11 ms·

"c" isn't "the speed of light" so much as "the speed of causality". Light just happens to be massless packets of energy that move at the speed of causality. F

"c" isn't "the speed of light" so much as "the speed of causality". Light just happens to be massless packets of energy that move at the speed of causality. For all intents and purposes this is happening in real time from our local frame of reference. https://youtu.be/msVuCEs8Ydo https://youtu.be/msVuCEs8Ydo

rhaway84773 4y ago
Realizing that most often when we discuss the speed of light we’re not actually discussing the speed of light, but rather the speed of causality, was a huge eye opener for me. The speed of light is not always c. That’s why refraction happens. Because light slows down in certain mediums below c. It’s kid of a coincidence that the speed of light happens to be c in a vacuum (actually I’m not sure about this…maybe there’s an organic reason why electromagnetic waves will be c in a vacuum that is fundamental). I do think it’s interesting that as humans our primary sense is to light which does happen to travel at c. I wonder how different our species would be if we couldn’t sense waves traveling at c, and for example, were only capable of detecting sound. Alternatively it may be that a species which could not sense waves traveling at c would not be capable of becoming as sophisticated as humans.
- Matumio 4y ago
  Dangerous speculation. One day, you will either step into a dark room and get eaten by a grue, or be killed by a gigantic bat who overheard your comment about her intellect. More seriously, I don't think speed-of-light has much biological relevance. It has consequences for microchips, though.
anonymouskimmer 4y ago
I kind of don't like this interpretation of events. The speed of causality varies depending on the speed of the causal particles and waves which propagate from an event. I was just reading an article on surviving nuclear detonations, and from those you have a few causal events propagating at different rates: the radiation, the shockwaves, the fallout. And if a tree falls in a forest with no one around, it does still make a sound.
- Swizec 4y ago
  The tree makes air move, but you need a subjective experience to turn that into sound.
  - Sebb767 4y ago
    That depends on whether you define sound as air waves/vibration or the sensation of hearing. Definitions vary [1,2,3], which is why this philosophical question manages to get people talking past each other. [1] https://www.merriam-webster.com/dictionary/sound https://www.merriam-webster.com/dictionary/sound [2] https://en.m.wikipedia.org/wiki/Sound https://en.m.wikipedia.org/wiki/Sound [3] https://dictionary.cambridge.org/dictionary/english/sound https://dictionary.cambridge.org/dictionary/english/sound (note that "can be heard" != "is heard")
    - sidlls 4y ago
      Then it's not a philosophical question so much as about the meaning of "sound". And "debates" about semantics are about as uninteresting as it gets.
      - Sebb767 4y ago
        A lot of "philosophical" questions boil down to semantic debates, see the sleeping beauty problem for another one [1]. So we can get into a philosophical (or semantic?) debate about that, for a funny instance of recursion :-) But I agree with that those debates are quite uninteresting, so let's not do that. [1] https://en.wikipedia.org/wiki/Sleeping_Beauty_problem https://en.wikipedia.org/wiki/Sleeping_Beauty_problem
      - mistermann 4y ago
        > And "debates" about semantics are about as uninteresting as it gets. A 'fact' that is relative to the frame of reference of the observer.
        sidlls 4y ago
NegativeK 4y ago
Causality is definitely not simultaneity. And yes, the speed of light is defined by the speed of causality, but c is still, among other things, the speed of light.
ethanbond 4y ago
IMO better description is “c is the maximum speed of information” Quantum entanglement can create causal effects much “faster” than c, but you cannot use such effects to transmit information still.
- jinwoo68 4y ago
  Measuring spin up of particle A is NOT a cause of measuring spin down of its entangled particle B.
  - ethanbond 4y ago
    Isn’t waveform collapse at Location B caused by waveform collapse at Location A? (Maybe a stupid question, I’ve only a passing interest in this stuff)
    - jinwoo68 4y ago
      My understanding is that when particles are entangled with each other, they must be described together with one wave function rather than one wave function for each of them. So once you measure particle A, the wave function collapses both for A and B.
      - ethanbond 4y ago
        Right. That… seems like causality to me.
    - Filligree 4y ago
      Location B will measure both up and down, but will only be able to communicate with the version of location A that measured the opposite value. There’s no need for FTL if you accept MWI.
    - codethief 4y ago
      No, if you change reference frames (in the special relativistic sense), the direction of causality might be opposite, i.e. collapse at B might suddenly cause the collapse at A.
Matumio 4y ago
> happening in real time Not sure about calling this "real time". If you actually wanted to do something about it (like saving the poor, mysterious object), then any help you send will face a completely different situation from what we see now.
- tshaddox 4y ago
  Okay, but that’s also true if I hear about a house fire 50 miles away. It’s way too late for me to do anything to save anyone there.
- tiagod 4y ago
  Imagine a world which is almost flat (but hilly), really big, and with a transparent atmosphere. We had extremely good telescopes, so from a big hill we could observe people a few thousands of km away, but we could only move very slowly. In the distance, there was another civilization that didn't have the technology to see us, or any other way to communicate with us. We also didn't have lasers or any other tech to send messages to them, other than travelling there (which would take some years), but we could see what was going there in almost real time. Wouldn't the same still apply, even without the limitations of the speed of light?
detrites 4y ago
So if sometime in the future, a pregnant human left Earth (say, through MuskTech's wormhole), and gave birth on a world orbiting Proxima Centauri, Earth's registrar shouldn't record it without adding an additional 4.3yrs? And when should the family back home celebrate? Defining the actual timing of events based on the presently available methods to perceive or communicate them seems odd if not also a bit impractical.
- delecti 4y ago
  Coordinating events as precise as births in a multiplanetary society is already going to be inherently impractical. The family back home should celebrate when it's relevant. If there's a wormhole, then the kid can probably make a call through it, so they can call on their (self-perceived) birthday. If the wormhole is a one-way trip, then the people back home should wait an additional 4.3 years to celebrate, because they won't have any idea until then.
codethief 4y ago
No, it's not. From our frame of reference (which, in General Relativistic terms, defines a coordinate system with a time coordinate) it still happened 26,000 years ago. If your friend tells you today about how they did X yesterday, would you also argue X happened today from your frame of reference?
- wolfendin 4y ago
  This confuses the ability to access information about events with the process of accessing information about events. Things happen at the earliest possible moment I could know about them. I was able to get that information about my friend yesterday, I just didn’t. I couldn’t have learned about this 26,000 years ago.
  - codethief 4y ago
    I'm not confusing anything. I was merely stating what General Relativity tells us in precise mathematical terms: Time passes between the event of something happening and the event when light/information from that first event first reaches us (or could theoretically reach us). This is reflected by a delta in the time coordinates of the involved events. > Things happen at the earliest possible moment I could know about them. You're of course free to define the word "happen" this way but among physicists you'd be the only one in doing so.
- anamexis 4y ago
  If you watch your friend do X right in front of you, would you argue it happened yesterday? They're both valid interpretations.
  - Supermancho 4y ago
    > If you watch your friend do X right in front of you, would you argue it happened yesterday? If that friend was 671 million miles away, I was say it happened yesterday. If it was a much smaller distance, I can intervene in the event because the relative effects do not prevent me from interacting. > They're both valid interpretations. That's true if you want to accept interpretation without restraint. I prefer consistent interpretations that are compatible with known physics. YMMV

