Spyman

Did you read the Wikipedia article with corresponding links? A type II supernova belongs to a sub-category of cataclysmic variable star known as a core-collapse supernova, which results from the internal collapse and violent explosion of a massive star. The presence of hydrogen in its spectrum is what distinguishes a type II supernova from other classes of supernova explosions. A star must have at least 9 times the mass of the Sun in order to undergo this type of core-collapse. http://en.wikipedia.org/wiki/Type_II_supernova

Do you think that the information gets more densely packed on the surface when it shrinks or that it will continue to keep its size when the mass starts to decrease?

rigney, I think it would be helpful if you explain what in your opinion the "entire galactic universe" consist of...

Hmm, maybe I don't understand the question or at least I interpret it differently than ajb. The Event Horizon is a feature of the Black Hole and the radius depends on the mass, so when the Black Hole evaporates the Event Horizon will shrink towards the center to finally vanish together with the Black Hole. If the Black Hole is so starved compared to its mass that it will evaporate before some particles outside of the Event Horizon would not have time to enter then those particles will obviously not be swallowed by the Black Hole and therefor not loose their information either. The Event Horizon is not a physicall object, it's a mathematical limit and as such it's thinner than the edge of a razor blade, any particles progressing through will normally pass quite fast. Infalling particles will observe a different and smaller radius for the Event Horizon than a distant observer and as such they will pass the larger radius observed by the distant observer in finite time according to their own clock. Event horizon The defining feature of a black hole is the appearance of an event horizon—a boundary in spacetime through which matter and light can only pass inward towards the mass of the black hole. Nothing, including light, can escape from inside the event horizon. The event horizon is referred to as such because if an event occurs within the boundary, light from that event cannot reach an outside observer, making it impossible to determine if such an event occurred. As predicted by general relativity, the presence of a large mass deforms spacetime in such a way that the paths particles take bend towards the mass. At the event horizon of a black hole, this deformation becomes so strong that there are no paths that lead away from the black hole. To a distant observer, clocks near a black hole appear to tick more slowly than those further away from the black hole. Due to this effect, known as gravitational time dilation, an object falling into a black hole appears to slow down as it approaches the event horizon, taking an infinite time to reach it. At the same time, all processes on this object slow down causing emitted light to appear redder and dimmer, an effect known as gravitational redshift. Eventually, at a point just before it reaches the event horizon, the falling object becomes so dim that it can no longer be seen. On the other hand, an observer falling into a black hole does not notice any of these effects as he crosses the event horizon. According to his own clock, he crosses the event horizon after a finite time, although he is unable to determine exactly when he crosses it, as it is impossible to determine the location of the event horizon from local observations. http://en.wikipedia.org/wiki/Black_hole

Well, I have Windows 2000 so that is easier said than done, and even if I take the long route by rightclicking on the picture, selecting properties and then copy and paste the adress found there, it doesn't seem to work for all pictures, for instance like the first one. If you can make it work, I would be grateful if you could fix the images in the thread I quoted from. (I am no longer able to edit such old post anyway due to the time limit.)

Velocity In the general sense, the absolute velocity of any object through space is not a meaningful question according to Einstein's special theory of relativity, which declares that there is no "preferred" inertial frame of reference in space with which to compare the object's motion. (Motion must always be specified with respect to another object.) This must be kept in mind when discussing the Galaxy's motion. Astronomers believe the Milky Way is moving at approximately 630 km per second relative to the local co-moving frame of reference that moves with the Hubble flow. If the Galaxy is moving at 600 km/s, Earth travels 51.84 million km per day, or more than 18.9 billion km per year, about 4.5 times its closest distance from Pluto. The Milky Way is thought to be moving in the direction of the Great Attractor. The Local Group (a cluster of gravitationally bound galaxies containing, among others, the Milky Way and the Andromeda galaxy) is part of a supercluster called the Local Supercluster, centered near the Virgo Cluster: although they are moving away from each other at 967 km/s as part of the Hubble flow, the velocity is less than would be expected given the 16.8 million pc distance due to the gravitational attraction between the Local Group and the Virgo Cluster. Another reference frame is provided by the cosmic microwave background (CMB). The Milky Way is moving at around 552 km/s with respect to the photons of the CMB, toward 10.5 right ascension, -24° declination (J2000 epoch, near the center of Hydra). This motion is observed by satellites such as the Cosmic Background Explorer (COBE) and the Wilkinson Microwave Anisotropy Probe (WMAP) as a dipole contribution to the CMB, as photons in equilibrium in the CMB frame get blue-shifted in the direction of the motion and red-shifted in the opposite direction. http://en.wikipedia.org/wiki/Milky_Way

A White Hole, but it would differ from expansion of the Universe since there is no center placed inside space.

