Recent content by Amaterasu21

Hi all, In the Jovian system, Callisto is extremely dark (albedo 0.22) because its ancient surface is covered with meteoritic dust. Ganymede is brighter (albedo 0.43) as its surface has been resurfaced more recently and hasn't had as much time to accumulate dust; that's confirmed by the younger...

That all makes sense - the bends, of course! Thank you!

Hi, a thought just occurred to me. We all learned in school that oxygen diffuses from the air in the alveoli into the blood, and carbon dioxide diffuses from the blood into the air to be breathed out. But they never mention nitrogen, argon or any of the other gases in the air! Does something...

Hi all, I've been thinking about a hypothetical circuit with (say) a 6V cell of negligible internal resistance, a 4V cell of negligible internal resistance, and a resistor in parallel with each other, and I can't figure out what the potential difference across the resistor would be. I've tried...

Ah, all of what you're saying about this being due to kinetic energy not being frame invariant makes a lot of sense. Thanks everyone! That's answered to my satisfaction. I hope I got my message about the cosmological redshift correct as well!

Hi all, My question is about Doppler redshifts, but I'm going to mention cosmological redshifts first because I'm a lay person as far as cosmology's concerned (I'm an amateur astronomer and did a few introductory astrophysics/cosmology courses at university, but my degree focus was planetary...

Let's say we use a very high charge at the surface of a planet with very strong gravity, so the acceleration's enough to produce a photon we can detect with the photoelectric effect. Does that mean if we allow the photosensor to fall freely, it could detect a photon, whereas if we put it on the...

1) I can't find a query similar to this one on the forum, sorry. 2) I've found a few sources that say it will, though: This paper: https://core.ac.uk/download/pdf/25269331.pdf Apparently the energy carried by the radiation comes from the gravitational energy of the system, but I'm not sure...

So what would happen to a charge sitting on the surface of a non-rotating mass? (I got 5.5*10-52 watts btw - okay, a very small amount of power. But the fact there's any power radiated at all confuses me since it'd need some sort of energy source, and the rotation of the Earth doesn't seem like...

General relativity tells us that an object in free-fall is actually inertial, following a geodesic through curved spacetime, and not accelerating. Instead, it's objects like us, on the surface of a large body, that are accelerating upwards. Maxwell's equations also tell us that accelerated...

Yes, stress would be proportional to strain, but what I was concerned about is force also being proportional to extension. I've seen both of those relationships labelled as "Hooke's Law," but I struggled to see how both could apply to the same spring at the same time because L/A would have to be...

That makes sense, but it also appears incompatible with this paragraph further down (italics mine): "The first stage is the linear elastic region. The stress is proportional to the strain, that is, obeys the general Hooke's law, and the slope is Young's modulus." The two graphs there also seem...

Thanks for the responses! hutchphd: That's fair enough if you're just going to slap a number named "Young's modulus" on a material and call it a day, but I'm talking about a stress-strain graph and why its slope is constant up to the limit of proportionality. Maybe the term "Young's modulus" is...

Hi all, I'm a little confused about something. Force-extension graphs and stress-strain graphs are always both straight lines up until the limit of proportionality, implying both the spring constant and the Young modulus are constant up until then. For a force-extension graph, Hooke's Law...

Thank you, that makes a lot of sense!