Hawking's theories...

Great Debates
1

I have been reading up on Hawking’s theories because they fascinate me so much (although i can barely understnd Jack shit, i guess its mainly to impress the girls)However one of his theories has fascinated me most: He says ‘Why do we remember the past and not the future’ What does he mean?

2

minega, I’ve never heard this from Hawking but it is an area I have looked into:

What he means given that most of the fundamental laws of nature are time-symetric, how come we have more information on what happened in the past than what will happen in the future.

Here is one take on it (I belive the writer of the article is a psycologist:

http://www.goertzel.org/dynapsyc/1995/EGOANDTI.html

Here’s a slightly different version (posted for someone else on a different board):

3

But here you are talking about PREDICTING the future while we have already experienced the past. Can the two really be compared? Can you remember something that never happened?

4

Oh…you mean ‘to a certain extent’ i think…

5

But as stated above our memory is nothing more than a predication of the past. Memories aren’t and cannot be perfect.

At a certain point in time your mind has a set of information contained in it. This set of information can be used to find out what happened in the past and what will happen in the future, from this information you cannot find out either with perfect accuracy.

6

Obviously, you can find out what hapened in the past, better than you can find out what will happen in the future and Hawking’s question can be restated as: “why is there this inbalance?”.

7

An important admission from the quoted section, is about the formation of information and how that relates to entropy. As a result of the laws of entropy, information can only be formed in the past to future direction and not in the future to past direction.

8

Sorry not admission, omission.

9

But what do you mean by “never happened”? The future exists; we just don’t happen to be there right now. From what I understand, mathematically speaking, the past and future are symmetrical. They are just different points in the time/space continuum. From that perspective, to say that the future “never happened” is similar to saying that if I am standing in San Francisco, that St. Louis doesn’t exist. Does St. Louis only exist if I get in a plane and fly there?

By the way, if that kind of stuff interests you, I read a great book that describes many different theories about the nature of time and why we experience it directionally. I don’t know how dated it is, since I read it years ago - but it was enjoyable reading. ABOUT TIME: Einstein’s Unfinished Revolution by P. C. W. Davies.
http://www.amazon.com/exec/obidos/tg/detail/-/0684818221/qid=1047583136/sr=1-3/ref=sr_1_3/104-3537307-4496768?v=glance&s=books

10

In that case, we do remember the future. Think of say, driving to a party, thinking what it’s going to be like. Our memory of the future just tends to be less accurate than or memory of the past.

11

I knew you were gonna say that.:wink:

12

Yeah, and every time I do, my “memory” of this future party is that it’s always the bestest party ever! (My memory of past parties is always more disappointing, for some reason.)

13

Or maybe Deja Vu is us remembering the future?

Maybe it is just a latent power that we have no access to?

14

Hawking and a lot of cosmologists have historically been concerned about the symmetry of the universe over time-
he has said that at one time it was believed that the expanding universe would stop expanding and start contracting, and that during the contraction phase time would run backwards—
well that certainly doesn’t look like being the case, a recent theory says that the universe will expand faster and faster until our bodies and the Earth itself explodes.
No symmetry there I’m afraid.

15

When was time supposed to run in the imaginary (+i or -i) direction?

16

I just started reading A brief history of time, so presumably I can post here on the subject in either a brief moment or after a long eternity. I can report, however, that I don’t remember that post yet, so Hawking is off to a good start.

17

Generally, my memory after a party is usually a lot less accurate:D

18

What you’re all going to say next has really pissed me off.

19

Well, it is correct to say that the equations of both classical physics and quantum mechanics treat time as a symmetric variable, but that does not mean there is no diffreence between past and future. It just means that neither model is complete.

For the record, most physicists accept CPT (charge-parity-time) symmetry as an absolute law. Both experimental results and current cosmological theories, however, argue that the individual elements of that trinity are not symmetric. T assymetry (and hence CP assymetry) have been demonstrated experimentally for neutral kaons. So far as I know it has not yet been verified experimentally, but violation of CP (and hence T) symmetry for baryons is at the heart of current big-bang cosmology, since it is the mechanism used to account for the fact that there is more matter than antimatter in the observed Universe.

So, I’m afraid the premise in the OP is simply mistaken. While time is modeled as a symmetric variable in the mathematics of physics, it is not symmetric in the real world.

20

Yes spiritus Mundi but the time-symmetry violations you describe could not account for the amount of time-asymmetry in the macroscopic world. But however they could account for the arrangment of matter in the universe that is itself responsible for time-asymmetry.

If the universe was in total thermal equilibrium there would be, excepting the cases you described, time-symmetry. It is the nonuniformity of the universe that is responsible for macroscopic time-asymmetry.