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Author Topic: The Universe  (Read 878 times)
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Donotremove
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« Reply #45 on: March 06, 2008, 03:27:08 PM »

Noneoftheabove, as far as I understand it, the "pictures" are digital.  They have no color.  NASA adds the color for better visuals for the general public.
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weezo
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« Reply #46 on: March 06, 2008, 04:42:00 PM »

Thanks, None Of,

As you say, now that the issue has come up, curiousity reigns! I am curious what information is in those other spectra and what it may add to what the picture shows. It may be information that I can add to my website for students.
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NoneoftheAbove
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« Reply #47 on: March 06, 2008, 05:42:26 PM »

Noneoftheabove, as far as I understand it, the "pictures" are digital.  They have no color.  NASA adds the color for better visuals for the general public.

I believe that's right (though I'm ready to be corrected). Certainly they are digitized for transmission. The question that remains for me and Weezo regards whether there are overlays from other than visual spectrum cameras, and if so, what those other images contributed to the visual composite that was published in USA Today. 
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obertray
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« Reply #48 on: March 06, 2008, 05:44:38 PM »

You were right, this is much more interesting...
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obertray
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« Reply #49 on: March 06, 2008, 06:02:31 PM »


Sheesh. From space (the vantage from which the picture is taken) DOWN would be AWAY from the orbiter, UP would be TOWARD the orbiter, just as in any overhead shot taken on earth. BELOW would be BELOW the steep cliff where the avalanch started ... let's not be coy, eh?

Without the slightest intent at coyness. And without the intent of semantics. I'd like to converse about your definition of down and up.

You say that any direction away from the orbiter is down. Why isn't it more appropriate to say the any direction away from the orbiter is across?

Now, as to overhead shot (you brought it up not me). Let's say that you are standing and you are holding the camera pointed at the top of your head and your shoes (assuming they are big enough). It is absolutely clear to all that this is an overhead shot and that relative to the planet the camera is up, and pointed down. But this is not true relative to the satellite.

The satellite is up from the surface but the surface is across from the satellite (not down).
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NoneoftheAbove
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« Reply #50 on: March 06, 2008, 06:18:24 PM »

Ober, I must confess that I don't understand your question, unless you are presuming that the MRO is not looking straight down, but toward a horizon. I assume that the MRO, like the mapping satellites, looks pretty much straight down when it takes pictures. This is so because of a couple of factors - for one, the objects directly below the orbiter are the closest, and for another, shooting straight down keeps the perspective consistent so that adjacent shots can be edge-mapped.

Of course that may not necessarily be the case with a particular picture. If, in this case, the camera is pointed toward a horizon (across), rather than straight down, I'd expect the picture to be presented so that the farthest objects were toward the top of the frame. Still, at the altitude (?) from which this thing is looking, very little relief would be visible.
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Kam
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« Reply #51 on: March 06, 2008, 06:44:59 PM »

We're looking at the planet from above.  The pic could be in practically any orientation and still make sense.
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obertray
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« Reply #52 on: March 06, 2008, 07:48:29 PM »

"Ober, I must confess that I don't understand your question, unless you are presuming that the MRO is not looking straight down, but toward a horizon."

No, it's [what I'm saying is] more like, There is no "dwon from the satellite there is only across. There is only down  to those for whom the satellite is up. Down doesn't mean anything in space.

Is Mars down from the moon? Is the Sun down from Mars, and Jupiter, is it also down from Mars?

If you are on the Moon, Earth is up. If you are off the Moon you go down to the Earth? No you go across to the Earth.

This having been said, there must be some point where you are now headed down.

By this one might speculate that up and down are a function of gravity alone.

Do I make my question clearer?
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NoneoftheAbove
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« Reply #53 on: March 06, 2008, 08:31:01 PM »

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Down doesn't mean anything in space.

Ober, you gotta understand that that is simply not true. Up and down exists wherever there is a mass close enough to predominate local gravitational effects. If you stopped the orbital momentum  of the MRO satellite directly above that landslide area, it would fall down onto that area*.  An satellite or individual in orbit around, say a planet, doesn't sense the planet's gravity, because he's in continuous free fall around  it, a state prolonged by his orbital velocity. But he IS being effected by the planet's gravity.

So, if you're in a gravity well, looking "down-well" is looking toward the center of proximate mass whether you're standing on it or looking at it from "above". even if you're screaming along in orbit.

"Down" loses physical meaning when you get to DEEP space, but not for MRO.

