“Time” is the most used noun in the English language, yet it remains a mystery. We’ve just completed an amazingly intense and rewarding multidisciplinary conference on the nature of time, and my brain is swimming with ideas and new questions. Rather than trying a summary (the talks will be online soon), here’s my stab at a top ten list partly inspired by our discussions: the things everyone should know about time. [Update: all of these are things I think are true, after quite a bit of deliberation. Not everyone agrees, although of course they should.]
1. Time exists. Might as well get this common question out of the way. Of course time exists — otherwise how would we set our alarm clocks? Time organizes the universe into an ordered series of moments, and thank goodness; what a mess it would be if reality were complete different from moment to moment. The real question is whether or not time is fundamental, or perhaps emergent. We used to think that “temperature” was a basic category of nature, but now we know it emerges from the motion of atoms. When it comes to whether time is fundamental, the answer is: nobody knows. My bet is “yes,” but we’ll need to understand quantum gravity much better before we can say for sure.
2. The past and future are equally real. This isn’t completely accepted, but it should be. Intuitively we think that the “now” is real, while the past is fixed and in the books, and the future hasn’t yet occurred. But physics teaches us something remarkable: every event in the past and future is implicit in the current moment. This is hard to see in our everyday lives, since we’re nowhere close to knowing everything about the universe at any moment, nor will we ever be — but the equations don’t lie. As Einstein put it, “It appears therefore more natural to think of physical reality as a four dimensional existence, instead of, as hitherto, the evolution of a three dimensional existence.”
3. Everyone experiences time differently. This is true at the level of both physics and biology. Within physics, we used to have Sir Isaac Newton’s view of time, which was universal and shared by everyone. But then Einstein came along and explained that how much time elapses for a person depends on how they travel through space (especially near the speed of light) as well as the gravitational field (especially if its near a black hole). From a biological or psychological perspective, the time measured by atomic clocks isn’t as important as the time measured by our internal rhythms and the accumulation of memories. That happens differently depending on who we are and what we are experiencing; there’s a real sense in which time moves more quickly when we’re older.
4. You live in the past. About 80 milliseconds in the past, to be precise. Use one hand to touch your nose, and the other to touch one of your feet, at exactly the same time. You will experience them as simultaneous acts. But that’s mysterious — clearly it takes more time for the signal to travel up your nerves from your feet to your brain than from your nose. The reconciliation is simple: our conscious experience takes time to assemble, and your brain waits for all the relevant input before it experiences the “now.” Experiments have shown that the lag between things happening and us experiencing them is about 80 milliseconds. (Via conference participant David Eagleman.)
5. Your memory isn’t as good as you think. When you remember an event in the past, your brain uses a very similar technique to imagining the future. The process is less like “replaying a video” than “putting on a play from a script.” If the script is wrong for whatever reason, you can have a false memory that is just as vivid as a true one. Eyewitness testimony, it turns out, is one of the least reliable forms of evidence allowed into courtrooms. (Via conference participants Kathleen McDermott and Henry Roediger.)
6. Consciousness depends on manipulating time. Many cognitive abilities are important for consciousness, and we don’t yet have a complete picture. But it’s clear that the ability to manipulate time and possibility is a crucial feature. In contrast to aquatic life, land-based animals, whose vision-based sensory field extends for hundreds of meters, have time to contemplate a variety of actions and pick the best one. The origin of grammar allowed us to talk about such hypothetical futures with each other. Consciousness wouldn’t be possible without the ability to imagine other times. (Via conference participant Malcolm MacIver.)
7. Disorder increases as time passes. At the heart of every difference between the past and future — memory, aging, causality, free will — is the fact that the universe is evolving from order to disorder. Entropy is increasing, as we physicists say. There are more ways to be disorderly (high entropy) than orderly (low entropy), so the increase of entropy seems natural. But to explain the lower entropy of past times we need to go all the way back to the Big Bang. We still haven’t answered the hard questions: why was entropy low near the Big Bang, and how does increasing entropy account for memory and causality and all the rest? (We heard great talks by David Albert and David Wallace, among others.)
