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<blockquote data-quote="Umbran" data-source="post: 52832" data-attributes="member: 177">There are a few... problems here that ought to be addressed.&nbsp; My apologies for the large sections of quoted text, but I find them invaluable to keep references obvious:Originally posted by RangerWickett Spacetime is one constant entity.&nbsp; Space and time are the same thing, which can be detected by experiments involving Einsteinian General Relativity.Yes and no.&nbsp; General Relativity puts time and space on the same mathematical footing.&nbsp; That is not equivalent to saying they are the same thing.Time flows forward.&nbsp; Why?&nbsp; We have never perceived time to flow backward.&nbsp; Since space and time are united, perhaps matter falls down through space in one direction (toward lowest possible potential energy) just as matter travels through time in one direction (toward the lowest possible potential energy). There is a major breakdown in your analogy here.&nbsp; In the process of moving from high to low gravitational potential energy by falling, an object accelerates - it's speed of motion increases.&nbsp; We have no evidence that the &quot;rate&quot; at which objects &quot;move through time&quot; is increasing.&nbsp; Our observations are consistent with all objects in the universe coasting through time at a constant &quot;rate&quot;, analogous to an object moving with constant speed in space - with no change in potential energy.Note: having a &quot;rate&quot; of motion through the time dimension is not a well defined concept.&nbsp; Speed is normally measured as a distance covered per unit time.&nbsp; Speed through time would be, what?&nbsp; Time covered per unit time?&nbsp; Thus I use quotes.Since the universe is expanding, and the law of the conservation of energy states that the universe cannot gain or lose energy, only convert it from one form to another, that would mean that as we progress forward in time, and matter becomes less and less dense, and the same amount of energy is spread over an ever-larger volume of space, then would not the potential energy in any given 5-foot cube be continually decreasing?This question has more than one answer...Being very picky about how you write it, the answer is, &quot;Generally, no.&quot;&nbsp; The amount of potential energy in a given 5-foot cube will continually decrease if and only if said 5-foot cube is completely and perfectly isolated from all other space.&nbsp; The statement holds only for very specific 5-foot cubes, not any cube.Attempting, instead, to read what you probably want to mean, the answer is, &quot;That rather depends what you mean by a 5-foot cube.&quot;&nbsp; Note that in an expanding space, what is meant by a foot is not necessarily well defined.&nbsp; As the space expands, so do all the rulers.&nbsp; Whether or not you say that the amount of potential energy in the cube decreases depends on how you account for the change in rulers.</blockquote>

[QUOTE="Umbran, post: 52832, member: 177"] There are a few... problems here that ought to be addressed. My apologies for the large sections of quoted text, but I find them invaluable to keep references obvious: [i]Originally posted by RangerWickett [/i] [B]Spacetime is one constant entity. Space and time are the same thing, which can be detected by experiments involving Einsteinian General Relativity.[/b] Yes and no. General Relativity puts time and space on the same mathematical footing. That is not equivalent to saying they are the same thing. [b] Time flows forward. Why? We have never perceived time to flow backward. Since space and time are united, perhaps matter falls down through space in one direction (toward lowest possible potential energy) just as matter travels through time in one direction (toward the lowest possible potential energy). [/b] There is a major breakdown in your analogy here. In the process of moving from high to low gravitational potential energy by falling, an object accelerates - it's speed of motion increases. We have no evidence that the "rate" at which objects "move through time" is increasing. Our observations are consistent with all objects in the universe coasting through time at a constant "rate", analogous to an object moving with constant speed in space - with no change in potential energy. Note: having a "rate" of motion through the time dimension is not a well defined concept. Speed is normally measured as a distance covered per unit time. Speed through time would be, what? Time covered per unit time? Thus I use quotes. [b]Since the universe is expanding, and the law of the conservation of energy states that the universe cannot gain or lose energy, only convert it from one form to another, that would mean that as we progress forward in time, and matter becomes less and less dense, and the same amount of energy is spread over an ever-larger volume of space, then would not the potential energy in any given 5-foot cube be continually decreasing?[/b] This question has more than one answer... Being very picky about how you write it, the answer is, "Generally, no." The amount of potential energy in a given 5-foot cube will continually decrease if and only if said 5-foot cube is completely and perfectly isolated from all other space. The statement holds only for very specific 5-foot cubes, not any cube. Attempting, instead, to read what you probably want to mean, the answer is, "That rather depends what you mean by a 5-foot cube." Note that in an expanding space, what is meant by a foot is not necessarily well defined. As the space expands, [i]so do all the rulers[/i]. Whether or not you say that the amount of potential energy in the cube decreases depends on how you account for the change in rulers. [/QUOTE]

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