Re: Two Questions...

This should be familiar to you -


"Gerald Kelleher (aka oriel36) is a celestial mechanics nut who thinks
that astronomy should have stopped with Kepler, and never gone on to
the
analytical universe of forces and accelerations put forth by Newton."

http://astro.isi.edu/reference/faq.html

If you are going to make a pathetic attempt to be technical then be
sure to get it right.I do not mind you subhuman grasp of astronomical
matters or what amounts to the same thing - your adherence to celestial
sphere geometry,I do mind that you cannot even compete with Newton.

Astronomy stopped at Roemer,after that Newton bundled the Keplerian
insight on orbital geometry with Roemerian insight on finite light
speed for his silly terrestial ballistics agenda -

"For to the earth planetary motions appear sometimes direct, sometimes
stationary, nay, and sometimes retrograde. But from the sun they are
always seen direct, and to proceed with a motion nearly uniform, that
is to say, a little swifter in the perihelion and a little slower in
the aphelion distances, so as to maintain an equality in the
description of the areas. This a noted proposition among astronomers,
and particularly demonstrable in Jupiter, from the eclipses of his
satellites; by the help of which eclipses, as we have said, the
heliocentric longitudes of that planet, and its distances from the sun,
are determined." Newton

Do you know what the above paragraph means as an accurate description
of Ptolemaic,Copernican,Keplerian and Roemerian reasoning ?, it means
absolutely nothing,it is junk and particularly that festering sore of
a first sentence.

I could not care less if you put my name on your site or not but if you
do so and try to squeek out a technical statement then be sure to get
it right.









Brian Tung wrote:
1. When a teacher at school was talking about how perfect the placing
of earth was, the nerdy guy in the class said "ya, if it were a few
inches closer to the sun, the glaciers would melt and destroy the
earth, and if it were a few inches away, then we would freeze to death"
I, actually knowing more and not usually showing it, pointed out that
the earth alternated from ~90-96 million miles away from the sun every
year and summer is actually further away than fall but... he said "no,
if the orbit was a few inches off" and i didn't want to start a huge
debate which would make me look like him but... I know that a tiny
deviation like 6 inches in orbit must happen all the time... such as
earthquakes and considering the mass of the moon, its orbit must move
the earth a few miles every month so... how much deviation from orbit
would it take for something catastrophic like a huge flood?

It would depend on how quickly the shift happened, but of course, six
inches would not make any kind of difference at all.

As you noted, the Earth's distance from the Sun varies by a few million
miles throughout the year, so at least that deviation, at that rate of
change, is noticeable, but hardly catastrophic. Some studies suggest
that the Earth could have formed within a fairly wide range of distances
from the Sun (typically from 0.9 AU to 1.4 AU) and still have permitted
liquid water, which is required for the kind of life we're familiar
with.

That doesn't mean, though, that the Earth's orbit could vary that much
*in a single year* and still support life. The Earth evidently has some
systems that act as a kind of buffer--systems such as the greenhouse
gases in the atmosphere (naturally as well as artificially).

If the Earth were further from the Sun, there is some feedback that
would liberate extra greenhouse gases and keep the planet warmer than it
would have been otherwise; if it were closer, some of the greenhouse
gases would go back into solution. Some of this is indicated by the fact
that life that depends on liquid water existed at a time when we know
the Sun to have been much cooler than it is today. Much more greenhouse
gas content was needed in order to sustain that life, and it must have
gradually been absorbed by rocks or ocean water as the Sun got warmer.

There's a limit, of course; you can't remove more greenhouse gases from
the atmosphere than there are to begin with. As the Sun continues to
warm, greenhouse gases will continue to depart the atmosphere in order
to maintain a reasonably comfortable equilibrium, but once they're all
gone, the increasing heat of the Sun will continue undeflected. It is
expected that within a billion years, our oceans will have completely
evaporated. Fortunately, a billion years is a very long time; we have
no reason to believe that human beings will still be around in any
event. The same kind of reasoning leads us to suggest that the Earth
couldn't be too much closer (about 0.9 AU) without overheating.

All these systems work as well as they do, however, because the changes
are relatively slow. They operate on geological time scales. They
couldn't work on time scales of a few months, which they would have to
if the Earth swung from between 0.9 AU to 1.4 AU within a single year!
It is even unclear whether the climate on the Earth can be held equable
when human influences are added in; these effects appear to operate on
the scale of several decades. We'll see.

2. I have been interested in astronomy lately and I wondered what are
the price ranges for telescopes? And are there any that you can sync
with your computer and see digital images/ type in long. and lat. and
it shows that part of the sky?

If you only want to observe visually, and don't need to involve a
computer/camera in the mix, they can be pretty inexpensive--maybe $200
U.S. will get you a decent six-inch telescope on a simple Dobsonian
mount. It's the steadiness and sky-following ability needed for
magnified photography and imaging that requires the mount to be
exceptionally stable and drives the price up. Computerizing the scope
so that it goes where you ask it to is relatively inexpensive, with
anywhere from one to a few hundred dollars being added to the price,
depending on how sophisticated the system is. By comparison, a steady
mount capable of doing single-shot long exposure imaging may be a
couple of thousand dollars on its own.

But yes, they're all available. One place to start is Orion:

http://www.telescope.com/

Their prices tend to be just a tad higher than competitors, but their
customer service is highly reputed.

--
Brian Tung <brian@xxxxxxx>
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.html

.

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