Talk:Rope trick effect

Second Law of Thermodynamics?

How it is possible that these "spikes" are apparently brighter (per square unit) than the fireball itself? Is this simply due to the inhomogenic sensitivity curve of the photographic film (and the fireball in truth brighter than the the exploding ropes) or is the temperature of the ropes really higher than that of the fireball surface? If both fireball and "rope gas" are comparable to a blackbody the intensity should increase with temperature at all wavelengths and thus the intensity within the fraction of light for which the film is sensitive should also increase (and thus the fireball be brighter). Normally the apparent inversion of this relation (i.e. receiving material hotter then the emitting material) would violate the second law of thermodynamics and therefore should be impossible.--SiriusB 15:01, 15 May 2005 (UTC)

• I assume it's just the film. Deltabeignet 19:04, 27 May 2005 (UTC)
  • But this also could not explain the phenomenon completely. Even if the film is sensitive only to a small fraction of the spectrum (what should most probably be the case) the intensity should still rise with temperature. You won't observe that a glowing object becomes darker, neither globally nor at any specific wavelength. The only reason I could think of is that either the fireball or the exploding ropes has a spectrum far from that of a black body.--SiriusB 21:02, 27 May 2005 (UTC)
    • Perhaps it is merely a matter of timing. The photo shows the fireball just after it has turned into a hydrodynamic shock front. Prior to which, it was a much hotter radiatively driven shock (UV/X-rays) and this, I suspect, is the radiation which was mostly responsible for heating the ropes and blowing the bright plasma off of them. Maybe the rope plasma simply hasn't had the time yet to cool to the temperature of the fireball due to this delay effect. Anyway IANAP, email LANL or LLNL and see if they'll give you some information on the effect.--Deglr6328 22:07, 27 May 2005 (UTC)
• Well, maybe the ropes are just burning. If, for example you aproach a match to the flame of a candle, when the match fires, it'll get far hotter than the candle itself. --Pinzo 21:15, 13 August 2005 (UTC)

• • I think that would be impossible though. We're talking burning rope and a nuclear bomb, a temperatrure difference of millions of degrees. Also it doesn't have time to "burn" in the conventional sense. Microseconds after the image was taken the whole lot was total obliterated. The ropes are vaporized into a plasma in this image and I would think that any light given off by conventional combusion with air is minmal at this stage. --Deglr6328 23:35, 13 August 2005 (UTC)

• • • Yeah, maybe you're right... What about difference in density? I mean, the fireball is expanding at great velocity, thus it'll get cooler quickly, but the ropes, turned into glowing plasma, will expand slower, and so they can keep a high temperature for a longer time. Just guessing. --Pinzo 01:38, 14 August 2005 (UTC)

• In the image the spikes are not apparently brighter: they are brighter. However, it does not follow that the spikes are hotter than the fireball.

The brightness of a photographic image tends to increase with:

1. intensity of the light incident on the optics though this itself is highly dependent upon
2. transmission of light through the optics, hence intensity of light incident upon the film;
3. duration of exposure;
4. sensitivity of the film to the frequency of the incident radiation.

If the air is acting as a 20 kK blackbody then its λ_max is readily blocked by ordinary glass optics meaning a substantial portion of its energy simply does not reach the film. (Yes, I do know that higher T leads to increased intensity at all wavelengths.) If the mooring ropes are organic then they could easily be incandescing visibly at T < 1400 K (as does a candle flame). Potentially a lower temperature but more visible light being emitted and hence detected.

As temperature is a measure of average kinetic energy, a volume of cooler, more dense material can contain more thermal energy than the same volume of a hotter, less dense material. Presumably density_rope > density_air ; even if cooler a denser rope could be radiating more total energy per unit area of film leading to a brighter image. Waerloeg 10:08, 11 September 2006 (UTC)

Plagurism?

