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Physics, Astronomy & Cosmology / Re: What Is The Final Parsec Problem ?

« on: 06/01/2025 18:47:47 »

    When galaxies collide, their central supermassive black holes (SMBHs) should also eventually merge.
    However, as the SMBHs approach each other within about a parsec (3.26 light-years), the density of stars and gas in the galactic core becomes too low to effectively remove the energy and momentum needed for the final plunge and merger.
    This "energy loss problem" prevents the black holes from spiraling inward and merging within a reasonable timeframe.

So how do Black Holes merge then ?

The quote you give kind of says it.  To get closer, their kinetic energy must go somewhere, else, like Earth, it just keeps orbiting the sun without getting closer.

Thing is, the way this energy is dissipated is by flinging other matter away, giving that matter the orbital energy of the pair. Once the material is all gone, only new (not orbiting) material can contribute further to this process, and that takes a lot of time.

They will eventually merge, just all all planets will eventually fall into the sun given enough time and no external dissturbance.  Any pair of orbiting objects emits gravitational waves and that energy comes from kinetic energy.. Earth for instance emits GWs at the rate of about 200 watts, and the kinetic energy of Earth will run a pair of 100W light bulbs for an awfully long time.  The sun will swallow Earth before that has time to happen, but that's the fate of say Jupiter.

Likewise, all black hole binaries like the undoctored picture you took will eventually merge, but the universe is only 14 billion years old, nowhere near long enough for gravitational waves to do the job at a full parsec away.


Fun fact: Two sheep circling each other will emit Baaavitational waves.

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Complementary Medicine / Re: Can anyone recommend any insomnia support groups?

« on: 17/12/2024 15:11:24 »

Hi Neilep, this is a very old thread and I have just read the last page of posts- I have no intention of reading through the whole lot. That said, I have a suggestion that in all probability has previously been mentioned but I will try anyway. Have you ever tried counting sheep to address your insomnia problem?

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Physics, Astronomy & Cosmology / Re: Are Atoms Perpetual Motion Machines ?

« on: 30/10/2024 13:47:06 »

I am fairly sure the first law is sacrosanct and will never be broken. I can foresee the possibility of very limited cases where the second law does not hold- these will be highly contrived scenarios and I don't reckon any great usefulness will arise from these. Bottom line, I don't think future generations will find a significant way around these laws. Ewe may hold a different opinion but we won't fall out over it.

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Physics, Astronomy & Cosmology / Re: Are Atoms Perpetual Motion Machines ?

« on: 30/10/2024 09:10:25 »

Yep, repeal both the first and second laws of thermodynamics and the global energy problem is solved. On further deliberation repeal of either would do the job.

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Physics, Astronomy & Cosmology / Re: Are Atoms Perpetual Motion Machines ?

« on: 29/10/2024 22:50:30 »

Maybe  in the future, our descendants will be able to harness the power of this motion to make a perpetual machine ?

Only if they repeal the most fundamental laws of physics and common sense. But I wouldn't put that past Donald Trump and the US Supreme Court..

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Physics, Astronomy & Cosmology / Re: Are Atoms Perpetual Motion Machines ?

« on: 29/10/2024 19:44:03 »

By eliminating all losses such as friction it is, in principle, possible to make a contraption that would exhibit perpetual motion. It would, however,  be totally impossible to harvest any energy from this.

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Physics, Astronomy & Cosmology / Re: Is it Just Hadrons that The Large Hadron Collider...collides ?

« on: 29/10/2024 19:27:09 »

What is so special about Hadrons ?

They're made of smaller things.

Are there other particles on the menu to be collided too ?

For the most part, no. Electrons for instance are not thus accelerated, although it seems capable of it.

How do they store the particles ?....are they kept in a test tube or something ?

Everything is made of them, so it is simply a matter of isolating them (from Hydrogen say) and then sending em down the pipe.

How many particles are fired at one time ?

Hundreds of billions (of protons, which are hadrons) per beam, and multiple beams.  I've heard a thousand times that figure, so not sure if there are thousands of beams or they can make some beams more dense.

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Physics, Astronomy & Cosmology / Re: Are Atoms Perpetual Motion Machines ?

« on: 29/10/2024 18:12:28 »

Where does the energy come from ?

It was always there since the atom was made.

2: Does this make atoms (et al) Perpetual Motion Machines ?

No. A PMM is something from which indefinite work can be extracted, at however small a rate. One cannot extract indefinite energy from the motion of an atom.

9

Physiology & Medicine / Re: What Happens To White Cells After They Have Dealt With An Infection ?

