The Big Bang! ESCI 518 Fall 2004

Origins How Do We Know? How and when did the: universe form? solar system / Earth form? Moon form? What were early Earth conditions? How Do We Know?

Origin of the Universe Big Bang occurred 15 billion years ago model for the beginning of the universe

Building a Universe - infinitely dense point not governed by our physical laws or time - all matter and energy contained in one point Einstein’s theory of relativity predicts this “smaller than a proton” time=0 state http://rainbow.ldeo.columbia.edu/courses/v1001/7.html

Building a Universe - instantaneous filling of space with all matter http://rainbow.ldeo.columbia.edu/courses/v1001/7.html

Edwin Hubble Universe is continuously expanding Galaxy’s velocity is proportional to its distance (galaxies that are twice as far from us move twice as fast) taken every galaxy the same amount of time to move from a common starting position to its current position

Hubble’s Evidence Doppler shifting - wavelength emitted by something moving away from us is shifted to a lower frequency Sound of a fire truck siren - pitch of the siren is higher as the fire truck moves towards you, and lower as it moves away from you Visible wavelengths emitted by objects moving away from us are shifted towards the red part of the visible spectrum The faster they move away from us, the more they are redshifted. Thus, redshift is a reasonable way to measure the speed of an object (this, by the way, is the principal by which radar guns measure the speed of a car or baseball) When we observe the redshift of galaxies outside our local group, every galaxy appears to be moving away from us - universe is expanding.

Evidence for Big Bang Red shift - as light from distant galaxies approach earth there is an increase of space between earth and the galaxy, which leads to wavelengths being stretched In 1964, Arno Penzias and Robert Wilson, discovered a noise of extraterrestrial origin that came from all directions at once - radiation left over from the Big Bang In June 1995, scientists detected primordial helium in the far reaches of the universe - consistent with an important aspect of the Big Bang theory that a mixture of hydrogen and helium was created at the beginning of the universe

Building a Universe 10-43 s - gravity separates from other forces - 10-28 centimeters 10-35 to 10-32 s - fundamental particles - quarks and electrons - softball 10-6 s - quarks combine into protons and neutrons - solar system 1 s - electromagnetic and weak nuclear forces separate 3 minutes - protons and neutrons combine into atomic nuclei 105 years - electrons join nuclei to make atoms; light is emitted 105-109 years - matter collapses into clouds, making galaxies and stars Light at 300,000 years Orion Nebula - http://stardate.utexas.edu/resources/ssguide/planet_form.html

When Did the Universe Form? 10 to 20 billion years ago (15) How do we know? spreading (Red Shift) know distances, rates of retreat, relative positions pervasive background radiation of 2.7°C above absolute zero afterglow of the Big Bang Shipp: Red shift - can determine composition of star, and relative movement by measuring its spectrum. Wavelengths shift toward red if moving away. Faster the velocity, more of a red shift. Wellner: wavelength shifts to the red end of the spectrum as Doppler Effect while light travels through universe (gravitational effect on photons) Hubble - universe is expanding (red shift) and things farther away are moving away faster (greater red shift) Differences in age b/c we don’t know the size of the universe. Doppler effect - shift in wavelength - light and sound Compressed as it approaches - higher pitched an shorter waved Stretched as it leaves - lower pitch, longer wave Orion Nebula - http://stardate.utexas.edu/resources/ssguide/planet_form.html

How old is the universe? Speed x time = distance (distance of a particular galaxy) / (that galaxy’s velocity) = (time) or 4.6 x 10^26 cm / 1 x 10^9 cm/sec = 4.6 x 10^17 sec ~ 15 billion years

Features of Our Solar System in a spiral arm of the Milky Way Galaxy Sun 9 planets 101 known moons (satellites) a tremendous number of asteroids most orbit the Sun between the orbits of Mars and Jupiter millions of comets and meteorites interplanetary dust and gases

Relative Sizes of the Sun and Planets

Solar System Configuration

Origin of Our Solar System Solar nebula theory cloud of gases and dust formed a rotating disk condensed and collapsed due to gravity forming solar nebula with an embryonic Sun surrounded by a rotating cloud

Embryonic Sun and Rotating Cloud planetesimals have formed in the inner solar system large eddies of gas and dust remain far from the protosun

The Planets Terrestrial Planets Mercury Venus Earth Mars small, composed of rock, with metal cores Jovian Planets Jupiter Saturn Uranus Neptune large, composed of hydrogen, helium, ammonia, methane, relatively small rocky cores – Pluto?