T. A. Gardner
Thread Killer
Correct. You could have an infinitely wide Mobius strip. Then there are no boundaries, as well as no beginning or end.
If the universe is infinitely old, how did Today ever get here?
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So you didn't read my post before responding. Got it.
I was clear in that I was talking about closed systems where energy could be added which is what you showed.
But I'm curious why you think the universe could contain "cyclic entropy"? Whence does the added energy come?
T. A. Gardner
Thread Killer
The energy isn't "add"ed, but rather comes from natural processes within the universe itself. To use a finite example:
You have a mass of atoms that form a star (point D on my graph). The atoms through nuclear and gravitational interaction create energy (point A). The energy is transferred elsewhere in the universe allowing "things" to happen (point B). The energy expended causes the mass involved to cool (point C). That mass through gravity ends up forming a new star and you are back at D.
Now, that's grossly simplified, but hopefully you get the idea.
What you are describing is the state within the current universe. Locally entropy can be negative (as I clearly stated) but what you have suggested would have to act on the overall universe itself which means you want the universe to be an OPEN system which can take in more energy.
In order for your explanation to apply to the universe it would have to be leveraging some "hyper-universe" within which the universe exists as a closed system.
(Also when describing the actions of a Carnot cycle, stick with steam engines which is more applicable than whatever you were talking about with clusters of atoms etc. I mean you obviously have had a thermo class and all so I shouldn't question your "lecture".
I specifically and intentionally used the term natural numbers not real numbers, because the natural numbers are the positive integers, i.e. the counting numbers.
Since the example supplied was fingers, it doesn't make sense to use negative integers on the real number line. There are no negative fingers. Natural digits we would count from an origin of 1 or zero. Counting digits on a hand is finite, and has an origin point, unlike an infinetly old universe.
Also, it's apples and oranges. , I'm talking about real tangible properties of the universe, space and time. In the abstract, immaterial realm of number theory, infinity is an abstract concept that comes in different sizes and may not necessarily correspond to physical reality.
I don't think the question is an engineering question, and whether we can engineer a system where entropy does not increase.Entropy can be applied to a cyclic process so long as the result is zero at the end of the cycle. In a universe billions of years old, that could be occurring and we just haven't noticed.
2.6: The Entropy
phys.libretexts.org
Entropy, as I've demonstrated, can by cyclic so long as overall it equals zero at the end of each cycle.
Every cosmologist and physicist I've ever read says the universe has an arrow of time defined by the increase of entropy from a lower entropy past.
I've never heard anything about a cyclical cosmic entropy, though I appreciate you bringing it to my attention.
A boundary implies a transition between something and something else.
The consensus opinion is that there is only spacetime or there's nothing. There can't be a boundary between something and nothing, because nothing is literally 'nothing'. It doesn't even have the spatial dimensions of length, width, height, or volume.
I like money and material possessions too, but I can't spend all my time talking about it.
Yeah that would be engineering a closed system with decreasing entropy which is not allowed by the Second Law of thermo.
Pretty much everything I've read in the literature indicates entropy is what gives time its "direction".
Why? Days are just man made measures of time.
I wouldn't say it's really man-made. A day is a tangible unit of time existing physically in this universe as defined by one 360 degree rotation of the earth around it's axis. But I was just using day as a colloquialism, the unit of time one chooses to use is arbitrary, as long as it has a uniform periodicity.
T. A. Gardner
Thread Killer
Of course, there's the little problem that if the universe is infinitely old, wouldn't that make it a perpetual motion machine?
Let’s stay with day, a discrete example. Why must there be at least one more of them…? Which means, I take it, there’s never a today. Which makes no sense.
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Sammy Jankis
Was it me?
what do you think of the purple polka dot sombrero?
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Sammy Jankis
Was it me?
Sammy Jankis
Was it me?
Due to wordplay, that is
It doesn't make sense too me either. It's a question I've never heard an answer to from advocates of an infinitely old universe, although I presume there may be an answer.
If the universe is infinitely old, there should be an infinite amount of days behind us in the past. If true, how did we go though infinity days to get to today? The fact that today is here seems to imply to me there is a finite amount of days behind us.
actually NOT wordplay. Relativity. My simplistic understanding of the paradox is that since the second person is in motion ergo time is moving differently for them (this is a known effect of relativity) that when the two simultaneously look at the "events" time will be different for them and the events will be different.
I see your point. What if it only implies the answerable is unknowable so we might as well take today for the finite thing it appears to be, which is what we do anyway.