perpetual motion

I gather that some poor student, physics confusion, was left in the dust. They probably went to Wiki or elsewhere for help.

Perpetual motion would be a good sticky topic for non-science visitors to be able to peruse, since it is a recurring theme among shade tree physicists and engineers. A short tutorial maybe, something like that, would nip it in the bud.
 
Perpetual motion is trivial: spin an object in the dead of space. Over-unity is fundamentally problematic, however, and I write this for onemancannon's sake because I read his post before he erased it. There are deeper issues involved, such the Law of Conservation of Energy, which preclude "getting really clever" in a machine's design to overcome obstacles. There is a fundamental barrier which cannot be overcome in principle.

As an analogy, consider this: I took a course on data analysis and compression in college. Someone asked the professor why there hadn't been any significant progress on a particular type of compression algorithm for such a long time, after so many years of steady improvement. His response was that the current form could be proven to provide something very close to the theoretically best compression result possible, and before he allowed me to think in these terms I naively thought that just "a little more ingenuity" would always yield a slightly better compression result.

In the mechanical world this theoretical barrier IS the unity line, where energy out = energy in at best, and we can only hope to approach it without any chance of ever crossing it.
 
Aqueous Id said:
I gather that some poor student, physics confusion, was left in the dust. They probably went to Wiki or elsewhere for help.

Perpetual motion would be a good sticky topic for non-science visitors to be able to peruse, since it is a recurring theme among shade tree physicists and engineers. A short tutorial maybe, something like that, would nip it in the bud.
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Why 'nip it in the bud'? Why not let people come to their own conclusions? It is a good exercise in physics to try to design perpetual motion machines and then discuss why they wouldn't work, at the very least.

RJBeery said:
As an analogy, consider this: I took a course on data analysis and compression in college. Someone asked the professor why there hadn't been any significant progress on a particular type of compression algorithm for such a long time, after so many years of steady improvement. His response was that the current form could be proven to provide something very close to the theoretically best compression result possible, and before he allowed me to think in these terms I naively thought that just "a little more ingenuity" would always yield a slightly better compression result.
Click to expand...

Digital data compression? Interesting. I had a fairly stray flight of fancy the other day when I got my new MP3 player - why do these files take up so much space? I thought that if someone really flexed their brain muscle maybe we could get smaller music files of the same quality and length.

RJBeery said:
In the mechanical world this theoretical barrier IS the unity line, where energy out = energy in at best, and we can only hope to approach it without any chance of ever crossing it.
Click to expand...

Yes, in the mechanical world! But why stop at mechanical models? It would be even more educational to read over a broad range of physics and science, not just kinetics, with the purpose of finding over unity devices.
 
DRZion said:
Why 'nip it in the bud'? Why not let people come to their own conclusions? It is a good exercise in physics to try to design perpetual motion machines and then discuss why they wouldn't work, at the very least.
Click to expand...
When I was 13 I built my first Perpetual Motion Machine. My own design and when you looked at it you would wonder why it would not start spinning, producing power all on its own. It was such a work of genius.

But alas the Laws of Thermodynamics were not going to be fooled by my cunningness. 45 years later and my Dad (RIP) still remembered the contraption. I think it marvelled him as well.
Miss those days! :bawl:
 
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DRZion said:
Digital data compression? Interesting. I had a fairly stray flight of fancy the other day when I got my new MP3 player - why do these files take up so much space? I thought that if someone really flexed their brain muscle maybe we could get smaller music files of the same quality and length.
Click to expand...
Yeah the MP3 algorithm actually isn't very efficient for compression. AAC is much better, and likely to be bumping up against the best we can ask for (in terms of file size at a given bit-rate). The only real areas for improvement are in tricks such as harmonic filtering or variable-bit-rate encoding depending on the complexity of the signal...basically playing with the fact that we can almost get the same subjective experience by opting to drop redundant or extraneous data (these are all lossy, don't forget).
 
DRZion said:
Digital data compression? Interesting. I had a fairly stray flight of fancy the other day when I got my new MP3 player - why do these files take up so much space? I thought that if someone really flexed their brain muscle maybe we could get smaller music files of the same quality and length.
Click to expand...
So much space?

