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[wierd]

So, this hit my news feed today.

https://newatlas.com/physics/spacetime-wave-packets-laser-light-refraction/


I am tired, and not thinking clearly; Take this with a massive grain of salt--- But if the excitation packet moves irrespective of any matter in the path, that means it could be used very creatively. If such event can be created synthetically in a lab, then conditions that would produce them must happen in nature as well. Creating a dual detector, one that captures these raw space-time wave packets, and one that captures normal light wave packets, could enable a vastly more comprehensive means of measuring intervening gas densities, as well as measuring differences in local spacetime geometry (since the wave packets specified do not always take the shortest possible path).

A very interesting sensor could be made using this.

[Eric Blank]

Optical physics hurts my head, but I wonder if it could be used to analyze sea ice; by drilling one hole through the ice to insert a detector and then transmit packets at it through different angles, or move the detector around under the ice to analyze multiple data points as columns while only drilling one hole. But, probably a stupid expense for such a purpose.

[wierd]

Another item hit my news feed.

https://phys.org/news/2020-09-faint-principles-quantum-physics.html

Basically, they use wave-cancellation with wave prediction, to catch the "error" from the prediction, vs the weak signal source they are working with, and thus determine when the signal source has shifted to send data, even when the total number of photons is very very low.


This led to an idea in my head:


A number of years ago, another team demonstrated an "over unity" (ahem) LED.  In reality, it was an LED held JUST under the bandgap energy, so that thermal excitations were able to effectively contribute to the photon emission of the LED. That thermal energy was consumed in the process, and was added to the energy of the resulting photons, allowing the LED to emit more energy as photons than was driven into it as electricity-- thus "over unity".  I mention this work because--

Instead of using heat, you reduce the energy supplied to the LED so that it requires slightly more than what thermal noise introduces. (since we dont want noise.)  Instead, an additional (very weak) voltage is supplied via a classical antenna and ground loop to replace that source of energy. This picks up weak signals, and converts it into a light stream with very low numbers of photons-- exactly what this work uses, (and demonstrates how to tease a useful signal from.)

I think this could be used (since LEDs are always a fixed energy frequency, and thus easily processed this way as an input source) to enable radio frequency, or even highly attenuated electrical signals to be enhanced with the same concept. 

[Reelya]

Ambient energy devices are definitely interesting but an alternative is to use radioactive waste graphite control rods to make C14 diamonds which emit a tiny amount of power for several thousand years

https://www.wired.com/story/are-radioactive-diamond-batteries-a-cure-for-nuclear-waste/

[wierd]

Sadly, that technology wont work very well.  Several people much better than me have run the numbers on it, and the applications are just not feasible.  The resulting devices will be far too large, and produce very very small trickles of power, in addition to suffering all the problems a betavoltaic source suffers from, such as semiconductor junction breakdown from the high energy beta particle exposure. (basically, it causes dopant migration in the semiconductor, which essentially kills it.)

The idea gets rehashed every so often it seems, but it has been looked into already.  There's a reason people aren't making C-14 diamond battery wafers.

[delphonso]

What's all this time travel nonsense I keep hearing about? I hear there was a breakthrough in quantum theory?

[Starver]

There's a breakthrough in quantum theory, everyone. This could mean Time Travel!!!!

Yes, that's a time-travel joke. And I will not apologise.

[wierd]

No, some guy just gave some math proofs that causality is not necessarily violated by time travel.  While that *IS* a big deal, it is not what the media portrays it as.

Rather, it means that while you might create the time machine to go back in time to assasinate baby hitler, your attempt will always fail, your presence in the past was really your own timeline's history after all, etc..

Thus, there is never a condition where you succeed in killing hitler, and thus lose the impetus to create the time machine in the first place.  That paradox is prevented, because you cannot succeed in your stated goal.

[Starver]

(My post was a post-facto joke, ICYMI.)

It's always been the sanest[1] theory, to me, that for anything you go back and do you had already came back and done.

Unless the sum-total of mass and energy in the universe (including the negative bits) is zero, in which case there's nothing to stop whole-reality branching to pick up any changes due to interference. (But also nothing stopping any branching on every single quantum 'decision' ever made, so doesn't even need time-travel to end up with no Hitler, or possibly twin-Hitlers.)

[1] Which doesn't guarantee it's the most correct.

[McTraveller]

Don't forget, if you want to time travel, you also need to space-travel.

I mean to go back to Earth in 1945, which is 75 years ago, you have to travel roughly 2 x 10⁵ m/s (speed of sun around galactic center) x 7.5x10¹ years x 3.1 x 10⁷ seconds/year or about  4.6 x 10¹⁴ meters.

[delphonso]

No, some guy just gave some math proofs that causality is not necessarily violated by time travel.

This is what I came here for. Thanks wierd.

Basing this more on fiction than anything (but at this point, what's the difference) I prefer the "always was" type of time travel - Kyle Reese goes back in time to protect John Connor('s mother) but becomes his dad in the process. Who was the original father? Doesn't matter, that has been changed and not it always was that Reese was his father.

Don't forget, if you want to time travel, you also need to space-travel.

I mean to go back to Earth in 1945, which is 75 years ago, you have to travel roughly 2 x 10⁵ m/s (speed of sun around galactic center) x 7.5x10¹ years x 3.1 x 10⁷ seconds/year or about  4.6 x 10¹⁴ meters.

I have yet to see any fiction deal with this adequately. I suppose if we have that sort of travel capability, we would more likely explore the stars rather than go back and get revenge on history's greatest monsters.

[ZBridges]

Don't forget, if you want to time travel, you also need to space-travel.

I mean to go back to Earth in 1945, which is 75 years ago, you have to travel roughly 2 x 10⁵ m/s (speed of sun around galactic center) x 7.5x10¹ years x 3.1 x 10⁷ seconds/year or about  4.6 x 10¹⁴ meters.

Can gravitational fields also allow for time travel, since time dilation can occur through two objects' different velocities relative to each other, and also through two objects' gravitational differences relative to each other?

[wierd]

wormholes do both, so the answer is yes.

[ZBridges]

For time travel in the positive or negative direction or either?

[wierd]

wormholes are bidirectional