Is the universe a causal system?

In summary, the question is vague and does not seem to fit well within the realm of what is discussed on this forum.
  • #1
HamzahA
6
0
A simple question. I might ask this as well: Is the universe causal?

The reason I'm asking this is that today I've ran into two guys having an argument about this, so I want to know.

Thank you.
 
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  • #2
And you want to jump into the middle of this argument because ...?

In any event, this question seems to fall more within the realm of philosophy than physics, and PF doesn't do philosophy according to its rules.
 
  • #3
In classical mechanics, yes. In GR, you need to be very clear what you mean by causal.
 
  • #4
I'm not jumping to the argument, it's just that those who were arguing seemed not to have any scientific background related. I'm simply curious.

I'll define causality like this: Causal System: A system whose output(s) depend on the current/past input(s).
 
  • #5
HamzahA said:
I'm not jumping to the argument, it's just that those who were arguing seemed not to have any scientific background related. I'm simply curious.

I'll define causality like this: Causal System: A system whose output(s) depend on the current/past input(s).

Yes, that is the standard definition and in no way changes my original answer. As I understand it, that standard definition is too vague in relation to GR and QM.
 
  • #6
phinds said:
Yes, that is the standard definition and in no way changes my original answer. As I understand it, that standard definition is too vague in relation to GR and QM.

Thank you for your response, but can you elaborate why is it too vague?
 
  • #7
HamzahA said:
Thank you for your response, but can you elaborate why is it too vague?

Unfortunately, I cannot. This is something that I heard once, thought was a bit weird and so briefly checked out on a couple of reputable sites and since it seemed to make sense, I just left it at that simple fact, since I did not want to delve further.

I assume you should be able to find stuff on the internet. Try Goggling "QM and causality"
 
  • #8
what I want to know is whether or not the universe is memoryless
 
  • #9
What is thread even about?
 
  • #10
Drakkith said:
What is thread even about?

I have no idea what oneamp is talking about, but what problem do you have with the OP's question? It seems perfectly reasonable to me, as do our interchanges. That is, the thread seems perfectly reasonable up until oneamp's interjection.
 
  • #11
HamzahA said:
can you elaborate why is it too vague?

Even in special relativity, there is no concept of "universal absolute time". So there is no simple concept of "event A happens before event B". One observer might claim that A happens first, while another observer (moving relative to the first one) claims B happens first, and both of them are right.

if you can't even be sure in what order "stuff happens", the idea of "causation" is rather hard to nail down.

If you really want to get your head around this, you need to do a course on special relativity. Warning: pop-science books and websites may be seriously misleading, or just plain wrong.
 
  • #12
AlephZero said:
if you can't even be sure in what order "stuff happens", the idea of "causation" is rather hard to nail down.

Perhaps, but I believe the order of events that an observer goes through will be seen the same by all other observers, right? For example, if I get up at 9 am my time and eat breakfast one hour later, all observers will agree that I woke up before I ate breakfast. Is that correct?
 
  • #13
Causality is invariant under SR. Since FTL travel is forbidden in both SR and GR, in no reference frame will you ever see a caused event precede its causative event. You need not worry about waking up full, Drakkith.
 
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  • #14
Chronos said:
Causality is invariant under SR. Since FTL travel is forbidden in both SR and GR, in no reference frame will you ever see a caused event precede its causative event. You need not worry about waking up full, Drakkith.

So no chance of waking up with the eggs already made then. Got it.
 
  • #15
As I recall Einsteins General Relativity admits solutions that form closed time loops, so strict adherence to causality must be imposed by some other means.

And within the realm of Quantum Mechanics there is the eternal quest to inject determinism into (for example) the decays of states, thus giving a casual response to question of type "why did this particle decay at t=10?" and "why did the fourth Hydrogen atom spin-flip first?"

As for oneamps question, I know I have a memory in my computer (I remember buying it) so the universe is certainly not totally void of memories. If you can manage a more well defined version of that question you might get a better answer.
 
  • #16
Uh, this might not be the right place, but I have a question for all of you PhysicsForums veterans with thousands and thousands of posts. I've just been incredibly impressed by the level of discussion here and I want to get where you are.

What are you educations? What did you focus on in college? How long have you been physics enthusiasts?
 
  • #17
Agrasin said:
Uh, this might not be the right place, but I have a question for all of you PhysicsForums veterans with thousands and thousands of posts. I've just been incredibly impressed by the level of discussion here and I want to get where you are.

What are you educations? What did you focus on in college? How long have you been physics enthusiasts?

This is best asked in the General Discussion forum. Otherwise we'll have to sic Phinds on you! (He's more bark than bite, but his slobber is the real threat)
 

1. Is the idea of the universe being a causal system supported by scientific evidence?

The concept of causality is deeply ingrained in our understanding of the world, and many scientific theories and experiments support the idea of a causal universe. For example, the laws of physics, which govern the behavior of matter and energy, are based on cause and effect relationships. Additionally, the Big Bang theory, which is currently the most widely accepted explanation for the origin of the universe, is based on a causal chain of events.

2. Can we prove that the universe is a causal system?

It is important to note that causality is a philosophical concept, and as such, cannot be definitively proven or disproven by science. However, the scientific method relies on the assumption of causality, and the vast majority of scientific theories and experiments are based on this principle. Therefore, while we cannot definitively prove that the universe is a causal system, the evidence strongly supports this idea.

3. What is the definition of a causal system?

A causal system is one in which every event is the result of a preceding cause. This means that every action or occurrence in the universe can be traced back to a specific cause or set of causes. Essentially, a causal system is one in which there is a clear relationship between cause and effect.

4. Are there any alternative theories to the universe being a causal system?

Some philosophers and scientists have proposed alternative theories to causality, such as determinism and indeterminism. These theories suggest that events in the universe may not always have a specific cause or that the concept of cause and effect may not be applicable to certain phenomena. However, these alternative theories are not widely accepted and do not have as much scientific evidence to support them as the idea of a causal universe.

5. How does the idea of a causal universe impact our understanding of free will?

The concept of free will is a complex and debated topic, and its relationship to causality is often a point of contention. Some argue that if the universe is a causal system, then all events, including human actions and decisions, are predetermined by preceding causes, and therefore free will does not exist. Others believe that free will can still exist within a causal universe, as the causes that lead to human actions may be complex and unpredictable. Ultimately, the impact of a causal universe on our understanding of free will is a philosophical question that remains open to interpretation.

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