. . . R_S=2MG/c²

• Small black holes, their mass are like mass of a hill, cca. 10¹² kg.
• Medium black holes, their mass are some times of our Sun, cca. 10³¹ kg.
• Giant black holes, their mass are some million times of our Sun, cca. 10³⁹ kg.

To become more familiar with black holes, let's determine radius R₁, where orbiting a spacecraft one turn needs punctually 1 year. ( Formula can derived from Kepler-laws (**) )

If we want photons to turn back to our orbiting rout and not to the infinite, we have to compress black hole a little bit. The smaller the hole, the smaller the rate we have to compress it. Giant black hole needs 20 mill.km compression, but a medium one needs only 1 millimeter. This emphasises the importance of gravity acceleration near surface! It is not too high in case of giant hole ( "only" 30000 m/s² ), but extremely high in case of small one (30*10³⁰ m/s²). A compering number: g= 274 m/s² on surface of Sun. (On the pictures the compressed radii are marked with R₀. )

Some years ago BBC showed a video on life of Stephen Hawking, well known researcher of black holes. Though best physicians were listed as adviser, there were disturbing or even mistaken statements with connection of BHs. Let's analyse some of them:

1. Photons are drawn back onto surface of BH by very strong gravitation.
2. In the film was shown an "event horizon" around a BH, pretty far from it. Inner part was marked as violet mist.
3. A spacecraft which enter event horizon can never escape.
4. Astronaut will never see the outer space, spacecraft or other astronauts.
5. It would take 4 weeks for him to fall from event horizon to surface of BH.
6. At half of falling time (2 weeks) his body will be lengthen.
7. BH swallows everything nearby it...
8. But gamma photons can escape with aid of tunnel effect.
9. There are cool BHs, their temperatures are very near to absolute zero.

ad 1.) "Photons are drawn back ... " really means that speed of light changes, decreases. This is the "ballistic emitter theory of light" created by Ritz in 1904 - and denied by de-Sitter at the same year. Speed of light is constant (c), says Theory of Relativity too. But gravity influenceses its wave-length - and the simplest explanation that it influenceses its speed. So BHs and other phenomenons show that speed of light depends on gravity. The stronger the gravity the lower the speed of light. (See fig. 2)

ad 2.) I admit, a "violet mist" is just good to show somehow "event horizon" , but there is no such a thing around BH ! Yes, maybe there is a "barrier" for photons emitting just from surface, but this is no barrier for a photons emitted one millimeter higher or one millimeter lower. And it is no barrier for spacecraft or astronauts. There is no physical law or reason to create a real barrier around BHs. Gravity acceleration is quite small there:

g_1(small) = 5*10^-9 m/s², . . g_1(medium) = 0.01 m/s², . . g_1(giant) = 4.7 m/s².

ad 3.) A spacecraft can easily move to and fro across event horizon with aid of its relatively weak rocket-engine and, finally can left this area using as few fuel as low the value of gravity is there. And no change in its rout if a heavenly body crosses this theoretic barrier: it will continue its elliptic or hyperbolic way without any abashment.

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ad 4.) The statement is simply untrue: astronaut inside will see astronauts outside, as he will not be yet on the surface. He will see stars too. Will be light-beams curved, if astronaut is on his half-way? Hardly not, because gravity is relatively weak there.

The "partly closed" event horison is an often cited imagination. (See Fig. 3) Photons, which started in perpendicular direction can escape, but others, which started slantwise, can't. This claim misses the target because of missing the scale. As height of event horizon is always very small, none of photons will escape. But this figure is just good to present that notion and even place of event horizon is not at all exact.

ad 5.) "Four weeks to fall"? - Maybe yes - maybe no . . (maybe rain - maybe snow . . ) If surface R₀ and "event horizon" R₁ of BH are just in proper distance (fare enough) - why not! But four minutes or even four mill-seconds would have been closer to reality. The "four weeks" data suggests quite false imagination.

