D5 Further cosmology

Any large section of the universe will be similar to any other large section.

• Homogeneous

• Isotropic

What can be observed by looking in any one direction from anywhere in the universe is similar to what can be seen by looking in any other direction from the same place.

• Homogeneous

• Isotropic

The universe has no edge and no center.

•  Isotropy

• Isotropic

The source of radiation and the observer could be moving apart from each other in unchanging space.

• Doppler effect

• Cosmological red-shift

The space between the source and the observer has expanded between the time when the radiation was emitted and the time when it was received.

• Doppler effect

• Cosmological red-shift

Occurs as a result of radiation moving out of gravitational fields.

• Gravitational red-shift

• Cosmological red-shift

A variable that would just stop the expansion of the universe after an infinite time. The current theoretical value is about six hydrogen atoms per cubic meter.

• Critical density

• Parameter density

Actual values of mass in galaxies.

• Green curve

• Orange curve

There may be more mass in galaxies that can be observed. This mass which cannot be observed directly is in an outer ring of a galaxy called a ... .

• Dark matter halo

• Dark energy

Possible future for the universe: This suggests that the density of the universe is close to the critical density and that the universe is expanding. The expansion of the universe has been accelerating. This explanation requires dark energy. 𝜌 = 𝜌c

• Red

• Green