Why is Time a One-Way Street?

Leonard Susskind
June 26, 2013
Anyone can see that the past is different from the future. Anyone, that is, but theoretical physicists, whose equations do not seem to distinguish the past from the future. How, then, do physicists understand the "arrow of time" - the fact that the past and future are so different? Leonard Susskind will discuss the paradox of time's arrow and how physicists and cosmologists view it today.

[@henrikrynauw244]

Awesome video ! Leonard is an amazing lecturer.

[@supertuesday600]

This is one of the best lecture you can watch on youtube. I've learnt alot. Thanks Lenny!

[@kensears5099]

Time-Space is aptly named, because the felt phenomenon of time, i.e., the changes, the motion and development, are spatial ones, which we feel/interpret as "Time". However, the "space" is observable; the "time" is not--PARTICULARLY as some sort of time-tunnel-environment IN WHICH "space" is moving, from past to future. Really, no such "time" exists. Space is ALWAYS "now", and the "developing" of "now" is what we interpret to ourselves as "Time". But it's all ALWAYS "here", "now".

[@yargoook3802]

Found myself thinking of Jeremy England's ideas about order and entropy several times during this excellent talk.

[@dk6024]

Nice complement to Sean Carroll's excellent discussion of this.

[@SpiritMolecule]

very interesting talk. thank you for sharing

[@bammbamm12]

A "conclusion" is where a man arrives when he gets sick of thinking.

[@joaquinpenroz7719]

Incredible physicist ... among all that I know, none explain matters better than Leonard !

[@CasperThePaperChaser]

This lecture is legendary.

[@vinm300]

Susskind is the best lecturer. 41:00 Jacob Bekenstein, is the name Susskind cannot remember.

[@scholar1972]

Lenny have over 300 lectures on KZbin. All of his lectures are clear and brevity. I have read his Ph.D thesis from Cornell.

[@sigmatau8231]

...this man is great

[@christopherhein9975]

It's been 5 years!

[@yargoook3802]

Space and time are a unit. Spacetime. Space is expanding. What is time doing?

[@mikegale9757]

Time passes at different rates for different observers. The universe is a vast, ancient sphere from our point of view, but it's a young pancake for a primordial photon. How long does it have to wait for one of Lenny's bubbles? Does it perceive its disk universe to be expanding? And what's the speed of time?

[@MARILYNANDERSON88]

"No time dependence for the changes in the constants of nature"- most changes in the "constants" on which we compute our reality are random and stepwise in nature, and relative position in space may be more meaningful than time when considering infinitesimal small parcels of space...

[@piotragier9676]

Does anybody have an idea what was the first question from the audience about? Seemed interesting.

[@scholar1972]

I have watched all of his talks and his lectures and most of his papers. He have/had an influence on my ideas on theoretical physics and elementary particle physics.

[@x69WINNING69x]

Question: do we forget about the universe in a box theory because of the boltzmann brain idea where the probability of our universe is far too low to be expected?

[@Grimthang]

Check out the series "what we still don't know" They go trough from the start when there are just the elements in the big bang to how those elements created all ect. one of the best documentaries i've seen in years.

[@sammyboy211v]

Can someone help an amateur to understand the state of the universe that Prof. Susskind describes around 40:30? He explains that at the cosmic horizon, there will be quantum energy (fluctuating particles). It's not clear if this is true before all matter passes through the horizon, but nevertheless, the cosmic horizon is described as the distance form a "fixed point" (the sun) to an object moving with the speed of light. My "questions" are therefore: Would this not be true for ANY point in space? Depending of what object you would choose as fixed. And as a result the sun (or the earth) would be at a cosmic horizon? Actually, any point in space would at a cosmic horizon. Is this messurable? To Illustrate, in the slide showing Hubble's Law (38:40) if you put a planet / star anywhere on a circle 2x the distance of the cosmic horizon from the sun, that would put the sun in that planet / star’s cosmic horizon.

[@naimulhaq9626]

Besides being real, time can be complex. Nahin (An Imaginary Tale...) explains how the equations of motion of a man and a bus tells us if the man can catch the bus. This is done by interpreting complex components of time, that explains if the man can catch the bus or not. In doing so he explains how complex time maybe interpreted as indicating space !!!

