md65536

The answer to that is the answer to the thread and I don't think anyone knows. "Time is (a measurement of) change" is also insufficient, because things can change slowly or quickly (the same amount of change can correspond to different amounts of time), and also it can't be "Time is (a measurement of) rate of change" because the same rate of change can be maintained over different amounts of time. I don't think "change" is the essence of time. Entropy might be. The constancy of the speed of light certainly is related (but if time is defined based on light, it might be cyclical because distance is already defined based on time). If change is expressed in terms of the passing of information across distances, then a definition of time based on change might work. Personally, I think (so please disregard this as anything more than just an idea) that "time is distance" is true, but as I mentioned distance is based on time. Also, the assumption of isotropic propagation of light makes it false. But if light was anisotropic and time and distance were equivalent, then a non-cyclical definition of time would be defined using something other than distance. My guess would be: Time and distance are emergent measurements of causality's consistency. Or instead of that, maybe something that even makes sense.

Making something more defined or definite means to specify it more precisely, but you're doing the opposite and specifying it more generally. I think you're literally undefining "naked mole rat" here, and undefining time with "A to B" (both by removing the meaning of time, and by not being specific about what A and B are). Meanwhile a definition like "time is what clocks measure" specifies it precisely, but doesn't say much about its meaning, which is essentially what the thread is seeking. That said, "simplest" and "most precise" might be mutually exclusive, in which case the simplest definition would only have to be precise enough to still be considered a definition at all.

The problem is that you'd have to back up those claims with irrefutable evidence.

It would be insufficient even if it wasn't left up to interpretation. As in, "time is the difference between two points in time" or "time is the progression from one point in time to another" or something. "A to B" would leave time still undefined even if it was clarified that it was referring to times. If we allow such meaningless cyclical definitions, then the simplest (non)definition would be "time is time." Either way you'd need time to be predefined for the statement to have meaning. On the other hand it could be interpreted in different ways that already have predefined meaning, such as "Time is the distance between two events". I don't think this definition would correspond to other accepted definitions, such as "Time is what clocks measure".

If they're points in space, yes. If they're points in time, no. If they're events it could be a spacetime interval which I believe can be decomposed into a spatial and a temporal component.

I've had similar thoughts: Humans desire to know where they come from. Most cultures have creation myths. We tend to explain unknown things in terms of known things. So for example, we see that humans have the ability to create things, so when we imagine a creator it is easiest to imagine it in terms of something already known to be able to create. So I figured that humans imagined the concept of a creator having a human form. At the time I thought it was a revolutionary idea but it's been thought of before. I recently read the notes in the liner of Jethro Tull's album Aqualung: 1 In the beginning Man created God; and in the image of Man created he him. Their message with this album is that organized religion creates the image of a god that they envision, and then distorts that image in all sorts of ways for all sorts of reasons. I would agree that we don't have a good understanding of the nature or even questionable existence of gods, but that we as humans have always made assumptions about the unknown based on the known, and that humans are the most god-like known thing. Depending on your definition of "god", humans may fit that description. For example, a conscious being who is aware of all my thoughts and actions and judges me for what I do... this describes my conscious mind. Or, if you describe god simply as "a giver of life" you might interpret it such that the sun fits your definition of god. It may be only that we assume that a god must be human-like, that we think it foolish for ancient civilizations to call the sun a god, when really it need not be more than just an admiring name for what it really is. The God that many major religions describe typically has both human and super-human properties, that define something that must be more than just a human. But I think it would make more sense if you phrased ideas and vague or conditional thoughts as such, rather than stating them as absolute facts.

Since no one's answered here's what I had in mind: I don't know if both the question and the answer are logically and semantically "bullet proof" but if not, I think it should be possible to fix it so that it is. ??? In case that last variation made sense, then continuing the theme... 5-door insane variation: Assume a similar set up to the last variation, but now there are 5 guards (you don't know which is which) and 5 doors. One guard always tells the truth. One guard always lies. One guard is insane and consistently alternates (as described above). One guard is a duplicate of one of the above 3 guards (but you don't know which). One guard alternates between acting like each of the above 4 guards (alternating for each evaluatable atom in your question), in an unknown but consistent order. Assume that it remembers whether the insane guard was last truthful or dishonest, and acts appropriately. What would you ask?

