If you and I are in separate space ships both traveling fast, there’s literally no possible way to determine if I am staying still and you are moving, or if you are staying still and I am moving, or if we are both moving. Also, from your perspective time will flow normally for you and slower for me, but from my perspective time will flow normally for me and slow for you.
Basically, everything, including time, is completely relative.
A hand drawn diagram from Carl Sagan representing all of space and time. The X axis represents time, going into the future and into the past and the Y axis represents scale, from the size of the electron to the distances between galaxies. It marks the relatively small “realm of direct human experience” and the much larger “realm of quantum physics” and “realm of special relativity.”
“Conceptually, the metric tensor defines how spacetime itself is curved. Its curvature is dependent on the matter, energy and stresses present within it; the contents of your Universe define its spacetime curvature. By the same token, how your Universe is curved tells you how the matter and energy is going to move through it. We like to think that an object in motion will continue in motion: Newton’s first law. We conceptualize that as a straight line, but what curved space tells us is that instead an object in motion continuing in motion follows a geodesic, which is a particularly-curved line that corresponds to unaccelerated motion. Ironically, it’s a geodesic, not necessarily a straight line, that is the shortest distance between two points. This shows up even on cosmic scales, where the curved spacetime due to the presence of extraordinary masses can curve the background light from behind it, sometimes into multiple images.”
Sure, you know what space and time are. If you heard of Einstein and relativity, you might know that they’re not absolute quantities, but that how you experience distances and the ticking of clocks is dependent on your motion through the Universe. But did you also know that the addition of masses and gravitation to the theory didn’t just result in general relativity, but changed the way we viewed the Universe completely? If you told me the positions, momenta and all the other properties of all the matter and energy in the Universe, I could tell you everything thanks to general relativity. I could tell you what the Universe would look like and what its behavior would be at any point in time: past, present or future. I could tell you the birth and fate of the Universe, and I could do it with no uncertainty at all. General relativity might be incredibly complex, but it’s the most powerful classical theory of all.
Ask Ethan: How Can I Travel Through Space Without Getting Into Trouble?
“Sometimes (usually Fridays after work) my friend Scotty beams me up to USS Enterprise for a ride around Sun following the orbit of planet Earth. The warp takes about 2 hours, so I guess our speed is very close to light speed, but not quite. During the ride I usually have a couple of beers, so when Scotty beams be back to my front door, my wife has difficulties believing me when I tell her that I was not at the local Pub…”
So, your friend on the USS Enterprise beamed you aboard, took you on a relativistic journey at impulse speeds around the Solar System, and brought you back to your starting point. You find that less time has passed for you than your family who remained on Earth, yet you’ve traveled a much greater distance. How does this all work? How much energy does it take, what’s the science behind it, and how do you get your family to believe you when you tell them what happened to you? Some basic advice: give them times in their reference frame, admit to the drinking you actually do, and if you go someplace unbelievable, take a photo!
I'm pretty young but I love astrophysics and I was wondering if you had any sort of list of resources (books, websites, etc) that explains and discusses quantum mechanics, the theory of relativity, and general theoretical physics.
Thanks for asking!! I’m glad that you’re interested in learning more about space and astrophysics, especially since you’re young.
I really really like PBS SpaceTime, they have a lot of SUPER interesting and very well done videos about all of the above mentioned topics (i’m actually probably gonna post some of their really good vids eventually). And when I say they have a lot of videos, I mean a LOT. And they’re all really really informative and very scientifically accurate. 15/10, would recommend.
If you want very in-depth articles, wikipedia is a relatively (pun intended) good source for reading about scientific topics - one of my friends jokingly said that wikipedia is where grad students record all the stuff they’ve learned so they don’t forget it in a few months (lol). Also a lot of universities have online notes and stuff posted, any website with a .edu ending is DEFINITELY trustworthy and likely to be accurate. I don’t have any book recommendations right now, but I’m going home for the weekend and I want to look at some if I get the chance. You can always find really good science books in the science section, right now I have “physics of the impossible” by Michio Kaku, and it’s a really cool book.
Let me know if you have any other questions, I’m happy to answer them and I really enjoy getting asks!
Some authors have suggested that fictional characters should not keep us too busy, since they are mere patterns of recurrence within a text, or mere functions within a plot. Though it is quite undeniable that characters are at least that, I am myself in favor of a more humanizing approach: villains and heroes have been created for us to suffer and celebrate them, for us to discuss them and speculate about their motives, their traits, their vices and virtues, etc. They are, certainly, textual patterns. But they constitute the kind of patterns that manage to trigger intense emotional responses; patterns against which we project our fears and desire.
There is also this magic about characters, which is actually a corollary of the projection phenomenon: they seem ‘others’ to us, yet they have their true genesis in the reader. Certainly, the reader is always embedded in a culture, and we can expect that, within the same culture, one reader’s experience of a fictional character be similar in many respect to another’s. However, our experience of a fictional character is bound to be also qualified by a number of particular aspects that are strictly personal. An already long history of literary criticism has proved how much room for disagreement there is in relation with heroes and villains.
I view those areas of disagreement - both between cultures and between individual readers - not so much as voids of uncomfortable uncertainty for the critic, but rather as the life repository of characters. These differences in experience make it possible for our famous heroes and infamous villains to become inexhaustible creatures, to be lived and relived endlessly. We must not, I think, be put down by uncertainty and relativity. The fact that the same villain can be experienced in different ways, depending on how we look at it, might just as well fill us with the enthusiasm of the connoisseur, who is always ready to try the same substance differently structured.
Villains in Our Mind: A Psychological Approach to Literary and Filmic Villainy, Enrique Calmara Arenas
Why are dark matter and modified gravity in such conflict?
“Most in the dark matter camp are convinced that the full suite of their successes to date mean that a better understanding of the nature of dark matter and improved computational power will lead to galaxy rotation falling into line. Similarly, most in the modified gravity camp are equally convinced that the failure of dark matter on these small scales is a catastrophe, and that the correlations they’ve discovered are a natural law that’s a precursor to a revolution even bigger than Einstein’s was 100 years ago. The great challenge for modified gravity is to reproduce the successes on large-scales of modern cosmology; the challenge for dark matter is to reproduce the details of the smallest scales correctly.”
The past month has seen a slew of papers out highlighting the tension between modified gravity and dark matter. Both recognize the same puzzles and problems with the Universe, and both ideas recognize that either one could be valid. In fact, if you look at the two greatest “crises” in gravity in the 19th century, it’s arguable that dark matter (Neptune) solved one, the Uranus problem, while modifying gravity (with Einstein’s general relativity) solved the other. Now in the 21st century, we have a whole Universe to explain, and while dark matter is definitely the leading theory, the idea of modifying gravity isn’t crazy. Moreover, it has a success that dark matter can’t match: on galaxy-scales and below. In the end, it will take a big step forward for a true victor to emerge, but here’s where the science stands right now.
Okay guys, Relativity is finally live! So let me explain for those of you who don’t know already. It’s a time travel webseries with a twist: there are ten episodes, but three different ways to watch them! Each character experiences these ten episodes in three different orders and to get the full experience of it, it’s best to watch it three times. (Don’t worry, it’s short!) I think it plays best if you do it from Candace’s POV, followed by Perry’s, then Erin’s. But you’re not bound to that! So watch the pilot and then you’ll get some options to keep going. Pick a character and it’ll put you in a playlist for that character. Also, you can just keep clicking “Follow [that character]”