I think you’d be better served to ask about the average volume of a cloud (if that makes sense, given how diverse they come). Because the mass is pretty much exactly volume multiplied with density. And the average density of clouds is pretty much exactly that of the surrounding air at the given altitude (because otherwise the cloud would not float, but either rise up or sink down). And the density of air at any given altitude is given by the Barometric formula. If you take a kubik kilometer of cloud (honestly, I have no idea how big clouds are), it would have a mass of approximately 364 thousand tons at 11 km above sea level, 88 thousand tons at 20 kilometers above sea level, 860 tons at 51 km above sea level and ca. 64 tons at 71km above sea level. But “regular” clouds only go up to ca. 20km, and 95% of the clouds you see are probably below 8km. Unfortunately the quoted wikipedia page has no entry for the barometric pressure at that altitude and I am too lazy to try and calculate it right now ;)
Researchers at the US National Centre for Atmospheric Research calculated the density of a cumulus cloud to be around 0.5 grams (0.018 ounces) of water per cubic meter, so a 1 cubic kilometer (0.24 cubic mile) wide cloud would contain 1 billion cubic meters (35 million cubic feet). If you calculate the number of cubic meters times by the density, 1,000,000,000 x 0.5, you’ll be left with the total weight of a cumulus cloud of that size – 500,000 kilograms (1.1 million pounds).
I think the term “weight” - while useful at sea level - can easily confuse people when it comes to clouds, as the density of the water in a cloud doesn’t have much to do with the weight of the cloud - see my elaborated edited response (unless I mis-guesstimated) - the mass of a cloud changes so drastically with altitude that the relative or even the absolute weight of water (vapor) therein is going to give people the wrong idea.
Oh shit good question. I’m gonna say no because I was really trying to ask about how much ice/water/dust is involved, but I’m also curious about the air.
This post on physics.stackexchange.com claims that hot accretion disks can reach 10^12^ K, hot enough for fusion to occur but not at rates that would make fusion a significant source of radiation from the disk.
Hi! Googling this question reveals the answer is yes, it does result in fusion.
As far as the output, according to this top result paper, that depends heavily on the size of the black hole, the size and speed of the accretion disk, and the medium from which the black hole is drawing (like a white dwarf vs interstellar gas).
From what I can make out–and I have no background–the author maps out results as high in weight as nickel.
I suppose the elements formed by fusion of hydrogen are pretty fixed. It’s mostly helium. Only the rate depends on the pressure and temperature of the fuel.
So I don’t know whether fusion happens in an accretion disk. But if it does, the elements formed are mostly helium, and a few other light elements at trace amounts.
Alternative theories of gravity are like alternative theories of medicine, they tend to be thoroughly invalidated and none are anywhere near as effective as the mainstream theory. As the wiki article you linked notes:
However, such models are no longer regarded as viable theories within the mainstream scientific community and general relativity is now the standard model to describe gravitation without the use of actions at a distance.
General relativitiy is one of the most tested, validated theories in physics. It is incredibly successful, not just describing the attraction of massive bodies but also describing frame dragging (solving a longstanding mystery on the retrograde motion of Mercury that Newtonian gravitation couldn’t explain), and predicting gravitational lensing and gravitational waves, both of which have been observed since and are perfectly described by GR.
An alternate model should attempt to solve a problem in the current leading one, for example giving a more fundamental explanation, or working at different scales where the current model fails (quantum gravity theories, for example). A good alternative model will also give results that are consistent with all existing observations, which is one area that every alternative theory of gravity I’m aware of fails. What problems in GR are you looking to resolve with an alternate gravitational model?
I’m not interested in questioning Einstein’s gravity - it’s super successful. I was interested in the history and alternative ideas that beaches out and died and the Wiki did have some decent info and even papers on “ether.” Fascinating and maybe intuitive for its time. It’s very hard to find any writing on postulating the mechanics that cause gravity to warp space/time. I was mostly interested in finding if there was some kind of wave function (not a graviton) within to describe the, “why.” There’s so much energy within atoms that you’d think there was more than enough room for hypotheticals, but none that are famous enough to discover on the Internet.
Yes, sound is the collective motion of particles in the form of a compression wave. As these waves propagate through a material and scatter off boundaries and inhomogeneities in general, they become less ordered and eventually indistinguishable from random atomic motion (i.e. thermal energy). However, in addition to this, sound waves can radiate away when in atmosphere. In the case of spacecraft, they can only dissipate into thermal energy and can therefore persist much longer. This is actually a problem engineers have to deal with, as unwanted vibrations can cause issues. There’s research looking into addressing this by using materials specifically designed to be highly absorbent to sound waves at particular frequencies (i.e. the collective motion of atoms at particular frequencies rapidly decays into random thermal motion).
