Recent comments in /f/askscience

backroadtovillainy t1_jdu56vj wrote

Reply to comment by [deleted] in Can elephants canter or gallop? by [deleted]

A lot of animals can be forced into unnatural movement like this elephant. Horses bounce or hop on their front legs the same way when hobbled.

But it's not natural, and causes a lot of painful wear on their bodies from long term unnatural movement. No wild elephant would get around this way because it probably hurts. Imagine how sore you would be if you had to hop everywhere and couldn't walk? Just because you technically can move that way doesn't mean you ever would.

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Nikkolai_the_Kol t1_jdu3qol wrote

Reply to Why are nonhuman erect bipedal animals so rare? by violetmammal4694

True bipedalism is pretty rare. Frankly, toddling around half-unbalanced is a good way to get eaten in the wild.

In all seriousness, in a tetrapod body plan (four limbs), to get bipedalism, one needs an adaptive change for the other two limbs. If the two front limbs aren't doing anything useful, generally speaking, evolution favors keeping four legs, rather than withering perfectly useful limbs. Obviously, that's a generalized statement, but let's talk about specialized forelimbs.

In humans, they are for fine manipulation. This is also true in all the great apes, bears, raccoons, otters, and the like. Hominins are the only ones, apparently, to get full bipedalism for this reason, and that is likely because we were the only ones with the right evolutionary pressure.

In badgers and pangolins, it's digging. (Badgers have only partial bipedalism.)

In birds, it's flight. (Yeah, all birds are bipedal!)

In penguins, their wings adapted for swimming control.

For other flightless birds (emus, cassowaries, etc.), current thinking is that they first evolved flight, then evolved to no longer have flight (say, when evolutionary pressures and genetic happenstance favored them being big enough to fight back, instead of flying away).

Now, imagine the evolutionary pressures that led to snakes losing all four limbs!

So, basically, the four-legged form just needs a genetic mutation and a complementary evolutionary pressure to encourage bipedalism, and there just aren't very many reasons to pressure for full bipedalism.

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mfb- t1_jdu3qaz wrote

Reply to Can you entangle more than two particles? Can entanglement be produced on a macroscopic scale to observe new physical interactions? by and-no-and-then

In principle you can entangle as many particles as you want. A prominent example is the GHZ state. You can also get entanglement with effective particles like phonons where you could say the entanglement includes the whole object.

The more particles you include the harder it tends to get to preserve entanglement.

> Where two particles interact regardless of the physical distance between them.

They don't interact with each other.

> can this be expanded [...] to observe things like additional dimensions or new physics?

No.

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Rootriver t1_jdu2vtj wrote

Reply to comment by Chalkarts in Around 550 million years ago the earth's magnetic field almost collapsed, but then strengthened a few million years later. Scientists say this may have been due to the formation of the inner core. But why exactly would that cause the magnetic field to get stronger? by somethingX

> Made me wonder if magnetism and gravity were the only forms of “drag”

Yes and no (at least according to the current main theories of physics). In a way in that scale gravitation and electromagnetism are the only meaningful forces, but forces (or rather interactions) called strong interaction and weak interaction can have pretty drastic local effects (these forces only work on very short distances, i.e. atomic and subatomic level) that can then affect the things on larger scale.

https://en.m.wikipedia.org/wiki/Standard_Model

Note: my knowledge here is bit rusty (pre observed Higgs boson) and elementary level.

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RoomyPockets t1_jdu2v9s wrote

Reply to If there was a hole in the ISS, would everyone get sucked out like in Sci-Fi movies? by hobbitlover

Just a technicality: the air is blown into space, not sucked into space. It's the internal pressure of the air that causes it to rapidly expand into the vacuum. As to whether it will take you out with it, that's down to how big the hole is. If left unchecked, the air will keep escaping until there's a vacuum left inside the ship.

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