
Hubble Finds 10 Times More Galaxies Than Thought - lx
http://www.nasa.gov/feature/goddard/2016/hubble-reveals-observable-universe-contains-10-times-more-galaxies-than-previously-thought/
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danbruc
Does this have any implications for the amount of dark matter or do estimates
of the energy content of the universe not rely on the number of observed
galaxies? If the number of observed galaxies does not matter, how do we
account for this factor of ten? Galaxies are probably not ten times lighter -
ignoring dark matter - than previously believed. Are those missing galaxies
just very light? Is the universe heavier than previously assumed? How does
that change the expansions of the universe? Does there have to be even more
dark energy to compensate for this additional baryonic matter to match
observed expansion rates?

~~~
netcraft
I don't think our evidence for dark matter comes from interactions between
galaxies but within a galaxy - the interaction of matter within the galaxy and
the amount of lensing observed because of the amount of observed matter in a
galaxy - in other words I dont _think_ that this will do much to the dark
matter calculations - but I am not certain and hope someone knowledgeable will
come along and set us straight.

~~~
flukus
One line of dark matter evidence is galactic clusters, though I'm not sure
what the distribution of these "new" galaxies is and whether it would affect
this.

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ciphre
So, instead of 200 billion galaxies, the number would be closer to 2 trillion
galaxies. I thought the first number seemed like a lot, wow. I wonder how many
stars there are if that is the case. At 100 billion stars per galaxy, the
number would be 2×10²³ stars. I believe that's 2000 billion trillion.

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yummybear
Multiply that with about 5-10 for planets. Mindboggling.

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pmoriarty
Then figure in the dwarf planets, asteroids, and comets, and we'll start to
get to some big numbers.

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lisivka
And don't forget about invisible «almost stars», Jupiter like systems, which
outnumbers visible stars (IMHO), with their own planets (satelites?) and
asteroids.

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WalterBright
Hubble has been so incredibly productive, if I had mega-billions I'd fund the
construction and launch of several more of them.

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laxd
Only two years until James Webb telescope launches. Should keep us entertained
for while.

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pmoriarty
I like this size comparison:

[https://upload.wikimedia.org/wikipedia/commons/4/42/JWST-
HST...](https://upload.wikimedia.org/wikipedia/commons/4/42/JWST-HST-primary-
mirrors.svg)

~~~
jessriedel
Note that Webb is an IR telescope, which is longer wavelength, so the
resolution actually is comparable to Hubble.

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jm547ster
Does it offer any advantages to Hubble?

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jessriedel
It's highly complementary. IR astronomy is essentially a different field.

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michaelmachine
There are also galaxies that are 99.9% dark matter apparently [1]. I don't
think they are counted in this survey.

[1]: [http://www.skyatnightmagazine.com/news/galaxy-
found-9999-dar...](http://www.skyatnightmagazine.com/news/galaxy-
found-9999-dark-matter)

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daveloyall
Regarding Olbers' paradox, the explanation that the article gives contradicts
what I heard elsewhere...

I heard that the nighttime sky is dark simply because the universe is to young
for the whole thing to get filled with light, though that will happen
eventually.

Crap, I can't remember where I read that. Somewhere linked off of HN.
Nautil.us?

~~~
danbruc
This will not happen, the accelerating expansion of the universe will make
more and more galaxies end up behind the horizon of our observable universe
even though the horizon itself keeps expanding.

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pmoriarty
It would happen if there's a big crunch.

Also, a lot of astronomy goes on the assumption that the laws of physics are
the same far away as they are near by, and that they don't change over time.
It's possible that if either of these two assumptions are incorrect that
anything goes.

