Hey Brett! Things going in circles -- in spaaaaaaace!

[Tim Wescott]

It's got things going in circles, so it's relevant to control line.  And it's got things in space, and really precise measurements, and wacky control systems -- so it's relevant to Brett.

Enjoy (or not).  I suspect that Brett's already on top of this:

[Brian Hampton]

I'm always amazed at the accuracy these experiments need and the fact that the scientists can actually achieve it. Don't know if anyone picked it up in that video but it was mentioned that they can determine the distance between those two blocks to less than the size of an atom. Similar accuracy was used in the LIGO experiment but over distances of several kilometres and they were dead lucky in that very shortly after switching it on they got a result from two massive black holes merging. The video below shows the final second or so of that merger. From memory, both black holes were a very similar mass of around 60 times the sun's mass. As they get closer to each other they begin to orbit around their common centre and this sets up a gravitational wave but at first it's so weak that it'd be undetectable plus its wavelength is the same as their orbital period. But over time they lose energy and get closer and closer to each other which means they start to orbit faster and faster and the gravitational wave gets more and more intense.

Now, to get back to that video below. Remember that there are two objects each massing about 60 times more than the sun orbiting around each other. Look at the timescale at the bottom of the graph. That begins a half second before the final merger. The graph has been converted to a sound wave so it's been called the chirp. In the final moment those two massive bodies are orbiting at about 1000 times a second!

[Brett Buck]

It's got things going in circles, so it's relevant to control line.  And it's got things in space, and really precise measurements, and wacky control systems -- so it's relevant to Brett.

Enjoy (or not).  I suspect that Brett's already on top of this:

   Sorry to disappoint, but I hadn't even heard of this. It sounds like a double-sensor version of Gravity Probe B, at first blush. Gravity Probe B navigated a spacecraft around a spinning gyro rotor/ball as it fell freely. I can see how you can navigate it around the cubes, I suppose, as long as you have an actuator that moves the enclosures further apart or closer together. It has to sense the motion of the cube WRT the housing somehow, so I guess they figured out that the force applied by the photons needed for the sensing put little enough force on the cube to not obscure the effect they are looking for. The people involved are usually pretty good at that sort of thing.

     Very interesting project.

   Brett

[Tim Wescott]

   Sorry to disappoint, but I hadn't even heard of this. It sounds like a double-sensor version of Gravity Probe B, at first blush. Gravity Probe B navigated a spacecraft around a spinning gyro rotor/ball as it fell freely. I can see how you can navigate it around the cubes, I suppose, as long as you have an actuator that moves the enclosures further apart or closer together. It has to sense the motion of the cube WRT the housing somehow, so I guess they figured out that the force applied by the photons needed for the sensing put little enough force on the cube to not obscure the effect they are looking for. The people involved are usually pretty good at that sort of thing.

     Very interesting project.

   Brett

You'd also need some way to get the cubes travelling in formation well enough that your enclosures don't run out of range of travel.

Nifty stuff.  Makes me regret having an ordinary job.

[Brett Buck]

You'd also need some way to get the cubes travelling in formation well enough that your enclosures don't run out of range of travel.

   Presumably, you run the experiment for as long as you can accommodate the relative motion, then cage the cubes, recenter them, then release them again and start up the next experiment. Same with launch, you have to hold them solidly somehow until you in the final orbit and stable enough to start, just restow them when they get too far apart.


    Brett

[Randy Cuberly]

  Presumably, you run the experiment for as long as you can accommodate the relative motion, then cage the cubes, recenter them, then release them again and start up the next experiment. Same with launch, you have to hold them solidly somehow until you in the final orbit and stable enough to start, just restow them when they get too far apart.


    Brett

As I understand it the forces are simply too small to reliably measure without tremendous masses that react together.  Hence the reaction of two black holes that were simply a stroke of luck at the right time!  I was aware of some of the efforts on the instrumentation for this through my association with NOAO and NRAO at the U of AZ, but was not directly involved.

Incredibly interesting stuff.  It's only taken about 100 years to catch reality up with the mind of Dr. Einstein.

Randy Cuberly

[Tim Wescott]

Incredibly interesting stuff.  It's only taken about 100 years to catch reality up with the mind of Dr. Einstein.

There were actually experimental results in General Relativity within ten or twenty years of it's formulation -- the perihelion of Mercury precesses ever so slightly, in a way that's not at all predicted by Newtonion mechanics but which is dead on to the predictions of Relativity.

One of the sources of excitement I've been seeing on this that's not in this particular video is that this is the first time that astronomers are getting real information about stellar events that are carried by something other than photons.  Everything else we get is electromagnetic radiation of some sort -- so gravity-wave astronomy is like opening a whole new window.

[Randy Cuberly]

There were actually experimental results in General Relativity within ten or twenty years of it's formulation -- the perihelion of Mercury precesses ever so slightly, in a way that's not at all predicted by Newtonion mechanics but which is dead on to the predictions of Relativity.

One of the sources of excitement I've been seeing on this that's not in this particular video is that this is the first time that astronomers are getting real information about stellar events that are carried by something other than photons.  Everything else we get is electromagnetic radiation of some sort -- so gravity-wave astronomy is like opening a whole new window.

Yeah...the biggest problem is finding the "window".  This time they admittedly got very lucky.  Events like that don't happen every day and
and as stated, last a second or so!  Talk about lucky data collection. 

[Tim Wescott]

Yeah...the biggest problem is finding the "window".  This time they admittedly got very lucky.  Events like that don't happen every day and
and as stated, last a second or so!  Talk about lucky data collection. 

Apparently they've detected more events, but that was hugely lucky.