Taking account of the earth's orbit of the sun, the sun's orbit of the galaxy and the galaxy's speed through the universe, how fast are we all travelling through space? and, as relativity tells us that the speed we travel affects time, what would happen if we stopped?

If we consider thermodynamics and its law that heat travels from hot to cold, I was curious as to how or what occurs when sunlight is travelling to Earth. The gap between the Sun and the Earth is effectively a vacuum and also the low pressure at high altitudes mean that it is very cold, surely the heat should be dispersed by then and not reach sea level.

I would like to know how we still manage to feel the heat.

Thank you

It seems to be generally assumed that there is an extremely high pressure at the centre of a planet such as the Earth.  I don’t think this can be correct, surely there should be no pressure at all, a void.  Could someone please explain why my reasoning is wrong?Pressure is due to the weight of (for example) air or water pressing down, due to it’s mass and gravitational attraction.  Ascending, the weight of material above decreases, so decreasing the pressure.  Pressure rises (at first) when descending from the surface as the weight of the column of material above increases.But at the planetary core (or more correctly, the true centre of gravity) there can be no net gravitational force because the attractive forces of every particle in the planet (and indeed beyond the planet) cancel.  It is a zero-gravity place.  As one moves from the core, out of any void and towards the surface, the amount of material directly above becomes less and that below (through the core to the diametrically opposite surface) increases, so that a net gravitational pull towards the core develops, reaching a maximum at the surface.  There will be an intermediate point between the core and the surface where the weight of material above is at a maximum (due to net gravitational pull and depth of material above) and here the pressure will be at a maximum, decreasing both upwards and downwards.  At the exact centre, without any attractive force, there can be no pressure if the planet can be considered as an unrestrained system (and with fluid magma and tectonic movement this is surely the case, the planet is flexible).  It is very hot  in the centre, so particles in the vicinity will be thermally mobile and drawn to areas of gravitational pull, away from the very centre.  This effect will keep the core empty; to what extent I wouldn’t wish to speculate, but I should guess not a major part of the entire globe.  This low pressure and low density volume at the centre may be noticeable, and I wonder if this could explain some of the anomalous observations about planetary and solar cores.

If correct, this effect should be seen in many large agglomerations of fluid particles such as stars, or even a Galaxy.  (But NOT the entire Universe – it is expanding).  Perhaps there is more matter located towards the galactic periphery than in the centre, and this might help explain the anomalous galactic rotational speeds which have led to the postulation of dark matter.  Is the concept of dark matter actually needed if the galaxies have a different mass distribution to that usually assumed with gravitational pull a maximum somewhat away from the centre?However, I do wonder how the black holes that seem to inhabit the centre of many galaxies can remain ‘locked’ into position in the centre of an otherwise gravitationally neutral place.I feel that this whole concept is all too simple and somewhere I must have made a mistake, so I would really appreciate someone explaining why I am wrong.

We all know (in the Northern Hemisphere) the days get shorter as we approach the end of December.  The days get longer as we approach June.  But why don't the days get shorter and longer at a uniform rate? 

Example: In September the day length varies by nearly 4 minutes a day. But in December the rate of change is only 1 to 2 minutes.  Around 20th December the change is only about 10 seconds.  Why is this?

If you want to 'play' with this, take a look at: http://www.timeanddate.com/worldclock/astronomy.html?n=136&month=12&year=2010&obj=sun&afl=-11&day=1

I have heard that the very cold temperatures we are experiecing can cause diesel to freeze. I heard that the temperature is around -12 degrees, is this true?

I have thought of this question as this can effect everybody.

I've been told that temperature can be explained by how fast molecules are moving around, the higher the temperature the faster they move and the more kinetic energy they have.  This is however confusing as different molecules will move around at different paces and will exist as different states at the same temperature i.e. at room temperature oxygen will be a gas whereas molecules in a chair will be solid.

 Therefore how do you define temperature?

Long-delayed-echoes are radio signals that return to the transmitting site after several seconds. Recently on around 7000kHz a German radio amateur heard his own signal coming back about 45 seconds after he had finished transmitting using morse code.

It normally takes around 1/7th second (0.14s) for a radio signal to go right round the Earth bouncing between the ionosphere and the planet to get back to where it started.

Did the signals just go round the world a few hundred times? The recording doesn't show them. You can hear them as .wav files here: http://brogl.net/Audio/

Also I'm interested in how they were audible after travelling for such a long distance. Was there some sort of focussing going on?

Say there was a tunnel that went through the centre of the Earth that came out on the exact opposite side to the entrance. If you jumped down it, would you have the momentum to fly out of the other side, or would you be pulled towards the Earth's centre of mass and be crushed? This is assuming of course that the person will not burn :P

I've seen the animations of icy meteorites filling the primordial oceans with (presumably) pure water, but rocks are not naturally 'salty', in a potato crisp sense, and extracted salt is from dried-out deposits originally from seawater. And why Sodium Chloride in particular ? 

Iron will attract magnetic lines of force by making their path through the space easier.  Is there any material which will prevent or block the passage of those lines of force?