Isn't this article almost directly copied from the "Rapatronic "Rope tricks"" site linked to at the bottom (http://simplethinking.com/home/rapatronic_3.shtml)? Which way did the information propegate? Is this legit?

What is "plagurism"? anyway this information appears on MANY different sites using very simillar terminology. There are ony so many ways to describe the thing.--Deglr6328 06:50, 29 March 2006 (UTC)

I think you know what plagiarism is, but for posterity's sake...it is spelled plagiarism and refers to verbatim copying of text from an outside source, which was clearly done here (or there..or the same author wrote both pieces). It is a copyright violation, and Wikipedia policy clearly forbids it. If anyone's just copied/pasted from that site, the copied passages should be paraphrased or rewritten (they could be improved quite a bit anyway).

well go at it then.--Deglr6328 04:34, 30 March 2006 (UTC)

If the typer of this article copied the webpage plagiarism will not be the problem; the problem will be copyright infringement and lack of citation. Copyright infringement is not licit.

If the author of the webpage copied Wikipedia then there needs to be notice on that webpage that the information is covered by the GNU Free Documentaion Licence (GFDL), that that webpage is also covered by the GFDL and credit to the Wikipedia authors needs to be given.

That there is more info at the external site than is in this article and that it is pointless to link to a site made after and taken from an article would seem to indicate that the propagation is from that site to this article and not vice versa. Waerloeg 09:07, 16 August 2006 (UTC)

It bothered me too so I cited Sublette at the end of the paragraph. I think this para should be rewritten so it's less of a cut & paste job from his work. -- Brianhe 16:09, 27 March 2007 (UTC)

Colored version of image?

Here is a coloured version of the image. I'm not sure if its worth swapping it with the present image.--Trounce 14:21, 28 July 2006 (UTC)

colored version

I would have to say that no it is not woth it. does it look neat? sure but what new information does adding red to the image convey to the reader? none I think and it even may convey an incorrect impression that this was the actual color of the thing which would not be good. --Deglr6328 00:02, 29 July 2006 (UTC)

Confused...

Exactly what ropes are burning? and what is a "shot cab"?

Mooring ropes from the shot cab to the ground, like those you can see on radio masts and other tall towers. The shot cab is the housing at the top of the tower that contains the explosive device. Waerloeg 21:20, 26 August 2006 (UTC)

It would be nice for experts to change the article to say so. I've done it using the information above. Bazza 12:24, 27 March 2007 (UTC)

"rope tricks" description incorrect, mixed up with other experiments

The text says that "The "rope tricks" which protrude from the bottom of the fireball are caused by the heating, rapid vaporization and then expansion of mooring cables.... induced by exposure to high-intensity visible light radiation, which causes the effect."

Since light radiation travels at essentially infinite velocity relative to the fireball shockwave, one would expect vaporization of the mooring cables along their entire length, though perhaps with slightly decreasing vigour, as you go radially outward.

This is clearly not the case -- the "rope tricks" show a definite start, with no sign at all of any heating farther out, radially (besides being brighter than the fireball, as noted in a previous discussion).

Moreover, the form of the "rope tricks" is conical, radially inward from the start, which is characteristic of a shock rarefaction wave, following behind the lead shock in the wire itself (shocks travel faster in dense media like the steel wires, which is why the spikes stick out ahead of the fireball).

The cited description of tests by Malik contradict this, but this was taken out of a text describing different experiments, where the wires were not mooring cables for the bomb tower itself, but rather cables going parallel to the tower, at some distance away.

In such an arrangement the wires get broadsided by the light flux, and of course vaporize along their entire length at once, as expected.

By contrast, wires going radially away from the bomb will not see much light, because the light is also going out radially (ie. parallel to the wires, not perpendicular).

