This is a guest post by Daniel LaVine.
Before the 1920′s, the Milky Way galaxy constituted the whole of existence — so far as astronomy was concerned. No one knew there was more to the universe than our own galaxy. We know, now, that there are more than 80 billion galaxies just like our own.
The Universe Gets Bigger
Pullquote: The universe is not only queerer than we suppose; it is queerer than we can suppose.
In the early years of that decade, an astronomer named Edwin Hubble began studying a class of fuzzy objects in the night sky known as “spiral nebulae.” He discovered that some of the tiny points of light contained in these so-called nebulae would increase in luminosity (the object’s intrinsic brightness) to a point and then decrease in luminosity, with the high point, low point, and the time between them remaining constant for each one.
Hubble noticed this behavior was similar to variable stars, which were already extensively studied. A type of variable star called a Cepheid variable was particularly useful to Hubble, as the luminosity of these stars correlates perfectly to the amount of time it takes them to go from dimmest to brightest to dimmest again (the period).
By comparing the theoretical value for the brightness of these objects (derived from the period) to the measured brightness, Hubble made an astounding discovery: the closest spiral nebula was 250 million light years away — 2,500 times the diameter of the known universe at the time! Clearly, these were not like other nebulae in the Milky Way, and the best explanation for their appearance was that they were other galaxies similar to our own but quite far away.
Doppler Shift
Pullquote: In the beginning the Universe was created.
This has made a lot of people very angry and been widely regarded as a bad move.
In addition to this discovery, Hubble added to the work of other astronomers who had already discovered that the light emitted by these objects is Doppler shifted. Most people are familiar with Doppler shifting from emergency vehicles, whose sirens sound high-pitched when traveling towards the observer, and then suddenly become much lower-pitched as the vehicle passes and begins to move away from the observer.
Similarly, Hubble found the frequency of the light emitted by these stars was “low-pitched,” indicating these galaxies were speeding away from our own galaxy. This observation could only have one of two interpretations: either the Milky Way is at the center of an explosion of galaxies, or the universe is uniformly expanding (i.e. all galaxies are moving away from each other like points on the surface of a balloon as it is filled).
This was exciting news to advocates of a new theory of gravity called the general theory of relativity because the equations for that theory admit solutions for a contracting universe or an expanding universe, but not a static one. Within a few years, both the size and the shape of the universe had changed dramatically, and scientists were beginning to envision an early universe in which all the matter in the universe had started clumped together but was being pushed apart by internal nuclear forces, a notion that was to become known as the Big Bang theory.
In the years following Hubble’s discovery, theoretical physicists including Georges Lemaître and Alexander Friedmann provided rigorous mathematical descriptions of the Big Bang. However, the idea was still hotly debated. Some physicists, most notably Fred Hoyle, continued to argue for steady state models of the universe, which would eliminate the somewhat troubling notion that the universe must have had a beginning. Interestingly, Hoyle coined the term “Big Bang” while trying to discredit the theory.
Leftover Signals of the Big Bang
Pullquote: The Big Bang is the only hypothesis that can account for the observations astronomers are making today.
The debate raged on until 1964, when the astronomers Arno Penzias and Robert Wilson began using a radio telescope they had designed to study microwave emissions in space. Curiously enough, the device picked up a peculiar and quite regular static that seemed to emanate from every direction. Theorists quickly realized that the Big Bang theory predicted this omnidirectional signal.
If, as the Big Bang theory suggested, the universe had once been tiny but contained all the matter it does today, it would have been an exceedingly hot swarm of protons and electrons. Because of the heat, the electrons would not be able to form stable orbits around the protons. Instead, the protons and electrons would bounce around incredibly quickly, absorbing and emitting photons as they did so.
But as the universe expanded, the amount of energy per unit of volume would decrease, ultimately allowing electrons to settle around the protons to form hydrogen gas. Hydrogen can absorb only photons of very particular frequencies, and as a result, a great deal of radiation in the form of photons would have escaped from this dense cloud of hydrogen never to be reabsorbed again. Theoretically, this radiation would echo throughout the universe for the rest of time and would still be detectable today.