[@MrDaanjanssen]

29:22 story of my life

[@xjuhox]

Just love this man.

[@Invictus131313]

This was an interesting lecture on how to reason from the premise of the weak anthropic principle. But what if the weak anthropic principle explains nothing? And the strong antrhopic principle explains why? It's seems odd that we should have to, *literally*, make things up (like m-theory) just to satisfy a weak anthropic interpretation of cosmology.

[@liboriofede7569]

How one can define the numerical value of the the probabilistic terms of these equations?

[@tejasgokhale01]

Isn't cosmic horizon just a mathematical limit beyond which we can't see? There isn't any physical boundary there and we may be on cosmic horizon for creatures in some far distant galaxy. What then does it mean to say that cosmic horizon has a temperature giving off hawking radiation?

[@King_Flippy_Nips]

pretty sure a lot of scientists agree(i do as well) that time is not a one way street, its just that we are only able to perceive its forward movement in space

[@JeffreyLXV_older]

Give the man a chair or a stool and some water. He's almost falling over near the end.

[@ericpalmer8549]

There is now. What we call past is information that is in the now. We didn't come from the past and we aren't going in to the future. It's now.

[@Oners82]

Well you could say exactly the same about a black hole. There is no physical boundary, just a mathematical boundary. The point is that even though the boundary is a conceptual construction, physical processes still occur at it.

[@johnkechagais7096]

Weather the planets are moving clockwise or anticlockwise they can still be only moving forward in time, Imagine something moving backward and forwards on a number line, say the x axis. Then grab that axis an make it move in the positive y direction. the moving backwards and forwards on the x axis does not mean it is moving backwards on the y direction. 3 dimensional space could simply be drifting forward in the time direction. The time dimension is not really treated the same as other directions in the laws of physics because it is often calculated in multiples of the i. The analogy used by Susskind breaks down as to the laws of physics not having a preferred direction and another way to demonstrate, or prove that needs to be thought up.

[@roy8200]

lol now that's the way to start a speech!

[@stainsbflowin]

7:01 is what you came here for

[@MikeRoePhonicsMusic]

What if the region outside of the edge of our Universe is just that...a region. But a region which is at complete and total equilibrium, thus "nothing" happens there.

[@ReiverBlue1971]

Before I start, I am by no means denying true physicists current opinions of time related to space. BUT, what if our perception of time is directly related/required for us to experience our existence within just 3 dimensional space? Is it possible that our perception of time moving in a constant direction is necessary for us to perceive our situation as purely in the 3 dimensions? If time were viewed as a variable similar to XY and Z in space then is it possible that our view of the universe (as "everything") would have to expand to beyond just these 3 dimensions? Is entropy an illusion created by perceiving our situation in just 3 dimensions? I suggest here various views of a similar concept. Lovely delivery of a complex concept :)

[@jacopman]

Time is the quantum slice dimensions of casualty. In our universe at the macro level it is represented by the 2nd law of thermodynamics within a closed system. At the quantum level it is demonstrated to be fluctuating independent of such a law. Time is not a duration but a condition of a dimension of space.

[@JonathanLangdale]

One thing that I've always wondered about and I wish I could ask Susskind is if there might be Hawking Radition on the cosmic horizon, or, if that only applies to black holes because of space-time curvature. Does that mean the cosmic horizon is not curvature? Also, why can't there be virtual blackholes and virtual hawking radiation in the vacuum?

[@RevBobAldo]

The usual progression of events, and time itself may be two quite separate things. That is, although events seem to follow one after the other (moving toward the future), the "time" for them to take place in is unfolding (flowing) from the future through the present and into the past. Picture a reel to reel tape recorder. The unrecorded tape (future) passes through the record head (present) and onto the take-up reel (the past - history). Time in itself may well "move" in such a manner.

[@LaureanoLuna]

0:45:45 Empty space with a lot of dark energy; that makes no sense to me. All theories claiming the universe came out of a vacuum by accident fail to explain whether that vacuum was absolutely nothing or not, and if not, why it was there. They also fail to explain how physical laws (e.g. quantum fluctuations) can apply before the physical universe existed.

