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Science Forum Index » Physics Forum » Does Newton's third law hold in Special Relativity?
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| PD |
 Posted: Thu Apr 10, 2008 6:06 am |
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On Apr 10, 10:52 am, Edward Green <spamspamsp...@netzero.com> wrote:
Quote: On Apr 9, 9:38 pm, "Robert J. Kolker" <bobkol...@comcast.net> wrote:
Edward Green wrote:
Not at a distance.
Relativistic momentum is conserved in all collisions.
Well, collisions imply contact, and that is not action at a distance.
No. Rutherford scattering does NOT imply contact, and it is a
collision. |
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| Jeffâ–˛Relf |
| Posted: Fri Apr 25, 2008 5:49 pm |
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If I understood you correctly..
Before Einstein “ discovered ” photons and atoms
he discovered “ e == m * c² ” via a thought experiment
involving radiation pressure and inertial objects.
Thanks.. that's Really good to know.
Shouldn't the kilogram be defined in terms of its field ?
Too bad we can't precisely measure its compton wavelength. |
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| Darwin123 |
| Posted: Sun Apr 27, 2008 4:42 pm |
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On Apr 9, 7:02 pm, Edward Green <spamspamsp...@netzero.com> wrote:
Quote: On Apr 7, 6:42 pm, Darwin123 <drosen0...@yahoo.com> wrote:
On Apr 7, 4:41 pm, "Timo A. Nieminen" <t...@physics.uq.edu.au> wrote:
On Mon, 7 Apr 2008, ram.rac...@gmail.com wrote:
The reason I was confused over this is because of the conservation of
momentum. Assume you're right, and the third law doesn't hold. Observe
this. Momentum is conserved in Special Relativity. Momentum remains a
constant. Force is the change of momentum over time. Therefore, the
total force must always be zero. But that would mean that for every 2-
body system, Newton's third law WILL hold. So how do you explain that?
Newton's 3 laws of motion can be summarised as "momentum is conserved",
with a definition of force thrown in for good measure. Sounds nicely
compatible with special relativity (given some care in what the derivative
in the rate of change of momentum in the definition of force is taken
w.r.t.).
What is incompatible between Newton and SR are: (a) Newton's definition of
mass, as the quantity of matter, vs SR magnitude of the energy-momentum
4-vector, (b) Newton's definition of momentum, and (c) if you include it
as part of Newtonian dynamics, Newton's law of universal gravitation.
In SR, there are no separated 2-body systems with forces. If the 2 bodies
are separated, and there is a force acting between them, it's mediated by
a field, and this field can transport energy and momentum. For 2-body
systems where the bodies only interact when in contact, Newton's 3rd will
be fine. For separated 2-body+field systems, it'll work too, if you assume
that you can exert a force on a field, defined by Newton's 2nd.
I don't think a field, or even a little piece of a field, can be
thought of as a body in the Principia sense.
Pedants seldom prosper.
Oh, I don't. I know people don't like it. I have been punished.
However, I think I am correct in this case.
What seems like pedantry to you right now may be a good model
for part of the creative process. The use and meaning of words is an
important part of mathematics. Advanced mathematics is more about
grammar than numerical calculations. Sometimes, an ambiguity in
language hides a deeper ambiguity.
Einstein and Lorentz were really bothered by something. They
both talked about the conflict between mechanics and electrodynamics.
Einstein said that he wasn't thinking about the Michelson-Morley
experiment when he wrote his papers. Yes, he had read the paper before
SR but it didn't figure prominently in his papers. His "thought
experiments" were designed to point out inconsistencies in the
physical theory. I am just pointing out that the physical theory is
actually built by words as well as equations. What do you think was
bothering Einstein and Lorentz? |
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| Jeffâ–˛Relf |
| Posted: Sun Apr 27, 2008 5:01 pm |
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We can't imagine nature as she truly is.
We can't imagine ( nor measure precisely )
the tiny 4-D gravitational field of, say, a billiard ball.
Worse.. the field is invisible, infinite in extent, and unblockable.
For example, we could toss the IPK ( International Prototype Kilogram )
into the trash if we could measure its gravitational field
precisely ( and consistently ).
The NIST in Colorado is hoping to do just that by
using a high-precision absolute gravimeter ( accelerometer )
and an ultra-precise weighing ( a Watt balance, in a vacuum ).
Einstein said:
“ I see a pattern,
but my imagination cannot picture the maker of that pattern.
