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What Is Time? One Researcher Shares His Exploration

ScuttleMonkey posted more than 4 years ago | from the what-about-the-underverse dept.

Science 578

Physicist Sean Carroll has built up a bit of a name for himself by tackling one of the age old questions that no one has been able to fully explain: What is time? Earlier this month he gave an interview with Wired where he tried to explain his theories in layman's terms. "I’m trying to understand how time works. And that’s a huge question that has lots of different aspects to it. A lot of them go back to Einstein and spacetime and how we measure time using clocks. But the particular aspect of time that I’m interested in is the arrow of time: the fact that the past is different from the future. We remember the past but we don’t remember the future. There are irreversible processes. There are things that happen, like you turn an egg into an omelet, but you can’t turn an omelet into an egg."

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Timeline (1, Interesting)

sopssa (1498795) | more than 4 years ago | (#31291534)

We remember the past but we don’t remember the future.

In a way you can "remember" future, it's called deja vu. The few times I've had it, everything matched perfectly what I already knew. I knew what was going to happen and what there was around me and what was different than how it usually is, ie. what items were in different location or not there. Like most people, I attributed it to a past dream. I am certain it didn't happen before in reality nor was it some anomaly from memory.

This leads me to believe there is a timeline. Everything happening all the time has a position and state on that timeline. We try to explain time with physics and our current knowledge. This is somewhat related to physics - if you're moving faster, you're aging slower (your time is going slower). This is true on airplanes and true when moving at light speed. If you moved fast enough, everyone on Earth could age 70 years while you only aged a few minutes.

But this only works towards future. Nevertheless, if it works towards future it must also work towards past. I think the plain movement speed isn't what's causing the differences in passing time, but it triggers something else. We as humans have (admittedly bad) memory of everything that has happened in the past. There is our own state and time. Why there couldn't be global state and time, a timeline? A timeline you could warp within, even if you did exactly the same things again.

Re:Timeline (5, Funny)

spiffmastercow (1001386) | more than 4 years ago | (#31291606)

You're either a Philosophy student, or you just watched Donnie Darko for the first time, right?

Re:Timeline (2, Informative)

Anonymous Coward | more than 4 years ago | (#31291630)

Timecubist, most likely. [timecube.com] Just wait 'til he watches Primer.

Re:Timeline (1)

pushing-robot (1037830) | more than 4 years ago | (#31291658)

That's better than what I was picturing, which is that he's posting on Slashdot while bare-ass naked and a bright shade of blue.

Invoking Occam (1)

srussia (884021) | more than 4 years ago | (#31292022)

You're either a Philosophy student, or you just watched Donnie Darko for the first time, right?

This is Slashdot. This must be a dupe.

Re:Timeline (5, Insightful)

BitZtream (692029) | more than 4 years ago | (#31291660)

Except ... medical studies show that 'Deja Vu' is really just brain glitches that are nothing more than thinking after the fact that you knew it was going to work that way. You're having a minor seizure, not predicting the future.

Re:Timeline (1)

macaulay805 (823467) | more than 4 years ago | (#31291884)

My personal problem with that text (as I actually had a conversation about this very topic the other day), is how about when my brain "glitches" and shows me things that happen well* in advance. *Well meaning years in advance.

Re:Timeline (2, Insightful)

maxume (22995) | more than 4 years ago | (#31291998)

Stuff that you remember, or stuff that you wrote down?

You can't trust your brain.

Re:Timeline (1)

twidarkling (1537077) | more than 4 years ago | (#31291890)

I knew Deja Vu is just the movement of memory directly to long-term, rather than residing in short-term first, but is it really a minor seizure? Because that shit happens to me a couple times a year. I should get checked out if it's seizing.

Re:Timeline (1)

dave562 (969951) | more than 4 years ago | (#31292028)

How do you explain when it doesn't happen after the fact? For example there are times when I have a second or two advance warning. I know exactly what someone is going to say, and then they say it. I never know more than a few words, but I know exactly what those few words will be.

Re:Timeline (3, Interesting)

TheCouchPotatoFamine (628797) | more than 4 years ago | (#31291662)

nope, your referring to prediction - not prescience - something that neural networks, such as the ones in your head - are very good at.

if you'd like to explore a real philosophical issue, consider whether or not you, as a neural network world-predictor, could ever experience anything truly random? Pretty much, no, your mind cannot refuse to map patterns, even if your senses pick up something that has no pattern at all, since your brain is just so wired to the gills to put a pattern on EVERYTHING.

