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jugo wrote:will the universe ever stop expanding?

depends who you ask

jugo wrote:will the universe ever stop expanding?

Current experimental measurements suggest that the expansion rate of the universe is accelerating. Which means that, provuded it doesn't somehow change in the future, the universe will continue expanding.

However, we don't understand the mechanism behind the accelerating expansion rate so can't predict at the moment how this rate may change in the future.

To noobs, such as myself, I just stumbled across a rather brilliant TV series from the 80s produced by CalTech.
It's called The Mechanical Universe, the hyperlink has an episode list and you can easily find episodes on Youtube.
It's a pretty decent intro course for the High School material I'm currently dealing with so...

Also, this is mildly unrelated, but does anybody know of Western and Northern European Mathematical history preceding 0AD?
I've not yet done much looking, but a sniff at the wiki page for mathematical history isn't revealing much.



Also2, Phig, where're you studying? And no, I do not intend to follow you (presuming you're in the US). I'm planning on taking some time off (largely to sort out funding/family issues) and then going to York, back in England.



Kay, what can you tell about theories on the Mechanism? I've assumed that it's some kind of big bang aftermath, or perhaps related to Entropy and things moving toward disorder - so expansion never ending. How stupid would that be?

Also, are there any circles in which Leibniz is typically referred to as the inventor of Differential Calculus?
I know that both he and Newton are credited with it, but in all physics classes & lectures I've been in and watched, they always 'instinctually' refer to Newton.

zerbaman wrote:To noobs, such as myself, I just stumbled across a rather brilliant TV series from the 80s produced by CalTech.
It's called The Mechanical Universe, the hyperlink has an episode list and you can easily find episodes on Youtube.
It's a pretty decent intro course for the High School material I'm currently dealing with so...

Also, this is mildly unrelated, but does anybody know of Western and Northern European Mathematical history preceding 0AD?
I've not yet done much looking, but a sniff at the wiki page for mathematical history isn't revealing much.



Also2, Phig, where're you studying? And no, I do not intend to follow you (presuming you're in the US). I'm planning on taking some time off (largely to sort out funding/family issues) and then going to York, back in England.



Kay, what can you tell about theories on the Mechanism? I've assumed that it's some kind of big bang aftermath, or perhaps related to Entropy and things moving toward disorder - so expansion never ending. How stupid would that be?

The original Big Bang postulate had two possibilities for the fate of the universe:
- Eventual contraction (ie Big Crunch) because there was sufficient mass in the universe to counteract the expansion rate, and so bring everything back together eventually.
- Infinite expansion because there was insufficient mass in the universe to counteract the expansion rate of the universe.
It was demonstrated in the 90s/00s that the second case was true. However, it was then shown a few years later that not only was the universe going to expand forever, the expansion rate was actually increasing.

As far as I am aware, most of the theories dealing with the accelerating expansion of the universe invoke something called Dark Energy. As a curious (perhaps coincidental) aside, it appears to match the Cosmological Constant which was a fudge factor that Einstein once incorporated into his equations dealing with the expansion rate of the universe, which he ultimately removed because it became apparent from experimental evidence back then that made the fudge no longer necessary. No one really has any conception as to what constitutes this Dark Energy, but the theories generally think that it is equivalent to an antigravitational effect that increases in strength as masses move further apart, or which only has significant effects in the regions of space containing very little matter (eg intergalactic space).

If dark energy is indeed effectively an unknown force, and if the theory of supersymmetry holds true, then it should have an equivalent particle (analagous to photons for electromagnetism). There have been suggestions that it may be possible to produce/detect these particles using the LHC. Some researchers have also claimed that the particle may have already been detected but this remains unconfirmed.

Some other possible mechanisms include:
- Previously unobserved spontaneous changes in particle masses. This may be happening in deep space, where the concentration of matter is very low.
- Mis-accounting of the amount of high energy particles zipping around in intergalactic space. Mapping these energy distributions is ongoing work.

So none of the postulates are really based directly on entropy or the big bang. They all do have to obey the 2nd law of thermodynamics though.

(LACE can probably correct me if I've oversimplified any of the above)

With regards Calculus, Leibnitz and Newton, it takes a long time to correct history and what people have grown up learning. I doubt it has filtered down to the school level, probably not even down to the university level for most courses.

Terpit wrote:

my feelings exactly

kay wrote:

unwind wrote:

kay wrote:Unwind, which aspects of wonders of life did you have difficulty with? Life as an energy input process to temporarily impose otder against the natural tendency of the universe to slide towards disorder? Maybe we can try to help explain.

