What is the consequence of a 'Moving' Speedbubble?

[JustQuestin2004 he/him]

I am not a scientist, I probably never will be. So could someone smarter than me clarify this WOB for me?

Spoiler

Necarion

So a savant could?

Brandon Sanderson

A savant could totally do that. The problem is, things moving in and out of a speed bubble, there's a transference of energy. This is how we keep speed bubbles from irradiating people when light moves through them, right, red shift. And so there's a transfer of energy directly from the Spiritual Realm, which means that moving with a speed bubble, you're gonna run into that, and it's gonna be, it's gonna cause all kinds of problems, but it would be possible.

What exactly are the 'problems' with a moving speedbubble? Are they lethally dangerous and could there be a way around them?

Because if you could move with a Speedbubble around you, it'd be almost like if you were tapping F-Steel to other people. Bullet-time as it were. 

Then if you got a Twinborn with A-Bendalloy and F-Steel you'd get something really crazy.

[Treamayne]

6 hours ago, JustQuestin2004 said:

I am not a scientist, I probably never will be. So could someone smarter than me clarify this WOB for me?

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Necarion

So a savant could?

Brandon Sanderson

A savant could totally do that. The problem is, things moving in and out of a speed bubble, there's a transference of energy. This is how we keep speed bubbles from irradiating people when light moves through them, right, red shift. And so there's a transfer of energy directly from the Spiritual Realm, which means that moving with a speed bubble, you're gonna run into that, and it's gonna be, it's gonna cause all kinds of problems, but it would be possible.

What exactly are the 'problems' with a moving speedbubble? Are they lethally dangerous and could there be a way around them?

Because if you could move with a Speedbubble around you, it'd be almost like if you were tapping F-Steel to other people. Bullet-time as it were. 

Then if you got a Twinborn with A-Bendalloy and F-Steel you'd get something really crazy.

I'll explain this in two parts because in BoM we have two reference examples, and a related example from SoS:
 

Quote

SoS Ch 16:

Wax dug a handful of rounds from the pouch on his belt, then leaped out of the speed bubble. He felt an immediate lurch—as if the world had been upended—and heard a faint popping sound. The nausea hit him like a punch to the face, but he was ready for it. He’d ducked out of speed bubbles before.

BoM Ch 17:

Spoiler

 

The switch didn’t seem to have done anything. So, Marasi swallowed and burned a pinch of cadmium.

The cube began to vibrate in her fingers.

Then the entire coach lurched, rocking as if it had been struck by something very hard. Marasi hit her head on the roof, then was slammed back down onto her seat.

The horses screamed, but MeLaan somehow kept them under control. Within moments, the coach had pulled to a stop.

“What the hell was that?” Waxillium said, hauling himself up off the floor, where he had ended up in a jumble with Steris.

Marasi groaned, sitting up and holding her head. “I did something stupid.”

“How stupid?” Waxillium asked.

“I was testing the device,” Marasi said, “and used Allomancy.”

Wayne’s head appeared at the door a moment later, hanging down from above. “Was that a speed bubble?”

“Yes,” Marasi said.

“That jolt damn near killed the horses,” Wayne said.

“I’m sorry, I’m sorry.”

Waxillium helped Steris sit up. “What … what went wrong?” she asked, befuddled.

“Marasi used a speed bubble while we were moving,” Waxillium said. “We hit the threshold and towed her out of it, popping the thing and lurching us from one time frame to the next.”

“But, she used it on the train,” Steris said.

“Speed bubbles move with you if you’re on something massive enough,” Waxillium said. 

 

 

So, as an object passes the edge of a time bubble, parts of the object are in different time frames causing a "lurch" that Wax notes induces nausea in people (SoS). This is why a time bubble is stationary unless the Allomancer is on a sufficiently massive object (like a train) to support the entire bubble. This is also why objects passing the time barrier deflect (like bullets) as the change in time reference skews the angular momentum (think of a prism bending light). The smaller the object, the greater the induced change.
Partly, this is because (as the WoB notes) energy is either gained or lost (depending on if the object is speeding up or slowing down to match the new local time frame). WIthout a conversion of investiture into kinetic energy, light passing the time barrier would shift the same way physical objects due - inducing redshift or blueshift. . .

Quote

Ch 12: She produced a card and handed it toward him. “Please experiment with this further and send me word. Thank you. Now, if I can just figure out why there’s no redshift involved in speed bubbles…”

With that she wandered off the floor, leaving him befuddled in the middle of the dancing.

 Red and blue shift is a loss or gain in energy in light photons, inducing a change in wavelength and frequency. IRL, this is usually caused by a Doppler effect between moving objects (at astronautical speeds and distances - lightyears of distance and kilometers per second speeds or faster) or light being bent by changes in gravitational potential. With time bubbles, what would happen (without the induced conversion of investiture to energy) is "stretching" the wavelength as it passes the barrier would decrease the energy and frequency (blueshift) causing the blue part of the spectrum to "stretch" into UV and X-Rays while compressing the wavelength as it passes the barrier would increase the energy and frequency (redshift) causing the red part of the spectrum to "compress" into infrared and microwaves.

Basically, the WoB is saying that investiture is converted to photon energy as light passes the barrier, preventing the changes in wavelength, frequency and energy that would result in these shifts (and irradiating the people in the time bubble) - while anything more massive than a photon does not "add" enough energy passing the bubble to prevent the lurching effect.

As far as moving time bubbles are concerned, if the bubble moved with the Allomancer, then everything you pass would be lurched and affected as it passed through the bubble's barrier (like the shots that deflect coming in, and deflect again when leaving); or (as in the BoM Ch 17 example) if the coach was in the Cadmium slow-time bubble while still attached to horses not inside the bubble then death and mayhem would likely result as instead of a single lurch of the bubble popping as Marasi was pulled out, you would have an increase in pressure (is this the right word?) as horses not slowed down were killed trying to pull on a coach moving in a different time frame (both objects are moving at a given speed in meters per second, but the coach's "seconds" last longer and therefore are slower and "tug" on the horses trying to pull the bubble).

Hope that helps.

[JustQuestin2004 he/him]

1 hour ago, Treamayne said:

Hope that helps.

It kinda does, so if one were to be a Savant in Bendalloy and be able to move the Speedbubble around by anchoring it to themselves, they'd probably have to make it as small as possible and wrap it around themselves to avoid some of these problems. Does that make sense?