# Intriguing question about Time, Physics and SRT in general

Please, no more of this stupid "t=0 duration" crap, that's not what the light cone says.

We can hope, but I fear our hopes will come to naught.

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We can hope but I fear out hopes will come to naught.

But the forum says he only last posted at 7:00pm, how can he exist now?

No, no, and no. There's no need to invoke even more complicated ideas to resolve a simple misunderstanding. If you can't even understand light cones, it's ridiculous to go further still and try relating them to quantum entanglement or de Sitter spaces. Your questions about time could be asked of classical Newtonian physics just as easily, and you could raise the exact same illogical objections. The oberver exists over a finite nonzero duration of time, and the light cone represents the points where events occuring at various times can affect them or be affected by them, given that no information can be carried from one event to another faster than light. Please, no more of this stupid "t=0 duration" crap, that's not what the light cone says.
Sorry to disagree, but I feel you seriously underestimate the significance of the light cone diagram as it relates to Minkowski/Einstein space time...and physics in general.
I believe that the cone diagram is central the understanding of GR, SRT, and the universe in general. It is far more than what you suggest it to be.
I quote:

A light cone is the path that a flash of light, emanating from a single event (localized to a single point in space and a single moment in time) and traveling in all directions, would take through spacetime. If we imagine the light confined to a two-dimensional plane, the light from the flash spreads out in a circle after the event E occurs, and if we graph the growing circle with the vertical axis of the graph representing time, the result is a cone, known as the future light cone. The past light cone behaves like the future light cone in reverse, a circle which contracts in radius at the speed of light until it converges to a point at the exact position and time of the event E. In reality, there are three space dimensions, so the light would actually form an expanding or contracting sphere in 3D space rather than a circle in 2D, and the light cone would actually be a four-dimensional version of a cone whose cross-sections form 3D spheres (analogous to a normal three-dimensional cone whose cross-sections form 2D circles), but the concept is easier to visualize with the number of spatial dimensions reduced from three to two.

Because signals and other causal influences cannot travel faster than light (see special relativity and quantum entanglement), the light cone plays an essential role in defining the concept of causality: for a given event E, the set of events that lie on or inside the past light cone of E would also be the set of all events that could send a signal that would have time to reach E and influence it in some way. For example, at a time ten years before E, if we consider the set of all events in the past light cone of E which occur at that time, the result would be a sphere (2D: disk) with a radius of ten light-years centered on the future position E will occur. So, any point on or inside the sphere could send a signal moving at the speed of light or slower that would have time to influence the event E, while points outside the sphere at that moment would not be able to have any causal influence on E. Likewise, the set of events that lie on or inside the future light cone of E would also be the set of events that could receive a signal sent out from the position and time of E, so the future light cone contains all the events that could potentially be causally influenced by E. Events which lie neither in the past or future light cone of E cannot influence or be influenced by E in relativity.
re: http://en.wikipedia.org/wiki/Light_cone

To me, the main point of the light cones is to differentiate between past and future light events and in doing so declare that absolute rest is impossible due to the HSP having no time duration. It is also declaring in essence that the universes reality is based on an event horizon of continuous movement. [thanks for the reminder Brudep ]
the emission of a ray of light being the base line for all events universally...

It is worth some serious study... beyond what you have implied IMO.

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But the forum says he only last posted at 7:00pm, how can he exist now?
good question!!

But the forum says he only last posted at 7:00pm, how can he exist now?

Sweet freaking Jesus, your right! It really is rather funny (in a sad sorta way) that QQ is all smug thinking he has found some sort of paradox to confound the experts.

Sweet freaking Jesus, your right! It really is rather funny (in a sad sorta way) that QQ is all smug thinking he has found some sort of paradox to confound the experts.
Certainly some of the "pseudo wanna-be experts" on this board perhaps, but certainly NOT the real experts that constructed the theories, such as Einstein, Minkowski, De Sitter, Lorentz etc...and later Feynman and others...
They have indeed got solutions to my questions and it is those solutions I wanted to explore...and wished to invite those interested to share the journey...

That little pop you heard was you blowing QQ's mind.

You good me good origin. I just spewed coffee on the screen reading this, wiped it off, took a swig, scrolled down and spewed again. You two are on a roll. Whatever QQ is saying obviously doesn't matter. (I have him on Ignore.) You see, in my reference frame he really does not exist at all. Maybe this should be in the Religion forum, under Buddhism or something, since I find myself laughing over the nonexistence of a person going crazy over the meaning of zero duration. Gawd. that just blew my own mind!

