
Paradoxes That Threaten to Tear Modern Cosmology Apart - gmays
https://medium.com/the-physics-arxiv-blog/the-paradoxes-that-threaten-to-tear-modern-cosmology-apart-d334a7fcfdb6
======
antognini
> What’s more, there is an energy associated with any given volume of the
> universe. If that volume increases, the inescapable conclusion is that this
> energy must increase as well. And yet physicists generally think that energy
> creation is forbidden.

It's important to remember that energy conservation is not an axiom of basic
physics. It is a consequence of Noether's theorem and temporal symmetry in the
laws of physics. In the framework of GR, this means that any static metric
will have some conserved quantity that corresponds to energy (though, in
general, it will not be the same as the Newtonian energy). But if the metric
is not static (as in the case of an expanding universe), there is no need for
energy to be conserved.

~~~
api
Tangential side question:

Must energy conservation be local? Would it be "legal" for -- say -- energy to
be spent/dissipated (entropy increase) at one location leading to an apparent
over-unity effect ("free" entropy decrease) somewhere else? I'm not talking
about energy transmission through wires or EM radiation... I mean something
apparently disconnected yet coupled.

I ask because I've encountered such ideas in sci-fi before and couldn't think
of a reason why they're forbidden -- though I have no idea how you would do
such a thing.

~~~
nitid_name
If it's coupled, wouldn't it cross the boundary of the system, and then be
included in normal entropy calculations as a flow across the boundary?

~~~
api
Exactly... just wondering if energy had to be conserved locally or globally?

Let me give you an example scenario:

Let's say (ignore the mechanism for now) that it's possible to send a small
amount of information from point A to B. This information takes a tremendous
amount of energy to generate at point A, and when it's received at point B it
can be used to (somehow) unlock a tremendous release of energy. If you only
looked at point B, it would look like you had an "over-unity device." But in
reality the energy spewing out at point B is paid for at point A, and the
information transfer by occurring at the speed of light does not violate
causality.

Not claiming it's _possible_ , just asking if it's expressly forbidden by
fundamental physics or not.

(If it _were_ possible it would of course open up all kinds of very amazing
things like remotely powered space propulsion, a whole next level of power
grid technology, or orbital solar power that actually worked, but I know of no
effect that accomplishes anything like this so it's total sci-fi even if not
forbidden by any known law.)

Edit: according to another response this likely is not possible. Oh well. :)

------
cristianpascu
I believe there are important social aspects of why/how the large public is
presented with certainty about what Science says and has discovered while
behind the scene things are not that pretty. It seems that we too often forget
that all of our beliefs are based on assumptions, some tested some not, some
testable and some not. This means that our efforts are always asymptotically
growing towards having true knowledge, as in a true justified belief. This
should force some sense of humility in us, specially when dealing to others'
beliefs. Religious or not.

~~~
aikah
Science isn't about "beliefs".Science is about facts.Science isn't afraid of
the unknown or to be challenged. Religion says one will rot in hell(whatever
it is) if one challenges religion. There is no knowledge in religion, as
religion doesn't explain anything that can be experimented by man kind.It's
just failed philosophy, and it's pretty arrogant. But you're right,both
religion and science are man made,they just have 2 opposite purposes.

~~~
cristianpascu
There are many fields in Science. It's one thing to say if we build this
bridge this way it will resist to an earthquake of this magnitude, and another
thing to say x years ago there was a population of humanoids that did this and
that. In the second case our explanation (composed of a set of sentences which
are beliefs to be proved as true) is constructed by inferences from our
observations (facts): this tool, that wall painting, whatever.

~~~
aikah
> It's one thing to say if we build this bridge this way it will resist to an
> earthquake of this magnitude, and another thing to say x years ago there was
> a population of humanoids that did this and that.

that's not a belief.You can experiment and reproduce that experiment.Whether
you get all the variables right is the issue science deals with.

You can't "experiment" god,heaven,hell or angels.These are fairy tales which
are based on nothing but ignorance.Their only purpose is power and control.
Religion is useless. If you crave for spirituality,then philosophy is a better
alternative.

