Nucular
Illuminator
Here's a line with no beginning and no end:
Jon_in_london
Illuminator
- Joined
- Aug 7, 2002
- Messages
- 4,989
INRM said:
No. Everything has to come from somewhere.
Nucular
Illuminator
Well, I'm no physicist, but I would have thought that, if the path through time of the ray in question is reversible - equally well describable as moving backwards through time as forwards (as I believe the paths of some particles can be), then presumably we might equally well say that it ends at a finite point in the past, but has no beginning in the present or the future. Or, that could just be nonsense. I think I'll go with the latter.
Stimpson J. Cat
Graduate Poster
- Joined
- Sep 20, 2001
- Messages
- 1,949
INRM,
First of all, the appropriate question would be "Is this mathematically possible?", since lines and rays are mathematical objects, not physical objects.
Second, the designation "beginning" and "end" are arbitrary. A line is a set of points, as is a ray. In other words, what you have just described is also a ray.
Dr. Stupid
First of all, the appropriate question would be "Is this mathematically possible?", since lines and rays are mathematical objects, not physical objects.
Second, the designation "beginning" and "end" are arbitrary. A line is a set of points, as is a ray. In other words, what you have just described is also a ray.
Dr. Stupid
aggle_rithm
Unregistered
A
INRM said:
I think a quantum singularity most closely fits this description. Or any gravity field, for that matter.
A gravity well draws matter in from (theoretically) an infinite distance. Once it lands, it has reached the end point. (ignoring, for the moment, the effects of other gravitational fields.)
Stimpson J. Cat said:
What I was trying to ask is: If you hypothetically had a universe that always existed... or something like that, or an entity. Could it suddenly end?
Or would that not be possible because it never had a beginning point?
-INRM
Interesting Ian
Unregistered
I
INRM said:
If we subsisted in a Universe which had always existed, then an infinite time would need to elapse before we get to where we are now. An infinite period of time cannot elapse. Therefore we can't have a Universe which has always existed.
Stimpson J. Cat
Graduate Poster
- Joined
- Sep 20, 2001
- Messages
- 1,949
INRM,
I don't think that question has an answer. It would depend on the hypothetical laws of nature that apply to this hypothetical universe or entity. If you are asking whether the premise that some hypothetical thing has always existed necessarily implies that it must always exist, then I would say the answer is no.
Dr. Stupid
I don't think that question has an answer. It would depend on the hypothetical laws of nature that apply to this hypothetical universe or entity. If you are asking whether the premise that some hypothetical thing has always existed necessarily implies that it must always exist, then I would say the answer is no.
Dr. Stupid
Stimpson J. Cat
Graduate Poster
- Joined
- Sep 20, 2001
- Messages
- 1,949
Ian,
Two points:
1) The statement that a universe which has always existed must have existed for an infinite period of time, is not necessarily true. In a non-Euclidean universe, all that is necessary for you to say that the universe has always existed, is that there has never been a time in the past when it did not. If time itself does not stretch back infinitely, then the universe would not have to be infinitely old. In fact, since time itself is a feature of the universe, it is pretty much a given that the universe has always existed, and always will. That does not mean it is infinite.
2) I am not convinced that your second premise, that an infinite period of time cannot elapse,is logically valid. Care to elaborate?
That said, I am inclined to think that infinity is not something which is truly physically represented in reality, temporally or otherwise. But I certainly can't logically prove that this is the case.
Dr. Stupid
Two points:
1) The statement that a universe which has always existed must have existed for an infinite period of time, is not necessarily true. In a non-Euclidean universe, all that is necessary for you to say that the universe has always existed, is that there has never been a time in the past when it did not. If time itself does not stretch back infinitely, then the universe would not have to be infinitely old. In fact, since time itself is a feature of the universe, it is pretty much a given that the universe has always existed, and always will. That does not mean it is infinite.
2) I am not convinced that your second premise, that an infinite period of time cannot elapse,is logically valid. Care to elaborate?
That said, I am inclined to think that infinity is not something which is truly physically represented in reality, temporally or otherwise. But I certainly can't logically prove that this is the case.
Dr. Stupid
TillEulenspiegel
Master Poster
- Joined
- May 30, 2003
- Messages
- 2,302
Re: Re: Is this physically possible
The problem is more the limitations of communicating a counterintuitive postulate using the limited frame of language rather then the idea of same..
I think that a singularity is excluded because it is both a starting and an ending point, altho the effect of time dilation would make it a phenomenon that would be impossible to observe to a definite end as it would take eternity to reach the exact interior of the singularity.(or even the suberbs)
I would rather embrace an Einstien-Rosenberg worm hole (propagated by a different flavor of black hole) as a candidate as there is a gradual onset of the gravitational effect on a body ( theoretically over infinite space) and a point where the wormhole exits into "normal" space.
aggle_rithm said:
The problem is more the limitations of communicating a counterintuitive postulate using the limited frame of language rather then the idea of same..
