#physic # [[Epistemic status]] #schroedinger-uncertain # Related - [[Poincare]] - [[Einstein]] - [[Physic/Time flowing is an illusion]] - [[Physic/Gravitation]] - [[Physic/Space-time]] - [[Philosophy/Epistemology/Einstein, Godel, and the relativity of truth]] - [[Physic/Lorentzian space-time]] # Relativity Einstein's equation $ E=mc^2 $ shows the relationship between mass (m) and energy (E), indicating that mass can be converted into energy and vice versa. When are you?  >A test of how well one has internalized the spirit of **Relativity** is how one is tempted to answer the question: **what would it be like to travel at 99.99 percent the speed of light?** A bad answer: due to the Lorentz-Fitzgerald contraction and to time dilation, one would feel squashed flat as a pancake and see time passing very slowly. A marginally better answer: one would indeed be squashed flat as a pancake and one’s clocks would be running slowly, but **this would not be noticeable** ~ [[Tim Maudlin]]   I think most people understands that time influences space, when an apple fall at minute 1, at minute 2 it will be closer to the ground. But what relativity imply is more than that, space also influences time, time goes faster or slower depending how fast you move, for example, and **you will not notice it**.  >According to the principle of **relativity**, the laws of physical phenomena must be the same for a fixed observer as for an observer who has a uniform motion of translation relative to him, so that we have not, nor can we possibly have, any means of discerning whether or not we are carried along in such a motion. >~ [[Poincare]] ## Bottlenecks >The existence of [[Schwarzschild singularity|singularities]] associated with gravitational collapse is considered by some an indication for the incompleteness of the general relativistic equations. It is not known whether or not these singularities are smoothed out by [[Quantum physic|quantum]] effects. >~ [[Abraham Pais - Subtle Is the Lord|Abraham Pais]] ## Thoughts - Our world is 4 dimensional, including time. - We say that the earth turn around the sun if we take the point of view of the sun, but what if we take the point of view of the universe? I guess it's the same, still have a hard time thinking about this, the universe is finite and ever-expanding I think according to [[Hawking]] (until the hypothetical [[Big crunch]] which should reverse the expansion and thus time). [[Poincare]] presents an example of a man living on a planet surrounded by cloud too thick to see the sky, thus they have to use other methods for cosmological and [[Physic]] discoveries, such as [[Geodesy]]. - The space I perceive is relative to my senses. i.e. [other animals may see the world in 2 or 4+ dimensions](http://archive.org/details/loreilleorganed00cyongoog/page/n156/mode/2up?view=theater) People who have lost a sense, vision for example, must have a very different sensation of space. Wouldn't a blind person be more interested in a geometry different from ours? If a small object emitting a strong deformation of space-time in any way, for example with a strong gravity, passed by my head, would I see the deformation? I don't think so because my senses would be distorted too. [[Neuroscience]] [Paper: How the brain sees the world in 3-D](https://www.sciencedaily.com/releases/2017/03/170321110312.htm) >We live in a three-dimensional world, but everything we see is first recorded on our retinas in only two dimensions. So how does the brain represent 3-D information? In a new study, researchers for the first time have shown how different parts of the brain represent an object's location in depth compared to its 2-D location. No, we do not live in a three-dimensional world, our **RELATIVE** experience of the world is in three dimension. >Thus the characteristic property of space, that of **having three dimensions, is only a property of our distribution table**, an internal property of the human intelligence, so to speak. It would be enough to destroy some of these connections, i.e. associations of ideas, to have a different distribution table, and **this could be enough for space to acquire a fourth dimension**. ~ [[Poincare]] ## Analogy If the earth and the solar system would somehow becomes 2x bigger on Monday, Bob would not notice that his hand is 2x bigger. ## **Relativity** & human language ![[Relativity and language]] ## Wisdom >It is with ordinary Mechanics that they must live; it is the only one they will ever have to apply; whatever the progress of automobilism, our cars will never reach the speeds where it is no longer true. The other is only a luxury, and one should only think of luxury when it is no longer likely to interfere with the necessary. ~ [[Poincare]] Unless we merge with machines, **relativity** is still very abstract to us, and invisible in our everyday life ## [[Biology/Evolution/Red Queen|Red Queen]] effect and **relativity** >The most curious part of the thing was, that the trees and the other things round them never changed their places at all: **however fast they went, they never seemed to pass anything.** "I wonder if all the things move along with us?" thought poor puzzled Alice. And the Queen seemed to guess her thoughts, for she cried, "Faster! Don't try to talk!" ~ [[Lewis Carroll]], Through the Looking-Glass ## Resources <iframe width="560" height="315" src="https://www.youtube.com/embed/Ov98y_DCvRY" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe> Similar topic links: [[Abraham Pais - Subtle Is the Lord]] [[Rulial space]]