Let's imagine that we are travelling through countries where the post gets gradually slower, and that we are sending a letter home to our father every day. Our father will receive the letters at lengthening intervals, because we will be arriving in places where the postal services takes longer to forward them. For him it will seem as if we have slowed down: initially he will get news of our day from us every day - but then he will have to wait several days, and eventually even weeks, just to learn about a single day of ours. For him, it is ass if our life has slowed...
If we then reach the desert, where there is no postal service at all, he will receive only the last letter we write before entering the desert, and it will arrive a long time after it was sent. For our father, the edge of the desert is therefore the place where for him our time stops. It is the horizon beyond which we can no longer be seen by him. He will continue to have information about us only "frozen at the desert's edge".
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which of these times is the 'real' one: the time of those at the horizon, or the time of those watching from a distance? The answer is: neither of them. it's meaningless. It is like asking which regions of the Earth are truly 'above' and which truly 'below'.
Quantum transitions of this kind - leaps from one configuration of space to another - are precisely what is described by loop quantum gravity.
The equations of ordinary quantum mechanics give the probabilities that jumps from one configuration to another will occur for a physical system that is in space. The equations of loop quantum gravity give the probabilities of leaps from one configuration of space to another configuration of space.
Scientists have a difficult relationship with their own ideas; perhaps no one is completely honest, even with oneself, about how much one believes... you need to be diplomatic, reasonable, admit that you could be wrong, but at heart there is a mad desire to scream, "but I'm sure that this is how things are!" we fall in love with our own ideas, are convinced by them...
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Paul Dirac, the most rational, impassive, cerebral, autistic of scientists, remarks in a lecture that the reason why it is rare for a good scientist who has obtained an important result to take the next step is taht they are the first to have doubts about their own results.
The disagreement concerns how much information you can cram into an entityt with a large volume but a small surface. One part of the scientific community is convinced that a black hole with a small horizon can only contain a small amount of information. Another disagrees.
What does it mean to 'contain information'?
More or less this; are there more things in a box containing five large and heavy balls, or in a box that contains twenty small marbles? The answer depends on what you mean by 'more things'. The five balls are bigger, they weigh more, so the first box contains more matter, more substance, more energy, more stuff, in this sense there are 'more things' in the box of balls.
But the number of marbles is greater than the number of balls. In this sense, there are 'more things, more details, in the box of marbles. If we wanted to send signals, by giving a single colour to each marble or each ball, we could send more signals, more colours, more information, with the marbles, because there are more of them. More precisely, it takes more information to describe the marbles than it does for the balls, because there are more of them. In technical terms, the box of balls contains more energy, whereas the box of marbles contains more information.
I aim at the core of the matter. I remove from my writing anything I can. I imagine those who know nothing about physics would find details useless and burdensome. The experts, on the other hand, know the details already; they are not interested in hearing them repeated. They want a novel perspective.
Where does the direction of time come from, if it is not inscribed in the fundamental grammar of the world?
It comes from the fact that we live in just one of the many solutions of the fundamental equations, and n this solution, the past appears special to us. The difference between past and future, that is, is a bit like the difference between two geographical directions for someone living in the mountains; in one direction, say north, the ground goes up; in the other, say south, it goes down. But this is not because north and south are intrinsically connected to up and down. Rather, only because around there things happen to be arranged in this way. On the Italian side of the Monte Bianco, 'upwards' is north, whereas on the French side, it is south. The irressistable flow of time is similarly a reflection of the way in which happen to be arranged.
