Uncle Al wrote in message ...
Grok wrote:

Some of us computer scientists were sitting around, bored, and decided
to nudge the Earth towards the Sun. It'd be convenient if it would
hit within our lifetime, so we could finish at least one project on
time and under budget in our lifetimes!

I'm not a physicist, nor did I take enough math or physics to figure
this out, so would like your help.

My guessing says we have to slow the Earth's rotation so that its
gravitational acceleration to the Sun overtakes it's angular momentum,
allowing us to smack into the big one.

How much force is required to slow us down enough so that the big
splashdown is within 50 years?

Boy, are you ever muddled. The Earth masses 5.9742x10^27 grams. Its
average orbital acceleration around the sun (at 1 AU or 499.004782
light-seconds) is 0.593008 cm/sec^2. Stop it cold in its orbit, F=ma,
and it falls into the sun nice as you please. Was that so hard? Go
figure out how long a non-orbiting Earth requires to fall from here to
the sun and get back to us with your calculations,

[snip]

Let's see. It's been a long time I played with planet but...

I think Uncle Al that if you just stop the motion of the earth it's
total mechanical energy E will still be negative, E0 , due to just
the potential of the sun and it will again attain an elliptical orbit
around the sun but with some other radius and we will fry anyway.

It seems to me that in order to achieve what is called a "collision
path" or singular solution to orbit equations, one must increase the
total mechanical energy of the earth until it becomes E 0. Then
earth will go into an open orbit (hyperbola or parabola) and depending
on eccentricity, mean and ecccentric anomaly, you may achieve a
collision course.

Contrary to common sense, of mayne not, the only way to increase the
total mechanical energy of the earth is by increasing its velocity.
Then bingo, 7 Bil morons fry to their extinction and the universe is
safe. Slowing it down does not do the job it seems, unless you also
supply an impulse to increase the total mechanical energy to positive
number.

"DarkMatter" wrote in message
...
On Thu, 11 Sep 2003 21:06:44 -0700, "Richard Henry"
Gave us:


"DarkMatter" wrote in
message
.. .
On Thu, 11 Sep 2003 15:19:11 -0700, "Richard Henry"
Gave us:

I don't think slowing the Earth's rotation would help much.



Not for the fifty year thing, but it would certainly achieve more
motion toward the sun, Less centripetal force, yet the same
attractive force. You do the math. Pretty simple ****.

????



Dip****. It appears that you were talking about the earth's spin, I
was talking about its rotation around the sun.

Seems to be a problem with definitions of terms commonly used in phyics,
posted to a _physics_ newsgroup.

So who's the dip****?

"Undeniable" wrote in message
m...

Let's see. It's been a long time I played with planet but...

I think Uncle Al that if you just stop the motion of the earth it's
total mechanical energy E will still be negative, E0 , due to just
the potential of the sun and it will again attain an elliptical orbit
around the sun but with some other radius and we will fry anyway.

Nope. It will be in a degenerate straight-line orbit
intersecting the Sun.

Hey, when you drop something on the Earth, does it go into
an elliptical orbit instead of hitting the ground?

In article , (Undeniable) writes:
I think Uncle Al that if you just stop the motion of the earth it's
total mechanical energy E will still be negative, E0 , due to just
the potential of the sun and it will again attain an elliptical orbit
around the sun but with some other radius and we will fry anyway.

Total mechanical energy is positive. Total mechanical energy
plus potential energy (counting at infinity as the zero point for
potential energy so that potential energy is increasingly negative
as you go down the gravity well) can be negative (and constant)
all the way from the Earth's current orbit to splashdown at the
surface of the sun.

It seems to me that in order to achieve what is called a "collision
path" or singular solution to orbit equations, one must increase the
total mechanical energy of the earth until it becomes E 0.

A straight drop will do it. No need to aim at the sun with a
speed in excess of escape velocity.

A collision orbit is merely an orbit that intersects with the
surface of the object you are orbitting.

A baseball thrown in Fenway is on a collision orbit with the
Earth. This is true even though the baseball is thrown at far
less than 25,000 miles per hour.

Then
earth will go into an open orbit (hyperbola or parabola) and depending
on eccentricity, mean and ecccentric anomaly, you may achieve a
collision course.

You can achieve a collision course with any orbit. Ray,
Ellipse, Hyperbola, Parabola, Circle.

(Though you do tend to need to put a mountain in the way in
order to get a circular orbit to collide with the planet surface).

Contrary to common sense, of mayne not, the only way to increase the
total mechanical energy of the earth is by increasing its velocity.
Then bingo, 7 Bil morons fry to their extinction and the universe is
safe. Slowing it down does not do the job it seems, unless you also
supply an impulse to increase the total mechanical energy to positive
number.

No.


Now...

While bringing the Earth to a complete stop will do the job, one
can accomplish the task with slightly less force. We don't need
a straight-line drop. We merely need an elliptical orbit that is
sufficiently elongated so that the low point on the orbit just
grazes the surface of the sun.

