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Jim Jones
July 29th 03, 02:38 AM
Hi.

If it where possible to create or to send 2 incredibly huge boulders
into outer space from Earth and just let them float out there , would
they eventually revolve around each other ? Is that how masses in
outer space work? They just find their gravitation point, and start to
"do si do" ?

What if launched from the moon ?

Or, would our solar system reject them? If so, what would it do with
these 2 new intruders, which did not come from way out there, but from
our modest little planet ?
Would they hook up with the asteroid belt outside of mars ?

Would they stay together at all, if when on earth they had absolutely
no magnetic properties ?

Does the pull of gravity get stronger on larger planets and weaker on
smaller planets ?

Why do the planets and moons pull (gravity) anyway? Is it because
they're so large? Is it the activity at the core?

Thanks in advance,

Jim

Ron Miller
July 29th 03, 11:01 AM
"Jim Jones" > wrote in message
...
> Hi.
>
> If it where possible to create or to send 2 incredibly huge boulders
> into outer space from Earth and just let them float out there , would
> they eventually revolve around each other ? Is that how masses in
> outer space work? They just find their gravitation point, and start to
> "do si do" ?

More or less, yes.

> What if launched from the moon ?

Would make no difference.

> Or, would our solar system reject them? If so, what would it do with
> these 2 new intruders, which did not come from way out there, but from
> our modest little planet ?

The solar system could care less.

> Would they hook up with the asteroid belt outside of mars ?

Not necessarily. They would orbit wherever you launched them to.

> Would they stay together at all, if when on earth they had absolutely
> no magnetic properties ?

Gravity is the operator here, not magnetism.

> Does the pull of gravity get stronger on larger planets and weaker on
> smaller planets ?

Yes.

> Why do the planets and moons pull (gravity) anyway? Is it because
> they're so large? Is it the activity at the core?

It is because of their mass.

RM

Jim
July 30th 03, 01:27 AM
On Tue, 29 Jul 2003 06:01:14 -0400, "Ron Miller"
> wrote:

>
>"Jim Jones" > wrote in message
...
>> Hi.
>>
>> If it where possible to create or to send 2 incredibly huge boulders
>> into outer space from Earth and just let them float out there , would
>> they eventually revolve around each other ? Is that how masses in
>> outer space work? They just find their gravitation point, and start to
>> "do si do" ?
>
>More or less, yes.
>
>> What if launched from the moon ?
>
>Would make no difference.
>
>> Or, would our solar system reject them? If so, what would it do with
>> these 2 new intruders, which did not come from way out there, but from
>> our modest little planet ?
>
>The solar system could care less.
>
>> Would they hook up with the asteroid belt outside of mars ?
>
>Not necessarily. They would orbit wherever you launched them to.
>
>> Would they stay together at all, if when on earth they had absolutely
>> no magnetic properties ?
>
>Gravity is the operator here, not magnetism.
>
>> Does the pull of gravity get stronger on larger planets and weaker on
>> smaller planets ?
>
>Yes.
>
>> Why do the planets and moons pull (gravity) anyway? Is it because
>> they're so large? Is it the activity at the core?
>
>It is because of their mass.
>
>RM

Ron,

Thanks for your prompt response and your help in clearing up those
things, but I may be unclear on what you mean, in the last statement,
about "It's their mass".

Let me rephrase my question. And please don't think you're being too
simple in answering:
Q. Why does earth hang onto it's loose objects ? What about "mass"
might I not be understanding.

ALSO: Does gravity gradually drop off, as we get higher and higher
into the atmosphere, OR, is there a fine line where gravity goes from
gravity to no gravity?

Thanks again,
Jim

Bill Nunnelee
July 30th 03, 02:28 AM
Let me correct the equation before somebody else does. :-)

F = (G * m1 * m2) / r^2

Where G is the gravitational constant.


