Comments on: Physics images

Physics images

Kirth Gerson — Mon, 21 May 2007 04:02:48 -0800

Sharpest manmade object This site _via has a huge collection of wonderful images, some CG, some actual. Black hole merger. Solid state microrefrigerator. Helium nanodroplets used to chill Nitrogen Oxide. Playing a nanoguitar.

By: hoverboards don't work on water

hoverboards don't work on water — Mon, 21 May 2007 05:11:30 -0800

That sharpest manmade object image is pretty cool. What are the "craters" on its surface?

By: Citizen Premier

Citizen Premier — Mon, 21 May 2007 05:14:44 -0800

By: Citizen Premier

Citizen Premier — Mon, 21 May 2007 05:16:12 -0800

...answer that bearing in mind that I'm not actually qualified to use the term "black hole."

By: AmberV

AmberV — Mon, 21 May 2007 05:24:26 -0800

The “craters” are explained in the caption. The little round pebbles you see on the surface are individual atoms, and the crater effect are the visual results of atomic movement that happened during the exposure.

By: Faint of Butt

Faint of Butt — Mon, 21 May 2007 05:31:07 -0800

So when are they going to adapt the nanoguitar into a nanoviolin that I can play for people who want my sympathy?

By: delmoi

delmoi — Mon, 21 May 2007 05:44:28 -0800

You know, I never even wondered what would happen when black holes enter eachother's event horizons--shouldn't it slow down the gravity waves of one or both of the black holes, making them less powerful? Totally wild-ass unqualified guess: Light slows down because photons have energy, and thus mass, whereas gravitons (if they even exist) may not.

By: kcds

kcds — Mon, 21 May 2007 05:48:22 -0800

Back off! I've got a shrink gun!

By: delmoi

delmoi — Mon, 21 May 2007 05:49:07 -0800

Except wikipedia says the photon is also massless, like the graviton. So my other theory is that black holes are defined in relativity, where gravity is defined by (again, I don't really know what I'm talking about) curvature of space, whereas the graviton, and gravity waves are part of quantum physics, and quantum physics and relativity don't match up yet.

By: hoverboards don't work on water

hoverboards don't work on water — Mon, 21 May 2007 05:58:56 -0800

The "craters" are explained in the caption. The little round pebbles you see on the surface are individual atoms, and the crater effect are the visual results of atomic movement that happened during the exposure. Are you sure that's what the caption is saying? I thought the "lighter colored elongated features" were the red streaks. The crater rims are pink and gray, and not elongated.

By: ~

Mon, 21 May 2007 06:00:05 -0800

delmoi that's probably not right since (not-physicist) photons are influenced by gravity and (not-philosopher) the fact of a force acting on a particle is not influenced by our lack of a gut (not-gastroenterologist).

By: Thorzdad

Thorzdad — Mon, 21 May 2007 06:17:21 -0800

hoverboards...I think the craters you see are atoms settling around irregularities or molecular textures on the surface of the needle. At least that's how I'm explaining it to myself. IANAP, of course, and I eagerly await the real answer.

By: edd

edd — Mon, 21 May 2007 06:20:37 -0800

You know, I never even wondered what would happen when black holes enter eachother's event horizons--shouldn't it slow down the gravity waves of one or both of the black holes, making them less powerful? I'm not entirely sure what you're getting at, but I think it's probably a bad idea to think of one entering the horizon of another. The horizons would meet and merge into one. One can't cross the event horizon of the other, because when they touch you just end up with one all-enveloping horizon.

By: Kirth Gerson

Kirth Gerson — Mon, 21 May 2007 06:30:17 -0800

So when are they going to adapt the nanoguitar into a nanoviolin that I can play for people who want my sympathy? posted by Faint of Butt FoB, your audience would need really acute hearing: "... the guitar, shown above, twangs at a frequency of 40 megahertz, some 17 octaves (or a factor of 130,000) higher than a normal guitar."

By: edd

edd — Mon, 21 May 2007 06:32:06 -0800

Oh and this might help with the black hole questions, although it's not about mergers

By: milestogo

milestogo — Mon, 21 May 2007 07:01:58 -0800

Very cool. I wonder how physicists define "sharp." Does anyone know?

By: adipocere

adipocere — Mon, 21 May 2007 07:06:49 -0800

Ah, gravity waves are part of general relativity, not QM. We'd like them to be, though. Photons are massless. Which is to say, they are rest massless, since, in their natural state, they are never at rest. That slowing down and trapping light business is another matter. E=mc^2 (which is a limited case of a slightly more complicated equation) only states equivalence of amount, not actual identity. Apples = Dollars * 2 is just an exchange rate, it doesn't mean that dollars are tasty. My apologies to those who do eat dollar bills. The event horizons should reach towards each other and merge, rather than simply look like two spheres touching. They would throw off quite a mess of gravity waves as they spin down together. Gravity waves always travel at the same speed so far as I would know, or black holes wouldn't have any gravity at all. Gravity waves travel at the speed of light, although there are some who think it is faster, perhaps infinitely so. I'm not buying that one, though.

By: chrismear

chrismear — Mon, 21 May 2007 07:18:46 -0800

I wonder how physicists define "sharp." Does anyone know? The width of the tip. The wider it is, the less sharp it is.

By: pracowity

pracowity — Mon, 21 May 2007 07:20:11 -0800

I wonder how physicists define "sharp." Very pointy. Or maybe this (pdf): "the radius of curvature of the near apex region is very small, less than 1 nm"

By: IronLizard

IronLizard — Mon, 21 May 2007 07:48:48 -0800

I wonder how physicists define "sharp." Does anyone know? Sharp is an acute angle.