Re:Timeline (1)

snowraver1 (1052510) | more than 4 years ago | (#31291680)

I think that deja vu is a memory anomoly or something odd with chemicals in the brain... I get a deja vu about once per year (it seemed more common when I was a kid... Just me??) and it is a very stong feeling of knowing what will happen. It feels like I could announce to the room that some action would happen, but I have never actually been able to do it... It seems like it is just on the tip of the tounge, but just out of reach. Has anyone been able to announce a reasonaby random event before it happened while experiencing a deja vu? Something like "Bob will walk in though that door now" or "Bob is going to spill his drink".

Re:Timeline (5, Insightful)

bill_mcgonigle (4333) | more than 4 years ago | (#31291846)

It seems like it is just on the tip of the tounge, but just out of reach. Has anyone been able to announce a reasonaby random event before it happened while experiencing a deja vu? Something like "Bob will walk in though that door now" or "Bob is going to spill his drink".

No, they can't because it's an illusion. Your brain gets into a tight sensing/remembering loop for a short time, so it seems like you're recalling stuff that just happened, but it's the other way around. You're not used to that, so it's confusing and easily misinterpreted.

There's no more reason to be embarrassed by this than being fooled by optical illusions (happening in your visual cortex, not your eye in many instances) - our brains aren't perfect arbiters of the physical world, they interpolate quite a bit, so occasionally they get tripped up. This imperfection lets us laugh at Penn & Teller - it's all good.

Besides, we already know that memories are chemically encoded, so the only way to have memories of the future is magically putting chemical patterns in your brain. And between 'magic' and 'brain fart' - well, apply Occam's Razor.

Re:Timeline (3, Interesting)

snowraver1 (1052510) | more than 4 years ago | (#31291944)

Has anyone else noticed a decrease in the frequency of deja vu as they get older? I think that the peak was when I was about 13-14. Just curious....

Re:Timeline (1)

timeOday (582209) | more than 4 years ago | (#31291964)

The strongest deja vu I ever had was right after hitting my head in a sledding accident.

Re:Timeline (-1, Troll)

Anonymous Coward | more than 4 years ago | (#31291704)

You're about to have another deja vu. Your nickname backwards reads ASS P.O.S. and it's a true description of what you are.

Re:Timeline (1)

Monkeedude1212 (1560403) | more than 4 years ago | (#31291706)

But this only works towards future. Nevertheless, if it works towards future it must also work towards past.

This is where you lost me. How did you arrive at that conclusoin? Most people would say that what happens in our timeline are heading in one direction and can't be reversed. The cooking of an egg, the stirring of sugar into water, no matter how much you stir that water or "unheat" that egg is it ever going to return to its original state. You drop a glass and it shatters. No matter how much you put the pieces back together, it is still broken until you apply some force that wasn't in the original occaison.

I think the plain movement speed isn't what's causing the differences in passing time, but it triggers something else. We as humans have (admittedly bad) memory of everything that has happened in the past.

We have pretty good memory, or so I like to think. You ask me where I was a month ago, I could work it out and tell you. You tell me where I was last year, it'd take longer, and perhaps conversing with someone else would jog my memory. Point is its all in there, and some people have freakishly good photographic memory.

There is our own state and time. Why there couldn't be global state and time, a timeline? A timeline you could warp within, even if you did exactly the same things again.

Okay you lost me again. I think you are trying to wonder why something like what you describe couldn't happen if time were capable of flowing both ways? But all evidence we have produced so far counters that.

Re:Timeline (1)

Arthur Grumbine (1086397) | more than 4 years ago | (#31291994)

But this only works towards future. Nevertheless, if it works towards future it must also work towards past.

This is where you lost me. How did you arrive at that conclusoin?

I'm pretty sure he started at where he wanted to be and worked backwards. A perfect example of "begging the question".

Re:Timeline (0)

Anonymous Coward | more than 4 years ago | (#31291734)

Did the acknowledgement of events come before or after the events? Typically, deja vu, something happens and you "remember it" as already knowing or having experienced it right? Well that's all chemical. It's the brain "mislabelleing" stuff it's recording/storing as memories.

Unless you were able to actually sit there and EXPECT events before they happened, then it's certainly not what you are claiming. It's just brain chemicals causing feelings that are wrong.

Re:Timeline (2, Interesting)

MRe_nl (306212) | more than 4 years ago | (#31291784)

The sensation of deja vu is (simply put) caused by a millisecond shutdown of a part of your memory, and the reloading of that part of your memory afterwards. This happens so fast you'll never notice but for that strange sensation of having seen/been there before. You have actually seen it before: one millisecond ago.