------
coldcode
I've always thought that what we don't know is larger than what we do know,
except that we can't measure what we don't know. The universe is continuously
surprising. Each discovery winds up trumping the supposed status quo. Being a
cosmologist must be a lot like being a javascript programmer, every day what
you thought you knew is now obsolete.

~~~
rotorblade
> we can't measure what we don't know.

This is interestingly put, and I would not completely agree with it. Let med
give two examples:

1\. Before Quantum mechanics we could measure the Photoelectric effect (that
is, light that is energetic enough can shoot off electrons from metal plates).
This is a Quantum phenomena, and we could measure it before the theory was
discovered.

2\. Before General relativity we could measure the precision of the elliptical
orbit of Mercury. This could not be explained by Newtonian gravity, and is a
relativistic effect. But could be measured before the theory was discovered.

And before these; Electric eels can shock you, and Magnetic rocks still
attract each other, even before Maxwell, Ampere, or Coulomb were even born.

The problem now a days (for fundamental theoretical physics) is that we are
mostly put in the categories: * There is no data we can't explain with theory.
* Theory that is consistent with current data and only predicts new features
at much higher energies than we can design experiments for.

There are some exceptions to these, but I will exclude these for now, since
they are a bit technical. Example of the first one: There is no data directly
implying a quantum nature of gravity [1]. Example of the second one:
Supersymmetry might not be visible at LHC because LHC is too weak.

That second category is why people jump on new results directly, like the
BICEP or the super-luminal neutrinos, and the hep-th/ section of arxiv.org is
flooded with papers trying to explain it. However, for both these cases, the
measurements turned out be be wrong.

> every day what you thought you knew is now obsolete.

This is what many people say, but I would not agree (in fundamental physics).
For example:

* One can say Newtonian mechanics is wrong because we have Special relativity now. But one should say: There is a regime (high velocities) in which Newtonian mechanics breaks down. This regime is determined by the speed of light, c. Newtonian mechanics is still correct for velocities much smaller than c. * One can say that Quantum mechanics makes Newtonian mechanics wrong. But one should say: There is a regime where Newtonian mechanics breaks down and Quantum mechanics governs, which is determined by the Planck constant.

and so on. It is not "obsolete", or have not turned out to be wrong. One only
needs to append new aspects in various regimes.

[1] See e.g. [http://backreaction.blogspot.fr/2013/11/big-data-meets-
eye.h...](http://backreaction.blogspot.fr/2013/11/big-data-meets-eye.html) >
Those of us working on the phenomenology of quantum gravity would be happy if
we had data at all [...]

~~~
Strilanc
Wikipedia's list of unsolved problems in physics [0] includes problems that
aren't "no data we can't explain" and "we can't test it yet". They're more
like "we expect that the theory can explain observation X, but we don't know
how yet" and "we don't know what the theory predicts for situation Y". For
example:

\- Mechanism for baryon asymmetry

\- Mechanism for ultra high energy cosmic rays

\- Mechanism of high temp superconductors

\- Black hole information paradox

\- Finding solutions to the Schrodinger equation in various situations

You might mean something very specific when you say "Fundamental physics"
though.

0:
[https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_p...](https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics)

~~~
rotorblade
Oh, I do simplify a lot and hide myself under "Fundamental physics". You are
absolutely right to call me out on that. :-) But lets think about one of the
examples that you brought up:

> \- Black hole information paradox

This is indeed a big question, but I would discard this in what I wrote since:
What is the experiment here? There is theoretical evidence for the Black hole
entropy, but even if we could create black holes, which has so far not been
accomplished by the LHC, how would you measure it? It is a bit more difficult
than a gas where you could deform it and measure temperature etc.

So this I would discard because I was considering discrepancies between theory
and experiments.

> \- Mechanism for...

some of these I would exclude in what I wrote because they might be explained
by current theories, but it is just not known how exactly. Take ultra high
energy cosmic rays, there are Shock-front acceleration mechanisms, Supernovae
explosions etc that are candidates, and if I understand the formation of that
unsolved problem correctly it is to among these candidates identify the
correct one or the main one (or if the candidate is not among the ones we know
now, find a new one and explain it).

------
PhantomGremlin
That article didn't even mention dark matter and dark energy. Those also
"contradict basic physics" in the sense that they need to be conjured into
existence to explain our observations.

~~~
rotorblade
It does actually. The statement:

"What’s more, there is an energy associated with any given volume of the
universe. If that volume increases, the inescapable conclusion is that this
energy must increase as well. And yet physicists generally think that energy
creation is forbidden."

is regarding vacuum energy = dark energy = cosmological constant, etc, and
continues to discuss it after that.

Another thing I find annoying is when they (this article and also others I
have seen linked here on HN) paint the picture of that breaking energy
conservation is some kind of magic going on -- it is far from it.

In General relativity (GR) you can construct conserved quantities from Killing
vectors [1]. For example, if you have a time-independent metric (the GR tool
for measuring lengths in space-time) you get a time-like Killing vector, which
is associated to a certain conserved quantity; Energy. (Another example is
when the metric has certain angular independences and you get conservation of
angular momentum.)

Now in metrics that mimics cosmological evolution (that is, evolution in
time), you have to break time-independence, hence your time-like Killing
vector is gone and your energy conservation law is gone!

This is portrayed as some magic-like thing (at least that is how it sounds to
me when I read these popular cosmology articles), but it is simply a
consequence of the mathematics of GR. It might break some usual physics
intuition, but I would not say that physicists (at least in this field) are
surprised by it.

So it does not really "contradict basic physics", one just needs to know more
about the details to get a good view of it. We do not need to figure out (or
"conjure into existence") a way to break conservation of energy (as is the
example here), it is already there in GR.

