But... how can we KNOW what is out there NOW?

so... we see fossil light.
a vast array of billions of galaxies and all the rest.
ancient light reveals millions or billions of images of what was.

but what about NOW?

how do we know that, for instance, andromeda is still there?
how do we know that it hasnt exploded and the first tremors of a tidal wave of
energy arent headed this way?

rather than the most brilliant informed assumptions, i am asking how do we know
about NOW?
are there concrete means of calculation?
means of sensing reality beyond waiting for the lightspeed messabes to arrive?

most people seem to rationalize--- best-guessing gropes for generalizations
based upon solar system objects or localized phenomena--- a visibility within
nanoseconds, or hopeful intrapolations to support probability, etc.

but...
can we prove--- without assumptions or the most imformed guessing--- that
remote objects whose ancient ghost images we observe--- exist NOW???

signed...
Clueless1

Scribe2b wrote:
rather than the most brilliant informed assumptions, i am asking how do
we know about NOW?
are there concrete means of calculation?
means of sensing reality beyond waiting for the lightspeed messabes to
arrive?

No. But most of these other alternate possibilities (something blowing
up a galaxy, for instance) are vanishingly improbable, and since you can
think up any number of vanishingly improbable things, we don't worry
about them. At least, not within the realm of science.

Brian Tung
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.txt

Scribe2b wrote:
so... we see fossil light.
a vast array of billions of galaxies and all the rest.
ancient light reveals millions or billions of images of what was.

but what about NOW?

One of the big problems with so many trolls (are you listening Shawn and
your friends?) is that it becomes increasingly difficult to tell the
difference between an honest question and a troll. Particularly when
the poster uses a silly alias.

Anyhow, one perfectly good answer to your question is that there is no
such thing as "now".

Another perfectly good answer is that the light time is of little matter
to our understanding; just another factor to take into account (or
explit to our advantage). It's like thunder and lightening without the
lightening. Even if there were only thunder and it took many seconds to
arrive, you'd still be able to describe the lightening bolt.

If you are truly interested in the answer to this and other questions I
suggest you visit your nearest college bookstore and purchase a basic
101 astronomy text. They are all written at level most people can
readily understand and there is little/no math.

Clear skies,
Greg

--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools Software for the Observer:
http://www.skyhound.com/cs.html

Skyhound Observing Pages:
http://www.skyhound.com/sh/skyhound.html

On 12 Sep 2003 16:06:10 GMT, (Scribe2b) stepped up to
the plate and batted:

so... we see fossil light.
a vast array of billions of galaxies and all the rest.
ancient light reveals millions or billions of images of what was.

but what about NOW?

how do we know that, for instance, andromeda is still there?
how do we know that it hasnt exploded and the first tremors of a tidal wave of
energy arent headed this way?

rather than the most brilliant informed assumptions, i am asking how do we know
about NOW?
are there concrete means of calculation?
means of sensing reality beyond waiting for the lightspeed messabes to arrive?

most people seem to rationalize--- best-guessing gropes for generalizations
based upon solar system objects or localized phenomena--- a visibility within
nanoseconds, or hopeful intrapolations to support probability, etc.

but...
can we prove--- without assumptions or the most imformed guessing--- that
remote objects whose ancient ghost images we observe--- exist NOW???

signed...
Clueless1

Define "now"

G../0

rolls (are you listening Shawn and
your friends?) is that it becomes increasingly difficult to tell the
difference between an honest question and a troll.

no intention to troll.
and i appreciate your response.
jc

Define "now"

I guess it depends on what "is" is.
However, since we seem to find objects receding at a greater acceleration the
farther back we look, we must necessarily believe that the acceleration is
decreasing since it is less nearer us in space and time. So perhaps the
universe is contracting but we will not see it until we get squashed....

Clear, Dark, Steady Skies!
(And considerate neighbors!!!)

Stephen Paul wrote:
So, again, to us the universe is, for all intents and purposes, a sphere.
Even if the mathematical model of a big bang everywhere all at once dictates
otherwise.

Is that making any sense to anyone?

Sure, it makes sense to me. Another way of looking at it is that a
fundamental property of the Universe is that every observer believes
he/she is at it's center. That thought always brings a chuckle...
explains a lot doesn't it? ;-)

Clear skies,
Greg

--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools Software for the Observer:
http://www.skyhound.com/cs.html

Skyhound Observing Pages:
http://www.skyhound.com/sh/skyhound.html

In article ,
Scribe2b wrote:
so... we see fossil light.
a vast array of billions of galaxies and all the rest.
ancient light reveals millions or billions of images of what was.

but what about NOW?

how do we know that, for instance, andromeda is still there?
how do we know that it hasnt exploded and the first tremors of
a tidal wave of energy arent headed this way?

....and what about tomorrow, or in 200 years, or in 2 million years?

It's really the equivalent case: we cannot know, from observation,
what the Andromeda Galaxy is like "now" until a few million years into
the future. Is there a supernova there "now"? We won't see it until
a few million years has passed, so its light can reach us....

rather than the most brilliant informed assumptions, i am asking how
do we know about NOW?
are there concrete means of calculation?
means of sensing reality beyond waiting for the lightspeed messabes
to arrive?

Well, we do have quite sophisticated models for stellar evolution and
even galactic evolution, which we can use for prediction purposes.
Is that what you mean with "concrete means of calculation"?

most people seem to rationalize--- best-guessing gropes for generalizations
based upon solar system objects or localized phenomena--- a visibility within
nanoseconds, or hopeful intrapolations to support probability, etc.

but...
can we prove--- without assumptions or the most imformed guessing--- that
remote objects whose ancient ghost images we observe--- exist NOW???

Of course not! We must for instance assume that the same natural
laws are valid there as here (one aspect of "the cosmological
principle"). If that's not the case, then we know absolutely nothing.

And that's the case with all our knowledge: it's based on at least
_some_ assumptions, assumptions which appears to remain valid through
an extremely large number of observations and therefore we trust
them. But we're still dependent on these assumptions.

Absolute proofs exist only in mathematics and in formal logic, but
not in the natural sciences.


--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://www.stjarnhimlen.se/
http://home.tiscali.se/pausch/

Similarly, time is also relative. We think of "now" having meaning, but
it's really just an illusion. All human beings are relatively close to
one another and moving at about the same speed. So we can cheat and
define a common "now."

still, i ask, if light travels X number of years from Andromeda to reach us,
and if Andromeda ripped itself apart X-1 years ago in our time, then next year
we would be in for a very unplesant surtprise.

is there no way to detect such events other than waiting upon the speed of
light?

jc

Jere wrote:
is there no way to detect such events other than waiting upon the speed of
light?

As far as we know, there is no way for information to travel faster
than the speed of light. If there were no warning for inhabitants
of M31, then there would be no warning for us, either.

Brian Tung
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.txt