Strange streak discussion: 2004 Dec 7 APOD

[Guest]

Following up on the discussion of the straightness (or otherwise) of the trail, here's a least-squares fit to it.


(click image for a larger version)

This was created by first rotating the trail so it was approximately horizontal (I used the raw data for this image), then finding the best correlation (i.e. minimum least-squares error) between an intensity template approximating the trail and the trail itself.

The horizontal axis corresponds to pixels lengthwise across the trail, the vertical axis is the pixel number perpendicular to the trail (centred at ~100). The red trace (indexed on the left) is the raw best fit, the blue trace (indexed on the right, and slightly offset for clarity) is a smoothed version of it.

The key features of note are that the general shape of the curve corresponds well to the general shape of the curves in the horizontally-compressed images, and that there appears to be a semi-periodic variation in the centreline position (corresponding to a body wobble, and at a frequency that's in the ballpark for a wing beat - 125 pixels ~= 184Hz). Also note the curve matchs well with the observation that the first half of the trail is quite linear, while the second half appears to show a tightening curvature.

The noise at each end of the trail is because the graph begins just before the trail start and ends after it; obviously before the start and after the ends, there's nothing for the algorithm to lock on to.

[Ed in Oregon]

Take out the event frames and you can't see a thing.

I beg to differ. There's a short, fat "spike" that is a remnant, a shadow, or something.

Where?

There are some waves at an angle to the shore just at the point of land by the pier. There is a matching wave with an opposite angle at the right side of the opening under the pier. I think both are the result of wake waves coming under the pier. They have nothing to do with this.

[Guest]

Following up on the discussion of the straightness (or otherwise) of the trail, here's a least-squares fit to it.

The link to the larger image is broken; it's actually here.

[stop_ams_now]

Hello Kooks.

kooks:
Term used to
describe a regular poster who continually posts messages with no
apparent grounding in reality. Different from a troll, kooks really
believe what they write, to the extent that they believe anything.

[Luis]

This was created by first rotating the trail so it was approximately horizontal (I used the raw data for this image), then finding the best correlation (i.e. minimum least-squares error) between an intensity template approximating the trail and the trail itself.

How did you generated the template... You may just be picking up an artifact produced by the template.

[Ed in Oregon]

Following up on the discussion of the straightness (or otherwise) of the trail, here's a least-squares fit to it.

...The key features of note are that the general shape of the curve corresponds well to the general shape of the curves in the horizontally-compressed images, and that there appears to be a semi-periodic variation in the centreline position (corresponding to a body wobble, and at a frequency that's in the ballpark for a wing beat - 125 pixels ~= 184Hz). Also note the curve matchs well with the observation that the first half of the trail is quite linear, while the second half appears to show a tightening curvature.
...

Amazing! I make it 220 Hz, but why quibble!
And meteors, raindrops, lightning, and all the other theories don't have wing beats.

[Luis]

Moe and Joe were in a plane accident. Their plane crashed into the sea and Moe and Joe swam to a small deserted island. After years had gone by, a pop bottle washes ashore. Moe picks it up and looks at it, holsing it so that Joe could see it. Clearly, it was half the length of Moe's body. Moe yelled: "Hey Joe, we've shrunk".

Or did they? ould the bottle really have been a new style, new fad, three foot bottle, or has Moe and Joe shrunk in size.?? Well, you just can't tell. You have no viable frame of reference.

Moe and Joe looked amazed at the bottle. They really could not tell what had happened. But well, after all they were a couple of smart guys and had nothing better to do in their free time, so they engaged in long and endless discussions and thought experiments that could tell them what really happened. After all, they had no means of replicating the experiment at all...

So they spent all of their free time,which in a dessert island is not much, after all you have to fish, keep your hut in one piece, look after your vegetables, keep the fire going, get wood, clean the water, produce clothes to protect yourself from the sun... an the list is endless. I was saying, they spent long hours at night or in between jobs to discuss the possible origin of the bottle. If they found the true answer or not, they never found, but they came to know each other better and kept their minds healthy.

Ocasionally an seagull or a starfish would stick its nose (actually beak or tentacle) and without understanding the true meaning of the game, would again wonder off.

[scherer]

Explaination 1) A few details must be noticed first. The air was calm as can be seen by the smooth water surface. I'm guessing it was dusk rather than dawn due to the heat generated cumulus clouds in the backgroud. The adjacent lights must have just come on due to the sunset. Lights typically go out during power up. If this light went out and possibly created an arc in the fixture, a port on the top side of the fixture could have created the conditions for the bernuli effect (smoke ring). A dissipating bernuli vortex would leave a faint smoke trail much like this one and would travel long distances in a straight line in calm air.

