

Einstein Was Right: NASA Announces Results of Epic Space-Time Experiment - tableslice
http://science.nasa.gov/science-news/science-at-nasa/2011/04may_epic/

======
tzs
It's not all that epic. These effects had already been measured by other
experiments and were found to agree with general relativity to much more
accuracy than the GP-B measurements. What GP-B brought to the table was a
direct measurement, as opposed to indirect measurements used by the other
experiments.

However, because the way they measured it pushed the limits of engineering, if
GP-B had NOT agreed with GR there is good chance the results would have been
dismissed as most likely due to equipment flaws.

While it is in general a good idea to confirm measurements, especially using
different techniques, in a case like this where the confirmation will be much
less precise than the other experiments and will likely be rejected if it
fails to confirm, you have to wonder why this was funded over other projects.

The answer to that turns out to be simple: politics. When space scientists
ranked all the proposed missions under consideration, GP-B came in dead last.
However, its proponents went to Congress, and got Congress to override the
normal process for prioritizing missions, forcing NASA to move it to the
front, ahead of more scientifically worthy missions.

There are a lot of very worthwhile scientific missions that we can't fly due
to budget limitations. It's a shame to see $750 million of the limited budget
go to a mission so far down on the importance list.

~~~
phlux
It is epic because he predicted this before any of the technical wizardry was
even in existence.

So, sure - the _proof_ may not be epic -- but the _prediction_ certainly is,
especially even moreso that he is correct (again)

~~~
jonnathanson
Einstein was so brilliant that his very name became a popular cliche. And yet,
the more modern science digs into his theories, the more we see that, if
anything, his brilliance is still _underrated_.

------
ColinWright
Same story, many comments:

<http://news.ycombinator.com/item?id=2516510>

------
scottdw2
Did the experiment use a control? That is, did they put other gyros in places
where space time should not have been twisted and observe no deviation?

If not, how do they know that the deviation was in fact caused by twisting
space time?

~~~
guygurari
While I understand your thinking, what you're suggesting is not the correct
methodology. General Relativity makes a specific, quantitative prediction for
an effect. The prediction is not trivial, in the sense that the most
reasonable alternative theory -- Newtonian dynamics -- predicts there should
be no effect at all. (This is the null hypothesis if you will.)

The GP-B experiment measured this effect and found agreement with the GR
prediction. This does not prove that GR is correct; rather, it is a piece of
evidence that implies GR is more likely to be a correct description of gravity
than what we previously believed [1]. Because the prediction was quantitative,
it is unlikely that the result is caused by something else, which makes the
evidence in favor of GR that much stronger.

Now, control groups are often used in life sciences fields. For example when
you test a drug, you have a control group that takes placebo. It's not my
field but as far as I understand this is done for two reasons. First, there is
no quantitative prediction regarding how effective the drug should be, because
drugs are not understood so precisely. So the prediction you're testing is
much weaker; it's just a boolean. Second, there is a known effect -- the
placebo effect -- that can affect results. In other words your null hypothesis
is that there may be some effect. These things mean that, without a control
group, the evidence in favor of a drug's effectiveness is not very strong.

[1] That is not to say that we believed GR was wrong, but we can never be 100%
sure, and every piece of positive evidence strengthens the case.

~~~
waqf
Right, the efficacy of GR was being tested, and the control was Newtonian
dynamics. GR was found to successfully predict the results observed. The
control is to attempt to predict the results with Newtonian dynamics and check
that that prediction is less accurate.

If you accidentally did an experiment where GR and Newton predict the same
thing, the control would kick in and tell you that you hadn't proved anything.

------
wallfly
It would be interesting to find out if using Hans Montanus's non-canonical
formulation of GR (which involves a Euclidean metric and perfectly flat space-
time) would yield the same numerical predictions, just with different "book
keeping".

That would put a different spin on the notion of Einstein "being right" as I
think a lot of folks subconsciously equate GR with the "strangeness" of the
Minkowski metric and non-Euclidean space-time manifold.

------
catechu
From article: "The mass of Earth dimples this fabric, much like a heavy person
sitting in the middle of a trampoline."

I will never imagine general relativity the same way again.

------
known
My understanding is we should benchmark everything with
<http://en.wikipedia.org/wiki/Speed_of_light>

------
Vivtek
I initially read this "Einstein was right, announces results of epic space-
time experiment", which _would_ have been epic and a much more interesting
story.

