Wikipedia:Reference desk/Archives/Science/2019 July 22

= July 22 =

Luna 15 flyby video: real of hoax?
I just watched a YouTube video on Luna 15 and it included a brief clip that was claimed to be a flyby of the Luna 15 caught on Apollo 11 film or video. It is at 5:33 Race for the Rocks - Apollo 11 vs Luna 15 on the Moon. It is also found here: Luna 15 over Eagle Apollo 11. Several things struck me as odd and made me suspect that this a fake video. I first searched snopes but found nothing. A further search turned up little except this stack exchange article, which in turn mentions that the clip was included in a 2005 BBC documentary "Space Race". Can anyone here find more information to confirm or debunk the authenticity of this clip? Perhaps the angle and flag position can be matched to photography of a later mission. -- Tom N  talk/contrib 01:32, 22 July 2019 (UTC)
 * The camera angle is wrong, showing the equipment bay on the backside of the lander from the quadrant III direction.
 * The flag is in the wrong place, also in quadrant III.
 * I didn't think the camera exposure level was set to be sensitive enough to be able to detect such a flyby.
 * Actually, BBC's "Space Race" was not a documentary, it was a docudrama -- if the clip was from there, then its fake. —107.15.157.44 (talk) 02:21, 22 July 2019 (UTC)
 * docudramas usually make extensive use of real footage, when available (besides, those come for free when public domain). -- if the clip was from there, then its fake. — is just wrong. The 6:07 dust figuring the crash of Luna is obviously not the real thing (nobody was there to film it) and the clip doesn't claim it is (it just suggests so). OTOH, I see no reason to doubt the explicit claim that the clip at 5:33 shows Luna flyby Apollo Gem fr (talk) 07:09, 22 July 2019 (UTC)
 * This Stackexchange thread discusses the video and whether it would have been possible. People seem to think not. --69.159.11.113 (talk) 07:59, 22 July 2019 (UTC)
 * People on this thread only point out that the astronauts would need to be specially on the watchout to have any chance to spot Luna, which is true. However, we are talking about Luna making a 2 seconds impromptu cameo on a long video from a fixed camera. This had significant chance to happen. Gem fr (talk) 08:24, 22 July 2019 (UTC)
 * What fixed camera taking long videos would this have been? --69.159.11.113 (talk) 21:47, 22 July 2019 (UTC)
 * The one (white upright object) on the foreground on this image, if I understand correctly the caption "stereo close-up camera stands in the middle" (from ) Gem fr (talk) 09:59, 23 July 2019 (UTC)
 * If the footage was captured by American Apollo equipment, it would be documented in the extensive archives, which are available to the public at the NASA Apollo Lunar Surface Journal. From the flight journal, I found Apollo 11, Flight Journal, Day 3, which contains archival audio of a NASA press conference on the topic of Luna 15.  By the third week of July, 1969, the orbital parameters of Luna 15 were known at NASA.  Conceivably, a camera could have been aimed at a place and time when Luna 15 was predicted to overfly.  After a brief search, I can't find documentary evidence of any plan to capture such footage.
 * If the footage were captured, it should be in the video index or the photography index.
 * With very little deviation, every single piece of footage and photography captured on the journey during the Apollo 11 mission is archived, including its camera, its storage medium, and the reason why that imagery was captured; and all of this data is available to the public.
 * Conversely, if the footage in question was some type of illustrative, simulated, or "news-reel" animation that was not actually captured from the moon, it's going to be a lot harder to track down its origin. From the footage in question, we can rule out most of the cameras - we know exactly where each video camera was at all times during Apollo 11 (because the cameras were placed and operated according to a schedule).
 * Nimur (talk) 13:04, 22 July 2019 (UTC)
 * Thank you all for your insights. Given that a docudrama may contains mix of real an "dramatized" footage, and the fact that the clip does not match the angle of the lone Apollo 11 TV camera, I would have to conclude that the clip was a dramatization. I've also reviewed photography from the other Apollo landing sites and none match the image in the video clip. It appears that the clip is entirely a studio production - both foreground and flyby. -- Tom N  talk/contrib 23:40, 22 July 2019 (UTC)


 * Sounds like something could weigh in on. ←Baseball Bugs What's up, Doc? carrots→ 01:08, 23 July 2019 (UTC)


