> If, on the other hand, he were connected to your "corporate peon" role, you could switch him on and off at the... drop of a hat. In fact, he could give you that hat when you get hired, already connected to everyone else in your office. And if you leave that job, you both burn that hat, and he gives one just like it to the next guy.
sounds like good old corporate email/network/IM account.
...which does not integrate at all into the employee's existing social tools. Separate accounts. Separate servers. All managed by the company and not the employee. If you have separate accounts for just work and real life, that's manageable. What happens if you also need separate accounts for church/temple/whatever, kids' sports leagues, civic societies, multiple circles of friends from high school, college, previous jobs, and the like?
It explodes beyond the ability of a human to maintain, and user names and passwords start getting reused.
I already have three separate e-mail addresses just at work, and that's a pain to deal with. I have two different personal e-mail accounts, so the recruiter spam doesn't drown out actual friend communication. I don't necessarily want Apple or Google or Microsoft connecting all those for their own nefarious purposes, but nor do I want to be burdened by the weight of my own requirements.
in the movie "Aviator" there is a scene where PanAm almost successfully gets monopoly on international flights. Watching it i could feel only "WTF?". The same way we'd be feeling couple decades later about monopolies that weak [in particular to the influence of industry] governments at all levels have been granting to telcos.
>I'm not even sure domain knowledge is important for a CEO of a company that size: once you become a $50 billion plus company, you don't have time to get involved with the details of the business.
Steve Jobs and CEOs in-between kind of make a counter-example.
Read the biographies of Steve and Steve; Jobs was not an expert, but was familiar with technology of that era. His father taught him electronics, and Jobs was working at Atari as an technician.
"39 explosions for the purpose of geological exploration (trying to find new natural gas deposits by studying seismic waves produced by small nuclear explosions)"
when in US the ITAR still applies AFAIK - getting any access to or knowledge transfer from ITAR project to non-US person, etc... Looks like starting from 1K plegde - invitation to test fire the engine - may run afoul of it.
I don't know. When I was in university we had similar projects going on (scratch-fabricated hybrid rocket motors, not aerospikes though) and I know there were non-citizen students participating. Didn't seem to be a problem.
I think the issue would be that they intend this engine to be the upper stage of a satellite launch platform. ITAR kicks in when you get up to that capability I believe.
Can ITAR apply to open source projects? i.e. if someone starts an open source rocket engine project not in the US, are people based in the US allowed to contribute in any way without running afoul of ITAR?
not sure what connection to Bitcoin here. The guy behaved like, for example, the mayor of San Diego (that mayor).
Different age, different business ... Would it warrant "This is What it's Like to Be a Woman in a city administration"?
>The event horizon is the "point of no return" beyond which gravity is inescapable.
the event horizon is frequently treated as "uncrossable" from inside to outside which is really different from "inescapable". The later means that whatever speed you have on or below the event horizon, you can't reach infinity. The former is just an impression by an outside observer because in his observation the time has stopped on the event horizon, while a stone thrown up from below the event horizon would cross the event horizon just fine on the way up and on the way down and would return back down successfully in its proper time (the point of "inescapability" is that the stone would always return). While above the horizon, the stone can interact with other stuff there and result of this interaction can be observed outside (doesn't mean on practice by us today or tomorrow :).
Many models seems to treat the event horizon as "uncrossable". For example quantum information disappearance - matter goes in, evaporates as Hawking. Yet, just for example, when Hawking radiation decreases the mass of the black hole it causes the shrink of the event horizon and thus whatever "stones"/photons on their way up were stuck (for external observer) in the stopped time of the horizon become free - doesn't mean though that we can observe them on practice as getting out of that gravitational well does take time (again in our time) and redshifts them into oblivion. Like proverbial "the check is in the mail". It is the reason why we can't really observe Hawking radiation until we develop technology to observe light with
extremely long wavelength and i just don't have the numbers right now on whether 13B years is enough for the radiation originating right above the event horizon to get out of that well and reach the interstellar space.
> while a stone thrown up from below the event horizon would cross the event horizon just fine on the way up and on the way down and would return back down successfully in its proper time
This doesn't agree with my understanding of GR. A stone "thrown up" from within a black hole interior cannot cross the event horizon in any reference frame - it cannot even get closer to it.
Look at the future light cones within the black hole interior, e.g. in the illustration at http://en.wikipedia.org/wiki/Eddington–Finkelstein_coordinat.... The future light cone of every event within the EH is skewed so far that even light rays directed outwards are drawn closer to the singularity.
the event horizon - Schwarzschild radius - is defined by the specific value of gravitational potential (escape speed equals speed of light) while, given the black hole mass large enough, the gravitational force at the Schwarzschild radius can be as small as we'd like it to be. The various local effects like time dilation, light path curving, etc... are defined by the value of gravitation force, not gravitational potential. The potential defines the fact that anything originating at or below the horizon would never escape completely the gravitational field, i.e. never reach the infinity.
The Schwarzschild radius of the mass of the observable Universe is 10B light years. So, several billions years ago, when observable Universe had 10B radius, it would be a black hole (though i think that in less expanded space of the earlier Universe the constants like "c" had different values and thus that Schwarzschild radius was less). We can imagine it in another way - increase 125 times (the observable Universe has 40+B light years radius) the amount of matter, ie. galaxies, stars, etc... inside the 10B radius ball around us, and you'd get the black hole with 10B light years Schwarzschild radius (and i don't think we would ever notice the change - only with time the galaxies's movement will be affected). Obviously, the gravitational field on the surface of that imaginary 10B radius sphere and inside it would increase somewhat (like 125 times on the surface, 125 times 0 pretty much 0) - not even close though to any values to affect space curvature or to prevent anything from crossing it from inside. Of course, anything that would cross it from inside would return back eventually.