Ok, that makes sense. I expected it to be kinetic into thermal.
But then in a place like the ISS with all the people all the time, does it mean extra heat inside? What would happen if you played loud music? I mean vacuum does not the heat away from you quickly, and there’s nothing to take the kinetic energy. After years of people talking and beeps beeping, where did it go?
I don’t have a great answer for you why, but heat must be radiated away from space ships faster than you might think. They have heaters on them to keep them warm. Think Apollo 13 when they turn off all their power, and it gets cold.
The ISS is traveling through a decent amount of atmosphere still, hence they need to boost their orbit occasionally. That atmosphere is probably plenty to dissipate WAY more heat than sound creates.
That doesn’t explain deep space ships… But they do clearly radiate heat, if not slowly. But probably faster than what little heat sound creates. (Also think of the cooling phase that James Webb space telescope went through)
Heat can transfer through conduction (basically thermal diffusion through physical contact), convection (bulk motion of matter, like gas or water flow), and radiation. For a spacecraft in low Earth orbit, the pressure is considered ultra-high vacuum, so you basically only have radiation to dissipate heat. Near room temperature, this would be mid-infrared light. The energy in everyday sound waves is very small, so body heat, on-board instruments, sunlight, and perhaps even IR emission from the Earth would be much more important contributors to heat build-up. However, regardless of the heat sources involved, there will always be some equilibrium temperature where the energy going into the system equals the energy radiating away.
To keep things comfortable for the crew on the ISS, there are passive and active systems to regulate the temperature [1]. For dissipating excess heat, large radiators are used. These are basically panels with a large surface area in order to maximize emission of thermal radiation. A closed-loop system is used to circulate fluid, which collects and transfers heat to these radiators. Water is used for some parts, but others have pipes on the outside that use ammonia to prevent freezing. The radiators themselves can be retracted or deployed as needed.
[1] Memi, E. G. “Active Thermal Control System (ATCS) Overview.” (2006): 19.
I’ve played a few games set in space and some of them have, in their quest to explain differences between the fiction and reality, a “simulated sound” system so you can still hear in space; would something like that actually be possible in real life? 🤔
In principle, you could have a system designed to image your surroundings (using cameras, LIDAR, etc) and perhaps some kind of machine learning algorithm to predict what kind of sound would be expected if the events around you were occurring in atmosphere. I imagine this could work well for simple things like a tool hitting a piece of metal, but would be probably run into issues when the events are affected by the lack of atmosphere or give little or no visual indication that they are occurring. And, of course, you wouldn’t be able to “hear” anything outside of the view of your imaging system.
No, they don’t annihilate. The electron will scatter off the other particle, though any differences in charge will of course affect the scattering. For example, an electron and a proton could become bound to make a hydrogen atom, but this couldn’t happen with an anti-proton. Any nuclear reactions (specifically electron capture) would be affected too.
In the case of free anti-neutrons, there’s a chance the anti-neutron could decay into an anti-proton and a positron. If this were to happen during the collision with an electron, the electron could potentially annihilate with the positron.
Absolutely. Sound waves are vibrations. Vibrations can be transmitted to other materials. Like electrical conductors, some materials conduct sound better than others. The amount of energy in sound is pretty low, so it’s not going to create a lot of heat or light, unless we’re talking about sound levels that would be dangerous to not only hearing but would cause death.
Any composite particle can have an antiparticle counterpart if you replace all of its constituent particles with antiparticles (e.g. anti- up and down quarks in the case of protons and neutrons).
Lol, but, for other readers, charge isn’t the only property that has an anti-component when making up anti matter.
Positrons are just the most easily explained and are what people are probably most familiar with.
Saying “electron but with a positive charge” satisfies the curiosity of most people who are smart enough to ask the question but don’t want to write a dissertation.
Plus, PET scanners take advantage of positron/electron annihilation to do their imaging, and that happens all over the world every day.
Which is kinda weird because where else in the world but medical imaging are regular people confronted with actual modern physics. Sure, semiconductors, but they don’t actually have to confront that.
Anyway, I do prefer to say “magic” rather than explain how an MRI works for a lot of people.
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