# swansont

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1. ## michel123456's relativity thread (from Time dilation dependence on direction)

When he returns the relative speed is zero, so no. Their clock run at the same rate, too, at that point. Length contraction and time dilation require motion (for SR). But during trip, yes, he is, according to the twin on earth. As is his spaceship. Reality has nothing to do with it. A billion different answers from a billion observers, and none of them can do a physics experiment that shows that “this is the ‘real‘ frame” Each frame is as real as the next. But I can’t cause a force to be exerted somewhere simply by moving. There’s so force, and rigidity is not an issue. Nothing is being crushed. A meter stick, or a length of a meter, is not a meter long when measured from a moving frame. Energy isn’t invariant, either. If you’re on a train car moving 100 m/s and throw a 1 kg ball 10 m/s, you see the ball moving 10 m/s and have 50 joules of KE. That’s true for anyone on the train. But that ball hitting a wall affixed to the earth is moving 110 m/s and has 6050 joules. Which one is “real”? Values depending on which frame you’re in is nothing unusual in physics. No, it isn’t. “Reality” is not anything relativity distinguishes Younger than his twin, because time ran slower for them. Not younger than when they started. And yes, the effect is real, in that it is not an illusion. Clocks would read different times.
2. ## Allowing personal use of motor vehicles is immoral

Who is forcing grandma to get in the car, against her will, without her regard for risk? Aren’t they the immoral one? If she drives of her own volition and accepts the risk, where is the immorality? She made the choice.
3. ## michel123456's relativity thread (from Time dilation dependence on direction)

So look at a situation where you don’t have a round object. Do railroad tracks get closer together in the distance? No, it’s perspective. We don’t worry that the train will derail. Let’s say you have a siren, at some frequency. It’s moving. If it’s moving toward you, the frequency is higher. If it’s moving away, it’s lower. You can hear this. The frequency is actually higher or lower, depending on your situation. It’s not an illusion. So the concept of some measurement being relative is not new. In relativity, length contraction comes from the invariance of c. The invariance is the new part. The derivation is pretty straightforward. In most situations, a moving object that ejects/emits something, you expect the speeds to add linearly. If you can throw an object 20 m/s and are on a platform moving 10 m/s, and throw the object in the direction of travel, it will go 30 m/s Light doesn’t behave that way, though. One consequence of c being invariant is that time and distance are not. If we “throw” this light from a moving platform and we both agree it moves at c (as we must) the only way for us to agree on measurements is if time and distance depend on our frame of reference There is no force. The measurement depends on the frame of reference. In the object’s own frame, nothing is different. There is no physics one can point to that says one frame is correct and the other is wrong.
4. ## michel123456's relativity thread (from Time dilation dependence on direction)

The lack of understanding is perfectly acceptable; you are making an effort to learn. The problem is when you insist that other things are or must be true. Whether or not you understand, you must at least acknowledge what people tell you is mainstream physics. You have no basis to say that it's wrong and/or some other position is right. Again, what you see and what you measure are not the same thing. Perspective is something you would account for if you were measuring the size of an object. If you look through a telescope and measure the angular size, you would need to know how far away it is. Nobody looks at the moon and insists that it is, in actuality, a few cm in diameter, or that the moon and the sun are physically the same size.
5. ## michel123456's relativity thread (from Time dilation dependence on direction)

As I recall you brought this up elsewhere, earlier. Perhaps you could not act like this issue wasn’t addressed? “Reality“ is an issue for philosophy What physics tells you is that the measurement value depends on who is doing the measurement Yes, it is. The lack of actual paradox is because of this The broken symmetry tells you who actually ages less. Why would you accept an explanation that is contradicted by experiments? Again, a matter for philosophy So you don’t understand it, and therefore nobody can?
6. ## Steering to the stars

Up to ~0.1c, non-relativistic equations are reasonably accurate, so v = at (thus, t = v/a, where v= 0.1c) and the displacement is s = 1/2 at^2
7. ## michel123456's relativity thread (from Time dilation dependence on direction)

They are not in the same frame Because that’s how relativity works, and relativity is how nature behaves. We have lots of evidence that time and space (distance) are relative. It’s not an arbitrary choice.
8. ## michel123456's relativity thread (from Time dilation dependence on direction)

You can’t state these values without acknowledging the frame in which they are measured. You have to keep that straight. Mixing frames won’t give a correct or consistent answer. ”Clock 2 lies 1 LH away” is true in the rest frame, not the moving frame. IOW, the moving clock doesn’t see a trip of 1 LH, since there is length contraction.
9. ## Using pattern recognition to avoid bad people

