MigL

An explosion has a radial direction. Parts of the 'exploding' material closer to the origin of the explosion would be moving towards the intermediate parts, while the furthest parts wouls be moving away from the intermediate parts. We observe ALL parts moving away from us, no matter which direction we look ( and so do observers on the other parts ) Even if the explosion was a 'surface' effect so that all parts are equidistant from the origin, we would still see 'voids' when looking towards the origin, or away from it; we see neither of these. IOW, the universe's 'explosion' is not consistent with observations, but expansion, as in increasing separations between parts of the universe, is. ( c'mon Airbrush, you've participated in enough of these discussions to know better about this, and some of your other claims )

There are also theories where space, and time, are emergent properties of 'something' more fundamental, as well as theories where spatial, and temporal, separations are inherent properties of the quantum particles themselves. The hard part is trying to build a model that is not only self-consistent, but also consistent with the large body of accumulated Physical evidence/observations. Imagination is cheap; unless you can satisfy the two constraints above, you have nothing. ( I haven't read the pdf file; maybe you do satisfy those constraints, and you have something, but unless you explain it here we'll never know )

Unfortunately they only generate microWatts, and would need to be in a backpack to power your cellphone. Much ado about nothing ... Not even 'good enough for Australia'. ( entertaining blog if you're into electronics )

Maybe if we reduce the situation to its simplest form without trying to find other 'connections' between the left and right parts of the EFEs ... Geodesics are basically a description of space-time curvature or geometry. A test mass falling towards mass M, will follow a geodesic which defines the local space-time geometry. A test mass falling towards mass M10 will follow a much different geodesic; one defining a different local geometry. So, I would guess mass ( and its equivalent energy ) has some hand in determining space-time geometry. For a more 'in-depth' explanation see here

Always wondered about that @exchemist NH3 in water solution becomes NH4+ and OH-, making the solution strongly basic. But pure Ammonia, by itself, is not basic, just a strong reducer ? I never did understand a Lewis acid as an electron pair acceptor. ( Grade 13 was a long time ago )

I can't add much to the mathematical discussion, but from a physical standpoint, the fact that gravity gravitates is what causes its non-linearity. If it were somehow possible to remove the energy-momentum components of an existing gravitational field/geometry, some part of that field/geometry would still exist, because its own energy density causes ( caused ? ) a part of the field/geometry. But that original gravitational field, or geometry, had to have been caused by a local energy-momentum distribution. I don't know about mathematical considerations, but physical considerations tell us local curvature has to be caused by something ( and from my understanding of De Sitter, so is global curvature ) because our universe is causal.

Expansion cannot be eternal, as John has pointed out, but time only begins to make sense once space-time geometry is evident, and that happened at the Planck time of 10-43 sec., about 13.8 Billion years ago. What was there before that time could have been 'eternal', or could have existed for a 'second'; such labels are meaningless since time, as we know it, did not exist yet. But it certainly was not the universe we know ( and may have been embedded in another universe; see Eternal Inflation ). Is that how you were going to elucidate ? No one has invoked a 'creator' or the 'supernatural'; just you.

You're gonna have to elaborate on that one also. My understanding is that De Sitter models an essentially flat universe, devoid of ordinary matter, where the dynamics are dominated by the Cosmological Constant/Dark Energy. IOW, there is a local energy that accounts for any deviation from absolute flatness.

pointless arguing with religion, Dim. "So let it be written; So let it be done."

No. That implies that, if you wind the expansion backwards in time, you come to an 'origin' point, IOW, expansion of the universe contradicts a universe that has existed forever. Based on the expansion constant, also known as Hubble's constant, we can say our observable universe started expanding about 13.8 Billion years ago. ( If you're going to discuss with scientists, like John, who actually know their sh*t, you really should 'brush up' on yours ) PS My apologies, Dim, for continuing along the tangent; never pass up an opportunity to educate.

Yeah ... OK. But I'm not the one who felt 'insulted'. And we obviously have different definitions of the word 'similar'. American hubris ...

