once more unto the breach...

[levine54]

I posted a question and recieved one answer. This did not answer the question. Perhaps one of our masters might consider a review.
If a pristine piece of aerogel is simply x-rayed, theoretically, it should show nothing. If a known piece of aerogel containing a particle of space debris, as used in the tutorial, is x-rayed it should show as a black dot on the x-ray. Subject the stardust unit to the x-ray and the myried particles contained therein should show up. This should, theoretically, identify the aeras that should be reviewed as opposed to scanning every millimeter hoping to find a trail.
If my reasoning is wrong, I would appreciate an explanation of where it is wrong.
Thank you, Harvey S. Levine

[fjgiie]

http://stardustathome.ssl.berkeley.edu/ ... ight=#9139

Hi levine54,

While you await your answer, may I give you my own personal thoughts regarding your question. From the above post we discover that Aerogel is not that pristine. From the manufacturer it contains impurities which show up on x-ray as points. We see some points within the Aerogel ourselves that are below the surface. (The stardust we are looking for has been said to be too small to see, we can only see the tracks.) From other reading I have learned that Aerogel contains stray bits of several inpurities.

I do not know if the dust tracks we are looking for would show up on X-ray, but they should show up in the focus movies we are looking at. Could not 15,000 people looking for these tracks find them quicker than one or several X-ray machines? The pictures would still have to be magnified large enough to see. How long would it take to make 750,000 X-rays? Who would have time to read them?

I told you, just my thoughts,

fjgiie
ps: Maybe we can get an answer to your question this time.
f

[Nikita]

Continuing on Fjgiie's thoughts, once they have the X-ray images and if they can get past the surface junk, they would still have to visually go through the aerogel. Most likely, they would still need us to look through it all and would have to use the virtual microscope anyway.

And by the way, the reason I gave my own opinion is because I have thought along these lines before too! I even thought of doing comparison scans before and after to see what had changed, but there are too many influences on the aerogel during the mission to be able to say that a difference would be stardust.

I look forward to hearing the answer too!

[Wolter]

Ok, suppose there is an X-ray machine with a resolution small enough to see the particals. Then , let's x-ray the collector. What do you end up with?
X-ray pictures of the collector. How do you determine which picture has an partical in it? By looking at it.

So what's the advantage to the current method? I don't see one.

How to look is not the problem, how to recognise is.

[Denise]

I'm still up to my ears translating lots of stuff about petroleum research in the Sahara - which is covering work done between 1953 and last year (more or less the span of my life, as it happens). Giving me a glimpse at the progress over 50+ years in how to get an idea of what's going on deep beneath the surface of the world without having to physically touch it (in the early stages at least).
With my head full of all that, and seeing you talking about x-rays, sonic reflection has crossed my mind. Probably rubbish, and if not it probably throws up the same kind of problems.
But just starting to think about all that crowds my mind - like, just what are the "tracks" - do they reveal themselves because of some "ordered" pattern of turbulence? For example - are they empty? - less dense? - areas of higher density surrounding voids or less dense areas? In which case, couldn't horizontal sound bouncing pick them up?
I of course have no real idea what I'm talking about, but I did almost impress myself for a moment there...
[emoticon whereby denise exits with a toss of the head and a casual wave of the hand, laughing politely at the offer of next year's nobel prize]

[ZackG]

X-raying at the resolution necessary to find particles would indeed create gajillions of images just like optical scanning did. (That's a technical term.) We would still be left with the same problem of how to sift the chaff from the grain as brought up earlier in this thread. In addition, we'd have the added headache of dealing with the x-ray apparatus.

There is another problem too. X-rays are a very energetic form of light and can *easily* trigger chemical reactions. Optical light is much "softer" on the samples because the energy of an optical photon (particle of light) is roughly 10,000 times less than an x-ray photon. Since one of the primary purposes of the mission is to examine the samples unaltered, this probably doesn't require too much explanation. Neverthless, many of the samples probably contain material that won't be heavily altered by x-rays. In these cases, we can and will use x-rays. Of course, by then we have already found the particle!

