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?
Others replying to you are wrong in suggesting that evidence for dark matter comes only intragalactic scales. In fact, there is evidence for dark matter at the much larger scales on which galaxies and galaxy cluster clump.
From reading the article, I believe this is literally just a finding about how many galaxies into which the known amount of matter was clumped in the distant past, i.e., more galaxies with less average mass.
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.
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.
My understanding is that dark matter was "discovered" when trying to find out why stars in the outer edge of a galaxy rotates with the same speed as the inner. A ten-fold increase in number of galaxies doesn't seem to affect this.
Potentially, there likely still be "dark matter" but it might we might not need e a new classification of dark matter.
We've known for a while now that there seems to be more galaxies out there, heck before the hubble went up we didn't even knew how much there is.
There are also indications that there is considerably more intergalactic material out there than we've suspected before.
However the problem is that "dark matter" is also needed on local scales, including our solar system; this is a good read http://scienceblogs.com/startswithabang/2013/01/18/why-the-u....
So "dark matter" is needed to explain our current model of gravity both local and global scales; it is important to note tho that "dark matter" is a placeholder it doesn't necessarily have to be a new type of matter (e.g. AXIONs), some irregular mode for normal matter (e.g. WIMPs) or or it can be regular matter which isn't easily observable (e.g. MACHOs) or it can be also be any combination of the above, and things we haven't even considered yet.
Alternatively we might need to rethink our understanding of gravity, and of the existing forces in general, a good point to note is that gravity isn't a traditional force in the first place which already sets it apart from the bunch (it's a property of the distortion of spacetime, it also is only attractive unless dark energy is somehow a very low/zero value property of the gravitational field).
So gravity might not work like we think it does, it might be hiding another elementary force, or it might be that gravity on certain scales/conditions splits into multiple forces similarly to how the electroweak force works (at some point during/prior to the big bang all forces/fields were unified at least in theory).
Mainstream Physics have been stuck somewhat for a fairly long time on certain aspects, there is also quite a bit of misconception about what works and what doesn't for example most people think that quantum gravity doesn't work which it does, you can use it for everyday life and for many other things, you can't use it during the big bang (and shortly after) and it breaks down near very strong fields e.g. a singularity which is also the internal killswitch or "mathematical contradiction" embedded within general relativity where gravity and spacetime as we know it break down.
My understanding of the article is that the answer is: No.
"found that 10 times as many galaxies were packed into a given volume of space in the early universe than found today. Most of these galaxies were relatively small and faint, with masses similar to those of the satellite galaxies surrounding the Milky Way. As they merged to form larger galaxies the population density of galaxies in space dwindled. This means that galaxies are not evenly distributed throughout the universe's history,"
I read this as they did not find new visible matter, but they discovered that the visible matter was distributed in many more small galaxies compared with today. I could be wrong though, I'm by no means an expert in this field.
As others have said, the argument for dark matter is based on stars within galaxies, not on the number of galaxies. What this does, though, is change the total mass of the universe (I presume). That might have implications for dark energy (rather than for dark matter), but I can't tell you what the implications actually are.
My layman guesses. The ratio of baryonic and dark matter remains unchanged because the new galaxies come with their own dark matter and we can determine the ratio from looking at individual galaxies. The amount of baryonic and dark matter in the universe goes up by a factor of ten unless the new galaxies are exceptionally small or large which would change this factor accordingly. Finally the amount of dark energy goes up to yield the observed expansion rate, no idea if that also means a factor of ten in which case the relative composition of the universe would remain unchanged.
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.
And don't forget about invisible «almost stars», Jupiter like systems, which outnumbers visible stars (IMHO), with their own planets (satelites?) and asteroids.
This Quora answer (https://www.quora.com/What-is-the-average-number-of-planets-...) takes a dataset of 2560 stars and comes out with an average of 1.3 planets per star. As the author caveats, this is an extremely small sample and probably not accurate, but it's something to start from.
The way we detect planets only detect some of them.
The best method is to notice when a planet passes in front of its star, by how it gets slightly dimmer. That only works if its orbit happens to be directly between us and that star.