 * The first video is accurate in what it says, but I think the video of the Luna 15 flyover is fake. They did leave the video camera on after they went back in, and I'll have to look that up to compare.  But it looks fake to me, and it pans up and zooms in. The camera didn't have zoom, but those could be post production.  Bubba73 You talkin' to me? 02:08, 23 July 2019 (UTC)


 * After the Apollo 11 moonwalk, the TV camera was left like this, so the video of Luna 15 passing over is fake. Bubba73 You talkin' to me? 02:17, 23 July 2019 (UTC)
 * The pan and zoom is obviously post production, you can seen the grain (pixel) growing; they could just as well have add a flashing arrow to highlight
 * I understand that the flyby occurred while the men where still on the moon, so the position of the camera after the departure is just irrelevant
 * Gem fr (talk) 09:18, 23 July 2019 (UTC)
 * No, it is not irrelevant. The way they left it (shown in the screenshot I uploaded) doesn't come close to matching what is in the video.  Neil put the camera on a tripod and moved it out to that location.  It wasn't moved after that.  The video depicts the period of time after the camera was placed there and before the ascent state took off.  The screenshot is from that period after the astronauts were back inside the LM and before the ascent stage took off.  For instance, the screenshot of the actual video doesn't even show the top of the Lunar Module, whereas the video shows area above the LM.  Bubba73 You talkin' to me? 15:40, 23 July 2019 (UTC)
 * show lots of videos, with different angle. For instance, a11.v1105816 Vs a11.v1104333 . So It wasn't moved after that may be true as far as position is concerned, but is obviously not true when we consider the angle. Doesn't mean the footage is real. Just mean your argument to discard it doesn't stand. Also, not sure all the film have been digitized. Gem fr (talk) 17:53, 23 July 2019 (UTC)
 * Not all of the videos are from the video (TV) camera. There were 16mm movie film cameras in the CM and LM.  The TV camera was first attached to the side of the LM.  After being on the surface for a while, Armstrong unmounted it, did a pan, moved as far away from the LM as the cable would reach, set it up on a tripod, and left it there. If the video in question were authentic, it would have to be from the TV camera after Armstrong moved it to the tripod and before the ascent stage left the Moon.  It would have to match the still I uploaded - it does not, therefore it is fake.  Bubba73 You talkin' to me? 22:50, 27 July 2019 (UTC)
 * From the page you linked to: "Journal Text: 110:02:53 ... Television clip. Neil has just completed his television panorama and has fixed the camera in its final orientation southeast towards the lunar module." Bubba73 You talkin' to me? 02:56, 28 July 2019 (UTC)
 * Look at the complete moonwalk TV video from 42:10 to the end (which is after the astronauts went back inside). It doesn't match the fake video.  Bubba73 You talkin' to me? 03:26, 28 July 2019 (UTC)
 * Look at 1:32:37 and later at 2:59:00 : obviously what was visible on TV did not match what was filmed by the camera. Some cuts were required. This is because TV standard did not match film standard. So your proof do not stand. However:
 * There are two major discrepancy: in the shadows (light coming from the left in real footage, from behind in the suspect video), and orientation of the flag (to the left in the former, to the right in the later). Besides, quite a number of simulation/artist rendering were produced; normally duly labelled as such, but who knows... So I tend to agree this is a reconstruction, not a real footage. Gem fr (talk) 16:54, 28 July 2019 (UTC)
 * This restored video was assembled from different sources. Right before 2:59:00 it says that the end bit was shot from a hand-held 8mm movie camera pointed at the TV screen, which is why it looks a little different from the earlier.  You can see the shake in the image due to the handheld camera filming the TV screen.  (The film movie camera was mounted in the LM window, so obviously it is going to be a different angle.)  I don't know what you mean by the standards not matching, unless you mean that a film made from the TV screen might be a little tighter shot.  But apart from that little bit from the end, probably all of it came from videotape.  Bubba73 You talkin' to me? 19:00, 28 July 2019 (UTC)


 * Just to discuss the binary choice in your title "real or hoax", if it's a re-creation, then that is neither. A hoax is an attempt to deceive us into thinking an event occurred which did not, while a re-creation is an attempt to show an event which did really happen. That is, although the footage is not real, the event was. SinisterLefty (talk) 03:45, 23 July 2019 (UTC)