[@mikolasinyuk8298]

We have one time dimension in 3d world, but what if our world will consist of 9 space dimensions?

[@kidzbop38isstraightfire92]

9:08 i want that as my ringtone

[@navneetrfs]

Now I can watch tenet movie again and finally understand it

[@yargoook3802]

23:53 Nietzsche's Eternal Recurrence...

[@miguelnglopes]

Genial!

[@ByteSci]

If the bubbling off is true, there should be residual radiation that is detectable. If we know where to look.

[@ajholloway4325]

What if (+ Lambda) and (- Lambda) were in a state of quantum duality? Or simply, both happening at the same Time? Think of the boundary between these two quantum states as the universal horizon.. Or the breach of "Boundaries" in "Photonics/Physics" relative to the cosmological constant known as the speed limit Of/For information Transfer/Sharing. Also this relates to black holes as a sort of "Pond" within, but still externally connected through "Underground" water tables..(Analogy). Just a thought? It may be a ridicules idea, and if so, I'm sorry for the distraction, but id like a to know why I'm thinking retiredly. Thank you for sharing with all others!

[@tokkahontas]

didn't just a few days ago they figure out the micro-organism E-coli doesn't age or go through any sort of entropy?

[@sepuste]

"Why is Time a One-Way Street?" Because it's not a dimension: it's just a sequence of events: the movement of the Earth around the sun, the regular clickings of a clock, or casual or one time events. It's a concept. And, as a sequence, it can only have the direction from the first event to the last, not the other way around.

[@kensears5099]

Time MUST be a "one-way street", in the most metaphorical of sense, precisely because there IS no street. That is, if there really WERE a "street", i.e., an environment, a tunnel, a corridor full of doors, in Hollywood style, then there could be two-way travel within the environment. But if the environment doesn't EXIST, there can be no "travel" IN it. It doesn't exist. No one has ever observed it. It's not there to BE observed. All we EVER observe is... NOW.

[@chuckschillingvideos]

Time is a one way street for a very simple, very intuitive reason. Not one person - no scientist, philosopher, etc. No one - has ever proposed a scientifically plausible, much less practical, means of "undoing" an event once it has occurred. Even if you presume that by some means it would be possible to travel to the past, no one has proposed a means by which the intervening events could be made to have never occurred.

[@jwoya]

"Why does time have an 'arrow' of directionality? Simple. It is a process, not a place. There is no such place as time." This seems like a pre-Einstein notion of time. Because time passes at different relative rates, there is real physical meaning to an object's observed coordinates ("place") in spacetime. A photon has been at the same point in time since the beginning of the universe.

[@JeffTheHokie]

The explanation is circular. He is using time (a dynamic model with change, motion, interaction, cause and effect) to define why there is time. The problem is motion, change and interaction require time to already be defined. The vortexes which he is proposing as the cause of time, were put into motion by an event in their past, so they already depended on time. To define time without circular logic, you would need to use a static 4 (or more) dimensional model.

[@SeanMauer]

So it comes down to a model of the universe that requires an disequilibrium between 3 space-time and 3+ space, providing vortices (or in modern terms vortexes) to form. Interesting thing, I just made a video on this that includes the role of gravity in the vortices cosmology, called "What is Inertia"

[@jack999rocks]

According to the equation and Colored lined / Bubble's formation - Does that also imply that : As Time moves ahead - the Universes Life Span would decrease drastically ? OR is that mean the Size of the New Universes lessen with Time - which also means that the Life in the Small Universes would be small in structure (size) ? SCIENCE Fiction Story - Than the Life in the Small Universe would have more capability to travel between Universes - even to the larger ones if they have more or less similar properties like in our Universe. :) Enjoy.

