The universe does not end in heat death — it gets steered back on course infinitely many times
Tipler's omega point theory was wrecked by his own extravagant religious claims, but Deutsch says there is a valuable core inside: the universe must be continuously piloted in order to complete infinite computation in finite time.
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Tipler's theory was destroyed by Tipler himself
Deutsch has a precise criticism of Frank Tipler's omega point theory: the theory itself is ‘about the fabric of the whole of reality’, it does not belong to any one of the four strands but irreducibly to all four — that is very high praise. But in “The Physics of Immortality” Tipler made extravagant claims for his theory, and the result is that most scientists and philosophers threw the whole thing away, missing along with it the valuable core idea inside. Deutsch says that discarded core is what he is about to explain.
— Brett HallTipler holds the line on unitarity against observation
Faced with observations of accelerating expansion, Tipler will not concede. He invokes Hawking's result: an ever-expanding universe requires all black holes to evaporate through Hawking radiation, which destroys all the information inside them and thus violates the unitarity of quantum physics — probabilities must add up to one. Tipler's argument is: the accelerating expansion you see now is merely a local fact about us at this moment; wait long enough and contraction will begin, because unitarity cannot be violated. Brett points out that Tipler is also engaging in a kind of motivated reasoning, trying to derive from the omega point theory that Christianity is true and that a Christian-style resurrection of everyone will occur.
— Brett HallThe world is comprehensible because it is comprehensible
Deutsch's argument is: if we are to explain why the world appears comprehensible, the explanation may be that the world is comprehensible. And a theory that ‘the world is half comprehensible’ has no explanatory power at all; it merely restates the problem and introduces an inexplicable constant of 1/2. Brett says this is his new favourite sentence from rereading this chapter, a total refutation of those who say ‘the human mind will in the end be unable to understand ultimate physics’ — including Neil deGrasse Tyson, who worries that only an alien mind could understand the successor theory to quantum mechanics. The reason is in “The Beginning of Infinity”: we are universal explainers.
— Brett HallThe omega point needs someone at the helm the whole way
Deutsch points out a technical detail: the spacetime oscillations that make the omega point possible are of a classically chaotic instability, growing more violent the closer you get to the omega point. Any tiny deviation from the correct shape is rapidly amplified, enough to destroy the conditions for continued computation, so the big crunch would arrive after only finitely many steps of computation. So to satisfy the Turing principle and reach the omega point, the universe must be continuously ‘steered’ back onto the right trajectory. Tipler has already shown in principle how to do this by manipulating the gravitational field of the whole of space.
— Brett HallCramming infinitely many thoughts into the last second
Deutsch's argument: the stabilisation mechanisms and the technology for storing information must be improved infinitely many times, with density and stress rising without limit, which requires the continual creation of new knowledge, and Popperian epistemology says new knowledge requires rational criticism and therefore intelligent entities. So in the final frenzy, an infinite amount of stabilisation and knowledge creation happens in finite time. Someone will ask: with only a second left, why not rest? Deutsch says this is the biggest misunderstanding — these people's minds are programs running on computers of unbounded speed, and thoughts are the virtual reality those computers render. The subjective duration of a virtual experience is not determined by the time that elapses but by the computation executed during that time. Infinite steps of computation contain the time for infinitely many thoughts.
The Kardashev scale is pseudoscience
The host says outright that he ‘regards the Kardashev scale as pseudoscience’. The reason: how do you calculate how much energy is there? You can look at the amount of luminous matter, make various assumptions, but we do not know what dark matter is, we do not know whether zero-point energy can be tapped, there are too many unknowns — especially when you are talking about the distant future and about ‘being able to use all the energy around a star’, you might find another energy source. He groups it with the Drake equation: not a law of physics but a string of choices about variables, some constrained, many completely open. He also grumbles: Musk is very keen on it, so tech people are keen on it too.
