What Is Time? One Researcher Shares His Exploration 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."
Timeline (Score:1, Interesting)
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.
Sean Carroll's "Real Rules for Time Travelers" (Score:4, Interesting)
http://discovermagazine.com/2010/mar/02-the-real-rules-for-time-travelers/article_print [discovermagazine.com]
What Is Time? (Score:5, Interesting)
Re:Timeline (Score:4, Interesting)
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 (Score:3, Interesting)
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:What Is Time? (Score:4, Interesting)
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? (Score:5, Interesting)
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:Timeline (Score:4, Interesting)
Islamic view of "time" (Score:2, Interesting)
In TFA, he basically contradicts evolution (Score:1, Interesting)
From TFA:
Entropy goes up with time, things become more disorderly
Basically, our observable universe begins around 13.7 billion years ago in a state of exquisite order, exquisitely low entropy. It’s like the universe is a wind-up toy that has been sort of puttering along for the last 13.7 billion years and will eventually wind down to nothing.
So, if entropy goes up with time, and things become more disorderly, how is it that species and advanced life forms become more orderly?
Re:But... (Score:5, Interesting)
If the universe were deterministic, then time is essentially meaningless even if it exists, since the start state and dynamics are all you need to know. And if the dynamics are information-preserving, any state (not just the start state) suffices. Apparently there are even deterministic interpretations of quantum mechanics, although I really don't know what that means.
Re:Easy (Score:3, Interesting)
Who said "Time is nature's way of stopping everything happening at once"? Was that Douglas Adams?
Re:Timeline (Score:4, Interesting)
It is explained by the fairly well substantiated fact that humans are poor judges of exact time and memory is often faulty. You remember knowing before hand, but did you actually know it or do you just think you knew? It is easy to misjudge a few seconds.
If you don't believe me that humans are poor at keeping time then I ask you, why do we have so many clocks around? Far more clocks than say thermometers or even distance. We don't need an alarm thermometer to tell us it is getting hot outside, but we often do need alarm clocks to tell us it is time for an appointment or if enough time has elapsed for an egg to boil or how long the microwave has run.
Re:Timeline (Score:4, Interesting)
If you write it down beforehand and document it when it happens, James Randi will give you 1 million dollars.
Re:Timeline (Score:3, Interesting)
You're assuming that people to whom this occurs have control over what they see and when. This is generally not the case in any reports of this sort. It's generally a very specific vision of a very specific event, usually an event associated with a major change in that person's personal life or a trauma (or death or...). My current theory is that certain traumatic events propagate in a ripple through time, and that some people have the ability to sense ripples that personally affect their own futures or the futures of people close to them. That's just a hypothesis based on limited evidence, of course.
Re:Time? (Score:3, Interesting)
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?
Time has effectively ceased if nothing has changed, therefore time is nothing. You've answered your own question, time does not exist, only matter and energy. Rates of change are simply questions of quantities of energy applied.
Re:But... (Score:3, Interesting)
Wired.com: In this multiverse theory, you have a static universe in the middle. From that, smaller universes pop off and travel in different directions, or arrows of time. So does that mean that the universe at the center has no time?
Carroll: So that’s a distinction that is worth drawing. There’s different moments in the history of the universe and time tells you which moment you’re talking about. And then there’s the arrow of time, which give us the feeling of progress, the feeling of flowing or moving through time. So that static universe in the middle has time as a coordinate but there’s no arrow of time. There’s no future versus past, everything is equal to each other.
The essential point is that the 2nd law of thermodynamics is really a backward way of looking at the question. It isn't that entropy increases with time. It's that we define "forward in time" to mean, "the direction of increasing entropy". Our local region of the multiverse happens to have an entropy gradient in one direction, so that's the direction we perceive time to increase in. But other regions of the multiverse might have different directions of increasing entropy, and hence different "arrows of time". And still other regions of the multiverse are completely flat with regard to entropy. In those regions, it isn't meaningful to define any arrow of time at all.
We feel like we're "moving through time" because we can only remember the past, not the future. If we could remember past and future equally well, we wouldn't have that sensation. Every moment would feel static, equally connected to past and feature. We wouldn't have a sense of moving in one particular direction.
So the question is, why can't we remember the future? And the answer is, because increasing entropy is needed to form memories. Just after the big bang, the universe was in a state of very low entropy. All the energy in the universe was concentrated in a tiny region of space. Since then, that energy has steadily spread out and become more diffuse (that is, entropy has increased), but the process still has a long way to go. We still have enormous amounts of energy concentrated into small areas known as stars. But energy is continuously flowing out from our sun and getting transferred from one form to another. Nuclear reactions produce high energy photons, which are used by plants to produce sugars, which our bodies use to produce ATP, which we use to manufacture proteins and form synapses and do all the other things needed to form a memory. At each stage, energy is converted from one form to another, and the entropy of the universe increases a little bit. Forming a memory is one of those transitions. On one side of the transition, the energy is still stored in ATP and the memory doesn't exist yet. On the other side of the transition, ATP has been used to form a memory, so the memory exists and the ATP has been split. Forming a memory requires using energy (and hence producing entropy), so the memory can only exist on the high entropy side of the transition.
CP != T (Score:3, Interesting)
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.
Sorry but you are confusing CP (matter/antimatter) symmetry and T (time reversal) symmetry. These are not the same. In addition time reversal violation does NOT mean that a process is irreversible it just means that it prefers to go in one direction over the other.