I think that a singularity is excluded because it is both a starting and an ending point, altho the effect of time dilation would make it a phenomenon that would be impossible to observe to a definite end as it would take eternity to reach the exact interior of the singularity.(or even the suberbs)
I would rather embrace an Einstien-Rosenberg worm hole (propagated by a different flavor of black hole) as a candidate as there is a gradual onset of the gravitational effect on a body ( theoretically over infinite space) and a point where the wormhole exits into "normal" space.
Interesting Ian
Unregistered
I
Stimpson J. Cat said:
Don't be preposterous. Let's imagine the Universe sprung into being 5 minutes ago complete with the creation of our mutually consistent memories. When I say the Universe sprung into being I mean that space and time also did. Now according to your logic you would say the Universe has always existed. But then you would be using the phrase "has always existed" in a sense at odds with the rest of the human race. That is to say you are not using language in its proper sense in saying the Universe has always existed when it in fact has only existed 5 minutes.
{shrugs}
I can only say it is intuititively obvious. Are you maintaining it is logically possible?
Anyway, it's not physically possible. If the Universe had already existed for an infinite period of time, then the probability of anything happening now would be one over infinity, which equates to a zero probability. But things are happening now. Therefore the Universe cannot be infinitely old.
Stimpson J. Cat
Graduate Poster
- Joined
- Sep 20, 2001
- Messages
- 1,949
Ian,
I am not the one being preposterous here. You are by trying to address my comments with a physically impossible scenario. Specifically, my argument is based on our current understanding of the nature of space-time, whereas your example flatly contradicts our understanding of space-time. You are basically saying that if what I said was true, and then something impossible happened, then a contradiction would occur. Well, go figure!
As for the language issue, you may be able to use the English language to ask the question "Did the Universe exist 20 billion years ago", but that doesn't mean the question is meaningful. If time itself only goes back 14 billion years, then such a question is meaningless.
It's certainly not intuitively obvious to me. I wonder which one of us has the correct intuition? Oh yeah, I almost forgot. Neither of us do. Intuition has nothing to do with it. As for being logically possible, sure it is. Which is to say, it does not necessarily lead to a logical contradiction.
I have no idea how you came up with that line of reasoning. In particular, how do you justify the premise?
Dr. Stupid
I am not the one being preposterous here. You are by trying to address my comments with a physically impossible scenario. Specifically, my argument is based on our current understanding of the nature of space-time, whereas your example flatly contradicts our understanding of space-time. You are basically saying that if what I said was true, and then something impossible happened, then a contradiction would occur. Well, go figure!
As for the language issue, you may be able to use the English language to ask the question "Did the Universe exist 20 billion years ago", but that doesn't mean the question is meaningful. If time itself only goes back 14 billion years, then such a question is meaningless.
It's certainly not intuitively obvious to me. I wonder which one of us has the correct intuition? Oh yeah, I almost forgot. Neither of us do. Intuition has nothing to do with it. As for being logically possible, sure it is. Which is to say, it does not necessarily lead to a logical contradiction.
I have no idea how you came up with that line of reasoning. In particular, how do you justify the premise?
Dr. Stupid
I wonder if you can treat time as something that is separate from the universe? It seems to me that time is rather an attribute, or property of our universe. One doesn't exist without the other, in some form.
It's hard to get around our restricted viewpoint. It's like standing on the Earth and looking around in all directions, and thinking "the world can't go on forever". So you start walking in a straight line, determined to find the edge of the world. And you walk forever, around the globe, because from the viewpoint of someone walking on the surface of a globe, it really doesn't have a beginning or end. It's counter-intuitive, until you shift your viewpoint. Since we can't step outside the universe to see the true image, time looks like a straight line that must have a beginning and end.
It's hard to get around our restricted viewpoint. It's like standing on the Earth and looking around in all directions, and thinking "the world can't go on forever". So you start walking in a straight line, determined to find the edge of the world. And you walk forever, around the globe, because from the viewpoint of someone walking on the surface of a globe, it really doesn't have a beginning or end. It's counter-intuitive, until you shift your viewpoint. Since we can't step outside the universe to see the true image, time looks like a straight line that must have a beginning and end.
Interesting Ian
Unregistered
I
Stimpson J. Cat said:
a) The time factor doesn't matter. Make it 15 billion years rather than 5 minutes if you like. It doesn't effect the force of my argument. You are wrong as per usual.
b) You should realise that a denial of the literal existence of the past does not contravene any physical laws. If you think otherwise then name those physical laws which are contravened.
I can't help that your intuition is lacking in this respect.
If it is logically possible then I look forward to your demonstration showing this to be so.