* (actually only very near it, because of Mars' rotational velocity).
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NoneoftheAbove
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« Reply #54 on: March 06, 2008, 08:43:57 PM »

OK, I got this:

a link to what appears to be the program page

Quote
It was taken on February 19, 2008, by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. ...
All images are false color.

and this, which gives some more details about the picture


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The complete image, HiRISE PSP_007338_2640, is centered at 83.7 degrees latitude, 235.8 degrees east longitude. The image was taken at a local Mars time of 1:05 PM and the scene is illuminated from the west with a solar incidence angle of 70 degrees, thus the sun was about 20 degrees above the horizon. At a solar longitude of 34.0 degrees...

and..

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HiRISE operates in visible wavelengths, the same as human eyes, but with a telescopic lens that will produce images at resolutions never before seen in planetary exploration missions. These high resolution images will enable scientists to resolve 1-meter (about 3-foot) sized objects on Mars and to study the morphology (surface structure) in a much more comprehensive manner than ever before.
HiRISE also makes observations at near-infrared wavelengths to obtain information on the mineral groups present. From an altitude varying between 200-400 kilometers (about 125 to 250 miles) above Mars, HiRISE will return surface images that contain individual basketball-sized pixel elements (30-60 centimeters, or 1 to 2 feet wide), allowing surface features 4-8 ft across to be determined (resolved). These new, high-resolution images will provide unprecedented views of layered materials, gullies, channels, and other science targets, as well as characterize possible future landing sites.

Y'all's turn to do the digging next time.

« Last Edit: March 06, 2008, 08:49:06 PM by NoneoftheAbove » Logged

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NoneoftheAbove
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« Reply #55 on: March 06, 2008, 08:50:33 PM »

We're looking at the planet from above.  The pic could be in practically any orientation and still make sense.

Zackly. Phwew.
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weezo
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« Reply #56 on: March 06, 2008, 09:18:44 PM »

OK, I think I get it! The top of the mountain/dome is to the left (the white with visible chunks missing), the area in the middle is the cliff jutting out of the mountain, and the cloud to the right is the debris that is falling/has fallen to the surface.

Thanks so much for your digging, None Of The Above. It is not the orientation I was assuming it to be. I thought that the left was the surface of mars, and the dust cloud was jumping up from the surface on the impact of the debris.

BTW, if you tire of discussing the trite with Obertray and quit, you will be doing as many others of us have done recently. He can truly make a mountain out of a molehill!


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obertray
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« Reply #57 on: March 07, 2008, 07:07:43 AM »

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Down doesn't mean anything in space.

Ober, you gotta understand that that is simply not true. Up and down exists wherever there is a mass close enough to predominate local gravitational effects. If you stopped the orbital momentum  of the MRO satellite directly above that landslide area, it would fall down onto that area*.  An satellite or individual in orbit around, say a planet, doesn't sense the planet's gravity, because he's in continuous free fall around  it, a state prolonged by his orbital velocity. But he IS being effected by the planet's gravity.

So, if you're in a gravity well, looking "down-well" is looking toward the center of proximate mass whether you're standing on it or looking at it from "above". even if you're screaming along in orbit.

"Down" loses physical meaning when you get to DEEP space, but not for MRO.

* (actually only very near it, because of Mars' rotational velocity).

I'm pretty sure that is what I am saying, that up and down are soley a describer of gravity.

But you bring a different qualifer to the discussion (which I appreciate) whan you say that down loses physical meaning.

Physical direction is different from navigational direction.
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NoneoftheAbove
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« Reply #58 on: March 07, 2008, 10:58:13 AM »

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But you bring a different qualifer to the discussion (which I appreciate) whan you say that down loses physical meaning.

Well, I'm not always (or ever) the best at it, but especially talking cosmology, I think precise use of context and lexicon is pretty important. I'm sure that even in deep space, for instance, it's possible to get "down", as in "get down, get funky!".  Grin
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NoneoftheAbove
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« Reply #59 on: March 07, 2008, 11:04:45 AM »

Now, here's something else I think worthy of discussion - NASA Baffled by Unexplained Force Acting on Space Probes

Remember the "anomaly" that was noticed in the velocity of the Pioneer spacecraft? Apparently it's been picked up again:

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"Jet Propulsion Laboratory astronomer John Anderson and his colleagues — who originally helped uncover the Pioneer anomaly — have discovered that four spacecraft each raced either a tiny bit faster or slower than expected when they flew past the Earth en route to other parts of the solar system."

My initial speculative reaction is that it might have to do with "frame-dragging", but I'm not up to the math and the observed effect is so very small. Are there any professional astronomers or cosmologists who haunt these halls?

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"Those who would give up their freedom for security will have none and deserve neither."
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