"Bill Nunnelee" > wrote in message
thlink.net...
> The outcome of the boulders would depend on their velocities relative to
> each other. If zero (and they were sufficiently close to each other),
their
> mutual gravitational attraction would pull them together---instead of
> orbiting, they would collide. (Gravity works over any distance, but if
they
> were too far apart, the influence of other solar system bodies would
> probably overwhelm any mutual attraction.) It wouldn't matter if they
were
> launched from the earth or the moon.
>
> Whether they would stay or go depends on whether they were given enough of
> an initial push to reach escape velocity or not. The initial speed and
> direction would also determine their orbit around the sun if they stayed.
> They could also be ejected by passing close to another body and picking up
> some of the body's energy. Gravitational assists were used with many
space
> probes, and close passages of Jupiter have been responsible for ejecting
> many comets over time.
>
> Magnetism is an entirely different force. The strength of gravity depends
> on the mass of the two objects involved and the distance between them.
> Newton expressed it as F = m1*m2 / r^2, where m1 and m2 are the two masses
> and r is the distance between them.
>
>
>
>
> "Jim Jones" > wrote in message
> ...
> > Hi.
> >
> > If it where possible to create or to send 2 incredibly huge boulders
> > into outer space from Earth and just let them float out there , would
> > they eventually revolve around each other ? Is that how masses in
> > outer space work? They just find their gravitation point, and start to
> > "do si do" ?
> >
> > What if launched from the moon ?
> >
> > Or, would our solar system reject them? If so, what would it do with
> > these 2 new intruders, which did not come from way out there, but from
> > our modest little planet ?
> > Would they hook up with the asteroid belt outside of mars ?
> >
> > Would they stay together at all, if when on earth they had absolutely
> > no magnetic properties ?
> >
> > Does the pull of gravity get stronger on larger planets and weaker on
> > smaller planets ?
> >
> > Why do the planets and moons pull (gravity) anyway? Is it because
> > they're so large? Is it the activity at the core?
> >
> > Thanks in advance,
> >
> > Jim
> >
> >
> >
> >
> >
>
>
>

Kent
July 30th 03, 04:43 AM
Jim wrote:
>
> Thanks for your prompt response and your help in clearing up those
> things, but I may be unclear on what you mean, in the last statement,
> about "It's their mass".

As an amateur myself I can put it the layman's terms I learned for you.
I hope you and Ron don't mind my jumping in. Mass is what determines an
object's gravity, not its size. Mass is simply the amount of "stuff" in
something. For example: a tennis ball and a tennis ball-sized rock.
The rock has more mass (stuff in it) than the tennis ball. In your hands
the rock weighs more than the ball, since there is more stuff in it for
gravity to draw upon (i.e. it weighs more).

Naturally, on the moon the rock would weigh less than it does on Earth,
and on Jupiter it would weigh more. So mass is the term used to describe
"stuff" astronomically, rather than size or weight, in regards to
gravity. Size only comes into it because there's so much more room for
"stuff" to be in. But that doesn't necessarily mean there *will* be
more "stuff" in the bigger object. So you can see that if Jupiter
(mostly gassy) were the same size as Earth (mostly rock), Earth would
have more mass and therefore more gravity. Same goes for if Earth were
the same size as Jupiter.

> Let me rephrase my question. And please don't think you're being too
> simple in answering:
> Q. Why does earth hang onto it's loose objects ?

Gravity, coupled with the fact the loose objects aren't going fast
enough to break away, nor slow enough to plummet to the ground.

> ALSO: Does gravity gradually drop off, as we get higher and higher
> into the atmosphere, OR, is there a fine line where gravity goes from
> gravity to no gravity?

The first. The "Dropping Off Equation", IIRC, is 1/R(squared). Where R
= radius of the Earth = 4000 miles = surface Gravity, or 1 G.

So if you fly out to 4000 miles *above* the surface = 1/2(squared) =
1/4th the strength of surface Gravity = .25 G's.

At the moon (ignoring its own gravity) = .00028 G's.

At Jupiter (ignoring its own gravity) = .000000000000000002 G's

As you can see, we'll never reach 0. Gravity will just drop off into
really, REALLY small numbers the farther out we go. Hope this helps a
bit.

Cheers,
Kent

Odysseus
July 30th 03, 05:27 AM
Jim wrote:
>
> Let me rephrase my question. And please don't think you're being too
> simple in answering:
> Q. Why does earth hang onto it's loose objects ? What about "mass"
> might I not be understanding.
>
Every body with mass attracts every other, in proportion to the
masses of both and in inverse proportion to the square of the
distance between their centres. Bill posted this same statement in
the form of an equation. On earth our principal experience of mass is
in the form of weight; a "heavy" object has a large mass, while the
mass of a "light" object is small. The weight of an object measures
the strength of its attraction to the earth, whose mass is so
enormous that it dominates everything near it. We don't notice the
attraction of one 'ordinary-sized' object for another because gravity
is very weak -- except when things as big as planets and moons are
involved. But using extremely sensitive torsion balances, the
gravitational attraction between very large weights suspended very
close to each other can actually be measured in a laboratory.

An object resting on the earth's surface stays where it is because
the ground 'pushes back' with an equal force; if unsupported it will
fall with an acceleration called "g", making its speed constantly
increase by a little under ten metres (about 32 feet) per second
every second. In order to raise an object off the surface one has to
supply a lifting force *greater* than the pull of gravity, i.e. the
object's weight.