Sure enough, the signal detected by Penzias and Wilson corresponded to the theoretical temperature for the leftover radiation predicted by the Big Bang theory. The discovery of the cosmic microwave background radiation was a groundbreaking experimental verification for the Big Bang and physicists quickly began to abandon the steady state models and turned to the newer theory as a better explanation for the evolution of the universe.
The cosmic microwave background radiation, theoretically generated about 400,000 years after the start of the Big Bang, is the earliest view we will ever have of the universe, but it’s enough to tell us an awful lot about the conditions that caused the radiation.
There are surely still mysteries surrounding the origins of the universe. Dark matter and dark energy were discovered only recently and they are changing older notions about cosmology in general and the Big Bang in general. However, the fact of the Big Bang is not in question.
The structure of the universe — that is, the structure of galactic clusters, galaxies, stars, their relative motion, and the radiation echoing from the very end of the Big Bang — all insist on a universe that began as an incredibly dense, tiny ball and expanded to the size we see today. It is simply the only hypothesis that can account for the observations astronomers are making today.
Nothing new to me but I always enjoy reading stuff like this. Quite a solid, straightforward explanation too.
The ‘problem’ with physics is is that as our knowledge progresses, this stuff gets increasingly complex. At some point people just phase out and reach for easier, more convenient ideas, because embracing the notion of “I don’t know” or “I don’t understand” is scary to many.
One objection: Under the Big Bang model, the universe was never “tiny” or a “tiny ball.”
“Tiny” implies size measured relative to something else, but there is no “something else” against which the universe’s size can be measured. The density of the universe was extraordinarily (incomprehensibly) high at the time of the Big Bang, but that’s not nearly the same thing as “tiny.”
“The ‘problem’ with physics is is that as our knowledge progresses, this stuff gets increasingly complex. ”
I don’t know if complexity is the problem. We can simplify things a great deal with the right analogies. I think the problem is that it’s counter-intuitive. For example, people experience time as an absolute. We have to explain to people that time is relational, and therefore it simply stops in the pre-”big bang” moment. So talking about “before the big bang” is impossible, yet people’s intuition just can’t handle that. Based on our experiences, there has to be something “before”.
First off, interesting site and articles you have here. It immediately went onto my RSS reader :)
This sort of stuff is just fascinating on every level. To relate it to religion, as an atheist I can’t understand why one would decide that “God made it all this way”, rather than explore the endless mysteries of the universe and everything it contains. I’d rather spend my entire life searching for, and getting, answers, than waste my life hoping I’d get the answers “in the end”. We’re here now, in this infinite space, and we should make the best of the (relatively speaking) miniscule time we’re allowed to exist before the universe changes its mind about us.
And that Adams quote really is pure gold!
VorJack’s point that understanding Science most of the time is counter-intuitive is absolutely right.
In fact, all the work that has been done in Science is pointing the limitation of our intuition, using evidence to shape the theory and then subject the theory to unlimited tests.
I have started a series on “Science, Common Sense, Stupidity” at my blog [http://atheistbibleforum.blogspot.com/search/label/Science%20Common%20Sense%20Stupidity%20ScSS]. So far I have written only two. As time goes on, I will write more on how common sense may need us into trouble (sometimes deadly situation).
The inclusion of “stupidity” in the title of this series points squarely at a group of people who think who know everything and refuse to see reasoning from a logical and pragmatic angle. If you are one of those, you may excuse yourself from reading this series. It may offend.
“The ‘problem’ with physics is is that as our knowledge progresses, this stuff gets increasingly complex. ”
Even though I’ve been beaten to it I’ll add my couldn’t agree more with the above … the number of other galaxies and the time that the Universe has existed – well I don’t think our poor little brains are geared to really comprehend these type of numbers.
There are those who would argue that God made things look like this as a test of our faith. There are those who think, therefore, that their God is a bald-faced liar. I will not accept any hypothesis of God that is not consistent with the reality of the universe as we know it.
The universe is my Bible.
As a theist who has no problem with a “qualified” big bang theory, I wonder how you guys respond to those materialists who are critical of big bang theory. I’ve even seem them goes as far as calling it equivalent to creation science and saying that even Hubble didn’t believe in an expanding universe.
