"...clearance for a new hyperspatial bypass. Regrettably, your planet is scheduled for demolition."

Not really a re-run as such, but whatever we're seeing from Earth surely has already been and gone as such by the time the light arrives here?

I wonder if there is a way of truly knowing what the real time situation is at the M101 galaxy.

no way of knowing, I suspect, without access to a stargate.

Its a serious question. Really.

And how do you determine the size of the black hole?

Where upon we would be able to view the past ... all in all, a dodgy premise

http://www.universetoday.com/2006/04/18/when-black-holes-merge/

To measure the size of a black hole, you only need to know its mass, this determines the so-called Swartzschild radius, i.e. the distance from the centre from which light cannot escape. Measuring mass is done by observing the effect on the motions of nearby objects (or if it is part of a double system measuring the orbital parameters of the visible companion).

I think the point is that every time you look up at the star's you're viewing the past (given the time the light took to reach Earth), therefore none of the stuff we're seeing is actually there or in that state anymore.

A Stargate on the other hand would allow you to go in seconds to the other location and see what the real state of things is there. :-)

Technically, everything you look at is in the past, as it takes time for reflected light to reach your eyes, not to mention the time it takes for your brain to process the information.

To be truly philosophical, everything is in the past anyway, since all thoughts you have had are in the past, and as soon as you identify a moment as the present, it is in the past; and all evidence of life, objects, the universe itself, is based on information collected in the past.

In other words: Nothing exists.

I would measure it.

@ Michael H.F. Wilkinson - you are not measuring it - you are inferring its size. In that regard your inference is weaker than the deduction of the size of dinosaurs from thigh bones. It's only about as strong as deducing the size of a yeti from its footprint. The facts that (a) there is much more tax-payers money to be had for inferring about "black holes" than about yetis, (b) there are far more boffins cashing in on it rather than in yetis does not make the inference any stronger - all that mean is the hive mind can make a bigger noise.

> I would measure it.

Hush!

Stop being boringly obvious and revise your General Relativity which will enlarge your event horizon (so to speak). Also reflect on the fact that the General Relativity is a very strong base principle, always proven right experimentally, and yeti size deduction is a set of ad-hoc rules, never proven right experimentally.

In the past, yes.. 27 million ago according to the boffins. But a mere blink of an eye in galactic terms, I'm guessing.

@ Luther Blissett

"I would measure it."

How?

Since black holes are not directly observable all you can do is to infer it's size. And "size" might not even be very well defined for

something like a black hole, so the Swartzschild Radius is probably as good as you're going to get. If we're talking about black holes

we're along way from any sort of common sense.

@ Ian Ferguson

"In other words: Nothing exists."

Then why bother posting? Or did you? I guess you didn't...

I challenge all yeti measurers to fly to a black hole to measure its diameter with a tape measure (on the Swartzshild surface of course). ;-)

Incidentally, the fastest flickering (in X ray usually) gives an upper bound to the size of a black hole too. These measurements do not conflict with other predictions made by general relativity

Put some white paper behind it and then you can see it, obvious really.

... yes this is all getting a wee bit silly, and no this is not meant as a serious response (just in case)

...Just another blatent example of the enviro-nazis stirring up panic to fund their own pet projects. Just because you "see" star formation doesn't mean it's actually "happening".

These so-called "boffins" with their "scientific method" and "observations" are just the lapdogs of industry lobyists trying to sell space exploration.

Reality is, whe're better off here at the bottom of our hole. Pull a comfy blanket of CO2 over your head and let God worry about the greater cosmos.

I am your host for tonight, Max Quordlepleen

"Also reflect on the fact that the General Relativity is a very strong base principle, always proven right experimentally, and yeti size deduction is a set of ad-hoc rules, never proven right experimentally."

Actually, both methods are epistemologically equal, from a logical positivist perspective. Neither method can ever be "proven right experimentally". They continute to stand as valid hypotheses because they have not yet been proven _wrong_ experimentally.

In terms of empirical data, though, a black hole just about shades it (boom boom) when compared to a Yeti. I believe we have "observed" black holes more often that Yetis.