Recent comments in /f/askscience
kam_era_guy t1_jas3hif wrote
Reply to comment by alyssasaccount in What exactly does Spaghettification mean? by mark0136
so the human body cannot snap in half if pulled apart with huge amounts of force?
[deleted] t1_jas1c31 wrote
alyssasaccount t1_jas19c0 wrote
Reply to comment by kam_era_guy in What exactly does Spaghettification mean? by mark0136
> would happen due to the magnetic field way before gravity
There isn’t necessarily any magnetic field. Spaghettification happens even in an idealized non-rotating, charge-neutral black hole.
> ripping of the physical structure across the weak points
Those points are bonded together by some kind of chemical bond, like hydrogen bonds between different atoms.
kam_era_guy t1_jas0ghz wrote
Reply to comment by alyssasaccount in What exactly does Spaghettification mean? by mark0136
I feel like the ripping of molecules would happen due to the magnetic field way before gravity has a chance to do so. And also gravity would first cause the ripping of the physical structure across the weak points ( joints and such? idk too much about anatomy).
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[deleted] t1_jaryttx wrote
Reply to comment by Ape_Togetha_Strong in Why do cosmologists say that gravity should "slow down" the expansion of the universe? by crazunggoy47
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annomandaris t1_jaryr0b wrote
Reply to comment by paleopuzzler in What exactly does Spaghettification mean? by mark0136
Imagine your hands are tied to the ceiling, and then they attach 5 ton weights to each of your legs.
That’s what spaghetification like in real life.
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ferrdek t1_jarv0ep wrote
Reply to comment by mfb- in Why do cosmologists say that gravity should "slow down" the expansion of the universe? by crazunggoy47
>"Warped" does not mean "expanding". It's more of a local deformation
Lets assume we have some point in space and we travel through it twice. First time the space is empty and the second time some massive object appear on our path (for instance a star) and we travel close to it, going through space warped by its gravity.
is the time needed to travel from point A to point B in warped space longer than time needed to travel that distance through unwarped space? Or the opposite? Or there is no difference?
Blakut t1_jars76x wrote
Reply to comment by 4a61756d65 in Why does a Thorium gas mantle, when incandescent, emit more light in the visible spectrum than in infrared, when compared with a black body with the same temperature? by [deleted]
no they are not, i was thinking of something completely different. The stuff i work with, astrohysical sources, usually have two kinds of spectra: continuum which can come from a few things, such as free free emission, synchrotron emission, thermal emission from dust, and spectral line emission. The thermal part of the spectrum is usually very close to the ideal black body and deviations happen moslty because of geometry of particles (such as dust) and other stuff along the way, so i can separate the continuum from the spectral part. This of course gave me the wrong impression that most objects (also on earth) must have a spectrum close to a black body, and deviate from that only slightly because of things "around" the emitting body, such as gases absorbing/emitting, without considering that of course, Kirchoffs law applies to solids and everyday objects too (i only studied this in relation to gasses and some line emission scenarios).
alyssasaccount t1_jarry8z wrote
Reply to What exactly does Spaghettification mean? by mark0136
In short, it’s basically a hybrid.
From the point of view of a body experiencing it, it’s just an extreme tidal force (which is not actually a force, but the rate of change of acceleration induced by some force with respect to position). It is space time being stretched, and that would produce tension on an object falling into a black hole (and I think there’s also compression in directions perpendicular to that tension, as depicted in the image you shared, but I don’t recall the details off the top of my head). Early on, that tension is not sufficient to break apart molecular bonds, but eventually it is, and the object will indeed get ripped apart. Eventually that tidal force might be strong enough that molecules get ripped apart, and at some point the curvature could be enough that you have to modify the very description of fundamental particles, at which point you’re getting into questions of quantum gravity, which are beyond the scope of experiment at present, and for which there are no generally accepted theories.
mfb- t1_jarqhow wrote
Reply to comment by ferrdek in Why do cosmologists say that gravity should "slow down" the expansion of the universe? by crazunggoy47
It means spacetime is no longer the simple Minkowski space of special relativity. "Warped" does not mean "expanding". It's more of a local deformation.
4a61756d65 t1_jarq3pl wrote
Reply to comment by Blakut in Why does a Thorium gas mantle, when incandescent, emit more light in the visible spectrum than in infrared, when compared with a black body with the same temperature? by [deleted]
Ah, you're right, but you're not talking too much about the emitter when you show plank, just about the EM field itself (and if you do it somewhat rigorously you at least mumble the words ergodicity/equidistribution, which fail in dilute gases with quantum electrons for example, so you get emission lines) I'm saying classical electrons are not enough to explain emission fully even in solids (that being said I don't know much/anything about the thorium case specifically)
Blakut t1_jarouro wrote
Reply to comment by 4a61756d65 in Why does a Thorium gas mantle, when incandescent, emit more light in the visible spectrum than in infrared, when compared with a black body with the same temperature? by [deleted]
But the planck spectrum uses quantum physics... It cannot be explained classically.
edit: idk why i considered gases (which i thought i know) and solids (which i know i don't know) as so different. Kirchoffs law applies to solids too, so if a solid is a poor absorber at a wavelength, it must be a good emitter.
4a61756d65 t1_jarn8c0 wrote
Reply to comment by Blakut in Why does a Thorium gas mantle, when incandescent, emit more light in the visible spectrum than in infrared, when compared with a black body with the same temperature? by [deleted]
Yeah, you can derive some forms of thermal emission from pretending electrons are classical point charges. That doesn't mean doing it will always explain the real world correctly! That's why we need quantum physics.
Quinny-o t1_jarn89m wrote
Reply to If cancer is caused by mutations in genes that regulate normal cell development/division, how does killing cancer cells prevent it from coming back? by [deleted]
You can have genetic mutations that leave you more susceptible to getting cancer. But it’s the cells that mutate…for example, a keratinocyte, that if dividing haphazardly will develop into squamous cell carcinoma (a skin cancer). You can’t change your DNA but things like lifestyle modifications go a long way. For example just because someone has a gene for breast cancer, does not mean that they will get breast cancer.
heresacorrection t1_jas3i1z wrote
Reply to Does being sick impair the body’s ability to form memories during that time? by Temporary_turbulance
Does being sick reduce your ability to form memories and remember? Yes https://www.jwatch.org/jp199906010000009/1999/06/01/does-fever-affect-memory
Confirmed in rats: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2630971/
Is amnesia (completing forgetting events) associated with being sick? I would say very rarely - since the only documented cases I could find were mainly in the elderly where the infections cause significant brain damage. https://pubmed.ncbi.nlm.nih.gov/14589627/
EDIT: found a case in a younger person - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3766455/ so yes it could happen but is clearly so rare that doctors can publish a paper when it occurs