Well in the end I managed to get a pretty good understanding of most of it. It's the parts that got into the chemistry side of things, and about protons and ions etc. where I got lost a bit (never been very good with chemistry or physics at that scale), in particular where he explained that the acidity of the water in the lake is basically down to the difference in concentration of ions and protons. I've never been particularly clued up about things on that scale so it made it a bit difficult to understand. I found myself wondering why that difference in concentration of protons/ions causes acidity, and what it is about it that quality that causes it to corrode things?

I suppose it was more just me confusing myself even more by thinking further into a subject that I never quite understood in the first place, lol

Acidity is defined, essentially, as the concentration of hydrogen ions (H+) in a given solution. Water is H2O. However, it doesn't always exist as H2O. It occasionally reversibly breaks down into H+ and OH- ions (the confusion between ions and protons probably stems from the fact that a H+ ion is, in fact, a proton. Being a physicist, he probably decided to refer to H+ ions as protons while referring to the OH- ions as "ions"). Both H+ and OH-ions are very reactive. But because there are equal numbers in pure water, they effectively react with each other and mop each other up. When you have an imbalance of H+ and OH-, the solution becomes reactive because you have an excess of either H+ or OH- floating about. When there are excess H+ ions, we call a solution acidic. When there are excess OH- ions, it's considered basic (or caustic). Way back when, someone decided to make a scale based on the number of excess H+ ions in a solution. They decided that neutral water was in the middle (pH 7), a very strong acid was pH 1, and a very strong base was pH 14.

Both acidic and basic solutions corrode things because the H+ or OH- don't like to exist as charged ions. They prefer to combine with other things to form a neutral molecule. So an acidic solution will attack stuff that allows the free hydrogen ions to combine with other elements in such a way that the whole mixture becomes more neutral (and therefore more stable).

I can go into reactions a bit more but it starts getting a bit more complicated because it involves electron orbitals and their effect on stability. Let me know if you want me to do that.

Thanks kay, it genuinely makes alot more sense now.
I have to say, the last 2 episodes of WOL has really helped me to understand alot of the stuff I've previously read about but been unable to fully understand.

unwind wrote:

kay wrote:

unwind wrote:

kay wrote:Unwind, which aspects of wonders of life did you have difficulty with? Life as an energy input process to temporarily impose otder against the natural tendency of the universe to slide towards disorder? Maybe we can try to help explain.

Well in the end I managed to get a pretty good understanding of most of it. It's the parts that got into the chemistry side of things, and about protons and ions etc. where I got lost a bit (never been very good with chemistry or physics at that scale), in particular where he explained that the acidity of the water in the lake is basically down to the difference in concentration of ions and protons. I've never been particularly clued up about things on that scale so it made it a bit difficult to understand. I found myself wondering why that difference in concentration of protons/ions causes acidity, and what it is about it that quality that causes it to corrode things?

I suppose it was more just me confusing myself even more by thinking further into a subject that I never quite understood in the first place, lol

Acidity is defined, essentially, as the concentration of hydrogen ions (H+) in a given solution. Water is H2O. However, it doesn't always exist as H2O. It occasionally reversibly breaks down into H+ and OH- ions (the confusion between ions and protons probably stems from the fact that a H+ ion is, in fact, a proton. Being a physicist, he probably decided to refer to H+ ions as protons while referring to the OH- ions as "ions"). Both H+ and OH-ions are very reactive. But because there are equal numbers in pure water, they effectively react with each other and mop each other up. When you have an imbalance of H+ and OH-, the solution becomes reactive because you have an excess of either H+ or OH- floating about. When there are excess H+ ions, we call a solution acidic. When there are excess OH- ions, it's considered basic (or caustic). Way back when, someone decided to make a scale based on the number of excess H+ ions in a solution. They decided that neutral water was in the middle (pH 7), a very strong acid was pH 1, and a very strong base was pH 14.

Both acidic and basic solutions corrode things because the H+ or OH- don't like to exist as charged ions. They prefer to combine with other things to form a neutral molecule. So an acidic solution will attack stuff that allows the free hydrogen ions to combine with other elements in such a way that the whole mixture becomes more neutral (and therefore more stable).

I can go into reactions a bit more but it starts getting a bit more complicated because it involves electron orbitals and their effect on stability. Let me know if you want me to do that.

