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Messages - kurros

1
Choose Your Own Topic / Re: a nice Sean Carroll interview
« on: Today at 10:14:26 am »
SN1885 was inside Andromeda.

Ahh well then vice versa re. Andromeda vs Milky Way observers. Except I guess we saw it since we know about it. So my comments apply to some time before 1885 Earth observers then ;).

2
Choose Your Own Topic / Re: a nice Sean Carroll interview
« on: Today at 08:14:16 am »
He can, but that determination will only be true in that frame of reference. There is nothing objectively special about that choice, so no grounds for him to claim that his determination is the "One True Correct causal ordering". The objective truth is that causal ordering is indeterminate outside light cones.

So, outside of our light cone the supernova SN1885 didn't occur 2.2 million years ago to observers in M31 (i.e., in their rest frame)?

Our rest frame is almost identical to that of M31 (our galaxies are not moving very fast relative to each other), so if we each calculate how long ago that supernova occurred in our respective rest frames then we will get very similar answers. However in M31, assuming the light from SN_1885 hasn't actually reached there yet so it is outside their light cone, it will also be possible to boost to reference frames where SN_1885 hasn't even exploded yet. No-one in M31 can have taken any actions on the basis of SN_1885 exploding yet, because it is impossible for them to know that it has exploded, and indeed from the point of view of some boosted observers in M31, it hasn't.

3
Choose Your Own Topic / Re: a nice Sean Carroll interview
« on: Today at 07:41:36 am »
Then why can't Charlie use the M31 rest frame to determine his temporal relation with Alice?

He can, but that determination will only be true in that frame of reference. There is nothing objectively special about that choice, so no grounds for him to claim that his determination is the "One True Correct causal ordering". The objective truth is that causal ordering is indeterminate outside light cones.

4
Choose Your Own Topic / Re: a nice Sean Carroll interview
« on: Today at 06:52:16 am »
So it doesn't matter how precisely you measure in your reference frame. Time still physically passes at different rates in other reference frames. It's not an issue of counting more accurately, this is a physical effect.

So is it possible for M31-ians to believe the universe is 6,000 years old and be correct? Hm. That provides a lot of opportunity for people like Krav to argue that Genesis is right about creation.

Only if they specify the reference frame that they are talking about. This is the point of relativity, time is relative, so you cannot speak of any absolute amount of time passing. You must specify the reference frame in which is passing. Anyway this age of 6000 years won't be true in the rest frame of M31, which would seem to be the sensible "default" for them to use. But there does exist some other reference frame where the universe is 6000 years old, sure. If you boost fast enough then time dilation can compress 13 billion years into 6000 years. This is a rather high gamma factor, about 2 million, so you have to travel at about 0.9999999999998c relative to M31 to achieve this (for reference LHC protons are only boosted to about gamma=7000, so we are talking about some serious boosting). But in principle this reference frame exists.

5
Choose Your Own Topic / Re: a nice Sean Carroll interview
« on: Today at 12:54:52 am »
I'm not sure what you mean. If they are outside each others light cones when they do their experiments, which is the case so long as a message cannot have last been sent from one to the other in the spacetime interval separating the events, then their temporal ordering is reference frame dependent regardless of what prearrangement trickery you might try to cook up.

Charlie is able to determine with some degree of preciseness when the M31 collision will take place and therefore backtrack how many years have passed on earth and then calculate with reasonable accuracy how much time has passed for Alice since he departed. Of course it might not be ultra-precise but like I said the thought experiment doesn't require this kind of preciseness. For example, even on Andromeda their scientists might know that the universe is 13.7 billion years old. They might even have far higher accuracy than us.

These calculations are only relative to clocks in a particular reference frame. Different amounts of time pass in different reference frames. Even the universe is only 13.7 years old when calculated in a certain reference frame (though that one adds even more complexity because the expanding universe requires us to consider general relatively, not just special relativity).

So it doesn't matter how precisely you measure in your reference frame. Time still physically passes at different rates in other reference frames. It's not an issue of counting more accurately, this is a physical effect.

6
Choose Your Own Topic / Re: a nice Sean Carroll interview
« on: November 14, 2019, 03:46:16 pm »
Sure, but that timing is only in one particular reference frame. In other reference frames there were different time intervals between their experiments, and the experiments can even have occurred in a different order. Temporal ordering is only definite when events lie within each others past/future light cones. Otherwise the ordering depends on reference frame.

I don't think my thought experiment requires exact precision anyway. In addition, Charlie in M31 and Alice1 in the Milky Way galaxy can calculate the exact time (within minutes or seconds) when M31 will collide with the Milky Way galaxy and use this benchmark to determine that Charlie's experiment follows Alice's experiment. They can predecide this before he departs to M31.

I'm not sure what you mean. If they are outside each others light cones when they do their experiments, which is the case so long as a message cannot have last been sent from one to the other in the spacetime interval separating the events, then their temporal ordering is reference frame dependent regardless of what prearrangement trickery you might try to cook up.

