I was looking at:

Is there really a direction of time?

which is yet another question related to the flow of time, and I was thinking that it would be nice to have a master Flow of Time question that we could direct people to. I don't think such a question exists. Searching the site I find the following popular questions:

as well of dozens of related questions with fewer upvotes. I think these questions pretty much cover the ground between them, and I was wondering if it would be useful to write a grand unified question that grouped all the information in one place. Obviously there would be duplication of existing material, but I think it would be worth it. I'm willing to have a go at writing a question and answer, but it would be Community Wiki so anyone can contribute.

Opinions please. Upvote if you want someone to write this question and downvote if you don't want to see this question posted.

  • 2
    $\begingroup$ In my opinion, the master flow of time question should also made a distinction between the concepts of "the arrow of time" (talk about the asymmetry of a process wrt t symmetry) and "the flow of time" (the subjective experience that time seemed to elapse continuously) since a lot of people tend to confuse the two $\endgroup$
    – Secret
    Commented Jan 15, 2016 at 9:33
  • 1
    $\begingroup$ +1 from me; I do agree with you; there have been such questions coming now and then and it would be great to guide them to a general master flow of time question. But also there must be a sharp distinction between the philosophy associated with it and the concerned material(s). Also, agree with Secret. $\endgroup$
    – user36790
    Commented Jan 15, 2016 at 9:50
  • 3
    $\begingroup$ Echoing some of the other comments: There seems to be two different types of questions here: 1. What is time exactly in physics? 2. What is the arrow of time in statistical physics? The new question belongs to the second type while John Rennie's examples belong to the first type. $\endgroup$
    – Qmechanic Mod
    Commented Jan 15, 2016 at 11:55
  • $\begingroup$ I have to say that the "nature of time" is one of those subjects that attracts a lot of ... um ... non-standard consideration. So, while I don't object to trying to build one or more master questions on the actual physics issues at play with time, I don't really think they'll help much. $\endgroup$ Commented Jan 15, 2016 at 18:20
  • $\begingroup$ While this is a great topic, I'm confused why there aren't more calls for canonical answers for much, much more common questions. Questions of the type 'why does double slit mumble', 'how mumble twin paradox', 'planck length mumble discreteness', 'EPR mumble faster than light', 'measuring mumble violating heisenberg', etc. are all at least an order of magnitude (or two!) more common. $\endgroup$
    – knzhou
    Commented Jan 16, 2016 at 5:59
  • $\begingroup$ My impression is that this site's very high rep users are tired of answering such questions, but they're the ones that need canonical answers most. $\endgroup$
    – knzhou
    Commented Jan 16, 2016 at 6:00
  • $\begingroup$ I like it. Wouldn't surprise me if it ended up being transferred to Skeptics, though.. $\endgroup$
    – tjt263
    Commented Jan 16, 2016 at 18:46
  • $\begingroup$ @knzhou There has been: meta.physics.stackexchange.com/q/6060 $\endgroup$
    – tpg2114
    Commented Jan 17, 2016 at 1:14
  • $\begingroup$ And another call for a specific question: meta.physics.stackexchange.com/q/7266 $\endgroup$
    – tpg2114
    Commented Jan 17, 2016 at 1:16
  • 4
    $\begingroup$ At the time of writing there are eight upvotes and no downvotes so I conclude no-one thinks this is a terrible idea but enthusiasm for it is muted. If I can get the time I'll have a go at writing the canonical Q/A but if anyone else wants to beat me to it please go ahead. As the title how about What is time, does it flow, and if so what defines its direction? $\endgroup$ Commented Jan 17, 2016 at 11:05
  • $\begingroup$ The trouble with "canonical" answers is that they're sometimes wrong. Remember that science is not a democracy: votes don't make an answer right. Evidence does. And the evidence days time is a cumulative measure of motion, it doesn't actually flow, it isn't something you can literally travel through, and it doesn't have a direction in any real sense. Light moves, things change, entropy tends to increase, and people then talk of "the arrow of time", But this is an abstract concept. You could just as well talk about the arrow of evolution. But anyway, I'd be interested in seeing your efforts. $\endgroup$ Commented Jan 22, 2016 at 15:11
  • $\begingroup$ read through your answers on this particular question along with the time dilation and the twin paradox ones..have to say that you did a great job...thanks for your contributions.. $\endgroup$
    – Bruce Lee
    Commented Mar 9, 2016 at 0:18

1 Answer 1


Right, the first draft is now at:

What is time, does it flow, and if so what defines its direction?

All comments welcome!


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .