The Expanding Universe?

[Astrophe (John)]

Hi All

I'm a newbie, so please be patient.

A few friends and I were discussing the concept of the ever expanding universe. We were somewhat perplexed about the nature of an ever expanding universe. What is causing the expansion? Is it the force of the Big Bang, or is something else (some other force) driving it.

I made the point that, if the universe was indeed expanding, then, by definition, it wasn't actually expanding into anything, as that would imply that there was something other than the universe into which it was expanding (hope you're getting this). My point was that as the universe expanded, then it was creating void, but that it couldn't be expanding into a void. A void is something....well the lack of something....which amounts to the same thing. So the universe is expanding, but not expanding into anything.

Am I on the right track, or not? Sorry to land this curly one on you all as my first post, but it's an intriguing question.

Thanks.....John.

[billdan (Bill)]

Gooday John,

Welcome to Ice in Space, hope you visit us more often, lot of friendly and intelligent people here, who are very helpful.

As for your question, I am definitely no expert on this subject but I believe the current theory/hypothesis is this thing called Dark Energy that is driving the Universe expansion. As for it filling in an empty void, I don't think that's correct, the empty space itself is expanding (at the speed of light) and dragging the physical stuff along with it.

To wet your appetite here is a link from our ABC that can make your brain hurt. But use google to hone in what else you need to know.

http://www.abc.net.au/news/2016-01-2...iverse/6994612

Cheers
Bill

[Astrophe (John)]

Originally Posted by billdan

Gooday John,

Welcome to Ice in Space, hope you visit us more often, lot of friendly and intelligent people here, who are very helpful.

As for your question, I am definitely no expert on this subject but I believe the current theory/hypothesis is this thing called Dark Energy that is driving the Universe expansion. As for it filling in an empty void, I don't think that's correct, the empty space itself is expanding (at the speed of light) and dragging the physical stuff along with it.

To wet your appetite here is a link from our ABC that can make your brain hurt. But use google to hone in what else you need to know.

http://www.abc.net.au/news/2016-01-2...iverse/6994612

Cheers
Bill

Hi Bill

That was the point I was attempting to make, i.e. that the universe is not expanding into a void, but that it is creating void as it expands, so I think we're both on the same track.

Thanks for the link....lots to think about, there.

[Astrophe (John)]

http://www.abc.net.au/news/2016-01-2...iverse/6994612

"Only 5 per cent of the universe is made of ordinary material like planets, stars, cars, and coffee. This "normal matter" is made mostly of protons, neutrons, and electrons.
Another 24 per cent is an exotic material that interacts through gravity, but produces no light, making it invisible to us. We call this "dark matter".
While dark matter only interacts with normal matter very weakly, particle physicists have plausible candidates for what dark matter is."

This is quite astounding. Only 5% of the universe is accessible to our senses. Would I be correct in assuming that scientists have postulated the existence of substances/forces called dark matter and dark energy? Neat. I'm guessing that science has arrived at these conclusions because the universe needs to have more 'substance' to account for its present (observable) behaviour?

[billdan (Bill)]

*** I'm guessing that science has arrived at these conclusions because the universe needs to have more 'substance' to account for its present (observable) behaviour? ***

Spot on John, scientists observe behaviour that doesn't match up with the maths.

We know that the outer planets orbit the Sun much slower than the inner planets due to the Suns gravity.
Back in the 1930's scientists assumed that the stars rotating around a galaxy would do the same thing.

What they discovered was that both outer and inner stars were rotating at the same speed, like a record on a turntable. When they did the maths, to work out the mass of the galaxy to produce that fast orbital speed of the outer stars, it came to 400 times more than the calculated mass of the visible galaxy. They called this invisible mass dark matter.
This 400:1 ratio has since been reduced to 5:1 due to better instruments calculating the visible galaxy mass.

Not all scientists believe in this theory, some say they have underestimated the influence caused by the mass of central supermassive black hole in each galaxy.

Other scientists say this extra mass is hidden in another dimension thats why its invisible, this is when science starts to turn into science fiction I think.

Anyway its all above my level of understanding.

Cheers
Bill

[Cimitar (Evan)]

Hi John, welcome to the forums

Your initial post is correct - our current understanding is that the Universe is not actually expanding into anything. As you mentioned, it is essentially creating the space/void as it goes. I often hear the analogy: take a deflated balloon, draw 3 dots on it, and then inflate the balloon. All of the dots will appear to move away from each other (relative to one another). Thus there is no apparent centre to the Universe as all remote galaxies appear to be moving away from your point of reference.

In addition to this, the universe appears to be accelerating in it's expansion, and began doing so approx. 7 billions years ago.

RE: Dark matter - yes, it was initially detected via galaxy rotation models. There also appears to be mounting evidence for it in the distribution of material on the large scale structure, via gravitational lensing and through fluctuations in the CMB.