7
Choose Your Own Topic / Re: a nice Sean Carroll interview
« on: November 14, 2019, 02:43:02 pm »
Actually I guess I should have mentioned the relativity of simultaneity thing earlier. We must remember that events occurring outside light cones have no definite causal ordering. So we cannot even definitely say that Alice did her experiment before Charlie. It seems clearly that way in the rest frame that we chose, but there exist other reference frames where the apparent temporal order is reversed.

I forgot to mention that Charlie is from the same planet as Alice and Bob. They went to earth and Saturn and he went to Andromeda. They sent daily messages to each other. The messages became more and more delayed, but both made the needed adjustments so that they always received at least one message a day to the other. Unfortunately a few hours before they did their experiments Charlie's radio in M31 broke down. Alice was aware that he was having trouble but it didn't effect their timing to do the experiment in Nov, 2019.

Sure, but that timing is only in one particular reference frame. In other reference frames there were different time intervals between their experiments, and the experiments can even have occurred in a different order. Temporal ordering is only definite when events lie within each others past/future light cones. Otherwise the ordering depends on reference frame.

8
Choose Your Own Topic / Re: a nice Sean Carroll interview
« on: November 14, 2019, 01:06:57 pm »
In some places the universe is split in two, and those branches can't talk to each other anymore, but other places are still "combined" in one branch and can send signals to both branches somewhere else.

Let me ask it this way: If Charlie1 builds a black hole bomb and detonated M31 and completely destroys it before his wavefront reaches Alice1, but Charlie2 doesn't build the bomb, then does M31 exist in Alice1's world before CW1-CW2's wavefront reaches Alice1. The question is meaningless because there is no "now" at M31 as far as Alice1 is concerned. The fixed reality of M31 does not exist until the wavefront from M31 reaches her, and "now" is 2 million years from now (since it takes the wavefront 2 million years to reach earth). Hence, it's wrong to say M31 exists and non-exists. It's just a meaningless question (like "what is time is it if there is no time?").

Well there is no such thing as a universal "now" in relativity at all, quantum mechanics aside. There are only past/future light cones. And this gravity bomb destruction of M31 is outside of the past light cone of both Alices. So it cannot even be said to be definitely in the past for her yet (she can still boost to a reference frame where Charlie hasn't destroyed M31 yet, indeed she can boost to one where Charlie hasn't even split yet). The destruction of M31 doesn't enter Alice's past light cone until some time after she gets split by Charlie's wavefront. After which point it is clear that the Alice in Charlie1's branch is the one who sees M31 get destroyed.

Actually I guess I should have mentioned the relativity of simultaneity thing earlier. We must remember that events occurring outside light cones have no definite causal ordering. So we cannot even definitely say that Alice did her experiment before Charlie. It seems clearly that way in the rest frame that we chose, but there exist other reference frames where the apparent temporal order is reversed.

9
Choose Your Own Topic / Re: a nice Sean Carroll interview
« on: November 14, 2019, 12:46:51 pm »
She splits, each one meets a different Charlie. Subjectively it seems random to each of them which Charlie they meet, but there is nothing random about it, Alice's subjective experience just branches deterministically along with the worlds.

Understood, but there is only one Charlie1 and two Alice1s. Alice11 is identical to Alice1 (same entity) but Alice12 is a duplicate in the same way a copying machine makes a copy.

Although, this point is not that important. The important point is that Alice1 before splitting into CW1 and CW2 thinks of M31 as "there" and having a particular state of affairs. But, since Charlie's split wavefront has not reached her yet, there is no M31 in her "now." That is there is no channel 3 thing called M31 for those 2 million years as we wait for Charlie's wavefront to reach Alice. Thus, if we apply this universally for all areas far outside of Alice's wavefront, we're looking at a philosophy that says there is nothing on channel 3. It is pure static except for nearby phenomenon. Again, that's not worth the cost of whatever denying action-at-a-distance buys you. Since SRT is not contradicted by action-at-a-distance there really is no reason to entertain such a non-parsimonious metaphysics as local MWI requires. Wheeler rightly scoffed at it, and Everett rightly was told to shelve this metaphysics. He probably didn't deserve all of the bad reaction and ridicule he received, but clearly it is a hell-bent metaphysics if it requires that most of universe has no "there" there.

But what you are saying just isn't the case. It's not "static" out there. If a star explodes out there somewhere, the light from the explosion will still propagate to Alice and she will see it. It doesn't make sense to say that it isn't part of her reality. Rather than channels I really think you are better off sticking with the branching metaphor. In some places the universe is split in two, and those branches can't talk to each other anymore, but other places are still "combined" in one branch and can send signals to both branches somewhere else.

10
Choose Your Own Topic / Re: a nice Sean Carroll interview
« on: November 14, 2019, 11:47:21 am »
Oh I see. It's not actually a meaningful question I think. First, there is no "original", both Alices were the same person in the past, before the split. She splits, each one meets a different Charlie. Subjectively it seems random to each of them which Charlie they meet, but there is nothing random about it, Alice's subjective experience just branches deterministically along with the worlds.