Dark energy and the Church principle falsify each other
There are three independent lines of evidence for accelerating expansion: type 1a supernovae (a white dwarf accreting to 1.38 solar masses explodes, and thus has a standard luminosity, and they measure as dimmer, i.e. farther, than they should be), the acoustic peaks of the cosmic microwave background being larger than they should be, and the matter distribution of baryon acoustic oscillations. All three are most parsimoniously explained by accelerating expansion. But the host says this poses a two-way problem: the Church principle makes the dark energy observations suspect, and the dark energy observations make the Church principle suspect. The possible way out is that one of them is false, or that both are true and the universe will recollapse in the future, or cycle as Penrose says, with something odd happening at the end that lets information leak into the next universe.
Predicting future knowledge is self-contradictory
Deutsch cites Pa's argument: future human affairs depend on the growth of future knowledge, and we cannot predict which specific knowledge will be created in the future — because if we could predict it, by definition we would already possess that knowledge now. This is not ‘prediction is hard’ but logically impossible. So any large-scale prophecy about future human or posthuman affairs cannot be reliable. The host says this sentence is the point where the whole picture of the future converges, and is the core content of “The Beginning of Infinity” appearing ahead of time in “The Fabric of Reality”.
— HostIn their own words · checked verbatim
Unfortunately, Tipler himself in his book, The Physics of Immortality, makes exaggerated claims for his theory, which have caused most scientists and philosophers to reject it out of hand, thereby missing the valuable core idea, which I shall now explain.
Brett Hall8:09
If we want to understand why the world seems comprehensible, the explanation might be that the world is comprehensible.
Brett Hall33:32
But we know that the subjective duration of a virtual reality experience is determined not by the elapsed time but by the computations that are performed in that time. In an infinite number of computational steps, there is time for an infinite number of thoughts.
We need not play this role if we do not want to. If we choose not to and the cheuring principle is true, then we can be sure that someone else, presumably some extraterrestrial intelligence, will.
It is Titler's quasi religious interpretation of that future history and his failure to distinguish that interpretation from the underlying scientific theory that have prevented the latter from being taken seriously.
even if we concede that these assumptions are individually plausible, the overall conclusions cannot really claim to be more than informed speculation.
We cannot predict what specific knowledge will be created in the future because if we could, we should by definition already possessed that knowledge in the present.
Host1:25:09
I fully expect the accelerating universe idea to either be overturned or severely modified.
Host1:26:09
Figures
| Multiple of the age of the universe (time needed for galaxies to all become isolated) | at least about 5 times the age of the universe | 15:15 |
| Expected time of the big rip | about 200 billion years | 15:15 |
| Year dark energy was discovered | 1998 | 18:18 |
| Mass limit for a white dwarf to explode | 1.38 solar masses | 59:56 |
| Timescale for the end of the stellar era | 10 to the 14th power years | 1:05:57 |
| Timescale for all black holes to evaporate | 10 to the 100th power years | 1:06:58 |
| Upper bound on all future computation | 10 to the 120th power operations | 1:07:58 |
| Cosmological idea the host expects to be overturned or heavily revised | the accelerating-expansion universe | 1:26:09 |
| Theory the host guesses could resolve dark energy and dark matter | a theory of quantum gravity | 1:26:09 |
| Proposer of the cyclic universe model mentioned by the host | Penrose | 1:26:09 |
Glossary
- omega point
- The end state of the universe proposed by Tipler, in which life acquires infinite computational capacity.
- Church principle
- Any physically realisable computation can be carried out by a universal Turing machine.
- Kardashev scale
- A classification of civilisations by the total amount of energy they can harness.
- unitarity
- The mathematical requirement in quantum mechanics that probabilities must sum to one.
- CCC
- The conformal cyclic cosmology model proposed by Penrose, in which the universe continues through infinite cycles.
How to listen
Engineers and founders interested in cosmology, philosophy of physics and Deutsch's thought, especially anyone who wants to understand ‘why predicting future knowledge is logically impossible’.
The first 8 minutes of background on Tipler's theory can be skipped.