Class 3Class 3

The UniverseThe UniverseAnd everything else…And everything else…

• Are there explosions in space?Are there explosions in space?• If, so, what do you think causes If, so, what do you think causes

them?them?

• Universe: Universe: Everything Everything that exists anywhere.that exists anywhere.

• Observable Observable Universe: Universe: The part of The part of the Universe that we the Universe that we can see using the can see using the largest telescopes.largest telescopes.

• Most scientists think Most scientists think the whole universe is the whole universe is much bigger than the much bigger than the observable universe.observable universe.

• Static: Static: inactive: inactive: not in physical not in physical motionmotion

• Theory: Theory: The The Universe does not Universe does not grow or shrink over grow or shrink over time and has time and has always existed.always existed.

• Originally favored Originally favored by Einstein.by Einstein.

Expanding UniverseExpanding Universe• As early as 1918 As early as 1918

though astronomers though astronomers noticed that parts of noticed that parts of the universe seemed to the universe seemed to be moving away from be moving away from us.us.

• In 1929 Edward Hubble In 1929 Edward Hubble came up with a formula came up with a formula the showed that the the showed that the farther some was away farther some was away from Earth, the faster it from Earth, the faster it was moving away.was moving away.

• The doppler effect is a change in The doppler effect is a change in frequency of a wave because the frequency of a wave because the source is moving.source is moving.

• A source moving away lengthens the A source moving away lengthens the wave.wave.

• A source moving closer shortens the A source moving closer shortens the wave.wave.

• The sound is higher pitched as the The sound is higher pitched as the vehicle approaches you and lower as vehicle approaches you and lower as it goes away.it goes away.

• Hubble saw that the Hubble saw that the further away an object further away an object was in the universe. was in the universe. The more its light was The more its light was shifted toward the red shifted toward the red end of the spectrum.end of the spectrum.

• Scientist could now Scientist could now tell how far away tell how far away something was just by something was just by checking its red-shift.checking its red-shift.

• If everything is If everything is expanding, some expanding, some scientists suggested scientists suggested that every at some that every at some early time must early time must been altogether.been altogether.

• Then suddenly Then suddenly started expanding, started expanding, something that something that continues even continues even today.today.

• Expansion of the universe.Expansion of the universe.

• Many scientists Many scientists were skeptical of were skeptical of the “big bang” until the “big bang” until two scientists in two scientists in 1965 stumbled 1965 stumbled across a mysterious across a mysterious level of background level of background radiation while radiation while testing a new radio testing a new radio telescope.telescope.

• This was the This was the leftover heat from leftover heat from the “big bang.”the “big bang.”

Age of the UniverseAge of the Universe

• Best Best estimate is estimate is between between 13.5 and 14 13.5 and 14 billion years billion years old.old.

• After about 300 After about 300 million years after million years after the “Big Bang” the “Big Bang” gravity started to gravity started to pull the hydrogen pull the hydrogen gas together. If a gas together. If a large enough ball large enough ball of hydrogen formed of hydrogen formed it would ignite into it would ignite into a star though a star though fusion.fusion.

• Just like people, Just like people, stars are born and stars are born and die.die.

• What happens to a star when it dies?What happens to a star when it dies?

• A medium sized star A medium sized star like the sun will burn like the sun will burn through all of its through all of its core hydrogen (in core hydrogen (in about 9.5 billion about 9.5 billion years), then shift to years), then shift to fusion in the outer fusion in the outer shell.shell.

• This will cause the This will cause the Sun to grow to a Sun to grow to a “Red Giant” star in “Red Giant” star in about 5 billion years.about 5 billion years.

• The sun will The sun will eventually shed its eventually shed its outer layers and end outer layers and end its life as a white its life as a white dwarf star.dwarf star.

• This will happen to 99 This will happen to 99 percent of all stars.percent of all stars.

• The outer layers will The outer layers will form a planetary form a planetary nebula.nebula.

• Has a diameter that is the same as Has a diameter that is the same as Saturn’s orbit.Saturn’s orbit.

• If a star is a large If a star is a large “blue supergiant,” “blue supergiant,” like Rigel, it will like Rigel, it will end its life with a end its life with a giant explosion giant explosion called a supernova.called a supernova.

• The remains of the The remains of the star will be crushed star will be crushed down into a down into a “blackhole”“blackhole”

• A black hole is an A black hole is an object with such object with such high gravity that high gravity that when anything when anything gets too close, it gets too close, it cannot escape cannot escape and will be and will be pulled in. This pulled in. This even includes even includes light.light.

• Scientists Scientists believe there believe there are super are super massive black massive black holes (perhaps a holes (perhaps a billion times the billion times the mass of the sun) mass of the sun) at the center of at the center of most galaxies, most galaxies, including the including the Milky Way.Milky Way.

• At about the same time the first stars At about the same time the first stars lit up. Large formation of matter lit up. Large formation of matter were pulled together to form were pulled together to form galaxies.galaxies.

• A galaxy is a A galaxy is a collection of collection of matter including matter including hydrogen gas, hydrogen gas, dust and stars. A dust and stars. A large galaxy can large galaxy can include a trillion include a trillion stars. (That’s stars. (That’s 1,000,000,000,001,000,000,000,000 stars)0 stars)

• We live in the We live in the Milky Way Milky Way GalaxyGalaxy..

• We can see the We can see the edge of it in the edge of it in the sky. It appears as sky. It appears as bright path called bright path called the “Milky Way.”the “Milky Way.”

Milky Way GalaxyMilky Way Galaxy• Has about 400 billion stars.Has about 400 billion stars.

• Galaxies are pulled Galaxies are pulled into groups by into groups by gravity. Our local gravity. Our local group contains 30 group contains 30 galaxies including galaxies including two other spirals.two other spirals.

• Galaxy groups are Galaxy groups are also part of also part of “superclusters” of “superclusters” of galaxies. We live in galaxies. We live in the Virgo Super the Virgo Super cluster which cluster which contains about 100 contains about 100 groups.groups.

• For decades For decades scientists wondered scientists wondered if the universe if the universe would continue to would continue to slowly expand slowly expand forever, or if there forever, or if there was enough gravity was enough gravity to pull it back to pull it back together into a “Big together into a “Big Crunch.”Crunch.”

• Most recent Most recent calculations calculations surprised surprised scientists as scientists as neither was the neither was the case. The case. The expansion is expansion is accelerating. accelerating.

• This leads some This leads some to speculate to speculate about a “Big Rip.”about a “Big Rip.”

• We will have a few minutes for you to We will have a few minutes for you to work on your presentations then we work on your presentations then we will start.will start.