[@justinhill6206]

In my limited knowledge the cosmic horizon is the point at which matter is moving so fast away from us (the further matter is from us the faster it is moving away)that the waves emitted or reflected from that matter are redshifted out of detection . So yes Alice`s data is redshifted out of Bob`s detection as long as Alice and Bob are at the stated distance from each other . Can a real scientist please correct me if wrong thank you

[@Mayburyj]

The analogy is assuming that the world of possibilities is flat however the basis of entropy is that order is uphill from the chaos. So the blue region is uphill from the white area and the pink region is a mountain. Therefore the chance of coming into the blue region can be less than zero if there is not enough energy.

[@josephmarcotte328]

Correction: This sub variation of the expanding universe does not expand forever because it must have a maximum size limitation obeying the laws of finite physics just like the speed of light velocity limitation has to on it's maximum end. because they are both classified as measurable quantities by the laws of finite physics and must obey. There's nothing infinitive within finite history properties.

[@kspangsege]

Who is the introducer?

[@FluidH2O]

I don't believe spacetime is actually producing time. Time being propogation of vibrations within the atom. We measure time with atoms and not with 'empty' space. Also photons moving with lightspeed have time=0 and don't have time to decay. This makes them very stable. Within a field of gravity all atoms (particles with mass) will experience a slowing down of ticks and having the 'same' time.

[@hillwalker8741]

Not sure he addressed the topic. Why not doubt the big bang at least to the extent that it is still banging (and increasing at that). All the space that is being created everywhere is our experience of time. Time should be gradually ticking faster. The arrow of time has to do with the nature of the creation of space. Perhaps with each plank unit of space that is created we experience one plank unit of time. I'm sure I could fill a lecture with such a theory and not get so far off topic.

[@ionjerdea8147]

SUPER

[@wirednotice]

im guessing you didn't understand the lecture

[@davidwilkie9551]

Why Precision is not Accuracy, because one condensed e-Pi-i sync-duration measurement is always incomplete in QM-TIME Eternity-now holography Dimensionality Interval Completeness, ie continuous cause-effect probability in potential sum-of-all-histories possibilities.., so is inevitably a One Way Street of Logarithmic Time Duration Timing Duality, and wave-packaging sight-plane Reciproction-recirculation Singularity of projection-drawing positioning, composed of hyper-hypo floating modular In-form-ation, or pure-math relative-timing ratio-rates motion-> QM=Quiescent hyperfluid Actuality.

[@slowmopoke]

tell that to a hole sailin' on the dirac sea....

[@Dyslexic-Artist-Theory-on-Time]

Why does time advance? < Photon momentum This is an invitation to see a theory on the physics of light and time!

[@beattoedtli1040]

How can Susskind claim we don't live inside a Boltzmann brain? We just don't know!

[@beattoedtli1040]

Yes, the predictions of this theory are absurd. But the timescales to which we extrapolate our current physics are just absurdely large. The same in particle physics- we ask about the GUT or Planck scale after having found the Higgs. There are > 10 orders of magnitude till there and we've found new physics in every factor of ten in the past.

[@frankbraker]

if the space of "all possible configurations" (at 24:43) is infinite, then there's no "just takes longer"? If it's just takes longer, why wouldn't it paint a Hamiltonian circuit and just loop forever?

[@Folkstone57]

What is the "it" that you are tlaking about painting a Hamiltonian circuit ? Also, why would anything do something like this ?

[@frankbraker]

okay - What I don't understand is - can objects move completely freely in space (infinite possible locations) or does the Planck length give location granularity, so that space of "all possible configurations" really is finite (and sorry if I misunderstood what he's saying at 24:43). I've been wondering about this since the discussion of multi-verse came out years ago. To restate the question, do Planck length limits apply granularity to the size and shape of vacuum?

[@Folkstone57]

I guess that depends on what you mean by "completely" because of course, a tennis ball can more freely but it still has to take into account the wind, the net, the rackets, etc . I don't think the Plank length makes any real difference unless the object is incredibly small. Objects smaller than the Plank length would not be objects we can detect, so the answer there is we currently can't know about objects that small. I doubt this answers your question but it's the best I can come up with.

