posted
I've been contemplating infinity lately and have realized just how mind boggling the subject really is. Let me try to sum up my thoughts regarding the matter, and let me know if it makes any sense whatsoever.
Let's begin with us. We are small. Incredibly small. Mind-boggling small, in comparison to the universe. Of course, the universe is, from our perspective, incredibly huge--but that is just from our perspective. Now let's shift that perspective a bit.
Let's shrink. Let's shrink to the point where the Earth is as relatively huge as that giant universe we were just worrying about. Naturally, by this point the Earth is seriously big, and the universe is even more so.
But we can shrink, and make that second point that big to us; and we can do that again, and again, and again.
But think: we haven't moved at all--we've just shrunk to a insanely tiny size compared to the universe, small enough that, to the common individual, we simply don't exist.
Naturally, it goes the other way, as well. We in our present perspective are next to nothing, compared to the entirety of the universe; what if the universe itself is next to nothing compared to something else, a fleck of dust in a world we have no comprehension of?
I've seen this idea stressed in fiction a couple of times, namely L'engle's A Wind in the Door and Stephen King's The Gunslinger. In the first, the main character shrinks to the size of a cellular protein, and finds that a human cell is like a world in comparison; in the second, the Gunslinger is shown the entire universe, and finds that it merely composes a single blade of grass.
Is there any merit to this idea of infinity whatsoever? The idea that perspective can go infinitely deep into the physical structure of the universe, until the universe itself loses meaning and the new perspective overwhelms us? Could our world be both infinitely huge and infinitely small? Or is this just a conundrum that I am worrying about needlessly?
Posts: 292 | Registered: Jun 2006
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posted
I'm not sure what type of answer you're looking for, but I think you answered your question already by realizing that size is relative. We can be both infinitely huge and infinitely small but not in relation to the same thing.
Posts: 1327 | Registered: Aug 2007
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quote:Originally posted by 777: Is there any merit to this idea of infinity whatsoever? The idea that perspective can go infinitely deep into the physical structure of the universe, until the universe itself loses meaning and the new perspective overwhelms us? Could our world be both infinitely huge and infinitely small? Or is this just a conundrum that I am worrying about needlessly?
This idea is explored in several Rudy Rucker novels and The Memory of Whiteness by Kim Robinson. However, the Planck length is one structural roadblock to an infinitely deep perspective of the Universe.
Posts: 6316 | Registered: Jun 2003
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I read up on the Planck length, but didn't quite understand it. Does it try to define a minimal length? I find that hard to believe; I mean, any length can be split into smaller lengths.
I suppose there is a minimal length that is of practical use to us, but that does not mean that infinity in this sense does not exist.
Another question: could this sense of an infinitely divisible universe mess with the atomic view of matter?
I would find it hilarious if scientists eventually discovered that our entire universe was merely an atomic particle.
Posts: 292 | Registered: Jun 2006
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posted
It's not a minimal length. You're right, mathematically any length can be be split into smaller parts. But that mathematical continuity may not be present physically. Assuming some theories of gravity are true, at distances approaching the Planck length, large-scale or human-scale topologies (roughly, the shape or structure of space) could break down, into quantum foam or other weirdness. See also wiki's page on Rolling ball--Scale-dependent_topology
So the smoothness or continuity of space we take for granted could be a scale-dependent illusion.
I only have a superficial understanding of this topic, if you want more you have to ask a physicist like King of Men.
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I have no mathematics or physics to back up anything I say, only Carl Sagan's relaying of the idea held by that some that our universe could just as easily be an electron of another universe as it could be its own entity, singular and absolute. I assume this is because we can't (so far?) have any outside examination of the universe and determine that "nope, not an electron in some colossal giant's toenail"
Posts: 655 | Registered: May 2005
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I have no mathematics or physics to back up anything I say, only Carl Sagan's relaying of the idea held by that some that our universe could just as easily be an electron of another universe as it could be its own entity, singular and absolute. I assume this is because we can't (so far?) have any outside examination of the universe and determine that "nope, not an electron in some colossal giant's toenail"
Mind boggling.... I'm content enough worrying about my homework, my family, and how I'll talk to "that pretty girl" so far though.
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And that's just the size of the known universe, relative to the size of the YouTube screen. I have no doubt that that fractal could continue for infinity.
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posted
So odd that this topic should show up the day after I finish reading "A brief History of Time" by Stephen Hawking.