> ALSO: Does gravity gradually drop off, as we get higher and higher
> into the atmosphere, OR, is there a fine line where gravity goes from
> gravity to no gravity?
>
It drops off gradually at first, then faster and faster, but never
disappears altogether. In principle the earth's gravity field goes
out to infinity, and in turn we experience gravitational attraction
from every star in our galaxy and beyond -- but at great distances
the forces become too small to have any noticeable effect. The key
here is the "square" part of the inverse square ratio I mentioned
above: the 'weakening' effect of great distance overcomes the
'strengthening' effect of great mass.

--
Odysseus

BenignVanilla
July 30th 03, 02:04 PM
"Kent" > wrote in message
...
<snip>
> At Jupiter (ignoring its own gravity) = .000000000000000002 G's
>
> As you can see, we'll never reach 0. Gravity will just drop off into
> really, REALLY small numbers the farther out we go. Hope this helps a
> bit.
<snip>

Is this true? Gravity never quites get to 0? I am having one of those
moments. This is shocking. Can someone expound on this? The concept sounds
very important. How far can we actually measure before we can't "sense" the
field anymore?

BV.

Bill Sheppard
July 30th 03, 07:36 PM
>Surely gravity is nullified when an object
>equi-distant from two bodies having
>equal gravitational pull?

It's called the barycenter (or barycentre to the Brits), the
gravitational null point, or effective center of mass, between two
co-orbiting bodies. In some situations, the barycenter can actually be
below the surface of the larger body.

oc

Odysseus
July 31st 03, 07:44 AM
Jonathan Silverlight wrote:
>
> The forces are still at work. It's like a tug of war, equally balanced
> and just as unstable. After all, the moon pulls on the Earth even though
> it's well outside the sphere where the Earth dominates (and vice versa).
> Of course for other planets the force becomes so small it's
> undetectable. I doubt we can detect the pull of Venus, for instance.

It's not too hard to 'ballpark' the numbers: given that Venus has a
mass of about 80% of the earth's, and at inferior conjunction it's
about fifty million kilometres away, nearly eight thousand times the
distance from the earth's centre to the surface. Dividing 0.8 by
8000^2 yields an acceleration value of somewhat over ten billionths
(i.e. 10^-8) of one g -- as you say, pushing the limits of our
ability to detect. By way of comparison the pull of the moon is over
250 times as strong, and that of the sun nearly 50,000 times; another
way to get an idea of our experience of the gravity of Venus might be
to compare it to a ten-tonne weight two metres away.

--
Odysseus

BenignVanilla
July 31st 03, 02:58 PM
"Jonathan Silverlight" > wrote in message
...
> In message >, Andrew McKay
> > writes
> >On Wed, 30 Jul 2003 09:04:21 -0400, "BenignVanilla"
> > wrote:
> >
> >>Is this true? Gravity never quites get to 0? I am having one of those
> >>moments. This is shocking. Can someone expound on this? The concept
sounds
> >>very important. How far can we actually measure before we can't "sense"
the
> >>field anymore?
> >
> >Surely gravity is nullified when an object equi-distant from two
> >bodies having equal gravitational pull? In other words it's effect is
> >additive, suggesting that there is indeed a zero-gravity situation
> >available.
> >
>
> The forces are still at work. It's like a tug of war, equally balanced
> and just as unstable. After all, the moon pulls on the Earth even though
> it's well outside the sphere where the Earth dominates (and vice versa).
> Of course for other planets the force becomes so small it's
> undetectable. I doubt we can detect the pull of Venus, for instance.

So if it's undetectable...is it there? I am seriously asking, not being a
smart ass. I am curious how far out these fields go. I am wondering if some
day distant planets could be found based on some kind of signature.

BV.

Greg Neill
July 31st 03, 03:32 PM
"BenignVanilla" > wrote in message
...
> "Jonathan Silverlight" > wrote in message
> ...
> > In message >, Andrew McKay
> > > writes

> > >
> > >Surely gravity is nullified when an object equi-distant from two
> > >bodies having equal gravitational pull? In other words it's effect is
> > >additive, suggesting that there is indeed a zero-gravity situation
> > >available.
> > >
> >
> > The forces are still at work. It's like a tug of war, equally balanced
> > and just as unstable. After all, the moon pulls on the Earth even though
> > it's well outside the sphere where the Earth dominates (and vice versa).
> > Of course for other planets the force becomes so small it's
> > undetectable. I doubt we can detect the pull of Venus, for instance.
>
> So if it's undetectable...is it there? I am seriously asking, not being a
> smart ass. I am curious how far out these fields go. I am wondering if
some
> day distant planets could be found based on some kind of signature.

