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Is time an illusion? (newscientist.com)
74 points by kqr2 on Mar 4, 2009 | hide | past | web | favorite | 40 comments

Great article - bad title. Saying that time might be an illusion is saying that time might not be "real". But a different model of time doesn't affect its realness.

Is temperature an illusion? Certainly not. And yet, as the article says, it's merely a model of the interaction between molecules.

Some models explain more than other models. Models that explain more are better. Thinking in terms of real/illusion is not helpful at all.

>> Saying that time might be an illusion is saying that time might not be "real".

No, the word "illusion" references an artifact that is both real and effective, yet whose true nature is misunderstood.

Moreover, for X to be an illusion, it necessarily must exist in some way.

You're both (a little) wrong! :)

You can't call something an illusion just because its true nature is misunderstood. An illusion is something that looks deceptively like something else. A hologram of a table is an illusion, but just misunderstanding the nature of a table (e.g. misunderstanding the fundamental particles from which it's constructed) does not make it an illusion.

Saying that time is an illusion is like saying that we appear to be living in a universe with time, but actually we don't. We are in fact experiencing something that looks like time, but isn't really time.

But obviously we do live in a universe with time, and the fact that time may turn out to be something strange or unexpected does not make it an illusion. It just means we misunderstood its true nature.

I believe they are saying time is a concept that is useful for explaining certain local experiences, but under certain more global circumstances, the defining characteristics of the concept of time could potentially change, causing us to need a new concept to describe it.

They didn't want to let January's "YOU ARE A HOLOGRAM" outpace the fine month February.

They're just saying time might be an abstraction after all, instead of a primitive.

I've always been more personally inclined to the social sciences - how people work and interact with each other. It always seemed to me that there's less red tape and formal background necessary to do interesting and practical work in social sciences.

But the more I think about it, the more I realize that damn near everything we do of value relies on hard science. If you had me pick one post-agriculture profession to be my only formal profession in the world, it'd have to be engineering. Engineering creates tools that greatly expand the ability of everyone else to do what they're doing. And yet, without physics and chemistry, we're not engineering damn near anything of value. Behavioral and social sciences have made such huge leaps due to increased communication, mobility, and processing and storing of information. All that can be credited to some damn amazing engineers, who all needed math and hard science to build what they did. It makes me remember from time to time, that though I'm not a hard scientist and will likely never more than dabble in it, it's pretty damn amazing stuff, and ought to be regularly given a nod of appreciation to its amazingness.

"All science is either physics or stamp collecting."

Ernest Rutherford

All Computer Science is either assembly programming or garbage collecting.

Or, to bastardize Greenspun's Tenth Rule (http://en.wikipedia.org/wiki/Greenspun's_Tenth_Rule):

All programming is either in Lisp or reimplementing it.

All generalizations are bad.

All assumptions about generalizations are generalizations.

"Time is an illusion. Lunchtime doubly so."

Douglas Adams.

All science is chemistry, the rest is just shit falling.

Just to clarify: the problem here is wave collapse. Wave collapse happens at an instant of time, and therefore picks a frame of reference. The wavefunction changes instantaneously over all space when "measurement" occurs, and does not obey the Schrodinger equation (or relativistic equivalent).

The "intriguing development" by Rovelli is that he used decoherence to explain measurement probabilities in some relativistic model. Time still exists in this model (which lives over R^{3+1}), but nothing happens instantaneously. Basically, he showed that the relativistic schrodinger equation gives the same experimental predictions as wave collapse.

Wave collapse hasn't been taken seriously by physicists in years. It's been thoroughly debunked again and again (c.f. http://www.npl.washington.edu/npl/int_rep/tiqm/TI_toc.html, http://www.flownet.com/ron/QM.pdf). The press keeps reporting it because it's such a delicious mystery.

Which physicists? As far as I know, copehnagen is the mainstream ontology.

I gave a talk last week on decoherence, just working out an explicit example where we can almost exactly solve the combined particle/measurement device system. The idea that wave collapse is unnecessary was not uncontroversial.

A quote from before I even gave the talk: "I don't believe you."

> Which physicists?

Well, Cramer (the one I cited) for one. David Mermin. Cerf and Adami. Roland Omnes. John Preskill. How many do you want?

> I gave a talk last week on decoherence

To what audience?

The audience of my talk was mixed math, physics and chemistry with a shared interest in quantum control.

As for the physicists you cite, the ones I recognize seem to work on either quantum information or foundations of QM. Decoherence is far more accepted in these fields than in the rest of physics.

Yeah, well, those are the people I would consider the authorities, wouldn't you?

BTW, collapse is easily debunked: take a two-slit experiment a put a detector at one slit. Interference is destroyed for all photons despite the "fact" that only half the photons "actually" interact with the detector. Collapse cannot account for this. (I put "fact" and "actually" in scare quotes because in true fact all the photons interact with the detector, but not according to the collapse theory.)

Try to define time. Or just go to the wikipedia article and listen to them try to define it, and digress into a discussion on how some people don't believe in it.

It's very hard to describe time without using the word time: A series of events -- What's an event? The best one I have is: Why can't two object occupy the same space? Well, they can, but at different times. Not really an explanation, but I think it's a good illustration.

Isn't time sort of like goodness, so fundamental that it's indescribable with invoking itself?

I've always thought of time as a measurement of change. No change, no time (i.e. if all particles in the universe were frozen in place at absolute zero then there would be no measurable change and time would not exist).

What you describe sounds like all particles in the universe suddenly lost all their energy. If time is change, time must be energy.

If time is an illusion, it's a very persistent one.

It's like physicists are discovering functional programming....

If science eventually proves without-a-doubt that the Big Bang was only one of many Big Bangs and that in fact, there seems to be no beginning or end to the Big Bangs, then the universe would essentially be infinite.

If it's determined that the universe, and everything in it, lasts (in one form or another) forever, then the meaning of time disappears. You cannot have time unless you have a beginning and an end.

Time only needs a beginning, it doesn't need and end.

Nobody can prove the Big Bang theory without-a-doubt: we only could rise theories against it, or bring facts against it, but it will stay an unproven theory forever, very similar to math theories: you can't prove them without-a-doubt, you only can give it credit currently, and because there hasn't been found any counter example yet.

Time is a very real perception, so the answer is "Yes" unless you're asking the metaphysical question "Is all perception an illusion?"

Maybe time only exists if it can be observed.

Maybe we are wasting our time discussing this. I agree that discussing this makes us feel intellectually satisfied, but nothing really worthwhile comes from this discussion.

I think 'Is time an illusion' is akin to asking 'define love'. I know it is corny.

Lunchtime - doubly so.

If time is an illusion that might explain why I feel like it disappears.

There is a theory that we only do exist because there is an entity outside of time which 'thinks' us continuously.

Anti-religious motivated downmods? Not cool, and not in the spirit of HN. Plus the idea that the whole world is a computer simulation is not religious and might also explain things.

How can an entity that is outside of time think us "continously"?

And how would you try to express something which is outside of our own possible experience? Sure, you could say "eternal present" or something; doesn't seem to sound much better...

I wasn't picking on your choice of words. If there is an ever-present something which effects our universe, and there is change in our universe, then there must be change in that ever-present something's universe, right? I mean, I suppose you could look at our universe as just a const 4-dimensional chunk of data with us simply moving along the time axis, but us moving along it is still change.

time isn't an illusion here where we are now, but it doesn't exist outside of this physical life-space.

> Is time an illusion?

Yeah, probably, just like all human sensory input.

I have a brilliant proof of this, but I'm so busy it'll have to wait until tomorrow.

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