MigL

Just read a story today that the author of a magazine article was offended by the naming of 'Tomahawk' cruise missiles in the strike on the Syrian airfield. Just imagine how she'll feel when they go in with Chinook, Kiowa, Iroquois and Apache helicopters. Sometimes you just gotta laugh.

Again, it is a MODEL, which, if applied correctly and in the appropriate circumstances, can make valid predictions about the universe we live in. NOT that the universe is necessarily a hologram ( as Strange has pointed out ). Something simple that we are all familiar with is light. Consider the wave model of light, when applied correctly, it makes all sorts of valuable predictions. But when applied incorrectly, such as with the photoelectric effect, it gives predictions which don't jive with observations. The particle model of light does work with the photoelectric effect, but doesn't make valid predictions in cases like diffraction. So what is light, a wave, a particle, both, or neither ? Don't confuse reality with the model used to describe it.

My impression was that Hawking radiation is a frame dependent effect, similar to Unruh radiation. It is apparent to the faraway observer, but disappears for the local frame of the infalling observer, who is in unaccelerated free-fall. However being stationary just outside the event horizon means an accelerated frame, and so there would be radiation ? I'm not convinced myself and will have to do some research.

It is simply a model that attempts to describe some of the fundamental qualities of the universe. In some circumstances the universe can be 'described' as a hologram with all of its information encoded on the lower dimensional surface of its boundary.

Even cleaning the sword, I would hope nitrile or neoprene gloves were used. HF is pretty nasty. It may not necessarily burn, but is absorbed, and can affect your bones.

Quite a few of us on this forum CAN follow the math, ZZ. What's more,, we understand the math and don't try to 'hide' behind it. First you claim there are no tidal effects within an event horizon ( again, its in black and white in posts #6 and #8 ), and then post a bunch of simplistic math to 'prove' that tidal effects are related to EH size. Which was our claim to begin with. We don't claim that there is a preferred viewpoint, that only the far-away observer's frame is significant, and that Alice will never know what happens to Bob. Bob's frame of reference is equally valid, and he WILL know what is happening as he crosses the EH on his way to the only event in his future, the meeting with the ( possible ) singularity. The two views cannot be contradictory, and can be explained by considering the signal reaching Alice from the infalling Bob. Incidentally, you don't win arguments by down-voting your opponent. That just makes you a sore loser. And I find it amusing that you have the gall to complain when others do the same to you.

Yes, I just re-read your post #6, and again in #8. No reference to size of the EH at all. Do you have selective memory ???

Sure, and your claim was that it occurs OUTSIDE the event horizon, while everyone else said it depends on the mass of the BH. Or do I need to quote you ?

I have had a copy of Dragon's Egg for a long time Swansont, as far as I know he is the only author. Also read another novel by him ( which I didn't find as interesting ), that involved a two planet system with a 'waterfall' from one planet to the other; I don't recall the title.

Math is fine ZZ, but the mathematical model has to be judiciously applied to the situation, otherwise it leads to non-sensical results like dimensionless points of infinite density. So while its true no outside observer will ever know Bob's fate once he reaches the event horizon, Bob will definitely know.

Are you familiar with Fermat's principle of least time ( for massless particles ), and the more general principle of least action by De Maupertius? It forms the basis of modern ( Lagrangian and Hamiltonian ) mechanics and even GR.

The answer to problem #3 is meaningless. There are no such things as stellar sized BHs with the mass of the Sun, as they could not possibly undergo gravitational collapse. They cannot even form neutron stars and are destined to be dwarfs in their senior years. Most galactic center BHs consist of millions, if not billions, of solar masses, and you could easily pass right through the event horizon without even noticing it. The fact that an outside observer would never see this does not change your reality and future meeting with the ( possible ) singularity. An excellent, non-mathematical reference is Kip Thorne's Black Holes and Time Warps.

The event horizon is a mathematical construct. There is nothing there. It is simply the radius at which escape velocity equals c . Gravity acts no different on one side of it than the other. A simple explanation for the 'direction' dilemma is to look at what happens to light cones as you cross the event horizon and approach the singularity. In effect, unless you can move faster than light, all POSSIBLE directions lead to the singularity. Edit : Sorry cross posted with J.C.

All that aside, his post was an excellent tribute to Robert L Foreward, writer of Dragon's Egg, one of my favorite sci-fi novels.

Again, there are NO other directions. The only POSSIBLE direction leads to the 'future', which is the singularity. And it is possible to have tidal forces in one direction. A simple way to look at it is when the gravitational differential across 6 ft is large enough to give a measurable difference, you will feel a 'tearing' force between your head and feet.

There is no difference in the way a BH acts gravitationally from an equivalent mass which is not a BH. Tidal forces exist within the event horizon. As a matter of fact, for a galactic center BH ( millions of solar masses ), the density required for gravitational collapse is equivalent to that of water, and you would not feel any tidal effect until you've passed through the event horizon and are well on your way to the ( possible ) singularity. What 'all possible paths lead to the singularity' means is that most paths are impossible once having passed the event horizon. The only available ( possible ) path left, leads to the singularity, and is usually stated as the only destination in your future is the singularity.

I am Canadian also, and the US could do much worse than copying our system, as it seems to work reasonably well. It does have its problems however... Doctors are paid by the 'system', and as a result are capped at a specific value. This has the double whammy of the best doctors leaving for the US where they can earn large, and the rest only taking so many patients to reach that cap. As a result we have doctor shortages in Hospitals resulting in long wait times for surgeries and difficulty finding family doctors. But at least EVERYONE has coverage ! I've said this before, and I repeat, for a rich country like the US, not to have a viable universal health care system is a shame and an embarrassement. Maybe having one would 'make America great again'.

Until now, I really thought I was funny... There goes my dream of doing stand-up.

Not just failed states either. How has V Putin become the richest man in the world ( estimated at up to 200 Bill ) ? And if you're going to consider the Government a partner, should it not also be liable for 50% of your losses ?

I thought it was Australian. And yes, I know what you mean Velocity_Boy, it only sounds good when spoken by women. ( your efforts are greatly appreciated, Zapatos )

And, this being a discussion forum... What do you wish to discuss ?

Not having read the Columbia article, what I get from CharonY's post is that media is, for the most part, SLIGHTLY left-leaning, while a small section of it is STRONGLY right leaning. No judgement on the ideologies, but that's no surprise to anyone. Remember the good old days when W Cronkite just presented the news without the political opinion.

Interesting but kind of misleading. How does one estimate the size of elementary particles ? You can get a 'scaling' factor based on their energy equivalence, but to assign a size other than 'point-like', you have to assume that they're made of something, and can be split into smaller pieces. But then electrons, neutrinos and quarks wouldn't be elementary, would they ?

I haven't looked up Political/Campaign Financing acts and legislation but I would guess that rules were significantly watered down in the 60s and 70s. It would be extremely hard for any politician, who gets financial contributions from wealthy people/corporations to then bring in such a level of taxation on those supporters. It would most likely be political suicide. The only way higher taxation on the wealthy could be realized is to stop the wealthy from 'buying' the government THEY want.

Have to agree with Zapatos, like and trust the Russian people, ddislike and distrust V Putin. As to the OP, D Trump better not set his sights on Canada. Remember how we 'smoked' you guys last time, 205 yrs ago ? ( what do you mean, we have NO armed forces and the longest undefended border in the world )