Month: October 2020

Thesis off-cuts: how special is our place in the Universe?

On By Natalie HoggIn PhD, ScienceLeave a comment

Thanks to many hundreds of people making dedicated observations of the sky over many decades, we know that the majority of our Universe is comprised of two substances: dark matter and dark energy. Dark matter is an unknown type of matter, referred to as "dark" because it does not interact electromagnetically, meaning that it doesn't …

Continue reading Thesis off-cuts: how special is our place in the Universe?

The distance duality relation

On By Natalie HoggIn PhD, ScienceLeave a comment

The distance duality relation tells us how, assuming that photons propagate on null geodesics in a pseudo-Riemannian spacetime and that their number is conserved, luminosity and angular diameter distances are related, via where dL is the luminosity distance, dA the angular diameter distance and z the redshift. This relation was introduced by Etherington in 1933, …

Continue reading The distance duality relation