If the Hawking radiation is correct then the immense gravity from the Black Hole itself would create a 'thermal bath of particles' that continues to enter through the Event Horizon. Hawking radiation (also known as Bekenstein-Hawking radiation) is a thermal radiation with a black body spectrum predicted to be emitted by black holes due to quantum effects. ... Black holes are sites of immense gravitational attraction. Classically, the gravitation is so powerful that nothing, not even electromagnetic radiation, can escape from the black hole. It is yet unknown how gravity can be incorporated into quantum mechanics, but nevertheless far from the black hole the gravitational effects can be weak enough that calculations can be reliably performed in the framework of quantum field theory in curved spacetime. Hawking showed that quantum effects allow black holes to emit exact black body radiation, which is the average thermal radiation emitted by an idealized thermal source known as a black body. The electromagnetic radiation is as if it were emitted by a black body with a temperature that is inversely proportional to the black hole's mass. Physical insight on the process may be gained by imagining that particle-antiparticle radiation is emitted from just beyond the event horizon. This radiation does not come directly from the black hole itself, but rather is a result of virtual particles being "boosted" by the black hole's gravitation into becoming real particles. A slightly more precise, but still much simplified, view of the process is that vacuum fluctuations cause a particle-antiparticle pair to appear close to the event horizon of a black hole. One of the pair falls into the black hole whilst the other escapes. In order to preserve total energy, the particle that fell into the black hole must have had a negative energy (with respect to an observer far away from the black hole). By this process, the black hole loses mass, and, to an outside observer, it would appear that the black hole has just emitted a particle. In reality, the process is a quantum tunneling effect, whereby particle-antiparticle pairs will form from the vacuum, and one will tunnel outside the event horizon. ... Hawking radiation is required by the Unruh effect and the equivalence principle applied to black hole horizons. Close to the event horizon of a black hole, a local observer must accelerate to keep from falling in. An accelerating observer sees a thermal bath of particles that pop out of the local acceleration horizon, turn around, and free-fall back in. The condition of local thermal equilibrium implies that the consistent extension of this local thermal bath has a finite temperature at infinity, which implies that some of these particles emitted by the horizon are not reabsorbed and become outgoing Hawking radiation. ... Under experimentally achievable conditions for gravitational systems this effect is too small to be observed. http://en.wikipedia.org/wiki/Hawking_radiation

Sorry, I don't know how to do that, the images are on Wikipedia and I only post the link to them. If a mod can do it and/or someone explain how I could make them smaller when linking to them I would be grateful. Is it possible to somehow rescale images while linking to them without uploading or editing the images themself? Would be great with such an option since a lot of pictures are to big to fit well into the forum posts.

If the extreme densities at the initial condition of the Big Bang was without a singularity then why do you think that Black Holes still could have them? Extrapolation of the expansion of the Universe backwards in time using general relativity yields an infinite density and temperature at a finite time in the past. This singularity signals the breakdown of general relativity. http://en.wikipedia.org/wiki/Big_Bang Also what do you think would happen to a Black Hole if it would consume so enormous much mass that the radius of the Event Horizon should exceed the Hubble Sphere?

I think we would be able to see a starved Black Hole despite its invisible interior, since a black hole can be observed by the stars that are obscured by it. Simulated view of a black hole in front of the Large Magellanic Cloud. http://en.wikipedia.org/wiki/Black_hole A Black Hole that is feeding can also be observed through the accretion disc of material that spiral inward towards the center while emitting radiation. Artist's conception of a binary star system with one black hole and one main sequence star. http://en.wikipedia.org/wiki/Accretion_disc

I also said: ---------- Ok.

