Why do Auroras change colours? Why are some colours rarer than others? | AskScience Blog

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Thursday, March 7, 2019

Why do Auroras change colours? Why are some colours rarer than others?

Why do Auroras change colours? Why are some colours rarer than others?


Why do Auroras change colours? Why are some colours rarer than others?

Posted: 06 Mar 2019 10:55 PM PST

Could a fast enough spaceship become a black hole?

Posted: 06 Mar 2019 07:32 AM PST

Any object with mass gains weight as it gains speed. Near the speed of light we always say that it gains "infinite" mass, thus it requires infinite enegy to get to the speed of light. My question is that is there a point where the object is so massive because of this that its radius would become lower than the Schwarzschild radius, and should become a black hole? If yes, what would happen? Wouldn't the object slow down enough, that it would revert back from this state?

Let's assume, that we have a spaceship that can stand the forces imparted on it, we have infinite fuel, and an infinite clear path in space to do that.

Edit: Thank you for all the great answers, and thank you for the stranger who gave the post gold. <3 u all

submitted by /u/A11ce
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Does cannibalism REALLY have adverse side effects or is that just something people say?

Posted: 07 Mar 2019 01:07 AM PST

What allows the element "oganesson" to have its (apparently) unique properties?

Posted: 07 Mar 2019 12:06 AM PST

See this comment:

Oganesson is really strange. It might not have any electron shells, and it's probably a solid at room temperature - which is mad considering it's in the noble gases!

https://www.chemistryworld.com/news/immense-oganesson-projected-to-have-no-electron-shells/3008104.article

Apparently its strangeness is due to relativistic effects, but I don't really understand what that precisely means.

See this comment that mentions the relativistic effects:

It's not so much the properties of the element, but properties of the isotope of that element. You'd get much longer lived isotopes, so you could have an element that lasts years rather than seconds.

In terms of the properties of flerovium - that's something that nobody's really sure about at the moment. It looks pretty unreactive, but at this point in the periodic table you start getting huge relativistic effects. The most interesting upshot of that theorised so far is with element 118 - which might not have electron shells!

submitted by /u/FunUniverse1778
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How does the "plug" of skin cut out by injecting someone with a hypodermic needle or IV not clog the needle and then get pushed into the blood stream and cause problems by clogging capillary blood vessels?

Posted: 07 Mar 2019 06:12 AM PST

From my understanding the needle is hollow with a pointed end, and it seems like this would act like a leather punch and cut a disk of flesh out, which would then clog the needle and be forced into the bloodstream when the medicine is injected. How does this not cause problems when it enters the blood stream? Do needles not work that way?

submitted by /u/CokeCanNinja
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Why did multicellular organisms evolve genders?

Posted: 07 Mar 2019 02:57 AM PST

Life appeared first on this planet as unicellular organisms, and then evolved into multi-cellular ones. However, I was wondering why and how gender came into being in the first place.

submitted by /u/ExpertVentriloquist
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Can Hardness be calculated from Toughness and material strength?

Posted: 07 Mar 2019 06:59 AM PST

Ex. If a material I have heard of but can't access has a reported toughness of 5.7 kJ/m2, and a material strength of 4.8x1011 Pa, as defined by this graph.

submitted by /u/DeismAccountant
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Time dilation due to gravity AND due to velocity (are they multiplicative?)

Posted: 06 Mar 2019 01:02 PM PST

So, in other words (and without the advantage of the Einstein field equations because they're over my head at this point).

I understand that I can calculate gamma using Sqrt(1-v^2/c^2) for an object orbiting a planet of mass M. Whatever the orbital speed needed to orbit at altitude R will plug in and give us the time dilation due to velocity. BUT, at the same time another gamma = Sqrt(1-2GM/Rc^2) because of gravity. Can you find total time dilation (relative to stationary earth observer) by multiplying both gamma's together?

t = t`(gammaGravity)(gammaVeloctiy) ?

Thank you to anybody willing to explain!

submitted by /u/MrPhysics2013
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Is there a large difference in in underwater pressure in a river where the water is potentially deep and swiftly moving?

Posted: 06 Mar 2019 07:42 PM PST

Does the water increase in pressure when it goes around a bend? Or does the water act like rush hour traffic and bumper to bumper its way around? Also taking into account the weight of the water above it. I know water does not compress, but I would assume the mass of the water would put some force on itself around a turn. I am also wondering about friction, would the water in the middle of a river be moving faster than the water along shore? If so does that mean there are essentially currents in the river so some is moving faster than the other? If the water is moving faster around a bend does that increase its erosion potential due to faster flow, or higher pressure from depth or inertia?

I know this is way more than one question that I am asking but the more I thought about it the more questions I had.

What triggered this rabbit hole was a curiosity about flash floods and how the initial debris field looks like a bulldozer. I was curious about how powerful the water is and how much soil it has the potential to cleave out from the landscape. I enjoy farming and I know here in Northern California Valley much of our rich soil came from the flooding of the mountain and foothill areas.

submitted by /u/Commando0861
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Hadron & recombination epochs: why do they always use "free electrons" as the culprit for blocking light?

Posted: 07 Mar 2019 02:58 AM PST

Actually this includes 2 related questions:

  • Why is Thomson scattering only caused by charged particles? EM radiation is weightless and isn't affected by charge. Therefore, why can't neutrons, neutral atoms and molecules scatter light just like free charged particles?

  • The 2nd one is more important. Near the beginning of the universe, there must be about equal amount of protons and electrons. As they're all free, and as the Compton wavelength of the proton is way way smaller than the electron (3 orders of magnitude), it is so much better at scattering light. Not to mention that its surface is also way bigger than the electron, therefore the chance of a photon encountering it is also magnified compared to that tiny electron. So why scientific papers always claim that light is effectively blocked by electrons without any mention to our bigger heroes, like in the Wikipedia article), for example: "This plasma was effectively opaque to electromagnetic radiation due to Thomson scattering by free electrons, as the mean free path each photon could travel before encountering an electron was very short."?

submitted by /u/Long_try
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What is the glassy looking substance breaking off of a space shuttle/rocket when it is launching?

