Recent comments in /f/askscience

Plane_Pea5434 t1_j4u08ws wrote

Reply to What happens to the energy of sound in space? by full_hammer

The energy dissipates in other forms, if you yell (assuming no spacesuit) the air will just go out and keep travelling trough space, if you do have a suit the the vibrations will eventually become heat that will be radiated in to the vacuum, remember that sound is how we perceive the movement of the air and not exactly a kind of energy

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IAmTheFloydman t1_j4tzqs1 wrote

Reply to Extinction of the Dinosaurs: What did I miss? by cakedayCountdown

The impact hypothesis was controversial for many years, even after the Alvarezes published their findings in 1980 about iridium deposits that were almost impossible to explain any way other than an asteroid impact. Some scientists still favored existing hypotheses, including volcanism, sea level changes, and even chronic constipation. (See Keith M. Parsons' "The Great Dinosaur Controversy" published in 2003.)

Many scientists believed that major collisions between celestial bodies ceased long before the dinosaurs went extinct. It wasn't until 1994, when Shoemaker-Levy 9 crashed into Jupiter, that we witnessed such an event occuring. 100% undeniable proof that collisions still occured, which meant they definitely could have occured 65 million years ago.

There was also the problem of the impact crater. The original 1980 paper was based on iridium deposits around the world, but there was no known impact crater of sufficient size that could be dated to the right time. The Chixulub crater was discovered in the 1970s, but it wasn't identified as an impact crater until 1990. (Previously, it was thought it may have been a volcanic caldera.)

All this is to say, evidence has trickled in to support the impact hypothesis, and while the pieces were there in the 90s, it has taken some time to put them all together.

And the discussion isn't over either! While many experts got together and concluded in 2010 that an asteroid impact was the main cause of the K-Pg (formerly K-T) extinction event, there is still significant evidence that volcanism at least played some part. The dinosaurs may well have been on the decline for a long time, and the impact simply sealed their fate. Anyone who says "the asteroid killed the dinosaurs" is probably oversimplifying a complex issue, but it would be a huge mistake the ignore the asteroid impact altogether.

Source: A 2015 essay I wrote as an assignment covering a controversy in science during my undergraduate studies.

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Paracelsus19 t1_j4tzpue wrote

Reply to My 4y/o told me her dream about losing teeth without ever knowing it's a common dream. Are there any other examples of cross-cultural phenomena that centers on a specific narrative? by koleslaw

Here's two links, one is for the overlap in general dream themes across different cultures and the other is an exploration of the tooth dream as a common global phenomenon- the idea that it relates to the "incorporation of dental irritation into dreaming" is an obvious explanation that I never thought about honestly.

https://3quarksdaily.com/3quarksdaily/2015/01/typical-dreams-a-comparison-of-dreams-across-cultures.html

https://www.frontiersin.org/articles/10.3389/fpsyg.2018.01812/full

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being_interesting0 t1_j4tyanf wrote

Reply to What determines the lifespan of a species? Why do humans have such a long lifespan compared to say a housecat? by Forking_Shorts92

Here is a paper that suggests epigenetics plays a large role. https://www.nature.com/articles/s41598-019-54447-w

It is true that mammal size is correlated to heart rate, and both are correlated to lifespan. Most mammals get about 1 billion heart beats. Humans have managed to beat this by being more social (supporting our elders in pre-medicine societies) and then using medical technology to really overcome natural entropy.

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BurnOutBrighter6 t1_j4twgkk wrote

Reply to Why, and how, does a combination of isopropyl alcohol and salt, plus a lot of shaking, remove the resin tar from the inside of a water pipe? by dankantspelle

Isopropyl alcohol is a good solvent for resin/tar. Salt is not very soluble in the alcohol and acts as a scrubby abrasive that can get into every curve and crevice, while not being hard enough to scratch up the glass. You could use isopropyl alcohol and sand and it would clean great but scratch the glass over time.

Plus the salt easily and cleanly rinses away in water after you're done cleaning (vs something like sugar).

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