What I 'hear' when I am told that "paleomagnetic data has been used to calculate that the radius of the Earth 400 million years ago was 102 ± 2.8% of today's radius" is that the tolerance of the estimate is good enough to falsify whether the Earth has expanded to TWICE its radius during the last 400 millions of years, but does not have the accuracy for making claims that the circumference of Earth is shrinking with millimeters per year. The tolerance level tells me that the Earth could have been slightly smaller 400 million years ago.

Your Link is broken, is this the correct one: http://en.wikipedia.org/wiki/Expanding_earth_theory#Current_status ? One prominent present day advocate of an expanding Earth is comics artist Neal Adams, who calls his ideas "Growing Earth Theory". He believes that an Earth with half its present radius would allow the continents to fit together perfectly, completely closing both the Atlantic and Pacific oceans. http://en.wikipedia.org/wiki/Expanding_earth_theory#Current_status In the light of ideas with the Earth growing from HALF it's radius, a scientific calculated estimate from measured data reveling a change of 102 ± 2.8% of today's radius in the past could be interpreted as "no significant change" and that "therefore earth expansion is untenable".

Ooh Yes, the two statements you made are wrong according to current models of cosmic expansion. False. False. The truth is that we currently are observing objects that were receding from us FTL due to cosmic expansion, when the light we see now were emitted. No, the rate of the expansion is accelerating right now but we STILL continue to observe objects that are receding from us FTL even though the expansion is accelerating and not decreasing. The fact that our possible descendents won't be able to observe light emitted right now from very distant objects, in a far far distant future due to an accelerated expansion is NOT an valid argument against us seeing objects today that were receding from us FTL in a distant past when they emitted that light from a relative close distance. Sure, if the expansion of the Universe continues to accelerate as it does then we will never be able to observe light emitted outside of the Hubble sphere right now, but we will still be able to continue to observe objects receding from us FTL in plenty of Billions of years to come. And then after some ~ 2 Trillions of years objects outside of the Local Supercluster will get redshifted so much that they will not be detectable any more.

Yes, photons traversing between two objects in expanding space would need to travel longer than photons in flat space to bridge the distance and the first photon in a lightray has a shorter path than the last photon, causing the lightray to be stretched which we can measure as redshift. Hubble's law of the correlation between redshifts and distances is required by models of cosmology derived from general relativity that have a metric expansion of space. As a result, photons propagating through the expanding space are stretched, creating the cosmological redshift. http://en.wikipedia.org/wiki/Redshift

A tale of two big bangs Whenever you hear or read about cosmology, there is one distinction you should have in the back of your mind - otherwise, matters might get a bit confusing: The term "big bang" has two slightly different meanings, and the answer to questions like "Did the big bang really happen" depends crucially on which of the two big bangs you are talking about. Did the big bang really happen? If you are talking about the big bang phase, the hot early universe as described by well-known physical theories (or, if you include inflation, by extrapolation from those theories), then there is good evidence that, yes, nearly 14 billion years ago, the cosmos developed in just the way described by the cosmological models (the main exhibits are the original abundances of light elements as deduced from astronomical observation, the distribution of far-away galaxies and the existence and properties of the so-called cosmic background radiation). Whether or not there really was a big bang singularity is a totally different question. Most cosmologists would be very surprised if it turned out that our universe really did have an infinitely dense, infinitely hot, infinitely curved beginning. Commonly, the fact that a model predicts infinite values for some physical quantity indicates that the model is too simple and fails to include some crucial aspect of the real world. Thus, while some cosmologists do not have a problem with assuming that our universe began in a singular state, most are convinced that the big bang singularity is an artefact - to be replaced by a more accurate description once quantum gravity research has made suitable progress. To be replaced with what? Nobody knows for sure. In some models, we can go infinitely far into the past (one example is presented in the spotlight text Avoiding the big bang). In others, the big bang is replaced by a beginning of the universe which avoids all infinities, but in which time itself is rather different from what we are used to (some more information about this can be found in the spotlight text Searching for the quantum beginning of the universe). http://www.einstein-online.info/en/spotlights/big_bangs/index.html