Until something happens to change the actual cause, which renders the correlation moot. If we use the beard example, since beards don’t actually cause bad behavior (or have a common cause with it), when styles change and people shave (or more people grow facial hair) the correlation will evaporate. But you’ll still be avoiding bearded people. Science allows you to predict. Correlation requires you to collect statistics and is only apparent after-the-fact.
10. ## America's Divorce from Science

The last dinner part I went to was with a bunch of physicists, so YMMV OTOH, the knowledge deficit model is known to fail pretty spectacularly in many cases. Focusing on one issue is shortsighted. Complex problems rarely have simple solutions. If the objection is emotional or irrational, it’s not communication of facts that is the problem, or the solution. And presenting sound science just makes these people dig in and hold on to their beliefs. Having one’s world view be upset tends to be an uncomfortable experience. One may resort to grasping at straws, or conspiracy, or whatever, in order to prevent that.
11. ## Using pattern recognition to avoid bad people

That category will likely suffer from small-number statistics
12. ## Using pattern recognition to avoid bad people

Finding out if those correlations are causal would be science. A point you have stopped short of. Without the science you just have bias and prejudice.
13. ## Allowing personal use of motor vehicles is immoral

! Moderator Note Given the lack of foundation and omitting information, I have to agree. It violates our rule on arguing in bad faith
14. ## I think I finally figured out the theory of everything in it's general answer and how to get to it.

! Moderator Note We discuss science here, and this ain’t it. Don’t broach this topic again. edit: You could start a thread and learn what science is, and why this isn’t a theory.
15. ## Electric charge – a different approach

! Moderator Note Rules still require that you post the material here. Not just upload a file.

17. ## The Yamato's Last Mission

Wait, a youtube video was inaccurate? Noooooooo!
18. ## Hijack from Strange self-induced feeling

! Moderator Note This is all off-topic, so it's now in the trash ! Moderator Note No, you're insulting, and you have a choice: do better, or, if this is how you intend to post, perhaps you could save everyone a lot of time and effort by quitting now.
19. ## Dark matter does not exist ?! What do you think ?

100 million as compared to Avogadro's number could be considered rare. All we can currently discern, AFAIK, is the mass of dark matter in a region (lensing, effects on galactic rotation, etc). If we don't know the mass of an individual particle, we can't quantify how many particles there are. Dark matter could be exceedingly common if it ends up having a very small mass. Less common if it has a large mass. (e.g. 1 eV vs 1 GeV would make the numbers different by 10^9)
20. ## michel123456's relativity thread (from Time dilation dependence on direction)

It's one light-hour only in the rest frame.
21. ## Time dilation is propagation delay (split from What is time? (Again))

I think that A knows the speed if light us finite, yes. That seems like a reasonable assumption, since it can be tested independently of this scenario, and would have been noticed already. I’m going with what was known about light prior to Einstein postulating c being invariant could be applied to kinematics. People already knew about the effects of the finite time it takes for information to travel. If A is ignorant of the signal delay, and does not account for it. Yes it is. Janus has made dozens of post on the topic, explaining the difference between what an observer “sees“ and what they measure the clock doing such as “It is important here not to confuse what someone visually sees happening to a clock approaching or receding with how fast that clock is actually ticking according to that person” https://www.scienceforums.net/topic/105185-time-dilation-dependence-on-direction/?tab=comments#comment-986159 Put another way, it is taken into consideration because the people involved understand and account for propagation delay. It’s not explicitly pointed out because it’s assumed that the reader already knows about the phenomenon
22. ## Time dilation is propagation delay (split from What is time? (Again))

That’s what A observes, but if A understands the propagation delay, this is not correct. A does not observe the clock to be running slow, because the time is the combination of the reading and the delay. IOW, if A does the measurement properly, this us not true. However, if A does the measurement incorrectly, A will get the wrong answer. One possibility being they assume the clock ran slow. They might also conclude that a dragon ate an hour of time. There are a large number of wrong answers one could apply. What’s the point of asking the same question over and over again? Are you hoping someone will eventually give you a different answer?
23. ## Phosphine detected on Venus

You misspelled “It’s aliens”
24. ## Time Zone Change Syndrome

! Moderator Note From rule 2.7 (emphasis added) Links, pictures and videos in posts should be relevant to the discussion, and members should be able to participate in the discussion without clicking any links or watching any videos. Videos and pictures should be accompanied by enough text to set the tone for the discussion, and should not be posted alone. Users advertising commercial sites will be banned. Attached documents should also be accompanied by a summary, at minimum.
25. ## Phosphine detected on Venus

"Strange chemical in clouds of Venus defies explanation. Could it be a sign of life?" https://www.space.com/venus-clouds-possible-life-chemical-discovery.html
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