In a vacuum, virtual particles are constantly appearing and annihilating, is this also going on inside my vacuum cleaner?

If the universe can expand faster than c, can it contact faster than c? would this be observable?

If an expanding universe undergoes inflation, would a contacting universe undergo deflation?

If I've understood this, at least to some extent, everything always travells at the speed of light (or c to be more precise), provided you take account of the speed of travel through time as well as space, something at a fixed point in space travels through time at c and something travelling through space at c ceases to travel through time? The earth, sun etc. are not fixed points in space, they move through space as does our galaxy as well.  My question is really where this puts us on a scale from a fixed point in space too something travelling through space at c, and how much of an effect do we experience (I realise we would be unaware of it), compared to something not moving through space at all.  If I were to look out into deep space and by some weird coalescence of improbabilities were to see a person standing at a fixed point, unmoving in space, how much faster would they appear to age (travel through time) from my perspective (still traveling at normal earth speeds) or would this be the case at all? Many thanks,

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?

I was watching a programme on equations the other night and Einstein's equation for the equivalence of mass and energy was described, E=mc2.

I understand that there is an equivalence between mass and energy and they can be converted.

However, my question is 'why does the equation depend on the speed of light and not just some arbitrary constant'?

Einstein knew that the constant was the square of speed of light well before practical experiment so there must be some logic to it.

Many thanks

There are many predictions made by scientists about the fate of the universe. One of them is the "Big Rip". So the question is, what will happen after the "Big Rip"?

So here's what I think will happen, feel free to correct me if I'm wrong.

1. The universe is expanding and it has been known and proven. If it continues at this rate, every matter inside the universe will be ripped apart.

2. But when the universe reaches it's "elastic limit" and can go no further, it will collapse with great force back into the centre of the universe.

3. When this happens, everything in the universe will shrink back into the size of an electron(or maybe even smaller) with an "infinite" amount of density. This can soon turn into another "Big Bang".

4. And therefore the steps repeat itself when there is another Big Bang.

Example: Imagine a coil of spring. If you compress it very tightly, it will repel back at you with great force. If it is pulled very strongly, it will pull itself back to it's normal shape with great force.

I believe that the universe is like a spring, but the only thing is that it doesn't have any definite shape.

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