Venus along with all the other planets cause perturbations in
the Earth's orbit (and all of each other's orbits of course).
If you inspect, for example, VSOP87 theory which provides a
series of terms which, combined, predict planetary positions to
an excellent degree of accuracy, you'll find terms associated
with the various planets and even some asteroids.

Bill Sheppard
July 31st 03, 05:26 PM
BV wrote,

>I am wondering if some day distant
>planets could be found based on some
>kind of signature.

Why sure, BV. One signature of extrasolar planets curently being
detected is the 'Doppler-wobble' of the parent star. This site gives
some excellent graphics-

www.howstuffworks.com/planet-hunting2.htm

An earlier poster mentioned the barycenter of two co-orbiting bodies,
and how the barycenter can sometimes be below the surface of the larger
body. The Earth-moon system is one such example. See-

http://baby.indstate.edu/gga/gga_cart/gecar279.htm

oc

BenignVanilla
July 31st 03, 06:18 PM
"Bill Sheppard" > wrote in message
...
> BV wrote,
>
> >I am wondering if some day distant
> >planets could be found based on some
> >kind of signature.
>
> Why sure, BV. One signature of extrasolar planets curently being
> detected is the 'Doppler-wobble' of the parent star. This site gives
> some excellent graphics-
>
> www.howstuffworks.com/planet-hunting2.htm
>
> An earlier poster mentioned the barycenter of two co-orbiting bodies,
> and how the barycenter can sometimes be below the surface of the larger
> body. The Earth-moon system is one such example. See-
>
> http://baby.indstate.edu/gga/gga_cart/gecar279.htm

I am aware of the wobble test. I guess I was more or less pulling a Bert,
and thinking outloud...green light thinking as they say, no filtration. If
the gravity fields go on "forever" maybe we could look at a star that
wobbles, and know there is a planet there, and then measure the trace
gravitational field to learn more about the planet itself. Maybe no so iffy?
(yes)?

BV.

Greg Neill
July 31st 03, 07:31 PM
"BenignVanilla" > wrote in message
...

>
> I am aware of the wobble test. I guess I was more or less pulling a Bert,
> and thinking outloud...green light thinking as they say, no filtration. If
> the gravity fields go on "forever" maybe we could look at a star that
> wobbles, and know there is a planet there, and then measure the trace
> gravitational field to learn more about the planet itself. Maybe no so
iffy?
> (yes)?
>

Run some numbers on the expected magnitude of the gravitational
field of an entire sun-sized star at several light-year's
distance. Compare with that of a mosquito hovering at the
lab window.

There's a reason that it's taking so long to get LIGO
operational.

Ian W
July 31st 03, 08:28 PM
In article >,
says...

> > > wrote:
> So if it's undetectable...is it there? I am seriously asking, not being a
> smart ass. I am curious how far out these fields go. I am wondering if some
> day distant planets could be found based on some kind of signature.
>
> BV.

You're on the right track in your thinking. Astronomers currently measure
the eccentricity of rotation of stars to determine if they have large
planetary masses orbiting the star. This eccentricity or 'wobble' is
caused by the varying gravity influence of the planet travelling on it's
orbit and it's subsequent effect on the stars rotation. It should be
noted that the size of the planets currently discovered are all Jupiter
sized and larger.

Ian

Greg Neill
August 1st 03, 02:42 PM
"Ian W" > wrote in message
. ..
> In article >,
> says...
>
> > > > wrote:
> > So if it's undetectable...is it there? I am seriously asking, not being
a
> > smart ass. I am curious how far out these fields go. I am wondering if
some
> > day distant planets could be found based on some kind of signature.
> >
> > BV.
>
> You're on the right track in your thinking. Astronomers currently measure
> the eccentricity of rotation of stars to determine if they have large
> planetary masses orbiting the star. This eccentricity or 'wobble' is
> caused by the varying gravity influence of the planet travelling on it's
> orbit and it's subsequent effect on the stars rotation. It should be
> noted that the size of the planets currently discovered are all Jupiter
> sized and larger.

Strictly speaking, it's not the rotation of the star that's
seen to wobble, but the position of the star itself on the
sky. Also, if at least some of the motion lies in the
direction of the observer, the wavelengths of emitted
light will be seen to vary periodically (doppler shifting).