Posted: 06 Mar 2019 04:51 PM PST

What is the earthly origin of the oxygen we breath?

Posted: 06 Mar 2019 07:29 PM PST

If I were to select a random molecule of oxygen that I just breathed and then trace it back to it's origins...what would it originate from on earth (or atmosphere)? Also, what is the path that that molecule took to reach my lungs today? What were the major steps it took to get here?

submitted by /u/speerow22
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What precisely makes a fusion-weapon "better" than a fission-weapon?

Posted: 06 Mar 2019 04:06 PM PST

My understanding is that a fusion-weapon only gets 50% of its yield from fusion (at most) and 50% of its yield from fission.

An expert mentioned that nobody has been able to make a bomb that gets 100% of its yield from fusion. (There have been efforts to come up with such a bomb, because fusion-products are not as nasty as fission-products, so a 100%-fusion bomb would have less-nasty fallout than any current bomb. However, these efforts have failed.)

This "no more than 50%" fact surprised me (if indeed it's true). My naive impression was that fusion was the "next level" in nuclear weaponry, and that you would merely have a fission-trigger; i.e., fission would account for some tiny fraction of the yield, and it would be 99% fusion-based yield. The fission would be just to get the thing started.

But if we're talking about 50-50, then that's rather unimpressive in terms of the fusion aspect.

What's so impressive about the fusion-aspect in these weapons?

See here for the expert-claim about how fusion generally only gives you 50% of your yield.

Edit: What exactly does the neutron-generator do/achieve? See here for the expert's description. I don't get what that really adds to the equation; just some extra neutrons? But how can that be relevant or add anything to the equation, given that there will be a massive number of neutrons released from the fissioning Uranium (which is the whole point, because is what causes the whole exponential chain-reaction)?

submitted by /u/FunUniverse1778
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Are there any organisms that can live in oil?

Posted: 07 Mar 2019 12:33 AM PST

In the same way that organisms live in water in the sea. From reading online, oxygen can be dissolved in oils (hydrocarbons) so this may indicate life is possible. However as oil molecules do not have a charge, they cannot dissolve salt and i assume other minerals, which may make it harder for life.

submitted by /u/AchillesFirstStand
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Are there any chemicals that act as excitatory transmitters on ligand-gated potassium channels?

Posted: 06 Mar 2019 08:20 PM PST

I know that Tetrodotoxin acts on potassium channels to inhibit them, messing up action potentials. From what I understand, an increase in activation of potassium channels seem to do nothing to the resting potential, since they (most of them) are always open anyways, so are there any chemicals that increase activation of K channels, and do they do anything to action potentials?

submitted by /u/bennettsaucyman
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Are death penalties recipients' blood and organs viable after chemical injection? If so, are blood and organs put on transplant lists?

Posted: 06 Mar 2019 04:52 PM PST

I know they inject the criminals with certain chemicals and compounds in the form of anesthetics, shut down lungs, and the heart. Do these injections make blood and organs unusable? If the blood and organs ARE viable, does anyone know if they are put on transplant lists?

submitted by /u/Bulbasaur_King
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What products do E. Coli excrete?

Posted: 07 Mar 2019 12:12 AM PST

What does E. coli excrete?

submitted by /u/REDoROBOT
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Can bacteria go extinct?

Posted: 06 Mar 2019 07:10 PM PST

Are there any reported cases of bacteria going extinct? How would/does that play into our definition of a communicable disease being eradicated (assuming it's bacterial)?

submitted by /u/NeedRandomButton
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At what stage do people typically "feel" cancer? How is it possible for someone to just get diagnosed at stage 4, at that point of metastasization shouldn't the person be in massive pain at stage 3 already?

Posted: 06 Mar 2019 05:27 PM PST

Just heard at Alex Trebek (Jeopardy! Host) was diagnosed with stage 4 pancreatic cancer. From what I know pancreatic cancer takes a long time (an average of 11.7 years before the first cancer cell develops within a high-grade pancreatic lesion, then an average of 6.8 years as the cancer grows and at least one cell has the potential to spread) and doesn't present a lot of symptoms at first. I understand normal people not having the time or money or even access to get checkups so they ignore that pain in their side that comes and goes until its too late, but again, Alex doesn't have any of those problems. Hes also 78, and shouldn't men be getting colonoscopies like every 10 years after 50? How does something like this slip through the medical health cracks for someone like Alex.

submitted by /u/ja20n123
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Why doesn't the sunset light all of the water?

Posted: 06 Mar 2019 06:14 PM PST

I know it sounds bizarre but hear me out:

When I watch a sunset on the beach, I see a beam of orange light on the surface of the water from the sun to me. When I move, it follows, and two people at different points have different lines of reflection. Why doesn't the light simply spread out and reflect across all the water, not just the streak in front of the source? Shouldn't it all be orange? I just saw a Reddit post of a sunset above the clouds, and even then, it reflects in that same line of orange, not across all the nearby clouds. The fact that cameras capture it tells me it isn't our eyes/brains, so what is it?

submitted by /u/SpencersBuddySocko
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What makes ice slippery? Even when it is below freezing ice is still slippery?

Posted: 06 Mar 2019 04:19 PM PST

Even hockey rinks or rubbing to ice cubes outside when it below freezing.

submitted by /u/Buzzinyo
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How do fruits and vegetables stay "fresh" in their peels after they're picked?

Posted: 06 Mar 2019 05:23 PM PST

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