What Is Time? | Answers With Joe

this video is supported by brilliant org there are really only three things about time that we don't understand the past the present in the future because the past once existed and now does not exist the future doesn't exist in the present well you can never really catch up to it like right now you're watching this video and in the future of this video I'm going to do something that you've never seen me doing a video before and that tea that I just did is now in the past and the present is right this very moment and ironically by the time you've even processed that moment it's already in the past the passage of time is perhaps the biggest guiding force in our lives we celebrate it we mourn it we schedule our lives around it the very passage of time is the thing that makes our existence possible and it is also the very thing that will eventually take away our existence so it's no surprise given its importance that a lot of brains have worked on what time is over the years and we've got a lot of different interpretations of it and still what exactly it is and how it works remains a mystery the Christian monks st. Augustine was once asked what is time and his response was if no one asks me I know what it is if I try to explain it to him who asks I don't know pretty accurate and it's one of those things that you think the more we study it the more it would make sense but no it just becomes more and more hard to understand insert Doctor Who timey wimey reference here and our study of time goes back long before we even have records the ancient Egyptians used obelisks as Sun dials to tell what time it was during the day they also have water clocks that float at a steady rate to keep time and obviously our glasses it was the Babylonians that first divided the day into hours made up of 60 minutes each which were divided up by 60 seconds each and they did this all the way back in 1800 BCE it was a great Dutch astronomer and physicist Christiaan Huygens who first invented the pendulum clock in 1656 this was actually the most accurate way of keeping time for the next 300 years 1927 saw the invention of the first quartz crystal clock this uses the piezoelectric properties of quartz that vibrates at 32,768 hertz giving it an accuracy of six parts per million but the most accurate measure of time we've been able to conceive so far is the atomic clock which uses the natural resonance of the cesium atom this makes the current definition of a second the time it takes a cesium 133 atom to vibrate 9,192,631,770 times ain't no way I was gonna memorize that number and this is important not just as a measure of time the cesium standard also helps to find other SI measurements like the meter which is the link that takes for light to travel in one 299,792,458 of a second i should have that memorized by now of course we don't need a clock to feel the passage of time we actually have our own little internal clocks and one of them you might consider would just be the heartbeat which beats at an average of around 70 beats per minute and then there's our circadian rhythms which comes from the hypothalamus this kind of secretes hormones at different times a day giving us wake and sleep cycles but our perception of time is subjective as we all know time can feel like it's speeding up or slowing down depending on the situation it tends to slow down quite a bit when we're in danger in some excitement so it was believed by many philosophers over the years that time is completely subjective and that there is no objective absolute time this is one of those things that was vigorously argued by guys with long beards standing around marble columns and stuff but as a scientific revolution began to take hold this argument sort of fell away and became replaced by an argument between what you might call relational lists and absolutists absolutists believed in absolute time they believed that time is an independent constant of the universe that functions independently of our perception of it or by the interaction with matter Sir Isaac Newton was one of these absolutists the relational lists saw time only as a measure of change basically arguing that the only reason time exists is because of changing states of matter so theoretically if you had a walled-off room where nothing happened inside of it for millions of years technically time did not pass in that room which is kind of weird but it's actually not that far off from the definition of time as a measure of entropy Newton's second law of thermodynamics states that in a closed system entropy will always increase over time entropy being the state of constantly moving toward equilibrium so if you have a hot coffee sitting on your desk the heat from that coffee will dissipate into the surrounding environment until its temperature reaches equilibrium with everything around it it doesn't go the other way another example might be a wineglass it is in a state that is definitely not in equilibrium with the rest the world wine glasses aren't naturally formed after all but if you shatter the glass on the ground all those little pieces are much closer to what you might find in nature stomp on them and they get smaller and smaller maybe you smash it on a road where cars drive over it over and over again every day it will get even finer and finer - down into dust which isn't even more even texture and if you want to keep going with it someday when the Sun expands it'll vaporize this and it'll just become gas dissipated out into the universe you get the idea but the arrow of time only travels in that direction that wineglass is not going to just reassemble itself by the way another interesting way of looking at entropy is through the statistical mechanics model that was championed by Ludwig Boltzmann he made the point that if you had two boxes with twenty balls labeled one through twenty there's only one way for all the balls to be in one box and not in the other whereas if you had a nineteen to one distribution there are twenty ways that that could happen because there are twenty different balls that