Why tardigrades are so hardy, how their biology is so different?
How immune system and medications work.
Why some plastics are recyclable and others are not.
Ask HN: What scientific phenomenon do you wish someone would explain better?
11–20 of 839 posts
Re: Ask HN: What scientific phenomenon do you wish someone would explain better?
#12Re: Ask HN: What scientific phenomenon do you wish someone would explain better?
#13The Coriolis Force
Re: Ask HN: What scientific phenomenon do you wish someone would explain better?
#14How can metric expansion of space redshift light? Doesn't that violate conservation of momentum, since the redder light has lower momentum? And adding on to that: Will light inside a box redshift? If I weigh the box (i.e. weigh the light inside the box), then wait a bit for the light to redshift, then weigh the box again?
You are correct! Cosmological redshift does violate conservation of momentum (and energy as well [1]). But conservation of energy and momentum does not actually apply if spacetime itself is globally changing.
The underlying reason for this is that Noether's theorem tells us that every physical symmetry implies a conservation law for some physical quantity. Conservation of energy and momentum comes from the fact that the physical laws are the same throughout time and space. However, cosmological expansion violates that assumption, so there is no reason that energy and momentum should still be conserved. [2]
[1]: One side note here is that relativistically, energy and momentum are not really separate physical quantities, but instead two components of the same underlying physical quantity. Unfortuantely, this quantity does not really have a good name (despite Taylor & Wheeler's attempt to call it "momenergy"). It ends up being called the momentum 4-vector, but the temporal component of this 4-vector is energy.
[2]: This is only true globally. Locally, the laws are approximately the same from one moment to the next, so conservation of energy and momentum hold for small distances and short times.
Re: Ask HN: What scientific phenomenon do you wish someone would explain better?
#15Another frustrating one - what is heredity? If it's possible to inherit something due to a shift in behavior (i.e. it's a cultural change that leads to a biochemical change), how does that connect neatly to mendalian inheritance?
Are you talking epigenetics? It's relatively closely related to mendelian inheritance. At a high level view, if genes are present in your genome that aren't "on" in a previous generation, but due to changes in behavior become more active, then in a future generation that gene could be expressed more. It's not that the genes have changed their code, they are just flipped on or off.
No, more things that are modifications without any genetic basis - like myopia. Doesn't seem to have any genetic/epigenetic basis. It's purely a physical use case, where the eye matures improperly if it's only exposed to near-field work.
Re: Ask HN: What scientific phenomenon do you wish someone would explain better?
#16Orbital mechanics
I've been meaning to do a bit of blogging about this since my thesis work was on gravitational dynamics. Is there anything in particular you would be interested in seeing explained?
Re: Ask HN: What scientific phenomenon do you wish someone would explain better?
#17Orbital mechanics
Have you heard of / played the game Kerbal Space Program?
I believe even folks at NASA have even said it helped cement their mathematical knowledge with a better intuitive understanding.
Re: Ask HN: What scientific phenomenon do you wish someone would explain better?
#18Quantum Mechanics, and why we need interpretations of it.
I have tried to grok it multiple times but escapes my feeble mind. I have developed some intuition, but not sure it's quite right. Hopefully someone can correct me:
1. Subatomic Matter is by default both mass and a wave, but when "observed" it becomes a particle as we know it i.e. with mass.
2. Atomic bonds are formed due to electrons (waves) being shared between adjacent atoms.
Hope I have some parts correct. Perhaps someone can shed some photons.
Re: Ask HN: What scientific phenomenon do you wish someone would explain better?
#19Protein Folding
Protein folding is amazing! Seems like it happens in realtime as it's synthesized by the ribosome.. I'll dig around and see if I can find a better resource for you.
Re: Ask HN: What scientific phenomenon do you wish someone would explain better?
#20Protein Folding
Isn't protein folding considered one of the biggest problems ever?