Back in the dark days before MP3, most audio files were WAV files, which took up maybe 30Mb for a CD quality 3 minute track.
Try downloading that on a 56kbpss modem!
The most common method of 'compression' was to lose a stereo channel, reduce the sampling rate down to maybe 16kHz, which resulted in really crappy radio music, but a file size of as little as 5Mb.

MP3s are amazing!
 
Yeah...damn kids these days...when I was younger I had a Samsung Uproar, which only held about 12 songs, and I was GRATEFUL!
 
:cheers:
Is that an 8-track in your pocket, or are you just happy to see me?
 
Robittybob1 said:
When I was 13 I built my first Perpetual Motion Machine. My own design and when you looked at it you would wonder why it would not start spinning, producing power all on its own. It was such a work of genius.
Click to expand...

I am now trying to figure out how to extract energy from a high pressure closed (encapsulated) container without removing material from the inside. I am not sure if it is possible, but there is a pressure difference to work with. So far it has been a very rewarding project! :)

RJBeery said:
Yeah the MP3 algorithm actually isn't very efficient for compression. AAC is much better, and likely to be bumping up against the best we can ask for (in terms of file size at a given bit-rate). The only real areas for improvement are in tricks such as harmonic filtering or variable-bit-rate encoding depending on the complexity of the signal...basically playing with the fact that we can almost get the same subjective experience by opting to drop redundant or extraneous data (these are all lossy, don't forget).
Click to expand...

variable-bit-rate seems like it would be a good idea. I really have no idea how it works though. If you have one note playing it seems that it shouldn't take much information to recreate that. But, this isn't how real music sounds. Even if you look at a sheet of music, it doesn't begin to tell you how the song will sound when played by a musician.

A friend once told me that MP3s divide a track into tiny little pieces and take all of the data from each, which are later played back in order. In contrast, cassettes record everything in a smooth continuum - he says it results in a richer quality.

Pete said:
So much space?

Back in the dark days before MP3, most audio files were WAV files, which took up maybe 30Mb for a CD quality 3 minute track.
Try downloading that on a 56kbpss modem!
The most common method of 'compression' was to lose a stereo channel, reduce the sampling rate down to maybe 16kHz, which resulted in really crappy radio music, but a file size of as little as 5Mb.

MP3s are amazing!
Click to expand...

Supposedly some computer engineers were able to make (3 years ago or so) a compressed computer game fit into 4 Mbytes. Once unpacked it was over a gigabyte of data, but I don't know if that included music. However, it would take many hours to decompress and an enormous amount of processing power. :shrug:
 
Relative motion makes it possible to create perpetual motion. Only an absolute reference system does not allow perpetual motion.

If we have two objects of different mass in motion, relative motion can assign velocity to either reference. But since mass is different, one option will contain more kinetic energy. The extra energy can be used to run perpetual motion.

The equations of special relativity originally had three equations, one for mass, distance and time. The mass equation was there for the energy balance to make sure you don't create perpetual motion. But physics decided to rationalized away the mass equation and just use space and time and relative reference so we could create perpetual motion.
 
I don't like the English language version, it turns science into mechanical machines, and science is nature. I call the Universe a perpetual motion machine. And it works very well. It is a good starting point to have an empty page in front of you, and get the universe moving from nothing (or something that you can define as nothing). Because this is such a useful exercise.. I think the English Wikipedia version should be changed.
 
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There is some interesting discussion on this thread, but IMO it's not relevant to physics and maths. Moved to pseudoscience.
 
wellwisher said:
Relative motion makes it possible to create perpetual motion. Only an absolute reference system does not allow perpetual motion.
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Pure nonsense.

If we have two objects of different mass in motion, relative motion can assign velocity to either reference. But since mass is different, one option will contain more kinetic energy. The extra energy can be used to run perpetual motion.
Click to expand...
There is no "extra energy".

The equations of special relativity originally had three equations, one for mass, distance and time. The mass equation was there for the energy balance to make sure you don't create perpetual motion. But physics decided to rationalized away the mass equation and just use space and time and relative reference so we could create perpetual motion.
Click to expand...
Have you ever bothered to get an education?
How did "physics rationalised away the mass equation"?
 
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