-- Jaro 02:11, 30 March 2007 (UTC)

Your thoughts are intriguing and seem plausible. Can you cite some references?--Deglr6328 12:33, 31 March 2007 (UTC)

Kelvin vs Kelvins

Instead of having an edit war let's talk about this here. The WP style guide is clear that the singular K is to be used for Kelvin. Is there some good reason not to follow the style guide? Brianhe 23:56, 13 September 2007 (UTC)

Credit

I think I found the original document that a lot of the text in this article was cut and pasted from. I credited it at the bottom of the article. Take a look and see what you think, and monkey with the refs as necessary (I suck at that). --Milkbreath (talk) 00:15, 23 November 2007 (UTC)

Additional info for Pic

It might be worth mentioning in the article the 5 vertical white lines visible in the lower right corner of the picture are not an example of the rope trick effect. Smoke devices were ignited prior to the detonation of the nuclear device to better facilitate the measuring and charting the expansion and effect of the primary nuclear device.--Legomancer (talk) 03:03, 17 July 2008 (UTC)

Video problem

Not really part of the discussion, but has anyone else had trouble with the video clip? I clicked it and it flickered and went dead. A few times. When I tried the 'still shot' option, it froze my browser (Firefox 2) leaving me only able to shut windows. Closing and restarting Firefox didn't work until I closed it in Task Manager. By the way, I prefer the coloured image for the still - so long as it is clearly labelled as additionally coloured. It looks clearer to me. I'm slightly (you never know why the military do some things) puzzled as to why they would use rope rather than metal cable for anchorage. Did they not worry that it might fall over post-bang, or would metal cable vapourise just the same? Peridon (talk) 16:43, 15 September 2008 (UTC)

The guy wires, and, indeed, the entire shot tower, were normally vaporized completely by the weapon fireball in a matter of milliseconds, so the construction of the guy wires didn't matter very much post-firing. Even if a bomb didn't completely destroy its shot tower (as happened in only two US cases, the Buster Able fizzle and the Upshot-Knothole Ruth design failure), the tower would be heavily damaged by the high explosive trigger used (as seen in this photo of the Ruth shot tower) and therefore wouldn't be reused, so there was no reason to worry about their long-term stability; all they needed to be able to do was stay standing for the week or so that it would take to install the diagnostic equipment and the weapon itself in the shot cab before the test. Indeed, some of the shot towers (including the one used in the famous Trinity shot) were of wooden construction! Rdfox 76 (talk) 22:57, 15 September 2008 (UTC)

"100 times the intensity of sunlight" seems like a gross underestimation

Can someone verify this number? It seems extremely low. Working with solar furnaces, only a 100X concentration would take quite a while to MELT metal, let alone instantly vaporize it. With the inverse square law, plus the extremely brief duration of the thermal pulse, I would expect concentrations in terms of thousands or even millions of solar units. From anecdotal evidence stating that at 10 miles the heat was roughly equivalent to full sunlight, and using a nominal distance of 100 feet for the limit of the "rope effect" (more or less) a rough calculation would give a value on the order of about 280000 solar units.

Going back to the original quoted source, the original said "intensity over 100 times greater than the sun", note "sun" not "sunlight". From the original author's reference to "the surface of the sun", just preceding this quote, implies that "sun" refers to the sun's surface. The word "sunlight" is universally taken to be the intensity at the Earth's surface (not the surface of the sun) when used casually as a unit of intensity. If anyone disagrees with this, please feel free to comment. I have changed the text to read "surface of the Sun" in the meantime. —Preceding unsigned comment added by Pmarshal (talk • contribs) 06:55, 5 April 2010 (UTC)

Rope Trick experiments

One of the outcomes never mentioned anywhere is that this gave them valuable information that eventually helped them configure the shape and placement of the "Secondary" used in thermonuclear (TN) weapons. — Preceding unsigned comment added by Atomicjohn (talk • contribs) 22:38, 6 August 2011 (UTC)

One of the outcomes never mentioned anywhere is that this gave them valuable information that eventually helped them configure the shape and placement of the "Secondary" used in thermonuclear (TN) weapons.Atomicjohn (talk) 22:39, 6 August 2011 (UTC)