« on: 29/10/2024 17:15:32 »

Blood cells (of any type) are fairly short lived, so the white cell counts go down by attrition and lack of many more being produced after their need is gone.  The counts return to normal levels around 5-25 days after infection is cleared, depending on the sort of infection involved.

Red cells might live 4 months. White cells have a life expectancy of only a few days, so if you stop making them in abnormal quantities, their numbers quickly decrease to normal levels.

I have given a unit of red blood cells, and that has the longest wait time before I'm allowed to donate again. Giving whole blood, plasma, platelets, all have shorter wait times.
I've not heard of giving white cells, but I know that early in the covid days before the vaccines came out, whole blood from a person who had recently gotten over a covid infection was in serious demand to serve as a treatment for the more dire cases.

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Physics, Astronomy & Cosmology / Re: Are Atoms Perpetual Motion Machines ?

« on: 29/10/2024 16:46:56 »

It makes them perpetual, but not machines because any model of an atom that invokes movement must require that movement to be essentially random. Heisenberg rules!

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Physics, Astronomy & Cosmology / Re: Why does Quantum Stuff Still Move At Absolute Zero ?

« on: 29/10/2024 15:30:02 »

Carnot efficiency is η = 1 - Tc/Th.

So if the theoretical efficiency of a heat engine is 100%, Tc must be zero. There's the definition!

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Physics, Astronomy & Cosmology / Re: Why does Quantum Stuff Still Move At Absolute Zero ?

« on: 19/10/2024 13:30:52 »

Hi.

    I'm fairly sure we've had some other threads discussing temperature and the sorts of issue that @neilep has raised.

This is a short summary of how I see the current situation.   Note that  (i)  I'm only one person and don't claim any special expertise in this field of study,    (ii)  It is apparent that our notion of temperature is changing, so that whatever is said here will probably change again in a few years.


Summary:

    Historically temperature was understood in many different ways.   One simple approach is that temperature was the thing you measure when you stick a thermometer into something.   Problems with this approach were too numerous to mention.  For example, how do you build a reliable thermometer?   Sticking a thermometer into some liquid is reasonably easy but sticking a thermometer into some solid is often impossible.  How do you ensure you're getting good thermal contact etc?      In the very old days, some things just didn't have a temperature if you couldn't stick a thermometer into it.
     At a later time,  let's say between 1848  (when Lord Kelvin was developing his Kelvin scale) and 2019 (when the weights and measures commitee redefined temperature) it was quite popular to define and consider temperature using a thermodynamic approach.   That actually worked quite well.
    Since May 2019,  international agreement has been to define temperature based on a Kinetic Theory approach.   That's not my fault, it's just what was done by the weights and measures committee and whoever establishes the SI units for Science.   They wanted to improve our definition and undertstanding of temperature and it was thought that basing temperature on this theoretical framework would make it more objective and absolute.   Just to be clear about this - the modern Kelvin scale is NOT the one that Lord Kelvin developed, we kept the name but ditched most of the notions that Lord Kelvin used.

     We have a great model and good understanding for this kinetic theory approach  IF  the substance is an ideal gas.   The trouble is that most things are NOT ideal gases.   We have a few other reasonable classical models for other things but by no means do we have a good classical model for the microscopic behaviour of everything.
     One very important thing to note is that the sort of microscopic mechanics that is used in these models and that the weights and measures committee have declared we MUST use,  are based on classical mechanics and NOT quantum mechanics.    This is a problem because some things are evidently quantum mechanical but we never-the-less have to do some translation into an equivalent classical system when we assign a temperature to that system.   As mentioned already, we have some good classical microscopic models for some things but sometimes we just do not have any such model that we can use.   Overall, the attempt by the weights and measures committee to make temperature more objective and absolute have caused as many problems as they may have hoped to solve.

   Reference:   Spend the time reading Wikipedia's entry for "temperature" and you'll get some idea of how temperature has been redefined.    https://en.wikipedia.org/wiki/Temperature.     That Wikipedia entry has been edited and adjusted since the last time I looked at it about 1 year ago.   As mentioned, it is very likely to keep changing in the near future.


   Anyway, one answer or reply we can offer to the OP is the following:
You just aren't allowed to use a quantum mechanical model for the substance you are trying to assign a temperature to.   You would HAVE to translate the behaviour of your substance into some classical microscopic model.    What you'll then end up with is a temperature that says something about the average kinetic energy per particle, even if it's a total abstraction to imagine that anything like individual classical particles could be found in this substance or thing.
    In your case, despite your assertion that this thing has temperature 0 k, it probably won't be and can't be 0 k.  You probably can't obtain an official temperature of precisely 0 Kelvin unless the zero point energy of your thing actually is 0 and the corresponding classical model would have particles with 0 kinetic energy.

