Sasha
@Sasha@lemmy.blahaj.zone
Yes, that Sasha
- Comment on your mom falls significantly faster than g 2 weeks ago:
I’ve only ever done QFT in curved spacetime, but I don’t see any reason why you couldn’t do EM, it’ll be a vaguely similar process. I never actually dealt with any scenarios where the curvature was that extreme, and QFT in a curved background is kinda bizarre and doesn’t always require one to consider the specific trajectories, though you definitely can especially if you’re doing some quantum teleportation stuff. In my area it’s simpler to ignore QED and to just consider a massless scalar field, this gives you plenty of information about what photons do without worrying about polarisations and electrons.
It’s been a long time since I did any reading on the geometric optics approximation (in the context of GR this is the formal name for light travelling on null geodesics), but for the most part it’s not something you have to consider, even outside of black holes the curvature tends to be pretty tame (that’s why you can comfortably fall into one in sci-fi), so unfortunately I don’t know of any phenomena (in GR) where it’s important. QFT in curved spacetime generally requires you to stay away from large curvatures, otherwise you start entering into the territory of quantum gravity for which there is no accepted theory.
Outside of GR, it breaks down quite regularly, including I believe, for the classic double slit experiment.
- Comment on your mom falls significantly faster than g 2 weeks ago:
On that first point, calculating spacetime metrics is such a horrible task most of the time that I avoided it at all costs. When I was working with novel spacetimes I was literally just writing down metrics and calculating certain features of the mass distribution from that.
For example I wrote down this way to have a solid disk of rotating spacetime by modifying the Alcubierre warp drive metric, and you can then calculate the mass distribution along the radius. I did that calculation to show that such a spacetime requires negative mass to exist.
- Comment on your mom falls significantly faster than g 2 weeks ago:
Yeah, once you add in a second mass to a Schwarzschild spacetime you’ll have a new spacetime that can’t be written as a “sum” of two Schwarzschild spacetimes, depending on the specifics there could be ways to simplify it but I doubt by much.
If GR was linear, then yeah the sum of two solutions would be another solution just like it is in electromagnetism.
I’m actually not 100% certain how you’d treat a shell, but I don’t think it’ll necessarily follow the same geodesic as a point like test particle. You’ll have tidal forces to deal with and my intuition tells me that will give a different result, though it could be a negligible difference depending on the scenario.
Most of my work in just GR was looking at null geodesics so I don’t really have the experience to answer that question conclusively. All that said, from what I recall it’s at least a fair approximation when the gravitational field is approximately uniform, like at some large distance from a star. The corrections to the precession of Mercury’s orbit were calculated with Mercury treated as a point like particle iirc.
- Comment on your mom falls significantly faster than g 2 weeks ago:
Yeah it would fair point, I’ll be honest I haven’t touched Newtonian gravity in a long time now so is forgotten that was a thing.
There’s a similar phenomenon in general relativity, but it doesn’t apply when you’ve got multiple sources because it’s non-linear.
- Comment on your mom falls significantly faster than g 2 weeks ago:
Possibly?
A bowling ball is more dense than a feather (I assume) and that’s probably going to matter more than just the size. Things get messy when you start considering the actual mass distributions, and honestly the easiest way to do any calculations like that is to just break each object up into tiny point like masses that are all rigidly connected, and then calculate all the forces between all of those points on a computer.
I full expect it just won’t matter as much as the difference in massed.
- Comment on your mom falls significantly faster than g 2 weeks ago:
I actually thought the answer might be never, but a quick back of the envelope calculation suggests you can do this by dropping a ~1kg bowling ball from a height of 10^-11m.
This is an extremely rough calculation, I’m basically just looking at how big a bunch of numbers are and pushing all that through some approximate formulae. I could easily be off by a few orders of magnitude and frankly I didn’t take care to check I was even doing any of it correctly.
10^-11m seems wrong, and frankly it probably is. But that’s still 1,000,000,000,000,000,000,000,000 times further than the earth moves in this situation.
- Comment on your mom falls significantly faster than g 2 weeks ago:
This is not correct, the force on the objects is the same sure, but the accelerations aren’t so you can’t calculate them both in one go like this.
- Comment on your mom falls significantly faster than g 2 weeks ago:
If anyone’s wondering, I used to be a physicist and gravity was essentially my area of study, OP is right assuming an ideal system, and some of the counter arguments I’ve seen here are bizarre.
If this wasn’t true, then gravity would be a constant acceleration all the time and everything would take the same amount of time to fall towards everything else (assuming constant starting distance).
You can introduce all the technicalities you want about how negligible the difference is between a bowling ball and a feather, and while you’d be right (well actually still wrong, this is an idealised case after all, you can still do the calculation and prove it to be true) you’d be missing the more interesting fact that OP has decided to share with you.
