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ex-wife otm

Ha, yeah. It's kind of ridiculous, right. He's a particle physicist so I never met him, but I know ppl who have. Tbh it kind of surprises me that this sort of thing doesn't happen more often. Many male physicists (especially toward the maths/high energy theory end) are a little, ahem, wet behind the ears. I mean even the person who told me this story struck me as the kind if person to whom it could happen.

He sounds like he is safer in prison than in the real world.

I like that he has published papers with the prison as his affiliation: http://physicsworld.com/cws/article/news/2012/nov/22/paul-frampton-hit-by-56-month-drugs-sentence

hay caek is "exotic matter" in this any more than subtle handwaving? What are my chances of actually getting to alpha centauri in my lifetime? And does FTL always and irrevocably imply time travel (which is problematic obviously) or is there any kind of loophole there?

http://io9.com/5963263/how-nasa-will-build-its-very-first-warp-drive?post=54599539

"exotic" is a term of art in particle physics, so it's a weird choice, but they don't give any indication they are actually talking about exotic matter. i think here they just mean regular mass that is converted into energy by nuclear fission or whatever, yielding e=mc2.

the point with this thing, afaict, is that it does not involve faster than light travel. imagine spacetime is a living room rug. you can't walk across the rug at FTL, but given preposterously contrived circumstances, someone else can stretch the rug in such a way just that your location changes in a way that is equivalent to moving (and perhaps a very long way very quickly).

key quote: "Mathematically, the field equations predict that this is possible, but it remains to be seen if we could ever reduce this to practice."

also i have no idea if the field equations even predict this is possible. i skipped gen rel (via not being clever enough).

the point with this thing, afaict, is that it does not involve faster than light travel.

but it still effectively means a signal could propagate faster than light. no?

ha, i guess. god i never understood this stuff.

is anything faster than aaron lennon over five yards tho

where is layman's maths-free guide to GR. anyway i guess this is mostly bullshit, no trips to stars near or far in my or maybe anyone's lifetime, sadface. what a senseless waste.

cheer up, maybe the onset of catastrophic climate change will focus minds on ways to get out of this solar system pronto

dreaming of a railgun that can shoot us at alpha centauri

c'mon get real, even ignoring acceleration the stars are out of reach without ftl. intra solar system railgun might be a winner, first we need space elevators to circumvent enormous expense of getting into orbit only by riding giant exploding tanks of propellant.

i'd settle for a railway that got me to galway tbph

now let's be realistic

*joke about galway being behind the times like light from distant stars*

it's not behind the times but it is beyond the pale

someone else can stretch the rug in such a way just that your location changes

Mrs. Whatsit?

a signal could propagate faster than light. no?

my understanding is that theory allows and experiments have supported the idea that certain kinds of state information can be exchanged between atoms that are indefinitely remote from one another, and this exchange may occur more quickly than a photon could travel between the two atoms. nb: i am not a phycisist.

If yr talking about epr paradox/aspect experiment then yeah there is some kind of weird action at a distance, but no information is propagated, just the same random outcome occurs at the two remote locations. Like rolling two dice light years apart and they always come up the same, spooky but you can't communicate anything.

makes me feel better to know that every time I lose at craps some space alien dooder also just like a quadrillion zeeprix a billion light years away

乒乓 quantum entangled with a space alien dooder!

I'd do it again too

quantum entanglement is a like a special std where you both get whammies at the same time

our maths are inadequate as yet

I've got another space question inspired by this gif that Dayo posted:
http://i.imgur.com/Z7FpC.gif

At first I thought it was wildly out of proportion because I thought the sun was waaaaay bigger than Jupiter but I internet-sleuthed and it looks like the sun's diameter is only ten times bigger than Jupiter's?
So gravity's gotta be both pretty intense and delicate, huh? Like, if I were in space and I opened a bag of peas, would my gravitational pull force them to orbit me? Or do all the nuclear reactions going on in the sun make it denser than the planets in order of insane magnitudes?

Jupiter is way less dense than the other planets in our galaxy iirc

Jupiter's mass = 0.0009546 Solar mass

most of that mass concentrated at the center, which is holding all those gases in

just like uranus

lol

there should be more songs about gas giants

Is there any rule of thumb for figuring out what's the biggest thing I could get to orbit around me in space?

you mean space, far enough away from any other objects that their gravometric pull doesn't overwhelm your own, right? I am thinking that even at a far distance, the sun is going to exert a greater pull than your own mass

the average density of the sun and jupiter are actually about the same, just a little be denser than water. the earth is 4ish times denser than either. that's on average. and "on average" is all that matters for gravity. the earth doesn't notice that the middle is denser than the outside. all it cares about is the average value, i.e. the total mass of the sun. (although it's true that at its centre the density of the sun is much higher than basically anywhere else in the solar system.)

so anyway, jupiter and the sun are the same density, for gravitational purposes. and you're right that you're right that jupiter is only ten times smaller than the sun. but if something is ten times smaller then, for a given density, it weighs 1000 times less. that's because mass = density x volume, and volume = size^3. indeed as crut says, jupiter is 0.00095 suns, i.e. ~ 1/1000), and the sun dominates the gravitational forces planets experience to an almost overwhelming degree. (but not completely, see, e.g. http://en.wikipedia.org/wiki/Discovery_of_Neptune)

that animation is not to scale, no. the relative size of jupiter and the sun look about right, but all the other planets are way off (they should basically be invisible, e.g. the earth is ~1/10 the size of jupiter, i.e. 1/100 the size of the sun). also obviously the distances between the planets and the sun are wrong, e.g. the distance between the earth and the sun is 200+ times the size of the sun.

