The word paradox, of Greek origin, can refer to something contrary to common sense, or something that happens against what is expected and causes astonishment. Discover 6 of these below.
Grandfather Paradox
One of the possible paradoxes that would arise from potential time travel is popularly known as the grandfather paradox.
In the book “The Imprudent Traveller” (El Viajero Imprudente), this paradox was outlined for the first time, used by many physicists to demonstrate the risks of time travel.
There, the character who goes back in time assassinates his grandfather before he has entered into a romantic relationship with his grandmother. In this extension of himself, i.e., his grandfather in the past, the imprudent traveller would make the mistake of potentially annihilating himself in a possible future, giving rise to the grandfather paradox.
EPR Paradox
The Einstein-Podolsky-Rosen paradox or EPR paradox is a thought experiment intended to demonstrate an inherent paradox in the early formulations of quantum theory. It is one of the most famous examples of quantum entanglement. The paradox involves two particles that are entangled according to quantum mechanics. According to the Copenhagen interpretation of quantum mechanics, each particle is individually in an uncertain state until it is measured, at which point the state of that particle becomes certain.
At that exact same moment, the state of the other particle also becomes certain. The reason this is classified as a paradox is that it apparently involves communication between the two particles at speeds faster than the speed of light, which is in conflict with Albert Einstein’s theory of relativity.
Twin Paradox
It is a thought experiment that analyzes the different perception of time between two observers with different states of motion. This paradox was proposed by Albert Einstein when developing what is known today as the theory of special relativity. The twin paradox poses that, due to the effect known as time dilation, an astronaut would return from an interstellar journey at speeds close to the speed of light considerably younger than their twin brother on Earth.
Fermi Paradox
It is the apparent contradiction between estimates that claim there is a high probability of other intelligent civilizations existing in the observable universe and the absence of evidence for such civilizations.
Schrödinger’s Cat Paradox
It is a thought experiment, sometimes described as a paradox. The scenario presents a hypothetical cat that can be simultaneously alive and dead, a state known as quantum superposition, as a result of being linked to a random subatomic event that may or may not occur.
Information Paradox
In the 1970s, Stephen Hawking argued that black holes forever destroy the information contained in the matter that falls into them. If this were the case, it would violate one of the basic postulates of quantum mechanics.
A proposal to resolve this paradox is the so-called “complementarity principle”. This maintains that the information falling into a black hole is never lost, although its fate depends on the observer’s point of view.
String theory seems to offer a theoretical framework in which to accommodate this principle. In particular, various calculations have managed to explain the entropy and radiation rate of certain black holes in terms of quantum strings.