rhaway84773 4y ago

Realizing that most often when we discuss the speed of light we’re not actually discussing the speed of light, but rather the speed of causality, was a huge eye opener for me. The speed of light is not always c. That’s why refraction happens. Because light slows down in certain mediums below c. It’s kid of a coincidence that the speed of light happens to be c in a vacuum (actually I’m not sure about this…maybe there’s an organic reason why electromagnetic waves will be c in a vacuum that is fundamental). I do think it’s interesting that as humans our primary sense is to light which does happen to travel at c. I wonder how different our species would be if we couldn’t sense waves traveling at c, and for example, were only capable of detecting sound. Alternatively it may be that a species which could not sense waves traveling at c would not be capable of becoming as sophisticated as humans.

Matumio 4y ago
Dangerous speculation. One day, you will either step into a dark room and get eaten by a grue, or be killed by a gigantic bat who overheard your comment about her intellect. More seriously, I don't think speed-of-light has much biological relevance. It has consequences for microchips, though.

anonymouskimmer 4y ago

I kind of don't like this interpretation of events. The speed of causality varies depending on the speed of the causal particles and waves which propagate from an event. I was just reading an article on surviving nuclear detonations, and from those you have a few causal events propagating at different rates: the radiation, the shockwaves, the fallout. And if a tree falls in a forest with no one around, it does still make a sound.

Swizec 4y ago
The tree makes air move, but you need a subjective experience to turn that into sound.
- Sebb767 4y ago
  That depends on whether you define sound as air waves/vibration or the sensation of hearing. Definitions vary [1,2,3], which is why this philosophical question manages to get people talking past each other. [1] https://www.merriam-webster.com/dictionary/sound https://www.merriam-webster.com/dictionary/sound [2] https://en.m.wikipedia.org/wiki/Sound https://en.m.wikipedia.org/wiki/Sound [3] https://dictionary.cambridge.org/dictionary/english/sound https://dictionary.cambridge.org/dictionary/english/sound (note that "can be heard" != "is heard")
  - sidlls 4y ago
    Then it's not a philosophical question so much as about the meaning of "sound". And "debates" about semantics are about as uninteresting as it gets.
    - Sebb767 4y ago
      A lot of "philosophical" questions boil down to semantic debates, see the sleeping beauty problem for another one [1]. So we can get into a philosophical (or semantic?) debate about that, for a funny instance of recursion :-) But I agree with that those debates are quite uninteresting, so let's not do that. [1] https://en.wikipedia.org/wiki/Sleeping_Beauty_problem https://en.wikipedia.org/wiki/Sleeping_Beauty_problem
    - mistermann 4y ago
      > And "debates" about semantics are about as uninteresting as it gets. A 'fact' that is relative to the frame of reference of the observer.
      - sidlls 4y ago

