Wikipedia:Reference desk/Archives/Science/2020 August 19

= August 19 =

A "car-sized" asteroid
This Sunday, A car-sized asteroid made the closest Earth flyby a space rock has ever survived. The scariest part was that it was undetected. If it collided on Earth, what sort of impact would it have made? Of course, the effect would depend of whether it hit on land or sea, and it would partially burn up in the atmosphere. The asteroid responsible for meteor crater, Arizona, was relatively* small (about 50 meters across). --2606:A000:1126:28D:4010:D10A:69ED:7785 (talk) 01:31, 19 August 2020 (UTC)
 * The Chelyabinsk meteor was larger, with a diameter around 20 meters. The other main variables are its velocity and the angle at which it impacts the atmosphere. The shallower the angle, the more time before it can impact the ground, which makes it more likely to break up or explode in an air burst. --47.146.63.87 (talk) 05:14, 19 August 2020 (UTC)
 * A 4-meter rock would probably produce a brief light trail as it disintegrates in the atmosphere. Bigger rocks buzz the Earth every couple of days; see e.g. spaceweather.com "Near Earth Asteroids" table.  Every now and then a bored newspaper editor has nothing better to do than write a clickbait story about one of them.  85.76.78.82 (talk) 05:23, 19 August 2020 (UTC)
 * And of course the effects are very different depending of the composition of the body in question: the Arizona crater was produced by a compact and heavy block of iron-nickel with a density of about 8, while the Chelyabinsk meteor]was a rather brittle mix of rocks and iron with a density of about 3.7. It is estimated that about half of the mass of the Arizona meteorite reached the ground and produced the crater while the Chelyabinsk meteor would probably not have reached the ground at all even if it had fallen vertically. But of course the shock wave reaching the ground can still be impressive.
 * Thanks Iblis for the link. I used some credible parameters for a car sized stony chunk [] and it gives:
 * -The projectile begins to breakup at an altitude of 56600 meters = 186000 ft
 * -The projectile bursts into a cloud of fragments at an altitude of 37500 meters = 123000 ft
 * -The residual velocity of the projectile fragments after the burst is 16.7 km/s = 10.4 miles/s
 * -The energy of the airburst is 6.07 x 1012 Joules = 0.14 x 10-2 MegaTons.
 * -No crater is formed, although large fragments may strike the surface.

2003:F5:6F08:AF00:F87A:34E2:BFA7:387C (talk) 18:25, 19 August 2020 (UTC) Marco PB
 * On that calculation, is it 0.14 x 10-2 i.e; 0.0014 Mt (1.4 kilotons)? -- — Preceding unsigned comment added by 2606:A000:1126:28D:F936:DCD9:CC6E:A4F9 (talk) 20:40, 19 August 2020 (UTC)
 * Yes, I forgot the superscript but the original has 10-2 as you write. So 1.4 kilotons make rather a noteworthy bang but 123,000 ft over ground after all. 2003:F5:6F08:AF00:BD9C:D95E:7C63:1799 (talk) 18:44, 20 August 2020 (UTC) Marco PB

_____ * Relative to the size of the crater --2606:A000:1126:28D:4010:D10A:69ED:7785 (talk) 05:34, 19 August 2020 (UTC)


 * You can use this online program to calculate the effects of an impact. Count Iblis (talk) 14:04, 19 August 2020 (UTC)

Egg laying vs live birth Snakes, venomous vs non-venomous snakes
Recently on YouTube, I watched a well-done short documentary, (Smithsonian or National Geo) which showed the eggs of a wild black mamba snake (native to Africa) hatching. A few videos later, I saw a home video of a young, probably American couple, who had cared for snake eggs found in a backyard, which they placed in an aquarium type enclosure. On camera, they noted that the eggs had hatched, and the young woman started searching around in the sawdust-type material, with her bare hands!, to locate the baby snakes, so they could identify the snake species. (They were “racers”.)

My question: Do only non-venomous snakes in North America give birth by “eggs”? Or to put it another way, were the eggs a sure indication (in North America) that the snakes were non-venomous? Probably a stupid question, here.

But I wonder if there is some sort of world-wide divide, in terms of venomous vs non-venomous, and egg laying vs live young. Are the black mambas an exception? Hope this makes sense....thanks!  Tribe of Tiger Let's Purrfect!  02:28, 19 August 2020 (UTC)


 * So snakes have three general modes of reproduction (general because there's exceptions all over the place). They can be oviparous, which means that they're egg-laying, they can be viviparous, meaning that the embryo develops internally and then comes out in a live birth, or they can be ovoviviparous, which means that they retain eggs inside the mother, which often hatch internally and come out looking like a live birth. Parity and venom only really correlate insofar as they may be shared between members of the same family, but independently there isn't really a big correlation. Boas, for example, are nonvenomous and generally ovoviviparous, while the superficially similar (and nonvenomous) pythons are egg-layers. Vipers are venomous, and the majority are ovoviviparous, but some specific genera like the bushmaster snakes lay eggs. Terrestrial Elapids like the black mamba or cobras lay eggs (as you mentioned), but sea snakes in the same family mostly have live young, and some of those guys are really venomous.  bibliomaniac 1  5  03:31, 19 August 2020 (UTC)


 * As to the North America question, this site says that coral snakes lay eggs and are the only venomous snakes in North America that do. So a person from Canada or the north or central US, where coral snakes don't live, might be justified in assuming that an egg-laying snake is non-venomous. --174.89.49.204 (talk) 04:10, 19 August 2020 (UTC)


 * Well there is certainly a wide variety, as noted, no cut and dried sort of classification, worldwide! Thanks very much for this good outline, I shall study. Also for the answer regarding North American snakes. This makes sense. I believe that coral snakes are found in Texas, and my YouTubers did not appear to be clueless people, so I will cease to worry about their safety.


 * I gather that there are many snake enthusiasts in the US who collect non-native snakes, and there are problems with escaped exotics in Florida, pythons/boas? which are disturbing the natural food chain, as imported predators. But as noted, they are not venomous. However, an escaped Bushmaster might be unable to survive, even in Florida, which I suppose is the closest environment to its native habitat. Thanks so much to both of you for the conversation. Regards,  Tribe of Tiger Let's Purrfect!  04:47, 19 August 2020 (UTC)


 * It does freeze every year or two in Florida, except very south. Perhaps higher land animals don't freeze till 31 as seawater is 4 times as salty and freezes at 28 and pure brine is 39 times as salty and freezes at 0. Sagittarian Milky Way (talk) 14:23, 19 August 2020 (UTC)
 * I know some snakes hibernate/brumate together underground, avoiding the frost. I guess it depends on the species and the climate though. Zindor (talk) 18:50, 19 August 2020 (UTC)


 * Have now discovered that the couple in the video live in Arkansas. Although coral snakes live there, these people live in an area too far north for them to survive. Snakes, not people! :-) The note above, by is a point well-taken. I know that the endangered Eastern Timber Rattlesnake brumates, in areas as far north as New Hampshire, I think. So I suppose an escaped Bushmaster might survive in Florida.   Tribe of Tiger  Let's Purrfect!  08:52, 20 August 2020 (UTC)


 * I assume even newly hatched snakes would have venom, if the species is venomous, as parental care in most snakes is pretty rudimentary. However, a big portion of the danger of a snakebite is the amount of venom injected and this would obviously tend to be much less in a baby snake than an adult. But... refraining from using your fingers to poke around is still a great idea. If you must poke around, using a small stick would seem to be the wise choice. Matt Deres (talk) 16:52, 21 August 2020 (UTC)