Like, if I were in space and I opened a bag of peas, would my gravitational pull force them to orbit me?

if you open them in such a way as to give them zero velocity relative to you (i.e. with a very steady hand), yes. but realistically you wouldn't have a steady enough hand, and you would impart enough energy for them to escape your orbit. assuming your arm is 1m long and you weigh 80kg, they'd need to be going at less than sqrt((2 * G * (80 kg)) / (1 m)) = 0.000231156472 mph (2 ten thousandth of a mile per hour) to be trapped in orbit around you.

Is there any rule of thumb for figuring out what's the biggest thing I could get to orbit around me in space?

― Fetchboy, Friday, March 1, 2013 7:21 PM (12 minutes ago) Bookmark Flag Post Permalink

you mean space, far enough away from any other objects that their gravometric pull doesn't overwhelm your own, right? I am thinking that even at a far distance, the sun is going to exert a greater pull than your own mass

― ☠ ☃ ☠ (mh), Friday, March 1, 2013 7:33 PM (59 seconds ago) Bookmark Flag Post Permalink

yeah the question is different depending on whether you're in the solar system or "deep space". in the solar system, you're basically asking, what's the biggest moon i could keep in orbit around planet fetchboy, without the sun pinching it and turning it into a planet. that would depend on how far you were from the sun, earth, etc.

in deep space, the only limit is the escape velocity: http://en.wikipedia.org/wiki/Escape_velocity. as long as your "moon" is moving slower than that away from you, it will orbit you.

there's a complication though: one body doesn't orbit another. they _both_ orbit their _shared_ centre of mass. in the case of the sun and the earth, that centre of mass is basically the centre of the sun, because the sun is so massive. it's a little bit further from the centre of the sun for the jupiter-sun system, and in fact the sun visibly wobbles in response to jupiter. observing exactly this effect in other stars is how most exoplanets get discovered (500+ of the 800+ we know about, according to http://exoplanet.eu/catalog/). the centre of mass of the earth-moon system is inside the earth, but only just.

that gif is blowing my mind

we're traveling in like a "solar up" direction?? where are we even going? this is madness.

the sun isn't moving exactly in the plane of the galaxy, but approximately so. and yeah apparently the plane of the solar system happens to be about 60° to the plane of the galaxy. who knew.

oh great so we're cockeyed too

iphone people: i recommend the app "exoplanets"

you can explore the MW, throw it around, pinch in out, etc.

and you can make neat graphs like size of planet against discovery year (notice we're getting good at finding smaller and smaller planets, i.e. closer and closer to earth mass)

we're traveling in like a "solar up" direction?? where are we even going? this is madness.

― goole, Friday, March 1, 2013 2:51 PM (6 minutes ago) Bookmark

http://i.imgur.com/CXIjIEr.jpg

Thought the Sun was moving at about the same velocity as nearby parts of the galaxy. There's nowhere to put the camera to capture this. The only way to get this effect given movement of nearby bodies would be to have the camera moving away from solar system at Ludicrous Speed, in which case the experience will be of the observer moving, not the solar system. No?

figuring out what's going on in the solar neighbourhood is very, very tricky and it's very difficult to visualize how they do it. but they do it by observing nearby stars.

on average they're all going round the sun at about the same speed in the same direction, 200-odd km/s. there's some scatter though. some are on perfectly circular orbits in the plane of the galaxy, some wobble up and down, some are on "radial" orbits, i.e. plunging toward the middle and out the other side, and only happy to be passing through the solar neighbourhood right now.

the upshot of that scatter in velocity/direction is that the stars that are close to us right now, will not be our nearest neighbours forever

http://upload.wikimedia.org/wikipedia/commons/thumb/e/e9/Near-stars-past-future-en.svg/749px-Near-stars-past-future-en.svg.png

Right, but those changes are glacial for any observer in a human time scale. There is literally nowhere to put a camera to visualize that gif. Even if the "camera" moved that fast away from the S.S. it wouldn't see the Sun translating so dramatically against the backdrop of near space, which is also moving at similar speeds in similar directions.

well that gif is just showing what voyager II is beaming back .... dunno what to tell ya man

afaict the camera is orbiting the centre of the MW faster than the sun, which is why the stars in the b/g are seen in parallax

apart from the scale issues, it looks basically plausible