How does gravity affect our universe?

the influence is one of the parameters in the field equations. The best way to understand…

Hubble constant

Assuming a linear extension of the universe, the scale factor a(t)=D(t)/D0 of any distance D and the distance D0 at time t0 in the universe is linearly dependent on time t:

a = da/dt*t (1) with an expansion speed

da/dt = H*a (2)

The factor H is the stroke lead constant (which should be called better stroke lead parameters because it is not constant – in fact follows from a linear expansion constant expansion speed da/dt and thus H=1/t with 1 in 2), has a pole point at the Big Bang and has since then decreased, but never becomes zero.

Cosmological horizon

With the speed of light c it is now possible to define a radius rH=c/H, which is called the stroke lead radius. For D = rH, the speed v(rH) = c, i.e. theoretically, objects are removed at this distance with speed of light from us (the special theory of relativity is only applicable locally and is not violated thereby), and one might think that one can never see these objects because their light does not come against the speed of expansion, but:

1. Light directly behind rH can, once sent out, create with time within rH and ultimately reach us – the correct invoice contains an integration of the movement of co-moved coordinates and the light signal from t0 to infinite and leads here too far – also…

2. the above-mentioned assumption of the linear extension is incorrect. The expansion is subject to braking and accelerating influences (e.g. the mass density including dark matter vs. dark energy), the strength of which was not temporally constant or will be. Depending on these influences, the cosmological horizon can expand further with predominant braking and make more objects visible, or shrink and hide more objects with predominant acceleration.

For these two reasons, the cosmological horizon is not attributable to the hub radius, but at the current level somewhat behind it (about LJ 16 billion instead of LJ 13.4 billion). With further expansion of the universe and decreasing mass density, the acceleration could gain – then the stroke lead parameter would decrease to a constant value: the solution for the differential equation da/dt=const*a is then an exponential extension which finally allowed the cosmological horizon to shrink to structures directly bound by gravity, and the remainders of the association from Milky Way and NGC224 would be alone in the darkness.

Particle horizon.

But where are the farthest objects we already see, really? When their light was emitted, i.e. shortly after the universe became transparent, they were only a few million LJ away. While her light was on the way to us in space, this space moved away from us at the rate of expansion and extended the travel time of the light (and its wavelength) until the light finally arrived here; In the meantime, the objects sent out at that time have become so-called. Particle horizon (about 46 billion LJ), that is far behind the cosmological horizon.