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Afzaal Ahmad Zeeshan wrote: Physics, needs abnormal people, who are able to imagine the world in an unusual way.
I have to disagree with that.
IMO, Physics needs people who can see the bleeding obvious without getting bogged down by ideas that sort-of work but don't.
I wanna be a eunuchs developer! Pass me a bread knife!
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It doesn't matter what 'shape' space/time takes in the slightest. The flat rubber sheet is, after all, a huge abstraction for the purposes of demonstrating the displacement theory of gravity. What 'dark energy' is supposed to explain is not expansion per se but the perceived acceleration of that expansion against all logic if you accept the standard cosmological model. Personally I can't help thinking that if you have to start making up stuff to fill in the gaps in your model than it's probably time to bin the model but then my living doesn't come from grants for research in theoretical physics!
I did wonder to myself the other day if the explanation could simply be that as inflation increases, and the distance between masses increases along with it, gravitational drag is reduced, ie. the brakes are taken off, but then I figured if I'd thought of that there's probably a couple of thousand papers out there telling me why it's rubbish. Sometimes it's easier to sleep at night just knowing what you don't know.
I am not a number. I am a ... no, wait!
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Yes, but it's all based on "observations" of a handful of supernovae seeming to cool faster than expected, and an assumption based on that that they're moving further away quicker than was previously assumed.
Me, I reckon that since we don't know precisely the dynamics of supernovae, something else is happening either to make them cool faster than anticipated, or to block/absorb some of the heat, again making them appear to cool faster than anticipated.
Something like an expanding cloud of dust that's recently been fused into higher-order atoms and molecules would likely have that kind of effect -- but what are the chances of something like that conveniently surrounding a supernova, eh?
Nah, it's much more likely that some idiot needed to publish something radical quickly, or lose his research grant there's some mysterious "dark" thingummy that's at back of it all.
I wanna be a eunuchs developer! Pass me a bread knife!
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When peer reviewed papers are, erm, peer reviewed that's exactly the sort of question that gets asked.
And just to be picky, they're not 'moving away more quickly' they, and everything else, is expanding so, while the novae are getting further away, they are also getting larger.
the analogy of the 'raisins in dough' so often used is only legitimate if raisins also expand in the oven.
PooperPig - Coming Soon
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Maxxx wrote: if raisins also expand in the oven
Which of course they do, absorbing moisture from the mix.
I am not a number. I am a ... no, wait!
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Weeeellllll that depends on how dry they are, how moist the dough and how long you cook for, and what is the cosmological constant...
PooperPig - Coming Soon
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_Maxxx_ wrote: they, and everything else, is expanding so, while the novae are getting further away, they are also getting larger.
I think you might have misunderstood something you read, there.
Nothing's getting bigger (well, novae get bigger because they're explosions), it's all just moving apart. It's the universe that's expanding, not the suns, planets, and teaspoons.
I wanna be a eunuchs developer! Pass me a bread knife!
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you're right. I was wrong!
damn - I'm as confused as when I found that the Hubble constant isn't!
PooperPig - Coming Soon
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Not your fault.
There's so much written on the topic using such poorly crafted language that it's not surprising that people get wrong ideas.
I wanna be a eunuchs developer! Pass me a bread knife!
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Some sorta "dark energy" is driving some posters here.
... such stuff as dreams are made on
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It seems that when these ideas are presented above, it is assumed that the ball(s) are attracted by a force below the rubber surface. I might say that it is in the center of that expanding rubber "balloon". Now here is an interesting clue. It has been discovered that not just the universe is expanding, the expansion is accelerating. The balls or mass-objects are not attracted to anything, it is the moving rubber surface that is accelerating toward the mass-objects(balls). If the expansion of the universe was just at a constant rate, there would be no gravity. It all runs on dark energy. It's just a thought. No, I didn't do the math.
