MigL

The 'end of life' scenario of a Black Hole is complicated, as it is based on semi-classical/quantum assumptions by S Hawking and later D Page. Calculations suggest a Black Hole ( Schwarzschild ) to be a net emitter of radiation at the current CMB temperature, it would be about the mass of the moon. From this point, the BH's temperature will increase dramatically, and its size would shrink from millimeter size until radiation is being released explosively. The mass is no longer able to contain the radiation, as it did when the BH was much larger. The actual 'shedding' of the Event Horizon would happen at microscopic scales approaching Planck, but this would happen almost instantly, as temperature ( and output mass energy ) increase exponentially. The Wiki entry on Hawking radiation Hawking radiation - Wikipedia more specifically, the section on Black Hole evaporation has a good explanation with simple-to-follow math

Energy and mass are equivalent properties of a system. IOW, a Black Hole can radiate away massless but energetic photons and lose mass. When the remaining mass is no longer able to support an Event Horizon, and it can be quite a large mass, it explodes back into normal space-time, with a gamma ray burst. There is a problem with this scenario, and it's at the forefront of research. A certain property of Quantum Mechanics dictates that information must be preserved. Black Holes, in effect, swallow information and randomize it by re-emitting it as non-specific Hawking radiation and a final gamma ray burst. So we know we are missing vital knowledge about the process. This is likely because S Hawking's theory was a 'crude' combining of GR and QM; a self-consistent Quantum Gravity model is needed. ( and ther are questions as to whether that is even possible )

The most basic purpose of life, any life on any planet, is to reproduce. I can see generational starships spreading a race through an area of our galaxy, or even probes that deliver embryonic life to other star systems, but what is the purpose of your Von Neumann probes ? They can't gather and return information to the sender, as that would take twice as long as the journey to get here. So why would any advanced civilization undertake such a project that may return information outdated by millennia, or not return any at all. For any civilization to advance to a level of interstellar travel, they would need to use concepts like effort/benefit analysis, otherwise they would have made stupid decisions, and not advanced to such a level. And sorry, but sending probes that don't return information, or return it 10 000 years out of date, seems like a stupid undertaking to me. The second part of your post reminds me of the time travel problem ... "Time travel is impossible because no one, from a future where they have time travel, has ever been seen." For all you know, your UAPs might be from the future, instead of from other star systems; how would you differentiate between the two ? And why do you consider one choice more likely than the other ?

I didn't want to get in on this, simply because serious discussion lends 'credibility' to the UFO are aliens argument. There are many things that are inexplicable, and the vast majority are not even related to UAPs. And just as with the 'alien visitation' believers, there is an even larger group of people who are sure they know the reason for this larger set of unexplainable phenomena. You yourself, Moon, would call these people religious fanatics, and you'd be the last person to point out a need for scientific research to investigate God. The fact that something is currently inexplicable does not grant freedom to 'make up' a cause. And as with religion, this is my opinion. Given the physical limitations on travel between star systems, I really cannot understand the reasoning ( and expenditure of resources ) why aliens would visit us, play cat and mouse games, and anally probe a few hicks in the Southern US 😄 ( sorry, I had to throw that in ).

You're preaching to the choir. I suggest you fly to Moscow and tell Vlad to stop targeting the reactor in Zaporizhzhia, and the containment in Chernobyl with missiles, shells and bombs. Oh wait ... I forgot, some people don't follow the rules. Remember what Batman said "My parents taught me a different lesson ... dying for no reason at all. They showed me that the world only makes sense when you force it to."

Attraction is a mental phenomenon. Birth control pills are a hormonal modifier. A little knowledge dispels many rumors.

Viruses are kept around to study and develop vaccines and outbreak mitigation methods. Even if you get rid of all smallpox virus, there is no reason why a member of that strain couldn't mutate into something even more virulent than smallpox. Hope for the best, but be ready for the worst; IOW be prepared.

No feelings were hurt, and no need for apologies. I was in a 'mood' that day, for other reasons. Sometimes I get into a funk thinking I've outlived my usefulness in this forum, but I never feel bad about things said on an on-line forum. You guys aren't real, just imaginary anyway, right ?

