Why? They have energy, and energy and mass are interchangeable after all
yeah, but something doesn't 'click' for me - didn't think E=MC^2 applied in the same way to zero mass 'particles' - but I get confused on the differences between resting mass and quantum mass....
...good job I'm a biologist and only have to think down to the size of molecules because subatomicals are far too quirky for me, and as for cosmologicals 
I am not sure about general relativity and photons and stuff but I was making the point that there's a lot of strangeness.
That's why the language of Physics is Maths. If you knew all the equations it'd make perfect sense.
is it ok to not really understand this stuff but to be completely fascinated by it? cos I am.
molgrips - Member
.....I was making the point that there's a lot of strangeness.
Yeah, great isn't it - reality, but not as we know it 
wish I was brainy enough to do proper mathemetictacs 
Yes. But remember that it's really just waffle unless you do the maths, so to speak.
molgrips - Member
Yes. But remember that it's really just waffle unless you do the maths
I'm happy enough for brainy folk to do the maths and just 'look at the pictures'
It might help by starting from some fundamentals. All matter interacts through one of four forces via a field. These forces are:
1) strong force - couples quarks inside nuclear particles. gets stronger as particles move apart.
2) weak force - responsible for changes in these nuclear particles (radioactivity). Acts over a short range
3) electromagnetic force - charge dependent and gets weaker as particles move apart.
4) gravity - always attractive and gets weaker as particles move apart.
Now forces work through coupling to a "force field". They do this by the exchange of particles. If the particle has mass, then the distance the force can work over is finite. The strong and weak forces work this way. Electromagnetic force uses massless photons, and gravity uses particles callex gravitons. I like the analogy of two rugby players passing to keep in contact as they run up the pitch.
The basic principle of forces coupling particles is however the same. As energy increases, the forces begin to work the same way. This is called "unification". The first unification was by Maxwell who showed electricty and magnetism were really the same force. Next came the weak force, which is propagated by heavy particles called W and Z bosons. This was in the 1980s. Going higher in energy, the next unification would be the strong force. The Higgs boson is the particle that would carry this force, if we see it.
Now back to gravity. Although fantastically weak, it is the bad boy of the four because it is universally attractive. Further unification of tbis very uncoupled force via the graviton would require much much higher energy (we won't be making that in any millenia soon). Superstring theory is one attempt to unify gravity with the other four and account for it's odd behaviour. Another approach is the quantum gravity, that uses an approach more akin to general relativity and the warping of the field carried by gravitons.
I don't play the drums, but before discovering Biology, I was a Professional Theoretical Physicist...
At last someone who knows what he is on about.
Maybe I think
Probably be the end of the thread now! And I was so enjoying not having a clue about WTF anyone was going on about! 
djaustin makes a good post but it still doesn't explain WHY any of it happens, just how...
Well, the "why" gets a bit metaphysical, or even religious if you're that way inclined. Really, it's because the universe is built that way. Then it's personal preference whether you believe in the weak or strong anthropic principle. The weak anthropic principle says, simply, that the universe is the way it is because if it were otherwise then we wouldn't be around to see it. The strong says that the universe was made for us to observe it.
Here's a anology for gravity
1. Imagine a square rubber tile - thats pinned in all four corners. This is Space and Time. Meaning that were you to be driving a little toy car across the rubber tile, it's takes 'Time' to go from one corner to another. By virtue of the joutney, you also move in Space too.
2. Without over-complicating it, your position on the tile (in your toy car) is always relative to other positions. Ie your view from your part of the rubber tile is currently different to that of another part of the tile. This is important to remember when the Theory of Relativity is discussed.
3. Now imagine a big iron ball dropped into the middle of the rubber tile. You can imagine the tile bending quite severely can't you? This is gravity. The effect of large mass in the space-time continuum.
4. To test this theory, now imagine driving your toy car past the iron ball. Clearly towards the outside of the rubber tile, the effect of the bend or 'gravity' is quite minimal.
5. But the closer you drive toward the iron ball, the greater the distortion of the tile and the 'greater the gravitational pull'
6. Now imagine that we dont have a single tile but we have an infinite amount - making a 3D space and time continuum.
7. The analogy of a large planet in space makes sense - the bigger the mass the bigger the gravitational field
8. Now imagine a super dense star that's collapsed in upon itself. It's so heavy it's become a incredible gravitational pull
9. Now imagine that the super dense star is sooooo heavy that our 'rubber' tile is so distorted that the corners have folded in towards each other - and may even touch!
10. Now imagine that our iron ball was soooo heavy that it ripped the rubber tile and fell through? Does this suggest alternative dimensions on the other side of conventional space?
YOU'RE ALL WRONG!
Brian Cox played keyboard in D:ream.
*Leaves thread, having made a positive contribution*
Now if you could effect our Relativity - by bending space/time with energy (e=mc2) you might be able to not only move huge vast interstellar distances in no time at all, but to perhaps move in Time too
Remember - if every position in the space time continuum is 'relative' in both space and time, it figures that portals or tears might be created by incredible explosions - like the ones being developed in CERN when particles are being driven together at incredible speeds
This is why there were scientists who genuinely felt that a blackhole might have been unleashed under Switzerland last year 
Sorry mol. Why isn't really the realm of Physics. The observation that the universe seems to conform to some ordered laws, albeit sometimes hard to understand laws, is really the realm of metaphysics. You might like to look up anthropomorphic principle, an unsatisfying circular argument about the role of the observer (it's that way because we are here to see it that way), or the many worlds interpretation of quantum mechanics, which I like, but does assume uniformity of laws across universes.
I know about the anthropic principle, and it is a way of answering some questions like how come our planet is exactly like the right distance from the sun etc. I do however think why is a question for Physics. However when you get very fundamental that is rather hard to think about.
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