A mathematical model for time travel

Welcome for time travellers

On May 2 2017, Newsweek published an article with this title:

Time travel is mathematically possible with mind-boggling model

You may well imagine that, with that title, the article will rather fall into the category of sensationalist papers on seemingly scientific issues. Indeed, in a quick reading of this article I have detected the following inaccuracies:

1. The title does not make clear the difference between a theoretical possibility of traveling in time and building a time machine. That is, the different between theory and practice. What Ben Tippett has developed is a purely theoretical mathematical model.
2. It presents the idea as something new which puts an end to a string of failures and disappointing calculations. Space-time loops, however, are known to be compatible with the general theory of relativity since quite a long time ago. In 1992, for instance, Stephen Hawking came to the conclusion that it would not be possible to use them without negative energy, something that is not known to exist. In 2005, the Israeli Amos Ori proposed a procedure that would not require it, consisting of spinning around an empty toroid region surrounded by a sphere containing enormous amounts of matter (e.g. a black hole). This is not so different from what is being proposed now.

Is the increase in life expectancy accelerating?

Nick Bostrom

Some philosophers, such as Nick Bostrom and the transhumanists, have concocted an updated version of Nietzsche’s superman. Their forecasts are based on two scientific advances presented as imminent since several decades ago: immortality, which will be attained when the advances in medicine increase life expectancy beyond one year per year; and artificial intelligence, the design of super-intelligent machines. Both advances could be combined to attain immortality through artificial intelligence, by downloading our conscience (something we cannot even define scientifically) into a super-intelligent machine, so that it would go on existing inside the machine.

Unfortunately for transhumanists, the UN data do not confirm their expectations. Let us look first at the data about the evolution of the maximum life expectancy in the world from 1950 to 2015 (see table 1). These and the following data have been taken from https://esa.un.org/unpd/wpp/Download/Standard/Mortality/.

Four ideas by Alvin Plantinga about God and materialism

Alvin Plantinga

Taking advantage of the awarding of the Templeton Prize to the American philosopher Alvin Plantinga, this post will try to review a few of his thoughts in the debate between theism and materialism. As it is impossible to review all his work in detail, I will mention just four of his ideas:

1. The Mozart argument for the existence of God. Why are we able to appreciate beauty? According to the materialistic hypothesis, there is no explanation why evolution has led us to this, as it is difficult to see how this trait could be useful for our survival. Instead of good music, we should appreciate cacophony, which is more abundant in nature. If we assume that God exists, however, this fact is easy to explain, because God appreciates beauty (in fact, God is beauty). This argument, along with many others, is in this web address.

Is there a universe?

The Spanish Wikipedia defines the universe thus:

The universe is the totality of space and time, all forms of matter, energy and momentum, plus the laws and physical constants that govern them. However, this term is also used in slightly different contextual senses and refers to concepts such as cosmos, world or nature. Its study, at the highest scales, is the object of cosmology, a discipline based on astronomy and physics, which describes all the aspects of this universe, together with its phenomena.

Before applying to the universe, the Greek word cosmos meant order and beauty. Notice that this sense is maintained in one of its derivatives, the word cosmetic. The Latin word mundus also has the two meanings: as a noun, it means the world, the totality. As an adjective, clean, neat, elegant. Presumably the first sense was copied from Greece, and to translate the world cosmos they adopted the same word that represented in Latin its other meaning. Finally the word nature (physis in Greek) has phenomenal connotations (rather than to the universe, it refers to what happens in it). From this word come physics (the study of nature) and metaphysics (beyond physics).