The fact that you ignore my points make me feel you were just wasting time before also. Of course it is; it's in the thread title -why did Truman use the atomic bomb on Japan- The pChemical plant where I work makes and purifies liquid Phosphine. On a regular basis we may have up to 60 000 lbs of Phosphine at 700 psi, on site. That is considered a weapon of mass destruction, even by the FBI, who have been here to investigate our site after 9/11. What we consider weapons of mass destruction would have first been used in WW1, in the form of Chlorine and Phosgene gas attacks. It might also be relevant that certain battles of WW1, and even the Crimean war, regularly had 100 000 casualties; if not from munitions then from infections of wounds afterwards. even earlier when city states in Europe were besieged, flaming catapults may have killed half their inhabitants ( or plague-ridden rats, most of them ). In that historical context, would that have been considered use of WMDs? Or how about when Ghengis Kahn raided central Asian cities, killed most, enslaved the rest, and burned the city to the ground ? Does that make arrows and fire WMDs? If the taking of lives is immoral, Taking them to save economy and culture are also. I, and I'm sure many others ( even MSC ) don't consider taking the life of someone who is threatening the life of others, immoral. Fear is never a justification; an imminent threat is. There is a difference, and its usuaslly called self defense. Have I addressed all your points, or are you still wasting your time.

Aw, come on. Don't tell me you can't tell the difference between Eichmann saying "It was my job to put those Jews to death because we hate their kind.", and a cop saying "It was my job to shoot that person because he was about to kill another person.". President H Truman was trying to save American lives. You don't think that's a President's job ?

I think we can all agree that killing is immoral. I don't follow the reasoning where killing a few is more moral than killing many. And if so, how many ? And I find it strange that you think someone like President H Truman shouldn't value 100 000 American lives more than 100 000 enemy combatants. That is his job; to defend people he cares about. Oh, and I got 'pissy' like this because MSC commented about my morality, or lack thereof, not to simply be provocative.

This thread has devolved into an argument about 'morality', and 'mine is better than yours'. I don't need to justify my morality to anyone on a science forum; people dying are people dying, and and my morality says if you can save those you care about, you do what you need, up to and including nuclear weapons. Nuclear weapons are simply a better more efficient weapon for killing. So were knives and swords to people with sticks; did anyone complain about the morality of using them ? So were bows and arrows to people using knives; who complained about the morality of their use ? The same for guns, tanks and bomber planes.; why is it all of a sudden about 'morality' ? And why is it more moral to kill someone( or many ) with guns, or bombs, but not nuclear weapons, @MSC

Black Holes have entropy, and therefore, temperature, This temperature is inversely proportional to its size. A solar mass Black Hole has a temperature 60 Billionths of a degree K. All other Black Holes are even colder. That means almost all Black Holes larger than a solar mass are net absorbers of mass/energy ( the CMB is at 2.7O K ) I would think that this Black Hole involved in the collision is a relatively 'new' Black Hole that hasn't been very 'active' ( injesting mass/energy ). Maybe Mordred can shed some light on this; I believe it's in his 'back yard'. As Black Holes evaporate they get smaller and hotter, and radiate copious amounts of energetic radiation ( possibly encoding information ? ) before they lose their Event Horizon and explode back into normal space-time. This can only happen far in the future when the universe has cooled enough for stellar Black Holes to be net emitters of radiation, or, if primordial microscopic Black Holes ( formed in the high energy densities shortly after the Big Bang ) are reaching the end of their lives, None have ever been detected. My thinking has aklways been that no paticle can be constrained to a point, because that would imply ( By the Heisenberg Uncertainty Principle ) that its momentum ( and speed ) could be infinite, and it could escape the Black Hole. So I, and most people don't believe a central singularity is possible; it simply means our theory ( GR ) is not applicable at these energies and scales. I suppose this depends on your definition of 'theory' and 'hypothesis', but the theory does make some testable predictions.

Mordred is much more qualified to answer, but there is a difference between vacuum energy , and vacuum expectation value. My ( limited ) understanding is that while the concept of the VEV is a property of the vacuum which in Quantum field theory ( QED, QCD, Higgs ) governs virtual particles and condensation of fundamental masses, vacuum energy ( zero point or false zero ) is a property of the universe, and encompasses contributions made by virtual particles. The one place where the two 'meet up' is in regards to spontaneous symmetry breaking. Physicists are not like chemists ( no offence meant ). We are much more anal, and hate plugging numbers ( constants, fundamental or otherwise ) into equations. These numbers have to have a 'reason', otherwise we ask "Why that number ?", or have to invoke the observation selection effect ( anthropic principle ). So we try to derive these such numbers from 'first principles'. The usual method for vacuum energy is treating each point in space as a harmonic oscillator, summing over all such points and renormalizing the resultant infinity, usually with a suitable cut off, or ( as Sabine mentions ) that energy is a gauge condition where only differences are measurable. I believe there has been some research into using vacuum energy as 'effective mass' of the vacuum, or a field strength that 'resists' global curvature ( in GR ), to derive G from first principles ( like I said, we are anal 😄 ).