Explaination 2) The image does on first impression seem to be a meteor trail. Even if the meteor or meteor dust did not come in direct contact with the lamp, the sonic or sub-sonic pressure gradient of a meteor would certainly be enough to "blow" a gas filled light that was still warming up. Halogen lights are particularly sensitive when "ringing" or heating up.

Steve Scherer / Wannabe Rocket Scientist

[Guest]

How did you generated the template... You may just be picking up an artifact produced by the template.

The template assumes a track width 'W' (I used 22 in this case), and everything is normalised to the range 0.0-1.0 (so 127=grey=0.5). So outside the track the value is 0.5, inside the value is computed using the following code (tweaked for readability):-

for (i=-TRKWIDTH/2;i<TRKWIDTH/2;i++) {
x = (double) i;
x = x/TRKWIDTH*2.0; /* Range -1 to + 1 */
x *= 3.14159; /* Scale to 1 cycle */
y =- cos(x)/2+0.5; /* Shift into range 0.0 to 0.5 */
}

The template that produces looks like this:-



Basically that template is slid along the trail, and at every pixel it's shifted from side to side to find the point where the error (squared) is minimised, and the minimum value used as a data point on the final graph.

In practice, the shape doesn't appear that important; my first attempt used a simple V notch and gave virtually identical results. Also, it's robust in that (linear) enhancement of the image doesn't affect the result, so no greyscale stretch was needed (the minimum error is the minimum error however it's scaled, since scaling should not and does not change which point has the smallest error).

[Jack_the_Kook_Killer]

Moe and Joe looked amazed at the bottle. They really could not tell what had happened. But well, after all they were a couple of smart guys and had nothing better to do in their free time, so they engaged in long and endless discussions and thought experiments that could tell them what really happened. After all, they had no means of replicating the experiment at all...

So they spent all of their free time,which in a dessert island is not much, after all you have to fish, keep your hut in one piece, look after your vegetables, keep the fire going, get wood, clean the water, produce clothes to protect yourself from the sun... an the list is endless. I was saying, they spent long hours at night or in between jobs to discuss the possible origin of the bottle. If they found the true answer or not, they never found, but they came to know each other better and kept their minds healthy.

Ocasionally an seagull or a starfish would stick its nose (actually beak or tentacle) and without understanding the true meaning of the game, would again wonder off.

Eureka it was a shooting starfish.

But wait, shouldn't the refractive index of the starfish be similar to water ~1.5
not air 1?
If so then the least squares fit to the cornball factor is approximately equal
to merry christmas to the power of eggnog.
The approximate airmass through which the shooting starfish travels could
never cause a contrail with 220Hz wingflap frequency.
Can starfish flap anyway?

A corollary to Arthur Conan Doyle's theory of elimination:
If all other theorys are rediculous then the most obvious one is correct.

[Captain Max Planck]

Have you considered the Eddington luminosity?

Max

PS. Is Kook baiting a sport?

[ftruck]

The mist or smoke seems to be coming from the ground behind the tree and drifting up around the light forming a halo of sorts.
The photo was taken in Darwin, Nth Australia. The area has several Air Force and army base's for both Australia and the US.
The line could be exhaust from a fighter jet or rocket test.
When the jet takes off it would require more fuel and the pilot would back the engines of after he's airborn thus more smoke close to the take off point on the other side of the river somewhere and less as the jet reached altitude.
Just good luck that the photographer was on the right spot to line up the jet exhaust (probably hapens everyday) the light on the jetty and the smoke from the BBQ under the tree.

[mikedoug]

"Nice analysis, but I think you're missing something."

Could it be his brain?

I lost that one a long time ago!

When did you lose yours?

While reading this drivel.

[Guest]

Meaning of AMATEUR

4. [adj] lacking professional skill or expertise; "a very amateurish job";
"inexpert but conscientious efforts"; "an unskilled painting"

Synonyms: amateurish, inexpert, nonprofessional, recreational, unpaid,
unprofessional, unskilled

Actually we are professionals (but we're goofing off).

That wouldn't be the oldest profession that you're practicing would it?

[no_more_ams]

Meaning of AMATEUR

4. [adj] lacking professional skill or expertise; "a very amateurish job";
"inexpert but conscientious efforts"; "an unskilled painting"

Synonyms: amateurish, inexpert, nonprofessional, recreational, unpaid,
unprofessional, unskilled

And what do you think a board like this is? A scientific meeting?