Re:Timeline (1)

timmarhy (659436) | more than 4 years ago | (#31291792)

is the speed you move at really related to biological aging though? i've always been dubious of this assertion, just because my mass is moving faster in relation to everything else why would my cells stop multiplying, and hence aging.(if we could get around them being crush by the force of accelerating to near light speed). it'd be very interesting to see any kind of testing of the effects of relativity on biology.

why do we know the reverse wouldn't be true? if you wizzed someone off for 70 years at light speed, the .0001 of a second it would seem to them wouldn't age them instantly? i'm genunily interested.

Re:Timeline (1)

Monkeedude1212 (1560403) | more than 4 years ago | (#31291894)

You are misunderstanding the concepts - its not that your cells are multiplying less fast, its that your atoms and molecules themselves are moving at a different reference of time.

It's hard to explain without having prior knowledge. Just know that we've observed this change in action - a satellite in orbit will read 1:00 and so will a clock on Earth. However after a long amount of time, the satellite will be a minute behind.

I'd get into the nitty gritty of it, but I don't have time. You should google "Fabric of Space-time" and blow your mind.

Re:Timeline (1)

marcansoft (727665) | more than 4 years ago | (#31291904)

You're thinking of time dilation as being related to your "brain clock" or the way your brain recognizes time. It isn't. Time itself is relative, and it works at a level below body chemistry. If you're traveling at near light speed, time will appear to pass normally to you (and to your cells, and to a digital clock that you're carrying, and to anything else with you), but in fact external observers will appear to age faster. To them, you're aging slowly and they're aging normally.

The key word is time. The progression of time itself changes, not the time it takes for biological processes to happen. One second is still one second, and the same things happen to you in one second as they would otherwise, it's just that your second isn't equal to the outside world's second.

Re:Timeline (1)

Toonol (1057698) | more than 4 years ago | (#31291810)

In a way you can "remember" future, it's called deja vu. The few times I've had it, everything matched perfectly what I already knew.

You think the simplest explanation for the feeling of deja vu is some sort of psychic echoes from future events?

Hmm... I feel like I've had this conversation before... in high school...

Time (5, Funny)

Anonymous Coward | more than 4 years ago | (#31291560)

About half past ten, give or take a couple of minutes.

Re:Time (2, Funny)

Edward Teach (11577) | more than 4 years ago | (#31291676)

LOL, posted at 2:33.

Re:Time (5, Funny)

Anonymous Coward | more than 4 years ago | (#31291722)

LOL, posted at 2:33.

Edward Teach meet Time Zones [wikipedia.org] . Times Zones, Edward.

Re:Time (-1, Flamebait)

Edward Teach (11577) | more than 4 years ago | (#31291788)

Anonymous Coward, meet the concept of humor: http://en.wikipedia.org/wiki/Humour [wikipedia.org]

Re:Time (5, Funny)

Anonymous Coward | more than 4 years ago | (#31291836)

Maybe you need to study the concept more.

Re:Time (2, Funny)

JustOK (667959) | more than 4 years ago | (#31291854)

Eddies in the space time continuum?

Re:Time (4, Funny)

twidarkling (1537077) | more than 4 years ago | (#31291924)

Well get him out, then. We just cleaned it.

Re:Time (1)

zoomosis (169771) | more than 4 years ago | (#31291932)

He certainly is.

Re:Time (1)

WrongSizeGlass (838941) | more than 4 years ago | (#31291678)

If you're having trouble telling what time it is you can always build the retro-clock from this article [slashdot.org] .

Re:Time (2, Funny)

Monkey_Genius (669908) | more than 4 years ago | (#31292026)

Twenty-Five or Six to Four?

What Is Time? (3, Insightful)

negRo_slim (636783) | more than 4 years ago | (#31291566)

Entropy

Re:What Is Time? (3, Informative)

Jorl17 (1716772) | more than 4 years ago | (#31291736)

Money

Re:What Is Time? (3, Interesting)

N7DR (536428) | more than 4 years ago | (#31291804)

As Einstein famously said: "Time is what a clock reads". I always thought that was rather a clever evasion: true but not particularly helpful.

For many years that quotation was on a poster that greeted one in the lobby of what was then the National Bureau of Standards in Boulder, CO.

Re:What Is Time? (0)

Anonymous Coward | more than 4 years ago | (#31291992)

And clocks are just entropy meters.

Re:What Is Time? (1)

buruonbrails (1247370) | more than 4 years ago | (#31291866)

Entropy shows us the direction of time. Lower entropy than now means past, higher entropy means future. However, if entropy ever reaches maximal level (thermodeath of the Universe), then this measure of time won't be usable any more.