could possibly be the one ball in the other box extrapolate that up to a 15-5 distribution and there are 15,000 different ways that could be arranged so a 15-5 distribution is fifteen thousand times more likely than a twenty and zero distribution in a ten and ten distribution there are more than 180,000 different arrangements that could make that happen so statistically if he randomly distributed the balls there was a much higher probability of a 10 - 10 or an 11 and 9 distribution than a 20 and 0 or a 19 and one distribution now if you apply this to atoms and energy the same rules apply atoms in the air gonna randomly collide and interact with each other and they're gonna sort of spread themselves out and distribute themselves evenly throughout your house so that one room isn't gonna have a higher pressure than another room now where this really gets interesting is that Boltzmann predicted low in tropic fluctuations so what does he mean by that so if we go back to those boxes with the twenty balls in it the probability of getting twenty and zero are incredibly low as we talked about before but if you run that over and over and over again randomly distributing them each time eventually after millions and millions of times a 20 and zero combination is going to happen that's just how randomness and probability work and that is a low entropy fluctuation so take that and expand it out to the Anur of our universe and you can expect that at some point in time that there will be a low entropy fluctuation in the universe meaning that time will actually travel backwards flowing toward a lower entropy state Boltzmann actually believed this was an explanation for the Big Bang although that idea has now been discredited over the years now there is a more philosophical debate about the nature of time and how it actually progresses and this falls into two camps of tencel s and tensed theories of time the tense theory of time states that the future does not exist yet that those there branches of time that kind of spread out as time progresses forward but it's created as it goes the tense list theory of time states that the past present and future are all equally real and we are just traveling along that timeline on the now deterministic a bit lacking freewill yeah a whole other can of worms that I won't get into here absolutely of course time was always considered to be an independent force in the universe until Einstein came along and realized that time and space are two sides of the same coin that coin beings force space-time actually to be fair Einstein was one of two people who came up with this theory of space-time the other one being Hermann Minkowski Einstein stated in his 1905 paper on special relativity that the laws of physics and the speed of light must be the same for all uniformly moving observers and for this to be true space and time can no longer be independent this was the only way for the speed of light to be constant for all observers but it was Minkowski three years later who came up with the idea that space and time could be seen as a single four-dimensional space-time fabric he closed out his paper on the subject by saying henceforth space by itself and time by itself are doomed to fade away into mere shadows and only a kind of union of the two will preserve an independent reality I mean Kowski by the way was famous for using what he called light cones to show how an object travels through its world line in space and time so now we know the space and time are connected here's something else that we know the universe and all the space that encompasses it is expanding we know this because the further away a galaxy is the faster its traveling away from us and that's because the space between us and that galaxy itself is stretching and the force behind the stretching is what we call dark energy dark because we have no idea what it is so could it be that since we know that space and time are connected and that they are expanding that what we perceive over the forward motion of time is in actuality simply the expansion of space-time and if we came to understand dark energy and we're able to reverse it would that actually constrict space-time and in effect reverse time and this leads me to one of my biggest pet peeves about the way time is portrayed in TV and movies because you always see it as if someone is just kind of leaping from one time to another like in Back to the Future where it doesn't make sense when you think about it because the time and space are connected then you're not just jumping to another time you're also jumping to another point in space which is basically teleporting and nobody ever talks about that so I mean consider that the planet is revolving at 1600 kilometers an hour so if you went back even five minutes you would wind up like a hundred and thirty kilometers off of where you started but it gets even crazier than that because the earth is also rotating around the Sun and it's traveling like 30 kilometres a second going around the Sun well you would wind up like 9,000 kilometers off from where you started which means you're either stranded out in space or you're like buried in the mantle and like vaporizing underneath the crust of the earth bad situation either way but actually gets even crazier than that because the Sun was traveling around the Milky Way it like 230 kilometers a second so you would wind up like 70,000 miles of course from where you started it's wrong a good situation and that's only going back five minutes imagine going back a day or a year or a hundred years or something like that the level of accuracy you would have to have to not wind up stranded out in space or buried somewhere deep in the planet it's it's almost impossible it's it's it's there's almost no way to pull it off so the only conceivable way I makes any sense anyway to go back in time is to go back along the same timeline that got you to where you were in the first place so what would that look like it would look something like this to the outside observer a person traveling backwards in time would be exactly that a