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Infinite Universe

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Showing 51-75 of 289 posts in this discussion
In reply to an earlier post on May 10, 2012 8:02:25 PM PDT
D. Thomas says:
AP wrote: "(v1 + v2)/(1+ v1*v2) (I put c=1)"

Nicely put!

In reply to an earlier post on May 11, 2012 8:29:00 AM PDT
There have to be other science-literate sentient beings out there, arguing right now with other science-illiterate sentient beings, about dark matter, dark energy, evolution, AGW (alien global warming) etc.

Posted on May 11, 2012 8:43:06 AM PDT
Last edited by the author on May 11, 2012 8:43:27 AM PDT
Roeselare says:
This is clearly wrong-headed,

The existence of a physically real seven-year biological cycle in avian song and human basal heart-rate records was revealed by studies in the years 1959-68. In the interval in days between the dates of starting and finishing seasonal song (Feb to June) of the common Chaffinch for each of the years 1946 - 1968, the seven year cycle is clearly seen.. Such a cycle has also been recognized in folk-lore and primitive medicine from earliest times. This period has arisen as the result of a 'beat' interaction between two natural rhythms of slightly different periods. In particular, we consider the possibility that evolved organisms ( BUT NOT SPECIALLY CREATED ORGANISMS) have inherited a 'memory' of the orbital period of the Earth at the time that evolution from uni-cell types began; this most probably occurred 'way back 1150 million years ago. In all probability, it was the annual seasonal period that evoked a response from the primitive 'brain cells' of the evolving organisms, just as the annual seasonal period affects all living organisms today. If so, this period could beat with the current orbital period (our year) to produce the observed seven-year cycle. With these assumptions we can calculate the Earth's orbital period (P) in the distant past from the equation:

1 / 7 =(1 / P)- 1 / 1

where the unit of time is taken to be the current length of the year. This gives P = 0.875 years or about 10.5 months. We can calculate the corresponding mean distance (A) of the Earth from the Sun by using Kepler's third law, which takes the form A = P^2/3, when A is measured in astronomical units (au) and P is in years. We obtain A = 0.9147 au. If we take the time interval (T) over which evolution and the expansion have occurred as 800 million years, then the expansion coefficient (E) is given approximately by:

E =(1 - A)/ T = 1.11 x 10^-10 per year

This represents an extremely slow expansion rate of no more than 36.03 ft per year in a total distance of 1.5 x 10^11 metres.

If we assume that the changes in the Earth's orbital period and mean distance have occurred as result of the general expansion of the Universe, then E represents an estimate of the Hubble constant and we may compare it with the estimates obtained by measuring the speed of recession of distant galaxies and the density estimates per CMBR perturbation angular separations.

H is currently thought to have a value of 46 miles per sec per Mpc

transform from Mpc to au units, we find the equivalent Hubble expansion rate to be:

H = 36.53 ft per yr per au

This highly coincidental result suggests that an increase in the mean distance of the Earth from the Sun has occurred over the past years at the same rate as the cosmological Hubble expansion.

Of course, if this is so, it is in conflict with the current view that only the space between the galaxies which is expanding and not the galaxies themselves. The implication is that not only the space between the galaxies, but also all the space within each individual galaxy is expanding at a rate determined by the Hubble constant.

Posted on May 11, 2012 10:05:39 AM PDT
A. Caplan says:
Based on our present knowledge, it is believed that the universe is finite in size, although, like a circle, there may be dimensions that are infinite. Time is believed to have started at the Big Bang. However, time is a variable.

In reply to an earlier post on May 11, 2012 11:29:26 AM PDT
I thought the Wilkinson Anisotropy Probe indicated that the universe is flat and open, therefore infinite.

In reply to an earlier post on May 11, 2012 1:30:36 PM PDT
Last edited by the author on May 11, 2012 1:32:11 PM PDT
Jack Shandy says:
-"Given a finite number of positions within a given volume and an infinite collection of such volumes, there must be infinity many volumes that are identical. "

You cannot perfectly isolate the finite volumes. Wavefunctions will cross their boundaries. I think this is a crucial aspect you're overlooking. Also, it's not just particles on specific positions which define the structure. What about energy? The energy spectrum is infinite and partly continuous. Of the infinity of finite volumes, no two finite volumes need to contain the same amount of energy. So no two finite volumes need to have the exact same spacetime curvature either.