UVB-76 is the callsign of a shortwave radio station that usually broadcasts on the frequency 4625 kHz (AM full carrier). It's known among radio listeners by the nickname The Buzzer. It features a short, monotonous buzz tone, repeating at a rate of approximately 25 tones per minute, for 24 hours per day. The station has been observed since around 1982. On rare occasions, the buzzer signal is interrupted and a voice transmission in Russian takes place. Only three to four such events have been noted. Despite much speculation, the actual purpose of this station remains unknown. The station's transmitter is located just outside Povarovo, Russia at 56°4′58″N 37°5′22″E, which is about halfway between Zelenograd and Solnechnogorsk and 40 kilometres (25 mi) northwest of Moscow, near the village of Lozhki. The location and callsign were unknown until the first voice broadcast of 1997. Frequently, distant conversations and other background noises can be heard behind the buzzer: this suggests that the buzzing device is behind a live and constantly open microphone (rather than a recording or automated sound being fed through playback equipment) or that a microphone may have been turned on accidentally. Satellite photo of UVB-76 transmitter in Povarovo, Russia. http://en.wikipedia.org/wiki/UVB-76

This is wrong according to current models of cosmic expansion. So, how fast was the radiating matter receding from us when the CMBR we observe today was emitted? ---------- Here is a good Cosmos calculator you should test: http://www.uni.edu/morgans/ajjar/Cosmology/cosmos.html You need to input these values: Omega=0.27, Lambda=0.73, Hubble=71 and Redshift=1100 for the CMBR. But anything we observe with a redshift higher than 2 was receding from us faster than c when the image we observe now was emitted.

The Oort cloud is thought to be a remnant of the original protoplanetary disc that formed around the Sun approximately 4.6 billion years ago. The most widely accepted hypothesis is that the Oort cloud's objects initially coalesced much closer to the Sun as part of the same process that formed the planets and asteroids, but that gravitational interaction with young gas giant planets such as Jupiter ejected the objects into extremely long elliptic or parabolic orbits. Simulations of the evolution of the Oort cloud from the beginnings of the Solar System to the present suggest that the cloud's mass peaked around 800 million years after formation, as the pace of accretion and collision slowed and depletion began to overtake supply. Analysis of the carbon and nitrogen isotope ratios in both the Oort cloud and Jupiter-family comets shows little difference between the two, despite their vastly separate regions of origin. This suggests that both originated from the original protosolar cloud, a conclusion also supported by studies of granular size in Oort cloud comets and by the recent impact study of Jupiter-family comet Tempel 1. http://en.wikipedia.org/wiki/Oort_cloud

Yes, the Hydrogen Atoms in the Local Interstellar Cloud are emitting thermal radiation, but the amount of heat energy are dependent of the density of the cloud. Less atoms available for emitting heat means that less photons will be radiated and less photons radiated gives a weaker photon field. Since the cloud is so insubstantial thin the photon field is going to be irrelevant faint too. I don't have the knowledge how to calculate the amount of radiation expelled from the cloud and then recieved on a moving object through it. But by intuition my impression is that the rise of temperature from thermal radiation will be inferior compared to heat transfer when the reciever is in direct contact with the emitter. I think the comets will get a much higher temperature increase from the material they are able to scoope up while going through than from the thermal radiation off the surronding cloud. Granted any comets from the Oort Cloud will get heat from both collisions with matter in the Local Fluff and from heat radiation emitted off it, but the comets are also able to release heat by emitting thermal radiation. By observation we do know that there are comets with vast orbits extending far out from the Sun, in which they spend or have spent a significant duration beyond the Sun's magnetosphere. Evidence tells us that comets are able to survive out there, they don't get "vaporised" by the hot dust outside.

The ‘ultimate fate’ and age of the universe The value of the Hubble parameter changes over time either increasing or decreasing depending on the sign of the so-called deceleration parameter q which is defined by [math]q=-(1+ \frac{\dot{H}}{H^2})[/math] . In a universe with a deceleration parameter equal to zero, it follows that H = 1/t, where t is the time since the Big Bang. A non-zero, time-dependent value of q simply requires integration of the Friedmann equations backwards from the present time to the time when the comoving horizon size was zero. It was long thought that q was positive, indicating that the expansion is slowing down due to gravitational attraction. This would imply an age of the universe less than 1/H (which is about 14 billion years). For instance, a value for q of 1/2 (once favoured by most theorists) would give the age of the universe as 2/(3H). The discovery in 1998 that q is apparently negative means that the universe could actually be older than 1/H. However, estimates of the age of the universe are very close to 1/H. http://en.wikipedia.org/wiki/Hubble%27s_law

This is old news, from October 2009, have you tried searching for it with Google?

