Originally posted by twhiteheadYou believe, but we don't know, because he doesn't care to do his own definitions. His opinion is ..., that we know, but his opinion changes from time to time, sw we really don't know when he invents expressions like "in and out of phase".
By 'out of phase' I believe he means that there is no universal now ie your now is different from mine. This could lead to time-travel.
This cannot lead to time-travel à la H. G. Wells. If you think so anyway, please explain.
Originally posted by twhiteheadIf we believe in quantum gravitation theory, then we know. The shortest period of time is Planck time. See further http://en.wikipedia.org/wiki/Planck_time. 5.4*10^-44 seconds. This period cannot be divided in two halves.
I do not think it is known whether time is quantum in nature ie whether it is infinity divisible or has a minimum size. Whatever the case, it is certainly very very small. My computer quite happily operates at about 2 billion operations per second, and each of those operations is a 'now' for the computer.
2 billionth of a second is only 2*10^-9 so in one 'now' for your computer there are 2.6*10^37 instants in universe. Your computer is slow as a snail. And still slower.
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Originally posted by FabianFnasLuckily, I think you, KazetNagorra and I do accept relativity theory, so it should not be a problem. This current discussion is whether or not a universal now is compatible with relativity - and of course what is meant by 'universal now' in the first place.
This information doesn't mean anything to those not believing in the relativity theory.
Originally posted by twhiteheadI'm merely thinking about Kelly. He does not believe in the relativity theory. I think that's because he doesn't know much about it. And in turn, doesn't want to larn anything about it.
Luckily, I think you, KazetNagorra and I do accept relativity theory, so it should not be a problem. This current discussion is whether or not a universal now is compatible with relativity - and of course what is meant by 'universal now' in the first place.
If we, Kelly and others, discuss the essence of time, then we should remind ourselves of what science gives us in the matter. If we're just talking about opinions, then it doesn't give much.
Kelly doesn't believe in time dilation, he thinks it's an faulty observation due to faulty measuring tecniques.
Kelly doesn't believe that we know anything about the age of the universe, he thinks it's an faulty observation due to faulty measuring tecniques.
He doesn't believe in any measuring tecniques giving results opposing his opinions. And this is the main problem with the line of reasoning that Kelly's doing.
I don't discuss about how long a 'now' is. We can define as we please. It doesn't change anything. I don't discuss Kellys opinions in any matter. I'm more interested in Kellys reasoning, how his universe ticks, based on his opinions. Not his opinions in itselves.
Originally posted by twhiteheadWell, it doesn't make any sense to talk about points x,y,z,t in spacetime, only points x,y,z,t in some intertial frame of reference. But let's take a closer look at your rules. Rule 1 is basically just a description of timelike and spacelike intervals in spacetime. Rule 2 tells you that space is not bounded, which it isn't, at least not from principles of relativity alone. What either rule has to do with "universal now" I'm not sure, because you would have to look at multiple observers to say anything about that.
I know that, and wasn't aware that my definitions implied it was so.
Do you think my rules would not hold over different frames of reference?
Originally posted by KazetNagorraI'll ask this again, not necessarily to you Kazel, but does "now" even have
Well, it doesn't make any sense to talk about points x,y,z,t in spacetime, only points x,y,z,t in some intertial frame of reference. But let's take a closer look at your rules. Rule 1 is basically just a description of timelike and spacelike intervals in spacetime. Rule 2 tells you that space is not bounded, which it isn't, at least not from principles ...[text shortened]... not sure, because you would have to look at multiple observers to say anything about that.
a time interval in it?
Kelly
Originally posted by KellyJayI did actually answer this question some postings ago:
I'll ask this again, not necessarily to you Kazel, but does "now" even have
a time interval in it?
Kelly
If we believe in quantum gravitation theory, this is what we know. The shortest period of time is Planck time. See further http://en.wikipedia.org/wiki/Planck_time. 5.4*10^-44 seconds. This period cannot be divided in two halves.
If the shortest time interval there is, then there is 5.4*10^44 'nows' in every seconds. If a 'now' is shorter than that it has no duration at all.
So we can define a 'now' as the plack time of duration, or zero time duration. However, this definition has no practical use.
Originally posted by KazetNagorraI didn't realize that. Surely if in one inertial frame of reference, a proton exists at x,y,z,t then it exists in every other inertial frame of reference at some x1,y1,z1,t1? In fact, surely it exists in every frame of reference, inertial or not? If so, how would I refer to it mathematically? How would I then refer to another point in space time?
Well, it doesn't make any sense to talk about points x,y,z,t in spacetime, only points x,y,z,t in some intertial frame of reference.
But let's take a closer look at your rules. Rule 1 is basically just a description of timelike and spacelike intervals in spacetime. Rule 2 tells you that space is not bounded, which it isn't, at least not from principles of relativity alone.
I didn't think that was what I was saying at all.
What either rule has to do with "universal now" I'm not sure, because you would have to look at multiple observers to say anything about that.
What I am trying to express is this:
I am sitting at my computer typing this post. It is 'now'. Somewhere in the world, you are also experiencing the same 'now'. There is a point in your timeline that is neither my future nor my past ie you are not in my past or future light-cones.
http://en.wikipedia.org/wiki/Light_cone
Moreover, for every person on the planet there is a unique set of points in their timelines such that no two points are in the same light cone.
For the sake of the above discussion, assume the surface of the earth is an inertial frame of reference.
Is it understandable? Is there a better way to express it? Does it violate relativity?