And a more, shall we say, controversial ( as always ) interpretation of vacuum energy

Really ? Sometimes they seem very appropriate for any geopolitics.

Here is a simple to follow calculation of the expected vacuum energy, and comparison to the observationally estimated vacuum energy which results in the 124 orders of magnitude 'vacuum catastrophe'. It also provides clarification about Cosmology, universal expansion and the Cosmological Principle.

There are different kinds of nuclear weapons; strategic, in the form of ICBMs and SLBMs, and tactical battlefield weapons of much smaller ( or single warhead ) yield. But all are weapons ( of a possible much larger scale ), so you may as well ask what would happen if say, NATO gave up its weapons ? I think V Putin's armies would be at the Atlantic European coast in a year ( assuming they can get their logistics in order ). If Taiwan dismantled their defenses, and the US wasn't willing to provide military support, China would start building a land bridge to Taiwan, to make them part of the mainland. How long would Israel last as if they discarded their weapons and relied on the good will of Syria, Iran, Lebanese Hezbollah and Hamas ? Because that is what you are proposing. And arguing that you don't mean conventional weapons, just nukes, is pointless. An army ( including tanks ) of 100 000 can be wiped out by a single hi-yield battlefield nuke, if your rogue opponent chooses to disregard the 'treaty' and keep their nukes. @MSC You may have misunderstood ( must be ADD at such a young age 😄 ) It is not that we are extorting and blackmailing these rogue states like N Korea and Iran not to develop nukes, rather, they are extorting/blackmailing ( usually ) the US, and demanding economic support as a condition of not developing nukes ( which they do anyway ). The reality is, in a 'perfect' world there are no bad actors, people who covet other's possessions/property/land, or people who crave wealth/power, and that is the only place where unilateral disarmament would work. That is not the world we live in. I wonder, if your child is being bullied at school, do you tell him/her " just go ahead and give the bully your lunch money, he/she will learn from your selfless act, and become a 'good' person too". How do you think that would work out, considering we now have punitive laws against bullying?

You guys are too old to be that naive; well intentioned, but naive. You ban handguns, yet criminals still get them. You ban nuclear weapons, yet rogue states still get them. Some people just don't abide by laws, that's why we call them criminals. Is V Putin abiding by international laws ? How about N Korea and Iran ? ( even Israel, Pakistan and India; not actually criminal, simply not signing on to any nuke banning treaty ) At best, you propose a system which ensures continued extortion/blackmail to keep them from developing nuclear weapons ( all the while continuing their development ).

The genie is out of the bottle, and it's too late for wishful thinking. The states that do have such weapons have a history of being provoked to the brink, and haven't used them since 1945. Even new nuclear powers like India, Pakistan and Israel. They are an almost known quantity. It's the unknown quantities like Iran and N Korea that make the equation hard to calculate.

What can I say ? I'm a complicated person. You mention Israel dropping a nuke on Iran, yet Israel has had nuclear weapons for about 30 years. They haven't used them yet. Would you be so confident that the same would hold true if Iran had them ?

Exactly. Even nuclear deterrence doesn't work with madmen dictators. Deterrence only works when both sides have something of value to lose. V Putin is arguably the richest man in the world; do you think he is 'mad' enough to lose that? Even KJU lives in the lap of luxury in N Korea; do you think he'd want to give that up ? The only ones I fear are the religious delusional nutbars running Iran, if they get nukes. They will use them, and Israel will respond; not proportionately either

There is a vast difference between what I have the stomach to do, and what should be done. Were I suddenly transported into President Truman's body, I may not have dropped nuclear weapons; but if I had lived his life, and experienced the horrors of that war, being responsible for all the people lost in the Pacific theater ( and those yet to come ), I certainly may have. I'll give you an ounce of T-Nitro-Toluene and an ounce of radioactive Cesium, and task you with transporting both, in your car, to the next city. With a little knowledge, you can provide shielding for the radiation; that's always been the biggest fear most people have, they can't see it and they don't understand it. Most people understand TNT perfectly well yet they don't know enough to be more afraid of it. Which do you think you should be more afraid of ? The danger is in how it is used.

Proportional response is highly over-rated. Deterrence of any particular action depends on the realization that the consequences could far outweigh any benefit. If I steal $100, and my only punishment is a $100 fine, I'm no worse off than I initially was, so I may as well attempt it.

Some people just see other people's ideas as damaging, and wish to silence them. Lesson learned ... stay off social media. That's where all the idiots are to be found.