Talk:Eternalism (philosophy of time)

Confused physicist says: I don't understand what this entry is about. It seems like a really botched version of relativity. Yes time is a dimension which is as real as the spatial dimensions, but no, this does not mean we have a 4D block. Instead all physical dimensions form a so-called (smooth) manifold. Blocks are not the only manifolds, but for example in 2 dimensions we have: sphere, torus(donut) and multitori (donuts with more than one hole). So if you want to understand time, study relativity. Block time does not capture the essence of relativity.

If you want to study relativity, go read the relativity articles. This article is not specifically about relativity, "botched" or otherwise, it's about a philosophical perspective on how to conceptualize the passage of time. "Block" probably isn't being used in the same technical sense as you're thinking in this case. Perhaps you could suggest some concepts in relativity that would be relevant for linking to here? There's already links to special relativity, simultinaity, and reference frames. Bryan 16:05, 21 Dec 2004 (UTC)

I love the entry on Block time. However, it brings up (I think) an interesting question, and the question should (I believe) be noted on the page:

Why is it now? Rather than some other time?

All times are "the present", according to an observer who is located at that particular time. Imagine a magic door with one side right in front of you here in 2004 and the other side right in front of Henry Ford in 1908. If you ask Henry Ford whether he's in the past, present, or future, he will of course say "the present." It doesn't matter if the door's open or closed, as far as Henry Ford is concerned 1908 is the present because that's where he is. Perhaps in 2039 someone will be browsing old Wikipedia talk: pages and see this conversation; from his or her perspective 2039 is "the present", but that doesn't affect our own perceptions here in 2004.

In fact, as you read this response, think back to when you first asked the question; at that point in time you were convinced that it was "the present". Now, however, you think that you asked the question in the past and now "the present" is right now (yikes). But that doesn't change the fact that you thought it was "the present" back then, just as you think it's "the present" right now even though that guy in 2039 thinks this all happened in the past.

As for why we all percieve our location in time to be "the present", I think that's probably due to the fact that we can remember events that occurred prior to any given location in time but not events subsequent to that location in time. Perhaps the thermodynamic arrow of time is responsible for that. Bryan 07:35, 7 Jan 2004 (UTC)

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Regarding this statement:

For example, relativity has shown that the concept of simultaneity is not universal, with different frames of reference having different perceptions of which events are in the future and which are in the past; there is no way to definitively identify a particlar point in univeral time as "the present".

As a layman, I'm having trouble getting this, and the entry on relativity isn't helping any. I can see how frame of reference can influence how I perceive the passage of time and how far in the past something happened, but I don't see how it affects my perception of which events are in the past. The article goes on to mention that people aren't able to observe future events, so there seems to be a contradiction here.

I've read nothing on the topic besides this article, and some introductions to relativity many years ago, and watching Cosmos.. so.. grain of salt :) --mjb

Simultenaity makes my head hurt too, when I pay attention to the details. :) Basically, it is my understanding that if there are two events "A" and "B" that occur some distance apart, there are some frames of reference in which an observer will see that event A happened before event B and some frames of reference in which an observer will see that event B happened before event A. The observer isn't observing anything in his own future, just observing two distant events that happened in his past and determining which one happened first. Since no frame of reference is more important than any other frame of reference, this isn't just an optical illusion.

I can't say why this works the way it does, offhand, I'd have to read up on it some more before I'd feel confident about writing anything over at special relativity. It does need to be explained more clearly, though, so if nobody with more physics knowlege than I gets to it before me I'll see if I can write something that I can understand. :) Bryan

Your confusion is understandable as it doesn't confirm to our common sense understanding of the world around us. The light clock thought experiment is an excellent way to refine your understanding of it. So here goes:

Empirical evidence supports the proposition that a given lightwave / photon particle will travel at a constant velocity irrespective of your interial reference frame; that means if you're going at c/2 (c equals the speed of light in a vacuum) relative to another frame of reference in the same direction as the lightwave, the lightwave will still be measured as going at c by parties in both reference frames.

