Vinicio Coletti's proposal about gravity
Does it depends on speed?
Missing matter is really missing?
First published on December 12, 1999
following a newsgroup discussion on July, 1998
Updated on October 30, 2002
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According to
Newton, the gravitational force depends on the mass of the two bodies we are
considering and on their distance:
The G in the
formula is the gravitational constant, expressing a scale factor, that depends
also on the units you use. Standard units are the meter and the kilogram,
thus
This mean that
between two bodies of 1 kg each at a distance of 1 meter there will be a
gravitational force of about 66.7 pN (pico-Newton).
According to Einstein, gravity is not a force at all. Bodies
curve space-time and they move along this deformed continuum. Also, the way we
perceive phenomena depends on the relative motion of the bodies, if they are
accelerated or not and so on.
If a body is going away from an observer at
rest, at a very high speed (a not minimal fraction of the speed of light),
signals from it will still come at the speed of light, but shifted to lower
frequencies.
All phisical phenomena we observe on the fast body will look
slower than normal (and for us they will be actually slower).
The
dimensions of the body will also look shorter from the farest to the nearest
side and, most importantly, the mass will look greater.
My proposal
During July 1998 I discussed these topics on an Italian
newsgroup, namely it.scienza, asking questions to some scientists and
other people discussing there.
In one of these messages I asked this
question:
if we perceive red-shifted radiation from a body going away very
quickly, and this is a quite real effect (we see it!), why we should not
perceive the effects of its greater mass, which is also a relativistic
effect?
Well, the question was indeed asked a bit more naively, as you
can read in one of the original messages posted by me on the newsgroup
it.scienza on July 2, 1998 (other messages are lost).
However, this
time I had no answers...
The message is in its original form, in Italian, but
I have outlined in bold the most important sentence.
Path: news.mclink.it!usenet
From: vcoletti@webcom.com (Vinicio
Coletti)
Newsgroups: it.scienza
Subject: Massa
Date: Thu, 02 Jul
1998 05:45:44 GMT
Organization: MC-link The World On Line
Lines:
22
Message-ID: <359b1d5e.28599899@news.mclink.it>
Reply-To:
vcoletti@webcom.com
NNTP-Posting-Host:
net144-105.mclink.it
X-Newsreader: Forte Free Agent
1.1/32.230
Uhm... torno sul problema della massa
relativistica.
Sto leggendo "Dal Big Bang ai buchi neri" di
Hawking e in uno dei
capitoli iniziali si dice che, siccome l'energia
e' equivalente
alla massa secondo la nota equazione, man mano che un
corpo
accelera la sua massa complessiva aumenta e quindi diventa
sempre
piu' difficile accelerarlo, per cui la velocita' della luce
non
si puo' superare ed un corpo con massa a riposo avrebbe
bisogno
di energia infinita per raggiungere c.
E' corretta
questa impostazione ?
Inoltre, se la massa aumenta effettivamente,
il resto
dell'universo ne risente ? Cioe': se un corpo si allontana da
me
a velocita' relativistiche, l'attrazione gravitazionale di
quel
corpo verso di me AUMENTA ?
(naturalmente, tenendo conto
della distanza che aumenta,
l'attrazione complessiva puo' anche
ridursi, ma volevo sapere se
la massa del corpo in allontanamento
bisogna scriverla
effettivamente aumentata nella formula F=k*m1*m2/d^2)
Vinicio Coletti - http://www.webcom.com/vcoletti
vcoletti@webcom.com |
This mean that we should compute the gravitational attraction
taking into account also the relative speed of the bodies, and the Newton
formula should become:
| F = G |
q2 m1 m2 |
| ------------- |
| d2 |
where each
body mass is considered increased by the speed (q is the increase factor that
depends on the speed).
Cosmological effects
Since our universe is expanding, the speed at which
two galaxies go away each from the other usually increases with the
distance.
The universe is very large, so most galaxies are very far and going
away very quickly from us (and from whatever site).
This mean that at the
cosmological level the effects of relativistic mass are very important
because gravity is stronger at so high recession speeds.
In my
opinion, this could also mean that there is not missing mass in the
universe.
Perhaps, using the q factor and computing this way the gravity,
we could discover that the observed expantion rate of the universe is totally
coherent with the observed matter density (or at least much less incoherent than
today).
Send your feedback
Addition of October 30, 2002
If you tought it was too strange to propose a modification of the Newton laws about
gravity, well, I have recently discovered that I am not alone.
When I bought the October 2002 issue of the Italian magazine "Le Scienze"
(which publishes many of the articles of "Scientific American") I kept
staring at pages 42-50, the mouth open...
What Le Scienze publishes is an article by Mordechai Milgrom, professor of physics
in a Middle East research institute.
Prof. Milgrom proposes
a theory named MOND (MOdified Newton Dynamics) stating that at very low values of
the acceleration constant, you need less force, compared to plain Newton laws, to
induce acceleration to a certain mass. This explains fairly well how matter behaves in
large galaxies, without any needs of dark matter.
Milgrom introduced this idea with the article "A Modification of the
Newton Dynamics as a Possible Alternative to the Hidden Mass Hypothesis" in the
Astrophysical Journal 270, pp. 365-370 of July 15, 1983.
There are several things to say about these two ideas:
- First of all, while Mordechai Milgrom is a real scientist, a professor of
physics, I am simply a curious naively observing things
- and this means that, while Milgrom's idea is a real theory, mine can be considered
only a hint.
- According to Milgrom, the modifying factor is the gravitational acceleration itself.
When this is high, the Milgrom's Law yields results very close to plain Newton Laws and
is thus undetectable in the everyday life in the solar system. But when the acceleration
is very low, as in the external part of large galaxies, computations diverge and Milgrom's
Law describes facts much better than Newton's one. You don't need dark matter at all.
- My hint is a bit different, because I imagine it is the relative speed of bodies
that causes an increase of the force, as if each body observed the other having a greater mass.
And linking this effect to the relativity, at least conceptually (because real computations of
this kind are out of my nowadays skills).
However, I don't know (that is I have not computed) how this could actually modify the behavior of
matter in galaxies, galaxy groups and so on. Ideally, one should simulate the distribution of
mass in a galaxy and compute all relative speeds and gravitational forces acting on each
simulated body.
If you want to know more on MOND theory and Mordechai Milgrom, here are a few links.
Ideas
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