Why does time only move forward and not backwards?

  • B
  • Thread starter Tech2025
  • Start date
  • Tags
    time
  • #1
48
7

Main Question or Discussion Point

Probably an unanswered question , just wondering what people have to say.
 

Answers and Replies

  • #3
I'm sure the brilliant minds of this forum can explain what is known this far. I believe it has to do with entropy, where everything goes from order to disorder, at the same time our perception of time is skewed. Past, present, and future all existing at once. Glad you asked also interested in the opinions on this forum.
 
  • #4
7,966
4,647
I'm sure the brilliant minds of this forum can explain what is known this far. I believe it has to do with entropy, where everything goes from order to disorder, at the same time our perception of time is skewed. Past, present, and future all existing at once. Glad you asked also interested in the opinions on this forum.
You too should read the Wikipedia article.
 
  • #5
You too should read the Wikipedia article.
lol, I am.

After doing a quick Google search and reading what is quoted below I feel more confused. Down the rabbit hole I go.

"There is no connection between classical thermodynamic entropy(which is real) and “time” (which is an illusion), there never was, and there never will be.

No form of "time travel" is possible, for the simple reason that there is no "time," no "time direction," no "flow of time," there is only now — there are no “pasts” and no “futures” to go to! In physics (and in QM), there is only a measure of durations of events, and of the intervals between events: the "fourth dimension of time" in mathematical physics is an abstraction — invented to enable manipulation of "Minkowski space" metrics —- it does not exist in our real Universe.

Recommended reading: J.C.N. Smith's Time — Illusion and Reality.

“Time” has nothing to do with any form of entropy (see What is the Easiest Definition of "Entropy"?), which in turn has nothing to do with “order” or “disorder”: Entropy is measured in units of energy over temperature (i.e, in joule per kelvin (J/K)), as Wikipedia (correctly) states in the article Entropy:

Entropy is an extensive property. It has the dimension of energy divided by temperature, which has a unit of joulesper kelvin in the International System of Units But the entropy of a pure substance is usually given as an intensive property — either entropy per unit mass or entropy per unit amount of substance

I challenge all disinformed fans of the unscientific notion that “entropy is a measure of disorder,” to explain exactly how a “degree of order — or disorder, as the case may be — can possibly be expressed in units of energy and temperature!"
 
  • #6
jbriggs444
Science Advisor
Homework Helper
2019 Award
7,969
2,826
Probably an unanswered question , just wondering what people have to say.
As long as time moves in the same direction for everything, it does not matter whether that direction is labelled "forward" or "backward". Ripples from a rock dropped in a pond will appear to move outward either way.
 
  • #7
7,966
4,647
Down the rabbit hole I go.
Don't drag us into the hole also. It appears that you hopped all over on the Internet, sometimes to sources unacceptable on PF. Please give a link to every assertion that you make. (If this was not a B level thread, even Wikipedia is not acceptable.)

The OP asked about the direction of time. not "what is time". We have had many threads about "what is time" here on PF. They tend to get philosophical and get shut down quickly, so stay away from that.
 
  • #8
Don't drag us into the hole also. It appears that you hopped all over on the Internet, sometimes to sources unacceptable on PF. Please give a link to every assertion that you make. (If this was not a B level thread, even Wikipedia is not acceptable.)

The OP asked about the direction of time. not "what is time". We have had many threads about "what is time" here on PF. They tend to get philosophical and get shut down quickly, so stay away from that.
Ahh I see, I see. Good to know. Do not want to get banned, relatively new here.
 
  • #9
767
587
As long as time moves in the same direction for everything, it does not matter whether that direction is labelled "forward" or "backward". Ripples from a rock dropped in a pond will appear to move outward either way.
What about an exploding rocket? Time reversal there is obviously connected with entropy ... and the two directions are distinguished.
 
  • #10
jbriggs444
Science Advisor
Homework Helper
2019 Award
7,969
2,826
What about an exploding rocket? Time reversal there is obviously connected with entropy ... and the two directions are distinguished.
If the direction of low entropy is in the direction that somebody has chosen to label as "future" then time will proceed in "reverse". The two directions are only distinguished by the direction in which low entropy is located.
 
  • #11
767
587
If the direction of low entropy is in the direction that somebody has chosen to label as "future" then time will proceed in "reverse". The two directions are only distinguished by the direction in which low entropy is located.
Then
Ripples from a rock dropped in a pond will appear to move outward either way.
is not true
 
  • #12
jbriggs444
Science Advisor
Homework Helper
2019 Award
7,969
2,826
Then

is not true
If a rock spontaneously rises from a pond in the middle of a circle of converging ripples, the ripples will appear to move outward because the direction of low entropy is in the direction that you have chosen to call "future".
 