My personal favorite theory of our universe is that we are inside of a rotating Black Hole... and even if we aren't, we likely will be someday! (like 10^80 years from now sure, but someday!) That is, unless all of the major particles deteriorate into neutrons and anti-electrons and things don't have enough mass to collapse themselves into a black hole and the existing black holes shrink down to near nothingness and explode leaving only energy and then the universe will go on expanding infinitely because their won't be enough gravitational force to slow it down and this is a huge run-on sentence and if you actually read it, I sympathize with you and you're still reading... stop now; did you stop yet?
Posts: 636 | Registered: Apr 2002
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I think that the current consensus is that the universe will just expand and cool untill everything is, like you said, broken down to elementary particles and chunks of matter floating around too far apart to interact.
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i thought there was a competing theory that said that the universe goes through regular cycles of contraction and expansion.
Posts: 3354 | Registered: May 2005
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steven, the expansion of the universe has been discovered to be accelerating, so all the big crunch and big rebound theories have fallen by the wayside. It's definitely expansion from here on out, from what we know now.
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No offense, Tatiana, but, last I heard, you're an engineer, not an astrophysicist. I saw an article in Discover a couple of years ago that said there are a number of theories besides infinite expansion still held by respected scientists.
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For not seeking offense, that was a little blunt, steven.
That being said, as far as I know there are still proponants of the constricting/expanding theory. We may just be victims of relative size, being too close to the bang to see the collapse.
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LOL steven, thanks for the vote of confidence. My other qualification is that I read science and astronomy journals all the time, and have a lifelong interest in astrophysics and cosmology. Definitely a lot more information has come to light since that Discover article of two years ago.
But, seriously, believe whatever makes you happy. No offense taken, I assure you. Posts: 6246 | Registered: Aug 2004
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posted
I'm puzzled why you think the acceleration of the expansion of the Universe proves anything regarding this. That fact has been known for decades. You haven't convinced me yet.
Posts: 3354 | Registered: May 2005
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quote:Originally posted by steven: I'm puzzled why you think the acceleration of the expansion of the Universe proves anything regarding this. That fact has been known for decades. You haven't convinced me yet.
steven, that fact has not been known for decades. Prior to the late 90s, it was thought that the rate of expansion was slowing down. More precise observations determined that the opposite was true, and led to the theoretical conception of dark energy (different from dark matter). These recent observations are presumably what Tatiana is talking about.
quote: The dark-energy story begins in 1998, when two independent teams of astronomers were searching for distant supernovae, hoping to measure the rate at which the expansion of the universe was slowing down. They were in for a shock: the observations showed that the expansion was speeding up. In fact, the universe started to accelerate long ago, some time in the last 10 billion years.
posted
OK, I'm not trying to be a big meanie, but the "red shift", which indicates accelerating expansion, had been commonly known of for at least 6 or 8 years before that article in Discovery came out. I kind of thought I'd known about the red shift since I was little. Maybe not, but I can't think of a time when I was aware of astrophyics that I didn't know about the red shift, and I'm 32, and read lots of science journals, etc. when I was 9 or 10 and after.
I still don't see what the red shift proves absolutely. Dark matter? Dark energy? Please. We barely understand those things at all yet, so to assume things like "they'll always have the effect of causing expansion to accelerate" is a bit premature.
Posts: 3354 | Registered: May 2005
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posted
In Penrose's "The Large, the Small and the Human Mind" there's a great chart showing a logarithmic scale of the universe in both time and physical size, from the big bang to now and from the Planck length to the "diameter" of the universe. Human beings are placed in the appropriate place on each scale.
It's not directly relevant to this discussion, but it's very good background
Posts: 26071 | Registered: Oct 2003
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posted
steven, the redshift of galaxies has been know about since the 1920s or even earlier. This led to the conception of galaxies, in fact. Before they were thought to be more local nebulae.
Hubble came up with Hubble's Law to explain these observations in 1929 paper, though his estimate of Hubble's constant was too high.
Hubble's Law is v = H_0 * D
where v is the recessional velocity, typically expressed in km/s. H0 is Hubble's constant and corresponds to the value of H (often termed the Hubble parameter which is a value that is time dependent)
Note the bold: Hubble's constant is actually a variable, that changes over time, reflecting either an accelerating or decelerating expansion of space.
This is what's new: a better estimate of Hubble's constant and it's rate of change over time. Now it's seen that the expansion of space is accelerating, so dark energy was theorized as an explanation. Before that, it was observed/assumed that gravity would slow the expansion rate.
edit: a summation from wiki:
quote:The value of Hubble parameter changes over time either increasing or decreasing depending on the sign of the so-called deceleration parameter q which is defined by:
In a universe with a deceleration parameter equal to zero, it follows that H = 1/t, where t is the time since the Big Bang. A non-zero, time-dependent value of q simply requires integration of the Friedmann equations backwards from the present time to the time when the comoving horizon size was zero.