@Barry
I have no problem with valid criticisms of the Big Bang theory. But the science behind the criticisms must be valid. Being critical is one thing, but there is a heck of a lot of evidence pointing toward Big Bang. And any criticism that could actually call all of this evidence into question would have to be very comprehensive.
I am after truth, in whatever form it takes. I’m not married to theories, and science should not be, either. If incontrovertible evidence for God’s existence is demonstrated, then I would be very happy for it. I doubt that such evidence will ever be found whether God exists or not, however.
I am very open minded, but not so open minded that my brains fall out.
I am continuously astounded and amazed at what science can accomplish. That people have been able to figure stuff like this out gives me great hope for the future of humanity.
@VorJack: “I don’t know if complexity is the problem. We can simplify things a great deal with the right analogies.”
I agree to an extent, but some things just can’t be properly explained by any analogy. Quantum mechanics springs to mind. Not only is this counter-intuitive, as you correctly state is an issue with many aspects of how the universe really works, it is also mind-bogglingly complicated.
haha.. I feel like I’ve heard that somewhere. Maybe it was a bumper sticker.
@Barry
I agree with Yoda, I mean alphonsuspeck.
Plus, I don’t see how anyone could say that Hubble didn’t really believe in an expanding universe. Wasn’t finding redshift in everything far away what he is known for?
@Barry:
Like alphonsuspeck says, the criticism must be qualified. Saying things like “Hubble didn’t believe in an expanding universe” convinces me immediately that the person making the statement is a moron and/or a liar and I don’t need to consider any further statements from that person.
I think it’s fair to say that the Big Bang event is no longer disputed by any scientists. However, certain elements of the theory are hotly disputed, like whether inflation really occured. Also, speculations vary as to a cyclical universe, mulitple universes, etc.
These are valid criticism, but they are very far from the kind of criticism served by creationists, who are the main opponents of BB theory. (I’m surprised you mention materialists as opponents).
@Adamus
Is it because it’s counter-intuitive, and always will be, or just because it’s not something that we’ve grown up with and basically take as ‘second nature’? There most have been a time when it was counter-intuitive that the Earth was ‘hurtling’ through space yet we don’t just fly off of or even feels it’s movement.
Not something I have the answer to though …
The big bang is stuff “banging” together (very simplistic definition).
I’m a fan of this theory.
But the question remains,
WHERE DID THE BANGING PARTICLES COME FROM?
Please someone answer this.
I think he’s referring to the wrong astronomer. Hoyle didn’t believe in the Big Bang (http://en.wikipedia.org/wiki/Fred_Hoyle#Rejection_of_chemical_evolution), because it smacked of creationism. He had no scientific reason to throw it, he just wanted the universe to be unbounded in time so that there was no question of what “caused” the universe.
Of course, Hoyle was also a fanatical believer in panspermia, rejecting out of hand that life could have appeared on Earth without assistance, so he seems a little confused.
a) Another universe, in which our universe is embedded.
b) There was literally no cause.
c) Anansi the Spider God did it.
d) Quantum fluctuations created a bubble of spacetime which has zero net energy, and so doesn’t require any precursor energy.
Take your pick. Any or all of them might be right. But C is really, really unlikely.
@Jabster
Quantum theory is counter-intuitive often because some of it’s postulates dictate things for which we have no comparative model on the large scale.
Take Schrodinger’s cat, for example. The theory would dictate that, inside his little box, the cat would be both dead and alive at the same time as the quantum particle is in itself in an indeterminate state. The closest comparable analogy is people sitting in half alive states at their workplace desks, and this comparison really doesn’t do Schrodinger justice.
Another example is that a paired quantum particle will not determine it’s “state” until one of the particles is observed, and at which point the paired particle will immediately assume its state, even if many light years away. There is no reasonable or unreasonable way for us to explain this instantaneous communication; nothing in the real world acts remotely similar. It is information traveling faster than the speed of light. It is likely to remain forever counter-intuitive, as nothing in our macro world acts remotely like it.
Quantum Physics is f’ing weird, no matter how you look at it.
@wintermute
I’ve never heard of option D before and I think it is exceedingly clever. Any references to scientists who think that?
Also, as to the spider god thing. Maybe no human conception could define God. I choose to define God as the creative energy that spawned the universe. Whatever that is. Unless the net energy of the system is zero. Which is really, really, f$&king clever.
