Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: DoctorBeaver on 17/05/2005 00:28:12
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I've just read a reply to an earlier post of mine & someone mentioned relativity & non-moving objects. Now, being but a humble psychologist, not a physicist, I need some clarity on a few points here.
1) If space is expanding, can any object be at rest in the universe? If the space between A and B expands, does that mean that A and B must be moving or can they be stationary while just the space between them expands? Surely, if the space expands they must get further apart: but are they actually MOVING? And if they ARE moving, what are they moving relative to?
2) It's accepted that galaxies, clusters & superclusters are moving away from each other (with local exceptions due to gravity, of course, e.g. the Milky Way & the Andromeda Galaxy): but further to my 1st point, are they actually moving apart or would thay be stationary if space itself were not expanding? Do they themselves have velocity other than that of the expansion?
3) Does the expansion of space occur WITHIN objects? Red giant stars are huge & there is 1 hell of alot of distance between 1 side & the other. Does the expansion of space cause them to also expand or does their gravity counteract it? Or how about the stars in galaxies? If space is expanding, is it just gravity that stops them from moving away from each other? I assume that's the case: but, am I missing some fundamental point, or isn't it quite a coincidence that the gravitational attraction within a galaxy exactly counteracts universal expansion? Similarly with atoms. Is the space between the particles expanding? And, if so, isn't it weird that the forces within the atom exactly balance that expansion?
Am I being stupid? Have I had too many tequilas?
AAARRRRGH... my brain hurts!
It wasn't me - a big boy did it & ran away
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1. No object is at rest in the universe, unless it be your very own local easy chair, and you would like the universe to be moving about you. It's all relative. We have trouble talking sense about what we mean by space. Is it a thing with its own properties, or can it only have sense when measured between two masses. This is a question that physicists don't seem to be able to answer with one voice. One thing is clear. On a cosmological scale, all things move relative to each other; there is nothing else to measure them against.
2. They are moving apart. We can measure that. We cannot actually measure the space between galaxies, just the galaxies. I think galaxies would not be moving away from us if the universe were not expanding. However, they would not be stationary then, they would be falling towards us. A stationary universe is simply not stable.
3. This is a question at the forefront of cosmology. Some conjecture that dark energy will eventually rip everything apart, even atoms. Others don't agree. As far a weird coincidences go, the universe is full of them. There are numerous strange "tweaks" of parameters in fundamental particles and forces, the mass and size of the universe, and in nature all around us. If any one of them were not true, we would not be here. So why is it all like it is then? This is really the most fundamental question. Stay tuned.
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1. Is not the creation of virtual particles a fundamental of space? Couldn't that be used in some way to "measure" space itself?
2. Isn't there something called the Great Attractor towards which superclusters of galaxies are moving? So, could the movement of galaxies be due at least in part to some kind of gravitational force emanating from that rather than solely the expansion of the universe? I seem to remember reading somewhere that the Great Attractor was theorised to be a massive cosmic string brane. If that is the case then the gravity from it must be unimaginably intense.
3. I suppose you're right about the forces exactly balancing being 1 of the coincidental constants. I realise that if any of them was different we, and, indeed, the universe itself, wouldn't be here.
However, having said that, is the speed of light an exception? If C was, say, 1% slower than it actually is, would that affect the basic structure of the universe? I believe all the other universal constants are concerned with force - gravity, electroweak etc - but light is different: it is not a force per se. Is possible to postulate a universe where all the other constants had the values they have here but where C was different? Or does light being a form of electromagnetic radiation mean that there is some direct correlation between C and the electroweak force?
It wasn't me - a big boy did it & ran away
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1. Virtual particles cannot be detected unless they become real. Space itself can be "measured" using virtual particles on a microscopic scale. There is a QM experiment showing the force that the vacuum energy exerts on closely spaced sheets of foil. I don't remember the name of this effect, and how large this force is. However, on cosmological scales there is no such thing to allow us to measure distances. Many astronomers have wished there were, since measuring astronomical distances has consumed many an astronomer's career. We had no idea how far away the nearest stars were until the last half of the 19th century.