It was long thought that q was positive, indicating that the expansion is slowing down due to gravitational attraction. This would imply an age of the universe less than 1/H (which is about 14,000 million years). For instance, a value for q of 1/2 (once favoured by most theorists) would give the age of the universe as 2/(3H). The discovery in 1998 that q is apparently negative means that the universe could actually be older than 1/H. In fact, estimates of the age of the universe are, by coincidence, very close to 1/H.
where v is the recessional velocity, typically expressed in km/s. H0 is Hubble's constant and corresponds to the value of H (often termed the Hubble parameter which is a value that is time dependent)
Note the bold: Hubble's constant is actually a variable, that changes over time, reflecting either an accelerating or decelerating expansion of space.
This is what's new: a better estimate of Hubble's constant and it's rate of change over time. Now it's seen that the expansion of space is accelerating, so dark energy was theorized as an explanation. Before that, it was observed/assumed that gravity would slow the expansion rate.
edit: a summation from wiki:
quote:The value of Hubble parameter changes over time either increasing or decreasing depending on the sign of the so-called deceleration parameter q which is defined by:
In a universe with a deceleration parameter equal to zero, it follows that H = 1/t, where t is the time since the Big Bang. A non-zero, time-dependent value of q simply requires integration of the Friedmann equations backwards from the present time to the time when the comoving horizon size was zero.
It was long thought that q was positive, indicating that the expansion is slowing down due to gravitational attraction. This would imply an age of the universe less than 1/H (which is about 14,000 million years). For instance, a value for q of 1/2 (once favoured by most theorists) would give the age of the universe as 2/(3H). The discovery in 1998 that q is apparently negative means that the universe could actually be older than 1/H. In fact, estimates of the age of the universe are, by coincidence, very close to 1/H.
quote:The idea that perspective can go infinitely deep into the physical structure of the universe, until the universe itself loses meaning and the new perspective overwhelms us? Could our world be both infinitely huge and infinitely small? Or is this just a conundrum that I am worrying about needlessly?
No one seems to have mentioned that long long before you hit the Planck length where the continuum hypothesis might no longer be valid for space itself, we hit dimensions where we are certaint that the continuum hypothesis no longer holds true for matter. The continuum hypothesis basically says that the properties of a material are independent of its size. So you can make things as big or as small as you might imaging and they will behave the same way. For example, a steel ball that's one millimeter across can have same properties as a steel ball that is a thousand kilometers across. But if you go the other direction and consider a steel ball that is a micron across, you drop below the grain size for the steel so the "steel" that is that small will behave entirely differently from a 1 millimeter steel ball. The interesting thing is that this break down occurs long before you reach the atomic scale because the macroscopic properties of most materials are the result of the interaction of many atoms. In the case of steel, the properties are the result of the interaction between crystal grains. In order for steel to behave like steel you have to have enough atoms to have enough crystals to allow the proper interaction of the crystals. So there is no way that the Whos on Horton's speck of dust sized planet could have steel. In fact, there is no way that they could be carbon based life forms with DNA and proteins and so on.
There is no physical way that you could shink a person to the size of a protein. And I don't simply mean that we haven't invented the technology yet. I mean that such a technology would violate the fundamental physical laws about the nature of matter. The basic properties of people (and all other life forms we know about) are determined by the interaction of many cells which are made of molecules like proteins and DNA. And the function of a protein or DNA molecule more or less depends on every single atom in the molecule. You can't cut it in half and end up with two halves that will behave anything like the orginal.
To shrink a person to the size of a protein would require a fundamental alteration in the nature of matter. You would have to shrink the atoms themselves creating for example, a form of matter with the same chemical properties as a carbon atom but which was millions of trillions of times smaller than a carbon atom.
And if we somehow discovered a form a matter that would allow us to have atoms millions of trillions of times smaller than the atoms in our universe, we would start running into other problems. For example, an eye that was smaller than about a micron, would never be able to see visable light because it would be smaller than the wavelength of the light. If you get even smaller, Quantum mechanics and the Heisenberg uncertainty principal dominate the behavior of particles. So Who mother's would have to content themselves with knowing either where the children were or what direction they were heading but never both. And who children would be restricted to a series of narrowly defind excited state.
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posted
Morbo, my understanding is that we don't yet have the computer processing power to determine much about dark matter or dark energy. Until we do, it's fruitless to speculate.