@alphonsuspeck, oh, Shrodinger’s Cat, my favorite quantum mechanics mindbend. The first time I saw this picture I had a fit of laughter lasting a good half hour. Nobody around me got it though…. I felt positively awkward.
http://www.adamus.nl/images/schrodingers-lolcat.jpg
@Adamus
:)
http://icanhascheezburger.files.wordpress.com/2008/07/funny-pictures-science-cat-does-experiments-on-you-for-revenge.jpg
@wintermute
No I meant Hubble, I’m not saying what is written here is correct or not, just that I’ve run across differing opinions on the Big Bang even within the camp of materialists………
) Hubble, in actual fact, was a life-long doubter of velocity being the cause of cosmological redshifts. And, (surprise) his linear law of redshifts applied to a non expanding universe. Here is one of many examples from his writings:
“Since the corresponding velocity of recession is the same fraction of the velocity of light, the nebulae in the most distant cluster observed, if they are actually receding, will appear 13 per cent fainter than they would appear if they were stationary. The difference is small but, fortunately, the measures can be made with fair accuracy. The results may be stated simply. If the nebulae are stationary, the law of red shifts is sensibly linear; red shifts are a constant multiple of distances. In other words, each unit of light path contributes the same amount of red shift. On the other hand, if the nebulae are receding, and the dimming factors are applied, the scale of distances is altered, and the law of red shifts is no longer linear.”
(See: Edwin Hubble, “The Problem of the Expanding Universe,” American Scientist, Vol. 30, No. 2, April 1942, pp. 110-1) For more see the Hubble link below.
http://home.pacbell.net/skeptica/edwinhubble.html
Chris:
I don’t have time to look up specific references right now, but it’s commonly accepted that all the gravity (negative energy) in the universe is at least very close to all the matter, light, electromagnetism and so forth (positive energy), so the net energy content of the universe is possibly exactly zero. If that’s the case, then it can be treated as a quantum fluctuation of the type we see when particle-antiparticle pairs spontaneously pop into existence, albeit on a larger scale.
I’ll try and get more detail for you when I have a few minutes to spare.
That’s a great description. I love reading that kind of stuff as do other commenters.
I also wholeheartedly agree with Martin that the science and theories surrounding this sort of thing make it infinitely more wonderful than the simple “goddidit” answer. Religion, to me, cheapens our whole existence by removing all the wonder and joy of scientific exploration.
Lee Smolin is a scientist with an interesting theory called the fecund universes theory. Has anyone heard of him or read his books?
It basically says that our universe was born from a black hole from another universe. in other words, our universe is an expanding blackhole from another universe that will eventually contract. If this were true, there would be unending number of multiple universes.
I have not read his books, but was hoping to get some feedback before I purchased any.
Here is a Summary of the Theory:
The fecund universes theory (also called cosmological natural selection theory) of cosmology advanced by Lee Smolin suggests that the rules of biology apply on the grandest scales, and is often referred to as “cosmological natural selection”. Smolin summarized the idea in a book aimed at a lay audience called The Life of the Cosmos (ISBN 0-19-510837-X).
The theory surmises that a collapsing black hole causes the emergence of a new universe on the “other side”, whose fundamental constant parameters (speed of light, Planck length and so forth) may differ slightly from those of the universe where the black hole collapsed. Each universe therefore gives rise to as many new universes as it has black holes. Thus the theory contains the evolutionary ideas of “reproduction” and “mutation” of universes, but has no direct analogue of natural selection. However, given any universe that can produce black holes that successfully spawn new universes, it is possible that some number of those universes will reach heat death with unsuccessful parameters. So, in a sense, fecundity cosmological natural selection is one where universes could die off before successfully reproducing, just as any biological being can die without having children.
@L. Cope
As it happens, Lee Smolin is also one of the leading critics of string theory. His book, “The Trouble with Physics” is the standard work cited against string theory. It has a website: http://www.thetroublewithphysics.com/
This was cool.
Nice little sum-up of the Big Bang, though interesting post at a time when New Scientist has just been postulating the growing weight behind Big Crunch theory (similar in all aspects except that the Universe originates from a similar Universe having reached elastic limit and crashing in on itself; an eternal loop of implosion/explosion/implosion etc.) and you yourself just having posted a very nice video on multiverse theory which personally I feel is the most logical.