Let's put a light clock in the frame moving at c/2. What happens when someone in the other reference frame looks at the light clock? He sees a ball of light moving along a diagonal path bouncing up and down between the two mirrors of the light clock. What does the person in the clock's reference frame see? He sees a ball of light moving straight up and down between the two mirrors. The ball of light that moved along the diagonal path had to travel further, and given that additive velocities only works in Newtonian mechanics, i.e. the ball of light is moving at the same speed relative to parties in both reference frames, that means the ball of light will take longer to bounce between the two mirrors for observers in the outside reference frame of the clock than observers inside the reference frame.

So time as measured by this light clock is moving slower in that reference frame relative to the other reference frame. (If parties in both reference frames had light clocks, both parties would see the other as moving slower. But this all gets reconciled, although it's a little tricky and beyond the scope of this reply.)

For a more tangible example of different parties seeing a different order of events happen, let me go over a train example:

A train is moving along in direction x. There are two laser sensors situated at opposite ends in one of its compartments. At the center of the compartment there is a laser that will fire beams at both sensors when turned on. When the sensors detect a laser beam, they light up. What happens when a person on the train in the compartment watches this process unfold? Both sensors light up at the same time. But what happens when someone on the ground, looking at the train go by, watches this process unfold? Since the train is moving in direction x, the laser beam moving in direction x towards the sensor nearer the front of the train must traverse a longer distance to reach the sensor than the laser beam that is moving towards the sensor at the back of the train. In Newtoniam mechanics, both observers would see the same thing as additive/substractive velocities would add to the velocity of the laser moving in the same direction as the train is and substract from the other laser, but we don't apparently live in a Newtonian world.

All sorts of interesting thought experiments can be done with this. What happens if the spaceship with the light clock moved at c? The ball of light in the light clock would use up all its velocity just to keep up and time would be completely still. And since we could use the light clock as a way to measure distance, space / distance itself is just as relativistic as time. If you were in a ship traveling at c, the whole Universe would be the size of a singularity.

Not only light travels at the speed of light; *everything* does. That is, everything moves through space-time at the speed of light. That means, the faster you move through space the slower you must move through time.

Can someone please provide links to validate this. I've never heard this before, and I find it interesting. -- Olathe November 17, 2003

That is the implication of special relativity, which follows from the finite speed of light. However, that is all relative to a detector, and assumes points in spacetime do not have a timestamp. The temperature of the microwave background seems to provide such an absolute timestamp, but I have seen no discussion of that. I guess the accelerating detector sees the universe expanding faster. Does that have any implications for our observations of the Hubble "constant"? ----

Anyway, hope that clarified some things for you. Relativity is fairly logical once you accept the premise of the constancy of the speed of light. It's light reading compared to quantum mechanics! No one understands it! :) --Spinoza

Block time/Eternalism

What is the difference between block time and eternalism? --Max 07:21, 16 November 2006 (UTC)

I believe there is no difference. - LegendLength 10:07 22 Jan 2007 (UTC)

Unsourced

The one source cited does not support the phrase "block time". This article is pretentious twaddle. The notion of "block time" is the same notion that time can be modelled as a dimension -- which is universally accepted amongst physicists. --Michael C. Price ^talk 11:54, 20 December 2006 (UTC)

Untrue. The Scientific American article in external links uses "block time", and the PhilSci article uses the similar "block universe" Bryan 04:19, 21 December 2006 (UTC)

The reference quote does not support the phrase "block time", nor the word "block" (note the word "not" in it!). Paul Davies is describing the universally accepted model of time as a dimension, similar to the other spatial dimensions. --Michael C. Price ^talk 09:18, 21 December 2006 (UTC)

Okay, I think I see the source of this problem. The footnote in question is not actually a reference, citation or source of any kind. It's just a footnote, a bit of extra explanatory text that doesn't otherwise fit into the flow of the article. What it's saying is basically "don't be confused into thinking that the name 'block time' means that the universe literally has the shape of a block." It doesn't invalidate the use of the term "block time" in general, it's just trying to make sure that the term isn't misinterpreted. For external sources see the Block time#External links section, those include the two I mention above. Bryan 01:02, 22 December 2006 (UTC)

No. Block time is the belief that time is literally a dimension that is no different from the 3 space dimensions around us. - LegendLength, 10:20 22 Jan 2007 —The preceding unsigned comment was added by 121.44.242.92 (talk) 09:10, 22 January 2007 (UTC).