

30-year-old black hole discovered by  - bsk
http://www.nasa.gov/home/hqnews/2010/nov/HQ_10-299_CHANDRA.html

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ojbyrne
So if this is 50 million light years away, shouldn't it be a 50,000,030 year
old black hole?

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Cushman
Depends on your frame of reference.

No, really: <http://en.wikipedia.org/wiki/Relativity_of_simultaneity>

There's not really such a thing as "right now, over there". To use the obvious
example, from the perspective of the light, no time has passed since it was
emitted at the object and our observing it.

~~~
pyre
I think the point is that if we were able to instantaneously transport
ourselves there we would be observing a 50 million + 30 year old black hole.
Nobody talks about things from the the perspective of a photon (in casual
conversation, at least).

~~~
baddox
That's false, or rather, undefined. To "instantaneously transport ourselves"
implies that there is an _absolute_ time frame shared by us and the black
hole, i.e. if it's 3:00 PM our time when we transport ourselves, we'll appear
at 3:00 PM "black hole time."

There simply is no such concept in relativity. For two events A and B
separated in space, some observers will see them happening simultaneously,
some will see A occur before B, and still other will see B occur before A.

~~~
JoeAltmaier
Yeah, we hear that a lot. But we also know to the millisecond "how long" it
took the light to get here etc. Yes, they are different frames of reference.
But if we crawled over there we know exactly how much time had passed there,
and how old the black hole would be when we got there.

~~~
jerf
You said "instantaneously". That usually would imply traveling outside of your
lightcone. That really is undefined; an "instantaneous" transport from here
can end up anywhere outside of your lightcone, which are all equally
well(/poorly) defined in relativity. You can't distinguish those points in
either time or space without creating a preferred reference frame.

This is the same reason FTL drives are also, fundamentally, time machines.
It's really a very profound thing; there's no "yeah, but really we know
there's an absolute time frame underneath it all"... there really, _really_
isn't an absolute time frame, and you really, _really_ can't say how old the
black hole would be if you "instantaneously" transported there; it is just as
valid to instantaneously appear when it is 31 years old as it would be to
appear when it is 100,000,029 years old (taking of course the estimated age as
its true age). Or, IMHO, just as invalid because FTL and instantaneous truly
don't exist.

Yes, if you change your claim to be sublight and non-instantaneous we can
compute how old it would be, but that's a profound goal post shift.

The Minkowski metric is a mindbender, the moreso once you realize that it is
not some weird mathematical abstraction with no connection to reality, it _is_
reality, or at least a much better approximation than the one we instinctively
use. The "weird mathematical abstraction with no connection to reality" is the
implicitly Euclidean/Galilean metric that exists in our heads. (Which can
actually be demonstrated to contain fundamental contradictions if you poke
them hard enough.)

~~~
JoeAltmaier
Yet we know

The age of the universe

The age of all the stars we see in the sky

How long ago that supernova occurred

On and on.

I get it. There is a disconnect between my timeframe and that of a different
acceleration frame. But they are related in a precise calculatable and
empirically-confirmed way that lets me set a clock in one and know exactly
what the clock in the other will read.

~~~
baddox
Knowing the age of something at a given time in its own reference point isn't
contradictory, thus we can know the age of the Earth, etc. It's __is
__contradictory to say that __now, in our reference frame __, the [supernova,
black hole, star, etc.] is _x_ years old. The only thing that makes sense is
to judge how old the object appears to us, judging from the information
(light) that's reaching us now from the given object.

~~~
JoeAltmaier
Then does it make sense to say "that light took 50,000,000 years to get here"?
Or is the black hole 'truly' 30 years old?

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siegler
They wait until the end to say that it could be just a neutron star.

 _Although the evidence points to a newly formed black hole in SN 1979C,
another intriguing possibility is that a young, rapidly spinning neutron star
with a powerful wind of high energy particles could be responsible for the
X-ray emission_

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psadauskas
Nice human-readable summary here, too:
[http://blogs.discovermagazine.com/badastronomy/2010/11/15/as...](http://blogs.discovermagazine.com/badastronomy/2010/11/15/astronomers-
may-have-found-youngest-black-hole)

~~~
hartror
I think every space article I have read on HN has had a better write up by
Phil linked in the comments.

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rbanffy
50 million light-years away? They called that our "neighborhood" a couple days
ago...

I think a lesson on expectations management is due.

~~~
frisco
I believe "neighborhood" has a formal definition here.

~~~
NHQ
Blame realtors.

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toppy
Is it possible to even notice 30 years in 50M-year frame?

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ceejayoz
It is when time zero begins with an explosion that outshines the whole galaxy.

