What is the Mass / Energy of a Cubic Lightyear of empty space?

[JulianO]

that's a very apt quote Julian... the theories i am currently working with are completely supported by experiment.

I really shouldn't reply, it is just too amusing though! Completely supported - oh dear.

So just which lab have you built a star in, where is your test galaxy that you can experiment with You did say completely - that these experiments scale to cosmic scales and that's completely support by experiment?

I have an open mind but I think I'll need some evidence that there is anything to these different ideas.

In science, we use a method we call the three legged stool approach.. Observe, Theorize, Experiment ...

Well in astronomy we don't have that luxury. As no one (yourself possibly excepted) has managed to create a star in the lab, let alone wait the millions or billions of years for it to evolve, we're a little restricted to observe, theorize, and model. As for galaxies and universes, they're even more tricky to make

dark energy and matter can only be addressed using the first 2 "legs", the first being interpreted and the third hypothetical, based on pure mathematical theory alone, therefore the stool only stands using one hec of a balancing act...

We observe multiple ways in which observation doesn't match original theory, we propose a theory (dark matter) to account for it (and others with less success), then we construct computer models to run simulations to test our theories. They do pretty well these days - statistically and visually the same as we observe. We can make an almost identical facsimile of our universe with these models starting seconds after the big bang, but only if they include dark matter so far. Meanwhile there are lots of groups trying to detect DM particles in many different ways (experimenting as best they can) - inconclusively so far - some groups report success, others not, but its fair to say no one has reached anything close to believable results yet. The LHC may be able to make some of the DM candidates too - we await results.

I'm willing to explain how dark matter solves a number of the issues of galactic and cosmology. I think I can explain it to a reasonable degree although I admit to struggling with some of the deeper cosmological arguments, I'll even chuck in a couple of the opposing theories too. Can you explain in basic terms how the theory you support works and why we managed to get to Jupiter, Neptune and beyond without it?

I'm not wedded to the theory - its just got the most going for it at the moment and you have to back something. It explains pretty much all observational anomalies, it works great in modelling, it also seems to follow Occam's razor to a degree (things would be more consistent it there were more mass in the universe).

I think I'll (try) and leave it there, thanks for playing!

[grey]

You presume too much, i never discounted the effects of gravity nor did i in any way say that gravitational effects are not to be considered, on the contrary. calculating orbital trajectories for spacecraft bound for any destination in our solar system require precise calculations involving Newton's law of gravitation, Kepler's law of planetary motion among other things like Hohmann's minimum-energy interplanetary transfer trajectory...

i also never claimed to "building a star" or knowing how they are built for that matter...however i do know that the fusion model of a star is totally unsupported by observation.. coronal temps in the tens of millions of degrees with a surface temp of 6000 degrees, and lower temps observed in the umbras of sun spots all the while supposedly having a core temp between 15 and 18 million degrees, explain that one! it can be using plasma physics if it were externally powered... while true that focusing 192 lasers on a microscopic deuterium target causes fusion for mere nanoseconds, i'd hardly equate that to "creating a star", it's a simple albeit costly fusion reaction, a H Bomb is far more efficient... your defense is unfounded and your tone is petty and condescending. My area of study is primarily astrophysics with extra disciplinary studies in plasma physics and electrodynamics and see no requirement to justify my opinions in this fora while people like yourself pick apart my responses and reply with denigratory / inflammatory remarks instead of engaging in educated and polite discussion. I've at least afforded you that courtesy...

see if you can leave it there, i know i will

[grey]

parting thoughts

part 1:

part 2:

enjoy