The Fate of Humanity According to Astro 490
- Slides: 35
The Fate of Humanity… According to Astro 490…
Population
Population
Life Expectancy
Life Expectancy
Observations and Experiments 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 1. We observe phenomena in the natural world, and science strives to make sense of it! 2. A Hypothesis is formed – questions that we wish to answer about a particular phenomenon. 3. Predictions are made based on a hypothesis. 4. We experiment, experiment make observations, and draw conclusions. The Hypothesis is accepted or rejected.
Einstein’s General Theory of Relativity (GR)
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
Letter from Einstein to Hale
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 center of 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 forward that these objects were rotating neutron stars (Tommy Gold) • Anthony Hewish awarded the Nobel Prize for the discovery!
Discovery of the CMB • Two models existed – the steady state theory, theory and 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 universe was much smaller in the past. The universe emerged from a hot, dense state – The Big Bang.
COBE CMB
WMAP CMB
Neutrinos • The three neutrino types (electron, , and ) interact 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?
Neutrinos
Bigger, Better Telescopes
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.
Next Generation Space Telescope
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
Cosmology – the need to move further out
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
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