But you aren't going on the journey, you're doing physics by random-quote + fantasy.

But you aren't going on the journey, you're doing physics by random-quote + fantasy.
and I suppose you believe your opinion matters! Why ?
I have no reason to hold your opinion with any real value...

"The evidence of value is in the substance of your posts not your flame and egoistic calls to some sort of authority."

Gawd. that just blew my own mind!
Don't tell me! ...you are a clandestine member of CRI?

But you aren't going on the journey, you're doing physics by random-quote + fantasy.

Call it fantasy travel. Interactive, with some people who actually studied some of the material to rib you for being a dolt. Ever so slightly masochistic physics, as opposed to the more sadist forms some of us sweated through. (Thermogoddamits anyone?)

Don't tell me! ...you are a clandestine member of CRI?

And the Dunning and Kruger experiment continues.....

And the Dunning and Kruger experiment continues.....
too bloody right... this thread is full of it... [chuckle]

This is interesting regarding the HSP:
from http://www.pitt.edu/~jdnorton/teaching/HPS_0410/chapters/spacetime/

quote:
The remaining region of the spacetime is outside both past and future light cones. It is a new sort of region that does not appear in pre-relativistic spacetimes. It is an "elsewhere" region.

It collects all events that cannot be connected to event O by timelike or lightlike curves. Its events can only be connected to O by spacelike curves. That is, its events are "spacelike separated" from O.

If we assume that no causal processes propagate faster than light, these events are causally disconnected from O. If we are at O we cannot causally affect or be causally affected by an occurrence at an event in this "elsewhere" region. Correspondingly, we cannot exchange signals between the event at O and any spacelike separated event in this region.

There is no corresponding region in a pre-relativistic spacetime. In Newtonian theory, it is assumed that there are propagations that are arbitrarily fast and even instantaneous. An example of an instantaneus propagation is changes in the Newtonian gravitational field. If the sun were to disappear, we would know instantly on earth, according to Newtonian theory, for the sun would no longer exert a gravitational pull on us.

Sorry to disagree, but I feel you seriously underestimate the significance of the light cone diagram as it relates to Minkowski/Einstein space time...and physics in general.
I believe that the cone diagram is central the understanding of GR, SRT, and the universe in general. It is far more than what you suggest it to be.

And I believe, based solely on what you've posted here, that you have no idea what the light cone represents or how one determines its size. Yes, light cones are important to the understanding of Relativity; no, they have nothing to do with your claim that observers don't exist. You throw around names like Minkowski as if I'm supposed to believe you have any clue what Minkowski spacetime represents, so why don't you tell us in your own words what Minkowski spacetime is and what its key properties are under translations, rotations and boosts?

To me, the main point of the light cones is to differentiate between past and future light events and in doing so declare that absolute rest is impossible due to the HSP having no time duration. It is also declaring in essence that the universes reality is based on an event horizon of continuous movement. [thanks for the reminder Brudep ]
the emission of a ray of light being the base line for all events universally...

To me, nothing you've written makes me believe you're in a position to making any assertions about physics whatsoever, and I'm not saying that as a putdown, I'm saying it because you're being arrogant and assertive about things you clearly don't understand (and clearly haven't tried very hard to understand). An observer's individual light cone does not represent the state of the universe's "reality", it represents the relationships between causes and effects at given times in the past, present and future, as they relate to that particular observer. The light cone shrinks to zero size at the observer's "present" time, because any other event in the universe happening at that same exact moment would have to send signals infinitely quickly in order to have an effect on the observer at that moment, or to be instantly affected by whatever the observer is doing.

Furthermore, light cones don't make an absolute differentiation between past and future, other than as seen by individual observers. Any two events with spacelike separation can have their orders of occurrance reversed depending on the reference frame observing them, and there's no contradiction here because the speed of light limit prevents spacelike events from being causally connected.

It is worth some serious study... beyond what you have implied IMO.

Please do some serious study then and stop making mindless, ignorant assertions about light cones you don't understand. Go learn physics from the ground up (yeah, fat chance you'd ever be humble or eager enough to bother with that), and then this stuff will actually start making sense to you. Please stop spouting this mindless crap about observers only existing for infinitesimal durations, because that's not what physics says and that's not what light cones imply.