[@frankbraker]

thanks. When I read about the multiverse the first time, the claim was there might be another Hubble volume that contained an almost exact duplicate of my body. Which, if vacuum was also granular (i.e. things don't move with infinite variation) might make sense. The universe becomes an enormous random number generator with a seed size of (size of the universe / Planck length ) digits. Any finite seed size on a random number generator has to eventually loop. So this is why I used the term Hamiltonian circuit. [Maybe my line of thinking is wrong, but I can at least try to express my question clearly.] :)

[@MadaxeMunkeee]

Well the laws are probabilistic in this model really, at least the way he's painting it using the ideal-gas metaphor. So it doesn't seem likely that it could form a closed path, and there's no motivating factor for it to keep circling around even if it did, I suppose.

[@thomasglen3547]

Time is a miraculous material measurement of our short lifetimes, with a great need to learn of our greater spiritual reality.. Spirituality is timeless and an enlightened person, educated or uneducated, can enjoy the timelessness of that other dimension..

[@attractor9]

space is also a one-way-street.

[@STEFJANY]

For physical reality objects the arrow of time makes them transform from a lower entropy (egg) to a more disorganized world with a higher entropy (omelet). For consciousness is the opposite from high entropy low quality hate fear anger to a lower entropy love, charity compassion, high quality consciousness.

[@awad7391]

time is just a human concept to organize the unfolding of events, in my opinion.Maybe its a flaw of the mind, and not something that exists.

[@tgillet1]

Is there any reason why the asymmetry of new universes wouldn't itself eliminate the possibility of the Boltzman Brain in the expanding and bubbling scenario? It seems to me if there as a mechanism for the generation of a new universe, and only new universes with certain qualities can result in human life (and thus no Bolztman Brain scenario would occur because that universe wouldn't actually lead to a single brain), then we would "be there" and no longer be "stuck"? There are plenty of planets out there. Likely some of them have life on them, and there may be many types of life, but we can be confident that many more planets will have life that starts out simple with bacteria and the like and then develop into complex things with brains than there are planets that start out with things with brains.

[@mejislasher]

Well said. I'm sad to see so many confused people

[@paulahuja1927]

As long as there is past there will be future. as long as there is future there will be now. as long as there is now there will be always past and future. You are born, you die. You die you are born. hand of time goes round and round on and on.......... And now I am dizzy .

[@Lokmeujasanginatwite]

BUBBLES!!

[@zholud]

How come can milk assemble itself against gravity?

[@frankbraker]

Let's just assume time isn't a one-way street and that it actually goes in both directions. Then the question is just about why memory appears to favor time in one direction, and why people don't often walk backwards...

[@ktx49]

why do we need "regions" of space to randomly pop into existence with different laws of physics to create new fractal-universes when we have black holes? to me the fractal picture Leonard displayed in his presentation is far too complicated and assuming....instead I think the fractal pattern exists within the formation of black holes where the black hole's horizon provides the EXACT analogy of our universes event horizon just as he mentioned earlier. so instead of fluctuations creating new bubble universes, we just need black holes to form and those create universes...and inside that "new universe" every black hole that forms creates another universe and so on, and so on.....much simpler picture and something we actually have empirical evidence for.

[@gunterra1]

The past is merely the present that has already gone by. In reality. the past does not exist; we merely remember it. it only appears that way. It is a record in out minds memory, we experienced it, we have had it, and so we know what it 'was'. As to the the future, that 'time' that has not come into existence yet, it's a little different. What is the best way to know the future? By creating it (in present time of course). Basically time is merely a consideration we daily make and having agreed that it is so it become real. None of those things exist outside of our living and experience. There would be no one there to assign meaning to it. That's about all there is to it.

[@gitaarmanad3048]

If we want to understand what time realy is, shouldn't we wonder why time is actually standing still in a singularity? Singularity is where both mass and time jump to another scale ,or dimension if you like this term better. What happens with time when one approach the speed of light? Well, both the frequency matter and also time are slowing down because the non dimensional particle that forms matter is moving with lightspeed. When we are too, both matter and time become non existent.

[@MathMan271]

Oh, I understood it completely; I'm not sure you did though.

