He told a Dublin conference that black holes did not destroy everything they consumed but instead eventually fired out "mangled" matter and energy. But the above discussion should be accurate enough to undertand what's going on outside and near the horizon.Renowned physicist Stephen Hawking on Wednesday put forward a radically-revised version of his theory on the nature of black holes, which formed where stars collapse. The true picture in a more realistic Belinsky-Khalatnikov-Lifshitz model has the spacetime stretching and oscillating chaotically as the masses approach the singularity. This assumes an idealised theoretical Schwarzchild black hole, where the infalling mass is assumed to have no gravity itself. If the star fell in millions of years earlier, its clock would show the much earlier time. The time experienced by either between crossing the event horizon and hitting the singularity is roughly the same. So as seen in the diagram, the collapsing star and the observer hit it at different now-spatial positions along it. The singularity is twisted round so instead of being timelike it is now spacelike. But the falling observer hits the singularity themselves before they see the star's matter complete its journey. They see the collapsing star pass through the event horizon and head rapidly towards the singularity. (Although times are not really comparable as being 'before' and 'after' one another when separated by an event horizon like this.)įor a falling observer, their past lightcone rapidly approaches and crosses the event horizon, and their view of the past is no longer being redshifted as much. This continues long after the objects have hit the singularity and ceased to exist. No matter how far up the page you go, the hovering observer can still see the light from everything that has fallen in in the past. The longer the time, the more oblique the angle and the slower (more red-shifted) the emissions seem to be, but the process never stops. They see the light of the collapsing star that fell into the hole millions of years ago, still struggling up out of the gravity well. These are called the past lightcone at the point.Īn observer hovering at a constant distance outside the black hole travels along the hyperbola shown on the right. Tilt your head $45^$ lines pointing down the page. To explain what is going on, here is a picture of a black hole, using a special coordinate system (Kruskal-Szekeres coordinates) that twists round to keep the lightcones aligned. Things fall 'onto' the event horizon, but as time slows down there, they get slower and slower, the light more red-shifted, and never reach it. So am I right if I say they end up separated in space (in radial direction), while their clocks show a difference?įrom the way you word your question, I gather you are thinking of a black hole in terms of the 'frozen star' picture common in early theory. The basic question: If two particles fall in from a hovering platform outside the horizon, a large time after one another (say a million years) how will they end up relative to one another in the frame of the particle that falls last? I can't imagine the second particle will ever meet the second. So let's assume a classical black hole without Hawking radiation. What is there to be said about this? Is this what is meant with ending up in the past relative to the universe around the hole? It seems we don't end up at the same point in spacetime. So it seems we end up with a lot of space between us in radial direction as well as with different ages. When I jump in however, will he/she have disappeared behind the horizon through which I will fall too. It seems that from the fixed position he/she ends up at the horizon while my clock ticks on. How do we end up relative to one another in space and time? Will I be a lot older than him/her? Will our distance wrt to each other grow to infinity, due to the tidal force that accelerates him/her away from me? I wait a million years and jump from the same position. Say, we are point-particles.įrom a fixed distance someone jumps into a black hole. Imagine we live eternally and can survive tidal forces.
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