In reply to an earlier post on May 11, 2012 2:13:03 PM PDT
Doctor Who says:
isotropic and homogeneous implies matter and energy as they are both interchangeable and that the curvature is fairly uniform. There is no distinction between directions therefore no one place that stands out.

Since the volumes in question are several million light years across (we are essentially averaging galaxies), the wave function leakage is not worth much. Who cares about a cm compared to a light year?

In reply to an earlier post on May 11, 2012 2:24:42 PM PDT
Last edited by the author on May 11, 2012 3:17:51 PM PDT
Jack Shandy says:
Actually the argument in your link contradicts your assertion. They argue that space is NOT expanding within gravitationally bound systems. An expanding space solution (FRW) to the GR equations only matches observations on a large scale where the universe may be approximated to be homogeneous, and is NOT meant to describe space on smaller scales, like that of galaxies which are far from homogeneous.

I've been at this some years ago on this forum. I thought it kind of dubious to claim that spacetime is expanding everywhere while the internal gravity of gravitationally bound systems oppose this expansion. The expansion itself IS a gravitational phenomenon, is how I see it. So you have gravity opposing gravity? May certainly be true, but sounds far fetched and unnecessary to me.

Now, finding out if space actually is or isn't locally expanding within galaxies, seems to me to necessarily involve experiments with noninteracting dust. Well, good luck with that:)

-"Now there is an interesting argument about whether the atoms molecules, life forms, planets, stars, galaxies, etc. in expanding spacetime are expanding along with it or not. Some physicists argue they don't. "

Electromagnetically bound systems definitely don't. They have equilibrium distances which result purely from EM, not GR. If space (slowly) expands inside an atom, the EM forces will bring all separations back to their equilibrium distance. Only when the expansion occurs rapidly will the electrons be ripped away from the nucleus.

In reply to an earlier post on May 11, 2012 2:29:04 PM PDT
I read the link to say that although space is expanding everywhere, gravitationally bound systems are not expanding along with it.

Your point about the expansion of spacetime itself being a gravitational event is interesting. This would imply that spacetime wouldn't expand in the absence of energy and matter. I.e., a completely empty Universe wouldn't expand (or contract). Does that include dark energy?

In reply to an earlier post on May 11, 2012 3:13:43 PM PDT
Last edited by the author on May 11, 2012 3:18:56 PM PDT
Jack Shandy says:
-"Your point about the expansion of spacetime itself being a gravitational event is interesting."

Gravity is geometry, nothing else. If the geometry changes, isn't that by definition a gravitational process?

-"I.e., a completely empty Universe wouldn't expand (or contract)."

I don't know. Isn't an expanding Minkowski space an admissible solution to the homogeneous field equation? That would mean that expansion isn't necessarily tied to energy/momentum. Just like curvature isn't necessarily tied to energy/momentum: Schwarzschild spacetime as a mathematical solution to the GR equations is completely devoid of energy/momentum (any plausible physical process which results in such a region in our universe involves a collapsing mass, but this is irrelevant: the energy momentum tensor field in Schwarzschild spacetime is identically zero). Also, gravitational waves can exist in empty space, regardless of how they were generated.

Posted on May 11, 2012 3:22:20 PM PDT
Last edited by the author on May 11, 2012 3:50:49 PM PDT
Stormegeddon says:
In Science: Yes, the universe is infinite, since it is constantly expanding.

In Theory: No, the universe is not infinite. Since space is full of curves, as theorized by Albert Einstein, maybe space is just one big curve. Maybe traveling in a straight line inevitably leads into one big curve, until we eventually end where we started. The immense gravity in the center of the universe might have pulled itself into an invisible circle that cannot be escaped. It can't be escaped because of the immense gravity of the center of the universe, but this is all in theory.

I believe that the universe has an end. But the Universe is so immensely large, that humans simply cannot grasp this concept. Humans have a very limited perspective of infinity. So, what is infinity exactly? Does it just never end? Well, it has to begin somewhere...?? This is why humans won't ever truly understand infinity. Now, at the end of the universe I have absolutely no idea what exists. Maybe you just go back to the beginning of the universe?