 * But if a scene staged for a movie is clipped from the movie and (deliberately) presented as being film of what the movie is representing, that is a hoax. And I think that's what the original question claimed. --69.159.11.113 (talk) 07:56, 23 July 2019 (UTC)


 * I still wouldn't call the footage a hoax, but it is being misrepresented. SinisterLefty (talk) 12:16, 29 July 2019 (UTC)
 * It might be more charitable to call it a "re-creation". Though if they fail to say somewhere that it's a re-creation, then it's fair to call it a hoax or a fake. ←Baseball Bugs What's up, Doc? carrots→ 12:22, 29 July 2019 (UTC)

Why is a tin sealed metal box not as effective as a "Faraday bag"
Due to the number of "relay attacks" on cars with keyless entry and start I started keeping my keys in a sealed tin. I posted this on a forum and someone said "tin cans don't work", which surprised me. I checked it and indeed the car opens when the can is held very close. I also have an RFID blocking pouch, which I stopped using as it is too small to get all my keys in. I tried with the car key in this and it blocked the signal, even when touching the car.

I would have thought that a solid tin would be better. It has a lid that fits tightly with overlap. Why is the RFID blocking pouch better at blocking the key signal than a solid metal tin? -- Q Chris (talk) 14:16, 22 July 2019 (UTC)


 * Just to clarify, are you actually asking about a metal can, which these days would be made of steel, not tin ? SinisterLefty (talk) 14:20, 22 July 2019 (UTC)
 * Yes - I am pretty sure it is coated steel. I could test with a magnet when I get home -- Q Chris (talk) 14:22, 22 July 2019 (UTC)


 * Confirmed, the tin is magnetic so must be coated steel -- Q Chris (talk) 17:21, 22 July 2019 (UTC)


 * Faraday cage is the relevant article. 107.15.157.44 (talk) 18:04, 22 July 2019 (UTC)
 * That article appears to imply the opposite; that thicker materials are better and that solid sheets rather than mesh work over a wider frequency range. -- Q Chris (talk) 21:07, 22 July 2019 (UTC)
 * But also that the material composition has an enormous effect, so tin-coated steel can vs. copper mesh is not an apples-to-apples comparison. Someguy1221 (talk) 23:27, 22 July 2019 (UTC)
 * You should make sure that the lid has electrical contact with the tin all round. The tin and lid internals are probably coated in plastic, and so will not conduct between them. You should be able to burn or scrape that off. Graeme Bartlett (talk) 01:35, 23 July 2019 (UTC)
 * This. If it's a food container, which it looks like it is, the inside has a plastic coating. Any modern food container containing metal (examples include metallised film and drink cans) has a plastic lining to prevent metal from touching the food. This prevents metal ions from transferring to the food, which causes off-flavors and promotes oxidation. (Chelating agents such as EDTA are also widely used as preservatives, for the same reason. The agents sequester metal ions that happen to get into the food.) Note that burning plastic produces toxic chemicals; I wouldn't advise it. --47.146.63.87 (talk) 05:10, 23 July 2019 (UTC)
 * I will give that a try later, it should be easy to remove the coating around where the lid joins. I am still surprised that two overlapping plates don't block the signal, even if they are not connected electrically. Another possibility is that it has to do with the number of layers, as someone commented on the original post that metal containers like this do work if you line them with foil -- Q Chris (talk)
 * Note that some tins are actually made from cardboard - eg Pringles container, so they may not conduct that well. At the frequencies used (≈300MHz) the skin depth in metallic conductors is less than a few microns, so almost certainly the metal is thicker than that, even if only a foil. 10 or 20 skin depths should attenuate the signal to undetectable levels. Graeme Bartlett (talk) 00:34, 24 July 2019 (UTC)

Faraday cages stop electric fields from charges external to the cage from getting into the cage, but net charges inside the cage will have a field exist outside the cage. Strictly speaking that field outside is due to charges on the outer surface of the cage (whose presence there is due to the internal charges) but the presence of a net charge inside does manifest a field outside the cage. What you would want is a cage to put your car in.... BSVulturis (talk) 00:56, 27 July 2019 (UTC)