I love the blender game engine. To me, it's as nostalgic as a favorite video game from childhood. I spent countless hours building little projects as a kid. I was really sad when they removed it in v2.8
Now as an adult, I can see why they removed it. It didn't make sense to put resources into it.
I'm really happy about the UPBGE project. It doesn't compare to the capabilities of Godot, but that's okay. It just makes me happy that someone else cared about it enough to pour time into it.
I recently came across some notes from a lecture I went to at Los Alamos in 2013 where the lecturer (Steven Brumby) said "it's out of fashion to call it AI now so I guess this is machine learning" .
It's good to see an old NASA page that hasn't been destroyed by the "web modernization" pushes. I was looking for information on human landing site selection recently and the bitrot due to "modernization" there is extreme. I also saw a lot of this from the inside while working at JPL. Insufficient care is taken to preserve old pages and URLs are rarely preserved in upgrades. (And this story is a fun one -- I think I learned about it in a Radiolab podcast which is worth a listen)
Edit: Oh shoot just realized this page is by Dave Williams. I worked with him on MoonDiff. He's great. He also maintains pages about lunar impact flashes.
I don't get how they know they have exactly one in there. I mean they're measuring the magnetic field but how on earth do you make sufficiently precise measurements to detect a single particle!?!
The simple explanation: The positrons fly around the trap center. In the z-direction, this is a simple "up and down" oscillation. There are electrodes in the top and bottom of the trap called the "end-caps". The end-caps are connected to each other with a large resistor (technically, a coil forming an LC resonator with the parasitic capacitance, but on resonance it looks like a large resistor).
When the positrons are at the top, they attract negative charges into the top end-cap. This is called an "image charge". When the positrons are close to the bottom end-cap, the image charge into bottom end-cap. This forms a current, the "image current". The more positrons you have, the larger the image current.
Since the image current (on the order of femtoamperes) has to flow through the large resistor, it is turned into a voltage that can be amplified and measured by cryogenic amplifiers. But it has a second effect: The voltage "back-acts" on the positrons, damping their motion. If you have more positrons in the trap, this damping gets stronger, because each positron experiences the back-action of all other positrons.
In the paper, you can see pictures of the driven axial motion, where you take an RF excitation and sweep the frequency over the resonance, recording the positrons' amplitude as a response. The more positrons you have, the "wider" this resonance, because of the damping effect.
As you reduce the number of positrons by doing a "dip" (making the trap really shallow, hoping that some, but not all, positrons escape), you can see the width getting smaller and smaller in discrete steps. That's how you know you are dealing with individual particles.
I haven't worked on Gabrielse's setup, but I have worked on other, very similar (better, ha!) experiments 10 years ago. I don't see what's so special about this trap, but putting antimatter into it always makes for a nice headline.
> In order to determine ωz and the number of trapped
positrons, the axial oscillation of a positron is driven with
oscillating potentials applied to the trap electrodes. The
frequency of the drive ωd is swept through resonance with
ωz.
> For the center-of-mass axial motion of
more than one positron, the damping (and hence the observed signal width) increases in proportion to the number of particles. A confirmation that only one positron
is trapped comes from spin flip observations that are discussed presently
They let it go and listen for the pop? Let it fall from the magnetic containment and you should see a predictable emission as it collides with some normal matter. Detecting single photons is what detectors are all about.
I think this is a fascinating technology. I wonder if it is currently energy positive (so that we can engineer it into a functional source) or at least if it can be extended to be captured in bulk (antimatter rockets!).
Energy positive? That made me laugh. Making antimatter is more energy negative than building a 747 out of gold. They burn through enough power to light a town in order to capture a literal handful of antimater particles.
In a rocket it would not be useful. It has the energy but would emit it as all sorts of highly penetrating radiation rather than hot gas for a rocket nozzle to turn into thrust.
One particle has enough energy to, maybe, if it hit a speck of dust it might result in a perceptible twitch of that speck of dust... if you were watching the spec under a good optical microscope.
I know you’re being facetious but a 747 made out of gold is going to be ~24 billion dollars if you are doing a weight conversion. A 747 by itself is ~$400 million. The entire CERN annual electricity cost is $~25-50M.
No way this experiment had that kind of funding. I would bet the experiment itself had a few million dollars in funding at most + another few for the salaries. Max 10M all in. Probably closer to 2-5M. Expensive but not prohibitive like a 747. But for a single particle.
Scaling up no one really knows because we only do this for single particles and that’s really inefficient. At scale it’s unclear what it could look like.
But electrons/positrons cannot become fuel. Positrons repel each other. So to make any real amount of antimater, beyond counting individual particles, you need anti-protons to keep the positrons happy and containable at scale. Creating the sort of anti-hydrogen one might want to collect as fuel, THAT requires golden 747s of energy.
I could be wrong but my understanding is that’s purely a function of our technological limitations in how we create antimatter, not in the fundamental energy required. Our tech of a particle acceleration is ~1e9 times less efficient than the actual energy required because most of the energy is lost, not converted. A gram would be $~6.2M/gram if we could get to 1% energy conversion efficiency. No one bothers of course to even try because it’s not worth it - expensive, difficult, and huge energy losses. Fusion reactors for space ships will probably come before antimatter gets cracked as a battery source.
