Julian Barbour - What is Time?

Time is a mystery; it's not what it seems. Time's flow feels unstoppable, yet some say time is not fundamental, perhaps not even real. Why do physicists and philosophers think time is a construct, something that emerges, not something that is basic?

[brunocoriolano]

“We live on an island surrounded by a sea of ignorance. As our island of knowledge grows, so does the shore of our ignorance.” ― John Archibald Wheeler

[WONKTI]

No physicist in the world today know for sure what "Time" is. However, some youtubers seems to have it all figured out.

[laonza]

What he says at 3:09 is truly the key.

[RalphDratman]

This is a most interesting, thoughtful exposition of "time" as a human construct with innumerable uses in our everyday world. It does not say much about time as the quintessentially mysterious foundation of theoretical physics.

[michaelpisciarino]

0:09 What is Time?
“A succession of pictures” continuously changing one into the other

We need a concept of change to hold a concept of time

0:59 Newton’s flow of time is wrong according to Barbour
2:00 You need change. Without it, you can’t say time has past.
2:58 Watches march in step not with Time, but with each other
3:36 Time, for practical purposes, is about keeping people synchronized, in about the same, common time

4:41 Refinements. Einstein showed the idea of absolute simultaneity is difficult at high speeds
5:24 Simultaneity at separate points.
6:07 We’ve reached a pleatu until Quantam Mechanics.

Atoms
6:49 Atomic Clocks, cesium atom.
7:35 Greater Accuracy requires Greater Care, Taking more variables in account

[bidoof]

Time is my mom yelling at me for hours

[dennisgalvin]

I'm a bit surprised with JBs comments about the deep rooted psychological experience of time moving forward and how he experiences it too. I thought with his viewpoint and all the research he's done on the subject that his perceptions would be free of that naivety.

[kevinheath]

If someone was in a black room couldn't see or hear or anything...fact nothing was happening...doesnt mean time was not passing. Hes wrong.

[GradyPhilpott]

All I can say is that this man's concept of time is exactly my concept of time and I'm just a guy who's been interested in the time and timekeeping for most of my life and while I do hold an advanced degree, none of my degrees have to do with physics. I came to my view of time by reading and studying on my own. And what is more impressive about Julian Barbour is that he makes his case in plain english.

[robb.]

I thought this was going to be the metaphysical interpretation of time, but it's time used as a practical measuring tool type of video.

[nevinsonlotterman]

My two favorite scientist that i like is Sir Isaac Newton and Albert Einstein

[williamesselman]

Even in an unchanging environment or when staring at a picture you have thoughts passing in your mind. As long as you have consciousness You couldn't possibly be unaware of the passing of time. Time is conscious awareness.

[mander]

I think time passes no matter what, you just need a frame of reference to prove it, just like you need a frame of reference for motion. The earth moves, but not from our frame of reference. Just an opinion, and probably an incomplete one.

[lovantigga]

Can't we define time as change in the arrangement of atom ?

[explorer-xert]

In response to - "It may be that time has passed but you just cant say." Julian replies - "I would prefer to put a name on something that I can see". That sounds like a very narrow view. Does that imply that when you are sleeping time is not passing?

[zeevkeane]

That’s a view of the world which relyes soley on mathematicall timelessness. Time is a dimension, rather a speed limit, preveneting the superimpossion of objects in the past, present, and future. The idea of it being a notion is purely stupid and frankly even if it wasnt stupid and is to be true there is nothing to gain by thinking of the world with such view.

[andrewk]

Are you serious? Discussing time and not even mentioning the 2nd law of therodynamics which defines the arrow of time. You may sync your watch or not but when they start ticking they only do so till their charge runs out, never do they accumulate charge no matter how you try. That is so fundamental a propery of time I have no idea how you missed that out

[deckard_]

I found the comments section far more interesting than the video which was lacking in meaningful information.

[spactick]

I love the way this guy talks. You can see in his eyes that he's not really convinced that what he's saying is in fact the absolute
truth, but he's trying to be as honest as he can be given his position of trying to satisfy the interviewers quest for an answer

[eXtremeDR]

If time is motion then time doesn't exist where no motion is. Motion creates heat - thus when there is no heat then there is no motion and no time. WOOT! My freezer is a time-machine! ^^