between3and26characterslon

C is the exact number not just an arbitrarily large number, E=mc2 didn't just appear out of nowhere it was derived from previous knowledge. Take a look here http://www.adamauton.com/warp/emc2.html

Is CMBR something we see at a distance or is it the sum of what we see between here and the edge of the observable universe (less matter of course). That diagram would appear to show it as a wall.

As fusion occurs in the star it makes ever heavier elements up untill the point iron is made. Iron either does not fuse under stella conditions or does not release energy when it fuses, I think it's the former. As the mass of iron at the stars core increases and its fuel gets used up the star will start to cool. As it cools it gets more dense and when the density reaches a certain point it will collapse under its own gravity (probably to a white dwarf). The collapse of the core releases energy which blows the outer layers of the star off in what is a supernova. (I've just gone back and read the other post before adding my reply and realised I've just repeated what steevey said, though not in as much detail.)

simples

There is so little friction on wet glossy lines that bikes can get trapped on them and end up going in whatever direction the lines go in, can't accelerate, can't brake and can't steer.

We are all familiar with wavelength and frequency but are we really? What is a photon doing that gives it these qualities. I remember when I was at school seeing light represented as a squiggly line on a blackboard. I never gave it much thought, just accepted it, but does light actually bob up and down in a wave as it travels along? This just recently struck me as absurd, surely light would pulsate equally in all directions and the squiggly line is a 2D reprensentation of its 3D nature. Then I wondered how polarising lenses work and I'm back at squiggly lines again (stop me if I'm getting too technical). So what is frequency and wavelength?

The frequency of the light emitted from the space craft is the same in all directions (as if the craft were stationary and the observers moving). The frequency of the light recieved by the observers would differ due to Dopler effect. The light would be equally redshifted in all directions due to time dilation and then, due to Dopler effect, blue shifted in front of the craft and red shifted further behind the craft.

"(stationary to the Cosmos)" first off there is no such thing as stationary to the Cosmos, they are stationary within a frame of reference (read about relativity principle for further explanation) 2nd "The point here is that to the observer in front, the EM radiation would be redshifted first due to time dilation, then blueshifted because of the Doppler effect" If red shift is due also to Doppler then the problem goes away.

Krauss gave a lecture where he said that if you treat mass as positive energy and gravity as negative energy they would cancell each other out and the net energy of the universe would be zero. He also said the if you take a region of space and remove all particles from it so that there is nothing left, NOTHING left then what you see on the micro scale is particles breifly appearing and disappearing again and so nothing isn't nothing it is something. Therefore, he said, the universe could come from nothing. Two things strike me with this 1) the nothing before TBB and the nothing after TBB are two different nothings, they aren't comparable and 2) if the universe did come from nothing why is it finite, why does it have finite mass and energy if that mass and energy came from nothing? getting back to the OP and dragonstar57's answer; was energy created during TBB or did it exist before TBB if so where did it exist?

If the rate of expansion was constant for all time the diagram would be a cylinder. The steepness of the outer lines tells you the rate of expansion, the steepest lines on the diagram are during inflation where the rate of expansion was at its greatest. The distance from leaft to right tells you the age of the universe. The diagram tells you the rate of expansion abruptly levelled (almost) off after inflation before entering the 'dark ages', the rate was then fairly constant and the rate is increasing as you get nearer the present.

The relativity principle is Galelean not Einsteinian, it applies to Galelean frames of referrence. That is frames which have uniform rectilinear translation relative to each other, the frame you are in is stationary as far as you are concerned and all others are moving but this is true for all frames and that makes observations objective.

Have a read /reed/ here and once you've read /red/ it it might answer your question http://www.einstein-online.info/spotlights/changing_places

What would a singularity look like from the inside?

Of course, should have thought it through before I asked.

For no other reason than to add to the confusion, if the universe is 14bn years old and the light from the most distant was emitted 14bn years ago then the light would not have had any distance to travel becasue at that time objects were close together. So if we are observing light that is 14bn years old it must have been at least 14bn LY away when it was emitted??? Hope that helps

Does this mean as the universe cools down it looses mass?