NegativeK 4y ago

Causality is definitely not simultaneity. And yes, the speed of light is defined by the speed of causality, but c is still, among other things, the speed of light.

ethanbond 4y ago

IMO better description is “c is the maximum speed of information” Quantum entanglement can create causal effects much “faster” than c, but you cannot use such effects to transmit information still.

jinwoo68 4y ago
Measuring spin up of particle A is NOT a cause of measuring spin down of its entangled particle B.
- ethanbond 4y ago
  Isn’t waveform collapse at Location B caused by waveform collapse at Location A? (Maybe a stupid question, I’ve only a passing interest in this stuff)
  - jinwoo68 4y ago
    My understanding is that when particles are entangled with each other, they must be described together with one wave function rather than one wave function for each of them. So once you measure particle A, the wave function collapses both for A and B.
    - ethanbond 4y ago
      Right. That… seems like causality to me.
  - Filligree 4y ago
    Location B will measure both up and down, but will only be able to communicate with the version of location A that measured the opposite value. There’s no need for FTL if you accept MWI.
  - codethief 4y ago
    No, if you change reference frames (in the special relativistic sense), the direction of causality might be opposite, i.e. collapse at B might suddenly cause the collapse at A.

Matumio 4y ago

> happening in real time Not sure about calling this "real time". If you actually wanted to do something about it (like saving the poor, mysterious object), then any help you send will face a completely different situation from what we see now.

tshaddox 4y ago
Okay, but that’s also true if I hear about a house fire 50 miles away. It’s way too late for me to do anything to save anyone there.
tiagod 4y ago
Imagine a world which is almost flat (but hilly), really big, and with a transparent atmosphere. We had extremely good telescopes, so from a big hill we could observe people a few thousands of km away, but we could only move very slowly. In the distance, there was another civilization that didn't have the technology to see us, or any other way to communicate with us. We also didn't have lasers or any other tech to send messages to them, other than travelling there (which would take some years), but we could see what was going there in almost real time. Wouldn't the same still apply, even without the limitations of the speed of light?

detrites 4y ago

So if sometime in the future, a pregnant human left Earth (say, through MuskTech's wormhole), and gave birth on a world orbiting Proxima Centauri, Earth's registrar shouldn't record it without adding an additional 4.3yrs? And when should the family back home celebrate? Defining the actual timing of events based on the presently available methods to perceive or communicate them seems odd if not also a bit impractical.

delecti 4y ago
Coordinating events as precise as births in a multiplanetary society is already going to be inherently impractical. The family back home should celebrate when it's relevant. If there's a wormhole, then the kid can probably make a call through it, so they can call on their (self-perceived) birthday. If the wormhole is a one-way trip, then the people back home should wait an additional 4.3 years to celebrate, because they won't have any idea until then.

codethief 4y ago

No, it's not. From our frame of reference (which, in General Relativistic terms, defines a coordinate system with a time coordinate) it still happened 26,000 years ago. If your friend tells you today about how they did X yesterday, would you also argue X happened today from your frame of reference?

wolfendin 4y ago
This confuses the ability to access information about events with the process of accessing information about events. Things happen at the earliest possible moment I could know about them. I was able to get that information about my friend yesterday, I just didn’t. I couldn’t have learned about this 26,000 years ago.
- codethief 4y ago
  I'm not confusing anything. I was merely stating what General Relativity tells us in precise mathematical terms: Time passes between the event of something happening and the event when light/information from that first event first reaches us (or could theoretically reach us). This is reflected by a delta in the time coordinates of the involved events. > Things happen at the earliest possible moment I could know about them. You're of course free to define the word "happen" this way but among physicists you'd be the only one in doing so.
anamexis 4y ago
If you watch your friend do X right in front of you, would you argue it happened yesterday? They're both valid interpretations.
- Supermancho 4y ago
  > If you watch your friend do X right in front of you, would you argue it happened yesterday? If that friend was 671 million miles away, I was say it happened yesterday. If it was a much smaller distance, I can intervene in the event because the relative effects do not prevent me from interacting. > They're both valid interpretations. That's true if you want to accept interpretation without restraint. I prefer consistent interpretations that are compatible with known physics. YMMV