I see a clock, but I cannot envision the clockmaker.
The human mind is unable to conceive of the four dimensions,
so how can it conceive of a God,
before whom a thousand years and a thousand dimensions are as one ? ”.
-- “ The Expanded Quotable Einstein ”,
Princeton University Press, 2000 Page 208
From Einstein's, " Ether and the Theory of Relativity " ( 1920 )
quoted at " http://TUHH.DE/rzt/rzt/it/Ether.html ":
" But this ether may not be thought of as
endowed with the quality characteristic of ponderable media,
as consisting of parts which may be tracked through time.
The idea of motion may not be applied to it. ".
Petkov ( 2005 ) has this to say:
“ This paper pursues two aims.
First, to show that the block universe view, regarding the universe as
a timelessly existing four-dimensional world,
is the only one that is consistent with special relativity.
Second, to argue that special relativity alone can resolve
the debate on whether the world is
three-dimensional or four-dimensional.
The argument advanced in the paper is that
if the world were three-dimensional
the kinematic consequences of special relativity and more importantly
the experiments confirming them would be impossible. ”.
-- “ Is There an Alternative to the Block Universe View ? ”
http://Philsci-Archive.Pitt.EDU/archive/00002408/ |
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| Jeffâ–˛Relf |
| Posted: Mon Apr 28, 2008 10:26 am |
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Like you and me, “ Uncle Rect-Al ” is an idiot savant,
a queer by-product of our overly-wealthy / overly-idle society.
Queerly, Uncle Rect-Al was just killing time ( 'til time kills him ).
Seeing as Uncle Rect-Al replied to me 3 times in a row
saying exactly the same thing ( admitting that he's an idiot savant ),
and you replied to him with extactly the same thing, 3 times in a row,
and seeing as Tom Potter keeps repeating exactly the same thing,
the following is a repeat of my recent post to Mr. NoEinstein..
Birth is the leading cause of death.
Given enough time, any immune system will give out,
and cancer is the result.
Consuming more ( especially alcohol and legal / illegal drugs )
makes one's immune system prematurely decrepit... that's called AIDS.
We have but one “ choice ”:
“ Live faster ( consuming more ) or live longer. ”.
This is true on a global level too, not just personally.
As I've said before..
Just as over-eating and over-drinking ruins one's health,
nations birthing too many kids and consuming too much crude oil
have ruined the health of the global economy.
To improve our health, we need more taxes and regulations,
especially child support “ taxes ”.
While “ sperm donors ” get an automatic ( computerized )
life-long irrevocable lien ( no judge can touch it )
accruing at 12 percent A.P.R. ( in “ interest and penalties ” )..
The mothers with young kids that I know get:
1,200 apartments for 120 dollars per month, free medical, free food,
free cash, free day care, free schooling ( college ), etc., etc.
No wonder people will do anything to immigrate to the U.S. !
“ able-bodied males ” ( like me ) get the bill.. nothing more. |
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| Uncle Al |
| Posted: Mon Apr 28, 2008 10:52 am |
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| hanson |
| Posted: Mon Apr 28, 2008 2:02 pm |
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"Uncle rect-Al" Schwartz <UncleAl0@hate.spam.net> wrote in message
news:4815F2BE.BD141F0D@hate.spam.net... to
We can't imagine nature as she truly is.
Quote: [snip crap]
hanson worte:
What is this "we" shit?... uncle rect-Al shows you daily how
he, rect-Al, "imagines nature as she truly is" and demonstrates
so on his own website... the way only he does it rect-Al-ly:
<http://www.mazepath.com/uncleal/sunshine.jpg>
that (link above) shows a perfect characterization of rect-Al's
cyber existence... Good choice. You are an honest dude, Al.
1) Incompetent individuals tend to overestimate their own level of
skill.
so, rect-Al shows here how he does it competently and accurately:
<http://www.mazepath.com/uncleal/sunshine.jpg>
2) Incompetent individuals fail to recognize genuine skill in others.
rect-Al refers by "others" to himself & shows how to recognize him:
<http://www.mazepath.com/uncleal/sunshine.jpg>
3) Incompetent individuals fail to recognize the extremity of their
inadequacy.
and so, rect-Al shows here what he does in order not to fail:
<http://www.mazepath.com/uncleal/sunshine.jpg>
Idiot.
rect-Al discovered his "idiot mantra" about himself in here:
<http://www.mazepath.com/uncleal/sunshine.jpg>.
recty-Al constantly checks and repeats it to spread the good
news about himself:... he, rect-Al being the mother of all idiots.
