

"Death Dance" Stars Found - May Help Prove Einstein Right - coderdude
http://news.nationalgeographic.com/news/2011/07/110719-white-dwarfs-supernovae-gravity-space-science/?source=link_fb20110720deathdancestars

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andrewcooke
oh for goodness sake. journalists - do you have no better ideas than "prove
einstein right"?

einstein was right. his work was an improvement on what went before. we _know_
this. it has been confirmed by many, many experiments and observations. and
reported countless times with the same tedious headline.

please, use something a little more original.

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Roboprog
Well, of course we _expect_ the gravity waves to be there, given the other
effects of relativity that have been confirmed so far.

However, scientists still observe, verify, measure. As one other poster
mentioned, the equipment to detect gravity waves from afar has not yet been
able to do the job (due to opportunity or sensitivity, don't know).

If for some reason they do not find the waves (and the instruments are shown
to be good), then there will be some more deep thinking to do: were we really
looking at objects different than what we thought? Is there some theory more
twisted than relativity that needs to be made to explain the previous results
as a special case and also explaining the new results???

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andrewcooke
sure. i have already said the same below.

i am not criticising the physicists, or the person who originally posted the
article, or denying how interesting it would be if waves were not found, or
disparaging the technical difficulties involved.

i am just tired of the same hackneyed phrase being used in every article
related to general relativity. google has over 12 _million_ hits for the
phrase "einstein was right". the national geographic is a quality publication.
it should know better.

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CanSpice
I'm trying to figure out how these are different from the binary pulsar PSR
B1913+16 (other than they're white dwarfs and the binary pulsar is two neutron
stars). PSR B1913+16 is two neutron stars orbiting each other in a tight
spiral, and their orbital decay corresponds with what Einstein's general
relativity predicts. In fact, the discoverers of PSR B1913+16 (Hulse and
Taylor) received the Nobel Prize in Physics in 1993 for showing that this was
the case.

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jevinskie
I'm unclear about how they are spiraling towards each other at 370 mi/s, just
1/3 the Earth-Moon distance apart, yet will take 900,000 years to merge. Can
anyone clarify that?

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tmhedberg
They aren't moving directly toward each other at that rate; they are orbiting
each other at that rate, and very gradually moving closer.

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flatline
Does anyone know how they would go about observing the gravitational waves?
Through lensing effects? Or are they just depending on the orbital decay to
demonstrate something?

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jessriedel
I don't have any expertise in astrophysics (just physics), but I am pretty
sure that white dwarfs aren't nearly strong enough to produce observable
lensing. You need black holes or whole galaxies for that. Further, these stars
are separated by less than the earth-moon distance, so they aren't
individually resolvable. The fact that it is a binary system has been inferred
from periodicities in it's brightness and spectrum. ("Astronomers measured the
stars' relative motions by looking at the light signatures, or spectra, coming
from the stars as they eclipse each other.")

I think your guess is right that all the data about the gravitational waves
will be taken from the orbital decay. This is actually a decent amount of data
since the rate of decay isn't constant, and because the eclipse maneuver isn't
a smooth process.

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mrspeaker
Android devs have known about this for ages. That's why there's already a
field for it in the sensor manager SDK docs...
[http://developer.android.com/reference/android/hardware/Sens...](http://developer.android.com/reference/android/hardware/SensorManager.html#GRAVITY_DEATH_STAR_I)