[1]
[https://en.wikipedia.org/wiki/Killing_vector_field#Geodesics](https://en.wikipedia.org/wiki/Killing_vector_field#Geodesics)
The article on wikipedia is quite lacking on this point, but I link it here
anyway.

~~~
jpmattia
Nicely put, though I'd point out

> _It might break some usual physics intuition,_

It really shouldn't in light of Noether's theorem: The fact that time
independence of the action S gives rise to energy conservation in the first
place tells us pretty clearly: If your action has time dependence, you don't
have conservation of energy.

------
Lewton
> this change may be as much as one centimetre per second per year

Anyone have an idea what that's supposed to mean?

Edit: Ah, thanks to both of you, it seems obvious now

~~~
rotorblade
It has the unit-dimension the same of acceleration (that is
[Length]/[Time]^2), so it should be read as:

'Every year, the velocity of the distant quasars (going away relative us) is
increased by 1 cm/s.'

~~~
kordless
Could there be a similar observation of this if time were slowing slightly?

~~~
jdmichal
I don't see how. Also, what would "time slowing slightly" even mean? That is,
what frame of reference is time slowing against? How would we even measure
that effect, given that all of our tools which measure time do so my detecting
a fixed interval of it passing? Intervals which would also be "slowed".

~~~
kordless
To be more specific, if our reference time were slowing slightly, where 'our'
is defined as all humans and devices making the measurements.

~~~
wiml
I think our time would have to be slowing different amounts w.r.t. objects at
different distances from us. This would imply a Universe-wide effect on the
rate of passage of time which is coincidentally centered on Earth, or at least
on our group of galaxies. Universal expansion has the advantage that it
doesn't require the Earth to happen to be at a special privileged point in the
cosmos.

------
jchomali
I totally agree with you.

------
eip
I want to see a picture of the sun in the visible spectrum taken in free space
or from the moon.

~~~
kryptiskt
This is the sun right now:
[http://sohowww.nascom.nasa.gov/data/realtime/hmi_igr/1024/la...](http://sohowww.nascom.nasa.gov/data/realtime/hmi_igr/1024/latest.jpg)

"The MDI (Michelson Doppler Imager) images shown here are taken in the
continuum near the Ni I 6768 Angstrom line. The most prominent features are
the sunspots. This is very much how the Sun looks like in the visible range of
the spectrum (for example, looking at it using special 'eclipse' glasses:
Remember, do not ever look directly at the Sun!). The magnetogram image shows
the magnetic field in the solar photosphere, with black and white indicating
opposite polarities. " from:
[http://sohowww.nascom.nasa.gov/data/realtime/realtime-
update...](http://sohowww.nascom.nasa.gov/data/realtime/realtime-update.html)

~~~
pavel_lishin
I'm trying to use [http://seal.nascom.nasa.gov/cgi-
bin/gui_seal](http://seal.nascom.nasa.gov/cgi-bin/gui_seal) to get some of the
recent images from that particular instrument, but can't figure it out - no
results are returned for my search query:
[http://i.imgur.com/ANlgBT4.png](http://i.imgur.com/ANlgBT4.png)

Anyone know what I'm doing wrong?

Edit: this might be a better resource, and can automatically show you an
animated sequence: [http://sohodata.nascom.nasa.gov/cgi-
bin/data_query](http://sohodata.nascom.nasa.gov/cgi-bin/data_query)

~~~
mturmon
MDI is no longer operational. It operated from 1996-2010. So your query for
2015 comes up empty.

The successor instrument is called HMI, which returns 4096^2 images on a
pretty fast cadence (45s or 720s depending on your purposes). It is much
superior to MDI. The HMI instrument team is at Stanford University, so I'd
point you there for data rather than to the NASA site, which offers a lot of
sources and seems to suffer from a least-common-denominator effect.

Recent HMI quick look products are here:
[http://jsoc.stanford.edu/data/hmi/images/latest/](http://jsoc.stanford.edu/data/hmi/images/latest/)

There is a back-catalog of JPEG images for browsing:
[http://hmi.stanford.edu/data/hmiimage.html](http://hmi.stanford.edu/data/hmiimage.html)

For science purposes, you can get FITS data from
[http://jsoc.stanford.edu](http://jsoc.stanford.edu) . There are a lot of data
products -- intensity, magnetic field (line-of-sight and vector), velocity,
tracked regions, etc., as well as near-real-time analogs of much of this data
(not as well-calibrated, but arrives within a couple hours of being taken).

There is no embargo on this data. They just expect acknowledgement
([http://sdo.gsfc.nasa.gov/data/rules.php](http://sdo.gsfc.nasa.gov/data/rules.php)).

~~~
pavel_lishin
Thank you!

~~~
mturmon
My pleasure. I developed a data product for both instruments.

