Recent comments in /f/askscience

Ausoge t1_j9hgy53 wrote

Reply to comment by alien_clown_ninja in What are more accepted hypotheses that similarly explain the aspects of hominid evolution that the "pseudoscientific" aquatic ape theory does? by KEVLAR60442

However we do have several adaptations that are very well-suited to the endurance hunter lifestyle - the ability to sweat (quite rare in animals in general), hairlessness (which allows passive heat radiation as well as more effective sweat evaporation), a large surface-area-to-volume ratio (again, good for surface cooling), an upright stance allowing us to see greater distances than most prey animals, and bipedal locomation, which is not very fast but is extremely energy-efficient. We also have spectacularly well-adjusted physiology for the throwing of projectiles, which somewhat compensates for our lack of speed. Our combined torso and shoulder mobility is unparalleled in the animal kingdom.

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Yda_Raven t1_j9hg9t2 wrote

Reply to Are the flu strains we vaccinate against more or less the same world-wide? by heyheyhey27

This is actually a big question to answer because a lot of surveillance goes into it. It's not just about looking the past strains of flu which have been circulating and which strains went into the vaccines. It's also how the populations current immunity reacts to the circulating viruses in lab tests.

There are several WHO Collaborating Centres around the world which receive virus samples taken from positive flu cases sent by various National Influenza Centres globally. The virus samples are put into culture in the hope they grow, sequenced if they do and a genetic tree is made to see if there are any obvious outliers, strains to watch etc.

During this time there are calls for blood donations (usually from people who work in these places!) pre and post flu vaccination. The serum from the blood is sent to each WHO collaborating centre so they can be used to test against viruses which are circulating/deemed of interest.

All of those results are pulled together ready for the vaccine composition meeting which happens twice a year (the northern hemisphere one is happening this week, southern is normally September) and a decision is made as to which strains of Influenza A and B go into the next jab. Then the candidate viruses get grown up, and passed on to the manufacturers of the vaccines. This has a time limit, about 4-5 months before the new vaccines and reagents for testing them have to be sent to the WHO Essential Regulatory Laboratories (ERLs), to undergo strict quality control tests to ensure they meet the standards expected before being used in the public health care system.

This video actually explains it quite nicely if TLDR! Monitoring Influenza Around the World

You can also learn more about GISRS and the Global Influenza Program here https://www.who.int/teams/global-influenza-programme#

This is actually my job, I work within the GISRS network - used to be in an ERL, now a WHO CC.

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CuppaJoe12 t1_j9hfdqu wrote

Reply to Does high altitude supersonic flight push air into space? by CertainlyUnreliable

The average thermal energy of a particle in an ideal gas depends on temperature. We can pull average velocity out of the energy if we know the mass of the gas particle.

Thermal energy = kinetic energy

3/2 k_b T = 1/2 m v^2

Rearrange:

v = sqrt( 3 k_b T / m)

  • k_b = boltzmann constant = 1.4e-23 J/K
  • m for a nitrogen molecule = 28 amu = 4.6e-26 kg
  • T in the stratosphere is around 220-270K, lets pick 250 arbitrarily

Plugging in yields v = 477 m/s. Oxygen would be slightly slower due to being more massive.

At sea level, the speed of sound is around 340m/s, and it decreases as you go up. In other words, the average air molecule is already bouncing around in the stratosphere at supersonic speeds. A collision with a supersonic aircraft would be absolutely unremarkable in terms of accelerating a gas molecule out of the atmosphere.

UV photochemistry and solar wind are the main ways gas is able to escape the atmosphere. Also, the above velocity is the average velocity. There are rare gas particles going much faster such that some gas can escape the atmosphere just by bouncing off other gas molecules ("thermal escape").

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alien_clown_ninja t1_j9hc2xj wrote

Reply to comment by PJHFortyTwo in What are more accepted hypotheses that similarly explain the aspects of hominid evolution that the "pseudoscientific" aquatic ape theory does? by KEVLAR60442

The endurance hunting hypothesis is on the same pseudo-science grounds as the aquatic ape hypothesis. Humans evolved in rocky terrain, where it would have been very difficult to track animals. And there is concrete evidence against it too. In the one place where animal remains with evidence of being eaten have been discovered alongside early humans, the bones were mostly adult and fit animals in their prime, not young or old which would be the easiest to catch by endurance hunting.

More likely is that early humans were ambush hunters, waiting in the foliage for an unlucky animal to walk by. It's possible that there were groups of humans that used endurance hunting, possibly for sport rather than survival (this is what the only groups of people who practice it today do).

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kelroe26 t1_j9hbrcr wrote

Reply to comment by GeriatricHydralisk in What are more accepted hypotheses that similarly explain the aspects of hominid evolution that the "pseudoscientific" aquatic ape theory does? by KEVLAR60442

I know people on the internet normally say this sarcastically, but I mean it with all sincerity. You must be a lot of fun to talk to at parties! That's a really cool and concise delivery of some very interesting information. Thanks, Queen/King

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