In a nutshell, here is what the light cone says: If an event occurs a billion light years away, it's going to take at least billion years before you can witness any evidence of it having occurred. When you do finally receive that evidence, the event that caused it will then be in your past light cone from that time onwards. Conversely, if an object is a billion light years away, and you send a signal towards it today, the signal and anything else you do today won't affect them for at least a billion years, so the eventual receiver will be in your future light cone, starting from a billion years in the future and onward.

Please stop spouting this mindless crap about observers only existing for infinitesimal durations, because that's not what physics says and that's not what light cones imply.
Support your complaint with a quote please.. and if not apologize for false representation...
[rpenner and others had thoroughly and very reasonably refuted that consideration in another thread and it has no bearing on this thread except to state that infinitesimals are irrelevant.]

Support your complaint with a quote please.. and if not apologize for false representation...
[rpenner and others had thoroughly and very reasonably refuted that consideration in another thread and it has no bearing on this thread except to state that infinitesimals are irrelevant.]

Here's a quote for you:

If the time duration between past and future, light cones, is zero then what mathematics can be used to describe the reality of the universe [ or any relevant observer frame of reference ] at that point in time?

That's from your opening post. Obviously you wouldn't be crazy enough to believe observers don't exist, but your claim and subsequent statements imply that you think this is an inevitable conclusion derived from Relativity unless we all agree to replace it with some stupid metaphysical layman model. And if your conclusion is indeed that Relativity and light cones somehow imply that observers don't exist, then you simply don't understand what light cones actually represent.

Now back to you. You threw the term "Minkowski spacetime" out there for us as if we were to believe you knew what you were talking about, so now I'd like you to tell us what's significant about the Minkowski metric in Relativity and how it transforms under translations, rotations and boosts. Don't worry, I'm not quizzing you here; the transformation properties of the Minkowski metric contain very important implications for light cones and their associated causal structures, so I'd like you to demonstrate for everyone that you have at least some clue what you're talking about.

too bloody right... this thread is full of it... [chuckle]

You're the prime candidate.

Here's a quote for you:

Originally Posted by Quantum Quack View Post
If the time duration between past and future, light cones, is zero then what mathematics can be used to describe the reality of the universe [ or any relevant observer frame of reference ] at that point in time?
That's from your opening post. Obviously you wouldn't be crazy enough to believe observers don't exist, but your claim and subsequent statements imply that you think this is an inevitable conclusion derived from Relativity unless we all agree to replace it with some stupid metaphysical layman model. And if your conclusion is indeed that Relativity and light cones somehow imply that observers don't exist, then you simply don't understand what light cones actually represent.

As much, as I wish I could agree with your paranoia, and I can not.

I am NOT disputing the validity of SRT.
I am not disputing the validity of the light cones diagrams.
You seem to feel that I am or am attempting to or am conspiring to, but I am not.

Years ago under the tolerant guidance of JamesR and Pete and various other astute and I might add patient members of sciforums and after doing exhaustive thought experiments many time over, including the various forms of the twins pseudo paradox, countless spread sheets and endless diagrams, I came to the personal conclusion that SRT was utterly sound logically given the premises that it worked from. Subsequently I had given up many years ago, attempting to refute SRT.
But you would not know this...if you knew me back before the paranoia about defending SRT became extreme.

The OP suggests that in a single instant of hsp zero duration time an observer can not exist.
I'll write it again so it is clear:
The OP suggests that in a single instant of hsp zero duration time an observer can not exist.
And this is confirmed by the light cone diagram.

However as ludicrous as it may appear to the paranoid, the observer does indeed exist but only as Brucep has suggested because the observer is a part of a continuum of time. The observer stands on a continuous event horizon. It is only because there is a continuum of **time (flowing) that allows the observer a universe for him to observe. **movement

However as the light cones diagram suggests:
For a single instant of zero duration time an observer and his universe would be non-existent.

Of course this in no way attacks the credibility of the author of the diagram [Minkowski] nor the application of it by Einstein and others in redefining contemporary physics.

To be honest when I first found this diagram about [12years ago] I was utterly staggered by the sheer brilliance involved in it's creation.. and I still am...for reasons that go way deeper than the typical and superficial view of them. In fact it was the diagram that brought me to sciforums to begin with if I recall correctly.