Um, neither will anything else. (1)

aussersterne (212916) | more than 4 years ago | (#31291910)

It will be, quite literally in every sense of the phrase, the end of time.

Or antimatter (5, Insightful)

mangu (126918) | more than 4 years ago | (#31291880)

Thermodynamics is one of two sets of phenomena that are irreversible. The other [wikipedia.org] is rather obscure, but is related to the fact that "ordinary" matter seems to be so much more abundant in our universe than anti-matter.

All other phenomena in our universe are reversible in time, which raises an interesting question: are we unable to see the future because our brains work on thermodynamic operations?

Not only biologic brains, but digital computers also depend on non-reversible operations. A two-input AND gate has a "0" output in three different input conditions: "00", "01", and "10". Now imagine a computer that uses a reversible logic system that is reversible, would that computer have a time-symmetric operation?

Re:What Is Time? (0)

Anonymous Coward | more than 4 years ago | (#31291916)

Hawkingthoughtthatthearrowoftimewasjustan effect of entropy.Maybehewasright,ormaybethatwillturnouttobeanevasion.Butitdoesn'tanswerwhattimeis.

Re:What Is Time? (1)

snooo53 (663796) | more than 4 years ago | (#31292020)

You know, usually I get really irritated tongue-in-cheek answers, but yours fits the article perfectly (of which reading was a big waste of time IMHO).

Time is the goo... (3, Informative)

gestalt_n_pepper (991155) | more than 4 years ago | (#31291568)

that connects state one to state two.

Re:Time is the goo... (1)

debrain (29228) | more than 4 years ago | (#31291698)

Time is the goo ... that connects state one to state two.

Goo made up of units of the shortest appreciable differences in states.

Re:Time is the goo... (1)

gestalt_n_pepper (991155) | more than 4 years ago | (#31291808)

1 unit goo = planck? Seems too large to me.

Easy (4, Funny)

Yvan256 (722131) | more than 4 years ago | (#31291582)

FORD: No, No listen. Just imagine that you’ve got this ebony bath, right? And it’s conical.

ARTHUR: Conical? What kind of bath is -

FORD: No, no, shh, shhh, it’s, it’s, it’s conical okay? So what you do, you fill it with fine white sand right? Or sugar, or anything like that. And when it’s full, you pull the plug out and it all just twirls down out of the plug hole but the thing is

ARTHUR: Why?

FORD: No, the clever thing is that you film it happening. You get a movie camera from somewhere and actually film it. But then you thread the film in the projector backwards.

ARTHUR: Backwards?

FORD: Yeah, neat you see. So what happens is you sit and you watch it and then everything appears to swirl upwards, out of the plug hole and fill the bath amazing.

ARTHUR: And that’s how the universe began?

FORD: No. But it’s a marvellous way to relax.

TRILLIAN: Funny man.

FORD: Well it broke the ice didn’t it?

Re:Easy (1)

Volante3192 (953645) | more than 4 years ago | (#31291632)

If only Harrod's wasn't destroyed we could've gotten an ebony conical bath to try that with.

Re:Easy (3, Funny)

Anonymous Coward | more than 4 years ago | (#31291638)

FORD: Time is an illusion. Lunchtime, doubly so. ARTHUR: Deep. Very deep. They have a page at the Readers' Digest for people like you.

[...]you can't turn an omelet into an egg. (4, Insightful)

snowraver1 (1052510) | more than 4 years ago | (#31291620)

Maybe not directly, but you can feed that omelet to a chicken, and then take the resulting egg.

Re:[...]you can't turn an omelet into an egg. (1)

hackerman (1649305) | more than 4 years ago | (#31291796)

that's awful!

Re:[...]you can't turn an omelet into an egg. (2, Funny)

Anonymous Coward | more than 4 years ago | (#31291852)

actually, its fowl

Re:[...]you can't turn an omelet into an egg. (2, Funny)

JustOK (667959) | more than 4 years ago | (#31291882)

it's just one of his yolks, although he might have poached it.

Re:[...]you can't turn an omelet into an egg. (4, Funny)

JustOK (667959) | more than 4 years ago | (#31291868)

automate it with a shell script

Re:[...]you can't turn an omelet into an egg. (0)

Anonymous Coward | more than 4 years ago | (#31291988)

Ah yeah, the typical slashdot asperger response, seeing a simple explanation and taking it literally, all while feeling smug and good about himself. "Yeah, that really showed him, and I have my fellow asperger friends to back me up with their moderation! Another friday well spent!"

