ELIF: how is time relative?
In: Physics
Another way to think of it is that your *perception* of time is relative. Similar to how, if we’re both sitting in a moving car that’s moving at 60mph, we would appear to be sitting still.
Your combined speed in space and time is constant, so if you move really fast through space time slows down for you.
Does it make sense to say that, if you moved at the fastest speeds possible (exaggerated example: speed of light or even much faster), then you’d be doing all sorts of stuff and time would barely have passed? For example, do a years worth of stuff (in our current standard of time) in a millisecond. Then that could mean that you would live almost forever or a really, really long time?
Haha well, time is still moving forward. So it will slow it down relative to the rest of your body.
Gravity affects time. The way we experience time on Earth, 24 hours in a day & 365 days a year, is not a universal constant. That is to say that another star system experience it differently. They age different, too.
In fact, your feet, being closer to the Earth, are younger than your head, which is farther from Earth and is affected by gravity (and time) differently.
Let us you stayed on Earth and your identical twin took a spaceship travelling at a very high speed on a long voyage of 20 years. Suppose both of you had synchronized identical watches that runs forever without any time loss.
When your twin gets back your watch will show 20 years have passed. Your twin’s watch will show it has been less than 20 years.
You measure time by seeing it fly.
Suppose there is a light in your living room. It is off. You turn it on, and you suddenly travel away from it at the speed of light. Just after you leave, someone shuts the light off.
That someone will see the light was on only for a couple seconds.
For you, the light will always be on (the image of when the light was on is traveling at speed of light, so are you).
Time is relative!
Imagine a space ship is about to leave on a voyage. It sets its clock to Earth time and by magic (or via a radio transmitter) the captain can always see both the earth clock and the ship clock. As the ship gets further from earth the captains can tell the difference between the clocks since light travels at a finite speed. At slow speeds the clock on Earth lags a little behind the ship clock, but they still go at the same pace. So far so sensible. The captain can tell how far away the ship is from Earth too.
Now lets say the ship is travelling away from Earth at a reasonable fraction of the speed of light. Things are a bit different now. The time the light takes to travel from the earth clock to the captain is increasing as the ship gets further from earth. Not only is the Earth clock lagging behind the ship clock but the increase in lag (over time) is noticeable. To the captain Earth’s time has slowed down. The impossible limit is when the light from the Earth clock never catches up with ship because the ship is going at the speed of light. To the captain the earth clock has stopped.
And then there is general relativity to complement special relativity (above) when gravity slows time down (give or take)…
I don’t know.. it all seems kinda off to me. Time dilation dictates that because of higher gravetational forces, the core of the earth is two years younger than the crust. But their both the same age. All gravity seems to do in my mind if affect rate of change, movement and reaction. Time is just a concept born of perception. It to me is a fixed dimension. It is always now, universally, everywhere. If you approached a time dilation phenomenon, then it exists in the same “time frame” as we do. But go inside it and your in the past or future (depending on which way you swing the gravity, higher slower, less future?) So now you have have mass and energy existing in two time lines at once, doubling matter and energy, and existing simultaneously in one overall timeline. Bs. The only thing that changes is perception, rate of change by way of movement or reaction.
I also am no genius, and am surely wrong and confused, but it’s what makes sense to me.. and it doesn’t matter a lick to my life if I have it wrong or right.
So, the speed of light is a constant. I’m not sure that ELI5-ing the reason for this is possible, beyond just saying that photons have a mass of zero. Anyway, say you build a clock that abuses this. It’s a tube with mirrors on the ends with a single photon inside of it, bouncing up and down. It measures an exact time based on the amount of bounces of the photon, since you know how long it is. This is all well and good.
Now, say you’ve got 2 people. One of them stands still, and the other puts the clock in his truck and speeds away. To the stationary observer, each time the light bounces, it has to move at a diagonal to reach where the other mirror will be as it moves. Diagonals are longer than straight lines, and the speed of light is constant, so the clock is now runny slow to the stationary observer. However, to the observer in the truck, the clock is relatively at rest, and the rest of the world is moving. For him, the light doesn’t have to take a diagonal, so his clock reads like it’s still correct, not slow. So, when the driving observer experiences as a second, the stationary observer will experience more than a second. In general, an observer that is moving and eventually stops will have experienced less time than someone who was still during this period.
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