2. I remember such terminology, but I can't say what would be in the "great attractor".
3. I am reminded of the fine structure constant, alpha. It is a pivotal, dimensionless constant which has exxtremely important ramifications for all matter and radiation. It is a function of the electronic charge, Planck's constant, and the speed of light. Yes, everything would change if c changed by 1%. Google "fine structure constant" for lots of reading. here is one reference:
http://scienceworld.wolfram.com/physics/FineStructureConstant.html
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Great questions, great answers, Great Britain(where I live), Great Balls of Fire !!..well, that's how this planet's going to end up eh ?...........oh great !!
Oh, and regarding the Great Attractor...well that's me !!..Great Charisma [;)]...ok Nursey..I'm ready for my bed bath now !!
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Finstagiber.net%2Fsmiliesdotcom%2Fcontrib%2Ficw%2F003.gif&hash=f326f525e3f6c60d4ea3ecbb24d1df2a)Men are the same as women.... just inside out !!(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Finstagiber.net%2Fsmiliesdotcom%2Fcontrib%2Ficw%2F003.gif&hash=f326f525e3f6c60d4ea3ecbb24d1df2a)
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quote:
Originally posted by gsmollin
There is a QM experiment showing the force that the vacuum energy exerts on closely spaced sheets of foil. I don't remember the name of this effect, and how large this force is.
The Casimir effect. Another crazy cloggy. [:)]
http://physicsweb.org/articles/world/15/9/6
The living are the dead on holiday. -- Maurice de Maeterlinck (1862-1949)
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Indeed - Hendrik Casimir (1948)
It wasn't me - a big boy did it & ran away
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If you want to read a good read, pick up his autobio called 'Haphazard Reality'. Very nice, funny guy too.
here's a review of sorts:
pdf:
http://www.aps-pub.com/proceedings/1463/304.pdf
The living are the dead on holiday. -- Maurice de Maeterlinck (1862-1949)
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Is Casimir still alive? If so, would you happen to know what he's working on now?
It wasn't me - a big boy did it & ran away
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No, he died in 2000. Funny how Dutch physicists excel at fiddling with tiny forces - van der Waals, Lorentz, Kamerlingh Onnes, Casimir. Most Dutch could care less, tho. Forgotten heroes, alas.
There's one bit from his memoirs I will not keep from you, on a similar 'nationalistic' note: Einstein was pretty obsessed with his Jewishness - understandably so, under the circumstances, you would say, and ofcourse this is true, although he probably was quite conscious of it way earlier in his life. Then again, cultural identity runs strong in just about any group, doesn't it?
Anyway, Casimir once walked into a room where Albert was standing close to a painting of Lorentz, for whom he had an boundless respect, whispering: "He must be one of us. I'm certain of it. Must be.' or words to that ilk.
Well, from his picture you cannot say, he's a pretty swarthy looking Dutchman, allright, but as far as I can find info on him, sorry for Albert, he wasn't.
http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Lorentz.html
Ach, you cannot win zem all, Albert probably would have said.
The living are the dead on holiday. -- Maurice de Maeterlinck (1862-1949)
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Heh, nice anecdote
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quote:
Originally posted by chimera
No, he died in 2000. Funny how Dutch physicists excel at fiddling with tiny forces - van der Waals, Lorentz, Kamerlingh Onnes, Casimir. Most Dutch could care less, tho. Forgotten heroes, alas....
Hey chimera, I just noticed your profile says "Netherlands", so you're Dutch, no? You lucky dog, all the prettiest girls are Dutch.
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quote:
Originally posted by gsmollin
[quote
Hey chimera, I just noticed your profile says "Netherlands", so you're Dutch, no? You lucky dog, all the prettiest girls are Dutch.
Is there any empiric evidence for this? [:p]
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He's not the first to make that statement, at least, so I suppose there's probably some truth to it. They're maybe a bit taller than in quite a few other countries, and legs that go on for miles and miles are pretty convincing arguments on that front, I guess... quite a few Dutch supermodels around.
Must say I personally would go to Belgium for a good drool. Cutest faces on the planet.
Don't drink beer anymore, but when I did, that was Belgian too, come to think of it - best in the world. So thats women, booze, but for some reason no really good Belgian music comes to mind to complete the old adagium.
Ach well.
The living are the dead on holiday. -- Maurice de Maeterlinck (1862-1949)
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You didn't mention Belgian chocolate
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Oh, cruel. Forgot all about that, and me a choc junk to the max.
