
More evidence that Voyager has exited the solar system - spullara
http://blog.chron.com/sciguy/2012/10/more-evidence-that-voyager-has-exited-the-solar-system/
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tjoff
All these articles are a bit meaningless to someone, such as me, that don't
even know what the definition of the solar system is (and no article seems to
care about it).

To me, the solar system is just a heap of planets orbiting the sun. With that
definition once you pass the orbit of the last planet your have exited the
solar system (although since the orbits aren't circular and they all are in
the ~same plane there sure is still some room for debate about the exact
border of the solar system) - and consequently when pluto was excluded the
size of the solar system shrank.

I don't imagine that my simple view of the matter is in any way accurate, but
considering that noone seems to know where och what is supposed to happen when
you leave the solar system, what are we then waiting for?

That something odd is happening and then, aha! That must be it! This is from
now on the definition of the end of the solar system?

Sure, there might be a border where cosmic rays from outside of the solar
system greatly increase etc. but does that have to coincide with the
definition of the solar system?

~~~
ejdyksen
There is no clear definition for the edge of the solar system[1]. The Voyager
spacecraft are helping to define it.

The heliopause is a pretty reasonable way to define the edge of the solar
system. A stated goal of the Voyager mission is to search for the heliopause
boundary[2]:

 _Both Voyagers are headed towards the outer boundary of the solar system in
search of the heliopause, the region where the Sun's influence wanes and the
beginning of interstellar space can be sensed. The heliopause has never been
reached by any spacecraft; the Voyagers may be the first to pass through this
region, which is thought to exist somewhere from 8 to 14 billion miles from
the Sun. This is where the million-mile-per-hour solar winds slows to about
250,000 miles per hour—the first indication that the wind is nearing the
heliopause. The Voyagers should cross the heliopause 10 to 20 years after
reaching the termination shock._

That having been said, this is a poor title. The news is not that the
spacecraft has simply crossed a boundary. The news is that the boundary, until
now unknown, was discovered (potentially).

The difference is "Ship successfully crosses Atlantic Ocean" vs "Columbus
discovers New World". Perhaps a better title would be "More evidence that
Voyager 1 has found the heliopause, considered to be the edge of the solar
system".

\----

[1] <http://en.wikipedia.org/wiki/Solar_System#Farthest_regions>

[2] <http://voyager.jpl.nasa.gov/mission/interstellar.html>

~~~
cema

      There is no clear definition for the edge of the solar system[1]. 
      The Voyager spacecraft are helping to define it.
    

I think this is a very important observation. Thanks!

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vecter
Could anyone explain to me why there's such a dramatic change in the incidence
of extra-solar high energy cosmic rays or the incidence of solar particles?
Without reading this article, I would have guessed that those graphs should've
tailed off "smoothly" as distance from the sun increases, but what we're
seeing instead is more of a "phase change". What about the underlying physics
at a certain distance causes this very discontinuos behavior, and why this
distance specifically? I imagine this cutoff distance must be a function of
properties of our sun like luminosity, magnetic field strength, etc.

~~~
Detrus
Well the data looks close enough to these theories
<http://en.wikipedia.org/wiki/Heliosphere>

~~~
manojlds
It is curious that the wiki mentions Voyager I data for some claims and we use
those to verify Voyager I data?

~~~
snprbob86
1) When you have a hypothesis, you conduct an experiment.

2) When your experiment yields results that match your hypothesis, you
consider that evidence.

3) When you have sufficient evidence, you upgrade your hypothesis to a
theorem.

According to the Wikipedia article, we've got at least two probes that are
producing results in line with our hypotheses. The bar for wikipedia is
"sourced", not proven theorem with scientific rigor. In this case, we're in
some nebulous area between 2 and 3. I think that meets the bar for an
encyclopedia, which is intended to serve as a summary for these types of
things.

Hit the sources and the transitive closure of references for more details.

~~~
taejo
> 3) When you have sufficient evidence, you upgrade your hypothesis to a
> theorem.

A theorem is a mathematical result: something proved logically from (possibly
physical) assumptions.

~~~
danparsonson
Such as the four colour theorem? en.wikipedia.org/wiki/Four_colour_theorem

~~~
archivator
_Especially_ the four colour theorem - the first mathematical theorem to be
proved with software. That said, I believe this discussion pertains to the
hypothesis -> theory "upgrade", not to theorems.

~~~
danparsonson
The point I was hinting at was that some theorems can be proven by a
sufficient body of evidence rather than requiring logical deduction - the four
colour theorem being a good example as it was proven by 'brute force' rather
than analytically.

~~~
andrewaylett
Doesn't a logical proof count as evidence? To my mind, these two methods are
demonstrating the same thing: considering all the possible inputs, we can show
[using logic|by testing them all] that the output meets our criteria.

To my mind, in this context, the difference between maths and physics is that
maths is exhaustive while in physics we don't usually have exhaustive evidence
so we have to work with what we've got.

~~~
danparsonson
Interesting question - to me, the distinction is that 'evidence' of the
validity of something is expected output(s) given known input(s), whereas
'proof' (at least in the mathematical sense) is a logical transformation that
is applied to make it obvious that the theorem must be true. I'm not sure you
could call a proof 'evidence' because it's not an output of the theorem - it
_is_ the theorem.

I'm less certain than I was before I read your post, though - so I stand to be
corrected :-)

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yo-mf
Considering that it has enough power to continue data communications with
Earth till 2025, it should be well into the heliosphere. If it keeps going at
its current speed of 17km/s, it should reach the nearest star by the year
75,787.

~~~
sesqu
Non sequitur much? Only two of those sentences have anything to do with each
other, and one factoid argues against the interestingness of another.

~~~
gphilip
>Only two of those sentences have anything to do with each other

Err.. I only see two sentences in total. Where is the non sequitur?

~~~
sesqu
Yeah, I meant clauses. Translation error.

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sown
I imagine that our descendants will have a certain kind empathetic pity on us
for not knowing this for certain in the same way we look back on people not
knowing what atoms were.

~~~
sharkweek
I love this -- it's always fun to think about what aspects of our modern
science people will one day scoff at.

Some I always consider:

\- Cures for disease

\- Our understanding of space

\- Transportation

~~~
smegel
Your assuming our descendants aren't living in a post apocalyptic dystopia
where civilized society is little more than a fairytale. We may seem like gods
to them. And it may be much closer than people expect, perhaps hundreds not
thousands of years.

~~~
jchrisa
or like 10 years

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s_kilk
I'm personally getting a little tired of this. It seems to me that every 2
months for the last few years I've seen a new article titled "voyager has left
the solar system". Perhaps I'm just ignorant but I can't help but think to
myself "what... Again? " each time I hear it.

~~~
raldi
You should try reading the article.

------
derleth

        Will she ever return? No, she'll never return.
        What knowledge we will learn!
        She'll voyage forever in the inky blackness.
        She's the probe who'll never return.
    

To the tune of "Charlie on the M.T.A.":

<http://www.mit.edu/~jdreed/t/charlie.html>