I'm also reminded of Arthur C. Clarke's famous dictum that, _" when a
distinguished but elderly scientist states that something is possible, he is
almost certainly right. When he states that something is impossible, he is
very probably wrong."_

~~~
danbruc
But the expansion of the universe is accelerating which tells us we are not in
a big crunch scenario. And we have probed the laws of physics over very long
distances and far into the past by looking at very distant objects and have to
date not found any strong evidence for varying laws of physics over space or
time. There are for example some claims of variations in the fine structure
constant but as far as I can tell those claimed variations may still be
explained by experimental errors and are therefore not widely accepted.

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Rzah
If space is curved rather than flat we could still have a big crunch on the
far side.

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jryan49
I think consensus is that it is flat and we keep finding more and more
evidence suggesting so.

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daveloyall
I heard that "if you go straight long enough, you end up where you were", as
analogous to walking on the surface of a globe. Are you saying that evidence
against that has surfaced?

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cygx
The current assumption of the cosmological standard model is spatial flatness,
which is compatible with the observations. In principle, space could still
curve back on itself on a large enough scale, but assuming there's no big
crunch coming, you'd have to go straight for a longer-than-infinite duration
to come back to the place you started from.

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daveloyall
Longer than infinite?

What does a big crunch have to do with it? Maybe I don't know what a big
crunch is... I currently think the big crunch is the idea that gravity will
eventually coalesce all matter into a single point.

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cygx
_Longer than infinite?_

In an expanding universe, objects can be separated by a cosmic horizon.
Nevertheless, from the comoving perspective, they may very well still move
towards each other - but without ever meeting up. However, if you extended
conformal time beyond infinity, they would. That's of course not physically
possible, so that particular comment was tongue in cheek.

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verytrivial
Nitpick: It is more "Hubble data postulates existence of 10 x technically
observable galaxies based upon their massive distance and hence age, and the
rate at which galaxies eat each other over time."

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stephengillie
If the universe is infinite, then aren't there infinite galaxies within it?

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danbruc
The number of galaxies is always for the observable universe - about 92
billion light years in diameter if I remember correctly - not the entire
universe. From the observed flatness of the observable universe we know that
the entire universe is at least about 100 times larger in volume assuming it
is isotropic.

~~~
daveloyall
What defines the horizon?

Is the horizon spherical?

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AnimalMuppet
> What defines the horizon?

The speed of light. Things beyond the horizon are things where the light
hasn't had time to reach us yet.

> Is the horizon spherical?

Given that the speed of light is isotropic, yes.

~~~
thaumasiotes
>> What defines the horizon?

> The speed of light. Things beyond the horizon are things where the light
> hasn't had time to reach us yet.

No. Things _within_ the horizon are things where the light hasn't had time to
reach us yet.

Things _beyond_ the horizon are things where no amount of time will ever
enable the light to reach us. That's what makes it "unobservable".

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danbruc
That seems wrong to me but maybe I am just misunderstanding you. The light
from the particle horizon is by definition the light arriving here now.
Whether light emitted on either side of the particle horizon will reach us
depends on whether the emission happens within the cosmological event horizon
which only coincide with the particle horizon in a non-accelerating universe
and changes over time in an [de]accelerating universe.

If we move away from an observer in our accelerating universe we first pass
objects that can still emit light that can reach the observer, then we pass
the cosmological event horizon and enter a region where objects were once able
to emit light reaching the observer but which are now moving away to fast for
they light emitted now to ever reach the observer and finally we pass the
particle horizon and enter the unobservable universe where objects were never
able to emit light able to reach us.

This may sound contradictory but one mus keep in mind that objects between the
cosmological event horizon and the particle horizon emitted light in the past
that is still on its way to us so that we can still observe those objects for
some time but they can just no longer emit light that will reach us.

Also note that I avoided talking about the inside and outside of horizons
because I am not sure what side is usually called the inside respectively the
outside. From the point of view of an observer he is inside the horizon, on
the other hand in analogy with a black hole where the horizon prevents light
reaching an observer outside the horizon we would have to call the observer
outside of the horizon. I think the former point of view is the common one but
I am absolutely not sure about that.

EDIT: Replaced Hubble horizon with cosmological event horizon as pointed out
by cygx.

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cygx
Physically, the Hubble 'horizon' is mostly meaningless. What you have in mind
is the cosmological event horizon.

Both can be defined in terms of certain velocities reaching c: The hubble
sphere is located where the change in proper distance at constant cosmological
time reaches the speed of light (aka recession velocities), the cosmological
event horizon is located where relative velocities as evaluated by parallel
transport along the light path does so.

~~~
danbruc
Thanks, updated my comment accordingly.

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achr2
I have wondered for a while how we can be certain that looking so deeply into
the distant (meaning past) universe gives an accurate picture. Wouldn't there
be many compounding effects, such as gravitational lensing combined with
expansion, that could be showing us a very different picture than the true
structure of the universe?

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andersonsantos
Elon Musk is right, we do live inside a computer simulation. After spending a
considerable amount of time analyzing the galaxies images used on this NASA
article I'm comfortable to assure you, those galaxies are a computer's desktop
wallpaper.

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Pigo
This reminds me of the first time I seen Saturn through a powerful telescope.
It looks cartoon-ish, or like a painting, even when you're not viewing it
through some kind of media. It felt oddly synthetic.

