Re: Page 137: Adieu SG-51
Posted: Sun Jul 22, 2018 8:19 pm
And FTL through shortcuts is directly equivalent to FTL through inflation, by which I mean that it isn't FTL at all.
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What do you mean by FTL through inflation?Absalom wrote:And FTL through shortcuts is directly equivalent to FTL through inflation, by which I mean that it isn't FTL at all.
It occurs to me that this is not an argument for why causality must exist. It is an argument for keeping physicists in a job.Your average physicist holds Relativity quite strongly. It has been tested again and again with an accuracy of many decimal places. They hold onto Causality even tighter. Without Causality the entire structure of physics crumbles. Causes must preceed effects, or it becomes impossible to make predictions. If it is impossible to make predictions, it would be best to give up physics for a more profitable line of work.
Actually, it does.RedDwarfIV wrote:It states that relativity has been tested again and again, accurately. But it does not say the same about causality.
Emphasis mine. Scientists really have put a significant amount of effort into looking for ways to break causality, especially with quantum mechanics. But even proponents of retrocausal quantum theory recognize that information cannot be sent back in time, even if a future event changes the random quantum state of entangled pairs. (See Bell's Theorem)Your average physicist holds Relativity quite strongly. It has been tested again and again with an accuracy of many decimal places. They hold onto Causality even tighter.
It is not an argument for why causality must exist, but it isn't an argument for keeping physicists in a job either. It is an argument for why you can't have Causality, Relativity, and FTL travel at the same time, and an argument for why scientific method breaks down without cause and effect.RedDwarfIV wrote:Therefore, if we can build FTL drives... then all we have done is put the physicists out of work. So long as effect before cause is limited to people who can't actually do anything with the information, no paradoxes will occur, and the universe carries on as normal.
No.boldilocks wrote:Does that mean watching a movie played in reverse violates causality?
I guess I'm having problems understanding how you can observe something before it happened.icekatze wrote:hi hi
No.boldilocks wrote:Does that mean watching a movie played in reverse violates causality?
If you played a movie before it was filmed, then you'd be in a violation of causality, but the universe doesn't care what time stamp we put on our recordings of events.
You can set your computer's calendar to 1990, but that's not violating causality. And the light from a series of p-n junction diodes attempting to imitate the light from an earlier event, is not the same thing as the light from that event. It is its own event.
The digitally encoded data at the beginning of a movie does not cause the digitally encoded data at the end of the movie to exist.
You can't. That's kind of the point.boldilocks wrote:I guess I'm having problems understanding how you can observe something before it happened.
But for FTL to be impossible you'd have to be able to. So it ends up as "FTL is impossible because if not you'd be able to do this other thing which is impossible."Arioch wrote:You can't. That's kind of the point.boldilocks wrote:I guess I'm having problems understanding how you can observe something before it happened.
The point is, as I tried to show in my pictures on the preceding page, that there is no such thing as a universal "now" time. It's relative for each observer. That's all fine if you're not allowed to travel or communicate information faster than light. But once you introduce ftl, you can create arrangements where some observers will perceive that effect precedes cause. And that cannot be because no point of view is more valid than any other. The speed of light limit ensures that for all observers in any frame of reference, effect will never precede cause.boldilocks wrote:
I guess I'm having problems understanding how you can observe something before it happened.
Which time is it going backwards in, if time is relative for each observer? The time they observe or the time of the people "transmitting"? At the end of the day, the photons it picked up in order to "observe" something would have to have been set in motion for them to be received, right?Victor_D wrote:The point is, as I tried to show in my pictures on the preceding page, that there is no such thing as a universal "now" time. It's relative for each observer. That's all fine if you're not allowed to travel or communicate information faster than light. But once you introduce ftl, you can create arrangements where some observers will perceive that effect precedes cause. And that cannot be because no point of view is more valid than any other. The speed of light limit ensures that for all observers in any frame of reference, effect will never precede cause.boldilocks wrote:I guess I'm having problems understanding how you can observe something before it happened.
If this were not true, then you'd be able to produce the paradox I described in the pictures. It arises because for both observers in that scenario, an FTL ship coming from the other location is going backwards in time.
Instant Cassettes, anyone?icekatze wrote:No.boldilocks wrote:Does that mean watching a movie played in reverse violates causality?
If you played a movie before it was filmed, then you'd be in a violation of causality, but the universe doesn't care what time stamp we put on our recordings of events.
Well, what this implies for the real universe is that FTL drive is impossible, which is perhaps a good explanation of why we don't see starships zipping by every day. However, To say "any FTL travel breaks causality" is not really a true statement, because there are instances in the real universe in which phenomena happen faster than light, but the universe is structured so that such phenomena can never transmit meaningful information in violation of causation.boldilocks wrote:But for FTL to be impossible you'd have to be able to. So it ends up as "FTL is impossible because if not you'd be able to do this other thing which is impossible."Arioch wrote:You can't. That's kind of the point.boldilocks wrote:I guess I'm having problems understanding how you can observe something before it happened.