Space and The wonders/mysteries of The Universe

Interesting read

so Dark Matter. Is it the stuff at the edge of the Universe that leaks in. The stuff that was everywhere from before the Big Bang. and if it is, is that why its impossible to know what it is because its outside our experience?

We know Dark Matter is there because galaxies spin faster than they should just by counting up the mass of everything that glows. There's extra gravity making the orbital speeds faster. It's not ordinary matter outside of stars (easy to count) because that would glow softly in the thermal infrared. So there's some extra mass unaccounted for that doesn't interact with the electro-magnetic fields that make up light, IR, etc. It's not just a simple observation uncertainty because there would have to be 5 times as much dark as ordinary matter to account for the galaxy rotational speeds.

This was noticed 20 years ago, and still nobody knows what the hell the stuff is. And nothing is wrong with the laws of gravity because that's been tested to hell and back.

halfwise wrote:

This was noticed 20 years ago, and still nobody knows what the hell the stuff is.  And nothing is wrong with the laws of gravity because that's been tested to hell and back.

A bit of caution might be in order here. Remember that in the 19th century the Newtonian laws of gravity had been well tested too, and so when Mercury's numbers didn't quite add up the planet Vulcan was invented to explain it. Perhaps Dark Matter is really just composed of the particles of the planet Vulcan and all the other exploded theories that science has created and discarded over time?

True, but I should reword that to say that the accuracy of the current theory of gravity has been tested to such an extent and over a large enough range of scales that it can't account for a whopping factor of 5 error in mass.  Mercury was a very small perturbation, as have been all the modifications of general relativity to newtonian gravity under all but extreme circumstances.  GPS only works because of the extreme high accuracy of general relativity.  But this is not on the same order as saying  galaxies must have 5 times the mass that we see.

sorry to labour a point but if the Universe is finite and doesn't literally go on for ever there must be an edge where it stops and what if past this edge its Dark Matter in infinite quantities that goes on forever? we cant measure it because we don't have machines that have come across it before. and there's so much of it that it invades the visual Universe.

supposedly the way to think of the edge of the universe is that it's asking like what's at the edge of the earth: it has finite area, but no edge.  2 dimensions curve around into 3 dimensions.  The same can be done with the 3 dimensions of our space curved up into a 4th dimension.

This leads to the thought that beams of light that don't hit anything may come back around again.  Except that the universe is expanding faster than the speed of light, so it's like an ant trying to circle a balloon that expands faster than it crawls.  Exploring all of this is frankly beyond my depth, I must confess. Like what happens if the universe's expansion is slowing down so that the light can catch up?

I guess it's good to reflect at times that the Universe will eventually implode, leaving all human effort ultimately pointless.

I never expected humans to accomplish much anyway. We're in it for ourselves.

On further reading, the main reason people assume the universe is curved with no edge is to avoid infinity. Measurements show it's quite flat, but most measurements indicate the earth is rather flat as well, just ginormous compared to us. It could be infinite with no edge; it could possibly have an edge but people aren't sure how to deal with it; curved with no edge makes it easier, but that doesn't necessarily make it true.

halfwise wrote:I never expected humans to accomplish much anyway.  We're in it for ourselves.

So, it's not an excuse for not trying?

I agree, the human race is at its best when it's being tricked into accomplishing great things. Unless there's a bunch of pharoahs high-fiving each other somewhere, the pyramids are a great example.

Hm, so I should perhaps make an effort then?

they have to live off some very dusty and shrivelled foodstuffs in those tombs so maybe they wont be high fiving it.

I feel I'm getting mixed signals here.

It does seem to impress the ladies if you at least try.  If not then drinking light beer in front of the telly is a good consolation prize.

Who said anything about women? I was talking about school. Women is a completely different err.. kettle of fish.. err.. altogether..

The problem of how to solve the size of the universe is very easy, its obviously infinitely finite

That's no help in dealing with women at all.

halfwise wrote:True, but I should reword that to say that the accuracy of the current theory of gravity has been tested to such an extent and over a large enough range of scales that it can't account for a whopping factor of 5 error in mass.  Mercury was a very small perturbation, as have been all the modifications of general relativity to newtonian gravity under all but extreme circumstances.  GPS only works because of the extreme high accuracy of general relativity.  But this is not on the same order as saying  galaxies must have 5 times the mass that we see.

Sure, but my instincts tell me that hunting for all that invisible mass is going to be an exercise in chasing wild geese in the end.

If I had to bet, I'd bet that after decades of chasing invisible matter, eventually there will be a "Eureka!" moment when it becomes obvious that general relativity is actually just a special case of a greater gravitational theory, and once that happens "Dark Matter" books will get filed on the same shelf as books on "Luminiferous Ether".  

(Unfortunately those are the kind of bets you never get to collect on )

That's no help in dealing with women at all.- Blue


I thought I'd deal with the easier topic first Blue!

But my answer to the second point- How to deal with women is simple. Don't.

Your advocating a cold war approach? Or a complete cessation of all formal and official communication?

Well the latter might be preferable but its not very practical. But give em an inch they take a mile, and, and here's the scary bit, you wont notice they have done it

Erm.. I might have read that wrong.

I think you might have done. On the other hand if all you have to give is an inch and she gets a mile out of it, she's a keeper

halfwise wrote:It does seem to impress the ladies if you at least try.      If not then drinking light beer in front of the telly is a good consolation prize.

you just wait, my pet theory of Dark Matter will be proven accurate and I will be high fiving crazy haired popular scientists on the Discovery Channel. oh yeah.