One can approximate this by figuring that the velocity at
this low point will closely approximate solar escape velocity.
Multiply by the radius of the sun and you have angular momentum
at impact. Divide by the radius of the Earth's current orbit
and you have tangential velocity there. Subtract this figure
from the Earth's current velocity and multiply by the Earth's mass
to figure out how much braking impulse you need to deliver.

I suspect that a gravity-assisted trajectory using Jupiter would
save you a lot.

John Briggs

Greg Neill wrote:

"Undeniable" wrote in message
m...

Let's see. It's been a long time I played with planet but...

I think Uncle Al that if you just stop the motion of the earth it's
total mechanical energy E will still be negative, E0 , due to just
the potential of the sun and it will again attain an elliptical orbit
around the sun but with some other radius and we will fry anyway.

Nope. It will be in a degenerate straight-line orbit
intersecting the Sun.

Hey, when you drop something on the Earth, does it go into
an elliptical orbit instead of hitting the ground?

KISS - keep it simple, stupid. Stop the Earth dead in its orbit, let
the sun do the rest of the work work, and get a default perfect hit in
the bargain (less Lens-Thirring frame dragging just before
touchdown). Note the prior post regarding crush strength of the
Earth.

The original poster has not calculated corrected time to splatter nor
velocity at hit,

http://www.math.ubc.ca/~israel/m215/.../falling2.html

suggesting it was just noise not inquiry.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!

An impact from the milky way at 6000 mps mass of 8 gigaton followed by
the same in .005 seconds as the first impact soaked uo thhe resistance
to impulsive force and the second impact slowed the earths orbit we Dont
have to hit the sun to die we could just fry.

"DarkMatter" wrote in message
...

Of course, the spinning or non spinning globe would yield the same
results in the scenario which is being discussed. Slowing its
rotational progression around the sun *would* have an effect, however.

"Rotational progression around the sun"? Do you mean orbital velocity?

DarkMatter wrote:

On Fri, 12 Sep 2003 07:01:57 -0700, "Richard Henry"
Gave us:


"DarkMatter" wrote in message
.. .
On Thu, 11 Sep 2003 21:06:44 -0700, "Richard Henry"
Gave us:


"DarkMatter" wrote in
message
.. .
On Thu, 11 Sep 2003 15:19:11 -0700, "Richard Henry"
Gave us:

I don't think slowing the Earth's rotation would help much.



Not for the fifty year thing, but it would certainly achieve more
motion toward the sun, Less centripetal force, yet the same
attractive force. You do the math. Pretty simple ****.

????



Dip****. It appears that you were talking about the earth's spin, I
was talking about its rotation around the sun.

Seems to be a problem with definitions of terms commonly used in phyics,
posted to a _physics_ newsgroup.

So who's the dip****?


Rotation, can be rotation around the sun, OR rotation on its axis.
Since the topic surrounds the sun, I assumed the rotation referred to
was that rotation. I guess assuming you had a clue was too much.

Of course, the spinning or non spinning globe would yield the same
results in the scenario which is being discussed. Slowing its
rotational progression around the sun *would* have an effect, however.

You are the dip****.

A body rotates about an internal axis and revolves around an external
body.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!

DarkMatter wrote:

On Fri, 12 Sep 2003 11:18:59 -0400, "Greg Neill"
Gave us:

"Undeniable" wrote in message
om...

Let's see. It's been a long time I played with planet but...

I think Uncle Al that if you just stop the motion of the earth it's
total mechanical energy E will still be negative, E0 , due to just
the potential of the sun and it will again attain an elliptical orbit
around the sun but with some other radius and we will fry anyway.

Nope. It will be in a degenerate straight-line orbit
intersecting the Sun.

Hey, when you drop something on the Earth, does it go into
an elliptical orbit instead of hitting the ground?

Depends on how close you are to the spheroid, dip****.

No it does not. Stuff with zero orbital velocity falls straight down
vs. the fixed stars from any arbitrary height (ignoring wind) If you
look locally you subtract out ground motion and allow for ~1 cm/sec
horizontal Coriolus acceleration varying with latitude.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!

"DarkMatter" wrote in message
...
On Fri, 12 Sep 2003 11:18:59 -0400, "Greg Neill"
Gave us:

"Undeniable" wrote in message
om...

Let's see. It's been a long time I played with planet but...

I think Uncle Al that if you just stop the motion of the earth it's
total mechanical energy E will still be negative, E0 , due to just
the potential of the sun and it will again attain an elliptical orbit
around the sun but with some other radius and we will fry anyway.

Nope. It will be in a degenerate straight-line orbit
intersecting the Sun.

Hey, when you drop something on the Earth, does it go into
an elliptical orbit instead of hitting the ground?

Depends on how close you are to the spheroid, dip****.

The globular clusters in your skull cavity only weigh
2 grams.

DarkMatter earns a place in the hall of shame for failing
to think before spewing, and then being rude about it.

Clearly, if the planet has zero angular momentum about
the primary and no radial velocity, it must subsequently
fall straight in.

One wonders if Darkmatter (Dull Grey Matter?) has any clue
at all. What is this nonsense about proximity to some
spheroid?