Cheers, Evan

[Astrophe (John)]

Thanks Bill and Evan for your responses.

I guess I've always had a passing interest in Astronomy for most of my life, but other things always seemed to get in my way when it came to allocating time for further study. As a newbie here, I'm on a very steep learning curve and I won't be able to contribute much to debate, until my knowledge base has grown considerably. What I perhaps can contribute, is a somewhat fresh approach to the subject, as I come to it with no preconceived ideas or entrenched prejudices.

In the near future, I hope to move to a non-urban location, which might enable me to begin to explore the heavens for myself, with the aid of a telescope. At present, I live in a very light-polluted environment (Wollongong), so I guess it would be fairly pointless to begin such a venture, now.

Cheers for now......John.

[sharptrack2 (Kevin)]

Hi John,

Welcome to IIS!

Don't think you can't experience some wonders of the immediate universe just because you're in the city.

A pair of binoculars (8x50 seems to be the recommendation) will allow you to explore the solar system, star clusters, nebulae. You can learn your way around the sky and prepare yourself for when you manage to find those moments under a dark sky and can look up.

A 6" dobsonian will also cut through a lot of that pollution and allow you to see the planets, the Trifid, Lagoon, and Orion nebulae.

One of the primary things to do is to find a spot in the yard that doesn't have a street light visible, if that's possible. Once you get dark adapted, things will start to pop out at you.

No time like the present to take a look at those receding galaxies!

[StuTodd]

Originally Posted by Cimitar

I often hear the analogy: take a deflated balloon, draw 3 dots on it, and then inflate the balloon. All of the dots will appear to move away from each other (relative to one another). Thus there is no apparent centre to the Universe as all remote galaxies appear to be moving away from your point of reference.

Cheers, Evan

So no matter what your wife tells you, you ARE at the centre of the universe

I have always wondered if we rely upon early physicists calculations too much. We certainly are seeing things which our physics and maths find awkward to fit into.

We were killing people for saying the sun was central in the solar system not too long ago in history! We believed the Earth is flat too. Who is to say the speed of light can't be beaten...if new theory explains more than the old equations, run with it!

Stu

[Astrophe (John)]

Originally Posted by StuTodd

So no matter what your wife tells you, you ARE at the centre of the universe

I have always wondered if we rely upon early physicists calculations too much. We certainly are seeing things which our physics and maths find awkward to fit into.

We were killing people for saying the sun was central in the solar system not too long ago in history! We believed the Earth is flat too. Who is to say the speed of light can't be beaten...if new theory explains more than the old equations, run with it!

Stu

I think the ancients knew a thing or two about the universe. After all, the Greeks came up with the idea of the atom and the more enlightened ones knew that the earth (and the other planets) were spheres....hence the 'music of the spheres' and the concept that the heavenly bodies made 'music' as they moved through space. The heliocentric system we acknowledge today, was also a Greek 'invention'.

[silv (Annette)]

I have the problem with imagining expansion, too, because my 3 dimensional experience tells me there has to be a direction, a room into which expansion goes.

One day I thought "Hey! It's time that is expanding, not the matter that makes up the universe. "

And beyond the edge of time, there can not be anything - because it has to happen before it can be something.

This somehow settled my feeling uncomfortable with space expanding.
It doesn't expand into a "there" but rather into a "then", which enables the space to expand, too.

Which still leaves me with thought-vertigo when it comes to the big bang, the beginning of time.
A link is missing, another level is missing to get a feeling of what was "before" time popped into being.

That "before", of course, is my limitation of experience as a human being.
Logically, there can not be a "before" if time did not exist yet.

Hence my thought-vertigo.

Time and space did not exist - so maybe a new word is needed for that circumstance.
Something like "befar", maybe.

[silv (Annette)]

Oh,
a new link in my thought chain:

The "befar" is of course still with us.
It didn't disappear when time was born which in turn enabled space to become space.

Where is "befar"?

[Astrophe (John)]

Originally Posted by silv

Oh,
a new link in my thought chain:

The "befar" is of course still with us.
It didn't disappear when time was born which in turn enabled space to become space.

Where is "befar"?

It befar away.

[markbakovic]

Originally Posted by Astrophe

I think the ancients knew a thing or two about the universe. After all, the Greeks came up with the idea of the atom and the more enlightened ones knew that the earth (and the other planets) were spheres....hence the 'music of the spheres' and the concept that the heavenly bodies made 'music' as they moved through space. The heliocentric system we acknowledge today, was also a Greek 'invention'.

