1. ## Shadow of sundial a straight line on equinox day?

On 31 Mar, 21:49, oriel36 <kelleher.ger...@gmail.com> wrote:
If you want to do this properly buy a globe of the Earth with the
correct axial tilt. Put a light or a candle in the centre of a table.
Point the north pole of the globe at your point representing Polaris
and, maintaiing this orientation move the globe round the candle. You
will note that you don't have to have any complicated extra orbital
motion to explain the seasons since it will be obvious that the Earth
rotates about it's tilted (with respect to the orbital plane) axis
which maintains its orientation with Polaris - or to put it another
way the "Celestial Sphere".
If you can't understand this there is something wrong with your brain

2. ## Shadow of sundial a straight line on equinox day?

oriel36 wrote:

Wow, it looks like you have finally been able to explain it in a way
that most everyone else here has understood all along. Now the big
question for you is, do you know why the rotational axis of the earth
(broomstick) remains fixed to the same distant point in space while the
earth orbits the sun? I have a feeling this is going to open a whole new
can of worms.

3. ## Shadow of sundial a straight line on equinox day?

On Mar 28, 7:19 pm, br...@lunabase.org (Brian Tung) wrote:

Thanks for the correction, Brian. I meant to say hyperbola and not
parabola. - Kurt

4. ## Shadow of sundial a straight line on equinox day?

On Mar 30, 7:30 am, Peter Lewis <kingkon...@gmail.com> wrote:

A basketball with markers taped to the poles and a flashlight at more
than 10 meters works.

There the NASA JPL Space Simulator may be of help:

http://space.jpl.nasa.gov/

For 2009, the equinoxes and solstices are at:

2009
Equinoxes Mar 20 11 44 Sept 22 21 18
Solstices June 21 05 45 Dec 21 17 47

Use March 20, 2009 at 11:44 UT in the simulator. Look at the Earth
from above and from "The Sun". Compare the position of the Earth as
seen from the Sun. The Sun will appear to be directly over the
equator. http://en.wikipedia.org/wiki/Equator

Because the Sun has no visual parallax when viewed from the Earth, the
rays of the Sun appear to be parallel, no matter whether you are look
at the Sun from a high latitude or from the equator. That's why the
Sun traces a visual straight line for all gnonoms.

Try running the simulator at other times of the year. You'll see that
the Sun does not appear to be directly over the equator. That's when
the Sun's shadow traces a hyperbola. Think in terms of conics - a
plane intersecting a sphere.

- Kurt

5. ## Shadow of sundial a straight line on equinox day?

On Mar 31, 7:02 am, Peter Lewis <kingkon...@gmail.com> wrote:

Hi
I thought I might add a little here. At the equinox, the suns shadow
would
follow the line of latitude where the person is located. For most any
location
that wasn't near the poles, this would seem to be a straight line,
although,
as drawn on the suface of the earth, it would curve, as all latitude
lines
do. If one had a truly flat board, not one that followed the Earth
curvature,
it would cast a straight line.
Dwight

6. ## Shadow of sundial a straight line on equinox day?

On Mar 28, 11:50 pm, oriel36 <kelleher.ger...@gmail.com> wrote

What a monstrous ego you have, to state that not one of the great
scientific minds of these times understands the basic dynamics of the
seasons, whereas you yourself know them perfectly. You are simply
delusional.

You are certainly correct when you lament the fact that it will be
more difficult than you thought to find even one person who thinks the
way you do...

7. ## Shadow of sundial a straight line on equinox day?

oriel36 wrote:

It is you who does not understand the *fundamental* cause of the seasons
if you can not explain why the earth's rotational axis remains fixed in
space towards the star Polaris while it (the earth) orbits the sun. If
you don't know the answer, it shouldn't take you more than a minute or
two to Google it. But of course the 'real' astronomers all ready know
the answer without having to look it up.

8. ## Shadow of sundial a straight line on equinox day?

Golden California Girls wrote:

I don't have to look it up. I've known about both of those phenomena
since I was a teenager. I didn't want to add more confusion to his
existent confusion. One step at a time.

Whoops, I'm feeding another troll.

9. ## Shadow of sundial a straight line on equinox day?

> On Apr 1, 8:16 pm, starman <star...@bluesky.net> wrote:

Let's forget about the global warming issue until you first give a
basing your understanding of the relationship between the inclination
(tilt) of the earth's rotational axis in relation to it's orbital plane
(around the sun), on imaging and other observations, which is fine.
However I'm asking you to explain the underlying principle of physics
which causes the observed behavior of the planets such as Uranus, which
you like to use as an example. Specifically, why does the earth's
rotational axis remain fixed to the same point in space, like your
broomstick analogy, while the earth orbits the sun? Or to put the
question in the negative, why *doesn't* the axis of the earth's rotation
always point *towards* the sun during it's annual orbit? If this were
true, it would be like the broomstick always pointing towards the basket
in the center of the room while the student walks around it. I think you
will agree that this is not the case but why? It might be helpful if you
do some research on a child's toy which is often used as an
instructional aid in a high school physics class. Hint: The name begins
with the letter 'G'.

10. ## Shadow of sundial a straight line on equinox day?

oriel36 wrote:

My only intention was to get you to do a little research to discover the
name and principles of the device or educational tool starting with the
letter 'G' which explains why the rotational axis of the earth remains
fixed to the same location in space, like your broomstick does in the
room. Haven't you ever wondered why this is so? I guess you made no
attempt to do that research. All I'm asking for is the name of that
device. If you can not provide it, you do not truly understand the
underlying physical principles which govern the behavior of any rotating
body, whether it be a planet or just a child's toy top. I imagine there
are more than a few readers here who are waiting to see if you can do
Last chance, what's the word?

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