In this case they are using 22Na that produces positrons. A quick search says that they cost like $50-$300. (I guess I'm in yet another list now.) I used one in the physic lab a few years ago. They are good enough to get a few blips in a Geiger counter or something similar.
I agree that if someone wants to make enough antiprotons and positrons to make enough antimater to power a rocket, the cost is prohibitive and there is absolutely no hope to make it cost efficient.
Positrons aren’t useful because they annihilate to produce gamma rays, which can’t be contained. However, anti-proton annihilation produces a bunch of particles, including pions, which could be contained in a magnetic bottle and directed for thrust.
I expect a future Bonneville speed run to get airborne and set some record. Could still qualify as fastest production car; even with no wheels on the ground.
There was a brief moment where programs had decent built-in help you could search to easily find where stuff was in menus. Didn't need a billion parameters or a giant faraway data center...
Or, better, the global menu search. Intellij's shift+shift shortcut is great.
The premise of this article initially appears to be that counter to common opinion, work is profitable and it's not all about investment / entrepreneurship.
But then through the course of tedious and somewhat pompous paragraphs (I only read 5 before I started skimming so let me know if I missed something) the point seems to bend towards "work hard to get a foothold so you can own stuff and then you'll make real money" .
It did nothing to change my opinion of our system where labor earns a pittance and all real wealth comes from the lottery of birthright, corruption, picking the right stock, or getting lucky in entrepreneurship.
(What's all this stuff about grades??? Does somebody think grades matter??? Maybe I'm out of touch because I got my PhD before really starting the career grind.)
> It did nothing to change my opinion of our system where labor earns a pittance and all real wealth comes from the lottery of birthright, corruption, picking the right stock, or getting lucky in entrepreneurship.
What is real wealth in this scenario? I had no birthright, involvement in government corruption, nor did I pick the right stock or start a company. Just boring old S&P 500 and not blowing money on really dumb stuff or making mistakes. Which is harder than it looks, but if your perception is real wealth = multi-digit millions then yes sure you have to get lucky. What is surprising or interesting about that? Rare thing is rare, else it wouldn’t be of value.
What's interesting is that 50 years ago, we had a system where if you worked hard for 30 years, your career would make you wealthy. Now, that is impossible, because structural inequality (stock buybacks etc) give all of the profits to the CEO, board, and shareholders rather than to the employees. You have to play the stock lottery and get lucky if you want to afford a house in an HCOL area.
In short, careers used to be inherently profitable, but now we have a system where only gambling is truly profitable.
It’s not impossible - I did it. Who cares about affording a house in a place where houses are expensive? Relocate. It’s not up to society to babysit your life. I want a giant house in San Francisco or in Monterrey. I’m not entitled to that and neither is anyone else.
Your premise about the stock lottery doesn’t make sense. First just buy index funds. Second the CEO and board and shareholders (that’s you) rise or sink with the fortunes of the company. If the company goes bankrupt you lose your money but so do those groups.
> If the company goes bankrupt you lose your money but so do those groups.
No, generally speaking, the CEO gets a golden parachute. E.g. Adam Neumann got 1.7 billion severance for being a douchebag cult leader and bankrupting wework.
I'm not complaining about my situation-- I'm doing really well. Making $207k / yr and living at the beach in LA. I'm just sad that we've switched from a system where normal workers can make actual money to a system where hyperfinancialization means a leisure class at the top, selected by lottery, has all of the real wealth and power.
Donate money to workers and be the change you want to see in the world. Leave extra large tips? Change starts with you. Stop complaining and being a baby and saying nobody can get rich while you live in what many consider to be a literal paradise with an income that correspondingly allows you quite a bit of freedom and high quality life. If you don’t want to do that move to Nebraska and buy a house and prove to yourself you can buy a house. You’re not entitled to buy an “affordable” house in the place almost everyone in the world wants to live.
The example you gave isn’t a good one. And second the CEO is often paid in shares to avoid taxes on income. If the shares are worthless, well you can do the math.
Like I said, I'm privileged and happy. It's my teacher friends, service industry friends, and factory workers I feel bad for. I just wish the USA was still a country where workers were well compensated, like they were from 1950 through about 1990.
Well you can voluntarily pay them more. Nothing stopping you. Buy American made only products or buy products only from American companies and pay more like I do. Put your money where your beliefs are. Where do your pots and pans come from? Lodge? Smithy? Duparquet? I do. You won’t catch me dead buying shit from non-American companies unless there are no realistic replacements. I’m not kidding, by the change you want to see in the world.
The 1950s - 1990s (not sure the time period is exactly correct) primarily corresponds with the post-war boom in which the US has 25% or so of global production and GDP. Those days aren’t coming back. We can work on tax policy of course, but there are too many people and too much competition for resources. In addition to tax policy reform we need governments to get back to basics, stop hiring dotards, and reduce the NGO and non-profit complex siphoning money away with crappy results. We can do better. Let’s do it. But let’s do it across the board and both put our money where our mouth is.
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