  • #13
767
587
If a rock spontaneously rises from a pond in the middle of a circle of converging ripples, the ripples will appear to move outward because the direction of low entropy is in the direction that you have chosen to call "future".
The smaller the circles the lower the entropy ... thus more into the "future", thus inwards. q.e.d
 
  • #14
jbriggs444
Science Advisor
Homework Helper
2019 Award
7,969
2,826
The smaller the circles the lower the entropy ... thus more into the future, thus inwards. q.e.d
So your claim is that ripples in ponds always converge inwards over time? That certainly does not match my experience.

Edit: I see now the scare quotes around "future" and agree with what you wrote.
 
Last edited:
  • #15
767
587
So your claim is that ripples in ponds always converge inwards over time? That certainly does not match my experience.
No, only if you choose the false direction, as you suggested.
"Time reversal" is a tricky thing! ...
[In Particle Physics it may be a symmetry, but not in everyday life ...]
 
  • #16
41
4
Time as a scalar quantity measurement (clock time) can be negative (or reversed) as often is the case in in mathematical equations.

The OP implicitly (or explicitly) is teetering to time as it is experienced in life, which is a manifestation of memory moving from the past towards the future and never is experienced in reverse. This time is probably more of a philosophical discussion than a scientific discussion.
 
  • #17
290
510
It's fun to derive the necessary philosophy from Feynman! His key words are NATURE KNOWS, in the QM part of the Lectures. So, Nature keeps incrementing Her knowledge, using the Spacetime as the organizer to keep it in order. Naturally, the organizer is being filled (with actual events) from one side forward, in a certain direction:smile:
 
Last edited:
  • #18
Vanadium 50
Staff Emeritus
Science Advisor
Education Advisor
2019 Award
23,721
6,132
So, Nature keeps incrementing Her knowledge, using the Spacetime as the organizer to keep it in order.
I don't think this makes sense. It's certainly not science.

I also think this question is ill-defined. What does it mean for time to "run backward"? What experiment could you conduct that would show this? You would quickly find yourself asking the question "backward with respect to what?" Presumably some universal clock that measures absolute time...
 
  • #19
767
587
I also think this question is ill-defined. What does it mean for time to "run backward"? What experiment could you conduct that would show this? You would quickly find yourself asking the question "backward with respect to what?" Presumably some universal clock that measures absolute time...
I guess you can restate it by asking if there is one preferred well-defined direction [of time]
 
  • #20
Vanadium 50
Staff Emeritus
Science Advisor
Education Advisor
2019 Award
23,721
6,132
You can ask all sorts of ill-defined things. What experiment could you conduct that would show this?
 
  • #21
767
587
You can ask all sorts of ill-defined things. What experiment could you conduct that would show this?
In the micro-world there may be time-reversal symmetry (equations invariant under the time-reversal symmetry operator/transformation), but not in Thermodynamics or Statistical Physics. You can use the direction of increasing Entropy (2nd Law of Thermodynamics) to figure out the direction of time ...
 
  • #22
Vanadium 50
Staff Emeritus
Science Advisor
Education Advisor
2019 Award
23,721
6,132
Stavros, you are ignoring what I am writing.
 
  • #23
767
587
Stavros, you are ignoring what I am writing.
What experiment? You seem to be the experimentalist ... you figure it out
 
  • #24
767
587
Stavros, you are ignoring what I am writing.
What experiment? You seem to be the experimentalist ... you figure it out
What I mean is that you haven't proven that such an experiment is not possible or it doesn't exist, nor it's impossible that it doesn't, per se or a priori, or even purely scientifically, unless/until that is proven. I offered you a starting point:
In the micro-world there may be time-reversal symmetry (equations invariant under the time-reversal symmetry operator/transformation), but not in Thermodynamics or Statistical Physics. You can use the direction of increasing Entropy (2nd Law of Thermodynamics) to figure out the direction of time ...
Rather you responded with a totally ambigious statement! I had to guess what you meant! [Then you went ahead and reported me!? ...]

Do you have a solution or proof for any claims? I am more than willing to hear! ...
 
  • #25
Vanadium 50
Staff Emeritus
Science Advisor
Education Advisor
2019 Award
23,721
6,132
1. It is not my job to come up with a counter-example to my own argument.
2. All you have succeeded in convincing me is that further discussion is a waste of time.
 

Related Threads for: Why does time only move forward and not backwards?

  • Last Post
2
Replies
42
Views
26K
  • Last Post
Replies
9
Views
871
  • Last Post
Replies
16
Views
711
Replies
6
Views
1K
  • Last Post
2
Replies
25
Views
5K
Replies
15
Views
2K
Replies
3
Views
845
Replies
8
Views
1K
Top