My difficulty lies in both my ignorance and a desire for answers to the following questions:
if the micro world and the macro world work in fundamentally different ways, then how do they interact? (The answer to this would of course be part of the theory of everything.)
it’s a bit like the question: if we have a soul and a material body, how do they interact?
Also, if we choose to accept unboundedness (rather than infinity), then can we talk about meta-space or meta-time concerning the spacetime prior to the big bang (if there could be such a thing– perhaps like a multiverse)?
Can we then decide if infinite regress is no longer a problem (with time relative within the universe) or perhaps a bigger problem (with meta-time upon meta-time outside the universe)?
I love this stuff. It really makes me think!
As to what was BEFORE the Big Bang:
The problem with suppositions of the pre-universe are (at least) two-fold:
1) We don’t know if time is an inherent property of our universe or if it existed before it. In the former case, the question of what was before BB doesn’t make sense.
2) We don’t know if the pre-universe followed the same rules as our universe. Maybe the rules of cause and effect were different, making it possible for something (ie. our universe) to appear without prior cause.
Disregarding these caveats, I kind of like this idea of physicist Victor Stenger:
As a general principle, nature always moves towards the state which requires the lowest amount of energy to maintain (an equilibrium). We observe this all the time. In physics, this is observed as symmetry breaking, which means that the system transforms to a less symmetrical state. The four forces of nature (electromagnetism, gravity, strong and weak nuclear force) are actually one and the same at sufficiently high energies. A few moments after Big Bang, the total energy of the surroundings was low enough to allow a symmetry break, causing gravity to separate from the other three forces. Later, strong force separated. Later still, weak force and electromagnetism.
We also (sometimes, though not always) observe symmetry breaking at a less fundamental level, such as phase transitions from plasma to vapor to liquid to solid. The hypothetical supersymmetry is also a state of symmetry which has been broken. There are probably numerous other examples.
Anyway, Stenger asks: What is the ultimate symmetrical state? The answer is – nothing. The state of nothing is absolutely symmetrical, beyond any comparison. If we apply nature’s principle of seeking the least energetic equilibrium via symmetry breaking, we see that this state of nothing must break into a state of – something, as perfect symmetry requires a higher level of energy to maintain than imperfect symmetry. This “something” manifested in the Big Bang. Big Bang is a symmetry break from “nothing”. It happened beacuse nature constantly seeks a lower state of energy.
It’s an interesting hypothesis, but whether it actually holds up, I can’t say (and neither can Stenger). Is some initial energy implied? Did the rule of symmetry breaking have to come from somewhere? We don’t know. But I still find it a fascinating suggestion. It ALMOST makes sense.
I actually didn’t know Hubble was so indecisive in his interpretation of the meaning of red-shift. Never the less, seeing that multiple, independent branches of science later proved the expanding universe to be real, I still hold that anyone using Hubble’s doubt as “proof” against Big Bang is a dishonest moron.
It’s on par with stating “Darwin recanted his theory on his death bed” or “Einstein believed in God”. Disregarding the invalidity of these claims, personal conviction doesn’t come into the picture, as long as it doesn’t skew the science. A good example of this is Fred Hoyle, who was vehemently opposed to the Big Bang theory, right up to his death in 2001, but ironically he never the less laid much of the theoretical groundwork for the BB theory.
What interests me about the big bang theory is the binary approach theists take when they choose to dispute it. The big bang doesn’t disprove the existence of God, and if you ask where the super-dense beginning of the universe came from, and no answer is provided, that doesn’t prove the existence of God. Logic doesn’t work that way.
Science uses the word theory for a specific reason. Even if something is accepted as fact it is still open to to critical analysis and improvement. The big bang isn’t a way to say “Hah! God doesn’t exist, losers!” It’s simply the most commonly accepted reason for the evidence in front of our noses. God is not an acceptable reason because you can’t mix faith with science, otherwise science doesn’t work. If the vast majority of astrophysicists say that the big bang is really the only thing that would make sense according to the evidence they have – sure, I’ll go with it.
