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Thoughtsoc
2011-Jan-25, 03:35 AM
I can't quite wrap my mind around this. Suppose one could approach a distant galaxy, in a space ship for example. The galaxy, I assume, would become larger and larger but still be distinguishable as a galaxy--filling up the entire view in one direction. As one moved closer to the first stars in the galaxy, the shape of the galaxy would no longer be seen. But when the full shape could be seen, I would think this would be the most remarkable sight. Am I correct on this? Has anyone attempted a rendering of such a sight?

Jens
2011-Jan-25, 03:47 AM
I can't quite wrap my mind around this. Suppose one could approach a distant galaxy, in a space ship for example. The galaxy, I assume, would become larger and larger but still be distinguishable as a galaxy--filling up the entire view in one direction. As one moved closer to the first starts in the galaxy, the shape of the galaxy would no longer be seen. But when the full shape could be seen, I would think this would be the most remarkable sight. Am I correct on this? Has anyone attempted a rendering of such a sight?

Your impression sounds correct to me. I agree it would be a formidable sight. And I'm not aware of any films with scenes like that, but maybe someday knows of some.

Middenrat
2011-Jan-25, 04:08 AM
I doubt CGI could render the grandeur of such a sight. But if your sun had been ejected perpendicular to the galactic plane some billions of years ago then your night sky might be dominated by the horizon-to-horizon glory of your mother galaxy.
With my luck it would be an elliptical ;)

loglo
2011-Jan-25, 04:42 AM
Don't forget that surface brightness (http://en.wikipedia.org/wiki/Surface_brightness) is inversely proportional to distance and not to distance squared. As you approach the galaxy it would not get any brighter, but you would see greater detail. I'm not sure if the sight would be as spectacular as a Hubble photo of the galaxy taken from much farther away but integrated over a much longer time.

As far as depictions go, I seem to recall someone on this forum stating that the galaxy in the background of the final scene of "Empire Strikes Back" was not realistic. (Youtube vid (http://www.youtube.com/watch?v=hQjXlhfd1cA), 1:00 mark)

Jeff Root
2011-Jan-25, 12:47 PM
I expect that several examples of zooming in on (or out of) galaxies
in films will be given, but the only examples that come to my mind
are of films that I haven't seen in many years, and I don't know how
good they were. In particular, one of my favorite films of all time,
and only eight minutes long, "A Rough Sketch for a Proposed Film
Dealing with the Powers of Ten and the Relative Size of Things in the
Universe" (1968) by Charles and Ray Eames. As the title suggests,
it was roughly done. The effects are relatively crude. So I don't
think the zoom-in/out was technically noteworthy. The other film
is a more finished version titled "Cosmic Zoom" (1977) made with
physicist Philip Morrison. I prefer the original, with the voice of
narrator Judith Bronowski.

I expect that some of the TV science series, such as the History
Channel's "The Universe", include more impressive zoom-ins of
the Milky Way.

-- Jeff, in Minneapolis

ngc3314
2011-Jan-25, 01:45 PM
Don't forget that surface brightness (http://en.wikipedia.org/wiki/Surface_brightness) is inversely proportional to distance and not to distance squared.

No, surface brightness is independent of distance (as long as the situation is local enough for Euclidean geometry to be an adequate approximation). This means that, for example, the naked-eye view at close range would be at least as detailed as the best view you ever have at the eyepiece of any telescope (since passive optical systems cannot increase surface brightness). You could not match long CCD exposures, but many spiral arms would appear, and lots of galaxy bulges would show the characteristic yellowish-orange of red giants. And seen from close-up, lots of galaxies have fine detail in the form of star-forming regions that would become more and more prominent.

Rhaedas
2011-Jan-25, 04:00 PM
There's this: http://www.youtube.com/watch?v=P0-lsyo28SU

A demo of a galactic model generated procedurally in real time for the hopeful MMO Infinity. It starts off inside the galaxy, but journeys out some so you can see the big picture. Not exact, but it gives a good idea maybe.

Hungry4info
2011-Jan-25, 05:32 PM
If I'm not mistaken, the galaxy would appear rather dim, and a definite letdown to anyone who was hoping for something resembling an HST image.
Go out at night, look at the Milky Way. Now imagine being further from it. Impressive sight, sure, but still rather dim.

chornedsnorkack
2011-Jan-25, 05:37 PM
No, surface brightness is independent of distance (as long as the situation is local enough for Euclidean geometry to be an adequate approximation).

Yes, but it is not independent of view direction.

jaeger
2011-Jan-25, 08:56 PM
If I'm not mistaken, the galaxy would appear rather dim, and a definite letdown to anyone who was hoping for something resembling an HST image.
Go out at night, look at the Milky Way. Now imagine being further from it. Impressive sight, sure, but still rather dim.

I have always loved the work of Mark A. Garlick, especially his "Spiral Metropolis" (2000). http://www.space-art.co.uk/en/artwork/galaxies/spiral-galaxy-rising.html. From what you are saying, I assume that this angle and presumed distance, the galaxy would still be diffuse and dim. Too bad.

On a smaller scale, how plausible is Dan Durda's "Emerald Sea" (June 1998)? http://www.boulder.swri.edu/~durda/emerald_sea.jpg

Finally, the short story that got me hooked on Sci-Fi over 50 years ago was "Nightfall" by Asimov. Plausible or are planets within globular clusters fairly unlikely?

Thoughtsoc
2011-Jan-25, 11:32 PM
The youtube video was great. Thanks! The Garlick painting is what I imagined a galaxy would look like if one was the right distance from it. In reality, it perhaps couldn't be so bright. But as one moved closer and closer, it would have to take up more room in the sky. Eventually, I would think the entire image would be visible to the naked eye. Yet the closest points in the image would still be light years away from each other--80,000 years apart on the fastest spaceship, perhaps. That's what I can't quite fathom.

Thanks for the replies!

chornedsnorkack
2011-Jan-26, 12:08 PM
Note that we cannot see most of Milky Way because of Great Rift.

We are in the Milky Way disc and can see both the outer disc and the branches of inner disc around Great Rift because they are concentrated in a narrow band. The disc right around us is there just as well, but we cannot see it because it is diffused over sky.

If we were to leave the Milky Way disc then we should still be seeing exact same total amount of light from the outer disc - but the surface luminosity should fall as the luminosity is spread over larger area, and the outer Milky Way should fade out of sight.

Whereas we should be seeing much more total light from inner Milky Way as soon as we can see around Great Rift - we should see the inner arms, bar, bulge and core unobstructed. Would the inner Milky Way also have higher surface luminosity than what could be seen from Sun?