Lets assume a frozen comet of water ice with a temperature of -330ºC, a radius of 10km and a mass of 2×1014kg. The Local Fluff is ~30 lightyears across and if the orbital speed and circumference of the comet around the Sun is very low compared to the Solar Systems speed and path, then the extra trajectory of the comets orbit can be neglected. Then the comet "punches" a hole with a Volume of 30×299792458×60×60×24×365.25×π×100002= ~89×1024m3. While creating this hole in the Local Fluff the comet will collide with 0.1×100×100×100 Hydrogen Atoms per cubic meter, which have a mass of 1.00794×1.660538782×10-27kg each. The accumulated mass on the comet during the travel will thus be 100000×1.67×10-27×89×1024= ~15000kg. Adding 15000kg with a temperature of 6000ºC to a massive body of 2×1014kg with a temperature of -330ºC will increase the average temperature to (6000×15000-330×2×1014)/(2×1014+15000)= -329.99999953ºC. The comet would, after ~100000 years of travel through the Local Fluff, exit at the other end with a temperature of roughly 0.0000005ºC higher than what it entered with. Even if we disregard the possibility of the comet cooling itself by emitting thermal radiation it would still survive much much longer than the duration the Milky Way is thought to have been around.

The process of Black Hole formation is only theoretical. Formation and evolution Considering the exotic nature of black holes, it may be natural to question if such bizarre objects could exist in nature or to suggest that they are merely pathological solutions to Einstein's equations. Einstein himself wrongly thought that black holes would not form, because he held that the angular momentum of collapsing particles would stabilize their motion at some radius. This led the general relativity community to dismiss all results to the contrary for many years. However, a minority of relativists continued to contend that black holes were physical objects, and by the end of the 1960s, they had persuaded the majority of researchers in the field that there is no obstacle to forming an event horizon. Once an event horizon forms, Roger Penrose proved that a singularity will form somewhere inside it. Shortly afterwards, Stephen Hawking showed that many cosmological solutions describing the Big Bang have singularities without scalar fields or other exotic matter (see Penrose-Hawking singularity theorems). The Kerr solution, the no-hair theorem and the laws of black hole thermodynamics showed that the physical properties of black holes were simple and comprehensible, making them respectable subjects for research. The primary formation process for black holes is expected to be the gravitational collapse of heavy objects such as stars, but there are also more exotic processes that can lead to the production of black holes. Gravitational collapse Gravitational collapse occurs when an object's internal pressure is insufficient to resist the object's own gravity. For stars this usually occurs either because a star has too little "fuel" left to maintain its temperature, or because a star which would have been stable receives extra matter in a way which does not raise its core temperature. In either case the star's temperature is no longer high enough to prevent it from collapsing under its own weight (the ideal gas law explains the connection between pressure, temperature, and volume). The collapse may be stopped by the degeneracy pressure of the star's constituents, condensing the matter in an exotic denser state. The result is one of the various types of compact star. Which type of compact star is formed depends on the mass of the remnant — the matter left over after changes triggered by the collapse (such as supernova or pulsations leading to a planetary nebula) have blown away the outer layers. Note that this can be substantially less than the original star — remnants exceeding 5 solar masses are produced by stars which were over 20 solar masses before the collapse. If the mass of the remnant exceeds ~3-4 solar masses (the Tolman-Oppenheimer-Volkoff limit)—either because the original star was very heavy or because the remnant collected additional mass through accretion of matter—even the degeneracy pressure of neutrons is insufficient to stop the collapse. After this no known mechanism (except possibly quark degeneracy pressure, see quark star) is powerful enough to stop the collapse and the object will inevitably collapse to a black hole. This gravitational collapse of heavy stars is assumed to be responsible for the formation of most (if not all) stellar mass black holes. http://en.wikipedia.org/wiki/Black_hole