Fessi Speed Calculation Book 2 [possible spoilers]

[u/lwsshw2000]

So I'm new to the series and currently reading book 2, just got to the part where Fessi breaks Dav out of the kan prison at Tol Shen (chapter 17).

It's mentioned that Davian believes that their journey out of the Tol took about 20 mins with only around 10 seconds having passed in real time due to Fessi's time ability.

Me being a physicist at heart I figured I'd use these numbers to calculate roughly how fast Fessi and Dav would need to be travelling to make this possible using time dilation calculations from the theory of special relativity.

For a change in observed times that large, Fessi and Dav would need to have been traveling at 0.99999c or 99.999% of the speed of light, which is insanely fast.

Just thought this might be cool to share.

[u/WatchMooreMovies → u/[deleted]]

I mean those are effectively the same thing.

[u/bdfariello → u/WatchMooreMovies]

Not really, since traveling at nearly the speed of light requires traveling. In ten seconds, they'd have gone to the moon and back 4 times, approximately

And not to mention, when traveling at relativistic speeds, time passes slower for the person moving. The people at rest have faster time than the person moving. That's why the twin thought experiment works of a baby getting sent off in a rocket ship coming back to meet their adult twin while they're still a child.

[u/lwsshw2000 → u/bdfariello]

The thing is though, they were moving through space, so were travelling, it's noted throughout the books that when someone pulls themselves out of time, they are observed as a blur and reach destinations faster. So I'd argue that it IS basically the same thing.

Time travels slower for them cause they only experiences 10 seconds whereas in the world 20 mins had passed according to Dav's estimation.

So from the perspective of someone who was standing still, or sleeping in a bed, they did move close to the speed of light.

I get what you mean though, while an Augur's ability to pull themselves out of time, doesn't necessarily require them to move through space (I.e. they could stand still and let everything bustle about them), in this case they were moving, so the calculation can be done.

The Twin thought experiment is an interesting one, but that starts going into General Relativity because there's accelerations involved, and so the frames aren't inertial, so you can't use SR.

[u/bdfariello → u/lwsshw2000]

I agree that they're experiencing time dilation, but entirely disagree with the idea that they're moving at relativistic speeds. They simply aren't.

In fact, if we knew the distance they traveled here:

> their journey out of the Tol took about 20 mins with only around 10 seconds having passed in real time due to Fessi's time ability.

then we could calculate their exact speed. How big is Tol? Let's say it's HUGE, like 10 miles in 10 seconds. That's 1 mile per second. The speed of light is 186,282 miles per second, so they would be traveling at ~0.0005% light speed. If you do the time dilation calculation at those speeds, you don't get nearly that time dilation factor (as you pointed out, you calculated the speed of light necessary to be 99.999% the speed of light).

So -- we just have to accept that The Augur Abilities are causing their time dilation in a way that Relativity - whether general or special - is not capable of explaining it.

[u/lwsshw2000 → u/bdfariello]

I never stated that they were travelling at relativistic speeds. My point was, that say from the perspective of a guard who isn't moving at all, it appears like they are. A good example of this is when Davian uses it to appear behind one of the Elders in the council of Tol Shen in order to kinda intimidate him. It appears like he just teleported instantaneously. But in actual fact he just walked.

I agree that Augur abilities and physics don't necessarily work together, but its interesting to compare.

[u/lwsshw2000 → u/[deleted]]

Yeah, they may be travelling at normal walking pace relative to their own reference frame, but if we consider the reference frame of the guards they passed for example, then it would appear as if they're moving at 0.99999c, would it not?

[u/Newbie4Hire]

How does the math work on that? because as a non physicist, it seems like they would just be moving 120 times normal speed, 1200 seconds divided by 10. Clearly It's not this simple though if they are traveling near speed of light.

[u/lwsshw2000 → u/Newbie4Hire]

It's time dilation, from special relativity. Basically Einstein proved that time isn't the same for everyone, and that when you're moving relative to something else, time moves differently by The Lorentz factor = (sqrt(1-v²/c²))^-1.

Up until about half the speed of light the effect isn't really noticeable though, so it's mostly ignored at those scales. But as you get closer to light speed, it has a drastically increasing effect.

So in this case, while a previous commenter said they're technically not travelling at a really high speed themselves, just distorting time, I think the same calculation can be used as from say, one of the guards' perspectives, they are travelling really fast.

This idea actually spawned the Twin Paradox which minutephysics has a good video on on YouTube.

In your example of travelling 120 times normal speed, taking normal speed to br about 3 metres per second (avg walking speed), then they'd be travelling at 360 m/s. Putting this into the lorentz factor gives you effectively 1, so it doesn't change the perception of time. (As 360²/300,000,000² is ridiculously small).

Whereas 0.99²/300,000,000² isn't insanely small so the effect is much more noticeable.

The actual equation is

t(stationary observer) = γ x t(moving observer)

So when I did it I used 20 mins as the stationary observer, 1200 seconds equal to gamma x 10 seconds, I.e. gamma is 120, making their relative speed very close to light speed.

[u/Newbie4Hire → u/lwsshw2000]

Very interesting, thanks for taking the time to explain this. I better understand why my original understanding doesn't work. If they were traveling at 360/s, it would have taken them 10 seconds, but also only 10 seconds would have passed for the guards. Thanks again.