NASA perplexed by galaxies heading in a particular direction | Hacker News Reader

NASA perplexed by galaxies heading in a particular direction

nasa.gov

28 pointsanigbrowl21 comments

From the PR: “This is not something we set out to find, but we cannot make it go away […]”

One can only imagine the drama if somone were to find such a sentence in a climate related PR :)

Creationists are already formulating their replies...

The difference is that this is a public rather than a private statement so the context is obvious. Specifically "we don't understand what's going on, we've tried to explain it in different ways, and can't, yet" vs. "I've succeeded in hiding important faults in this research, don't tell anyone".

I am always amazed by the amount of new discoveries that are still possible in science. We might think that we have an adequate picture of our universe and how it operates, but then we discover yet another subatomic particle or another strange fact about the movement and organization of the galaxies.

For all we know the smallest subatomic particles yet discovered may be made up of yet smaller subatomic particles, and the laws of physics that we use today will be completely invalidated by a future better understanding of dark matter and its effect on our universe.

It is humbling and incredible to think about how much there is yet to discover.

This one is always fascinating for me to think about:

> There is considerable speculation as to why the observable universe is apparently almost entirely matter, whether there exist other places that are almost entirely antimatter instead, and what might be possible if antimatter could be harnessed, but at this time the apparent asymmetry of matter and antimatter in the visible universe is one of the greatest unsolved problems in physics.

http://en.wikipedia.org/wiki/Antimatter

You don't even have to go as far as dark matter, dark energy, or indeed space at all to find amazing undiscovered principles in physics. For example: put a ball on your desk. Now push it. Did it resist? Why? Well, sure, there's a component of friction, but even without friction it would resist your push...so, why? Inertia, right? But where does inertia come from?!? http://en.wikipedia.org/wiki/Inertia#Source_of_Inertia

> then we discover yet another subatomic particle

I guess that is a general principle: Just look at the thing (= what you have/what we know so far), then zoom in, ask: "Why is it that this is how it is?"

I guess you can do that on and for just anything we know, therefore we won't ever have a complete picture.

The BBC covered this phenomenon in a hour long program on Tuesday. For any one who can get it or is interested, link below.

http://www.bbc.co.uk/iplayer/episode/b00rgg31/Horizon_200920...

Discounting the sensational title, the click-to-show-text Programme Information has a simple summary:

There's something very odd going on in space - something that shouldn't be possible. It is as though vast swathes of the universe are being hoovered up by a vast and unseen celestial vacuum cleaner.

We barely know anything about cosmology at all, when you get down to it.

Why do you say that?

Because there are so often things we discover we're fundamentally wrong about. It's really a pretty thin science based on a lot of assumptions and inferences.

It's very safe to say most of what we know about cosmology is wrong, and a large portion of it is probably deeply wrong.

I would imagine cosmologists know where the boundaries are between what we know, what we don't know, what we "might know" (i.e. the status of various hypotheses and theories with regards to supporting evidence). I think it's safe to say that there is a lot of stuff in each of these categories.

It would be pretty surprising if we're "fundamentally wrong" about cosmology, given that scientists are aware of what goes where, with respect to these categories. Plus, I'd imagine a lot of cosmology is purely observation, anyway, and you can't be "wrong" about observation.

There is a lot of room between "omniscient" (which many people mistakenly demand of science) and "wrong". In other words, science can and must deal with partial knowledge.

Cosmologists have pretty wide agreement on, for instance, the order of events in the first second. See http://en.wikipedia.org/wiki/Inflation_%28cosmology%29 for details.

Those events took place under conditions of gravity, temperature and pressure that we can't reproduce.

Those theories include belief in a phenomena called inflation which is not predicted by any theory we have in physics today, and which has some internal contradictions. (See http://www.edge.org/q2008/q08_4.html#Steinhardt for an explanation of some of them.)

Oh, and the thing we can look at to test these theories? That's the cosmic background radiation which is believed to have been formed several hundred thousand years later.

Are you still confident in what scientists currently claim about cosmology?

That's the thing, it's mostly all stuff we "might know". And most of the observations are based on a lot of assumptions and inferences. It's not like "how much liquid is in this vial". The measurements and observations depend on a chain of things being true that might not be true.

Seriously, what are you talking about?

We know a lot about cosmology. In particular there is very good evidence for for the basic model: hot big bang, cold dark matter, accelerating expansion, geometrically flat, ~14 billions years old (see http://www.astro.ucla.edu/~wright/cosmology_faq.html for more).

Granted we don't know what the dark matter is, and we don't know what's causing the acceleration. Those are big unknowns! But the basic picture is pretty well understood. And I think it's very unlikely that much of this picture is "deeply wrong".

I mean, what do you think? Some day we are going to discover that the universe wasn't really denser and hotter in the past? That the universe isn't really expanding? That baryonic matter makes up all of the mass of the universe?

The very faq you link to uses cautious language. Look at "currently most accepted model" right there in the first question.

If you've followed cosmological history at all, it's been a cascading series of big changes decade after decade.

I'm virtually certain the model of 2030 will vary in deep, significant ways from the model of 2010.

Can you be more specific? What parts of the "hot big bang, cold dark matter, accelerating expansion, geometrically flat, ~14 billion years old" model will be shown to be "deeply wrong"? Do you think that discovering, say, the nature of dark energy, is going to demonstrate that the universe isn't really expanding? That we are going to discover that the universe is really 100 billion years old? That the universe was actually colder and larger in the past?

You're both correct. We know a lot about cosmology compared to what we knew, say, 100 or especially 200 years ago. Many of the big, open cosmological questions throughout human history (what is the Universe, how was it created, how old is it, what are the stars, what powers the stars, how far away are galaxies, etc, etc) have been answered.

We should not downplay that remarkable achievement. We know the age of the Universe to high precision, despite the fact that that age is fully 6 orders of magnitude greater than all of human history.

Nevertheless, there is still much we don't know, and likely what we don't know easily exceeds what we do know, by a fair margin. We do not know the nature of the majority of dark matter, we do not know the nature of "dark energy", we do not fully understand why the Universe is filled with matter rather than just energy, etc.

waterlesscloud is not saying that there is lots we still don't understand. He is saying that much, perhaps most of what we currently believe is "deeply wrong". This is of course possible, but I think it is very unlikely.

There is a big difference between saying that our current model is "deeply wrong" and saying that our current model might be superseded by a later model which encompasses the current observations. Therefore the major assumptions of the current cosmology are not likely to be "deeply wrong" anymore than Newton's theory of gravity was "deeply wrong" just because it was superseded by general relativity.

I do believe that our current understanding of cosmology has hardly scratched the surface of describing how things really are. However, any future model is not going to invalidate current observations, but rather, better explain them.

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