G=EMC^2 Glazier
August 1st 03, 07:23 PM
Hi Ian What you say means Jupiter will let life looking at our sun from
their solar system know that our sun has planets. They would be as smart
as us to know Jupiter is a gas planet,and is good to let viewers know
are system has planets.,but this type of planet has no life.
I don't think earth can make the sun wobble very much when the mutual
center of gravity is inside the sphere of the sun(under its surface)
This could be true for lots of sun like stars. Still if
there are gas planets there are rock planets in solar systems. Life from
a far is not stupid,and would know this. Bert

Ian W
August 1st 03, 08:02 PM
In article >,
says...
> "Ian W" > wrote in message
> . ..
> > In article >,
> > says...
> >
> > > > > wrote:
> > > So if it's undetectable...is it there? I am seriously asking, not being
> a
> > > smart ass. I am curious how far out these fields go. I am wondering if
> some
> > > day distant planets could be found based on some kind of signature.
> > >
> > > BV.
> >
> > You're on the right track in your thinking. Astronomers currently measure
> > the eccentricity of rotation of stars to determine if they have large
> > planetary masses orbiting the star. This eccentricity or 'wobble' is
> > caused by the varying gravity influence of the planet travelling on it's
> > orbit and it's subsequent effect on the stars rotation. It should be
> > noted that the size of the planets currently discovered are all Jupiter
> > sized and larger.
>
> Strictly speaking, it's not the rotation of the star that's
> seen to wobble, but the position of the star itself on the
> sky. Also, if at least some of the motion lies in the
> direction of the observer, the wavelengths of emitted
> light will be seen to vary periodically (doppler shifting).


I refer you to http://sim.jpl.nasa.gov/science/planet.html

Please note that what I stated is correct regarding measurement of
eccentricity of orbit as the eccentricity of orbit shows up as a movement
which is plottable over time.

Ian

Greg Neill
August 2nd 03, 01:47 AM
"Ian W" > wrote in message
. ..
> In article >,
> says...

> >
> > Strictly speaking, it's not the rotation of the star that's
> > seen to wobble, but the position of the star itself on the
> > sky. Also, if at least some of the motion lies in the
> > direction of the observer, the wavelengths of emitted
> > light will be seen to vary periodically (doppler shifting).
>
>
> I refer you to http://sim.jpl.nasa.gov/science/planet.html
>
> Please note that what I stated is correct regarding measurement of
> eccentricity of orbit as the eccentricity of orbit shows up as a movement
> which is plottable over time.

Perhaps it's a matter of semantics. Stars and planets both
rotate and orbit. "Rotation" is usually taken to mean
the rotation of the body about its axis (just as the Earth
rotates daily). The wobbles that are being measured are in
the position of the star as the star and planet mutually orbit.

Ian W
August 2nd 03, 07:22 AM
In article >,
says...

Hi Bert,

> Hi Ian What you say means Jupiter will let life looking at our sun from
> their solar system know that our sun has planets. They would be as smart
> as us to know Jupiter is a gas planet,and is good to let viewers know
> are system has planets.,but this type of planet has no life.

In theory yes. However if we assume there is an intelligent life form or
life forms that have science advanced enough to measure the eccentricity
of orbit of stars and from that deduce the fact that there is one or more
Jupiter sized large planets in orbit.

There are however a couple of caveats, the most important one is that the
'wobble' caused by a large planetary mass (ie: large planet like Jupiter)
is tiny and therefore detecting said wobble would be near impossible over
a distance of more than perhaps a few tens of parsecs. This statement is
based on the premise that the technology level of the hypothetical 'other
lifeforms' is comparable to our current level of technology.

> I don't think earth can make the sun wobble very much when the mutual
> center of gravity is inside the sphere of the sun(under its surface)
> This could be true for lots of sun like stars.

I guess you are refering to a star that's in the Red Giant phase?

> Still if there are gas planets there are rock planets in solar systems.
> Life from a far is not stupid,and would know this. Bert

I'd not make such a blanket assertion that where there are gas giant
planets there are rock planets. From what I understand of current
planetary formation theories a star formation region rich in heavy
elements is required to spawn small dense planets of comparable
composition to Earth, Mars etc.

Ian

Ian W
August 2nd 03, 07:30 AM
In article >,
says...

> Perhaps it's a matter of semantics. Stars and planets both
> rotate and orbit. "Rotation" is usually taken to mean
> the rotation of the body about its axis (just as the Earth
> rotates daily). The wobbles that are being measured are in
> the position of the star as the star and planet mutually orbit.

Exactly. The use of such terms also varies slightly from country to
country.

