earth to be our relevant location. Speed is always relative. And our location is relative. How could we build a relative location on Earth. And be careful about the location. The same location may have once be underground. While in the future your location may be in the concrete wall of a future building. Either location could be distrusting when you reappear. These problems are rarely covered in movies.
I think the closet that some of us will get to Time Travel will be a computer generated version of reality, maybe a Virtual Reality machine of sorts like a holodeck or something, where points in time, although possibly arbitrary, could be generated for people to see. The way computer tech is advancing, this is not beyond possible in te next 50 years.
and maybe they'll be able to create a perfect simulation of our time that people will get plugged into. and maybe people inside this simulation forget that they're in one. and they create simulations of their own. which eventually create simulations of their own...and so on ;]
Don't hold your breath. People have been working on Fusion power for well over 70 years and its still just a dream.
How do we know the black holes created are not portals into other dimensions- through time??
I do have a legitimate question though; I thought that all that is, all that was, and all that will be exists within a state akin to omnipresence? Meanwhile, something with a consciousness is "railed in" to percieve at a limited rate, in its limited space, while the rate at which that being percieves time is dependent on its speed through that-which-has-already-taken-place? I am sorry that I can not write this to be more clear.
Your audio engineer needs to invest in a parametric equalizer and notch out that feedback.
This is 13 years ago in a school library in Missouri…. I’m sure “parametric equalizers” weren’t top priority
@@JohnnyNiteTrain Tell the kid to use a notch filter lol.
We are and have always been travelling through time since time began
That's like saying going to the toilet is traveling. I mean sure, but what an uninteresting way to look at it.
12:20 I take issue with you stating the idea that quantum mechanics "implies multiple worlds", since that is just one interpretation of quantum mechanics.
I thpught the title was "The President of Time Travel" I was ready for a speech from our leader.
Scientists at Cambridge University have taken advantage of the unusual properties of the quantum realm to successfully simulate a method of backward time travel that allowed them to change an event after the fact one out of four times. You may want to consider taking that experiment into account
This is a creative writing lecture by a physics professor
Yep.
Exactly, just like an episode of Star Trek.
It seems to me that "time" is the one word in human language that cannot be properly defined. Trying to define time always seems to result in circular reasoning or in using its own units or its characteristics such as past, present or future when attempting to define time. I have always believed that time can only be experienced but never truly defined.
34:35 hold up, I thought it was the immense speed that they were moving that affected the time dilation not the difference in gravity which would be negligible
Sean Carroll has one of the most soothing voices ever. I genuinely love the topics, but it's so easy to just doze off while listening to him for an hour 😅
Time can slow down and even stop; but it can’t go backwards. Because time is delineated by the position of all particles relative to all other particles; the particles can never be in the same positions again.
And four years after this lecture, Nolan and Kip came out with Interstellar.
Interstellar is a science fiction movie.....the operative word being fiction.
Time is the measurement of the interaction of Matter to a change and changes of all things simutaneously a new beginning of everything as it changes with Us Constantly without pause,✨
Dr. Carroll says that we're especially fascinated with going backwards in time. Well that's not true in my case. I would very much prefer to see the future rather than the past. After all, I already have some idea of what the past was like (generally not very pleasant), but the future would be totally unknown.
It's all ready happened.and a mind boginnigly large #of almost identicle parallel realities that have differant consistent histories is where we seem to be.😮
@@rudedawg2495 You're referring to alternate time-lines a.k.a. the "many worlds" interpretation of quantum mechanics. That's not quite what I mean. I'm talking about traveling forward in our current time-line. Although traveling to THE future may not be possible because of quantum indeterminance. Perhaps we'll only be able to visit a sheaf of the most probable futures.
I alway come away from Sean’s lectures slightly more educated and a lot more confused. My brain is just a bit like a slow clock.
Join the club. These are some mind boggling concepts. But from watching vids like this I have come to the conclusion that multiverse theory solves all paradox. I would otherwise not even know what that meant.
Multiverse theory is an explanation that makes sense. However, there are others. Personally, I think that he's succinct in his oration, but poignancy is really what he brings to the table. The explanation of light cones was fairly inaccurate, but that's understandable, as it is a two dimensional description of a four dimensional phenomenon.
@@legiongrattan7349 Which is really just the limitations of a projector screen being your means of visual aid. If he had some kind of hologram projector he could do a 3D representation, but even then to add time into it as the 4th dimension isn't really possible with visuals.
One thing that breaks my brain is that if a person travels around earth the opposite as the sun at a fast enough clip they would hypothetically be going back in time. So if a person could do a backwards rotation traveling around the earth they would be traveling through all the time zones in reverse essentially setting the calendar dates in reverse. That would be time travel. But the earth would not be traveling back in its travel of its rotation around a star. So the earth would still be traveling forward as you are traveling back through dates on the calendar. I think this might become an alternative reality not time travel
'What do we want?' 'TIME TRAVEL!' 'When do we want it?' 'YESTERDAY!'
I time traveled to the end of this video when I woke up.
Who said --> "I'm working on a new theory of time." ?? Answer :: Lee Smolin.
Multiverse solves all paradox. Problem is I imagine there is no way to verify it. Unless we get some kind of quantum leap device.
Multiverse theory is a Heaven myth for atheists
Filmed 2010, posted 2 months ago, pc used for rendering video made in1946...
If I stay on earth and a second person travels fast and returns. They having less time pass means when they return I experience their past. As I will see them when they are younger than when they left. So I will be in touch with the past.