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ronDW wrote: it is assumed that the ball(s) are attracted by a force below the rubber surface
Nah, it's just an analogy that, although it uses three dimensions to demonstrate the movement of smaller objects, only demonstrates the effect in two-dimensions.
ronDW wrote: It has been discovered that not just the universe is expanding, the expansion is accelerating
It really hasn't been "discovered"; it's been huge-leap-of-silly-supposition assumed, based on virtually zero data.
ronDW wrote: If the expansion of the universe was just at a constant rate, there would be no gravity
This is true. Coulomb's Law (known only as the Inverse-square law, in the US, because Coulomb wasn't American) wouldn't have it otherwise.
ronDW wrote: I didn't do the math
Nor did I, but Physics isn't about Maths; it just uses it to confirm observations.
And these guys didn't do the Maths, either. They used statistical analysis -- and real mathematicians don't like statistical analyses.
I wanna be a eunuchs developer! Pass me a bread knife!
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Maxxx wrote: we represent 'spacetime' as a flat sheet (usually black rubber with white grid lines)
That's just a projection onto a 2D surface so that the uneducated masses can go "oooh, I understand Einstein now" when they visit the science center.
In reality, it is the three dimensional space we live in that is curved. It looks straight because there's so little curvature created by the planets or even the sun. But it'll look a lot different near a black hole!
Marc
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OriginalGriff wrote: Or even a long way away from a galaxy!
Exactly!
Marc
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Marc Clifton wrote: That's just a projection onto a 2D surface so that the uneducated masses can go "oooh, I understand Einstein now" when they visit the science center.
Very true - but a convenient demonstration nonetheless.
Marc Clifton wrote: But it'll look a lot different near a black hole!
True - but in the sheet analogy the black hole is a vertical-sided well - so the demonstration model holds up quite well.
ripple the sheet and you get gravitational waves
stretch it - expansion of the universe (though have to stretch your balls too - which some may find a less than pleasant experience :grin
PooperPig - Coming Soon
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You can create any concept you want: a big sphere or a chicken shaped multiverse. It is just a concept like space time.
Physics is not the science that was a thousand years ago. Instead of analyzing the real world, physicists try to "blow our mind" with some superstition theories about space-time. As a programmer, I do not believe them. Variable is not the same as an actual object, it is just a placeholder for a concept related to an actual object, so we can work with it.
tl,dr; Too much modern physics is just based on misunderstanding mathematical concepts and representing it as something great.
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Plamen Dragiyski wrote: It is just a concept like space time.
Well, I'd like to see the mathematics to support a chicken-shaped multiverse!
Plamen Dragiyski wrote: physicists try to "blow our mind" with some superstition theories about space-time.
Seriously?
Plamen Dragiyski wrote: As a programmer, I do not believe them.
What? That's like saying "As a programmer I don't believe in God" the two things are unrelated!
so are you seriously saying you don't believe in spacetime? Do you not believe that the rate of passage of time varies by the observer?
this effect is real, and measurable, and used IRL !
PooperPig - Coming Soon
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Maxxx:
Your extension of the "rubber sheet" metaphor is an valid way of visualizing the action of the cosmological constant. So I think that you're providing a useful analogy to explain its action, rather than suggesting an alternative.
My own position regarding dark energy is rather more revolutionary, and motivated by a far simpler proposition. Dark Energy cannot be moving at all speeds in all directions. Since it interacts with regular matter, it therefore establishes a preferred reference frame. Einstein's theories of special and general relativity go out the window.
So I think that physics has gone on a long detour since 1860, when the Michelson-Morley experiment was done. This was an experiment that sought for evidence of the "aluminiferous ether" - the medium in which light waves traveled - by measuring the change in the velocity of light as the earth circled the sun. It did not detect any change, and so physicists adopted the view that space was empty. But there's another explanation: the speed of sound does not vary as the earth circles the sun, because the air is entrained with the motion of the earth. Dark Energy must be entrained with matter and carried along with it as it moves. This allows a whole lot of interesting possibilities for explanation of general relativistic effects.
Brian
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If you want to learn more about Dark Matter and Dark Energy, read the book "Dark Side of the Universe" by Iain Nicolson. It's pretty technical and filled with charts and graphs but nothing the people in this forum couldn't comprehend. It's also a little dated - astronomy/cosmology have progressed as fast as computer hardware and software in the past 20 or 30 years (largely because of advances in computer hardware and software).
