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The time barrier that prevents formation of black holes
As a mass is compacted to have a smaller and smaller radius, the escape velocity at the surface of the resulting sphere increases. If the sphere could be compacted to a critical radius (called the Schwarzschild radius) so that the escape velocity at the surface of the sphere is equal to the speed of light, nothing could escape from the gravity field. The result would be the formation of a black hole. However, the dilation of time that occurs with increasing gravity erects an impenetrable barrier at the Schwarzschild radius that is able to prevent any mass from compacting sufficiently to form a black hole.
Einstein’s theory of general relativity predicts that gravity affects distance, light and time. When a distant observer watches how light is impacted by gravity, it appears that gravity decreases the frequency of light and the wavelength of light. If the frequency of the light is used as a clock to measure the passage of time, then gravity can be understood to slow down the clock that measures the passage of time. This phenomena, referred to as time dilation, results in different perspectives on how fast things occur dependent upon the observer's location in a gravity field. Something that appears to occur quite slowly when measured by the clock of an observer in a relatively weak gravity field, will appear to occur much faster when measured by the clock of an observer in a stronger gravity field.
How time is affected at the surface of a very compacted mass
Because of the effects of gravity, very large masses, such as a planet or a sun, tend to have the shape of a sphere. As a large mass is compacted the force of gravity at the surface of the resulting sphere increases. The increase in the force of gravity at the surface decreases the frequency of light and thus the clock that measures the passage of time. As a result what takes place in a very short time as measured by a clock near the surface of such a compacted mass, can take place in a much longer time when measured by the clock of a distant observer. The interesting effects that this can produce may be understood by considering Bob’s adventure as he approaches a very compact mass. Betty, from a large distance away, will use a camera to produce a video recording of Bob’s adventure. As Bob draws near to the surface of the compacted mass, Bob will perceive things happen in a very short time that will be perceived by Betty as taking a very long time. Betty, therefore, will use the fast forward playback feature of the camera in order to understand how events appear to Bob.
Let’s say Betty and Bob are exploring the universe and spy in the distance a mass compacted so much that the escape velocity at the surface of the mass is just at the speed of light. They are curious and want to learn more. Bob volunteers to travel down to the surface, take a look and report back. Bob starts down. What happens to Bob? Betty records it on her video camera.
Figure 1, not to scale, represents how Betty sees Bob’s journey. As Bob gets close to the surface of the mass, his progress seems to slow down. Finally just before he arrives, he is going so slow that, to Betty, he appears to stop moving. The reason for this is that Bob's progress is measured by Bob's clock. However, from Betty's perspective, Bob's clock keeps moving slower and slower as Bob approaches the surface. As the clock at Bob's location slows, Bob's progress is slowed until he appears to Betty to be standing still. This slowing of the passage of time and the accompanying effect of length contraction (another relativistic effect caused by gravity) prevents Bob from ever reaching the surface.
Betty is patient, so she decides to keep recording. As she watches, radiation from space overtakes and impacts Bob. Betty's camera is very sensitive so the portion of radiation that impacts Bob and reflects back to Betty brings with it a progress report on Bob's location and condition. As it turns out, everything in the universe eventually disintegrates into radiation*. After a very long time Betty notices that Bob also is disintegrating into radiation. It may take a very long time (things like protons are pretty stable) for Bob to completely disintegrate, but eventually all of Bob has been emitted as radiation and Bob is gone. Thus, in Betty’s time frame, as recorded, Bob ended his journey suspended in space, slowly disintegrating with some of the resulting radiation rising back into space and toward Betty.
To understand how
Bob perceived the
journey, Betty plays back the video of Bob’s
journey in increasingly faster motion as Bob approaches the surface
of the mass. Because of the force of
gravity, Bob will perceive himself to be going very fast near the
surface, so Betty speeds
up the video accordingly. The fast forward version of the video shows
hurtling towards the surface and then in a very brief instant of time
Bob went from being whole to being gone. In Bob’s perception, he
instantly disintegrated before reaching the surface. Figure 2 shows
Bob’s complete journey. All the radiation that in Betty's
perception overtook Bob over the course of the long time he was near
the surface of the mass, in Bob's perspective arrived almost
instanteously, making things uncomfortably warm for him and hastening
What Bob’s demise teaches about Cosmology
What happened to Bob is the fate of everything in a very strong gravity field where the escape velocity is close to the speed of light. The disintegration that from the time frame of a weaker gravity field takes a long time, happens instantaneously in a gravity field where the escape velocity is close to the speed of light.
This is why a star can never collapse into a black hole. Once a collapsing star has compacted so that the escape velocity at the surface of the collapsing star approaches the speed of light, the disintegration of the matter at the surface of the collapsing star that appears to take a very long time when observed from a distance will happen instantly. This instant disintegration will reduce the mass of the collapsing star and the gravity at its surface. Because of the reduced gravity, the star can compact further until the escape velocity at the surface of the collapsing star again approaches the speed of light. The process repeats until enough of the mass of the collapsing star has disintegrated so that it no longer collapses.
The disintegration that happens instantaneously in
the time frame at
the surface of the collapsing star takes much longer in the time
frame of a distant observer. To a distant observer, the collapsing
star in its early stages of collapse can appear to be a dark mass
compacted to a radius slightly larger than the critical radius for a
black hole, and thus indistinguishable from a black hole. As
of the collapsing star disintegrates so that the critical radius
retreats into the collapsing mass--lessening the effects of time
dilation--bursts of radiation from the collapsing star will be seen,
explaining the sudden appearance of quasars.
For a more thorough treatment of this subject, see the two
journal articles: Five
fallacies used to link black holes to Einstein’s relativistic
space-time and How
black holes violate the conservation of energy.
Copyrighted Article--by Doug Weller--used with permissionComments