> the event horizon - Schwarzschild radius - is defined by the specific value of gravitational potential (escape speed equals speed of light)
The Schwarzschild radius does have the property that, if you plug it into the classical equation for escape velocity, you get the speed of light. That doesn't mean arbitrary classical analogies (like the "thrown stone" example) hold.
In particular, consider that you can escape the earth while never achieving escape velocity. Just keep firing your rockets to counteract gravity. But if this were possible with black holes, then they would not be very interesting!
> The various local effects like time dilation, light path curving, etc... are defined by the value of gravitation force, not gravitational potential.
These are not local effects! Locally, there is no time dilation, and no curvature of light. I see my watch tick at the same rate, no matter where I am, because my watch and my eyes are in the same local reference frame.
In order to see effects like time dilation or curvature of light, you must compare events separated in spacetime. For example, we can look at the paths of light emitted by distant stars. And since the light had to get to our eyes, we have to account for the entirety of the path that it took. So the time dilation I observe for an event depends on the entirety of spacetime along the path from the event to me, not just the local curvature for the event.
In mathematical language, if you want to move a vector from one point to another on a curved manifold, you can't just specify the start and end point. The path you take affects the resulting vector.
> The potential defines the fact that anything originating at or below the horizon would never escape completely the gravitational field, i.e. never reach the infinity.
So objects originating outside the event horizon reach infinity in a finite time? Huh?
given the black hole mass large enough, the gravitational force at the Schwarzschild radius can be as small as we'd like it to be
No, it can't; the "acceleration due to gravity", which is the acceleration required to "hover" at a constant altitude above the horizon, diverges as the horizon is approached.
What can be made as small as desired by making the hole's mass large enough is tidal gravity at the horizon.
several billions years ago, when observable Universe had 10B radius, it would be a black hole
No, it wouldn't. A black hole is a stationary spacetime. The spacetime of the universe is not stationary. The spacetime model that describes the universe is very different from the spacetime model that describes a black hole; the fact that you can plug the mass of the observable universe into the Schwarzschild radius formula and get a number out does not mean that number has any physical meaning for the universe.
>No, it wouldn't. A black hole is a stationary spacetime. The spacetime of the universe is not stationary. The spacetime model that describes the universe is very different from the spacetime model that describes a black hole
exactly. There is no stationary spacetime in our Universe. Black hole is pretty artificial model where pure mathematical artifacts of singularity at the horizon is taken for the real thing.
> the fact that you can plug the mass of the observable universe into the Schwarzschild radius formula and get a number out does not mean that number has any physical meaning for the universe.
Taking a big chunk of space and calculating escape speed from its gravitational field - how is that not a physical meaning? At what specific size of the chunk you think it becomes not meaningful?
The universe as a whole is not stationary, nor even close to being so; but portions of the universe are very close to being stationary. The solar system, for example. Black holes do not have to be exactly stationary; if they are as close to being stationary as the solar system, that's plenty close enough.
Black hole is pretty artificial model
The exactly spherically symmetric solution is an idealization, yes; but there are plenty of numerical simulations that show that non-symmetric spacetimes still form event horizons.
where pure mathematical artifacts of singularity at the horizon is taken for the real thing.
There is no physical singularity at the horizon. Some coordinate charts have a coordinate singularity at the horizon, but that's easily fixed by just using a different coordinate chart. The only physical singularity is at r = 0.
Taking a big chunk of space and calculating escape speed from its gravitational field
Escape to where? You can't escape from the universe as a whole. The concept of "escape speed" has no meaning for the universe as a whole.
>Escape to where? You can't escape from the universe as a whole. The concept of "escape speed" has no meaning for the universe as a whole.
take a 1B light years radius ball, populate it with density of our Milky Way - that ball will have 1B Schwarzschild radius. Calculation of gravitational potential (escape speed) from it to the rest of the Universe makes sense, doesn't it?. And due to this gravitational potential it will be bona fide black hole from the point of view of the rest of the Universe.
Nor mine. You're correct, any object in the interior of the hole, even one that is moving radially outward at the speed of light, gets closer to the singularity (i.e., its r coordinate decreases) with time, which means it can't get closer to the horizon (that would require increasing r).
Technically speaking, in classical GR if you begin at any point inside the event horizon of a black hole, your entire future light cone is also contained within the event horizon. That means that a black hole event horizon truly is "uncrossable" (as you phrase it), not just "inescapable". (The Newtonian analogy of escape velocities doesn't really capture the details of GR in this case.)
50 years ago plane looks more capable as VTOL than F-35. Modern powerful engines allow to drive the fans from the compressor shaft - as F-35 shows - and that would fix the main geometry issue with jet engine placement in XV-5A where fans were driven from jet exhaust.
We have created sufficient variety of failed VTOL plane concepts that there are certainly a number of types you've never seen. It is a recurrent trend - every engineering team thinks they have an answer which puts a novel spin on things and will fix them once and for all - and then it turns to shit.
View the 'wheel of shame', as it's known in aeronautical engineering circles:
several years ago spent a bunch of time going through the wheel, and in my view XV-5A and Bell X-22 were pretty good planes - there was nothing really wrong with them, and definitely not a "shame". Given the half-century improvements in hardware/electronics/aeronautical science i think if built today they would be much better than F-35 and V-22.
we can have serious hearing in Senate on BTC with outcome rules [almost] killing or seriously affecting it. Having a hearing and SEC/FBI enforcement on Doge? With Doge as a witness. Put you paw on the Bible and repeat after me ...
sounds like good old corporate email/network/IM account.