]]>
]]>
Ok, got that – so in respect of where I’ve used mass we could for (arguments sake) then exchange it for energy. I still find that hard to grasp firmly – especially with the nuclear explosion example. My understanding of nuclear fission is that an unstable molecule (i.e. one that has an imbalance of electrons) is caused to liberate it’s “spare” negative charge by the application of an external force (be it due to an implosion pressure generated by explosives as in the Manhattan project or by other means) that in turn causes neighbouring molecules to do the same in the domino effect. The liberation of these particles causes a release of energy but surely doesn’t actually destroy them does it, otherwise how does the chain reaction remain self perpetuating? If it does, it wrecks the notion of matter not being able to be destroyed, but only changed. Please enlighten me a bit more on this if you can.
Vacuum - it all depends how you define "vacuum". We tend to think of a vacuum as a region of space with nothing at all in it, but, for a scientist, a vacuum is simply the emptiest that space can be. If any area of space is harbouring as little energy as possible then it is a vacuum. But the laws of thermodynamics dictate that (for the universe as a whole) there will always be some energy present. So the creation of a vacuum doesn't mean zero energy.
Right, that’s cleared up one then. Vacuum per-se is not an area of space that contains absolutely nothing, but an area that contains as little energy as is possible for the volume of the universe as it is at the point in time that it is calculated. To extrapolate that theory further then, if the universe is expanding it is reasonable to say that the static atmospheric pressure of the universe (in other words how much of a vacuum the vacuum is) is actually dropping constantly until such time as the expansion stops, and therefore as the laws of thermo-dynamics state a reduction in pressure equates to an equivalent reduction in temperature. To put it simply, as the universe gets bigger, the vacuum pressure of space gets lower (a greater vacuum) and the temperature of the universe drops. Please kick me up the arse if I’m barking up the wrong tree here.
Dark matter, dark energy and the rate of the expanding universe. I think you've got the cart slightly before the horse on this. The positing of dark matter and energy didn't lead to the idea of an excellerating universe. On the contrary, it was the empirical observation that the universe is expanding at an excellerating rate that forced scientists to posit the notion of dark matter and dark energy. The laws of gravity cannot explain the observed excelleration given the amount of "normal" matter thought to exist. Dark matter/energy are therefore theoretical expedients - either there's something like them out there or pretty much everything we know about physics is fucked.
Sorry, this came across arse about face when I wrote it (I did say it was hard for me to get down what I wanted to say!). I accept that the dark matter/energy theories were formulated from the discovery that the universe seemed from observation to be accelerating in growth as opposed to decelerating which was to be expected. As for our theories on physics being fucked – well that was the conclusion that I came to as well. I was hoping that somebody had come up with some concrete evidence to the existence and nature of either that would at least prove our understanding of the universe as proposed by Einstein and Newton, instead of the “well we can’t explain what’s happening so it must be this” argument. By the sound of things, the dark matter/energy thing has become the Holy Grail of physicists.
More profoundly, light waves didn’t move at a speed dictated by their medium or the movement of the observer. Sound travels at 767mph at room temperature. Change the temperature of the air and the speed of the sound wave changes too. But light travels at 670 million mph no matter what. And if you swim away from a sea wave it will approach you more slowly (from your point of view). But it you move away from a beam of light it will still come at you at 670 million mph (from your point of view). And, amazingly, if I watched you chase a light beam at 500 million mph I would see the light travelling 170 million mph faster than you, but you would see the light travelling 670 million mph faster than you.
Well that’s confused me totally! That throws my interpretation of relativity out of the window, and dances around it in a flowery costume…. How is that physically possible (and how on earth has it been proved)? What would happen if I was travelling at the same speed as a beam of light? Would it still appear to be travelling at twice my speed or would it appear stationary? In that case, what would happen if I was to travel faster than the speed of light (though it’s my understanding that C is regarded as an impassable barrier as far as physicists are concerned)?
It was Einstein’s special theory of relativity (1905) that sounded the death-knell for the aether. He pointed out that Maxwell’s equations describing the motion of light invoked no kind of aether and experiments had failed to find anything like it. Theory and experiment pointed the same way: there was no aeither; electromagnetic waves, unlike any other type of wave, needed no medium and hence could travel through space.
