How old is the Universe?

Age of the Universe• Astrophysics suggests that ~13,700,000,000 years ago there was a big

bang. It was not so much of an explosive bang as it was an expansion of space-time itself. All matter was thus created within a few heartbeats, creating an expanding plasma of the nuclei of hydrogen, helium and a bit of lithium, the lightest of the elements.

Determining Age

• Method 1: Determine the speed and distances of other galaxies Doppler Shift

Determining Age

• Method 2: Study old globular clusters

All of the stars in a globular cluster formed at roughly the same time, thus they can serve as cosmic clocks. If a globular cluster is more than 20 million years old, then all of its hydrogen burning stars will be less massive than 10 solar masses. This implies that no individual hydrogen burning star will be more than 1000 times brighter than the Sun. If a globular cluster is more than 2 billion years old, then there will be no hydrogen-burning star more massive than 2 solar masses.The oldest globular clusters contain only stars less massive than 0.7 solar masses. These low mass stars are much dimmer than the Sun. This observation suggests that the oldest globular clusters are between 11 and 18 billion years old. The uncertainty in this estimate is due to the difficulty in determining the exact distance to a globular cluster (hence, an uncertainty in the brightness (and mass) of the stars in the cluster).

What is the Universe doing

• Expanding, Contracting, or Oscillating?

• How do we know?

• Balloon or cookie dough analogy

Hertzsprung-Russell Diagram

A star’s color depends upon its temperature.

A star’s temperature depends upon its age.

Sun: T = 6000 Kso E = 5.67 x 10-8 Watts m-2 K-4 (6000 K)4 = 7.3 x 107 Watts m-2

How old is the Earth?

•Radioisotopes

•Meteorites

•Moon rocks

What is the Earth made of?•Atmosphere?

•Crust?

•Core?

Geologic Timescale

Global Warming and Runaway Green House

• What is the Greenhouse Effect?– CO2 and H20

• How does Earth compare with Mars and Venus?

Questioning results

• Scientific Method– Question– Hypothesis– Prediction– Testing with Control– Observation

Repeat…

Face on Mars