Best Wishes.

(Last edit to fix some spelling errors).

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Physics, Astronomy & Cosmology / Re: Why does Quantum Stuff Still Move At Absolute Zero ?

« on: 19/10/2024 10:59:58 »

Does the uncertainty principle apply to low temperatures like this or is it strictly position and momentum?

If an object doesn't move, you know its position and momentum exactly. This is forbidden by the indeterminacy principle, regardless of its kinetic energy.

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Physics, Astronomy & Cosmology / Re: Why does Quantum Stuff Still Move At Absolute Zero ?

« on: 19/10/2024 08:55:48 »

Surely it would still have mass at 0deg k and hence the energy of e=m(csq)  Does the uncertainty principle apply to low temperatures like this or is it strictly position and momentum?

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Physics, Astronomy & Cosmology / Re: Why does Quantum Stuff Still Move At Absolute Zero ?

« on: 18/10/2024 20:26:55 »

One thing I noticed about your questions is that absolute zero is a theoretical limit. There's a reason no experiment has been done at absolute zero or 0 deg K.

It has to do with the so-called Planck energy of quantum particles; none of these is ever at 0 deg K, because then it would have no rest energy or ground state. It wouldn't be a particle any more.

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Plant Sciences, Zoology & Evolution / Re: How Do Bees Say That The Source Of Food Is Now Empty ? Or Don't They ?

« on: 22/05/2024 23:22:10 »

They have to start somewhere, so the first job is to scout around for food. If you find some, you tell your chums where it is so they save energy by literally making a bee line to it.

Whilst the food is worth collecting, each returning bee then repeats the location. This is necessary because they navigate by the sun, so the coordinates change as the day progresses.

If a bee judges the source to be exhausted, she won't repeat the location but will scout for another source and the process starts again.

Apart from the moving coordinates, bee navigation is very similar to aircraft traffic control. Bees fly out of the hive to a fixed marker "beacon"  then set off scouting or collecting as instructed. On returning, they fly to the beacon then wait for ordered approach and debrief instructions from a couple of controllers at the hive entrance. Final approach appears to be "instrument" rather than "visual" which is why you shouldn't move a hive when they are working - they can't find their way back from the beacon if the door moved more than a meter or so since they left the hive!

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Geology, Palaeontology & Archaeology / Re: How Old is Soil ?

« on: 21/05/2024 08:00:40 »

...and if you keep digging down, you will find electric cables, drains, and, way down deep, trains. Never trust an archaeologist.

But if you estimate between 0.2 and 1 millimeter per year, depending on the nature of the soil, you won't be far off.

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Geology, Palaeontology & Archaeology / Re: How Old is Soil ?

« on: 20/05/2024 15:56:14 »

I doubt it will have an age as such, it must surely be a recipe that's had ingredients added to it and modified over millennia. Freshly fallen biomass, rotted biomass, constituent parts of biomass, large grains of sand, smaller grains of sand, dust, each evolved from the previous stage.

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Plant Sciences, Zoology & Evolution / Re: Do Fish Salivate ?

« on: 17/05/2024 19:49:23 »

Whales being mammals almost certainly do but fish?, I don't know. By a statement in your question we now know that sheep salivate, much as I suspect is the case for all mammals. Then again i'm just a lowly retired engineer, not a biologist and I replied as no one else had and i'm bored. And I enjoy these ovine onslaughts.

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Physics, Astronomy & Cosmology / Re: Where are the round rocks on Mars ?

« on: 17/05/2024 13:20:07 »

They probably never existed, or haven't yet evolved.

Rocks tend to fracture with straight edges. You need the erosive action of grit-laden water or wind to polish them into smooth shapes, and Mars seems somewhat deficient in both.

The alternative source of mineral rotundity can be a volcanic eruption of liquid that freezes slowly as it descends through a viscous atmosphere. but again Mars isn't the best place to manufacture lead shot by that traditional process.   

Umpteen years ago the New Scientist published a question about the distribution of flat stones on a seashore. My 6-year-old son pointed out that all the good ones will have been thrown into the sea by small boys, so you won't find many above the high water mark. Extrapolating from that wisdom, and from the Apollo program of exporting human stupidity to other planets, I think you might find round rocks inside the so-called craters that form the Mars crazy golf course.