Hmmm…. Not totally convinced with the electromagnetic waves need no medium to travel through argument (sorry Albert – you are one smart cookie but the juries still out on this one). Aether was, is, and will always be a bollocks argument. Write that off right now. I still feel much more confident with the space isn’t a vacuum theory and movement of electromagnetic waves is due to them influencing molecules in space. As light is an electromagnetic wave, it must be influenced by other electromagnetic forces that it passes through in space – in other words it must be able to be bent by the gravitational pull of stars and the like (or am I again making a crass assumption?). If not, black hole theories get kicked into touch surely? Saying that, the whole “what actually is light” debate springs to mind when you try to apply it to E=MC2. As light is an electromagnetic wave it can’t have a mass can it, and thus how does this equate to the energy contained within it? AHHHHHH my head hurts now!!!!!
In 1826 Heinrich Wilhelm Mathius Olbers, the discoverer of the minor planets Pallas and Vesta, reformulated the paradox; "Why is the sky dark at night? The intensity of light reduces with the square of the distance from the observer. If the distribution of stars is uniform in space, then the number of stars at a particular distance from the observer should be proportional to the surface area of a sphre whose radius is that distance. At each radius therefore the amount of light should be both proportional to the radius squared and inversely proportional to the radius squared. These two effects will cancel and so every shell should add the same amount of light. In an infinite universe the sky would be infinitely bright."
Got (what I think is) a reasonable argument on this. Light travels in a straight line (except when a star or black hole gets in the way ). The size of our sun greatly dwarfs our planet. When the earth is facing the sun (from the perspective of somebody standing in daylight of course) it is bombarded with a great percentage of the total amount of light being given out by it. In other words, imagine somebody shining a torch on a wall. When they’re close to the wall the spot of light is small but bright, as the distance increases the spot gets larger but dims (as explained above). The amount of electromagnetic energy doesn’t reduce, just the area that it objectively affects increases. Now take the torch 5 miles away – the light from it still travels all the way to the wall, it’s just the effective area it is covering is now massive. To the observer at the wall the light is still visible as long as the electromagnetic energy being generated is greater than the background noise (in other words if it’s dark enough you’ll see it) but appears to be a pin prick. We know the source isn’t that small – but our eye only detects a small amount of the energy being generated. To take this to its logical conclusion, if it was dark enough and you could get it far enough away there must be a point in space where you would detect just one single solitary beam of light being generated by the source. Blow this up to interstellar distances and the light from the most distant of stars must also do the same thing. Also, it’s worth bearing something else in mind as well – the effective shadow of stars that are nearer to the earth than others, once projected out into the far extremities of the universe is enormous. If you consider our point of viewing the universe is extremely small in the great scheme of things it is reasonable to conclude that quite a large percentage of the universe would not be visible to us.
Even those who realised that the theory of gravity would cause a collapse did not consider the possibility that the universe was expanding. They all, including Einstein, imagined a repulsive force that worked only at very large distances. This would allow the planets motion to be correctly explained by Newtonian gravity and allow for the creation of galaxies but stop the wholesale collapse. Unfortunately, even with this extra repulsive term most models would not be stable. Trying to balance something between two opposing forces leads to instability when some small perturbation affects an object. Pushing down on a long stick starts off fine but after a certain amount of force the stick suddenly shoots out sideways and snaps
Again, not totally convinced with this repulsive force idea. Newtonian gravity theory explains to me why the planets in our solar system are all gradually evening out their orbits into one plane around the rotation of the sun, and their individual rotations (both planetary and regarding their satellites) are all starting to straighten up on their axis. To accept there is a repulsive force at work would require a certain amount of chaotic movement of the planets to my mind.
To be continued…….
Time for a pint and an aspirin! Thanks for all the effort so far guys, my mind is expanding as we speak – anybody who tries crack the joke about vacuums and my head you’ve missed the boat!
Statistics: Posted by Bananas — Sat Feb 25, 2006 6:53 pm
]]>
]]>
]]>
]]>
]]>
]]>
]]>
]]>
RE: vacuum - it all depends how you define "vaccum". We tend to think of a vaccum as a region of space with nothing at all in it, but, for a scientist, a vacuum is simply the emptiest that space can be. If any area of space is harbouring as little energy as possible then it is a vacuum. But the laws of thermodynamics dictate that (for the universe as a whole) there will always be some energy present. So the creation of a vacuum doesn't mean zero energy.