Under Frederic Barbarossa, Emperor of the Holy Roman Empire, in the late 1100s. ( don't get me wrong, I'm not disagreeing with you, just presenting a differing perspective; I like historical discussions )

I'm aware of that. Some would consider the mid 400s as the end of the empire, when a Germanic warrior of the Roman army, Odacer, assumed the title of "king' after deposing a child emperor. He had full support from the Roman Senate, and he ruled in the Roman tradition. He even expanded the 'empire' by retaking Sicily from the Vandals, and Dalmatia ( Croatia ) as far as the Danube to defeat the Rugi. He was finally deposed in the late 400s by another 'barbarian', Theodoric, an Ostrogoth, who also took on Roman sensibilities in his rule. They may not have been officially 'emperors' before Charlemagne, and they may have been 'barbarians', but they became Roman 'kings' of a somewhat reduced western empire.

Because Germany's obligatory 2% of GDP is not paid to anyone, They could very well spend it all in Germany; buying from their own defense contractors, or on wages for their military. Even if they did meet their obligations to collective defense spending, that spending would not need to go to US defense contractors. Even an idiot like D Trump should know that, or did you think he meant Germany was going to cut the US a cheque for a few Billion ? You acknowledge that D Trump was confused, yet you seem to know that he meant they should pay for protection. D Trump said Germany failed to meet its obligations to NATO, and, in his confusion, said they should pay the US. You said Germany failed to meet their obligations ( I have also agreed ). I said "that sounds similar to what D Trump said'. Where am I wrong, and what are you so upset about ???

Would Olber's paradox work in a universe where light from extremely distant sources, is red-shifted, due to expansion, to undetectable levels ? Only if you also consider the "other things", John. ( I know, I know, off topic ... sorry )

Rome may have fallen, and sacked numerous times, but the Roman empire assimilated invaders to 'their ways' and flourished, under various guises, well until recent times. Most Germanic empires, up to the Habsbergs of the Austro-Hungarian Empire, fancied themselves as the Holy Roman Empire. It is no coincidence that Germanic leaders called themselves 'Kaiser' ( even Russian leaders were known as 'Tsars' ), a derivation of Caesar. See the works of E Gibbon, "The Decline and Fall of the Roman Empire".

You're squabbling over what D Trump doesn't say, just as you took offense to what I didn't say. The 'delinquent' payments are not owed to the US; they are owed to the collective defense of NATO. I would have thought You'd understand that. You do know about NATO's collective defense policy ? It is not comparable to rent or mortgage payments ( yes, I do know what delinquent means ); it is more like you, and every other American, paying their taxes for upkeep of public, collectively owned roads, while D Trump doesn't pay his fair share for the upkeep, but still gets to use the roads. Subtle difference, but different nonetheless. If Europe had kept up with their obligations to collective defense, they wouldn't have been caught with their pants down when V Putin invaded the Ukraine. Now Europeans can't supply Ukraine with weapons/ammunition as they frantically try to ramp up production and spending, while the US, who is trying to come to their rescue again, is plagued by internal political squabbles with regards to supplying aid to Ukraine. And if the Ukraine falls, how long before an emboldened V Putin puts NATO's collective defense at risk ?

My apologies; it wasn't meant to be insulting. The emojis were there because I've been called that in the past, on this forum. No, but those are the same reasons D Trump cited for wishing to pull out of NATO. And why I led with "That sounds like ..."; nothing else was implied.

