Transcript The universe - Villanova University

The universe
Doesn’t get any better than that,
does it??
The Big Bang
Roughly 15 billion years ago, the universe
began with a huge explosion out of what is
called a singularity.
What came before?
Oscillating universe(s)?
Time and Temperature

Up to 1 microsecond, we have quarks,
gluons, electrons, neutrinos, photons.

After 5 seconds, Temperature = 1 billion
Kelvins, relatively “cool” → no more
isolated quarks, just electrons, neutrinos,
photons, etc.

Protons, Neutrons, and some elements start to
form by about 4 minutes, including Hydrogen,
Helium, and Deuterium

Universe still “too dense” to allow photons to
move far. Universe can’t be “seen”.

After 1 million years, temperature around 3000
K, universe is now sufficiently rare to allow a lot
of atoms to form, which they do. Photons can
now move large distances. Universe is “visible”.
Imperfections give structure

You’d expect after the big bang that the universe
would be isotropic; it isn’t.
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Those differences determine galaxies, stars, etc.
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Where did they come from?

Matter and antimatter?
Young Stars

The Hydrogen in the early universe coalesced to
form stars.
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Powering the stars is nuclear fusion.

Balance between nuclear fusion pressure and
gravitational pressure (10 billion K).
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Some stars collapse and explode, creating
heavier elements.
Heavy elements

Stuff like iron, nickel, uranium comes from
the destruction (explosion) of stars.

These elements help to form “new” stars,
which are still mostly hydrogen.

These newer stars live and die, giving
even more heavy elements.
Our star, the sun

Mostly Hydrogen, a little Helium, some
heavier stuff like Carbon.

Born about 5 billion years ago, live another
5 billion (give or take).
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Less and less fuel, core contracts, outer
layers expand. “Nova” and planetary
nebula, leaving a white dwarf behind.
Star death
Our sun → white dwarf plus extra stuff
Sun will expand into a red giant, larger than
Earth’s orbit.
White dwarf turns into black dwarf (heat
death)
Bigger stars?

Neutron stars, also called “pulsars”

Rotating stars with a density close to the
density of the nucleus.

“Little Green Men”

What about even bigger stars???
Black Holes
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Heavier stars collapse into singularity
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Escape speed greater than speed of light
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Event Horizon and tidal forces
Larger Scales: Galaxies
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Elliptical, Spiral, and Irregular
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Dark Matter
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Distances: redshifts (Doppler shift) gives
the Hubble law.
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“Walls” of galaxies