RE: dark matter, dark energy and the rate of the expanding universe. I think you've got the cart slightly before the horse on this. The positing of dark matter and energy didn't lead to the idea of an excellerating universve. On the contrary, it was the empirical observation that the universe is expanding at an excellerating rate that forced scientists to posit the notion of dark matter and dark energy. The laws of gravity cannot explain the observed excelleration given the amount of "normal" matter thought to exist. Dark matter/energy are therefore theoretical expedients - either there's something like them out there or pretty much everything we know about physics is fucked.
RE: the amount of mass in the universe. I think it would be more accurate to say that the amount of energy in the universe is constant. Mass can be converted into energy (as happens in a nuclear explosion) and when that happens the amount of mass in the universe is actually reduced, but the amount of energy remains constant.
Statistics: Posted by Captain Howdy — Wed Feb 22, 2006 1:07 pm
]]>
Ok, I’ve spent the last few days working out what I want to ask – now just to get it down in words (this would be so much easier to do over a few pints and a large sheet of paper!). Anyhoo, bound to forget to ask something here so expect a few follow ups…
Firstly I’m no expert on advanced physics (it still takes me 3 attempts to spell the bloody word) so if I make some dramatic and monumental cock up in what I say please don’t pillory me for it. Secondly, what I have gleaned on the subject is all self taught/read up on/scammed off TV, so blame somebody else if I haven’t got a clue with what I’m saying!
Onwards and upwards….
Ok – principles which I believe to be true….
1. The Big Bang Theory of the creation of the universe is accepted as fact by most scientists:
At T (time) = 0 (in other words the exact moment the universe was created) all the matter in the universe was packed into one big lump at its centre, that due to the enormous gravitational pull of itself caused a massive implosion that scattered itself back out in all directions thus creating the universe. This matter initially flew out at the speed of light for a miniscule fraction of a second and then immediately started to decelerate gradually – the thought being that if it wasn’t slowing down below the speed of light we wouldn’t be able to see anything travelling away from us. Unless this bizarre “Dark Energy” theory is correct then I’m totally buggered – more about that later.
So, by definition then, there is a finite amount of matter in the universe, which eventually will (due to gravity) all start imploding back upon itself until at some point in the far future it will all pack back to one big lump at the centre of the universe and the whole process will happen again. If this is correct then it’s reasonable to assume that the universe is spherical and has an eventual end (what’s beyond that edge has been left to the theologians to explain!).
2. A smart bloke called Albert can up with the theory (well there were a few he came up with but this is one of important the ones) that time travel is in theory possible if you were capable of accelerating an object towards a target point in the universe at a speed greater than the speed of light.
Ok with that – relativity in time and space obviously to be born in mind. Another of his great discoveries was E (energy) = M (mass) x C (speed of light) squared. So by juggling the equation we would see that to accelerate even a small amount of mass to anywhere near the speed of light would require an enormous amount of juice (in other words humanly impossible for us to achieve at this time with anything larger than an electron or other sub-atomic particle).
Still with me?
Ok, what do I want to have cleared up then…..
1. Space….the dark bit between the big lumps in the galaxy….everybody says it’s a vacuum. Surely this is a fallacy? There must be something filling the gaps? Gravity – i.e. Magnetism requires some medium to “pass” through (some molecules to have their polarity aligned) otherwise it would have no effect wouldn’t it, and the planets in our own galaxy would fly off in all directions. So is it true that space per-se is not a true vacuum, it is “filled” with molecules that are so far apart that the effective atmospheric pressure generated by them is impossible to measure as it is so small. This would make some sense to me if the finite matter in the universe theory holds up. If the universe is expanding spherically out at a fair rate of knots then the effective volume of that sphere must be growing at an enormous rate (err…Pi R cubed is it? – my maths is worse than my physics) so the atmospheric pressure of the universe must be falling at a consistent rate – same number of particles in a bigger space = lower static volumetric pressure and reduced universal temperature.
So….is space a true vacuum containing nothing at zero atmospheric pressure, or is it made up of lots of particles that are just so far apart that it is impossible for us to measure their effect?