By: three blind mice

three blind mice — Mon, 21 May 2007 08:00:10 -0800

Sharpest manmade object... I was expecting a photo of Ann Coulter's tongue.

By: lostburner

lostburner — Mon, 21 May 2007 08:17:42 -0800

Sharpest manmade object... I was expecting a photo of Ann Coulter's tongue. You fool. Such sharpness cannot have been begotten by man, and surely has come directly from places of deeper darkness.

By: lester the unlikely

lester the unlikely — Mon, 21 May 2007 09:05:51 -0800

I got to sit in on an electron microscope experiment a couple months ago and it was a little disappointing to learn that those cool atomic-scale images are often touched up waaaay more than you'd think. That one looked like it had been painted...

By: Ethereal Bligh

Ethereal Bligh — Mon, 21 May 2007 09:17:37 -0800

Thank God adipocere is here or I would have had to snipe at someone. Please don't answer physics questions if you don't know that photons have zero rest mass or even if you think that gravitational waves are the same sort of thing as light waves¹. You're probably a smart guy/gal and a mensch otherwise, but hey. It's annoying. "Gravity waves always travel at the same speed so far as I would know, or black holes wouldn't have any gravity at all. Gravity waves travel at the speed of light, although there are some who think it is faster, perhaps infinitely so. I'm not buying that one, though." The speed-of-gravitational-waves was discussed here on MeFi when that experiment was conducted a few of years ago. As a non-physicist, trying to get to the bottom of that (reading lots of posts by GR to sci.physics.relativity on the subject) gave me a headache. Anyway, does anyone actually think that gravitational waves travel instantaneously? The Newtonian model of gravity requires that gravity propagate instantly; but gravitational waves are the ripples in space/time that occur when a (large) mass is accelerated. Those GR has propagating at the speed of light. A non-accelerating mass creates no waves and the effect of its gravitational field corresponds to its actual position. At any rate, that whole experiment and the surrounding debate was/is intensely interesting to me and I simply don't have the education to understand it. I hate it when that happens. "Ah, gravity waves are part of general relativity, not QM. We'd like them to be, though." Frankly, I'm inclined toward the GR view of gravity and not the QM suspicion of the existence of a graviton. Not that I'm the least qualified to say such a thing. But GR is so beautiful, it seems right. 1. See WikiPedia's article on gravitational waves for an introduction. I am not saying there aren't some similarities.

By: RoseyD

RoseyD — Mon, 21 May 2007 13:20:40 -0800

Thank God adipocere is here or I . . . Don't thank God unless you understand that this gathering is in no way influenced by absolute intelligence. It's annoying. That's only meant as plain funny

By: adipocere

adipocere — Mon, 21 May 2007 13:23:53 -0800

Ethereal Blingh, there are definitely folks who believe in an FTL transmission of gravity waves. And not just tinfoil-capped, gravity-lifter-building, Joseph-Neumann-worshiping whackjobs who breathlessly say, "Anything is possible!" Real people with PhDs in the appropriate fields believe it. In fact, the very first search result you get for "speed of gravity" in Google is van Flandern's site. He's long been a proponent of the "fast gravity" crowd. He's even been published in Physics Letters. He has the number set at 2x10^10 of c. Others have it set at infinity. I'm still not buying it, though. I always liked GR (even grinding through the tensors in my class for it), but something will eventually have to be done for it to play nicely with everyone else. I have held aside a space in my heart for the thought that perhaps gravity will be the "odd man out," and will simply never be unified with the other three.

By: Ethereal Bligh

Ethereal Bligh — Mon, 21 May 2007 13:41:03 -0800

"In fact, the very first search result you get for "speed of gravity" in Google is van Flandern's site. He's long been a proponent of the 'fast gravity' crowd. He's even been published in Physics Letters. He has the number set at 2x10^10 of c. Others have it set at infinity." Like I said (didn't I?—I edited my comment numerous times), I had mucho trouble with this discussion when I first encountered it and researched it. But I seem to recall that van Flandern, though with all the required credentials, is nevertheless considered to be at least "fringe". So did Fomalont's experiment just set the lower boundary to be very near c, or did it cast doubt on the fast gravity theory?

By: adipocere

adipocere — Mon, 21 May 2007 14:08:31 -0800

Last I heard from the Fomalont thing (was that four years ago already?) was that Cliff Will disagreed with his interpretation of the results, in the sense that "I don't think you measured what you think you measured." I haven't seen him in a while, though, so I haven't had a chance to ask him how that particular debate turned out. Oh, you're right that van Flandern's fringe. However, he's not quite so fringe that he's beyond the pale and into the land of the gibbering madmen. I'm just skeptical enough of everything that I won't quite close my mind on the matter for some time. I'm about 99.99% certain that gravity propagation is set firmly at c, and would be heartily surprised to find out that it wasn't, but not quite to the point that my head would explode. I'd say the vast majority of physicists agree with the c limit. Speaking of Clifford Will, check out Was Einstein Right? (Answer: yeah, pretty much so far). What's fascinating is the discussion of some of the alternate theories of gravity that would reduce to GR, etc. These minor contenders were quite plausible for a while, becoming more and more unlikely with each experiment. And that's what I think of van Flandern - I'm not quite sure where you draw the line between "unpopular fringe theory" and "kook" (and I am no defender of the kooks), but he does provide that bit of nagging doubt that is useful and can often serve as a kick in the pants. I suppose we more or less agree ... I just feel obligated to leave a little room for me to be surprised by physics, and to state it, because I never quite got to the PhD level, and the universe likes to throw even doctorates a few curve balls every now and again.

By: Many bubbles

Many bubbles — Tue, 22 May 2007 00:49:00 -0800

*geekgasm*

By: Smedleyman

Smedleyman — Tue, 22 May 2007 07:57:43 -0800

nifty stuff