[@tonyinhk888]

I agree with earlier comment by jbyeats. Time is not a dimension of the Universe, like what Einstein said. Time is simply a human invention, like money, that has never existed in nature, but to help we human beings to record things in an orderly manner, and to make appointments and schedules. What we observe things of the past are changes in states, including various objects moving in space, but not moving in space-time, and because of this we cannot physically go back to the past, or take a trip to the future, as suggested by Einstein's Relativity Theories.

[@MrKorrazonCold]

Because centre is everywhere within every ocean of waves there is always pressure at every point as the waves come from a distance radius thus everything is vibrating wavefronts of energy compressing/ decompressing two opposing vortices forming the sinusoidal wave medium density (space) at each and every point of space.. . .or contracting and expanding virtual pairs coming into and out of existence thus every instance of C has an anti+C.. . .Electrical potential is the same as future potential within a ref-frame.. . .And atoms and particles are really wave centres from regions of intense wave pressure. . ..made of vibrating wavefronts called shells in particle physics.. . . that have been multiplied to infinity, within the active cores of galaxies the pair's cannot escape contracting time and space compressing energy input into singularities forming an equal and opposite explosive decompression of Cosmic Ray Jets and Synchrotron radiation expanding outward via the poles.. . . Vibrating matter is simulating rest and balance now through violent motion.. . .The more violent the opposed vibrating motion oscillating within that 3D centred ref-frame the slower time runs.. . .Stimulated emission now is a process by the way of which a higher quantum mechanical state of a particle through a photon is then converted to a lower level resulting in the production of light.. . .In quantum computing the two energy states of a Cubit can be an atom, electron, or a photon.. . . All information is recorded magnetically via two equal pairs of opposite expression called Cubits.. . .Each of the pair cancels the other out in cyclic periodicities.. . .Each of the pair then becomes what the other was switching trillions of times from matter to antimatter.. . .Their output was the negation of their input: 0 goes to 1,1 to 0.. . .the start of a Fibonacci sequence.. . . Cosmic rays are 89% hydrogen nuclei, 10% helium nuclei, and 1% everything else formed by E2 as the waves come from a distance radius (4pi R2) and outward now from its source.. . .And these are now entangling+/-unfolding wavefronts therefore is no problem with entanglement (Huygens wavelets) Like dropping a pebble into a pond dividing one unit of space/multiplied by one unit of time dilation.. . .Vibrating matter is a fine mixture of positive and negative electric changes coming into and out of existence.. . .Matter negative electric charge and antimatter positive electric charge forms a profound and perfect symmetry forming and when that symmetry is broken forms the imperfect spiral symmetry of the Fibonacci sequence seen everywhere in nature.. . . Therefore, because everything is contracting and expanding a locational spherical inward absorption density t=0 and now outward emission density of photon oscillations or vibrating quantized spherical electromagnetic wavefronts (2pi) forming resonance antimatter matter annihilation, forming positive and negative electric charge and electromagnetic interference fields as time unfolds C2.. . .their individual light spheres superimpose as crests and troughs become In phase now, their space time lines will synchronize, or amplify multiplying electrical potential along cubic dynameters compressing the wave amplitude now+4-0-4+-the shorter the expanding transverse wavelengths dividing acceleration away in unison inversely proportional to the square of the distance from the source of that constant expanding light sphere.. . . E2=mc2c4+p2c2.. . .Time is inverse multiplying+/-dividing like frequency and wavelength.. . . E2 compressing energy input=+mass. decompressing a constant C2 as time unfolds.. . .Acceleration is not the thrust from a rocket nor the fuel but an equal and opposite reaction -Gravitation is a second force from the electromagnetic weak force!!! Now is the moment of emission and by manipulating this process of spherical symmetry forming and breaking a physicist shines a 2pi pulse on an electron and its output was the negation of its input: 0 goes to 1,1 to 0.. . .and this time line can be seen in the mirror or line symmetry of the individual ref-frame relative from the perspective of an outside observer.. . .All things are One, appearing as two opposite extensions of the centred One.. . .Like each neuron within the brain that has a voltage which changes when ions flow inward and outward from a cell.. . .Once a neurons voltage reaches a certain level of subconscious energy compression, it will then consciously fire (C) an electrical signal to other cells, which repeat the process.. . .And, depending which neurons gets stimulated through repetition, certain neural connections become stronger and more efficient, whilst others may become weaker as time unfolds into statistical entropy.. . .This is called neuroplasticity.. . . The traditional assumption of spacetime, where space is three-dimensional and time plays the role of a fourth dimension is inaccurate.. . .If we would want to study the origin of the universe we would actually have to look "forward," since Cnows time vector direction is opposite to the arrow of distance - from which we perceive an expanding universe.. . .