person in Reverse the perspective of the reverse time person would of course look normal to them and everybody else would be reversed in time I can only assume this would have to entail some kind of temporal bubble around the reverse time person that allows this to take place but by traveling backwards along the same timeline as before you ensure that you don't get you know thrown off the spatial plane as well and you can just sit there in your comfy chair moving along through time reversed from the rest of the world which by the way one might argue this would make you a kind of antimatter because according to some interpretations antimatter is simply regular matter traveling backwards in time now this is also very limiting because for one thing you're moving backwards at one second per second so if you wanted to go back a year you would literally have to just sit there for a year though if we're controlling dark energy I guess you could just increase the rate of dark energy to compress space-time more and therefore speed faster through time another question though is would you age inside of this temporal bubble in which case you could only travel back in time so far before you reach the point when you were born and theoretically you wouldn't even be able to go beyond that ironically the time machine by HD wells which is one of the very first science-fiction stories to involve time travel kind of got this right a lot better and it's a lot closer to what reality would possibly be than a lot of the time-travel stuff that we see these days now that's pretty fantastical stuff about traveling into the past obviously but traveling into the future is totally something that's possible you can actually do that in fact you're doing it right now now yes we are all time travelers in a sense traveling forward in time at one second per second but if you travel at relativistic speeds you can actually speed that up quite a bit as Einstein's general theory of relativity shows the closer you get to the speed of light the more your temporal progression slows down which means that you actually experience time a lot slower than the rest of the world which means that you are kind of traveling into their future faster you could say that time keeps on slippin slippin slippin into the future this is known as time dilation but you guys knows all this you seen interstellar unless thing I'll leave you with here goes back to that whole how we perceive thing because as we all know the older we get the faster time seems to pass this is sort of a universal thing we all seem to experience it but there is a reason for it because we don't experience time linearly we experience it proportionally we interpret time as a proportion of the time that we've been alive so if you're four years old one year is 25% of your life it is 25% of everything you have ever experienced that's a big chunk of your life but if you're 51 year is like 2% of your life which feels like much less because it is much less ultimately time is a construct that we organize our lives around but the only time that really matters is right now no matter what you're doing whenever and wherever you are you are living in a perpetual now the moment you were living right now is the only time that moment is ever gonna happen in all of history so make the most of it that doesn't mean you have to go climb mountains or make every moment big it just means from time to time throughout your day just kind of stop for a second just soak it in they say that depression comes from living in the past and anxiety comes from living in the future but happiness that comes from living right now so embrace it so much of what we understand about time came from Einstein and his special theory of relativity so if that's something you've never quite gotten your head around something you've always kind of struggled with one place that you can learn a lot more about it is the special relativity course on brilliant organ this course will walk you through Einsteins breakthrough theory by showing you the kinds of problems that play physicists back in his day and how his theories solve those problems using fun interactive games and puzzles this course will give you a deeper understanding of relativity than you ever had before from the speed of light to the real meaning of e equals mc-squared this of course is just one of many courses on brilliant that will change the way you look at the world brilliant is an online learning platform that's different because it doesn't just throw facts at your face it actually teaches you problem-solving so that you can think like a scientist and apply that to all places of your life and with their new daily challenges feature you can develop a learning habit to keep that brain growing all throughout the year you can sign up 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would like to join them and get early access to videos and just be a part of a really awesome community you can go to patreon.com/scishow so Joe please like and share this video if you liked it and if this is your first time here I've got a video right here you might want to check out you might like it too or any of the others that Google might be suggesting for you down there I invite you to check those out and if you do like them maybe hit subscribe I invite you to join us because I come back with videos every Monday and every Thursday on fun science II and and future topics and stuff t-shirts available at all ways it answers with Joe calm slash shirts thank you so much for watching you guys go out and now I have an eye-opening rest of the week and I'll see you next Monday love you guys take care

Channel: Joe Scott

Views: 260,701

Rating: 4.8720903 out of 5

Keywords: answers with joe, time, einstein, spacetime, time travel, the time machine, tensed theory of time, tenseless theory of time, special theory of relativity, atomic clock, cesium 133, St. augustine, entropy, second law of thermodynamics, ludwig Boltzmann, Hermann minkowski, dark energy

Id: Yhzz47J0tro

Length: 16min 53sec (1013 seconds)

Published: Mon Jun 03 2019