Dig this: the discoverers of chocolate, the Mayas forbade women to drink chocolate (it was a drink to them) because it would turn them into sex-crazed monsters.
And guess what: it's LEGAL in Belgium.
The living are the dead on holiday. -- Maurice de Maeterlinck (1862-1949)
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Yeah, I seem to remember hearing about that somewhere. Why the hell would they stop them drinkning it? I'd have thought it would have been mandatory!
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Womandatory, even.
The living are the dead on holiday. -- Maurice de Maeterlinck (1862-1949)
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Ohhh grrroooooaaaaan [V]
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Hey, I'm Dutch. I can pretend I never heard of off-colour jokes, right?
The living are the dead on holiday. -- Maurice de Maeterlinck (1862-1949)
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quote:
Originally posted by DoctorBeaver
quote:
Originally posted by gsmollin
[quote
Hey chimera, I just noticed your profile says "Netherlands", so you're Dutch, no? You lucky dog, all the prettiest girls are Dutch.
Is there any empiric evidence for this? [:p]
It's a long story, but I suppose its only my own personal bias. Belgian girls have prettier faces? Hmm, I'll have to look into that. Was that a pun?
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You're a regular Munster Punster.
I suggest looking into their faces starting all the way at the feet and work your way up from there. Take all day, and have lunch half-way.
OT: In particular the seemingly innocent question of the Casimir force within a single hollow sphere is still a matter of lively debate. People are not even sure if the force is attractive or repulsive.
I've a feeling it depends on the direction (inward/outward), and that this somehow ties in to both gravity and vacuum expansion.
The living are the dead on holiday. -- Maurice de Maeterlinck (1862-1949)
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quote:
Originally posted by chimera
...I suggest looking into their faces starting all the way at the feet and work your way up from there. Take all day, and have lunch half-way.
OT: In particular the seemingly innocent question of the Casimir force within a single hollow sphere is still a matter of lively debate. People are not even sure if the force is attractive or repulsive...
I have been "looking into" this issue, especially during lunch. I have determined that the "force is attractive"! I have also determined that it is a fundamental "force", very primal. I hope this helps.
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This thread has really nose-dived [:(]
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Well, it's movement. [:)]
The living are the dead on holiday. -- Maurice de Maeterlinck (1862-1949)
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quote:
Well, it's movement.
So is having a dump! [:p]
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OK, then print this and read at your next session:
http://physicsweb.org/articles/world/13/12/8/1
I think it will clear up some of your questions and undoubtedly spark a few new ones...
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From that link - Planck regarded the energy "as made up of a completely determinate number of finite equal parts, and for this purpose I use the constant of nature h = 6.55 x 10-27 (erg sec)". Moreover, he continued, "this constant, once multiplied by the common frequency of the resonators, gives the energy element epsilon in ergs, and by division of E by epsilon we get the number P of energy elements to be distributed over the N resonators".
Do you have any idea how Planck arrived at 6.55x10-27? There must be some kind of basis for it but that text doesn't explain it.
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It is essentially a proportionality constant between the energy of a quantum of radiation and the radiation frequency. It has dimensions of action and angular momentum, all of which is very important throughout any quantum theory, needless to say.
"He adduced additional evidence for the importance of his formula by using it to evaluate the constant h (his value was 6.55 ยด 10-27 erg-second, close to the modern value), as well as the so-called Boltzmann constant (the fundamental constant in kinetic theory and statistical mechanics), Avogadro's number, and the charge of the electron."
is not very helpful either, eh? I think he actually made a guess of it at first, with help of calculations to make it ever more accurate. Something quickly buried in this hagiographic 'it all came to me in a divine flash' type of scientific history-writing, we have altogether too much of these days. They are portraying these guys like some demigods, not your average dead-ordinary intelligent or even brilliant bloke full of human doubts, and at times woefully stuck, that they simply were at times.
'People we can never hope to emulate.' Hah. Hagiography, I say. Mythbuilding. Pfui.
http://uk.geocities.com/max_planck_uk/people/planck/planck.html
The living are the dead on holiday. -- Maurice de Maeterlinck (1862-1949)
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Was it Thomas Edison who said that inventing is "1% inspiration, 99% sweat" or words to that effect? The Planck thing sounds a bit like that with the 99% left out (yes, hagiography)