Re:[...]you can't turn an omelet into an egg. (3, Insightful)

timeOday (582209) | more than 4 years ago | (#31292016)

Maybe not directly, but you can feed that omelet to a chicken, and then take the resulting egg.

But the chicken produces fewer eggs than you feed it. Not just "not more", but "fewer."

Re:[...]you can't turn an omelet into an egg. (0)

Anonymous Coward | more than 4 years ago | (#31292018)

you could then test what the efficiency is of the egg->chicken->egg cycle.

But... (4, Insightful)

Black Parrot (19622) | more than 4 years ago | (#31291648)

We remember the past but we don't remember the future. There are irreversible processes. There are things that happen, like you turn an egg into an omelet, but you can't turn an omelet into an egg.

But if time is non-monotonic, wouldn't we un-remember, un-break things, during the backturns?

How would anyone know if time isn't always forward?

What Is Time? (5, Interesting)

Monkey_Genius (669908) | more than 4 years ago | (#31291652)

Time is an artificial construct of the Human mind that allows us to mark our pitiful existence in an uncaring universe.

Re:What Is Time? (4, Interesting)

Toonol (1057698) | more than 4 years ago | (#31291872)

Time is an artificial construct of the Human mind that allows us to mark our pitiful existence in an uncaring universe.

Not far from the truth, but I'd say it is an "amazing creation of evolution" that allows us to "experience the unfurling glory of our life in a rich universe."

Re:What Is Time? (1)

BradleyUffner (103496) | more than 4 years ago | (#31291950)

Time is an artificial construct of the Human mind that allows us to mark our pitiful existence in an uncaring universe.

I tend to agree with you, but it brings up the question of why the effects of time are different on an observer in motion compared to one at rest.

easy (1)

Michael Kristopeit (1751814) | more than 4 years ago | (#31291672)

time is the bi-product of change

Re:easy (0)

Anonymous Coward | more than 4 years ago | (#31291844)

But then why do things change? And why is the rate of change here the same as in a galaxy far far away? There must then be a more fundamental clock that regulates the rate of change.

Re:easy (1)

Michael Kristopeit (1751814) | more than 4 years ago | (#31291970)

There must then be a more fundamental clock that regulates the rate of change.

must? what if the change itself was regulating our perception of time? the article might as well be entitled "what is god?"... all speculation that 50% of people will disagree with.

Re:easy (1)

twidarkling (1537077) | more than 4 years ago | (#31291962)

Wrong. Time isn't bi! It doesn't go both ways.

Time? (2, Insightful)

daffey (1726862) | more than 4 years ago | (#31291728)

A physicist I'm not, nor mathematician, but 'TIME is CHANGE' in my book. No change- no time. What else can you measure it against?

Re:Time? (3, Informative)

Monkeedude1212 (1560403) | more than 4 years ago | (#31291830)

What else can you measure time against, or what else can you measure change against? Because you can measure a change in distance, a change in volume, a change in temperature, the list goes on.

As for measuring time - you can have instances where nothing changes BUT the time - so thus begs the question, what is time if nothing changes?

Imagine a single Molecule, Well if you can imagine it moving you know it has speed and then you just take the change in distance to find the amount of time that had passed.

Well, imagine if it didn't have a speed - it wasn't moving. How would you calculate the change in time?

Re:Time? (1)

Toonol (1057698) | more than 4 years ago | (#31291928)

I think that is part of the issue, but there's more problems:

Change is measured over time. An accelerating change means that more change is happening per time; that means that time is somehow independent of change.

Also... change happens go forward through time, going backward through time. If you see two atoms collide, the process works forward and backward... but time only seems to go forward. Why does time seem to only exist in one direction?

It seems to tie heavily into thermodynamics (and, hence, evolution). Individual particles behave almost independently of time, but large systems seem to statistically indicate a strong temporal directionality.

My head hurts.... (1)

L3370 (1421413) | more than 4 years ago | (#31291738)

"We remember the past but we don’t remember the future. There are irreversible processes"

I am in NO WAY qualified to argue on the subject, but the quoted statement seems like a problem with words and definitions. You can't 'remember' the future because the word 'remember' doesn't apply very well to the word (or usage of the word) 'future.'

I'll probably be blasted out to hell by an expert in 3...2...1...

Re:My head hurts.... (0)

Anonymous Coward | more than 4 years ago | (#31292010)

Good point. One can also not "predict the past". By definition. And not "by definition of the physical axioms that rule our universe" but "by definition of the word 'predict' in the dictionary".