The reason we don't use ultrasound is because the ultrasound waves are too big to see a particle which is only a couple microns in size. By the time you increase the frequency of the ultrasound so that one wavelength is only a couple microns in size, it bounces around too much within the aerogel to provide a decent image. However, ultrasound is pretty useful for *cutting* aerogel, and we have used ultrasound tools to cut aerogel.

[Denise]

The reason we don't use ultrasound is because the ultrasound waves are too big to see a particle which is only a couple microns in size.

Thanks for explaining, I do appreciate it. But (if you'll allow me to be so presumptious) you seem to be talking about locating a particle. I was thinking about locating the track, hence my question about densities. Surely there's a way of ultra-sound "cutting" horizontally, "slice" by "slice", and spotting a pattern (a non-randomness in density changes in the aerogel) ?
Sorry - you get ingenuous questions like mine when you involve "the public". Doesn't mean I don't enjoy looking, just that I think about it sometimes, specially since there is apparently nothing that has turned up yet.
Denise

[ZackG]

I like ingenuous questions. It means you're cutting to the chase. The best are ingenious + ingenuous questions.

Regarding 3D imaging of the tiles using ultrasound, I think the problem isn't whether or not it is possible, but rather that it isn't the optimum solution. The primary issue has to do with making a "solid" connection between the ultrasound machine and the aerogel and how the sound waves bounce around within the aerogel. For comparison you might be thinking of medical ultrasound, such as that used to image a fetus. However, the two aren't the same. Because aerogel is so delicate and fragile, it would be very difficult to get a high quality ultrasound connection without damaging the tiles. In addition, ultrasound characteristics can be highly variable from one material to another, so unless there is a severe economic incentive to devlop the ultrasound technology for a specific application, then the money probably won't be spent. So, for ultrasound to work, you need economics behind you AND you need it to be technically the best way to do the job. In the medical field, obviously, there is a demand for devloping the technology because abdomens are opaque (unlike aerogel), and the economic value for imaging is high. They also use ultrasound imaging in some other industrial applications where circumstances are particularly advantageous. (Testing weld joints comes to mind. Maybe some of our other dusters work in these areas and can pipe in.)

Given the fact that the aerogel tiles are extremely fragile, light, and they'll tend to reflect the sound waves in patterns differently than other ultrasound applications, the upshot is that it is just easier to use optics.

That said, maybe we have an ultrasound engineer on the board who would like to go online, buy some aerogel and develop an ultrasound imager. If it worked better than what we're doing, then I'm sure we'd use it and probably hold a feast in your and his/her honor!

[levine54]

I wish to express my thanks to all who participated in my query.
I have learned a lot. There are a lot of great minds out there in Dusterville. Once again, thank you

[Denise]

... awful pun there, ZackG...
Tee-hee

[Jwb52z]

It would be very difficult to create an ultrasound imaging machine for aerogel because it's 1,000 times less dense than glass. See, the way they work is that they have to use a specific frequency and intensity depending upon through what they are trying to making an image of at the time. That's not so much of a problem in the human body except in the case of too many in a row can cause problems in a pregnancy, which is why they don't do them ALOT and why many people griped about Tom and Katie buying a sonogram machine. Anyway, the frequency and intensity of the sound waves matter in inanimate materials because everything in the universe, as far as we know, has a specific point at which it can be vibrated apart or torn apart, for lack of a better way to say it. With such a light material, I'm not quite sure that there is a wave length of sound waves that could do the job of even making an image without disturbing the aerogel, seeing as how the machine involves pressure on the surface of the object/person as well.

[Denise]

Thank you for explaining, both of you. (And my apologies to Zack for my flippant comment ( re "pipe in" for welders). I'd meant to follow it up.
It's frustrating though, specially for someone like me who (by profession) has a little knowledge here and there and so thinks it should be easy.
My reference was not even to scanning abdomens, but layers of the planet. So a long way off.
But there's nothing wrong with keeping looking with our eyes, and rather nice too.
Denise