Over an infinite amount of time anything which is physically possible to happen will happen at some point. Now let's consider some event, like say our lives whilst we subsist in this physical reality. We need not have been born now because it would be physically possible to have existed any other time in an infinite amount of time. Therefore the probability that we do exist now is 1 over infinity, which is zero. Therefore the Universe cannot have existed for an infinte period of time.
PixyMisa
Persnickety Insect
Perhaps many times, depending on the nature of the infinity.Interesting Ian said:
Fine.
Indeed, we may have lived out the exact same lives in the distant past, except that the PostScript Language Reference Manual was orange rather than red.
Your calculator is broken.
False premise, conclusion ignored. Redo from start.
aggle_rithm
Unregistered
A
I've heard one theory that the universe was originally four spatial dimensions, and at some "point" one of the spatial dimensions "became" time. This seems counterintuitive, since something cannot "become" something else if there is no time, and no point in time in which it can happen. However, the moment that the universe came into being, the laws of physics weren't quite what they are now, so it's difficult to imagine what was going on.
Stimpson J. Cat
Graduate Poster
- Joined
- Sep 20, 2001
- Messages
- 1,949
Ian,
You are correct, in that the issue of whether it is 5 minutes or 15 billion years is irrelevant. The point is that the Universe popping into existence, fully formed and in a state that indicates that it is billions of years old, is not physically possible according to our current understanding of the laws of nature.
Are you seriously claiming that the suggestion that the Universe appeared fully formed five minutes ago, as it was five minutes ago, does not violate any of the laws of physics?
It violates all of them! It violates the basic concept of science, which is that we can actually draw reliable conclusions about the universe from our observations. For it to be true, everything we think we know about how things work, would have to be wrong.
Obviously it must be my intuition that is wrong. After all, the great Interesting Ian is never wrong about any of his unsubstantiated gut feelings
There is nothing to demonstrate. The original assertion is so vague that it is impossible to show that it is true in general. You have claimed that an infinite amount of time cannot elapse. Under what conditions? Certainly we could invent hypothetical conditions under which, in principle, an infinite amount of time could not elapse. We could also invent hypothetical conditions under which an infinite period of time could elapse. Since no specific set of conditions was stipulated, clearly it is logically possible. As to whether it is possible in the real World, I don't know, and neither do you.
Nope, sorry. Imagine for a moment that a Universe existed for an infinite period of time, and that a species of intelligent beings existed in that Universe for a period of 10,000 years. Now, during that 10,000 year period, what is the probability that you are in that 10,000 year period? One.
It is called the anthropic principle. Once you acknowledge the fact that we, as a species, have actually existed for a non-zero period of time, it is trivial that we will actually exist during the period of time in which we are able to question the likelihood of our existence. As will the (presumably) infinite number of other intelligent life forms that will spend a finite amount of time existing in this hypothetical infinite Universe.
Put simply, your math is wrong. I suggest you brush up on it a bit before you tell other people they are being preposterous for disagreeing with you about it.
Dr. Stupid
You are correct, in that the issue of whether it is 5 minutes or 15 billion years is irrelevant. The point is that the Universe popping into existence, fully formed and in a state that indicates that it is billions of years old, is not physically possible according to our current understanding of the laws of nature.
Are you seriously claiming that the suggestion that the Universe appeared fully formed five minutes ago, as it was five minutes ago, does not violate any of the laws of physics?
It violates all of them! It violates the basic concept of science, which is that we can actually draw reliable conclusions about the universe from our observations. For it to be true, everything we think we know about how things work, would have to be wrong.
Obviously it must be my intuition that is wrong. After all, the great Interesting Ian is never wrong about any of his unsubstantiated gut feelings
There is nothing to demonstrate. The original assertion is so vague that it is impossible to show that it is true in general. You have claimed that an infinite amount of time cannot elapse. Under what conditions? Certainly we could invent hypothetical conditions under which, in principle, an infinite amount of time could not elapse. We could also invent hypothetical conditions under which an infinite period of time could elapse. Since no specific set of conditions was stipulated, clearly it is logically possible. As to whether it is possible in the real World, I don't know, and neither do you.
Nope, sorry. Imagine for a moment that a Universe existed for an infinite period of time, and that a species of intelligent beings existed in that Universe for a period of 10,000 years. Now, during that 10,000 year period, what is the probability that you are in that 10,000 year period? One.
It is called the anthropic principle. Once you acknowledge the fact that we, as a species, have actually existed for a non-zero period of time, it is trivial that we will actually exist during the period of time in which we are able to question the likelihood of our existence. As will the (presumably) infinite number of other intelligent life forms that will spend a finite amount of time existing in this hypothetical infinite Universe.
Put simply, your math is wrong. I suggest you brush up on it a bit before you tell other people they are being preposterous for disagreeing with you about it.
Dr. Stupid