Acceleration in Space

In free space, far away from any influential gravity, if I were to shoot a
gun (bullet starts at 1000 ft/sec., or hit a golf ball with my driver, or
even throw a baseball (you can plug in the arbitrary numbers for the initial
acceleration), how far will these aforementioned objects travel? Will their
speed EVER change? I know that this is probably a sophomoric question for
most of you, but please indulge me. Thank you.

Cordially,
west

Hi West,

Assume for a moment that you could be far enough away from the influence of
gravity - and remain so - then yes, it will continue to travel in a
straight-line (assuming flat space in the absence of gravity) for ever until
an external force it applied from something.

However, gravity knows no limit and thus there would be no place in the
known universe where the influence of gravity would be null. Maybe extremely
small - but then the concept of size (field strength) would be relative.
Thus the answer would be that gravitational forces would alter the motion -
though it might not be obvious to an observer for quite some time.

Then there's the concern of magnetic influences - but that's for later.

--
Thanks,
Jeffrey

Physics and Astronomy
Columbia, South Carolina
http://midlandstech.com/jlh



"west" wrote in message
news:Lkhmh.8441$tc5.6618@trnddc01...
In free space, far away from any influential gravity, if I were to shoot a
gun (bullet starts at 1000 ft/sec., or hit a golf ball with my driver, or
even throw a baseball (you can plug in the arbitrary numbers for the
initial
acceleration), how far will these aforementioned objects travel? Will
their
speed EVER change? I know that this is probably a sophomoric question for
most of you, but please indulge me. Thank you.

Cordially,
west

On or about 2007-01-02,
Jeff Hopkins atomic58 illuminated us with:
Hi West,

Assume for a moment that you could be far enough away from the influence of
gravity - and remain so - then yes, it will continue to travel in a
straight-line (assuming flat space in the absence of gravity) for ever until
an external force it applied from something.

However, gravity knows no limit and thus there would be no place in the
known universe where the influence of gravity would be null. Maybe extremely
small - but then the concept of size (field strength) would be relative.

OK, the pedant in me wonders whether there might indeed be null
gravity at a few points in the universe? Obviously mid-way between two
large identical masses, the gravity effect of each cancels the other
out. Might there not be to occasional spot in the real universe where
the net gravity is zero? Granted it doesn't actually affect your
answer to the original question as we have a moving object and it will
eventually encounter gravity as you say.

--
Mark
Real email address | Giraffiti:
is mark at | Concrete art, spray-painted very, very high.
ayliffe dot org |

Hi Mark,

Yes, you could be right - in all seriousness, such a possibility exists that
there might be a true null point somewhere at sometime. Perhaps even a null
region ... but based upon the assumption of a great deal of mass distributed
throughout the known universe in a somewhat random pattern coupled with the
fact that all of this mass is in motion would strongly hint against the
likelihood of a null point existing since the gravitational fields
themselves would be changing in strength nearly constantly. So a null region
would even be less likely.

I hope this example coming up it not too weak, but imagine a city pool with
20 to 30 children playing in it. The pool's surface would be in a state of
constant motion at all times - do some degree - and though the waves in some
location may momentarily cancel out leaving that region of the pool smooth -
it should not last long with the kids not only splashing (gravity) but
moving around at the same time (gravity waves).

--
Thanks,
Jeffrey

Physics and Astronomy
Columbia, South Carolina
http://midlandstech.com/jlh



"Mark Ayliffe" wrote in message
...
On or about 2007-01-02,
Jeff Hopkins atomic58 illuminated us with:
Hi West,

Assume for a moment that you could be far enough away from the influence
of
gravity - and remain so - then yes, it will continue to travel in a
straight-line (assuming flat space in the absence of gravity) for ever
until
an external force it applied from something.

However, gravity knows no limit and thus there would be no place in the
known universe where the influence of gravity would be null. Maybe
extremely
small - but then the concept of size (field strength) would be relative.