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posted
So, last I heard, it was undecided. Until the math is done, we're all making educated guesses. Right, Tatiana?
Posts: 3354 | Registered: May 2005
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posted
steven, nope. Read what Morbo said. The universe is accelerating in its rate of expansion. That means it's not slowing down, it's going to keep on expanding forever. No big crunch is anticipated ever, and no big rebounds. It's continual expansion from here on out.
The competing theories are about what exactly is causing the expansion, etc.
Posts: 6246 | Registered: Aug 2004
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posted
steven, I'm not sure why you're bringing processing power into this. In any case, it's not fruitless to speculate, this is 19/20 of the mass/energy of the universe we're talking about. If you look at the link, it says "0.4% stars etc." That's it--the entire observable universe is 0.4%. It's humbling.
With dark matter at least we have some guesses/suspects (MACHOs, WIMPs, heavy neutrinos). Dark energy, not so much. We need to speculate on what they both are in order to understand them.
777, you can click on this link--it's just a pie chart. Also, that equation in my summary from wiki is gibberish due to font changes.
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posted
Tatiana, there is no consensus in the field that expansion will continue forever. Check that Discover article, did you want a link?
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Thanks for the clarification, Rabbit. I didn't quite realize the extent of the problems with science that this idea could have.
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That one does not challenge accelerated expansion. Indeed, it accepts it and offers an alternate explanation. And although they postulate a cyclic universe, it is not a cycle of expansion and contraction but rather a cycle of collisions between membranes in a higher dimensional universe.
quote:This theorizing agrees with what we can see in our universe now. The ekpyrotic model leads to a scenario a lot like the fireball of the Big Bang, but there is no episode of inflation. From the outset, the cosmos experienced just one force that accelerated the expansion. That force is still at work today, which means that instead of coasting to a stop, the universe is expanding faster today than it was a billion years ago and will be expanding faster a billion years from now. In short, that one force would also explain the enigmatic force that astronomers have recently named dark energy. Further calculations by Steinhardt and Turok suggest we're at the beginning of a very long process that will eventually result in what appears to be an empty universe. Trillions of years from now, matter will be so widely spread out that its average density will be much less than a single electron per quadrillion cubic light-years of space. That's so close to zero density that there's no meaningful difference.
Again, this scenario echoes the predictions of conventional Big Bang cosmology, except that in the model proposed by Steinhardt and Turok, the story does not end there. In the far future, another three-dimensional world still lurks nearby, similarly emptied out after its encounter with ours, invisible and imperceptible to us. Although they bounced apart after the collision, the two branes will exert a force on each other that's analogous to gravity, and they will ultimately meet in another crash, triggering another Big Bang. The cycle of such collisions would be eternal.
posted
I'll admit up front that I didn't read anything into that Dark Energy thing, so everything I'm about to say might be completely pointless.
I don't see why the Universe would keep expanding after all of the major energy-producing particles have eroded. I mean, sure, there wouldn't be any Gravity to pull the edges of the Universe back, but neither would there be any force to push it OUT. Perhaps it will just stop altogether?
Of course, this whole thing is sort of abstract to me, as we don't even know what the "Edge" of the universe IS. To know how it would act, one would have to know the difference between it and the void OUTSIDE of the universe, wouldn't you? Is the "Universe" just defined as the parts of "Space" that contain energy/matter? Maybe the edge of the universe is to space as a national border is to Earth. An invisible, imaginary line of which their is no real difference between one side and the other except for what you find their.
Of course, that concept would imply an Infinite Universe in which exists at least one "Island" created by an exploding Singularity (Big Bang), and I know how much Physicists are trying to do away with infinites, but how else can something "Expand" when it's the only thing that exists?
Posts: 636 | Registered: Apr 2002
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posted
I'm afraid you will have to get into dark energy if you want to deal with this issue. Steinhardt and Turok offer one possible explanation. A more common explanation comes from the applying the Heisenberg uncertainty principle. If the principle holds, there is no such thing as empty space: new particles pop into existence and are promptly destroyed by their anti-particles creating what is called vacuum energy.
The 'edge' of the universe might not be a useful concept at all and, regardless, an edge is not necessary to show that the space between clumps of matter is expanding.
Posts: 675 | Registered: Aug 2001
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posted
Paul Davies flips that around in his latest book Cosmic Jackpot where he argues that our observations help create the goldilocks universe in the first place.
I can't put my hands on a good text reference right now (other than Amazon) but he talks about it for this week's Science Friday "Why the Universe is Right for Life":
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