Frames of reference; If you're on a train are you moving or not? If the train was running on perfectly flat and smooth rails, was not accelerating or braking, was not turning and the windows were covered you would not know you were moving. If you put something on the table in front of you it would stay there and not move even though the train is speeding along the tracks so this object is moving relative to the ground outside but stationary relative to the train. The ground outside is one frame of refference and inside the train is another frame of refference so when you talk about the velocity of an object you have to relate it to a frame of refference. A frame of refference is an imaginary grid consisting of x, y and z coordinates which you use to describe the motion of objects. That Diagram; Imagine you are in a box floating in space so there is no gravity, if you are either not moving, or moving at constant speed in a straight line you will float freely in this box and have no concept of up or down. If there was a tiny hole in this box (you're in a space suit) with a lazer shining through it the laser light would describe a straight line to the other side of the box. Rule 1; light travells in straight lines If a space ship came along an gave this box a shove it would accelerate momentarily and then reach a constant speed again. You inside the box would see one of the sides approaching and you would bump into it. It would in turn shove you and so now you have the same speed as the box again and are back to floating around inside it. If the space ship were to hook up to the box and give it a tow and accelerate at a constant rate one of the sides of the box would come up to meet you but his time you would feel it constantly pushing you and you would be able to stand up on what you might now consider the floor. Rule 2; being stationary in a gravitational field or being in an accelerating box are the same thing. If a laser were to shine through the tiny hole in an accelerating box the light would describe not a straight line but a curve accross the box before hitting the other side. So now we have a conflict light travels in straigt lines but gravity bends it even though light does not have mass so gravity can not bend it. The Answer; Light travels in straight lines relative to spacetime, gravity bends spacetime and therefore light appears to bend. The diagram shows how mass warps spacetime and how it would affect the trajectory of anything passing through it. It's a 2d plane of a 3d distortion in 4d space, it's a bit like taking a cross section so you can see what's going on. no equations and the simplest way I can

but you're still thinking of the universe as being something spherical expanding into space whereas it's something of unknown shape that is an expansion of space. Imagine this; picture a circle with a point at its centre, this represents the centre of the universe and the edge of the observable universe. now stretch this into a cylinder with an axis, the centre is no longer a point but a line bend the ends round so they meet and you have a torus stretch this torus top and bottom so that it starts to look like a cylinder again and the 'centre' is now 2 dimensional (maybe even 3 dimensional) with imaginary lines connecting the torus to the centre hold the centre still and rotate torus around it (ie looking directly above a doughnut turn it clockwise) the lines connecting the centre of the torus to the outside are stretched. you can now imagine that the elongation of the torus into a cylidrical shape is the direction of time and the stretching of the lines connecting points is the expansion of space. I'm not in any way saying that the above is correct just that if you think about it you can imagine something that makes some sort of sense. Two ice skaters skate past each other and as they pass they grab hold of each other they will naturally spin

This is quite interesting and Krauss talks about the cosmological constant Susskind (in those other lectures) says that there is a small repulsive component to gravity and whereas gravity follows the 1/r2 rule the repulsive component is constant albeit miniscule. This means that eventually you are far enough away from a mass that its gravitational force of attraction is less than the repulsive force. BTW not sure I understand the ball analogy, I don't think it's correct to think of the universe as a ball, the over simplification leads to problems. Also gravity is stronger below us than it is at the sides (that is it has direction) that's why we stick to the planet. Maybe I'm wrong but there seems to be the suggestion that there is a universal ground which everything is being pulled towards. If that were the case then on a rotating and orbiting planet we should fall of it.

Here's where I heard it but there is a lot more to it than I got round to watching http:// www.youtube.com/watch?v=s8UrYIZhm60&p=6C8BDEEBA6BDC78D&playnext=1 Copy and paste into your address bar and remove the spaces, I've done this because there are 12 lectures in this series and this is lecture 2. He says in the first few minutes that the repulsive force is a component of gravity.

I have just been watching something to do with this. Hawking initially said that information was destroyed Susskind (and others) said that the information was not lost, as it would violate a fundamental principle of physics, rather it was smeared over the surface of the event horizon Hawking eventually admitted (after 30 years) that he was wrong, and the others were wrong too, but now believes that the information is retained in universes where the black hole does not exist. I don't think there is any proof for this yet though.

I know what you mean but like you that is because of my lack of knowledge.

I watched a lecture by Leonard Susskind on youtube, do a search on relativity on youtube and you will find a series of 8 lectures of about 1h30 each, in it he said, "the expansion was due to a property of gravity, but we'll come to that later" I never got that far though. The maths is too complicated for me to follow so I'm trying to learn a bit first. Also Krauss (youtube him) explains a bit but yeah I had the same thought myself, gravity causes the expansion of the universe.

Isn't 'all trajectories' a bit confusing, there's only one trajectory which either includes all points or some points. You can imagine your journey would describe a huge circle as you travel around the universe and you end up back where you started, you would exist at all points on a line. Alternatively you can imagine travelling through all points in the universe, and therefore existing at all points, before returning to the point you started. I only ask because I heard that there is nothing in physics that forbids time travel but if you travelled in time you, and all the atoms you are made of, would exist in two places at the same time.

yep Hopefully you had heard that before rather than working it out, it's a test to see if someone is a psychopath.