11
Choose Your Own Topic / Re: a nice Sean Carroll interview
« on: November 14, 2019, 10:52:35 am »
Well if AW2 dies then the world containing her corpse is still split by Charlies wave, and AW1 also splits into one Alice who meets Charlie1 and another who meets Charlie2.

The point is that there is a way to identify which Alice is original and which is a duplicate. The original one is the timeline where Alice could have died whereas the duplicate world can only make copies of that original Alice.

In any case, local MWI has no way of determining which Charlie that Alice1 meets. It's random which means that all of these "Charlie worlds" are not "real" until those wavefronts reach Alice. This means that there is no fact of matter as to what is happening right now in Andromeda (M31). That depends on which world matches up with our light cone, and that is then only randomly determined. However, "right now" there is no M31. Some might consider that too big a price to avoid action-at-a-distance which doesn't even violate STR anyway.

What? I don't know what you are thinking. Alice can die on any branch, there is no special branch, nor any randomness.

12
Choose Your Own Topic / Re: a nice Sean Carroll interview
« on: November 14, 2019, 09:38:37 am »
There is no "original" Alice1. Alice1 and Alice2 and all other Alices have equal status. And both Alices meet both Charlies, there are four branches in the end. So we end up with four Alices.

Suppose Alice dies in AW1/AW2 before Charlie's wave reaches her, then we can define the original Alice as the one who was living when AW1 split from AW2.

Well if AW2 dies then the world containing her corpse is still split by Charlies wave, and AW1 also splits into one Alice who meets Charlie1 and another who meets Charlie2.

13
Choose Your Own Topic / Re: a nice Sean Carroll interview
« on: November 14, 2019, 08:11:42 am »
Yes Alice1 splits into two; one who meets Charlie1 and another who meets Charlie2. It doesn't matter that the AW1/AW2 split occurred 200 million years ago, the Charlie splitting is in the past causal light cone of both Alices (it has entered that light cone just now, as the splitting wavefront reaches Alice). So they are both split by this event.

But wrt the original Alice1 (not the duplicate) which Charlie does she meet? Is it random (indeterministic)? It seems random.

There is no "original" Alice1. Alice1 and Alice2 and all other Alices have equal status. And both Alices meet both Charlies, there are four branches in the end. So we end up with four Alices.

14
Choose Your Own Topic / Re: a nice Sean Carroll interview
« on: November 14, 2019, 07:39:03 am »
But, which Charlie (CW1 or CW2) will the Alice1 who first branched into channel 3 [from channel 2] meet? You seem to be saying that *she* will meet both Charlie1 and Charlie2, but CW1 and CW2 split Alice1 200 million years *after* her Nov 10 experiment with Bob. These are all duplicates and not the original Alice1 (whom you fell in love with). Who does the original Alice meet? Charlie1 or Charlie2?

Yes Alice1 splits into two; one who meets Charlie1 and another who meets Charlie2. It doesn't matter that the AW1/AW2 split occurred 200 million years ago, the Charlie splitting is in the past causal light cone of both Alices (it has entered that light cone just now, as the splitting wavefront reaches Alice). So they are both split by this event.

15
Choose Your Own Topic / Re: Do “trans” characteristics support dualism?
« on: November 14, 2019, 04:09:45 am »
@wonderer
I'm not using "offendability" as a criterion for picking metaphysics, I just wanted to highlight the entailments (or ethical baggage in this case) of a property dualist account of gender. Most trans people have very strong feelings that their true gender is not physical. I suspect if we were to invite a trans person on this thread, they would likely subscribe to substance dualism or some other account that sees gender as foundational to a person, rather than emergent. I think we should take that opinion seriously, which I think - going back to the OP - might give us a reason to consider the merits of substance dualism. Are you saying that perhaps we shouldn't take these opinions seriously until we have independent reasons to think substance dualism is plausible?

I'm not really seeing the ethical baggage you are talking about.  I'm not (to pick a nonrandom example) a chaplain in the US military who is in some sort of authority over anyone I might have such a discussion with.  I'm just some dude with my own perspective on things.

Of course, I'm not going to go seek out trans people and proselytize for physicalism, but supposing someone came here and insisted that they had a soul that was meant for a body different than the one they were born with, I would certainly question their reasoning for that claim.

Indeed this feeling of "having the wrong body" just sounds to me similar to other body-related psychological problems people have. For example some transplant patients end up having severe problems accepting the foreign organ as part of "their" body, especially highly visible ones like hands. The first human hand transplant ultimately failed because the patient was unable to psychologically accept the hand as "theirs". And there are cases of people having these feelings even "without" a transplant, i.e. they just feel strongly that some of their limbs are "not theirs" and have a strong desire to cut them off (xenomelia). I don't know if trans-ness has a similar cause to these things, probably no-one knows yet, but these sort of things certainly do exist.

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