In reply to an earlier post on May 11, 2012 3:41:51 PM PDT
Last edited by the author on May 11, 2012 3:42:18 PM PDT
tom kriske says:
--> No. Nothing can be infinite, as logically argued and proven by many philosophers throughout the ages, and the universe is demonstrated to be only finite by the absence of radiation with a wavelength of more than a certain amount (this amount being the size of the universe).

do you just make sh8 up to suit your immediate needs? from zeno to the present the infinite has served as a great source of wonder and confusion to all manner of thinkers, but it has never been proven to be a logical impossibility. and from a mathematical point of view, the infinite is way more than a mere convenience, it's a downright necessity.

In reply to an earlier post on May 11, 2012 3:42:13 PM PDT
Jack Shandy says:
Thought experiment:

Let's have one hydrogen atom in each multimillion lightyear volume, empty otherwise. The energy spectrum of the electron is countably infinite for the bound states, uncountably infinite for the free states.

Now, must there be two multimillion lightyear volumes in which the electron has the same energy? Or even have to exist in the same superposition of energy eigenfunctions? Didn't think so.

On macroscopic levels, you may well be right about patterns repeating, but when you regard the world quantum mechanically, I don't think so.

In reply to an earlier post on May 11, 2012 3:43:59 PM PDT
Last edited by the author on May 11, 2012 3:44:24 PM PDT
Stormegeddon says:
It was "In Theory". I personally like the idea of infinity.

In reply to an earlier post on May 11, 2012 3:45:38 PM PDT
Jack Shandy says:
For a second I thought you wrote that first paragraph. Haha! Really...

In reply to an earlier post on May 11, 2012 3:47:54 PM PDT
tom kriske says:
so long as it was only for a second!

In reply to an earlier post on May 11, 2012 3:53:54 PM PDT
D. Thomas says:
The future doesn't look good. The universe will keep expanding. Galaxies will become so distant from one another that their light will take so long to reach the beings of that time that they won't be visible. The sentient beings of that distant age will see only their own galaxy, and wrongly think that they're seeing the entire universe.

And the worst won't even have arrived yet.

Eventually, all the stars will burn out and the universe will reach entropy. All matter will evaporate. There will be no structure of any kind -- no sub-atomic particles, no planets, no stars, no galaxies. Nothing will remain, not even the random neutrino. Nothing will be happening, so time - nature's way of keeping everything from happening at once - won't even exist.

Dismal prospect, but there's good news: it's highly unlikely that any of us will witness this empty future.

It raises an interesting question, though. Will all that nothingness produce another Big Bang, and start the universe-building process all over again?

In reply to an earlier post on May 11, 2012 3:56:45 PM PDT
Stormegeddon says:
Big Bang 2 :)

In reply to an earlier post on May 11, 2012 4:00:59 PM PDT
reply to Physics Geek's post:

the butterfly does

In reply to an earlier post on May 11, 2012 4:01:39 PM PDT
D. Thomas says:

I didn't mean to suggest that we're the only part of the universe where there are sentient beings with such concerns.

My point was that only a very tiny fraction of the universe consists of matter, and that gravity and the Strong Force don't really matter except in the vicinity of matter.

In reply to an earlier post on May 11, 2012 4:01:46 PM PDT
tom kriske says:
well, in theory, i'd say the universe, in *all* its grandeur, is effectively infinite. and by that i mean that the entire edifice is so intricately interconnected, on time-spans measured in 10^10^1000 years and more, and spatial dimensions numbering, potentially in the billions and billions and billions... that you could never determine the 'true' nature of the universe. in fact, i think the question 'is the universe infinite?' is meaningless, or, at least, ill-posed.

In reply to an earlier post on May 11, 2012 4:01:56 PM PDT
reply to Jack Shandy's post:

grvity is the distortino of time

In reply to an earlier post on May 11, 2012 4:03:52 PM PDT
reply to tom kriske's post:

you have no idea what infinity really is if you think that

were you a liberal arts major ?

In reply to an earlier post on May 11, 2012 4:07:12 PM PDT
tom kriske says:
the fact that you don't have the slightest inkling of what i intimated in my post pleases me to no end.

In reply to an earlier post on May 11, 2012 4:12:34 PM PDT
Last edited by the author on May 11, 2012 4:12:54 PM PDT
reply to tom kriske's post:

i am glad taht your ignorance gives you pleasure

you still dont know what you are talking about though

i note you do not deny being a liberal arts major !!!!!!!!!!!!
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This discussion

Discussion in:  Science forum
Participants:  29
Total posts:  289
Initial post:  May 9, 2012
Latest post:  Jan 22, 2013

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