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hawski
Would that information extend our current estimation of heat death of the
universe?

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platz
does this also affect the friedman equation?

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heldrida
QA finds 10 times more bugs than thought.

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lohankin
Can it be that in 10 years, everybody will believe that we live in simulated
reality, and these galaxies are created on demand when we stare into
particular region of space? Elon Musk says he thinks so:
[http://motherboard.vice.com/read/elon-musk-simulated-
univers...](http://motherboard.vice.com/read/elon-musk-simulated-universe-
hypothesis)

~~~
duaneb
What's the point about asking untestable questions? You might as well become a
theoretical physicist or a priest.

~~~
smac8
Because they are interesting and fun to think about?

Because they may create new ideas which impact models, frameworks, directions,
and analogies of thought in experimental and theoretical disciplines of the
same or differing subjects?

Because not everything is testable, or even when it is the number of variables
simply makes controlling the experiment for accurate causal derivations
difficult to impossible? (increasingly true as science progresses, often
leading to false levels of confidence).

Hmm......

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duaneb
> Because they may create new ideas which impact models, frameworks,
> directions, and analogies of thought in experimental and theoretical
> disciplines of the same or differing subjects?

How do you figure? Whether we are in a simulation is a) unknowable by
definition, or it's not a very good simulation, and b) doesn't change anything
about how our universe works from our perspective. Why would speculation about
"why" impact anything about the decisions we make?

~~~
pmoriarty
If someone thought they were in a simulation, they might try to find a way out
of it, or might start not taking life seriously.

If, as most people, you think that one's beliefs shape one's actions, then it
should be pretty clear that a belief that we live in a simulation could lead
to some people acting differently based on that belief.

Only if one did not have free will or if one's beliefs did not shape one's
actions would such a belief have no potential impact.

~~~
duaneb
> If someone thought they were in a simulation, they might try to find a way
> out of it

This is completely nonsensical.

> or might start not taking life seriously.

People already do this just fine.

> Only if one did not have free will or if one's beliefs did not shape one's
> actions would such a belief have no potential impact.

Free will is a pretty thought, not anything to do with a simulation theory.
Why does it matter whether you are forced to bow down to physical laws vs
simulated physical laws? You can tell yourself whatever you want, but you
gotta bow.

~~~
pmoriarty
> > If someone thought they were in a simulation, they might try to find a way
> out of it

> This is completely nonsensical.

It really depends on the nature of the simulation. For example, if the
simulation was something like what was depicted in _The Matrix_ , where one's
experience or senses were being simulated while one's real body was outside
the simulation, then it could be possible to find a way out.

Of course, if your entire existence was simulated and you had no existence
outside the simulation, then it would be more difficult, but perhaps even then
not impossible, depending on whether you believed that a copy of yourself was
still you. For instance, one could conceivably "upload" a copy of one's
mind/brain in to a robot that was external to the simulation and that robot
could then potentially have access to sensations/experience outside the
simulation. Of course, then it could be argued whether that's another
simulation.

But the potential for whatever is "outside" the simulation being just another
simulation (ala _Inception_ ) is always there. And I'm not sure how one could
ever be certain one was ever really "outside" and not just in another
simulation -- though it might be possible that one really is "outside" without
being certain of it. Or one could be certain and mistaken, or certain and
correct. But then one could always be mistaken.

> > or might start not taking life seriously.

> People already do this just fine.

I meant people who took their life seriously because they thought it was
"real" and then finding out that they and everyone/everything around them was
simulated might decide, as a result of this realization, to no longer take
life seriously. For example, they could have valued human life before, but
when realizing that the beings they thought were alive before actually
weren't, then they could start not valuing them anymore.

Of course, some people don't value their own lives or those of others
regardless, and don't take their life seriously anyway.. but I'm not talking
about them.

> Free will is a pretty thought, not anything to do with a simulation theory.

The point of bringing up free will was to show under what circumstances one's
beliefs would not have any impact on one's actions. Those circumstances are
ones in which one does not have free will.

If one does have free will, and one's actions really are shaped by one's
beliefs, then the belief that one is in a simulation could have an effect on
what one does.

If one does not have free will, or one's actions are not shaped by one's
beliefs, then the same belief would not have any effect one what one does. One
would do what one was determined to do regardless.

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wruza
>the potential for whatever is "outside" the simulation being just another
simulation (ala Inception) is always there

Original scenario of The Matrix had it until some businessman decided to turn
it into another happy-end hollywood crap, afaik.