2. What’s with this imbalance in the measurement of the matter in the universe? From what I believe, scientists can only account for something like 20% of their predicted total mass in the universe a figure that rises (from memory if I’m roughly correct) to around 35% if they include Anti-matter (now there’s a subject in itself). Now I hear that some boffin has come up with the theory of “Dark Energy” which miraculously works out to the exact missing 65% of universal mass. What the hell is Dark Energy, and how does it work? The people who have come up with this idea also seem to be saying that the universe is instead of gradually slowing down as it expands, actually accelerating. Now forgive me ignorance, if this is true surely it knocks the Big Bang Theory into touch, and flicks the V’s to Newton’s ideas. How can something be accelerating without an external force being applied to it? This Dark Matter thing just seems too much of a convenient answer to an unexplained question!
Is it not possible that as we are hurtling away from the centre of the universe at a speed in excess of 0.5C, whilst a large proportion of the universe is heading the opposite direction at the same speed, and therefore the combined opening speed between here and there would be in excess of C? If so, this would explain a lot of the missing universe – it is of course there but you can’t see it and they can’t see us. Unless you were in the centre of the universe looking out you would never be able to see or measure the entire mass of the universe purely because you can’t measure what can’t be seen! Saying that, if this idea is feasible then as the expansion started to slow down, more and more matter would become visible and measurable (in fact there would come a point probably I would guestimate at about half-way through the implosion part of the universal cycle where all the matter in the universe would become visible from here – I need a mathematician to work that out accurately). This would also go some way to explaining why the universe may be accelerating away and not slowing down, though really I’m struggling to make sense of this accelerating universe thing.
3. Time travel….got some issues with this subject! Got a reasonable grasp of what Albert says, but need some clarification on the basics. If you were capable of travelling in excess of C towards something then by definition you can arrive at that point in the universe before the light you saw when you began arrives at you initial starting point. But surely you would not be able to travel back beyond the point in relative time that the light you initially saw left its origin. In other words for example the light from an object (point A) takes 1 minute to arrive at your objective (point B). If you were capable of accelerating instantaneously to a speed in excess of C you should be able to travel in space to point A and arrive before the light you saw departed. However (if my understanding is correct) you couldn’t travel to a point in time beyond that minute otherwise you are defying Einstein’s basic laws of space-time and relativity. If somebody was viewing you from point B, you wouldn’t appear to be travelling back in time by a minute, but would actually only travelling in space. The point in time when the light reaches point A is “effectively” frozen, and you could only travel so far back in time as the time the light took to arrive at point A and no further. This means that if you were to travel interstellar distances you would arrive there at the point in time that the light departed that would be many years in the past, but to somebody viewing it from point B you would just seem to materialise there instantaneously. Why did I come up with this theory? Back to the old finite matter in the universe thing – for an object to travel in time would mean that at the point in the past when it arrives there would be more universal mass present than before the object arrived. I can’t think who it was who said that you can’t destroy or create matter; you can only change its form. So the extrapolate that idea to its conclusion, for a mass to travel back in time to a point in time beyond the origin of the light viewed from the point of origin arrives would require an equal amount of mass travelling the opposite direction into the future arriving at the same instant that you depart to go into the past. Again this would mean something in the past accelerating towards your point of origin at the same speed that you would travel into the past to (a) make space for the arrival of your mass and (b) to fill the hole of the mass that you left behind. This then can only confirm my understanding of the idea that you could only arrive at a point in space-time that is equal to the point in time that you departed – unless you make an arrangement with somebody in the past for them to leave at the exact point in time to arrive in your exact point in space-time as you depart weighing exactly the same amount of mass as you (otherwise according to E=MC2 it dictates that there would be a hell of a big bang when you tried it!).
So, to recap,
1. Space. Vacuum or not?
2. Dark Energy. What the fu…..? Or is there a faster than the speed of light thing going on?
3. Time Travel. Is the distance you can travel back in time dictated by the time the light took to travel the distance from source to objective.
4. The Big Bang. Like the theory, and it explains a lot. Is it widely accepted that it’s the way the universe was formed, or are there other theories that stand up to scrutiny?
5. Mass. Is it true to say that there is a finite mass in the universe, and that figure is impossible to change?
6. Was Newton right, or can the universe really be accelerating instead of slowing down in its expansion?
7. Is D Minor the saddest of all the chords?
8. Should I really get a life and stop giving myself headaches thinking about shit like this?
Any ideas, theories and head-slapping “dohs!” welcome!
There will be more to come, beware!
Statistics: Posted by Bananas — Wed Feb 22, 2006 12:11 am
]]>
]]>
]]>
]]>