time

Adam Frank writes: KEY TAKEAWAYS When you look at a picture of a galaxy that is 75 million light-years away, you are seeing that galaxy at a time when dinosaurs ruled the Earth.  Distance translates into time because the speed of light is finite.   What you perceive as “now” is really layer after layer of light reaching your eye from many different moments in the past. Light from the time of the dinosaurs When you look at a picture of a galaxy that is 75 million light-years away, you are not seeing it as it is right now, but as it was when that light you are seeing left it 75 million years ago. That means you are seeing that galaxy Read More ›

That’s a perhaps surprisingly contentious topic among theoretical physicists: You see, whether time flows forward, or doesn’t flow at all, or moves back and forth, our resulting subjective experience would be identical in all cases: we would always find ourselves in an experiential snapshot extending smoothly backwards in memory and forwards in expectation, just like the desert road. We would always tell ourselves the same story about what’s going on. A mere cognitive narrative—based purely on contents of the experiential snapshot in question—would suffice to convince us of the forward flow of time even when such is not the case. The ostensible experience of temporal flow is thus an illusion.Bernardo Kastrup, “Do we actually experience the flow of time?” at Read More ›

Did Carlo Rovelli, start a fashion for debunking time with The Order of Time? Here’s science writer Marcia Bartusiak, author of Dispatches from Planet 3, asking whether it is time to just get rid of time: You might say that quantum mechanics introduced a fuzziness into physics: You can pinpoint the precise position of a particle, but at a trade-off; its velocity cannot then be measured very well. Conversely, if you know how fast a particle is going, you won’t be able to know exactly where it is. Werner Heisenberg best summarized this strange and exotic situation with his famous uncertainty principle. But all this action, uncertain as it is, occurs on a fixed stage of space and time, a Read More ›

Carlo Rovelli, author of The Order of Time, that there is neither space nor time: A present that is common throughout the whole universe does not exist. Events are not ordered in pasts, presents, and futures; they are only “partially” ordered. There is a present that is near to us, but nothing that is “present” in a far-off galaxy. The present is a localized rather than a global phenomenon. The difference between past and future does not exist in the elementary equations that govern events in the world. It issues only from the fact that, in the past, the world found itself subject to a state that, with our blurred take on things, appears particular to us. Locally, time passes Read More ›

Further to Carlo Rovelli’s views on time travel (only a technological problem, not a scientific one) and the order of time in general,  views, as set out in The Order of Time, our color commentator Rob Sheldon offers, — If I can speculate about what goes on in physicist’s heads, this issue about time is an attempt to force symmetry on the universe. Sorta like the 2-yr old who wants to regularize irregular verbs. “Mommy not home; she goed to the store.” Einstein’s Special Relativity (SR) argued that time was a fourth dimension and should not be treated any differently than height, width, and length. To get the units right, one only needed to multiply time by the speed of light–c*t. Only Read More ›