Thanks kay, it genuinely makes alot more sense now.
I have to say, the last 2 episodes of WOL has really helped me to understand alot of the stuff I've previously read about but been unable to fully understand.

Small thread bumpage as I've been slightly avoiding all of this whilst I couldn't find time to watch WOL.

Watched the first episode last night and slightly embarrassingly, I'm not sure I'd ever truly understood pH until seeing Cox's explanation. Kay's been wonderful enough to put it into words that confirm I did indeed understand.

This is exactly what the telly is FOR. I can't wait to get onto episode two tonight!

Episode 2 was good. Episode 3 is great! Lion cubs and lemurs!

Also, did you watch the penguin cam programme? Started on Monday. Supposed to be brilliant and hilarious!

Not even heard of it! I'm totally out of sync with the iPlayer at the moment.. got an extra special night of absolutely fuck all booked in tonight so I'll probably end up watching it... thanks for the heads up!

kay wrote:Episode 2 was good. Episode 3 is great! Lion cubs and lemurs!

I'm up to date now... Episode 3 really was amazing, but I've got the right horn for Octopus brains, so episode 2 had me all excitable too. From the way Ep3 finished, I guess that was the last one? Could've watched this all year tbh.

Beautifully produced too... the little floating annotations and diagrams worked brilliantly whilst making the whole thing stay kind of fun. BC always picks his experiments well too - the cloud chamber was excellent... V and I are going to try and make one, I think! It's made me think I probably need to get any procreating out of my system before I get a chance to leave the atmosphere though...

magma wrote:

kay wrote:Episode 2 was good. Episode 3 is great! Lion cubs and lemurs!

I'm up to date now... Episode 3 really was amazing, but I've got the right horn for Octopus brains, so episode 2 had me all excitable too. From the way Ep3 finished, I guess that was the last one? Could've watched this all year tbh.

Beautifully produced too... the little floating annotations and diagrams worked brilliantly whilst making the whole thing stay kind of fun. BC always picks his experiments well too - the cloud chamber was excellent... V and I are going to try and make one, I think! It's made me think I probably need to get any procreating out of my system before I get a chance to leave the atmosphere though...

Octopi always win hands down - I replayed the bit towards the end of the segment about 5 times. I think it was episode 3 of 5 on the iplayer website.

I spent 4 years earning my masters degree in physics... jesus fucking christ it nearly killed me.

electrical engineering signing in.

mthrfnk wrote:I spent 4 years earning my masters degree in physics... jesus fucking christ it nearly killed me.

I find Physics fascinating, I really do but, as someone who no doubt, knows the subject fairly well can I ask you 2 rather stupid questions.


What practical need is there to understand things like the kinetic energy of a system of particles?

What's the point in laws like the conservation of linear momentum when they only exist hypothetically in a system where external forces are not at work on the 'affected particles'?

Leave Blank wrote:

mthrfnk wrote:I spent 4 years earning my masters degree in physics... jesus fucking christ it nearly killed me.

I find Physics fascinating, I really do but, as someone who no doubt, knows the subject fairly well can I ask you 2 rather stupid questions.


What practical need is there to understand things like the kinetic energy of a system of particles?

What's the point in laws like the conservation of linear momentum when they only exist hypothetically in a system where external forces are not at work on the 'affected particles'?

The kinetic energy of a system of particles can translate into the effective pressure of a gas or the temperature of a gaseous or liquid system. In solids, its the movement of electrons that determines heat transfer rates and electrical conductivity.

Conservation of linear momentum still allows us to make good predictions of interaction outcomes on a macroscopic scale. The only reason it isn't as usefully applied on a particle scale is simply because we still lack the computing power to take everything into account. But approximations still give us pretty good results.

Is physics even important now that we have electricity and good technologies? Im pretty sure we don't need it anymore

Terpit wrote:Is physics even important now that we have electricity and good technologies? Im pretty sure we don't need it anymore

I'm pretty sure that statement is invalid, it's like saying "we can breathe, we don't need oxygen". Why do you think "good technologies" get better every year?

Also @ kay, nice explaining, in relation to the practical needs of understanding and utilising KE stuff - engines are a great example of where understanding the transfer of energy within the system is paramount, no one's going to buy cars with inefficient engines Similarly COLM is equally as useful, even when drawing approximations.

I used to find stuff like this interesting, but frankly my brain got a bit mushed towards the end of my degree learning the advanced stuff and tbh it's just disinterests me completely now.

Terpit wrote:Is physics even important now that we have electricity and good technologies? Im pretty sure we don't need it anymore