EOSC 310 CHAPTER 2

radiation

- All objects emit radiation - The wavelength and intensity of radiation vary with temperature - If the temperature gets hot enough, some radiation will enter the visible part of the electromagnetic spectrum

Evidence of the Big Bang

Red Shift - shows that distant galaxies are speeding away from ours and is evidence of an expanding universe - cosmic background radiation

Red shift

the dark bands or "absorption lines" on the Fraunhofer spectrum that shift towards red on the spectrum, meaning that galaxies that have red shift are moving farther away from us (and that the universe is expanding)

recessional velocity

the velocity in which the galaxy is receding, calculated from red shift from electromagnetic radiation

Aftermath of the Big Bang

- As space expanded, the universe cooled and matter formed - One second after the Big Bang, the universe was filled with neutrons, protons, electrons, anti-electrons, photons and neutrinos; - During the first three minutes of the universe, the light elements were born during a process known as Big Bang nucleosynthesis - for the first 100,000 years the only two elements were hydrogen and helium (10:1); the objects that are farthest from us are also moving away from us the fastest.

dark energy

- It has the opposite effect of what we perceive as matter and energy and exerts an expanding force on the universe - theorized to make up 70% of the universe

How do astronomers measure distances in the universe?

- Triangulation, only for nearby stars in our galaxy - Size and lumonosity - Standard candles - astronomical object with a known luminosity

Discuss the size and age of the universe

- age: 13.7 billion years old - size: the universe is constantly expanding with galaxies moving away from us

What did Edwin Hubble discover?

- discovered that the farther away galaxies are, the faster they move away - found a linear relationship between recession velocity and distance (Hubble's Law!) - used the velocity distance relationship to calculate the age of the Universe.

dark matter

- physicists are not sure what it is, but know what it isn't - makes up about 6x as much mass as normal matter - makes up around 23% of the universe

blackbody radiation

- the ubiquitous background radiation of the universe - used to estimate the temperature of distant objects

Show how velocity and distance are correlated and explain how we know the galaxies were at the same location 13.7 billion years ago, before the Big Bang.

Using a plot of distance from our galaxy versus recession velocity, you would take the slope of the straight line that captures the linear trend in the data to determine the time since the galaxies started moving away from each other.