I'm just going to ramble a bit and hopefully not be too wrong.
This whole idea of light-cones and relative 'future' and 'past'... is it okay if I think of it as sort of... the doppler effect with light as opposed to sound?
That is, something can happen on the sun, and someone on Mercury will see it "first", and someone on earth will see it "second", even though it's the same event.
Or does this sort of ordered-flow screw up thinking later down the road? A decent analogy for now, but it will only make things harder later?
And I would like to try and parse this a bit:
So what about an eruption on the Sun's surface 4 minutes ago? That cannot affect us *now*. So it is not in our past But nor is it in our future. We say that it is 'elsewhere', because us phsyicists think that sounds cool.
That cannot affect us *now*. -as in... that cannot affect us until the light photons from the event cross paths with us. -as far as the example goes... we cannot 'be startled' by the eruption on the sun exactly when it happens, because we don't even know that it occurred until 8 min after it actually happened.
We say that it is 'elsewhere'... -as in... this is something that, basically, the light photons from the event may (or may not...) at some point cross into our future light cone, and therefore become our "now". At which point, we can be affected by it.
So it is not in our past -right, because we haven't detected it yet, the light photons are only halfway between the sun and the earth
But nor is it in our future -I don't understand this. Do you mean it's not necessarily in our future? As in... we could not detect the explosion for some reason (say we're sleeping)? -if the explosion occured, and we're watching it with our telescope, and we are going to see it, when the photons reach earth... how is it not in our future?
But *elsewhere* events cannot influence me *now*, so even though I think the explosion occured 4 minutes before I clap my hands, there's nothing wrong with someone else thinking that it happened four minutes AFTER I clapped my hands. And that may well be what they see if they are travelling at an appropriate speed and direction relative to me and the Sun.
But *elsewhere* events cannot influence me *now* -right, because we have yet to detect them. There isn't even a chance for us to detect them because the photons haven't reached us yet.
so even though I think the explosion occured 4 minutes before I clap my hands -because when we finally see the explosion, we know that we clapped our hands 4 min. ago, and that it take 8 min. for light to travel to us from the sun?
there's nothing wrong with someone else thinking that it happened four minutes AFTER I clapped my hands. And that may well be what they see if they are travelling at an appropriate speed and direction relative to me and the Sun. -because they just saw the explosion and don't know it took 8 min. for the light to travel to earth? -Or is this not what you meant, and you're implying something about someone going very fast (and not on earth) and so their sense of time is different from ours on earth?
quote:That is, something can happen on the sun, and someone on Mercury will see it "first", and someone on earth will see it "second", even though it's the same event.
I think I'm beginning to see the problem with thinking this way. This way kind of includes some implied "standard time" of the universe, which doesn't really exist.
It's not so much that the even happend, and Mecury saw it 'first' and Earth saw it 'second' so much that:
An event happened. Mercury detected the event 4 min. after the event happened. Earth detected the event 8 min. after the event happened.
This way there's no restrictions, and no implied foundational time-line.
I still find the 'doppler effect with time instead of sound' to be helpful to myself, but I will have to focus on remembering that everything has it's own independent, um... timeline.
Okay, I understand then. This was more of a terminology issue then a concept issue.
Seeing the explosion may be in my future (in a destiny sort of sense), but the event itself is not in the future, because it's already happened. I understand that.
Its the latter. They need both the appropiate speed and direction....
I think I understand this as well. Say they are travelling at some sufficient speed and direction that they "see" the clap from earth 4 min. after they "see" the explosion on the sun? I can visualize that, if the answer is yes. Or am I still not understanding the concept?
if the explosion occured, and we're watching it with our telescope, and we are going to see it, when the photons reach earth... how is it not in our future?
Because the event has already happened.
Wait... if what you say is true, then no one really has any "future" whatsoever. Since everything happens in some sort of "elsewhere" (no matter how miniscule) before the light photons hit our eyes and we detect the event.
Whether it's an explosion on the sun, and it takes 8 min for the light to reach us. Or it's an explosion right in front of us, and it takes 0.0000023whatever seconds for the light to reach us.
If what you say is true, neither case is in "our future" because the events happened before we saw them. Therefore, nothing at all is in "our future" because all events take some amount of time for us to detect them.
So, if that's true, what is meant by the "future" light cone?
