The Fate of Humanity… According to Astro 490…
ObservationsandExperiments Testing theories that help us understand the Universe
Outline • How do we test a theory? • Classic Experiments and Observations • Einstein’s Theory of General Relativity (Light Deflection, Gravity Probe B) • Maxwell, Hertz, and Electromagnetism • Particle Physics and Quantum Mechanics and Planck • Tokamak Reactors • Medicine and Biochemistry – Watson and Crick • Astronomy • Classification of Spectra • Hubble and the expansion of the Universe • Karl Jansky and the Radio Window • Discovery of the CMB (COBE and WMAP) • Discover of Pulsars (Bell and Hewish) • The Future…To Infinity, and Beyond! • The Neutrino Problem • Bigger Better Telescopes (ALMA, SKA, LST, NGST) • Observing beyond EM Radiation – LIGO and Gravity waves
The Scientific Method • We observe phenomena in the natural world, and science strives to make sense of it! • A Hypothesis is formed – questions that we wish to answer about a particular phenomenon. • Predictions are made based on a hypothesis. • We experiment, make observations, and draw conclusions. The Hypothesis is accepted or rejected.
Deflection of Light • GR predicted that a large mass would warp space time, and deflect light passing by from a distant star. Einstein communicated this to George Hale. • The effect was measured (to 30%) and made Einstein a celebrity, but more importantly confirmed that the predictions of GR were correct! Observed 1.75’’ Actual
Gravity Probe B • Gravity Probe B will measure small changes in the spin direction of gyroscopes in orbit 400 miles over the poles
Electromagnetism • Maxwell brought together the formalism which relate electric and magnetic fields to radiation phenomena. • Heinrich Hertz experimentally verified that accelerating electric charges created low frequency electromagnetic waves (radio waves), which paved the wave for Morse code and wireless radio communication.
Nuclear Fusion • Tokamak and plasma experiments with toroidal magnetic fields are paving the way for nuclear fusion.
Particle Physics • Discovery of the W and Z particles – carriers of the weak interaction.
The Expansion of the Universe • Edwin Hubble used optical spectroscopy to measure the Doppler shift of galaxies – he found the correlation that velocity is proportional to distance. Objects further away are receding at a higher speed! • This showed that the universe was expanding, and that the nebular objects in the sky were actually distant entities separate from the Milky Way Galaxy
Radio Astronomy • Karl Jansky studied short wave radio transmission for Bell Laboratories (frequency of 20.5 MHz). His directional antenna identified static sources as nearby and distant thunderstorms, and unknown noise that repeated with a period of 23 hours and 56 minutes – it was not coming from an Earth transmission! • The radiation from coming from the constellation Sagittarius – the direction of the centerof the Milky Way galaxy.
Discovery of Pulsars • Compiling observations from a low frequency array, graduate student Jocelyn Bell noticed a periodic signal on the chart recorder. • The signal was marked ‘LGM’ for Little Green Men. • Hypothesis placed forwardthat these objects wererotating neutron stars (Tommy Gold) • Anthony Hewish awardedthe Nobel Prize for thediscovery!
Discovery of the CMB • Two models existed – the steady state theory, and the theory that the universe was expanding • The issue was settled when Penzias and Wilson discovered microwave radiation – homogeneous in every point in the sky. • This implied that the the universe was much smaller in the past. The universe emerged from a hot, dense state – The Big Bang.
Neutrinos • The three neutrino types (electron, , and ) interact via the via the weak force – they don’t interact with normal matter, and are very difficult to detect. • The questions that detectors hope to answer are • Do they have mass? • Do they have magnetic spin? • Are they their own anti-particle?
Atacama Large Millimeter Array • 64 element interferometer operating at millimeter wavelengths
Square Kilometer Array • 1 square kilometer total collecting area. • How to do it – large numbers of telescopes with small diameters, or many Arecibo sized telescopes?
Large Synoptic Survey Telescope • This telescope will help explore the temporal aspect of astronomy – Supernova, Near Earth Asteroids, etc. • Will cover larges areas of the sky and use a 3 billion pixel camera system, and generate 3,000 Gigabytes of data every night!
Cornell/Caltech Atacama Telescope • 25 meter class telescope • Will operate between the infrared and radio wavelengths (aka submillimeter)
Next Generation Space Telescope • The next stage beyond the Hubble Space Telescope. • 6 meter segmented mirror telescope in orbit at the second Lagrange Point.
Beyond E&M – Gravity Waves! • LIGO – Laser Interferometric Gravitational-Wave Observatory • Accelerating masses create gravity waves – just like accelerating charges created EM waves, but they are much more difficult to detect (one hundred-millionth the diameter of a hydrogen atom!). • You need a violent event – a supernova or the coalescence of blacks holes. • Gravity waves will cause disturbances, and will cause the laser setup to go out of phase.
LIGO • Two setups for verification of observations
What will we learn? • Firsts - Understanding the first stellar deaths – the first supernovae, the first quasars. • Pushing the envelope of the high-redshift universe – • When did the “Dark ages” end? • Gravitational Lensing • Resolving the disks of Active Galaxies • How did galaxies form? • The birth of proto-planetary systems – we will be able see the formation disks of new solar systems. • Resolving extra-solar planets