Now that you are so intersted in the meaning of words, what about this one moron, I mean its meaning, according to the Oxford dictionary.

• noun informal a stupid person.


— DERIVATIVES moronic adjective.

— ORIGIN from Greek moros ‘foolish’.

Thanks for clarifying the level of the work done here, moronic.

[Snodney Belcher]

I don't think it was Comet. Maybe donner or blitzen. But I can't recall, the most famous reigndeer of all?

[Tommy Hollingshead]

I see these things everyday. But I'm not going to tell you what it is.

[Not Luis]

In all seriousness has anyone actually ruled out cosmic rays?

This does look exactly like the charge trails on CCDs. Particularly with
the charge ending in a few pixels and the fact that the cameras alignment is
with the vertical.
The probability is low but certainly non-zero.

[Luis]

"Nice analysis, but I think you're missing something."

Could it be his brain?

I lost that one a long time ago!

When did you lose yours?

While reading this drivel.

So we are all equally brainless. Although you seem to be quite bitter about life. You have all my sympathy. And please come back with any agression or clever remark you wish, it will just reinforce the impression of you that we will keep for posterity.

We are only memory and the remembrance that others keep of us. And as a bitter sowl I will remember you. You have my pitty.

[Not Not Luis]

In all seriousness has anyone actually ruled out cosmic rays?

This does look exactly like the charge trails on CCDs. Particularly with
the charge ending in a few pixels and the fact that the cameras alignment is
with the vertical.
The probability is low but certainly non-zero.

It would spoil all the fun of the image processing!

Now talking seriously, I may be naive here, but if ti was a cosmic ray, wouldn't we expect it to come perpendicular to the horizon? Or is this terribly stupid to ask?

[mikedoug]

Thanks, I always liked "bitter sowl" far better than the average lager.

[Luis]

I see... if I understand you correctly what you are trying to do is to measure the "strightness" of the pattern. By doing the LSF to that template you want to measure variations from it.

Now wouldn't this analysis be insensitive to what side of the streak is changing shape? I mean it would equally pick up a symmetric narrowing of the streak and an asymmetric narrowing of it, or even a change of idrection without a noarrowing...

If my interpretation is correct, could you come up with a template that picks up what side of the streak changed shape and in what direction. We would like to know if the streak is ondulating, but its width is constant, or if its width is actually changing periodically.

Also have you run an FFT of your signal? Is there a spike somwhere, or is it the brain picking up a pattern that is not really there?

Cheers

[Not Not Not Luis]

In all seriousness has anyone actually ruled out cosmic rays?

This does look exactly like the charge trails on CCDs. Particularly with
the charge ending in a few pixels and the fact that the cameras alignment is
with the vertical.
The probability is low but certainly non-zero.

It would spoil all the fun of the image processing!

Now talking seriously, I may be naive here, but if ti was a cosmic ray, wouldn't we expect it to come perpendicular to the horizon? Or is this terribly stupid to ask?

Cosmic rays don't "all" have to come from zenith.
What is the latitude of the location?

[Cloudbait]

In all seriousness has anyone actually ruled out cosmic rays?

This does look exactly like the charge trails on CCDs. Particularly with
the charge ending in a few pixels and the fact that the cameras alignment is
with the vertical.
The probability is low but certainly non-zero.

I've made tens of thousands of CCD images over the years, and most have cosmic ray hits (I work at a high altitude). I've never seen a cosmic ray hit that looked like anything in this image. A direct cosmic ray hit produces a saturated pixel (or a small cluster of them). Sometimes, a cosmic ray produces a shower of high energy particles that can show up as tracks of hot pixels on an image. But there is nothing a cosmic ray (or its products) could do to produce the shadow track, and the "explosion" isn't even saturated. A cosmic ray event can be discounted.

[Not Not Not Not Luis]

Cosmic rays don't "all" have to come from zenith.
What is the latitude of the location?

Looking for the latitude I found this link, it summarises most of what has been posted here

http://www.cloudbait.com/science/darwin.html

And I found this info there

The image was made at 12° 28' south, 130° 50.5' east. The camera is facing a little east of south, and is about 500 meters from the wharf. At the time these images were made, the azimuth of the Sun was 249° (WSW) and the altitude (with refraction) was -0.3°, or just below the ideal horizon. However, the Sun's azimuth placed it behind land, so the actual horizon was higher.