Wikipedia:Reference desk/Archives/Science/2020 October 24

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October 24

Identify shark animal species from zoo photo, from between four options

I took the following photos in the Rotterdam zoo: c:File:Rotterdam-zoo-ginglymostoma-cirratum-0.jpg, c:File:Rotterdam-zoo-carcharhinus-1.jpg, c:File:Rotterdam-zoo-carcharhinus-2.jpg, c:File:Rotterdam-zoo-carcharhinus-3.jpg.

The sign says that the aquarium has four species of sharks. (A previous version of this question listed only two species.)

• Carcharhinus plumbeus (sandbar shark, atlantische mensenhaai, Atlantischer Mensenhai).
• Carcharhinus limbatus (Blacktip shark, zwartpunthaai, Schwarzspitzenhai).
• “Carcharhinus limbatus”, probably a typo for Carcharhinus acronotus (blacknose shark, Zwartneushaai, Schwarznasenhai).
• Ginglymostoma cirratum (Nurse shark, w:nl:Verpleegsterhaai, w:de:Atlantischer Ammenhai).

However, I know basically nothing about sharks or cartilaginous fishes, so I can't distinguish between these species. It is possible that multiple species are represented on these images. Can you identify the species of (some or all of) the sharks depicted? Thank you for your help in advance

– b_jonas 20:56, 24 October 2020 (UTC)

All the pictures look like nurse sharks to me, based on the caudal fins, mouth shape, and bottom-dwelling behavior. bibliomaniac15 22:27, 24 October 2020 (UTC)

Thank you bibliomaniac15. I'll modify the metadata for the images according to that. But if anyone has a different opinion, feel free to answer still. – b_jonas 12:50, 25 October 2020 (UTC)

The same opinion: of the four cited arts three have a large first dorsal fin sitting in the middle of the backbone while the Ammenhai has it smaller and placed one third from the tail, near the second dorsal fin. Beside that only the Ammenhai has barbels and an uniform gray coulour, lives near or right at the bottom and spends the daytime in more or less large groups sleeping over eachother 2003:F5:6F15:5100:D908:99CE:27E:49EB (talk) 14:50, 25 October 2020 (UTC) Marco PB

Thank you for the confirmation. – b_jonas 16:58, 25 October 2020 (UTC)

NASA

The Moon photographed from Earth - no stars!!

When you see film shot by NASA there is a decided absence of stars. I would like to know; is that simply something that does not show up on film and when the astronauts are in space are they able to see stars? Do they not see stars or do they see an absolute plethora of stars. And why. Thank you — Preceding unsigned comment added by 2A00:23C6:6884:6200:D453:B0D7:E160:7942 (talk) 20:46, 24 October 2020 (UTC)

The exposure time isn't long enough to catch any except maybe the brightest stars. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:16, 24 October 2020 (UTC)

In more detail, the reason is that stars are not very bright. You can ordinarily see them at night (if the sky is dark enough where you are, and not cloudy) only because the human eye adapts to the darkness by enlarging the pupil well beyond the size it would be in daytime. All but the simplest cameras can achieve the same effect by adjusting the aperture or the shutter speed, but this affects the entire photo. If anything other than stars would be in the same photo, then it would be heavily overexposed. So when taking photos on the surface of the Moon, for example, the camera is adjusted so the ground and any people or devices in the picture are visible; but this makes the stars too faint to register in the photo. Astronauts can and do look at the stars from space, but they need to go into a dark room (or if spacewalking, look away from other objects) so they get dark-adapted the same way you would if you went out at night. See here. --174.89.48.182 (talk) 21:23, 24 October 2020 (UTC)

"Conspiracy theorists argue that the lack of stars in the Apollo 11 mission photographs prove that the event was staged. NASA could not have faked the full wonder of the lunar sky, and so they simply chose not to include any stars at all." Bumptump (talk) 23:25, 24 October 2020 (UTC)

Yes, that's just one of the many flawed arguments in that conspiracy theory. You don't hear about it so much nowadays. I suspect they moved on to other hoaxes, like Pizzagate and Qanon. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:09, 25 October 2020 (UTC)

Another reason why the moon landing hoax theory is nonsense is that the Soviets acknowledged the American achievement. Since the space race really was a race, they were trying to get to the moon before we were. If they hadn't believed it, they would have said so. But the Soviets were rational enemies. Robert McClenon (talk) 00:47, 25 October 2020 (UTC)

That is just proof that the conspiracy runs deeper. Either the Soviets are in on it, or the Soviets are am invention of the Deep State Illuminati, too! --Stephan Schulz (talk) 21:14, 25 October 2020 (UTC)

Neil deGrasse Tyson tweeted recently "Rumor has it that Neil Armstrong and Buzz Aldrin agreed to fake the Moon landinig. But to make the footage look as authentic as possible, they urged NASA to film it on-location. And NASA agreed." :) --TrogWoolley (talk) 13:39, 27 October 2020 (UTC)

For the reason given above by 174, you don't see stars in photos of the Moon taken from Earth either. Adding stars to the background of the Apollo 11 photographs would have been an easy job even for amateur photographers with a dark room. The idea that the conspirators at NASA would not have been capable of this, should they have wanted to do so, is by itself ludicrous.  --Lambiam 08:46, 25 October 2020 (UTC)

You're being logical. For conspiracy theorists, logic don't enter into it. :) ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:36, 25 October 2020 (UTC)

I added a photo (at the top of this section) of the Moon taken from Earth. It illustrates what happens to stars when the camera exposure is set to photograph something lit by the Sun. If the exposure was high enough to show stars, the Moon would be blown out. Bubba73 ^{You talkin' to me?} 23:54, 26 October 2020 (UTC)

To clarify, "blown out" means it would be so badly overexposed it would look white, or mostly so. --174.95.161.129 (talk) 05:59, 28 October 2020 (UTC)

Another photo with stars taken by Apollo 16 using the Far Ultraviolet Camera/Spectrograph is at Moon landing conspiracy theories#Photographic and film oddities. Alansplodge (talk) 12:12, 27 October 2020 (UTC)

A bit of fun on Neil's part, as on 30 May he tweeted:

Amid the turbulence of a pandemic & racedemic, I offer this reflection of what Earth looks like from space, as only an Apollo astronaut can tell it.

You develop an instant global consciousness, a people orientation, an intense dissatisfaction with the state of the world, and a compulsion to do something about it. From out there on the moon, international politics look so petty. You want to grab a politician by the scruff of the neck and drag him a quarter of a million miles out and say,

"Look at that, you son of a bi*ch."

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