Both have been independently shown to be broken: CP in K and B meson decays and T in K and B meson oscillations which might be the source of your confusion. It is also worth pointing out that the combination of all three, called CPT, is expected to be conserved since it is a symmetry of relativistic space-time. If this is an unbroken symmetry then CP and T symmetries will be closely associated with each other but even then they will still be different.
If the CPT symmetry is broken then we end up with weird effects like Lorentz-violation, antiparticles with different masses to particles and really fundamental things like Quantum Field Theory break down. This makes it very hard to even construct CPT-violating models (although they do exist).
TFA is bullshit (Score:3, Interesting)
I got zero new information about time in the article.
From wikipedia:
http://en.wikipedia.org/wiki/Entropy [wikipedia.org]
"Entropy is the only quantity in the physical sciences that seems to imply a particular direction for time, sometimes called an arrow of time. As we go "forward" in time, the second law of thermodynamics states that the entropy of an isolated system tends to increase or remain the same; it will not decrease. Hence, from one perspective, entropy measurement is thought of as a kind of clock"
Bad car analogy:
This is silly in a same way if you had an indicator light that would turn on only if you are going forward, and then call that light "a speedometer".
Re:Timeline (Score:3, Interesting)
And you're assuming they perform better than random chance. You don't need to make a prediction on demand to claim Randi's $1M prize, you just have to make a very specific prediction of a very specific event that cannot be deduced by logic, pop it in an envelope and send it to him before the fact. You can send more than one prediction but if you do then you must score significantly better than random chance.
Randi's father was killed by his own wishfull thinking [youtube.com]. Needless to say I think that reading a good book on the art of skepticisim such as Sagan's Demon Haunted World [wikipedia.org] would be much more profitable than sending random predictions to Randi, it's just that the profit cannot be measured in monetary terms.
Personally I learnt my first lesson in skepticisim over 30yrs ago from a book by Randi debunking Uri Geller whom I naively believed had wound my broken watch in one of his TV stunts. Turns out my Dad did it with a pair of tweesers when I left the room and didn't tell me until I stopped believing it myself several years later - pretty good life lesson if you ask me.
Anecdote: One night my ex-wife woke me at 3:00am and told me she'd had a nightmare where her aunt had died. She was accurate to within an hour.
Explaination: We had visited her dying aunt in hospital a few days before the dream. People remeber the random hits and ignore the overwhelming number of misses.
Anecdote: My current lady freind claimed angels appeared and saved her life when she momentarily fell asleep at the wheel.
Explaination: She was asleep and her subconcious was telling her she shouldn't be. If you have never had a strong visual hallucination then angles floating alongside you car would appear to be very strong proof they exist.
Pidgeon dance (Score:5, Interesting)
The human brain is very good at creating non-existant patterns in random noise. There is a classic phycological experiment (IIRC by Skinner), showing that pigeons do exactly same thing (ie: engage in superstisious behaviour).
In the experiment a feeder was set up so that it would drop a pellet of food randomly with a mean time between pellet drops of a few minutes. The feeder was placed in the pigeon cage for an hour or two at normal feeding times.
The hungry pigeon would just happen to make some random movement just before the pellet happened to drop. It then mentally connected that movement with food and would repeat it a few times in the hope another pellet would appear.
Occasionally it would make a different movement just before the pellet appaeared. It would then mentally connect this new movement with food and join the two movements together in the hope of getting more food. After a while the pigeon(s) had all created their own unique an complex dance that they would start endlessly performing whenever the dispenser was introduced to their cage.
The really interesting part is that the time it took to perform a fully developed pigeon dance was always equal to the mean time between random pellet drops, meaning the pidgeon was virtually garenteed to recieve the reward after one or two performances of it's dance. Connecting random dreams to future events after the fact is just one of the many human forms of the pigeon dance.
Re:What Is Time? (Score:3, Interesting)
Another version (Sorry, don't know if it was from Einstein or from the Meisner Thorne Wheeler book) is that time is chosen to make physics look simple. If I plot the position of an object without any forces acting on it, I can choose time to be such that its position is a linear function of time. Since clocks are based on mechanics, this pretty directly turns into time is what a clock measures.
Once you go beyond that sort of description you need to tread carefully to avoid turning your physics into philosophy. For it to be physics it needs to predict measurable quantities. The original article meets this definition if it can make definite predictions - I couldn't tell for sure from the interview.
Re:Time is the goo... (Score:5, Interesting)
A line doesn't have to move across a plane.
A plane doesn't have to move across space.
So why, then, is space constantly moving across time, always in the same direction? Is "God" pushing our "space" through "time"?
Why do we "experience" anything at all? Why are we not just static sequences of space?
I think time is a little something other than "just another dimension". But who can really say?
Re:Timeline (Score:2, Interesting)
Re:Time is the goo... (Score:1, Interesting)
Two points describe a line.
Three points describe a plane.
Four points describe a volume.
Five points describe a time.
Therefore...
A line describe the time-motion of a point.
A plane describe the time-motion of a line.
A volume describe the time-motion of a plane.
A time describe the time-motion of a volume.
So why, then, is space constantly moving across time, always in the same direction? Is "God" pushing our "space" through "time"?
It isn't, it's not, and No.
Why do we "experience" anything at all? Why are we not just static sequences of space?
You're getting into an unrelated discussion of self-awareness. Technically we are static sequences... depending on your relative point of view.
I think time is a little something other than "just another dimension".
It's not "another" dimension. Well, at least not in the sense that it is an additional one. Time is a physical construct just as length, width, and depth are.