Why that's easy! (1)

Dunbal (464142) | more than 4 years ago | (#31291752)

v = s/t therefore vt = s therefore t - s/v: Time is simply distance over velocity!

Honestly it's all very well to swindl^H^H^H^H convince people to give you grant money by investigating "time". I mean, the prospects of having one's very own time machine are incredible.

Yet one has to ask, (and this is where tenses get complicated, I will resort to the Douglas Adams trans-temporal convention) if anything practical wioll have come from such a study, we would have been receiving visitors from "the future" for a long time now! Heck, wars and genocides could have been prevented as far back as ancient Egypt. In fact, human nature being what it is, history will would have become pretty boring...

Re:Why that's easy! (1)

Eudial (590661) | more than 4 years ago | (#31291818)

v = s/t therefore vt = s therefore t - s/v: Time is simply distance over velocity!

Distance between what, and velocity of what? What about stationary objects?

Re:Why that's easy! (1)

mb_96_net (962371) | more than 4 years ago | (#31292000)

The building blocks (electrons, protons or quarks even) of stationary objects still have motion. Maybe anything that has a temperature greater than absolute zero experiences time because it is in motion.

Re:Why that's easy! (1)

Toonol (1057698) | more than 4 years ago | (#31292044)

You're not very intellectually curious. Studying time doesn't mean your goal is to make a time machine, any more than studying gravity means you want to create an antigravity gun.

Why do you think time shouldn't be studied, when so many other fundamental attributes of our universe should be? It seems you think time possesses some magically unknowable characteristics. Defining it as distance over velocity is as simplistic as defining mass as density times volume, and thinking that explains anything.

An old co-worker once told me.. (0)

Anonymous Coward | more than 4 years ago | (#31291758)

Time is our word for every dimension that exists besides the first three... not sure how many there are though.

Humpty Dumpty (1)

mosb1000 (710161) | more than 4 years ago | (#31291760)

Humpty Dumpty sat on a wall,
Humpty Dumpty had a great fall.
All the king's horses and all the king's men
Couldn't put Humpty together again.

A more apt question is this: What is Entropy [wikipedia.org] ?

Time Travel (5, Funny)

Citizen of Earth (569446) | more than 4 years ago | (#31291766)

Hello. I am a time traveler. Be not afraid. I come from the past and I travel into the future at a rate of one second per second.

St Augustine already figured it out: (4, Insightful)

joebok (457904) | more than 4 years ago | (#31291794)

From St. Augustine's Confessions, Book XI:

CHAP. XIV. -- NEITHER TIME PAST NOR FUTURE, BUT THE PRESENT ONLY, REALLY IS.

17. At no time, therefore, hadst Thou not made anything, because Thou hadst made time itself. And no times are co-eternal with Thee, because Thou remainest for ever; but should these continue, they would not be times. For what is time? Who can easily and briefly explain it? Who even in thought can comprehend it, even to the pronouncing of a word concerning it? But what in speaking do we refer to more familiarly and knowingly than time? And certainly we understand when we speak of it; we understand also when we hear it spoken of by another. What, then, is time? If no one ask of me, I know; if I wish to explain to him who asks, I know not. Yet I say with confidence, that I know that if nothing passed away, there would not be past time; and if nothing were coming, there would not be future time; and if nothing were, there would not be present time. Those two times, therefore, past and future, how are they, when even the past now is not; and the future is not as yet? But should the present be always present, and should it not pass into time past, time truly it could not be, but eternity. If, then, time present -- if it be time -- only comes into existence because it passes into time past, how do we say that even this is, whose cause of being is that it shall not be -- namely, so that we cannot truly say that time is, unless because it tends not to be?

Re:St Augustine already figured it out: (1)

aBaldrich (1692238) | more than 4 years ago | (#31291922)

My philosophy teacher told me something that blew my mind: Past is a non-being, because it ceased to exist. Future is a non-being, because it does not exist yet. Present lies between two non-beings. Therefore it does not exist.
I think that "time" is one of the most strange, even spiritual things there are. Can we demonstrate it exists? Can we falsify it? Everyone discusses causality and non-contradiction. Time is probably one of the most underrated axioms of human knowledge.

Re:St Augustine already figured it out: (1)

Tomfrh (719891) | more than 4 years ago | (#31291958)

Maybe, but a lot physicists seem very keen on eternalist interpretations of time in which every instant is just as real as any other.

