Oct. 4 – 2B03 04/10/2011 9:24:00 AM
Novel Prize – evidence for the acceleration of the expansion of the universe.
Used standard candles.
Special relativity – associated w/ very fast speeds.
More waves per unit time – blueshift
Less waves per unit time – redshift
Speed stays constant, what changes is wavelength.
Let’s Look at Small Things
In quantum mechanics, we will look deeper into the atom. Quarks
are the units that made protons and neutrons.
Momentum (p) = mv
o Falls apart in quantum world.
Newton’s Laws breaking down at extreme cases (moving incredibly
fast). Also, at really small scales (atom’s size).
Blackbody radiation – main point – hot objects glow w/ a spectrum
of colours that depend only on their temperature.
o Colour depends only on temperature.
o From colour you see, you can work out temperature.
o Stars – excellent blackbodies. You can tell from its colour
what temperature it is.
o If light comes in packets of quanta, you can understand the
Einstein also made huge contributions to quantum mechanics.
Built on Planck’s ideas. People thought light was continuous wave –
but it was discovered that light comes in little particles. He could
now describe the photoelectric effect. We thought that in order to move stuff around, we needed momentum.
SOme mass and some velocity. But light has no mass, photons got none.
Our idea of momentum for light must not be correct.
First evidence that classical physics was breaking down. P=mv does
not work for light and subatomic particles.
Duality – light behaves as a wave and a particle.
o Subatomic particles can also behave like both particles and
Energy realized – E=hf
As frequency increases, we have more energy. As f goes up, E goes
Redshifting – longer wavelength – energy smaller (photons lose
Reverse might also be true. Particles may behave as waves.