Does a grenade correspond with danger, not in meaning but in terminal sound of the two words?

Another way to think about it or explain it is that the head-on with each traveling 60 MPH would be like a car traveling 120 MPH slamming head on into a stationary car (in neutral). This would be softer than hitting say a wall (lower deceleration over a longer period of time compared to say brick wall), and the total mass of 2 mangled car should continue moving at half speed (60 MPH -- lower overall deceleration compared to say a brick wall). If you explain it using the example of a 120 MPH car hitting a movable stationary car, it's clear to see that this isn't the same as hitting an immovable obstacle. With the former your velocity changes by 60 MPH; with the latter it changes 120 MPH.

To clarify a vague idea that I'd posted earlier in this thread: Doesn't the OPERA result (if verified) only show that the "group velocity" of the neutrino density exceeds the speed of light? Only the amplitude of the probability of detecting a neutrino has been measured and/or interpreted to be exceeding c. In this case, the actual neutrinos would be traveling at slightly less than c, but the probability of detecting them would travel faster. Essentially this would mean that a signal of sparse neutrinos would become easier to detect just before a dense group of neutrinos arrives. If this is so, then it doesn't necessarily violate relativity. It is already known that a group velocity can exceed c without violating relativity. http://en.wikipedia..../Group_velocity Also, it would still be impossible to use this to send information faster than c (because you can't determine the changing probability of detecting a neutrino based on a single detection of a neutrino. For 2 or more positive detections, I don't know how the probability would be calculated, but I'll note again that the determination of v > c is based on a best fit of a graph consisting of a lot of neutrino detections over relatively long times, and certainly as the timescale and number of detections decreases the certainty of a change in probability amplitude also decreases. My contention would require that it is theoretically impossible with the OPERA setup to detect a change in the probability amplitude within 60 ns after a measurement (detection of a neutrino)... so that a "dense group of neutrinos" would still arrive before you could detect any change in the probability that it is coming. I have no idea how this would be determined). Still, this would be considered revolutionary maybe?, because it would demonstrate something like the wave function of some matter being affected by other remote matter. But I don't think it would invalidate any accepted theories that I know of. This is all speculation and I only know slightly more about what I'm talking about than I did before, which still isn't a lot, but I'm still betting that this is the cause of the OPERA results (admittedly mostly because "I want to believe").

That's correct to the best of my knowledge.

Suppose two snails are having a race. They both start out at a speed of 1m per day, but they both will slow down: After every hour, snail A reduces its speed by half. After every milliimeter covered, B reduces its speed by half. If the race is 1m long, who would win?

Go on, take a guess! What's there to lose? I've already given out so many clues: Meanings of words. Stems, and danger The riddle is strange, the answer yet stranger

Wrong thread.

Yes, where r is the radius (or side length, etc) of the mass. With astronomical sizes of nebulae, the mass would be astronomically larger (note the 3 dimensions of emphasis!). Note that this use of r is different from the previous use, where it was used to denote distance from us. However, the ratio of radiusnebula/distancenebula was chosen to be the same as radiusmoon/distancemoon. -- So in this case I guess it's proportional to r³ whether r is radius or distance. Even though the mass of the mythical moon-density nebula is cubically proportional to r, its gravitational pull is only linearly proportional to r, as described earlier. It would still be astronomically greater though, because the radius of the nebula is astronomically many times the moon's.

I agree. The idea of a nebulae-sized moon-like mass is pretty absurd in reality. I'm sure that it would have many (billions of?) times the mass of the entire universe. Even the sun is a lot less dense than the moon. I was thinking of calculating it for comparison, but I feel too lazy to.

Actually, it can. The result is a model with well-tested correspondence with observed reality. Ugh, yawn. I guess the supply of troll food ran out in the other thread. Plenty of fresh blood here! Start suckin!

