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I have seen references to this but I am constantly confused by how this is actually a thing. There was a video I watched that stated that in some situations 2

• akdev1l 3y ago
  this phenomenon is called “time dilation” you can search for it. Not trying to be a dick, just not qualified to explain this myself
  • nerdjon 3y ago
    Honestly that helps, just having a name to look for instead of somehow making a google search out of this will help.
    • 7thaccount 3y ago
      There is also time dilation from motion through space (motion through space + motion through time is equal to the speed of light, so as you speed up, your motion through time slows down) as well as time dilation due to gravity (like when near a black hole I think). I'm also not a physicist, but read some popsci books in my youth like "A brief history of time" from Stephen Hawking (it's written for normal people). That's probably the best book you'd want. He later wrote a more modernized version called "a briefer history of time" as well. They both cover time dilation from a high level iirc. Of course, to truly understand you'd need to learn the math. I'm looking forward to doing that during retirement in a few decades.
• belter 3y ago
  Maybe this one: "Does the Past Still Exist?" - https://youtu.be/GwzN5YwMzv0 https://youtu.be/GwzN5YwMzv0
  • nerdjon 3y ago
    I will watch that tonight, thank you.
• corndoge 3y ago
  https://en.wikipedia.org/wiki/Time_dilation https://en.wikipedia.org/wiki/Time_dilation
• dmoy 3y ago
  > I have seen references to this but I am constantly confused by how this is actually a thing. Shit, I studied this for a whole semster in physics back in the day, and even back then I was constantly confused by it. It is some unnaturally (to humans) weird stuff.
• johnla 3y ago
  It will forever boggle me but the way I sort of rationalize it is that speed basically borrows energy from time. Something like that. So the faster you go, the slower the time goes. So if you go the speed of light, you're taking so much time away that when you make a roundtrip, you're like 50 years into the future. That's a totally wrong explanation but it helps me sort out the effects and what to expect. If you fly quickly around the Earth, your watch is a tiny bit different than the stationary clock.
  • magicalhippo 3y ago
    AFAIK one can also consider the 4D velocity vector to have a constant lenght. Thus the faster you move in the spatial dimensions, the slower you move in the time dimension to maintain the constant length.
    • bloopernova 3y ago
      That's a helpful explanation, thank you.
    • bumby 3y ago
      Why must the velocity vector have a constant length?
      • CydeWeys 3y ago
        Now that's the billion dollar question, isn't it. But it's true.
      • numpad0 3y ago
        So to preoccupy your mind with simulation hypothesis and inter-node bandwidth estimation for the cluster we’re on. edit: wait, if the Vector4.magnitude == 1, are dense objects actually just fast/hot?
        • anticensor 3y ago
          With constant magnitude vectors, you can eliminate one of the numbers out of the motion simulation for each particle. Huge optimisation indeed.
• c54 3y ago
  FloatHeadPhysics does a really good job of explaining these kinds of things https://youtu.be/TJmgKdc7H34 https://youtu.be/TJmgKdc7H34
  • trey-jones 3y ago
    This is actually the guy that finally helped me break through into understanding (at least a little what's going on). Specifically about how the movement through space lengthens distances between objects (including atoms) and causes information (including light) to travel further, along the hypotenuse of a triangle, "in order to do stuff". "Doing stuff" includes observing things because of the light travel distance, but also biological processes, which involve eg. electrons moving from one atom to another. I didn't watched the linked video here (more relevant perhaps), but this was the one for me: https://youtu.be/Vitf8YaVXhc https://youtu.be/Vitf8YaVXhc
• irobeth 3y ago
  The way I've understood it is that everything which can 'move' in spacetime has to have a momentum vector with constant magnitude C (when expressed in the right units, C = 1) The faster you 'move' through space, the more you have to 'borrow' from the time component of the vector to maintain a magnitude of C That means your 'position in time' moves slower; and so for people who aren't moving as fast through space as you are, they appear to 'experience more time'
  • user_7832 3y ago
    What is the frame of reference, or is there even one, in this case? If you have one spacecraft moving in one direction at 0.5c flying by Earth, is the craft at 0.5c and experiencing "slower" time, or is Earth experiencing slower time? Or do they both experience the same thing as they're not accelerating wrt each other?
    • aidenn0 3y ago
      If they just pass by each other without changing speeds, each sees the other as experiencing slower time. For the case where one leaves and comes back, see the Twin paradox[1] which is resolved by the simple fact that to change speeds one must accelerate (or that the one who returns must have experienced at a minimum two different frames of references; one to leave and one to return). 1: https://en.wikipedia.org/wiki/Twin_paradox https://en.wikipedia.org/wiki/Twin_paradox
    • kijin 3y ago
      There is no independent frame of reference by which we can tell whose time is slower. From the spacecraft's frame of reference, Earth's time is slower. From Earth's frame of reference, the spacecraft's time is slower. Both are right. When we say that time is slower or faster on a spacecraft, the Moon, or an exoplanet of Christopher Nolan's, we are implicitly prefixing the statement with "From Earth's frame of reference..."