[@uberhikari]

@15:21 Why are there 9 planets in that solar system? lol

[@thegun1649]

FRACTAL flow by Tesla

[@Newtube_Channel]

Just give a simple example of Random motion. They are processes which all show a definitive direction of time. As an example, a Fractal Flow is somewhat elaborate and unnecessary. Still doesn't explain why we witness singular direction of time. Fair enough. Nature merely evolves as a function of its environment. Namely we can only interpret the world based on the how the world is. It may never be evident. Physics is a joke. Open Physics topics need to be taken far more seriously at an elementary level.

[@TheisticThinker]

No, not necessarily. In a Universe with a constant Hubble parameter there is a true horizon just like a black hole. The observable universe only grows to a finite size in an infinite time.

[@Texas75023]

It's too bad *NOTHING* in our observable, measurable Universe . . . is Infinite. Including Time.

[@gunterra1]

"the planets in the solar system move clock wise?" Really? Not so. It totally depends from where one looks. From the opposite side, so to speak, they would move counter clockwise, obviously. No a good example, isn't it?

[@justinhill6206]

I forgot to mention the cosmological redshift is due to the universe expanding which stretches the waves further I believe

[@michielzoelman1380]

It should be a requirement that every scientist must have atleast one experience on psychedelic drugs. Where you understand that you are a little drop out of the ocean of counciousness (unified field) falling back into that field. Experiencing the whole picture. There is just no way quantum theories and time etc can be understand in a sober ape mind. At light speed time doesnt exist and the whole universe is created in an instant. Simultaneously something that has weight creating time based on how heavy something is and how fast it goes. In religious words, god is and god is becoming at the same time. You are god playing a game with yourself, pretending you are not alone and slowly building to be one again.

[@Scumbot404]

When ppl learned to measure things, time was one of them. Later they divided time into smaller units of measures. This way ppl learned to sense proceeding time when earlier everything happened "now". Time is two things: 1. a human can experience time (ie. one sees an object moving from A to B) 2. measure (clock is based on earths rotation)

[@nidieunimaitre613]

I don't quite get why ONE single brain would be more likely than many... The "many" property allows for gradual improvement through evolution and/or cooperation through time.... (in the same way that a child is more likely to be born with a couple of parents than with just one parent!)

[@bphoenix777]

All very interesting theories - my take is that time as we experience it is not the cosmological time, but requires a body consciousness to be experienced. Outside of consciousness all bets are off, time can go in any direction or speed. The reason the experience of time needs a body is, that in a living body the arrow of thermodynamics is reversed and the body is constantly renewing itself from the center and eroding at the outside until death. This is the only reason we experience time as linear...

[@narrator69]

OK, for as long as I've followed cosmology Hubble's constant made no sense to me. It only makes sense that galaxies farther away are travelling faster as they are further back in time and haven't slowed as much as the ones closer to the observer. So how does that prove the universe is accelerating?

[@MrKorrazonCold]

Time only moves forward because all forces of nature are formed by E2 a locational spherical inward absorption density 4pi R2 and outward emission density 2pi Re2 of electromagnetic quantized wave fronts, forming antimatter matter annihilation, + and -electric charge and EM-fields, or resonance and interference now as time unfolds C2 forming an inward force called gravity from objects, relative to their own energy or mass, at the centre of their own 3D ref-frames within the infinite Universe."

[@bammbamm12]

If we can observe the universe expanding, then why do the constellations look the same to us as they did to the ancient Greeks?

[@8twospiders]

Time feels like a crystal. Everything that has ever happened or will ever happen, has already happened. If not we have to accept the multiverse.

[@bektaskonca5189]

time is never a one way system that is primitive thinking...