That is, if I can't say that light from an explosion on the sun is in our future (if I'm eventually going to see it), what can we say is actually in the future light cone?
Or is that the catch? I can say that the "light" from the event is in our future, but not the event itself?
If so, then that's some more terminology confusion I just needed to understand, and that fits the concept I already have.
This would make sense... hence the term "future light cone" :)
But what about things that haven't happened yet? They would still be in the future.
Yes, thanks. I was still getting confused between the difference and co-existance of "the future" and a "future light cone". I wrongly assumed that it was either one or the other, sort of a classical vs quantum type thing. It's not that the relative mind-set only has a "future light cone", it just also has one.
I think I'm better now, thanks to you and all the others for indulging my ramblings.
Einstein's Special Theory of Relativity introduces us to the concept of time as a dimension, very similar to our three spatial dimensions. (The clue to this was in Maxwell's Equations of electromagnetism, which could be written in exceptionally simple form once time was treated as the fourth member of the (x, y, z ) set.)
Just to be clear, YOU agree with this concept (emphasis on concept) that time is very similar to our three spatial dimensions?
All four dimensions are merely measurements, they measure in increments we have standardised so as to make sense of the Cosmos we are part of.
But both space and time are not in themselves 'things'.
I completely agree.
V-Bird and cavediver said the same thing. Why do you have a problem with what cavediver said, yet agree with what V-Bird said?
I don't understand. One says all 4 dimension are basically the same thing, the other says all 4 dimensions are very similar.
I'm really not the one to be arguing this sort of thing, but I think that both V-bird and cavediver are saying pretty much the same thing:
Space (spatial dimensions) and Time are both real things.
However, our human-measurements of those real things are man-made concepts and not necessarily perfectly accurate representations of those things. This would be because our information is imperfect, and our senses are limited.
I don't think cavediver's saying that time is a linear measurement of space. I think that cavediver's saying that time is a linear measurement of a property of our universe the same way that the spatial dimensions are linear measurements of properties of our universe.
Those 'properties of our universe' (or 'properties of things in our universe') are real things, and the measurements are human-concepts that are our best-method-available (right now) to try and describe those real properties of objects in this universe.
That's how I see it, anyway. But, really, I don't have the background knowledge required to argue what I think cavediver or V-bird is saying. I could very well be misinterpreting them myself. It's probably best that I bow out of this particular arguement.
I have no questions and have no problem visualizing everything you posted and talked about.
I'm going right back to basics to destroy this common perception of 'physical'. It's precisely this approach that recently helped Agobot go rather gaga in his nihilism phase And we'll soon get to the point where Holmes was once accusing me of trying to 'fuck with his mind'
None of that to worry about with me. At least not yet, anyway :)
Quick question about tunneling..
I understand that there is some actual minute possibility of 1 tunneling thing (partical? quark? light photon? I'm not sure of the terminology here...) to go right through, say, a brick wall. I have no issue with this, and can visualize it and it makes sense to me.
Is there some actual minute possibiliy of something larger possibly passing through a brick wall? Like, say, me.. or a car, or whatever?
I would like to say "no" because I think the fields connecting everything would prevent this. Those fields would have to be broken first, and then the me or car or whatever isn't a me or a car or a whatever anymore.
Does this make sense? Or am I not thinking of things correctly?
[Tunneling] is possible for electrons, even atoms, and actually even molecules in the right extreme conditions.
I don't want to take you off course but, could you give an example of "the right extreme conditions"?
Take this with a grain of salt, but here's my thoughts:
But the wavefunctions of large objects are forced to have extremely small extent because of the practically inifnite interactions with the wavefunctions of the practically infininte number of other particles around us. This is decoherence.
Therefore, "the right extreme conditions" would be things like: -a near vacuum (other than the tunnel-er and the tunnel-ee, of course) -near absolute zero -both? -a bit of "luck" to hit (enter?) the object at just the right spot
Those are my guesses, for what they're worth. (and I wanted to bump this thread :))
I think I understand what you're saying. I do want to point out one thing though:
I do not know of any real world examples where you could observe this interaction however, since any observation would cause a collapse of the wave function and your back to classical view of reality where the two objects will interact with each other.
I'm not assuming that any of the scenarios I mentioned were being observed in any way. In fact, I was assuming they were all necessarily unobservable. In the sense of "it could happen... but we wouldn't be able to observe it happening".