Nebula spotted with more super-sized bodies than a gym on Jan 2nd

I agree as I had a similar reaction on reading it.

I think a couple sentences need to be updated something along the lines of:

The Tarantula Nebula, also known as 30 Doradus or 30 Dor, located about 160,000 light years away in the Large Megallanic Cloud, a satellite galaxy to our Milky Way , could contain a whopping 600 stars that are between 15 to 200 solar masses.

and

It’s uncertain how common rich galaxiesnebulae like 30 Dor are.

" all major star forming regions have that to a smaller or lesser degree" [DYM greater or lesser?]

But anyway, yes, these regions are fairly common and, essentially, inevitable.

If the Universe is not to be completely homogeneous at all scales then there must be variations in the distribution of stuff and this, in turn, means that there must be extremes - statistical outliers. It would actually be a bit strange if things like 30 Dor didn't exist with the apparent frequency that they do.

Statistical outliers always make for a good news story though.

Not to seem too cynical about this, statistical outliers are also good at provoking thought.

Re: LIGO/VIRGO

We can tell direction because firstly LIGO is two detectors separated by a reasonable distance and secondly VIRGO is way across the Atlantic in Italy. We have stereo vision in the gravity wavelength and stereo vision gives depth perception and direction detection as well. The wider apart your 'eyes' are the better things become, up to a point.

In the first ever detection only one LIGO was operating at the time and VIRGO was not up and running fully but now we have three eyes watching.

The real mind blowing things is that by bouncing the light a few times along the arms effectively increases the detection sensitivity and they can detect movement as fine as a fraction of the width of a proton.

Necessary to see these things. Early versions saw nothing, these are the upgraded versions.

There is a proposal to put one in SPAAAAACE and the ESA has flown a demonstration pair of satellites in sufficiently precise lockstep to show we have the technology. This would enable much longer arms than we can make down on our curved earth and removes the vast majority of terrestrial vibration sources such as earthquakes, trains, heavy trucks, volcanic eruptions, storms and the like. Which all have to be measured and filtered out on earth.

Who knows what we might see with instruments like this?

Re: LIGO/VIRGO

Given that it concerns black holes, how are they going to pinpoint the location of the event since, by definition, they didn't see that a collision was going to take place ?

Do you mean to imply that you can't see a black hole collision coming because you can't see those black holes themselves?

The presence of black holes can be inferred by effects on their local environment, stuff swirling inwards around them, as well as gravitational lensing. So they can be located, their trajectories determined and a possible collision predicted.

Re: LIGO/VIRGO

With 2, 3, or (ideally) 4 detectors, you can locate the source of the gravity wave, by using the same math that your cell phone or the GPS in your car uses to locate you.

For those few of us who remember their 3D analytic geometry:

The difference in timings from 2 detectors puts the target on a curve called a hyperbola. With 3 detectors you can calculate 2 hyperbolas, which have at most 4 intersections. But you have enough data to find a 3rd hyperbola which passes through 1 of the 4 intersections, and you are there! This is enough to know where your phone or car is on a known surface (the Earth), or the direction that a gravitational wave came from. Ordinary telescopes than look for an object out there, and use astronomy tricks to determine its distance.

With 4 detectors, you calculate curved surfaces called hyperboloids and similarly nail down intersections. Then you can calculate the distance to the gravity wave emitter without astronomy. Simple high-school math! (With an assist from a desktop computer, of course, we're IT guys....)

Re: Try as I might, I still can't conceptualise/visualise gravity waves

If you look a the ball depressing the elastic sheet model of spacetime then two other balls moving on the sheet cause vibrations which stretch and squeeze the sheet.

The detection is like detecting any sort of wave. The only difference is the medium.

As a Kiwi in exile I followed the recent Kaikoura earthquake which did things like raise the land up by between 2 and 4m. Large sections of seabed were raised up with sea life included. The NE of the South Island of NZ was moved NE, stretched by tens of metres.

That point is a plate boundary, the Pacific plate of heavy, dense seafloor is subducting between the lighter Australian plate.

We conceptually think rocks are hard and brittle and the land is not stretchy. But it is. Up to a point. In reaction to all the shaking the hillsides fell down in massive landslips. But the movement of the land was incredible.

Darwin took time off from the Beagle to cross the Andes from Chile. Where he landed there had just been a massive quake which similarly raised up a portion of seabed some metres and seeing this rock with sealife still clinging to it was in Darwin's mind as he sat on his burro ascending the Andes and seeing shells in the rocks he realised many uplifting quakes over geological time had raised the seafloor up to the high peaks.

The Kaikoura coast consists of maritime alps which rise directly from the sea. Not as high as the Andes but the same principle and snow capped and sharp.

Those in the area at the time commented about how noisy it was. The land groaned as it was stretched and thrust upwards and the hillsides fell downwards.

Re: Try as I might, I still can't conceptualise/visualise gravity waves

Sorry guys, I was the OP of this thread.

I understand what the effects can be (The Simpsons 3D episode was appropriately funny and enlightening), I just can't get to grips with HOW it works which is why in the OP I said I understand without understanding.

I understand the concept of time dilation no problem, but just can't get my head around space time, mental block, stupidity, call it what you will....I just can't get there.

Re: Try as I might, I still can't conceptualise/visualise gravity waves

I know, right? It all seems more like philosophy than physics.

Scientists seem to like to refer to space with words we usually use to describe liquid. Matter is furiously spinning, tiny little whirlpools of -- something. Something that is, and also is not nothing. Except it's not those 2 1/2 dimensional whirlpools you get in water. They're 3 1/2 dimensional whirlpools. Something you can't actually imagine, but you can do math with.

Get enough of those whirlpools, and you get a big whirlpool. And those big whirlpools stuck stuff in. Except there's no stuff, just the liquid. Which isn't a liquid. Since all stuff is just whirlpools, the stuff it sucks in is other whirlpools. Crash a couple really, really, big whirlpools together, and you get a shock wave that travels out through the nothingness that isn't nothingness, nor is it a liquid.

It's just one holy psychedelic fever dream.

Re: Were you expecting us?

It's the spacial distortions by all the black holes that make the Kessel run so interesting. Really good pilots can thread the needle and do it in 14 parsecs. There is a legend, though about one guy...

Re: alan.green@balfourbeatty.com

But you can see them. Or at least you can see where they are. All the dust and stars that are circling the a black hole, getting closer and closer until too late, emit very high frequency high-energy electromagnetic radiation, which can be "seen" and measured with gamma-ray detectors and radio telescopes and such.