I think (1)

Token_Internet_Girl (1131287) | more than 4 years ago | (#31291800)

We spend too much time on the subject of time. How can we really ever know the true nature of time if we are limited by our perception of it as human beings? All we can see is the Entropic version of time this guy discussed; things are in state one, the state changes with chemical reactions and energy release, then they are in an irreversible state. Time is a byproduct of this basic law of Thermodynamics. Personally I'm of the mind that the true nature of the universe eludes it because there are forces or concepts we are yet incapable of perceiving. But I'm only a novice in Physics, I could be wrong.

Re:I think (1)

sconeu (64226) | more than 4 years ago | (#31291832)

Indeed. What he's really researching is the Second Law.

ObSimpsons: Lisa, in this house, we obey the Laws of Thermodynamics!!!!

Wrong. (0)

Anonymous Coward | more than 4 years ago | (#31291848)

There is no past, there is no future, there is only the present.

Re:Wrong. (1)

bill_mcgonigle (4333) | more than 4 years ago | (#31291966)

There is no past, there is no future, there is only the present.

absolute metaphysical certitude?

My Theory (1)

macaulay805 (823467) | more than 4 years ago | (#31291856)

Which I came up with so long ago is: Time is a measurement of location and actions.
Location: The relative point you were at in space, includes local (Earth) and/or celestial location.
Actions: What you were doing at the time.

In history, we measure where we were and what we were doing.
In present, where we are now and what we're doing.
In future, where we will be and what we will be doing.

Not a measurement of, but a tool for (1)

aussersterne (212916) | more than 4 years ago | (#31291968)

synchronizing location and actions. Time allows members of society to harness shared cognitive storage capabilities in the interest of collaboration and synchronization, which allows humans to produce the incredibly complex world that we have produced.

Making fire burn backwards (1)

handy_vandal (606174) | more than 4 years ago | (#31291870)

Larry Niven wrote that "A man who can make fire burn backwards is mighty wizard indeed", or words to that effect. One of his short stories, I forget which.

Time flies like an arrow; (0)

Anonymous Coward | more than 4 years ago | (#31291892)

fruit flies like a banana.

Not that it makes sense (1)

T Murphy (1054674) | more than 4 years ago | (#31291908)

I just took a linear algebra course, and to perform a translation on a matrix (each column is a coordinate set, each row is x, y or z coordinates), you first add a dimension, and multiply your matrix by an identity matrix with the wanted translation in the extra dimension. In other words, to move stuff using matrix multiplication, you have to add a dimension. It makes no physical sense, but it is interesting to think of time as this added dimension simply facilitating movement.

As for the math I am talking about, I can't format it nicely, but translating by (5,6) looks like this:

Format is [[row 1],[row 2],[row 3]]:
A=[[2 3],[4 5]]
A'=[[2 3 0],[4 5 0],[0 0 1]]
T=[[1 0 5],[0 1 6], [0 0 1]]
A'(translated)=T*A'
A'(translated)=[[7 8 0],[10 11 0],[0 0 1]]

Order to chaos (1)

dandart (1274360) | more than 4 years ago | (#31291912)

The direction of time is order to chaos (with a few exceptions). The universe is more chaotic than it used to be, but with packets of order.

Fundamentally, it takes a little energy to turn order to chaos but a lot of energy to turn chaos to order. Like breaking an egg, or thermodynamic laws (energy moving from hot objects to cold objects, due to hot objects having more entropy).

Fred Hoyle would be pleased (1)

MichaelSmith (789609) | more than 4 years ago | (#31291920)

This sounds like the steady state theory. Back then Hoyle was pushing it the idea was that mass comes from nowhere continuously. In this idea entropy just appears in a quiet universe for no reason.

Time does not exist (4, Insightful)

afabbro (33948) | more than 4 years ago | (#31291948)

Prove me wrong.

The future obviously does not exist. The past? Doesn't exist either. Hence, only this present moment exists.

You can't even prove that the past existed. The only thing we have is present-moment memories, etc. I remember typing "Prove me wrong" but my memory is hardly reliable. If thirty seconds ago you spilled milk on your pants, all you have now is wet, soggy pants, not any "chain of events". Even if you filmed it, all you have is the present-moment series of images, not some actual piece of the past.

Only this present moment exists. All else is wild speculation and fantasy. Time does not exist.

The simple answer (1, Funny)

Anonymous Coward | more than 4 years ago | (#31291952)

Time is what you are wasting right now.