Jonathan Silverlight
August 2nd 03, 09:32 AM
In message >, Ian W
> writes
>In article >,
says...
>
>Hi Bert,
>
>> Hi Ian What you say means Jupiter will let life looking at our sun from
>> their solar system know that our sun has planets. They would be as smart
>> as us to know Jupiter is a gas planet,and is good to let viewers know
>> are system has planets.,but this type of planet has no life.
>
>In theory yes. However if we assume there is an intelligent life form or
>life forms that have science advanced enough to measure the eccentricity
>of orbit of stars and from that deduce the fact that there is one or more
>Jupiter sized large planets in orbit.
>
>There are however a couple of caveats, the most important one is that the
>'wobble' caused by a large planetary mass (ie: large planet like Jupiter)
>is tiny and therefore detecting said wobble would be near impossible over
>a distance of more than perhaps a few tens of parsecs. This statement is
>based on the premise that the technology level of the hypothetical 'other
>lifeforms' is comparable to our current level of technology.

I'll have to check one of the exoplanet sites, but isn't the point about
the new discoveries that we _can_ now detect the effect of a
Jupiter-size planet in a Jupiter-like orbit, and because the detection
depends on Doppler shift it doesn't matter how far away it is?
Similarly, detection of a planet in transit just depends on its being
large enough and on the small chance that we will catch it crossing its
sun.
And we are beginners at this game.
--
"Roads in space for rockets to travel....four-dimensional roads, curving with
relativity"
Mail to jsilverlight AT merseia.fsnet.co.uk is welcome.
Or visit Jonathan's Space Site http://www.merseia.fsnet.co.uk

,
August 2nd 03, 11:48 AM
"Jim" > wrote in message
...
> On Tue, 29 Jul 2003 06:01:14 -0400, "Ron Miller"
> > wrote:
>
> >
> >"Jim Jones" > wrote in message
> ...
> >> Hi.
> >>
> >> If it where possible to create or to send 2 incredibly huge boulders
> >> into outer space from Earth and just let them float out there , would
> >> they eventually revolve around each other ? Is that how masses in
> >> outer space work? They just find their gravitation point, and start to
> >> "do si do" ?
> >
> >More or less, yes.
> >
> >> What if launched from the moon ?
> >
> >Would make no difference.
> >
> >> Or, would our solar system reject them? If so, what would it do with
> >> these 2 new intruders, which did not come from way out there, but from
> >> our modest little planet ?
> >
> >The solar system could care less.
> >
> >> Would they hook up with the asteroid belt outside of mars ?
> >
> >Not necessarily. They would orbit wherever you launched them to.
> >
> >> Would they stay together at all, if when on earth they had absolutely
> >> no magnetic properties ?
> >
> >Gravity is the operator here, not magnetism.
> >
> >> Does the pull of gravity get stronger on larger planets and weaker on
> >> smaller planets ?
> >
> >Yes.
> >
> >> Why do the planets and moons pull (gravity) anyway? Is it because
> >> they're so large? Is it the activity at the core?
> >
> >It is because of their mass.
> >
> >RM
>
> Ron,
>
> Thanks for your prompt response and your help in clearing up those
> things, but I may be unclear on what you mean, in the last statement,
> about "It's their mass".
>
> Let me rephrase my question. And please don't think you're being too
> simple in answering:
> Q. Why does earth hang onto it's loose objects ? What about "mass"
> might I not be understanding.
>
> ALSO: Does gravity gradually drop off, as we get higher and higher
> into the atmosphere, OR, is there a fine line where gravity goes from
> gravity to no gravity?


You have to think of gravity as causing a shift in geometry, not
as a force.

Use this analogy, if two people were to start walking from
the same point on earth but at a small angle relative
to each other, they would appear to be walking
a straight line and their distance from each
other would steadily increase as they walked.

But as they continued walking eventually the
curvature of the earth would begin to close
the distance between them until they met
at the other side of the earth.

Both people would see themselves as walking
a straight line since they can't perceive the
curvature of the earth, yet in reality they
are tracing a parabolic curve. It's the hidden
geometry of the surface that creates this
apparant contradiction. The two meet
or seem to be attracted to each other
due to geometry, not because there
is some mysterious force pulling them
towards each other as they walked.

It is the same in space, two objects
launched in straight lines slightly
askew from each other would
seem to be attracted to each other
and curve back towards a collision.

But there is no force between them, their
mass has altered the geometry of space.
Since we can't directly perceive this
hidden geometry we assume there
is some mysterious force at a distance.
There is none.

The earth is traveling in a ..straight line
through curved space-time along a
geodesic created by the sun's mass.