You would think that with their combined economies, the EU would be more assertive on the World stage, but some member states are actively undermining the Union's influence. The same can be said for NATO. Witness Hungary, whose leader seems more aligned with Russia than European neighbors. Witness Turkey, who buys Russian equipment to operate within NATO, among other problems, such as with Greece and Sweden's acceptance. And what about Britain opting out of the EU, which, IIRC, you're in favor of, String Junky; does that not reduce the EU's influence to that of vassal to the US ? The EU has had , for a few years now, the opportunity to be on equal footing with the US, but many of its member states are 'full of themselves' and want to go it alone ( France ), some think they'd be better off on their own ( UK ), some don't give a damn ( Italy ), and all do way more trade/deals, and are then beholden to, dispicable economies like Russia and China. The only member state that seems to 'glue' them together is the country that nearly destroyed Europe in the last century ( Germany ). And then all these states ( and Canada too ! ) blame their failures on American hubris, as you now do. Liberals is the name of the political party, akin to Democrats. The other parties of note are Progressive Conservatives, also akin to Democrats ( thankfully we have no equivalent to Republicans ), and National Democratic Party, socialists who make promises they'll never have to keep because they'll never be in power. That's today's lesson in canadian politics. That sounds an awful lot like what D Trump said 6-7 years ago when he suggested pulling out of NATO, and more recently when he said he would let V Putin have Ukraine, and possibly the rest of Europe, unless they start paying their share. Careful, you might get called a 'Trumpet' 😄😄 . It is not a matter of America being altruistic in providing defense for Europe and the rest of the free World, but a matter of self interest. It is always better to deal with free states than the likes of Russia, china, and other unreasonable autocratic states. I'm not sure when 'populism' took on a different meaning, as it used to refer to the will of the people determining governance, not a few 'elites'. Unfortunately, like other institutions such as communism, fascism, and religion, it is easily corrupted. The best example would be the populism of the French Revolution, which took power from a few 'elites' and gave it to the common people. Fear mistrust, and insecurity ultimately led to the revolution 'eating itself' But back to the OP... The US exerts control over other countries, not militarily like Russia does, or military and economic coercion like China, but rather, through other countries' greed; America is still the largest spender in the world, and other countries want the benefits of America's spending power.

Gravity is what makes things weigh We anxiously await the OP to clarify what he wants to know about gravity. ( without the hand gesture emoji )

I appreciate what you're attempting to convey, String Junky, but you're playing fast and loose with statistics. Black population of the US is about 50 Million, or approx 15 %, so, while there is a great divide that needs addressing, it is not of the magnitude you indicate. IOW, you cannot have equal numbers of millionaires, because numbers of Blacks and non-Blacks are not equal. You don't include a source so I don't know which year the Forbes article gives data for. The Black population of the US was 36 Million 24 years ago, or approx 11% of total population. Per capita numbers/percentages would better illustrate the situation. As for Microsoft's numbers, I would guess they are close enough, and I applaud their transparency. Other companies should do the same. ( even though Bill turned out to be a bit of a misogynist )

No such thing as MS Office XP; maybe Office 2007 or 2010 ? There are a few public domain Office suites that read/write MS Office files at no cost, alternatively, MS Office 365 is subscription based ( pay when you need ).

Looks to be exactly the same as a piezo buzzer, except, instead of contacting a solid plate to make noise, it pushes droplets of water through a perforated plate ( as suggested by Swansont ). A simple circuit, where an oscillator switches a transistor to provide a voltage/current to the piezo element, can be adjusted with higher/lower drive voltage, and different oscillator frequency.

So far so good, CharonY. Or maybe, our politicians are a little more sensible than yours 😄

I wouldn't exactly call it a pop-sci myth. The Event Horizon is a condition of the space-time surrounding the collapsed mass-energy. At the Event Horizon, a mathematical condition is exceeded, but there is no actual physical structure. One can say that the space-time surrounding the collapsed object is the source of Hawking radiation, and you would be correct. You could say that the condition of the space-time is the source, or you could say the EH is the source, and you would still be correct. I've also read of many 'mechanisms' for Hawking radiation production, ranging from the virtual particle pair capture and emission ( as real ) which you described, to particles ( radiation ) tunneling through the EH, as if the EH was a real structure, and many other 'interpretational' mathematical models which give the same results. ( this is a Quantum Mechanical effect, after all ) What is certain is that BHs have entropy, and therefore must have a temperature. That temperature requires them to emit radiation characteristic of a black body at that temperature. Here are two differing 'interpretational' mechanisms for radiation production from a google search Hawking Particle Creation.pdf (brainmaster.com) 0409024.pdf (arxiv.org) Both are fairly understandable ( math light ) and don''t give me 'headaches' when reading them 🙂 .