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• somenameforme 3y ago
  The concept of time dilation in general is actually pretty easy to explain, with the use of a relativistic starship! Imagine we create a ship that could constantly accelerate at 1g per second. What happens if you're on that ship, and start to approach the speed of light (relative to an observe back on Earth)? Well, some quite weird stuff - but you would not actually slow down! The speed of light is not a speed limit, like most people think of it. A human could easily travel billions of light years in a single lifetime. But it is true that nothing can ever be perceived as traveling faster than the speed of light. So how you can you travel billions of light years in a few decades, yet never be perceived as going faster than the speed of light - one light year per year? Simple - the universe, like a simulation filled with spaghetti code, starts to cheat, and changes the rate at which things start to move through time. An observer back on Earth would see your ship start to accelerate towards the speed of light, but then hit an insurmountable asymptote just before it. So if you traveled a million light years, they would see your trip taking a million years. But by contrast, only about 26 years would pass for you. So if you traveled a million light years out in our 1g accelerating ship, and then a million light years back, it would take you 52 years, but 2 million years would have passed on Earth. There's a calculator for such trips here. [1] This whole effect is called time dilation. Gravitational time dilation is just a special case of general time dilation, and is essentially the time dilation factor driven by the velocity needed to escape the gravitational well created by a body. So - more massive objects result in greater time dilation. It leads to interesting things like the core of the Earth actually being younger than its surface! --- A clear way this can be seen in real life (and to also emphasize this is in no way whatsoever an optical illusion) is with particle accelerators. Many emergent or unstable particles tend to decay rapidly. Yet when we accelerate them to speeds near light, we end up being able to observe them for orders of magnitude longer than their decay when at rest. It's because of time dilation. From an at rest observer, time starts to move more slowly for something moving rapidly. All of this should also be taken with a general 'for illustrative purposes' asterisk. I'm leaving out lots of things, like how as you approached the speed of light you'd start to experience length contraction. It's essentially another way that the universe cheats to ensure that everybody always perceives the speed of light as a constant. --- This has amusing and interesting social implications for Earth as well, if and when we become able of developing such technology - the rich and powerful, seeking immortality, will undoubtedly seek to thrust themselves into the future. Great setting for some sort of a sci-fi series, not only for those on Earth, but also for those setting out into a future that may not be exactly what they were hoping for. [1] - https://spacetravel.simhub.online/ https://spacetravel.simhub.online/
• hoorayimhelping 3y ago
  A Brief History of Time deals with this subject very well. It's a very easy and quick read, meant for a wide audience, not a technical one. It's readable in an afternoon. The concept that time is relative to the observer is where the theory of relativity gets its name from.
• aidenn0 3y ago
  All of those things fall out from the speed of light being independent of the speed you are moving at (i.e. regardless of how fast or slow or what direction you are going, you will always get the same answer when you measure the speed of light in a vacuum). The easiest one to explain is probably the most mind-bending: wheter or not an event is "simultaneous" depends on the frame of reference. You are sitting in a spaceship that has a large empty cargo bay. There is a lightbulb in the exact center of the cargo bay. If you turn the bulb on, it will hit the front and the rear of the cargo bay at the exact same time. This is true regardless of the speed the spaceship is traveling at (because the speed of light will always be measured as the same value). Now think of what happens from the frame of reference of someone on a planet as the spaceship is passing by. Since the spaceship is moving forwards, and the light moves in both directions at the same speed, the light will hit the back of the cargo bay slightly before the light hits the front of the cargo bay. The faster the spaceship is moving, the bigger this difference.
• Traubenfuchs 3y ago
  It‘s pretty simple. In places with high gravity, time goes slower. In fast moving containers (car, plane, spaceship), mass+gravity are also increased. This is the reason why shining a light forward on a moving train doesn‘t make the photons the speed of light + the speed of the train. The speed of the light emitted from the flashlight is slowed down by the mass/gravitation increase through the movement of the train. This way, travelling to the future is pretty easy by the way. Just travel in a vehicle almost at the speed of light and the outside worlds time will move faster (relatively), since you are slowed down.
• TaylorAlexander 3y ago
  Highly recommend the best-selling book A Brief History of Time!
• ldargin 3y ago
  It's a bit easy to understand that in the context of gravity, because gravity bends light down. If you shine a flashlight on Earth, that light is in free-fall, bending down. Time follows the same path, because the speed of light is fixed.