Lectures on galaxies and cosmology Astronomy II, Fall 2005 Lectures on galaxies and cosmology Dr Martin Hendry University of Glasgow, UK (Basler Chair, 2005) HENDRY@etsu.edu Tel: 94252 Brown Hall, Room 373 Office Hrs: Mon 10.30 – 11.30 Tue 14.30 – 15.30 http://www.astro.gla.ac.uk/users/martin/basler/astro2/

Cosmology: the Nature of Spacetime Olbers’ Paradox: Why is the sky dark at night?

Cosmology: the Nature of Spacetime Olbers’ Paradox: Why is the sky dark at night?

The Cosmological Principle At any time, the Universe is isotropic and homogeneous

Hubble’s Law: 1929 Distant galaxies are receding from us with a speed proportional to their distance

Hubble’s Interpretation ‘Recession of the Nebulae’ caused not by the motion of galaxies through space, but the expansion of space itself between the galaxies Cosmic scale factor increases as the Universe expands

Einstein’s General Relativity “Matter tells space how to curve, and space tells matter how to move”

In General Relativity even light is affected by the curvature of spacetime. We call this effect Gravitational Lensing GL is now routinely observed throughout the universe

Gravitational lensing observable during a total solar eclipse

Will the Universe continue to expand forever? In simple cosmological models this depends on how much matter there is in the Universe (or more precisely, what is the density of matter?) If the density is more than a critical value, the Universe will recollapse

Answer related to the curvature of the Universe

Answer related to the curvature of the Universe Positive

Answer related to the curvature of the Universe Positive Negative

Answer related to the curvature of the Universe Positive Negative Zero

We can measure this using Supernovae and the background radiation

Hubble diagram of distant supernovae We need a good standard candle, to probe the geometry of the Universe Type I Supernovae Distant SN fainter than expected. Suggests Universe expanding even faster today than in the distant past Expansion is accelerating!

What is driving the cosmic acceleration?… Dark Energy

State of the Universe – Nov 2005 Dark Energy Cold Dark Matter Atoms