OK, the pedant in me wonders whether there might indeed be null
gravity at a few points in the universe? Obviously mid-way between two
large identical masses, the gravity effect of each cancels the other
out. Might there not be to occasional spot in the real universe where
the net gravity is zero? Granted it doesn't actually affect your
answer to the original question as we have a moving object and it will
eventually encounter gravity as you say.

--
Mark
Real email address | Giraffiti:
is mark at | Concrete art, spray-painted very, very
high.
ayliffe dot org |

Jeff Hopkins wrote:
Hi Mark,

Yes, you could be right - in all seriousness, such a possibility exists that
there might be a true null point somewhere at sometime. Perhaps even a null
region ... but based upon the assumption of a great deal of mass distributed
throughout the known universe in a somewhat random pattern coupled with the
fact that all of this mass is in motion would strongly hint against the
likelihood of a null point existing since the gravitational fields
themselves would be changing in strength nearly constantly. So a null region
would even be less likely.

I reckon there must be such a point, at the centre of mass of the universe.

Andy Guthrie wrote:
Jeff Hopkins wrote:

Hi Mark,

Yes, you could be right - in all seriousness, such a possibility
exists that there might be a true null point somewhere at sometime.
Perhaps even a null region ... but based upon the assumption of a
great deal of mass distributed throughout the known universe in a
somewhat random pattern coupled with the fact that all of this mass is
in motion would strongly hint against the likelihood of a null point
existing since the gravitational fields themselves would be changing
in strength nearly constantly. So a null region would even be less
likely.


I reckon there must be such a point, at the centre of mass of the universe.

As I understand such things, this above presumes, that the Universe is
finite (to be able to have a center of mass) - but to my knowledge it is
not known if it actually is finite or not ...

Claudio

Claudio Grondi wrote:
Andy Guthrie wrote:
Jeff Hopkins wrote:

Hi Mark,

Yes, you could be right - in all seriousness, such a possibility
exists that there might be a true null point somewhere at sometime.
Perhaps even a null region ... but based upon the assumption of a
great deal of mass distributed throughout the known universe in a
somewhat random pattern coupled with the fact that all of this mass
is in motion would strongly hint against the likelihood of a null
point existing since the gravitational fields themselves would be
changing in strength nearly constantly. So a null region would even
be less likely.


I reckon there must be such a point, at the centre of mass of the
universe.

As I understand such things, this above presumes, that the Universe is
finite (to be able to have a center of mass) - but to my knowledge it is
not known if it actually is finite or not ...

Finite but unbounded ?

I would still say there would have to be a point of gravitational
equilibrium, just as there is certainly a point somewhere on the Earth's
surface where the wind speed must be zero.

Claudio Grondi wrote:

As I understand such things, this above presumes, that the Universe is
finite (to be able to have a center of mass) - but to my knowledge it
is not known if it actually is finite or not ...

Claudio

Didn't Einstein say that no point of the universe can be considered special?
Surely the actual phyical centre of the universe, arrived at by pure
geometry, would look like, and have the properties of, any other point
chosen at random.

Gravity is an inverse square field but can never be said to be zero, however
far away from a given mass you are. Two objects orbiting each other can have
a point between them that is gravitationally null but this orbits with them
(lagrange 1 i think). Hardly "gravity free if your orbiting with a binary
system... any other nulls would be fleeting indeed as objects not orbiting
each other (if that can ever be said between any two objects in our
universe) follow their own paths in spacetime and move relative to each
other. If you watch a field drop to null then climb again you can slice the
time segments to ever finer degrees until the null happens as a point and
not an event making these nulls exeedingly, if not infinitly small.

Les




--
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"The God of the Old Testament is arguably the most unpleasant character
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control-freak ; a vindictive, bloodthirsty ethnic cleanser; a
misogynistic, homophobic, racist, infanticidal , genocidal , filicidal
, pestilential , megalomaniacal, sadomasochistic, capriciously
malevolent bully" (Richard Dawkins)

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Les Hemmings a.a #2251 SA