8. Complexity comes and goes. Other than creationists, most people have no trouble appreciating the difference between “orderly” (low entropy) and “complex.” Entropy increases, but complexity is ephemeral; it increases and decreases in complex ways, unsurprisingly enough. Part of the “job” of complex structures is to increase entropy, e.g. in the origin of life. But we’re far from having a complete understanding of this crucial phenomenon. (Talks by Mike Russell, Richard Lenski, Raissa D’Souza.)
9. Aging can be reversed. We all grow old, part of the general trend toward growing disorder. But it’s only the universe as a whole that must increase in entropy, not every individual piece of it. (Otherwise it would be impossible to build a refrigerator.) Reversing the arrow of time for living organisms is a technological challenge, not a physical impossibility. And we’re making progress on a few fronts: stem cells, yeast, and even (with caveats) mice and human muscle tissue. As one biologist told me: “You and I won’t live forever. But as for our grandkids, I’m not placing any bets.”
10. A lifespan is a billion heartbeats. Complex organisms die. Sad though it is in individual cases, it’s a necessary part of the bigger picture; life pushes out the old to make way for the new. Remarkably, there exist simple scaling laws relating animal metabolism to body mass. Larger animals live longer; but they also metabolize slower, as manifested in slower heart rates. These effects cancel out, so that animals from shrews to blue whales have lifespans with just about equal number of heartbeats — about one and a half billion, if you simply must be precise. In that very real sense, all animal species experience “the same amount of time.” At least, until we master #9 and become immortal. (Amazing talk by Geoffrey West.)
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This is a remarkable article and blog. I wish I’d attended the conference. ATTITUDE to time has long absorbed my interest. The way a person perceives time reveals their character: how they spend time, fear it, waste, save it and so on. I welcome personal attitudes for a book project.
We agonize over a young person terminally ill, but when depressed our salvation is that we are not immortal. Between those extremes a thousand philosophies lie. See my website http://www.perceptionoftime.com and comment.
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What’s mind-blowing is that there are not 3 dimensions of space and then time, but the dimensions are hybridized space-time mixed together. If you manage to “sit still,” you are whizzing along time at nearly the speed of light. If you should move, however, your movement “takes away” from your maximum possible time speed, and time starts to slow as per the equations of time-dilation. If you manage to move at 99% of the speed of light, time slows over 7 times because of your movement. 99.9% slows time by over 22 times, and so on. If you could reach the theoretical maximum light-speed (but you can’t), all the possible speed would be consumed and time would stand still.
Nice article. Seems similar to quantum science whatever it is… 😀 Anyways, great article! 😀
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So, time is space. there was a bang and we said look, let’s call this TIME. the bang is still going on(Space) but how? the bang would not ever happen, there was no time before it! Is just would never have been there. in space or time.
I’m not 100% convinced space exists, let alone time.
From the perspective of a non-physicist (who loves physics and science )…..
Time is the comparison between events. The time it takes to write this sentence is the comparison of the typing of the sentence to the number of ticks (seconds) on a clock.
Time is what allows 3 dimensional entities (us) to experience the events of our reality in a fixed order.
There is no past or future as far as having happened and yet to be. There is simply time and where we are relative to the experiencing of these ordered events. I experience birth before death and events between these compared to the number of ticks on a clock provide the time (or measurement) of my life.
Your past and your future already exist and both are based on the choices you’ve already made (as well as others). We may not yet have experienced all of these events that come from our choices but that has more to do with our being 3 dimensional entities then whether or not they have happened.
It’s hard to properly convey using the written communication of our 3 dimensional existence but I think the above is close.
“Other than creationists”
A superfluous, incorrect and stupid thing to write.
The “past” (as a word/concept/term) can be used in relation to what has been found to have occured (the factual) as much as what could have occured (the speculative). And likewise the “future” is used in relation to what remains to be seen, as much as what might take place.
