When I said the orbits of the planets and comets were regular, I was
corrected by the comments that gravational interference from other bodies
does alter the periods of orbits. What I was thinking when I said that,
is that without outside interference the orbits are regular and
predictable - e.g. the earth and moon orbits. I forgot that the orbits
of comets, which are of comparatively low mass, are easily altered by
planets.
My point in saying that orbits are regular was to say that orbits are
very much like a pendulum used to drive a clock. Each can be used to
measure time. YECs have used short period comets to support a young
earth, which I feel is unreasonable. However, I don't recall ever having
seen OECs use long period comets as a measure of long ages.
In my mind, long period comets are a clean measure of millions of years.
Comet orbits have none (that I can see) of the "assumptions" that YECs
present to discredit OEC arguments such as radioactivity, speed of light,
etc. If a comet enters the solar system with a velocity high enough to
suggest it has been "falling" for millions of years, what YEC argument
would negate the conclusion that it really has been traveling that long?
I have been able to accept the suggestion that God created with apparent
age, but I have never been comfortable with the idea that God would
create, for example, fossils in primary rocks. Long comet orbits strike
me at this time as being more akin to fossils than to light from distant
stars.
I had some questions re comet orbits/velocities which I didn't see
answered here, so I asked Tom Van Flandern (website link below). For
those who might be interested, and with Tom's permission, my questions
and his answers are copied below.
Bill Payne
> what is the difference between a hyperbolic and parabolic
orbit?
Both are standard geometric shapes. Both are open. They are
the open-orbit counterparts of circles and ellipses. Just as
all circles have the same shape (e = 0) while ellipses have
a variety of shapes (0 < e < 1), all parabolas have the same
shape (e = 1) while hyperbolas have a variety of shapes (e >
1). [e = eccentricity.]
> Couldn't both be open, so that a comet with either orbit would
> not return to the solar system?
That is true. Both are always open, escape orbits.
> Aren't all comets gravitationally bound to the sun?
All *periodic* comets are bound to the Sun at the present
time. *New* comets (those arriving from the "Oort cloud"
(which I maintain does not exist) always arrive on bound
orbits, although only marginally bound. However, the binding
is so marginal that the tiny impulses these comets get from
planets are enough to change half these orbits to unbound as
they leave the planetary region, never to return.
> If one were not, would the only determining factor be the velocity,
> i.e., its velocity would have to be greater than the escape velocity
> from the sun?
That is true.
> I don't see where the shape of the orbit would affect whether a comet
> was gravitationally bound to the sun.
Generally, orbits are ellipses. But if a comet receives a
speed boost such that it goes faster than escape velocity,
it never returns. Its orbit is therefore open by definition.
The shape of the path it follows is a hyperbola
(approximated by a parabola in some cases). Speed determines
boundedness and shape together. They go hand-in-hand.
> I reviewed your book to see if you said that we have seen a comet with
> a period of 3 million years, and I couldn't find that statement.
All "new" comets have periods of millions of years. All are
possibly consistent with 3.2 million years. The more
accurately the orbit is determined, the closer the period is
to 3.2 million years. [This property is not obvious. See my
paper "The Exploded Planet Hypothesis -- 2000" at
<http://metaresearch.org>, "Solar System" tab, "EPH"
sub-tab.)
> What is the longest period comet we have observed?
Unbound comets have infinite period. The most loosely bound
comets have observational uncertainties that overlap
(unbound) infinite period.
> I would assume that we have seen comets with periods longer than a
> couple of thousand years. Is that correct?
Yes. Comets with periods less than 100 years are classified
as "short period". Comets of more than one observed return
in human history are classified as "periodic comets". The
majority of newly discovered comets (as opposed to
dynamically "new" comets) have periods of thousands of years
or more. Best wishes. -|Tom|-
This archive was generated by hypermail 2b29 : Fri Jan 12 2001 - 23:06:13 EST