
#1
Jul1212, 09:18 PM

P: 10

If not, does the second law of thermodynamics even apply? What role would entropy play if it is not?




#2
Jul1312, 04:02 AM

PF Gold
P: 10,992

To our knowledge it is. At minimum you could count the observable universe as a closed system because anything outside it will not have had time to affect you locally due to the finite speed of light.




#3
Jul1312, 07:43 AM

P: 10

We once assumed that we would fall off the edge of the earth too. When you say "observable universe" you refer to technology constraints. If all assumptions are based on limits in technological capability, what is the point in exploration and creative thought?




#4
Jul1312, 07:58 AM

PF Gold
P: 10,992

Is The Universe A Closed System?The distance at which the original space that emitted the current CMB is believed to be about 14 billion parsecs, or 45.7 billion light years. The edge of the actual observable universe, with ANY form of radiation, is believed to be about 14.3 billion parsecs, 46.6 billion light years. (So the diameter of the observable universe is currently about 93.2 billion light years) Past this point we cannot see, even in principle, as nothing has had time to reach us yet. 



#5
Jul1312, 09:31 AM

P: 197

@Drakkith:
Isn't the universe closed system by definition? 



#6
Jul1312, 09:34 AM

Mentor
P: 5,337





#7
Jul1312, 09:38 AM

P: 10

Ok so, is the universe a perpetual motion machine? See where I'm going?




#8
Jul1312, 09:40 AM

P: 10

If the universe is a closed system, where are the boundries?




#9
Jul1312, 09:44 AM

Mentor
P: 5,337





#10
Jul1312, 09:47 AM

P: 10

In order for it to be a closed system, it would require boundries.




#12
Jul1312, 10:04 AM

P: 10




#13
Jul1312, 10:07 AM

Mentor
P: 5,337





#14
Jul1312, 10:37 AM

P: 526

Another consequence of the FLRW spacetime is that, as Ryan points out, it has no boundaries. It could be infinite. If it is finite, it's either a simply connected surface or a nonsimply connected surface. As Darkkith explained, because of the rate at which the universe expands, we can approximate our observable universe to be a closed system. So yes, it obeys the second law. 



#15
Jul1312, 11:09 AM

P: 274

What about virtual particles? Wouldn't the existence of virtual particles imply that the universe is not closed? Virtual particles seem to come from outside of the universe and appear inside it.




#16
Jul1312, 11:20 AM

P: 526





#17
Jul1312, 11:24 AM

P: 274





#18
Jul1312, 11:29 AM

P: 274

xAxis wrote:
In a way, that the universe is a closed system can become a useless tautology. Let's rename universe "everything" and let's replace the predicate: is a closed system with contains everything. After all, if something contains everything then beyond its borders is nothing. (though you could make the argument that speaking of the universe's borders is not sensible but you know what I mean) So now if you put the new subject and predicate together you get a useless tautology: everything contains everything. 


Register to reply 
Related Discussions  
Our Universe Is A Closed Electron In A Far Grander Universe We Can Never See?  Cosmology  20  
Two separate barycenters of a binary system in a small closed universe?  Cosmology  2  
Is the universe a closed system?  General Astronomy  2  
Is the universe an open or a closed system?  General Physics  8  
Closed Universe?  Cosmology  4 