The past and future may be implicit in the present but the number of possible pasts and futures implied by any given present is either very large or infinite. If the term “reality” is used in relation to both the facts as much as the possible (as is increasingly typical) the term “reality” can become somewhat stretched to the point of being totally ineffective – what does one mean by the word? For example, to say the multiverse is real is to say next to nothing about the multiverse.
The reason for the word “reality” becoming increasingly ineffective (or defective) is quantum mechanics. In QM the possible and the actual are found to be functionally related yet not equivalent.
im curious. if all creatures experience about 1.5 billion heartbeats shouldnt that mean exercise is in fact decreasing your lifespan by burning up those ticks? and shouldnt increasing your metabolism in fact be like increasing the flame on a candle?
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Most of the posts claiming that time is a human construct and therefore fundamentally nonexistent contain the same error: they conflate the human concept of time with the phenomena itself. After demonstrating that our concept of time is human-created, they seem to imagine they’ve proven that the phenomena this concept seeks to explain must therefore also be artifical.
This actually doesn’t add anything to the debate, since the only thing it addresses is the half of the question that almost everyone agrees with already.
The real point – the point the more rigorous posters are attempting to explore – is the nature of the phenomena itself.
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Time is an illusion (but a useful distinction tool), can be disassembled, and only requires 2 physical facts: change/motion, and a memory/storing mechanism (take one or both away, and time doesn’t occur for where an observer-knower occurs). Time simply emerges from mutually-required 1) the continuum in motion (if entirely static, nothing would exist, including consciousness/awareness), and 2) our differencing/comparing engine with its stored states (memory). It’s never other than Now, and the past (even 80 milliseconds ago), and imagined futures, is thought or known only now. This puts everything occuring in the universe across a ‘flat screen’ we call “Now”.
If our current awareness is really 80 milliseconds ago (conscious existence, ‘in the pipeline’ so to speak), yet we physically exist now, then we are doing ‘knowing’ of 2 separate points in time, simultaneously. One can be more unified than that 🙂 Your knower that’s aware of 2 (or more) time points simultaneously is the state we call Now. Anyone thinking we don’t physically exist right now may have alot of fun wasting alot of words trying to prove that notion.
Try this PoV/image: If absolutely everything in the universe stopped (ceased motion), there would be no way to detect time, or how much “time” had elapsed once it commenced motion. Of course, if absolutely everything ceased particle motion and force-field/energy flow, and I mean all of the points that make up all of the threads that are vibrating inside of every vibrating superstring that gives detectable effect to everything we call physical and phsical elements, then ‘it all’ would vanish. Motion is required for physical existence, and the apparency of time, therefore motion is more foundational (the truer truth). Motion (at the continuum level) is necessary to be. Time isn’t required to simply “be”.
The “Rabbit Hole” may seem deep, but there is an understanding where the illusion we call “Time” isn’t a mystery.
I’m no physicist or Mensa member, but here’s my take on things:
1. Everything comes down to Cause & Effect. Everything is based on the past, and everything effects the future. Everything is both a Cause and an Effect.
2. The future is set. Free will does exist, but only as an illusion. Every decision you make is actually dependant on Causes from the past. Your frame of mind leading up to the decision is effected by what’s happened to you in the day leading up to it, your past experiences are going to guide you in making any decision, the exact position and angle that you observe external stimulus from, and on and on into factors that none of us would ever believe could be significant enough to make a perceivable difference. Whatever you believe, the fact is that you were always going to make that particular decision at that particular time. You may change your mind 10 seconds later, but you were always going to do that too.
3. The past and future don’t physically exist. Matter only exists in the present. If time travel is possible, it’s only through non-physical means (I’m only 99.9999999% sure that phychics are all full of shit). You may also be able to create the illusion of time travel to the future by putting your physical body into a temporarily static state, but you’ll never physically be able to wink in and out of existance at different points in time.
