91

General Science / Re: How does ChatGPT work?

« Last post by evan_au on 26/05/2023 22:48:33 »

recycling other people's text

Most science is just recycling other people's words.

Perhaps it ChatGPT permutes those same words into a new (but not totally unlikely) sequence, it may, perchance, generate something useful.
- Separating the gold and gems from the stream of derivative drivel is left as an exercise for the reader...

92

General Science / Re: What is the smallest laser able to melt iron made by nanotechnology?

« Last post by evan_au on 26/05/2023 22:44:06 »

Provided you thermally isolate the iron particles in a vacuum, and surround it by mirrors to keep most of the radiated heat in, you shouldn't need a very big laser to melt it.

Particles of iron can also be very small. The iron particles which form "seeds" for carbon nanotubes are only nanometers across. The main challenge here is how to focus a significant amount of optical power on a target which is smaller than a wavelength.

93

New Theories / Re: A Quandary about Accelerated Motion in Special Relativity

« Last post by MikeFontenot on 26/05/2023 21:21:36 »

I'm just not able to follow you, Eternal.

Each rocket has an attached accelerometer, and those two accelerometers always show exactly the same acceleration. (That is part of the initial specification of the scenario).  The INITIAL diagram says that the inertial observers who are stationary wrt the rockets immediately before the rockets fire, say that the separation of the rockets doesn't vary.  But THAT violates special relativity:  special relativity says (via the length contraction equation) that an inertial observer MUST conclude that a yardstick moving away from himself (in the direction of its length) is shorter than his own yardsticks.  (And the faster the yardstick moves, the shorter it becomes, according to that inertial observer).  So those inertial observers must conclude that the separation of the rockets MUST decrease as the rockets accelerate away.  And the faster the rockets go, the more the separation decreases.  So that initial diagram is incorrect, because it violates special relativity.

94

General Science / Re: What causes people to distrust science?

« Last post by alancalverd on 26/05/2023 20:02:31 »

Half-truths, religion, politics, marketing, and bad science.

95

General Science / Re: What is the smallest laser able to melt iron made by nanotechnology?

« Last post by Petrochemicals on 26/05/2023 19:48:39 »

lazers can be very very small, perhaps one photons width.

https://cutlasercut.com/drawing-resources/expert-tips/laser-kerf/#:~:text=The%20laser%20burns%20away%20a,experienced%20when%20cutting%20thicker%20foams.

96

New Theories / Re: A Quandary about Accelerated Motion in Special Relativity

« Last post by Eternal Student on 26/05/2023 19:31:55 »

Hi.

WHEN you do that, then the original diagram (that hung over my desk for 20 to 30 years) violates special relativity ... because the inertial observers who are stationary with the rockets immediately before the rockets are fired, claim that the separation between rockets is constant.

     It doesn't violate special relativity and it's not impossible for that to be the motion and corresponding worldlines of the rockets.    Are the observers who were "stationary with the rockets immediately before the rockets were fired" going to observe those worldlines for the rockets or not?   That is a choice you have.    Decide how the rockets will move in this frame (which I'll call the lab frame).   You can make this choice - but then it will determine what happens to a piece of string that connected the two rockets.

Special relativity (via the length contraction equation) says that any inertial observer will conclude that yardsticks that are moving (in the direction of their length) wrt himself are shorter than his own yardsticks (by the gamma factor).  I.e., if gamma = 2.0, the yardsticks are only half as long as they would be if they weren't moving relative to the inertial observer.  So the inertial observers who are stationary with the rockets immediately before the rockets are fired MUST (according to special relativity) say that the two rockets get closer together as their speed increases.

   There weren't any rigid connections like yard sticks between the rockets.  If you do put a rigid connection rod between them (e.g. the rope or piece of string in Bell's spaceship paradox) then you do find there is a problem, exactly as you have outlined.
      If the motion of the rockets was as originally described (constant separation in the lab frame), then the string must break.

      Alternatively you can start the problem the other way round.  Stipulate that a string of fixed length was attached between the two rockets and it did not break as the rockets accelerated.   Then the motion of the rockets (in the lab frame) could not have been as previously described,  it would have been different.  The motion of the rockets in the lab frame would be exactly as you have described later in the post - the observers who stay in the lab frame would see the rockets getting closer together as time progresses.   One consequence of this is that, in the lab frame, the rockets did not have the same acceleration at every moment of time.

I hope that makes some sense.   You can choose how the rockets move in the lab frame   OR   if the string will break.   However, you can't choose to have the rockets accelerate equally at every moment of time in the lab frame AND ALSO avoid the string breaking  --->   That's a combination that is not possible.

Best Wishes.

97

Just Chat! / Re: Why is it so easy to fool wine experts?

« Last post by Bored chemist on 26/05/2023 17:50:31 »

if anyone out there knows what I'm talking about....

Watch this space...

98

Just Chat! / Re: The Linguistic Status Of 'Thrice'?

« Last post by Bored chemist on 26/05/2023 17:45:03 »

and the rich magical thunder of the King James Bible

... castrated when people realised that magic doesn't work.
I still use thrice. It's a perfectly cromulent word.

99

New Theories / Re: An essay in futility, too long to read :)

« Last post by yor_on on 26/05/2023 17:44:47 »

Then again, I doubt all of it, looking at our path, and behaviors. Wars have a way with people.

100

General Science / Re: What causes people to distrust science?

« Last post by Bored chemist on 26/05/2023 17:43:15 »

Mainly, liars.