Blurgh, sorry, thought everyone's forgotten the thread. It seems that at least it had slipped from my head. Who am I then? Certainly you don't know me. Find out and what I mean I'll no longer be. I am a word, and I have more than one stem, It takes some license to remove one of them, but if I've become stronger (look at me, see that I am) put back the stem and I'm where I began. In what sense correspondence? Its mention was terse. It's of terminal sounds of words or of lines of verse. As riddles go, this one's about fun as cancer You might roll your eyes when you find out the answer.

What about causality? Does it work in reverse identically to forward? What about non-determinism? Certainly the past is determined; does that mean the future must be? Or is the future undetermined and so is the past (if we reverse time we get a different past)? Are you speaking from opinion/belief, or from the standpoint of accepted science? What about entropy? It has a meaningful arrow.

Still out of my league but for fun: Yes. By the very nature of a "decimal expansion"... just map the n'th decimal place to the n'th natural number, and you have a 1-1 mapping between the number of digits and the natural numbers. If you have an infinite number of digits on both sides of the decimal (not sure if that makes sense) then alternate between them when counting. The even naturals will map to the digits on one side of the decimal, and the odds will map to digits on the other side.

I'm out of my league, but I think there are further problems. See http://en.wikipedia.org/wiki/Aleph_number The cardinality of the set of symbols representing digits in your proposed irrational number would be countably infinite and so would be aleph-naught. The cardinality of the reals is 2^aleph-naught, and the set is uncountable. It sounds like the "continuum hypothesis" implies that this really is a valid form of "infinity plus one". I suspect that the ability to construct a set is similar to the ability to count it, so you could construct a set of symbols representing the digits of an irrational number -- or at least you could construct every given symbol in that set, which I guess isn't the same as constructing the complete set. Either way you couldn't do the same for the set of reals. I would say that setting C to infinity and then manipulating it arithmetically and expecting relations to hold (like 2^C > C) is an error. Anyway, your statements above might still be logically true in that "If we can do something impossible, then we can do something else impossible."

You mean like "infinity plus one"? Yes, I misread what you wrote. I think the mistake is in treating infinity as a normal number. But the number you're imagining would be a real number. It just wouldn't require "more than infinity" symbols to describe it.

Is that, "there would have had been", or perhaps "there would soon be"? I suppose you mean relative to the number or quality of future "cooler" gizmos that we should still expect. It will just have to be someone else who makes them a reality. I suppose if there's something we can learn from Jobs, it's that... If you think that something is possible, don't rest until someone else makes it a reality. That's not meant as an insult; Jobs was a leader more than an engineer, and if we all did only what we're capable of doing ourselves, then we'd probably mostly give up soon after dreaming up an idea. If more of us work with persistence to make imagined possibilities real, we should have some pretty cool gizmos in the next 20 years.

The cardinality of the reals is infinite. You're right in that infinity is not in the reals. Intuitively thinking of this number (infinity) as a real number is the error.

http://en.wikipedia.org/wiki/Present Related is the notion of an instant: http://en.wikipedia..../Cauchy_surface Another quote from above: http://en.wikipedia....s_.22present.22 Personally, I disagree with Einstein's quote there. If every event can be ordered in a sequence, with all causative events placed "before" and all effected events placed "after" (and any non-causally related event placed arbitrarily maybe), then the past and future relative to an event can be consistently defined (with many possible consistent choices for those arbitrarily placed events). Then the present can be defined relative to any event. The act of observing or experiencing a moment of time can be called an event (or a set of events); the present would be a set of events simultaneous to that. -- In agreement with Einstein this set is not distinct, and the separation between past and future can be made arbitrarily... However, the only real significance of past and future involve causally related sequences of events, and causally related sequences of events have a distinct ordering. If the present can be defined relative to any event (as in, any event happens in that event's present), then the present is different for everyone and for every observation. Philosophically I would say that the present for a given person is the set of events simultaneous to the perception of being in or at any particular moment. Edit: But I wouldn't try to define a true present in terms of human perception, because the brain probably mixes a lot of recent "past" into its perception of the present, and probably deals with events out-of-order by different parts of the brain, in order to function. Our perception of the present is probably quite fuzzy and technically inconsistent.