I think the ancient greek concept of atomos was substantially different to what "we" (or even 19th century physicists) would consider an "atom", and related more to the logical extrapolation that if you halve a thing and halve the half and repeat ad nauseum eventually the last "half" must be smaller than the width of your blade and, thus, indivisible (which is all that word is usually translated to mean). The reintroduction of that term as appropriate for the modern idea of an atom makes sense conceptually (although what the Greeks meant would be more similar to what we'd call a "molecule" today), but only to a certain level of basic chemistry. Any concept of electron orbitals, binding energies or subatomic particles would be completely unrelated to what was just a Greek thought experiment in mathematics (an illuminating one sure).

Aristarchus' system of motion of the wandering stars (it's generally assumed the ancient Greeks had no idea they were lumps of rock like the earth and the moon, as the usual thinking is it is not possible to discern the phases of Venus with the unaided eye) was indeed heliocentric, but he wasn't influential at the time (and a lot of his work was lost anyway) and his model was actually a worse predictor of planetary motion than various iterations of Ptolemy's geocentric models of 300 years later, which used very un-physical orbits within orbits to explain (albeit not very badly) most of the observations readily available to anyone with eyes and a calendar. Both their errors were simple: the classical mathematician's unhealthy obsession with circles. 10 points to Griffindor for guessing that stars are spheres based on the same obsession, though, so it wasn't all bad.

The problem with vague mysticism (eg "all the planets hum a melody") is that if you try hard enough you can make any specific, verifiable fact seem like it was predicted by some appropriately indistinct sage wisdom of the ancients if you try hard enough ("oh, Pythagoras knew that planetary bodies reradiate absorbed solar radiation in the infrared and their orbits lead them to approach us and recede with a particular frequency and the Doppler variation in their IR signal is the "melody" to which he was referring...").

Also if 5% (seems low) of teh univers is "normal matter" that doesn't mean only that is accessible to our senses: a) black holes, unstable particles (like all those neutrinos, muons, Higgs and un-Higgs bosons etc. etc. flying around in ATLAS detectors and things), photons, force fields (like gravity) are all accessible to our senses (directly or via monitors), and b) I would argue that we can "access" dark matter and dark energy (since we can observe their effects) and saying we can't experience DM because we can't see it is a bit like saying I have no concept of "blue" because I can't taste it, or that I can't smell Smells Like Teen Spirit, therefore grunge was just an accident of mathematics.

I think that far from demystifying science the urge to amaze and impress often risks shrouding things like this in more mystique than is healthy. People complain about science being treated like a lobby group and a point of view and "only 5% of the universe is normal things" or "the LHC can make black holes" doesn't exactly do a lot to dispel the myth of crazy albert with zany hair and some far-out conclusion based on a blackboard full of heiroglyphics That Will Blow Your MIND! etc.

There seems to be some non- or dimly- glowing material concentrated near the galactic core. It might be a new type of dust. It's quite far away but, so it's hard to tell.

Gravity seems to be weaker over huge scales than we expected, so there may be some energy excess to what we usually predict. We'll let you know.

It might rain tomorrow. Maybe even this afternoon. Should be sunny again by the weekend.

btw:

and also: Cimitar, the universe expanding at an increasing rate beginning 7 bn years ago, where is that from? news to me...

[Astrophe (John)]

Markbakovic, Thank you for your extensive response, but there is no need to be so defensive, as I was speaking in the 'round' not in the specific. Much of the learning and knowledge of the ancient Greeks, Egyptians, etc, has been lost, so it is not at all fair to allude to them (as you appear to), as being mere 'thought spinners'.

I'll just go to one point for the moment. The Music of the Spheres, was a concept based on the assumption that all matter is made up of vibrations....that there is no real solid matter at all, but that everything is at base.....music...or sound....vibrations. This conclusion is not as foolish as it might seem at first glance, because, as we know, atoms are made up of vibrating particles and while the ancients obviously had no first hand knowledge of the existence of protons and neutrons, etc, they appear to have had access to knowledge which hinted at the existence of infinitely small particles and that the world of the senses, was, by and large, composed of ever finer grades of matter and that these particles made 'music' as they went about their business. It is a somewhat poetical way of expressing things, but nonetheless, apposite.

[RelevantTheory]

The quetsion is really semantics about what is or not is a thing. After all if there is no information, no differentiation to something else, does it really exist or does it require something to be compared to. Similarly it is an argument of semantics as to wether the night sky is dark. It can only be compared to something else, such as the sky in the day. Information that does not represent anything known is egocentrically denied being in a state of existence but still must exist at the same time due to its denial. What is beyond our comprehension will be denied its existence but must exist by virtue of being beyond our comprehension. After all that is a differentiation itself. Anyway, simply put, the way I sense it is that where we perceive the threshold of existence must always progress because at that boundary is an ineffable difference which is existence itself. We may just need to accept laws of physics or scales of difference which are beyond those we are so far familiar with.

[Astrophe (John)]

....I think!