There are mountains of data that support the current theories of General Relativity, Dark Matter, Dark Energy and the existence of planets around other stars. Those theories have evolved as more data is gathered.
The community of astronomers and cosmologists is as dedicated, hard-working and objective as the community of coders/developers. No more and no less. Conspiracy theories about astronomy have about as much validity as conspiracy theories about the latest version of C++.
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That is how curved spacetime is commonly viewed since Einstein. The model about galaxies moving apart is not the problem. However, since measurements have shown that the galaxies not only move apart, but also accelerate doing so, the big question is what drives that acceleration?
The only force we know that works to any measurable effect at cosmic distances is gravitation, but gravitation is an attractive force, whereas what we see appears to be some kind of repelling force. This force is called dark energy, and, so far, we have not the faintest idea what it is, or where it comes from.
One idea *I* have been considering is that there is no repellant force after all. Instead, there could be something beyond the visibility horizon that attracts the far removed galaxies - through gravitation. We already know that continued inflation will eventually fling the visible galaxies so far apart that we will no longer be able to see them, or even realize there are such galaxies outside our field of vision. We cannot be sure that this isn't already the case! So, what if the brunt of the mass of our entire universe is already beyond our field of vision, and what if the outermost galaxies are already rebounding due to the cumulated gravity of the entirety of the universe? This would cause a relatively strong concentration of mass close to the real (invisible) boundary of the universe that may have a stronger gravitational effect on the galaxy that are close to the boundary than the cumulated gravitaty of the 'inner' galaxies. I'm not sure how to model this mathematically though, and have some doubts that such a scenario is even possible - if it were, I'm sure some scientists would have worked it out by now.
Another possible explanation I could think of is based on the inflating rubber ball analogy: think of god as a 'little' girl, who tried a little too hard to inflate a five dimensional balloon until it burst? That burst is the big bang, our universe is not the (four-dimensional) surface of the balloon (which existed before), but the (3-dimensional) fringe of the tear! The force that apparently speeds up the expansion of our universe in truth is the contractive force of the rubber balloon that pulls the fringes of the rubber away from the origin of the burst 
Ok, I don't think that theory will hold up to scientific scrutiny either, but at least it is fun working out the details. Also it is a much more realistic story of creation than any contemporary religion can offer. Unfortunately, it won't be a very successful religion until mankind can adjust to the idea of god as a five dimensional little girl 
GOTOs are a bit like wire coat hangers: they tend to breed in the darkness, such that where there once were few, eventually there are many, and the program's architecture collapses beneath them. (Fran Poretto)
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Interesting thoughts - I"ve certainly known some 5 year olds who *thought* they were god!
Acceleration is the change in velocity over time. And velocity is change in position over time.
So - what if it is *time* that is changing ? If, in fact, from their own POV every distant star, galaxy etc. are moving at a constant velocity, but from our POV time slows as a function of distance, then they would appear to be speeding up.
This would make sense also from a space-time expansion perspective. Space expands and time contracts by way of conservation of energy.
Simples!
PooperPig - Coming Soon
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So it's been almost one and a half year since I moved out on my own, got a new job, and moved my old desktop PC to my new home office... Where I never come because why would I sit in a cold office when I got a whole house to myself? The living room is heated and has a kitchen, so I prefer sitting there. With my new laptop provided by my employer.
Now, almost one and a half year later, I finally moved my desktop PC to the living room (on the kitchen table which I've used exactly three times to actually have breakfast/lunch/dinner on  ).
I finally have an actual monitor and keyboard again! 
My desktop PC is a little slower than the laptop, but it has a lot more HD space (the laptop has about 230GB SSD, whereas my PC has 2TB non-SSD).
And of course I can install whatever I like on my desktop PC because it's mine and not my companies!
Although now that I'm working on this thing again I notice my keyboard could really use a replacement... It came with my first Win 95 PC and the keys are huge and a little hard to press 
So anyway, back to PC gaming! 
This gon' be good!
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Sander Rossel wrote: My desktop PC is a little slower than the laptop
There go the deadlines...
No, wait...
Sander Rossel wrote: So anyway, back to PC gaming!
There go the deadlines!
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