4. There may be some special start and end points to time where they’re just a Cause or just an Effect, but I think it may be more likely that time is circular and everything will just lead us back to the same point again. If there was a big bang to create our universe, then whatever ends it will cause another big bang (so points 1 & 2 still hold).
I stopped reading at 1. Time Exists…
The proof of this is that you can set your alarm clock?!!! Who invented the alarm clock? Mother nature? No, man invented it keep track of the sun. That doesn’t mean time exists. It’s another man made concept, most ignorant humans cant imagine a universe without themselves in it.
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In #1., the author stated “thank goodness”. Some might rather say “thank God” that time is not completely chaotic. For the brave among you, here is a related article that might bring some insight to the topic. Evolution Ex Nihilo.
EM wave(photon) have speed c which combines time and space(in 3D! Magnetic field direction,Electric field direction, and travel direction). Photon is the most/smallest fundamental particle. May Time come from that..?
I think #196 T, can be shown to be correct, And INSPIRED me to write up the following thoughts,
(related VIDEO ‘Do things ‘take time’ to move, or just move ?’
>> http://www.youtube.com/watch?v=WV3VjsY03Hk&t=1m4s)
PAGE >> https://sites.google.com/site/abriefhistoryoftimelessness/mathematics/what-do-clocks-measure
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(with respect) Sean’s first assumption ‘Time exists’ … setting alarm clocks proves it – can be seriously and logically questioned, e.g…
– The ability to create something we might call an alarm ‘clock’ may seem to confirm the existence and nature of ‘time – IF – we start with the assumption time exists*, but an ‘alarm clock’ does not necessarily prove the existence of ‘Time’ (with its flow, direction, Past and Future etc.)
(*just as if we watch a mind reading show with the ‘assumption’ that mind reading exists, are assumption may ‘seem to be confirmed’ – but we may still actually be mistaken).
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Consider making a large heavy mass, free to rotate on good bearings. We attach a small ‘arm’ so it sticks out from the mass at one location.
Then we set the mass spinning… any steady speed will do, but a speed matching the speed at which the Earth happens to rotate will be simplest… ( only for us here on Earth =)
With this set up one could place a ‘bell’ at any point around the spinning object, such that the protruding arm will strike and ring the bell where the two meet.
Now if for simplicity we do set the mas to spin at the same rate the Earth happens to be spinning at, then in Time terms, putting the bell 15 degrees on from where the protruding arm is will effectively make an alarm clock, which is set to go off in ‘one hour’.
But look from fundamentals what the set up actually shows and does not show.
-the spinning mass shows that objects can exist, rotate, and have inertia.
-that energy can be put into an object, and
-that energy is needed for objects to move
-the protruding arm shows that a moving thing can be heading for other things, (the bell in this case)
But the device does not prove that….
-as things move they leave or create a ‘temporal past’ behind them, or that
-ahead of moving things there is a ‘temporal future’, or that
-moving things head into a temporal future, or that
-a temporal future is constantly arriving, passing through an infinitely thin present, and into a ‘past’.
-or that, as well as ‘energy’ things also need a thing called ‘time’ to be existing and flowing.
This section might cause some irritation as you read it, but we should not assume that ‘If we are feeling irritated – this is a scientific proof that our currently held views are correct, and those views that irritate us are incorrect’. (in fact often the opposite is true ‘feeling irritated’ can be a sign that we are not being scientific).
Further more it is worth considering that the concept of an alarm clock may ‘seem to confirm’ the existence of time – if it is looked at ‘as if time exists’ – but if it is looked at as if ‘just matter and motion exist’ then this simpler* view will also seem to be confirmed.
note also that ‘seeming to confirm’ an assumption is not the same thing as proving an assumption from first principles, or direct observation.
*Simpler because it doesn’t call on the existence of an invisible past, invisible future, the ‘unpowered’ flow of an invisible thing called time – through an ‘infinitely thin’ present.
( See web link above for DIAGRAM.)
matt welcome