# Event Space

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#### topsquark

Forum Staff
Perhaps if Topsquark thinks the discussion should be held elsewhere he might move it for us.
Yup, I moved it. It's now in the Relativity Forum.

-Dan

#### Woody

You can probably guess that I was trying to link the "cause and event" topology,
which originates in Einstein's quite rigidly deterministic universe
with the fuzzier world of QM.

I have just read an article in new-scientist <in the quantum realm cause doesnt necessarily come before effect>
which suggests that, in certain very specific circumstances, it would appear that cause and effect can occur in reversed time!

I am floundering for a way in which the sharply defined causal links of relativity
might be shown to be an approximation to (or perhaps an idealization of) the fuzzier causal links found in QM.

topsquark

#### studiot

I am floundering for a way in which the sharply defined causal links of relativity
might be shown to be an approximation to (or perhaps an idealization of) the fuzzier causal links found in QM.
This distinction is quite a good way to put it, although time is never actually reversed and in relativity the causal sequence is the same in all frames, fixed by network of invariant links of the (minkowski) interval.

But don't forget the uncertainty principle in QM.

One way to look at this is that it is due to the order in which two measurements are taken.
So if you measure energy first then time you will get a different result (differing by the uncertainty) from measuring time first then energy. (Or any of the other pairs of variables).
This is because these variable pairs are not commutative.
This is not so very different from measuring first the voltage and then the current or the other way round first the current then the voltage in a circuit in classical Physics. You cannot measure these together either.

Woody and topsquark

#### Woody

and I think that it is actually suggesting that (in particular special circumstances) a superposition of states
(as produced by having two possible paths in space as in for example the double slit experiments)
can be obtained by providing two possible routes that are displaced in time.
e.g. does a photon go through Gate A first and then through Gate B, or through Gate B first and then through Gate A?
Apparently experiments have been performed that seem to suggest, the photon can do both (as with the double slit experiments)
The experiments are difficult to set up, and thus the results are not (yet) 100% firm, but the idea is intriguing.

topsquark

#### studiot

As I understand these experiments and the double slit in particular, if you look for a particular action(better not use that word it has a special meaning) activity you will find it. Lokk for a wave and you will observve wave properties. Look for a particle and you will observe 'photons'. This does not imply (as some eg Penrose suggest) volitional control.

#### GatheringKnowledge

You can probably guess that I was trying to link the "cause and event" topology,
which originates in Einstein's quite rigidly deterministic universe
with the fuzzier world of QM.

I have just read an article in new-scientist <in the quantum realm cause doesnt necessarily come before effect>
which suggests that, in certain very specific circumstances, it would appear that cause and effect can occur in reversed time!

I am floundering for a way in which the sharply defined causal links of relativity
might be shown to be an approximation to (or perhaps an idealization of) the fuzzier causal links found in QM.
I'm not sure, if it's possible to define an "event space" without the inclusion of time in any form. What makes the quantum reality so fuzzy, is that in the difference to Einstein's theory, all what determines the occurence of events, is the probability of their occurrence at a given location and at a specific moment of time. Because of the nature of probability in QM, nothing can be certain in absolute terms, as everything, what we observe, is just the most possible outcome. But once the wave function of probability collapses into a specific state, observed result is permanently "written" into spacetime and becomes a definitive history, which is shared among all observers. All what remains relative in timeline, after the collapse of probability distribution, is how determined events are being perceived in different frames - but in any case, their logical order will be maintained for all observers, so it will possible to trace them back to original states, which were observed after the initial wave function collapse.

Since in QM probability never reaches 0% or 100%, before a direct measurement of state is taken, there's a tiny possibility, that an event, which suppose to take place as a result of an other event can precede it's own cause - we just don't observe it in real life, because it's probability is too low, to actually take place. But in case of a photon, which passes through double slit, probability remains at 50% to 50%, until light won't reach a projection screen. Theoretically it's possible to artificially manipulate the probability of a wave function at quantum scale and collapse it into an "impossible" state - but in nature it has to be extrely rare and obviously doesn't affect physical processes at macroscale. If you want to use those rules to describe processes observed at larger scales, you have to include density of probability in space. Probability of an electron is much less defined, than probability of an atom, while molecules are determined in space and time even more. Now just keep scaling probability distributiion to objects at macroscale and you will understand why observed processes appear to us, as fully determined in time.

In another post, I will try to explain, how much such representation of space and time differs from the one, which is proposed in Einstein's model of relativity...

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#### GatheringKnowledge

As I understand these experiments and the double slit in particular, if you look for a particular action(better not use that word it has a special meaning) activity you will find it. Lokk for a wave and you will observve wave properties. Look for a particle and you will observe 'photons'. This does not imply (as some eg Penrose suggest) volitional control.
You can look for an activity and don't find any, if the probability of occurence at the time & location of measurement, is too low. You can for example look for socks in a drawer, but you won'rt find them there, if they are inside a washing mashine at this time. What differs a photon from socks, is how much it is determined in spacetime - possibility of an outcome becomes much more uncertain at the smallest scales of reality. There's 50% chance for a photon, to pass one slit from two, so you have 50% chance, to find it on one side of space between the slits and a screen - but once you'll find out, if a photon is there or not, it's motion path won't be a probability anymore and it will start to behave like a particle. However, probability of finding that photon on Mars, is too low, to find it there (in 99,99999% of all cases)

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#### Woody

My personal interpretation of the QM probability is that
the inclusion of a wider spread of interactions with a wider spread of other QM entities,
introduces tighter constraints of the probability function.

If the probability function is tightly constrained, then a particle model can be used to describe the behavior.

If the QM entity being tested is only lightly interacting with other QM entities (in the wider universe)
then its probability function is only lightly constrained,
and the probability wave function model needs to be applied in order to successfully describe its behaviors.

donglebox

#### studiot

Woody, Can you give an example of what you mean ?

#### Woody

Probably not, my ideas are a bit nebulous, however I will try...
The position of an isolated electron seems to be fairly free to be quite widely defined,
e.g. it can simultaneously go through both slots of an interference grating.
However an electron that is forming part of an atom has a quite constrained position (close to the atom).

The isolated electron, having been at a widely defined position through most of its journey (through both slots)
gains a clearly defined position when it interacts with the atoms of the screen.

As an item becomes more macroscopic, such QM features as superposition of states become less readily achievable.

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