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Milton Lasell Humason (August 19, 1891 – June 18, 1972) He was born in Dodge Center, Minnesota. He dropped out of school and had no formal education past the age of 14. Because he loved the mountains, and Mount Wilson in particular, he became a "mule skinner" taking materials and equipment up the mountain while Mount Wilson Observatory was being built. In 1917, after a short stint on a ranch in La Verne, he became a janitor at the Mount Wilson Observatory. Out of sheer interest, he volunteered to be a night assistant at the observatory. His technical skill and quiet manner made him a favorite on the mountain. Recognizing his talent, in 1919, George Ellery Hale made him a Mt. Wilson staff member. This was unprecedented, as Humason did not have a Ph.D., or even a high school diploma. He soon proved Hale's judgment correct, as he made several key observational discoveries. He became known as a meticulous observer, obtaining photographs and difficult spectrograms of faint galaxies. His observations played a major role in the development of physical cosmology, including assisting Edwin Hubble in formulating Hubble's law. He retired in 1957. He discovered Comet C/1961 R1 (Humason), notable for its large perihelion distance.Due to merest chance, Humason missed discovering Pluto. Eleven years before Clyde Tombaugh, Humason took a photograph in which the image of Pluto fell on a defect in the photographic plate and was not detected. Much of the work Humason performed was actually credited to Hubble, the two of whom worked together for many years

Milton Humason, Edwin Hubble, Charles St. John, Albert Michelson,Albert Einstein, W. W. Campbell, and Walter Adams.

Evidence for an expanding universe

The spectrum of hydrogen gas is the unique fingerprint of that element

Hydrogen lamp

Evidence for an expanding universe

Orion Nebula

When we see a repeat of the pattern we saw in the lab, we know hydrogen is present

Evidence for an expanding universe

We see the same repeating pattern of lines in

a galaxy, but displaced to the red

Galaxy UGC 12915

Evidence for an expanding universe

The further the galaxy, the more the shift to the red

Galaxy UGC 12508

Evidence for an expanding universe

Galaxy KUG 1750

The greater the red shift, the faster the galaxy is receding

Evidence for an expanding universe

The red shift is caused by the expansion of space.

Galaxy KUG 1217

Evidence for an expanding universe

The red shift is evidence for an expanding universe

Galaxy IRAS F09159

Cosmological Red Shift

12

=

v

c=z =

Redshift and Doppler Shift Redshift z is determined by comparing laboratory wavelength to observed wavelength

If objects are moving away from observer, light will be redshifted

Velocity of object can be determined from z

Markarian 205Quasar

NGC 4319Barred spiral galaxy

(system of billions of stars, gas, and dust)80 million light-years away

1 billion light-years away

Markarian 205Quasar

NGC 4319Barred spiral galaxy

(system of billions of stars, gas, and dust)80 million light-years away

1 billion light-years away

Foreground star inside our galaxythousands of light-years away

Distant background galaxy??? light-years away

1) Virtually all galaxies are moving away from us, e.g. they are redshifted.

2) The more distant the galaxy, the larger its redshift, that is the faster it is moving away.

Doppler shift

Standard Candle

I am sure you have been coached by friends that if you want an "A" in class, sit in the front of the lecture hall. 

Experience tells you that just sitting in front of the room does not guarantee a good grade. As you know the only place where success comes before hard work is in the dictionary.  Examination of the classroom seating chart does reveal something for us to think about regarding the Hubble data plot.

Past Does not equal Does not equalPresent Future

The Universe is…

Dynamic…not static

The stars are fossils embedded in the black strata of the night. The heavens above are a road cut we stand before that shows us the continuum of time across the eons of eternity…Larry Mascotti

Look afar and see the end from the beginning…

The Expanding Universe

…the expansion of the universe is an expansion of space not an expansion of galaxies into space …the expansion of the universe is an expansion of space not an expansion of galaxies into space …the expansion of the universe is an expansion of space not an expansion of galaxies into space

The top drawing would imply that the Universe expanded into "something" that preceded the beginning of the expansion. This "something", the condition before the event known as the Big Bang, is being theoretically explored but to date no experimental test support the condition of the "something" that came before the expansion phase of the Universe-everything we know. The expansion of the Universe is the beginning of time and space as we know it. In observing such a diagram as shown above it suggests that the observer, you, is viewing the balloon

universe from a place outside of this balloon universe. Where exactly is "outside the universe?"

The Expanding Universe

What’s the deal? Are we in a special place in the universe? Why else would everything be moving away from us?

The words “Big Bang” don’t adequately describe the expansion of the universe, which is different than an explosion from a given point in space. In an explosion, an observer sitting far from the center would see material traveling toward her. In the expanding universe, an observer at any point in the universe sees matter traveling away from her…Scott Dodelson Fermi Lab.

What do we see?

• In the past, AGN were more common.– It’s likely that most have run out of fuel

• Spiral were somewhat more common.– Less had been cannibalized

• Peculiarly shaped blue galaxies were more common.– The collisions that form ellipticals in progress?

Galaxy Evolution

• Remember that when we look into the distance we’re also looking into the past, one year ago per light year distant.

We see the Andromeda Galaxy as it was more than million years ago.

More distant galaxies we see longer ago.

Evolution of Galaxies

Image at http://www.galex.caltech.edu/media/glx2007-05f_img01.html

The Expanding Universe

In the 20s and 30s, Edwin Hubble noticed that emission lines in the spectra of spiral nebulae were consistently red shifted.– The smaller the angular size of the nebula, the

greater the red shift.– Once he measured the distance to Andromeda,

he was able to express a relationship between the measured velocity and the distance.

• V=H0d

• Added benefit, v is much easier to measure than d

The Universe

• Before Hubble– the universe was thought to

be constant.– the Milky Way was the only

known galaxy.

• Edwin Hubble was the first astronomer who– observed and identified

other galaxies.– found out the universe is

expanding.

http://www.edwinhubble.com/hubble_gallery/whirlpool_galaxy_M51.htm

What does it mean?

• In the distant past, every galaxy we can see was in one place. All matter and energy was essentially in the same place.

…it is easy to be overawed by the vision of the new astronomy. Many among us would prefer to retreat into a comfortable cloud of unknowing. But if we are truly interested in knowing who we are, then we must be brave enough to accept what our senses and our reason tell us. We must enter into the universe of galaxies and light-years, even at the risk of spiritual vertigo, and know what after all must be known…

…the pilgrimage is one that each of us must make alone, into the realm of the stars and galaxies, to the limits of the universe, to that boundary of space and time where the ultimate mystery, the known unknowable. It is a pilgrimage in the quest of the soul of the night…Chet Raymo

To an astronomer, man is nothing more than an insignificant dot in an infinite universe…

…I have often felt that, but then I realize that the insignificant dot who is man is also the astronomer…