Jonathan

s



>
> Thanks again,
> Jim
>

G=EMC^2 Glazier
August 2nd 03, 01:51 PM
Hi Ian I was told that there are two orbiting neutron stars that have
two planets orbiting these neutron stars. If true(told to me by beer
drinking buddy) and they are only 3 times larger than the earth this I
find interesting. Ian have you ever heard of this? Lots of
theories could come out of this,if true. Bert PS The best
clue nature gives us on gravity is. The greater the mass the stronger
the gravity field,and gravity creates mass density. That goes for
inertia as well,and if inertia and gravity are not the same they have to
be two sides to the same coin (I think they are one).

G=EMC^2 Glazier
August 2nd 03, 02:14 PM
To find the right stuff for life we have to go with our carbon
structure. We have to look for stars like our sun. If we find a gas
giant like Jupiter we have to assume there are rock planets as well(we
have 5 solid planets) Fiction writers can create silicon life.
Intelligent life that have all the features of of bugs.(many hands,and
eyes) We have to see,and look for life on what we know to be
reality "US" There is a sameness in the way nature constructs,and the
human body took a half billion years to come out right. Its our brain
that needs a lot more evolving to get it to have no fear,and treat
others with great kindness.knowing how lucky we are to share this
spacetime together on an earth that can give everyone a free lunch if we
work together,and love each other. Bert

Ian W
August 2nd 03, 04:57 PM
In article >,
says...

> I'll have to check one of the exoplanet sites, but isn't the point about
> the new discoveries that we _can_ now detect the effect of a
> Jupiter-size planet in a Jupiter-like orbit, and because the detection
> depends on Doppler shift it doesn't matter how far away it is?
> Similarly, detection of a planet in transit just depends on its being
> large enough and on the small chance that we will catch it crossing its
> sun.
> And we are beginners at this game.

Doppler spectography or more correctly Radial Shift measurement is one of
the four methods used and yes you're quite right regarding the size and
orbital characteristics that we can detect at present.

As far as I'm aware (I could well be wrong here) Radial Shift measurents
at present are limted to an accuracy of about 10 meters per second which
poses some limitations to the range of accurate measurements. No doubt in
time this will be greatly improved.

The other methods used are astometry, transit detection and optical
inteferometry which is a new method and at present mostly theoretical
unless the astronomers at C.O.A.S.T have been doing stuff I don't know
about.

Of the 4 methods optical interferometery is probably going to be the best
in the long term for imaging potential candidate planets.

Indeed we are but beginners at this game, the same also applies for SETI
research in general.

Ian W
August 2nd 03, 09:50 PM
In article >,
says...

Hi Bert,

I think your buddy is referring to the following:

http://news.bbc.co.uk/2/hi/science/nature/3053165.stm?from=astrowire

That system being visible is more of a fluke than anything else from the
look of it.

PS: YOur PS is too much for my brain to cope with at 4.50am after a
couple of bottles of red wine and a night of howling winds, driving rain
and other goodies.

> Hi Ian I was told that there are two orbiting neutron stars that have
> two planets orbiting these neutron stars. If true(told to me by beer
> drinking buddy) and they are only 3 times larger than the earth this I
> find interesting. Ian have you ever heard of this? Lots of
> theories could come out of this,if true. Bert PS The best
> clue nature gives us on gravity is. The greater the mass the stronger
> the gravity field,and gravity creates mass density. That goes for
> inertia as well,and if inertia and gravity are not the same they have to
> be two sides to the same coin (I think they are one).

Fred Williams
August 2nd 03, 10:18 PM
, wrote:


> It is the same in space, two objects
> launched in straight lines slightly
> askew from each other would
> seem to be attracted to each other
> and curve back towards a collision.
>
> But there is no force between them, their
> mass has altered the geometry of space.
> Since we can't directly perceive this
> hidden geometry we assume there
> is some mysterious force at a distance.
> There is none.
>
> The earth is traveling in a ..straight line
> through curved space-time along a
> geodesic created by the sun's mass.
>
> Jonathan
>

I like this interpretation for it's elegance. There is no need to
"invent" 'gravitons' or anything like that. "Space" can be thought
of as a property of matter and so curvature of space becomes a
natural cosequence, if so. I've no idea how this stands up in the
light of higher physics and mathematics, although I have a degree in
math., only.


--
Regards
Fred
>
Remove FFFf to reply, please

BenignVanilla
August 4th 03, 04:00 PM
"G=EMC^2 Glazier" > wrote in message
...
> To find the right stuff for life we have to go with our carbon
> structure. We have to look for stars like our sun. If we find a gas
> giant like Jupiter we have to assume there are rock planets as well(we
> have 5 solid planets)

Why must we assume? I don't think it is safe to assume all other solar
systems will mimic ours identically.

> Fiction writers can create silicon life.

I agree, this is a very valid thought experiment. Who is to say ALL life in
the universe is developing as ours has?