Quote:
Thanks for the laughs, schmuck... ahahaha... ahahahanson |
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| Jeffâ–˛Relf |
| Posted: Mon Apr 28, 2008 6:22 pm |
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When did I ask for money ? T.J. wanted me to buy a ship;
it was his idea to make me “ fabulously rich ”, not mine.
Spending less interests me far more than earning more would.
I like T.J. a lot, and I wish we could find a project to work on,
but our interests simply don't overlap.
Besides.. he no longer posts here.
I take my life and my cigarettes ultra seriously,
and I no longer have the cash to buy tobacco,
so I'm looking for alternatives ( like sun-dried lawn clippings ).
The only gimme I get from the government ( for being low income )
is 12 dollars off my monthly phone bill and food stamps.
I'm not picky about what I eat ( bread is good enough ),
so I can get free food from 10 different sources.. it's no big deal.
I might be able to use the food stamps to buy bulk herbs
( perhaps dried mint leaves ) for 9 dollars a pound,
but I don't know yet if it'd make a good cigarette.
Also, I don't know if I could order the poundage I require.
If I had the spare cash, I'd buy 100 cartons of super-thin, 120 mm,
slow burning “ Opal 120s ” cigarettes;
other than that, money doesn't interest me much. |
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| hanson |
| Posted: Tue Apr 29, 2008 12:38 am |
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"Jeff?Relf" <Jeff_Relf@X.Invalid> wrote in message
news:Jeff_Relf_2008_Apr_28__9_22_PY@X.Invalid...
Quote: I take my life and my cigarettes ultra seriously,
and I no longer have the cash to buy tobacco,
so I'm looking for alternatives ( like sun-dried lawn clippings ).
hanson wrote:
.... keep on doing that for a while and you will "smoke" your
lungs until they look like two little bags of dark beef jerky.
Then one day you will get a flushed face, your throat and
neck will puff up, and get swollen and your breathing will
become laborious... and under unimaginable pain for you
now... 90 days later after you have succumb to lung cancer
they'll bury you in the lawn where you got your lawn clippings
from... Don't be such a dumb shit, Relf... --- Brew some
moonshine, from any type of fruit, even used coffee grounds,
and sugar that you can get for free, if you need a fix that bad.
--- hanson |
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| Jeffâ–˛Relf |
| Posted: Tue Apr 29, 2008 7:39 am |
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Drinking moonshine ( instead of smoking hay ) won't prevent my death.
Like it or not, death comes with birth. |
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| hanson |
| Posted: Tue Apr 29, 2008 3:49 pm |
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.... WOAAAHahahaha... ahahahahAHAHAHAHAHAHA...
with the brilliant mind in his Einstein-Dingleberry sized
brain Lodo-Jeff justifies his lawn clipping habit with:
Quote:
"Jeff?Relf" <Jeff_Relf@X.Invalid> wrote...
Drinking moonshine ( instead of smoking hay ) won't
prevent my death. Like it or not, death comes with birth.
Quote:
.... after Jeff assured everybody that....
"Jeff?Relf" <Jeff_Relf@X.Invalid> wrote in message
news:Jeff_Relf_2008_Apr_28__9_22_PY@X.Invalid...
I take my life and my cigarettes ultra seriously,
and I no longer have the cash to buy tobacco,
so I'm looking for alternatives ( like sun-dried lawn clippings ).
So, since everything is "Kismet" to you and you are bent
on self-destruction, then at least do that right, given
your circumstances. Tell you landlord that you will mow
his lawns for free if you can let the clippings dry for a
few days and you can keep the hay... Then start with
and amongst your other fallen angels a thriving barter
exchange with your hay for other goodies that you can't
afford now. Good luck to you, Dreidel-Jeff... ahahaha...
Quote:
hanson wrote earlier to Jeff:
... keep on doing that for a while and you will "smoke" your
lungs until they look like two little bags of dark beef jerky.
Then one day you will get a flushed face, your throat and
neck will puff up, and get swollen and your breathing will
become laborious... and under unimaginable pain for you
now... 90 days later after you have succumb to lung cancer
they'll bury you in the lawn where you got your lawn clippings
from... Don't be such a dumb shit, Relf... --- Brew some
moonshine, from any type of fruit, even used coffee grounds,
and sugar that you can get for free, if you need a fix that bad.
--- hanson |
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