swansont

Sure

Careful - they are not thought to interact via the weak interaction, but via some new method on the scale of, or weaker than, the weak interaction

One explicit avoidance of outright technobabble was the baryon sweep, which was an attempt to not just make something up http://blogs.scienceforums.net/swansont/archives/1043

If it could interact electromagnetically it would emit thermal EM radiation. The ability to emit light has implications about how it behaves - easy dissipation of energy would allow it to “clump” more readily. And “dark” is also an acknowledgement that we don’t know what it is, as beecee has noted.

Part of the reason it’s called dark is because it doesn’t interact electromagnetically, and is thus not visible

Folks, it’s fiction. Things are made up. There are attempts at continuity and they tried to not botch the science too badly, but at the end of it all, they’re telling a story. A friend from high school spent a year as the TNG science consultant (later was on the writing staff); I complained one time about an episode’s science and he admitted he was overruled because the writers liked the story line. There’s an excellent chance the discussion of the efficiency was to advance the story.

! Moderator Note Show us what you have done ! Moderator Note Absolutely not. This is homework help

It's all quantized, though, and so a photon being absorbed or emitted changes the angular momentum of an atom by the angular momentum of the photon, which is h-bar.

Not for any of the individual particles, since it's quantized. The only pathway for changing them is flipping the spin of an electron or causing an excitation of an electron to a state with a different orbital angular momentum. I'm not sure how that could happen just by re-orienting a rigid body. There would need to be a corresponding interaction down on the atomic level, and I can't think of a direct connection between the two.

Any alignment of an angular momentum vector is determined locally (it's with respect to the atom), so yes, the direction would have to change in a rigid body. But most electrons are paired up in multi-electron atoms, and there is nuclear spin to consider as well, so the amount of torque needed to achieve this is going to be quite small compared to what's necessary to rotate the body itself. We can see that this is the case because we can see it happen with a permanent magnet, which depends on unpaired electrons having a certain orientation within the material. The magnetic field depends on the orientation of the magnet, so if it is rotated, the spin orientation must have changed as well.

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Have we found few because there are few, or because detecting them is difficult? Like all humans are fascinated by e.g. bugs? Or is it that a few of them would be fascinated by us, and the rest are just going about their duties. No? Where do they get their resources, then?

! Moderator Note I concur with exchemist; give a proper citation of the paper and post at least the abstract. This is required by rule 2.7 excerpt: Links, pictures and videos in posts should be relevant to the discussion, and members should be able to participate in the discussion without clicking any links or watching any videos. Videos and pictures should be accompanied by enough text to set the tone for the discussion, and should not be posted alone. Users advertising commercial sites will be banned. Attached documents should be for support material only; material for discussion must be posted. Documents must also be accompanied by a summary, at minimum.

It's not the efficiency. Newton is a unit of force. You can get to energy if you are exerting a force through a distance, and thus doing work. Do this at some speed v and you can calculate a power. But you can't just say that something is exerting a force and directly get a power from it. The great pyramid at Giza has a mass of over 6 billion kg, and thus exerts a force of ~60 Giganewtons on the ground, but since nothing is moving there is no work done and the power is zero.

How are you getting from newtons of force to watts of power?

Gosh, I wish I had linked to this last week.

“with the building of ITER, we are building a machine that is almost there, in terms of being able to power itself and give off surplus electricity” The point is that ITER won’t produce electricity. It will be unable to do so. That will have to wait until the next device, which isn’t slated to be online for ~30 year…if there are no schedule slips for any reason. We aren’t “almost there.” We’re at least 30 years away, which has been the state of fusion for >50 years. No, you’ve missed the point. The problem is getting fusion to work at this scale. You’re just assuming things will go as planned and on schedule, which hasn’t been the state of affairs for pretty much the whole history of fusion efforts. edit to add: https://www.science.org/content/article/iter-fusion-project-take-least-6-years-longer-planned "The project was officially begun in 2006 with an estimated cost of €5 billion and date for the beginning of operations—or first plasma—in 2016." Now the estimate is first plasma in late 2025, according to the Wikipedia article. And the issue of cost overruns and who will pony up cash for an engineering prototype when that well runs dry is a separate problem.

So you can’t make any claims about how much electricity ITER will produce. It will be zero. Any claims about what ITER will do have to be taken with a grain of salt. Those are goals. Complex experiments rarely work as planned. As we saw in the other thread, producing more heat than you put in is not the same thing as self-sustaining. Why? Because you say so? Do any of the designs predict this? Once ITER has demonstrated what it needs to, you have to fund, finish designing and then build the next one. The EU DEMO, the next step, is scheduled to take decades before it’s up and running. (estimated in the 2050s, assuming everything goes right. IOW, this is not imminent) EU DEMO is being designed to produce 2 GW thermal and 750 MW electrical. So less than half of the thermal output. https://en.wikipedia.org/wiki/DEMOnstration_Power_Plant

How are they a secret of the Bible? Either they are mentioned - in which case you need to cite the passages - or they are not.

Define “almost there” and provide evidence of this claim, please. Considering that ITER is not designed to generate any electricity. https://www.iter.org/proj/inafewlines ITER will not capture the energy it produces as electricity

! Moderator Note A proper citation would be chapter and verse ! Moderator Note And this is the preaching you were told to steer clear of. A very genius person shouldn’t need to be told multiple times; I would expect they would understand the rules after on reading.

! Moderator Note If one is to take this as a topic of discussion and not preaching (because you’ve been warned about that), and that this isn’t a topic for science, by your own insistence, we’re left with religious sources…but you haven’t really provided any. The disappointingly vague introduction almost excuses the unserious responses and poor signal/noise. (which will be cleaned up) ! Moderator Note Angels (presumably) exist in religious literature and culture, which is the domain in which this can be discussed. Anyone who can't follow that limitation should not post.

Yes, it seems I had a spurious “kilo” in there. 250 W not 250 kW, but that was notation, not calculation 250 W *3600 sec/hr*10 hr is 9 Megajoules, so the result is correct I was conservative in my numbers, and the being in question wouldn’t be human. That was for context only - a roughly human-sized quadruped (to maximize area) that wasn’t warm-blooded should require less energy than a human. Mammal metabolism scales roughly somewhere between M^0.67 and M^0.75, so the size limit might be somewhat smaller, but still decidedly in the macroscopic realm, and the demand goes down if they aren’t warm-blooded, or if they are, they regulate to a lower temperature. Those are not energy-related objections. My point is simply that energy availability isn’t the restriction here.

1 food calorie is ~4.1 kilojoules. If you need 2000 food calories, then you need 8.2 Megajoules. A fair bit of that for a human is sustaining our warm-bloodedness If your solar insolation is 250 kw/m^2 for 10 hours, that’s 9 Mj/m^2. The energy isn’t the limit.

It’s being studied/considered https://news.miami.edu/stories/2021/12/are-black-holes-and-dark-matter-the-same.html https://www.quantamagazine.org/black-holes-from-the-big-bang-could-be-the-dark-matter-20200923/