We can also detect them by a Doppler shift of the star, because the planet (if big enough) will move the star as it orbits. This works when the transit method fails, but provides fewer data on the planet itself.
Caveat++++: Factor in rogue planets that don't orbit any stars, or large asteroids drifting through nebulas etc...
I'm sure the number of solid bodies — potential habitats for life or artificial constructs — in our universe is magnitudes larger than the number of stars we've detected, and the latter is already a mind boggling quantity.
I would tend to agree. The effective gravitational influence of a star would be relative to its mass. We can pretty easily determine the (rough) mass of a star, and ours appears(?) to be somewhere in the middle, so it stands to reason that 8-ish decently sized planets is not an unreasonable number.
That doesn't hold I'm afraid. The newly discovered galaxies are small and dim, so won't change the numbers very significantly. It's not as radical a discovery as it appear at first glance.
If...the biggest two letter word in the English language.
Given how little we actually spend on this sort of stuff, I'd be happy if we could save Hubble, rather than let it retired and reenter the atmosphere and burn. Perhaps a robotic mission to repair it in 2025 can be added to our big plans to go to Mars, etc.
Given that probably most of the cost of the Hubble is R+D, another one could be built and launched for only a fraction of the cost of the original. 3 or 4, even lesser.
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?
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.
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."
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.
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?
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.
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.
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.
The nighttime sky is filled with light. It's called the microwave background radiation. It's the light from the fiery hot stuff that was in existence in the very early universe, and it has travelled vast distances. It just happens that it has been red-shifted so much that it appears dark to your eyes.
Olbers' paradox is based on the assumption of an infinite static universe. Taking that assumption you arrive at the paradox. So therefore the assumption must be wrong - ergo evidence for the big bang model which solves the paradox.
It's impossible because of laws of thermodynamic. Star can heat it surroundings up to temperature of it surface, and with distance this temperature drops in proportion to square of distance. For example, Sun surface has temperature of 5800K, but it can heat surface at Earth only up to 450K, because surface of sphere at Earth orbit is much much larger than surface of Sun. Interstellar light cannot heat for more than fraction of Kelvin.
You're forgetting to sum over all the visible stars in the sky, which just brings us back to Olber's Paradox.
Think of it another way—if you're in an oven at 5800K, there is no arrangement of matter you can put inside that will not eventually come to thermal equilibrium.
You're forgetting to divide that sum by distances to these stars in square. Thermal equilibrium inside oven and in few light years outside of oven are two very different things.
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."
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.
It is spherical and it is the distance light could travel in the 13.7 billion years since the big bang, or more precisely since when the universe got cold enough to allow electrons and protons to form atoms which in turn made the universe transparent to light and which occurred about 400,000 years after the big bang. Note that the radius is about 46 billion light years and not only 13.7 billion light years because the universe continued to expand while the light was on its way to us. This also changed the frequency of the light and so the light emitted at the edge of the observable universe at the time of recombination is the cosmic microwave background we receive today.
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.
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.
The space between various parts (if there is more than we can see) is growing faster than the speed of light, eventually it will get to the point where even nearby galaxies disappear.
Nearby galaxies will only disappear for practical purposes: Their light emission will continue to reach us, it just gets increasingly redshifted. In fact, if we were able to detect them, we would continue to discover more and more galaxies, but the total number will asymptotically approach a fixed value (ignoring the change in numbers due to galactic evolution).
No, I think flukus is right. The space itself between galaxies is expanding (and the expansion is accelerating), which means, so eventually even our closest neighbour Andromeda will disappear behind our observable horizon and be eternally inaccessible, in all regions of the electromagnetic spectrum. It's counter-intuitive, but a good way to visualize is by imagining miniature galaxies printed on an expanding balloon (with the expansion speeding up), and then imagining what happens to a photon leaving galaxy A and travelling "towards" galaxy B - you'll notice that if the balloon is expanding rapidly enough, the photon ends up moving away relative to both A and B.