My point – this argument doesn’t really say anything about whether God exists. Theists can dredge up every single accepted scientific theory that doesn’t jive with the Bible and poke every one of them full of holes – it doesn’t win the argument. It simply points out a flaw that means either we don’t have enough evidence, our the conclusions need to be re-examined.
missed the name, not going back:
Compared to the modern universe and using a light year as a yardstick, the early universe was tiny. And most physicists seem to agree that it was very nearly round (though four dimensional — would “hyperball” work for you?). Obviously, I had to simplify things a little bit, as everyone here has pointed out that science is not particularly intuitive.
Jabster:
Feynman has an awesome quote about how we used to call them “astronomical numbers,” but now they’re even smaller than the national debt (and that was decades ago). “We should call them economic numbers!” or something similar.
Stephen Webb:
It’s an interesting question. In the very early big bang, we would not have seen protons, neutrons, or photons at all; interesting, since photons are responsible for all the interactions that (e.g.) keep us from falling through the floor, the ground, and down to the center of the earth, and protons and neutrons are pretty important in that whole gravity paradigm. Electrons are a little mysterious, and I don’t know very much about how they fit in with high-energy models. But the bigger stuff (protons and neutrons) seem to be assembled from gluons and quarks, and the very early universe would have been almost entirely a quark-gluon plasma (which I believe has been replicated in a particle accelerator at some point or other). Quarks are pretty much impossible to play with because we can only barely generate enough energy to start splitting them apart, and we can’t do too much experimenting before they stick back together.
So given how little we know about the material of which the early universe was made, I’ll have to give the default scientific answer: we just don’t know where the first particles came from.
Thanks everyone for your comments, these were very interesting.
It was me who made the “tiny” objection.
Don’t we need to make a distinction between the visible universe and the universe in its totality, thinking of inflation?
Certainly the radius of the visible universe was much smaller in the remote past than it is today. But we know the visible is not the total universe, which could be spatially infinite. And it seems that if the universe is spatially infinite now then it was always spatially infinite. In that case, the Big Bang doesn’t make reference to anything “tiny,” unless you’re thinking specifically about the visible universe. There are other possibilities, of course.
@Rodney Dunning
Sorry for losing your name. I have to admit to playing a little fast and loose with some details for the sake of clarity, and your objections are good for the sake of keeping everything in perspective.
Yes and no. On the one hand, there is some evidence for inflation, which would suggest that the distinction is important. On the other hand, the evidence is far from conclusive; from what I know, this is one of the biggest areas of debate about the Big Bang. And given that there’s no way to determine anything about the parts of the universe that aren’t visible, the distinction is only useful for qualifying current observations and theories with a big “BUT…”.
I think you have a little misconception here. I don’t think there are many (if any) professional physicists who think that space is infinite. The structure of space-time is dependent on energy density, and I believe the most widely held view is that space-time is a finite (!) four-dimensional spheroid that wraps itself around the (presumably finite) energy and matter that constitute the universe. In other words, if you pick a direction and keep going, you’ll end up where you started just like you would on the surface of the earth. When all the mass is in one spot, space-time is very highly curved and the round trip takes a much smaller amount of time — thus, tiny.
There are, as you say, other possibilities. I’m repeating what the professionals are saying to the best of my abilities.
Dan,
I am a professional.
The evidence for inflation is persuasive to everyone I know; I’m not aware of anyone advocating the “standard” (non-inflationary) Big Bang model. Perhaps some details are controversial, depending on how that term is defined.
On the structure of the universe, telescopic observations of the cosmic background radiation strongly suggest the shape is very nearly flat. I don’t know anyone who believes otherwise. The positive curvature you’ve described has been more or less put to bed by observations of light from the hot regions of the early universe. If the universe had positive curvature, those regions would appear brighter (due to focusing) than they do.
On whether the universe is infinite, we don’t know. A flat geometry is compatible with both a finite and an infinite universe. Detailed observations of the cosmic background radiation can, at least in principle, resolve this question. Unless something has come up very recently, I don’t think we know the answer.
@Rodney Dunning:
Well, I was about to consider myself informed because nothing you say sounds unreasonable, but then again, you are random internet dude. So I will read more about it before jumping to any conclusions either way. Thank you for the reality check, though.
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