<snip>
BV.

G=EMC^2 Glazier
August 5th 03, 03:23 PM
BV Carbon is the building block to create life. To assume life
formed completly different than life forms on earth,is very "iffy"
thinking. We have millions and millions of different life forms on
earth to chose from. Bert

BenignVanilla
August 5th 03, 04:36 PM
"G=EMC^2 Glazier" > wrote in message
...
> BV Carbon is the building block to create life. To assume life
> formed completly different than life forms on earth,is very "iffy"
> thinking. We have millions and millions of different life forms on
> earth to chose from. Bert
>

I don't think it's iffy at all. Using the Earth as our only data set doesn't
IMHO dictate the universe. Life as we know it is carbon based and dependant
on water. That doesn't mean that ALL life in the universe is the same. I
think to assume that would lend to a margin of error that we cannot afford.
In a case like this, I think we need to remain open minded on the
possibility of life forming a different way somewhere else in the universe.
Clearly Moby has different needs then you right? So maybe the Bert on Planet
X is silicon based?

BV.

G=EMC^2 Glazier
August 6th 03, 04:05 PM
BV Moby has two eyes one brain,one heart. a mouth digestive system,and
breaths oxygen. He has lots of features different to help him
survive in a different medium(water). He can move in every direction.
Octopus like man are survivors because they can out think all other
animals that can do them bodily harm. When I look into Moby's eyes I
know he is looking back at me. I have the brain power of animals in
this order MAN, City Rat,and Octopus. Some will argue
monkeys.whales.after man(so be it) In the insect realm its
cockroaches,,bees.and horse flies. Bert

Dennis Taylor
August 6th 03, 04:32 PM
"G=EMC^2 Glazier" > wrote in message
...
> Octopus like man are survivors because they can out think all other
> animals that can do them bodily harm.

Nope. Octopi survive because they are physically adapted to their
environment. Just like cats and rats and elephants.

Typically the way this argument will go is that the opponent will respond by
giving examples of intelligent behaviour in octopi and daring me to declare
that this isn't intelligent behaviour. This is of course a straw man
argument, since there's a big difference between a rat being able to
navigate a maze, for instance, and declaring that a rat survives because it
is intelligent like humans.

The next thing that the opponent will do is point out that he's talking
about octopi, not rats, and therefore my point is invalid. I will then point
out that you can substitute "octopus" for "rat" in my statement, and it
still has the same meaning; but I used rats because I don't know if they've
put octopi through mazes.

The opponent will then go off into a long rambling diatribe about how we are
chauvinistic to define intelligence by our own standards, and that in its
own way an octopus is "intelligent", and how can I say that they aren't as
intelligent as humans in their own way. I will point out that the original
statement pretty specifically referred to a "human-type" intelligence, and
anyway if the statement referred to "octopus adaptation-type intelligence",
then the statement is true but trivial, basically saying "octopus survive
because they are good at being octopus". Ooh.

At this point, depending on temperament, the opponent will either go into
retreating definitions, trying to score and/or avoid being pinned down on
smaller and smaller points of the original argument, or will go into ad
hominim arguments, trying to discredit my arguments by attacking my
spelling, grammar, or character.

[sigh]

I may be being unfair to Bert on this, but it does get a little predictable
around here some times.

G=EMC^2 Glazier
August 6th 03, 10:57 PM
Dennis You are not unfair to me at all by expressing your personal
views on animal intelligence. You will notice I site city rats. Country
rats are not nearly as smart. I could write a book on Moby because we
are friends and we study each other. Truth is he likes showing me how
smart he is. I never gave him a treat every time he jumped through a
hoop. He would not jump through a hoop with or without a
treat(to smart for that) A duck can give the appearance of great
intelligence(play the piano and hit the right keys to a simple song.It
has no idea what it is really doing.. This kind of
controlling animal behavior by a treat after every trick does not really
show intelligence. NOVA had a show on the intelligence of the city
rat(what he could think out and do on its own) and it was more than than
running a maze. It was amazing Bert

Dennis Taylor
August 6th 03, 11:26 PM
"Bill Duncan" > wrote in message
et...
>I saw one time on the Discovery Channel an octopus unscrewing the lid
> of a jar to get to the crab inside.Let's see a rat do that.Bill.

Like I said:

> > Typically the way this argument will go is that the opponent will
respond by
> > giving examples of intelligent behaviour in octopi and daring me to
declare
> > that this isn't intelligent behaviour. This is of course a straw man
> > argument, since there's a big difference between a rat being able to
> > navigate a maze, for instance, and declaring that a rat survives because
it
> > is intelligent like humans.