Instead of an expanding balloon, just use a flat piece of paper as your model of space-time (after dimensional reduction):
Due to conformal flatness of the FLRW metric, it's possible to represent the Hubble flow as vertical lines, the spatial surfaces at constant cosmological time as horizontal lines and light rays as straight lines angled at 45°. The geodesics for massive particles not following the Hubble flow however would be more complicated, but are of no particular interest.
The big bang happens at the lower edge of the paper, the upper edge represents t=inf. The observable universe is bounded by two light rays that meet at infinity. In our toy model with 1 spatial dimension, if an observer follows the Hubble flow along a vertical line, the number of observable galaxies will be proportional to the width of the intersection of the cone formed by light rays and the horizontal line representing space at the time when galaxies first formed.
Galaxies that are visible right now will continue to be visible forever in theory, but may become undetectable in practice due to increasing redshift. They will also not be seen to cross any 'edge of the universe', but instead appear to become fainter, redder and frozen in time.
As time goes by, we will continue to observe new galaxies being formed, which increases the total number of theoretically visible galaxies. In practice, redshift may again prevent us from doing so in practice.
The observable universe is finite as according to our current models, light emitted beyond a certain distance will never reach us. The global size beyond the oberservational limit is harder to tackle. You're right that even though the observable universe is finite, it's volume is potentially increasing forever.
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?
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.
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.
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...
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).
> 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?
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.
> 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.
> > 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.
My bet they will. As soon as VR gadgets become more realistic, people will start asking more philosophical questions. Let's talk about it in 10 years :)
People have been asking these questions for thousands of years.
Take a look at Hindu mythology. The idea that the world is an illusion or a dream was quite common as far back as 3 or 4 thousand years ago, and has lasted on through the present.
Another version of that belief was made famous by Plato 2500 years ago. Then Zhuangzi's famous "Now I do not know whether I was then a man dreaming I was a butterfly, or whether I am now a butterfly, dreaming I am a man." came about 2300 years ago. Then yet another version by Berkeley about 250 years ago.
The whole "the universe is a simulation" is just the most recent variation, that came about with the advent of computers.
The Upanishads posit a reality of consciousness that upends the common ("worldly") conceptualization: dream state was held to be a higher and more fundamental experience of reality. In this sense, the "worldy" experience was actually "slumber" and the dream world more "real". In the Gita, Krishna declares that what common people experience as "day" and "awakened" is "night" and "sleep" for the yogin.
The Sufis symbolized the worldly existence and our apparent multiplicity as 'foam on the surface of an ocean' (c.f. Quantum cosmology and quantum foam), with the true reality being the eternal sea.
In both, "the Real" is the true Self, the "infinitesimal" that is "the Most High"; and the "outward world" the microcosom and the true macrocosom the inner reality of Man.
There are Hindu myths that speak of the world being a dream of Brahma (or of Vishnu, depending on the myth), and of the world ending when the dreamer awakes.
Buddhism (how could I have neglected to mention it?) also has the illusory nature of the world (and of the self) as a central tenet -- though what that actually means varies with the strand of Buddhism you're talking about.
The world as illusion was even a belief of some Gnostics, who lived a couple of thousand years ago.
To complete this list (and also follow up to your hoped-for "escape from the simulation" /g) the Qur'an explicitly says that "this life is an illusion and a pastime" and in the Sura of the Jinn, we are informed by these non-Human sentient beings that they have been trying for a very long time to escape but have always been frustrated in their attempts.
Regarding Buddhism, in the Lotus Sutra, the Buddha, to the apparent dismay of a few thousand attendees -- they get up and leave! -- informs that the Three Vehicles are merely devices to reach various levels of understanding, and that this world ("a burning old house") was an attraction that attracted his children but unfortunately they got caught up in the illusion and now need enticements (the Three Vehicles) to rescue them from the burning old house.
People in this thread are being way too dismissive of an idea that couldn't possibly have been expressed or understood without modern computational science, specifically the notion of Turing equivalence.
True, but this new variation is fundamentally different exactly because now it's not just an abstract process of unknown nature, but a "computation". It will be interesting to see how the idea will be reconciled with "science". E.g. with "random mutations" allegedly driving evolution, to name just a single aspect.