If you do the maths correctly, you should get a=G(m+M)/r^2 for the acceleration between the two, if m is the mass of the bowling ball or feather, you can see why increasing it would result in a larger acceleration. From there it’s just a little integration to get the flight time. For the argument where the effect of the bowling ball feather is negligible, that’s apparent by making the approximation m+M≈M, but it is in this system an approximation.
I could probably go ahead and work out what the corrections are under GR but I don’t want to and they’d be pretty damn tiny.
- Comment on Scientists dismayed as UK ministers clear way for gene editing of crops - but not animals 2 weeks ago:
Depending on the way it’s modified, I think there’s some environmental risk particularly for soil erosion and potentially cross breeding with non-modified crops.
I don’t think these should stop us from making better food sources, but it does concern me because there isn’t much corporate incentive to adequately test for these things.
- Comment on Australian government pilots Microsoft Copilot with mixed results. 3 weeks ago:
Inb4 robodebt 2.0
- Comment on The Most Loved Digital Audio Streaming Platforms. 1 month ago:
Just pirate, it’s better than paying these companies to rip off artists. Support your favourite artists directly, streams are basically worthless compared to other forms of income like merch.
- Comment on Why is space 2 dimensional? 1 month ago:
Best video you’ll ever see on the topic imo (and very short)
- Comment on SGVsbG8sIFdvcmxkIQ0K :) 1 month ago:
Why does this kinda look like Doug Walker?
- Comment on Thank you! 2 months ago:
Coffee is just a bean soup
- Comment on Gina Rinehart urges government to ‘drill, baby drill’ and build Israeli-style ‘iron dome’ in northern Australia 2 months ago:
What a horrible waste of oxygen
- Comment on How to know you'll turn out trans? 4 months ago:
Yeah, fair enough. Best of luck, you deserve happiness and I’m rooting for you
- Comment on How to know you'll turn out trans? 4 months ago:
I’m so sorry that you had such a horrible journey, but I’m so proud of you for making it this far
- Comment on How to know you'll turn out trans? 4 months ago:
HELL YEAH!!! I’m so goddamn happy for you!!!
egg_irl was a big part of it for me too, it’s an awesome place
- Comment on How to know you'll turn out trans? 4 months ago:
That’s sort of my experience, but I’ll also add that if you don’t know that being trans is a thing then it’s possible to just not recognise what it is or that you can do something about it.
- Comment on How to know you'll turn out trans? 4 months ago:
The real sign of being trans is if you go to egg_irl and start relating to almost everything lol (sorry I haven’t got a clue how to link communities).
Tbh there’s no magic bullet to be sure, but if you fantasize about being a different gender that’s a pretty big one, cis people don’t do that.
- Comment on How to know you'll turn out trans? 4 months ago:
Pretty sure my inability to use a chair correctly is what makes me bi, thinking everyone is hot is just a side effect
- Comment on How to know you'll turn out trans? 4 months ago:
I am trans and I can say I’ve never felt like I was in the wrong body, I think most of the time that’s just a relatively flawed way to describe an experience that can’t truely be understood unless you’ve experienced it.
Of course, no one has the same experience with these things. For me it’s mostly just been that something felt like it was missing, and I fixed that when I began to transition. The main thing for me was how much happier the internal changes made me, estrogen changes how you experience emotions and being out to my family had a similar effect.
When it comes to “signs” the biggest was just being envious of people who had the freedom to express differently than me. I can confirm that it’s a gradual realisation, though honestly most of that was overcoming shame and internalised transphobia.
- Comment on The Ute Mountain Ute Tribe will construct one of the largest solar farms in the U.S. 8 months ago:
This post left me very confused for a good 30 seconds, why would a bunch of car enthusiasts install solar panels? … Oh
- Comment on YouTube Premium announces 100 million subscribers 9 months ago:
Use smart tube
- Comment on [deleted] 9 months ago:
I know someone who religiously follows it, because he constantly discloses when he’s doing it (all the time). It’s very real
- Comment on Fake news, fake penis... 9 months ago:
Power move I’d totally do this on purpose
- Comment on My thoughts on the Australia Day date 9 months ago:
A nation built on blood and genocide, wars fought with Aboriginal soldiers who came home to no thanks to be treated like dirt.
I won’t have pride in a country that won’t face its own racism, I won’t have pride in a country that won’t face it’s unjustifiable founding.
Always was, always will be aboriginal land.
- Comment on My thoughts on the Australia Day date 9 months ago:
Maybe it’s just me, but I don’t think we should keep Australia day while there’s still so much injustice for the first nations people.
We can have it back when we’ve actually built something worth celebrating.
But again, maybe that’s just me.
- Comment on Gen Z is choosing not to drive 9 months ago:
As someone who has absolutely no desire to ever own or drive a car, I’m getting my licence based purely on the off chance that I might need to anyway (but I’d probably just hire for a day).
- Comment on OpenAI Quietly Deletes Ban on Using ChatGPT for “Military and Warfare” 10 months ago:
I can’t spell, don’t blame me for relying on an ordinarily quite useful tool.