ad 6.) Statement "his body will be lengthen" seems to be bizarre, but it is surly true! Near black hole change of gravity is also very big. Let's suppose that gravity grows 100 m/s² in every meter. Distance of upper and lower part of astronaut is cca. 0.5 meter and his body mass is cca. 100 kg. Then his waist will be pulled (and lengthen) by as much as 2500 newtons gravity force. As figure 4 shows this occurs at R₂= 1870 km above surface.
This extreme force grows exponentially and at R₃= 250 km it will tear in half an iron beam, if it is as tall as an astronaut. At the surface this force becomes million times bigger and tears this iron beam to bits (maybe atoms).

ad 7.) BH swallows just as much matter nearby as common stars do - no more and no less. They work under the very same physical law - i.e. gravity. They are unable to capture a heavenly body alone, a third big mass is needed to do so, just as case of common stars. Clouds of dust or gase are other case. They have inner friction, lost speed and are captured later. Effects depend on volume of central- and nearby masses only, nevertheless a common star or BH is in the centrum. Luminous swirling clouds or short period stars rotating around an invisible centre prove only the presence of an unidentified big mass and not the presence of the theoretical creature, BH.

ad 8.) Tunnel effect is best known in case of electrons. The so called "physical vacuum" borrows energy subatomic particles getting over obstacles. In case of photons this effect is unknown. But if so, no reason that pairs of positrons and electrons - to be birthed by escaped gamma-photons at theevent horizon - can overcome gravity field of a giant black hole and escape.

Another interesting but unproved theory that electrons escape, but positrons fall down. ( An often quoted figure is something like Fig. 5) As positrons are supposed to have negative mass ( ? ) and negative energy ( ?? ) so they are promising creatures for theoreticians to get rid of rotation and heat of BHs. . . Well, let us make a small calculation! One kilogram positron has 1.7*10²¹ coulomb positive charge. Capacity of a medium BH - as spherical condenser - is 1.6 micro-farad. (***) So one kilogram positron would cause 10²⁷ volt voltage at surface of BH. This huge voltage will push further positrons away and pull electrons backward.

There is one more hidden statement at Fig. 5. It shows a positron with an anti-clockwise spin and an electron with clockwise spin. Wrong imagination! Both particle have both spin direction, in 50-50% distribution. So spin of positrons are not suitable to stop revolving BHs.

ad 9.) To become as cool as absolute zero? BHs can't get rid of heat! It is rather sure that process 8 does not work. Also BHs can't get rid of electromagnetic waves (light for example) as it is our original postulate. And they can't get rid of matter (electrons for example). On contrary, they continuously swallow energy in form of very hot matter. So, how does it work?

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In my opinion there are too much suppositions in theory of BHs, house of cards is too high. Science often quotes 'Ocham's razor principle', well known and really useful: "Don't increase number of new parameters superfluously. Use maximum one!" In theory of BHs there are dozens of new parameters . . . Yes, they are maybe necessary. But to tell everybody that theory of BHs is full of unproved suppositions - it is also necessary.

Safe of Protected Minds Bureau - SPMB - certificates all details below :
Owner:  Thomas-t Title:  To Understand Black Holes Date:   11/27/2000 Time:   19:56 GMT Category:    cosmology	PROTECTED MINDS: BHs and other phenomenon show that speed of light depends on gravity.  A spacecraft can easily move to and fro across event horizon. BH swallows just as much matter nearby as common stars do - no more and no less. Spin of positrons are not suitable to stop revolving BHs.  BHs can't get rid of heat!  Theory of BHs is full of unproved suppositions.

(*) E_pot = E_kin ; . . . - G*M*m*( 1/R₀ - 1/R_S) = m*c²/2 ;
. . . R₀ = inf., . . . G=6.67*10^-11, . . R_S = 2*G*M/c²

(**) F_grav = F_centr ; . . . G*m*M/r² = m*r*omega² ;
. . . omega = 2pi/31558000;