What is time? (0)

Anonymous Coward | more than 4 years ago | (#31291974)

Baby don't hurt me... Don't hurt me... no more...

time has no arrow, spacetime does (2, Insightful)

sweetser (148397) | more than 4 years ago | (#31291986)

Hello:

Time will never have an arrow. Spacetime will, from the space part. If you take Minkowski's advice, that one should only think about spacetime, not time or space, then Carroll's question is poorly formed. It is good English, bad mathematical physics. Since Minkowski's observation was based on work with special relativity, people presume is observation applies only for relativistic systems. Sorry, Nature is more consistent than that: one needs to think about spacetime always, even if it contributes squat. Newton's 2nd law can be written F = m (d/dt. 0, 0, 0)^2 (0, x, y, z). What makes it classical are all the zeroes that appear in the spacetime operators.The handedness of times arrow comes from the space part whose contributions are stupidly small, but add up enough of them, and they are irreversible.

1 X per 100(0) yr. events happening daily now (0)

Anonymous Coward | more than 4 years ago | (#31292002)

you do the math. time is what we have (yet another gift) here, &/or hereafter.

Ask Dr Soran! (1)

sajuuk (1371145) | more than 4 years ago | (#31292024)

Time is the fire in which we burn...

Islamic view of "time" (1, Interesting)

Chicken_Kickers (1062164) | more than 4 years ago | (#31292036)

The Islamic view of time and the universe in general is that what has happened, is happening and will happen has already been determined ("it is written"). What has happened can never be undone and this is mentioned many-many times in the Quran. This means that time travel is impossible. In fact, the belief in fate and predestination and accepting the outcome whether good or bad, is one of the core of iman or Belief. What is happening and what will happen also cannot be avoided. To some extent, mankind has the ability of self determination on the small scale but in the larger scheme of things, God had determined everything. For example, the time of death for a person is already determined(though we will not know it) even before birth and mankind could not avoid or add or subtract even 1 second to this. Similarly, the time of Qiamat or Armageddon where the entire universe will fold upon itself is also already determined. Many Muslim scholars have dwelt on this subject, particularly its impact on the concept of sin and reward. The Prophet Muhammad actually discourages too much dwelling on this matter because human minds could not fathom the will of God. God is not some bearded Caucasian with long hair and wearing a white robe. God exist outside of time and the universe and thus is unfathomable. "He" is nothing that any human mind could ever imagine or grasp any more than a bacterium in a petri dish could grasp the concept of a sentient human being.

Time travel to the past and Uncle Rico moments. (1)

t0qer (230538) | more than 4 years ago | (#31292040)

Some of you may remember Uncle Rico from Napoleon Dynamite. He was the uncle that lived in his van, taping himself throwing a football to himself, and was constantly wishing he could go back in time so he could relive one of his football moments and his life would be perfect. I've been having some similar moments (except in my case, there was an ex gf I had in HS, parents kicked me out, and she thought I abandoned her, 20 years later I find her and she's still makes me sigh but she's married with kids, like I am)

So with my slightly smarter than Rico brain I've been exploring the possibility of time travel. I have no physics background, etc.

It started off with a dream I had. I saw what looked like torus's made of water flying past me, like distortion waves. After they passed, I was in the past. I think the inspiration came from the Atlas 5 rocket going through the sundog last month.
http://www.youtube.com/watch?v=SsDEfu8s1Lw&feature=player_embedded# [youtube.com]

The next day I read up on bending time/space into a torus. I found out that at the speed of light, this is what happens to time/space naturally.
http://www.scribd.com/doc/17397008/SPINORS-TWISTORS-QUATERNIONS-AND-THE-SPACETIME-TORUS-TOPOLOGY-Paper [scribd.com]

I also know a bit about relativity. If I travel from earth at lightspeed, from my perspective on my spaceship time has stopped on earth.

So I started questioning what would happen if a torus of space time flew past me at the speed of light, and I was in the center of the torus as it passed. Would time stop around me while I remain in a normal time space? What if it went beyond light speed, would time begin to slowly go backwards?

If space/time travelling at 0 = our perceived passage of time.
If space/time travelling at 299,792,458 mph = time stopped
Then wouldn't space/time travelling at 599,584,916mph = our perceived passage of time in reverse?

Basically saying that at 599,584,916mph it would take me 22 years to get back to my sweetheart. If I wanted to get there in a few hours I'd be looking at getting space time to pass me by at 13,190,868,152,000mph

I'm not trying to say this is a valid theory, like I said I have no physics background at all. It's just something I've been thinking about a lot. The whole torus thing like I said, it was a dream and my thought was the reason you would want to bend space/time into a torus is to keep a region in the center of non bent time/space so you, the traveler would be safe.

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