Nobody Cares! (Science & Tech Edition)

Dakota Tebaldi

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I'm still trying to wrap my head around what exactly is 75 times brighter than total darkness...
Well thing is, when we see a black hole, we don't actually see the black hole. What we see is the hot mire of loose material that is gathering around the black hole before it falls in, which completely surrounds and obscures it from view - although much of this stuff tends to gather in a rotating disk-like area around it (it's even called the "accretion disk"). This cloud of stuff speeds up and becomes more dense the closer it gets to the black hole - like water circling a drain, pretty much - and at a certain speed and density, it starts to give off radiation - heat, and then light. And then eventually radiation much more energetic than light - x-rays and gamma rays. But it's this stuff that was observed to increase in brightness so dramatically recently.
 

danielravennest

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Does that mean it's now a gray hole?
No, the hole, whose name is Sagittarius A*, is still black. What we observe is the "accretion disk" of stuff orbiting the hole before it falls in. Tidal forces around this hole are so strong, they can rip stars apart, and shred anything else that gets too close. The flare-up is likely a stream of ripped-apart stuff that hit the accretion disk at a significant fraction of the speed of light. That releases an enormous amount of energy.

 
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Argent Stonecutter

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Hawking radiation from a hole that size will be negligible.
 

danielravennest

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UPDATE: Hoppy Flew! Official flight video:


Elon's "Starhopper" test rocket wouldn't start yesterday, so they had to send in a mechanic to fix the "spark plugs" (notice his feet sticking out of the nozzle). They are going to try again today starting at 5 pm EST. I hope the man painted on the side is "number of missions flown" and not body count.





Technical version: there are three pairs of plasma torches in the engine. They are lit by an electric arc similar to a spark plug. The arc wasn't firing yesterday, apparently from a bad connector.

The pairs are for the fuel and oxygen turbopumps and the main combustion chamber. The torch flames in turn light the fuel mixes which drive the turbopumps, and the main burning in the combustion chamber. The turbopumps are needed to take the fuel and oxygen from 3 bars pressure (45 psi) in their tanks, to a higher pressure than in the combustion chamber. If their pressure wasn't higher, they would not flow in. What powers the pumps is burning a little of the methane and oxygen with the other to make a hot gas. Those gases then goe into the combustion chamber and finish burning with each other, so nothing is wasted.

 
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As of 6:43am ET today, the X-37B spaceplane’s fifth mission, dubbed the Orbital Test Vehicle (OTV-5), will have spent 719 days in orbit—just 11 days shy of a full two years circling the globe. The previous record was 717 days, 20 hours and 42 minutes, achieved just a few years earlier with OTV-4.

All we know about the 29-foot long spaceplane’s mission comes from the Air Force description, which is light on details, to say the least:

The X-37B Orbital Test Vehicle, or OTV, is an experimental test program to demonstrate technologies for a reliable, reusable, unmanned space test platform for the U.S. Air Force. The primary objectives of the X-37B are twofold; reusable spacecraft technologies for America’s future in space and operating experiments which can be returned to, and examined, on Earth.
 

Dakota Tebaldi

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I love this thing. I don't know what it's for or what it's actually doing, so I'm probably gonna end up regretting fanboying over it when it's revealed some day that it's like some gamma-ray weapon that's been assassinating people all this time; but until that day, I love it.
 

Dakota Tebaldi

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When I was RL little, I used to have this very-occasionally recurring nightmare that, like a few other of my dreams, has stuck in my memory for my whole life because of how deeply scary it was. I'd dream that I suddenly got the ability to fly - I could fly around anywhere, as fast as I wanted. And then I found out I could even fly in space without dying; and as a kid, I knew just enough about space to know about a couple of the really cool and awesome things that are out there in our galaxy, and I was so curious about them that I decided to use my new superpower to go and see those things first-hand and up-close. In the nightmares, though, I never got to reach my goals, because they would always end exactly the same way: I'd get maybe halfway or so to the destination object, and then have a sudden realization of where I was, turn around, and just look at this vast universe full of stars that all looked almost exactly the same and I had no idea which one was my home. I was lost in the abyss forever. And that moment was so utterly terrifying that I always woke up right at that moment.

Now, you have the chance to simulate my nightmare for yourself, using the amazing Space Engine software! Except that you can actually reach your destination eventually, and you don't have to experience existential horror when you turn around and realize you can't pick our Sun out of the starfield because you can just click the program off, or auto-return (you cheating bastard).

But the main point of this post isn't really to tell you about Space Engine, it's to tell you about this video about it and the horror of genuine perspective:

 

Dakota Tebaldi

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Hey guess what! Pyroclastic flows can continue flowing right over the top of a body of water, including the ocean. SURPRISE!

 
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