Astrophysics and Cosmology How do we know what we know about the universe around us?

Astrophysics and Cosmology

How do we know what we know about the universe around us?


The farthest from the Earth we have been to return “direct evidence” has been Mars



The farthest from the Earth we have been to return “direct evidence” has been Mars

The rest of the universe is understood by “looking” that is, by the collection of electromagnetic waves


Tools:

Telescopes – can receive information both inside and outside of the visible window


Tools:


Most of what is in the (currently) observable is gaseous.


Tools:


Most of what is in the (currently) observable is gaseous.

Spectroscopic analysis of emission and absorption spectra most common tool


Part 3(e): Atomic Physics

Spectral Properties of IncandescenceEnergy

WavelengthBlue Red

Low Temp

High Temp



Click here to view a temperature adjustable continuous spectrum

http://webphysics.davidson.edu/alumni/MiLee/java/bb_mjl.htm

Absorption Spectrum of the Sun

Gas


Absorption Spectrum of the Sun


Moving one step closer to finding the fingerprints of life in a habitable planet beyond the solar system, astronomers have for

the first time detected carbon dioxide in the atmosphere of a planet that orbits a star other than the sun

Fall 2008

Moving one step closer to finding the fingerprints of life in a habitable planet beyond the solar system, astronomers have for

the first time detected carbon dioxide in the atmosphere of a planet that orbits a star other than the sun

Fall 2008

How on Earth do they know this??????


Heat

Emission




The Universe contains vast amount of hydrogen.

Other elements are being synthesized

Complex molecules are also being synthesized in gas clouds


A strange observation:

When spectra were first collected about the universe, there were no known fingerprints that matched what was observed.




?




It was realized that the spectra fit known elements, but that all of the wavelengths in the spectra had been “shifted” to longer wavelengths


The Red and Blue Shift





The Wavelengths are the same in all directions only if the atoms in the gas are not moving.



The Wavelengths get “squished” in the direction of motion, and “stretched” in the opposite direction.

Astrophysics and CosmologyAstrophysics and Cosmology


The Wavelengths get “squished” in the direction of motion, and “stretched” in the opposite direction.


It was further observed that ALL spectra form ALL deep space objects were shifted toward the red, ie, longer wavelengths

The implications is that ALL objects in the universe, on the average, are moving away from the Earth.


The only way ALL objects in the universe can be moving away from the Earth is if the

universe is expanding.


Expanding FROM where and TO where?

? ?


The Big Bang

The universe exploded into existence approximately 15 billion years ago (the Big Bang).

Shortly after the Big Bang, the hydrogen that makes up the current universe was formed. Other elements were subsequently synthesized from the hydrogen.

All of the material in the universe (including you) is 15 billion years old.

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Astrophysics and Cosmology How do we know what we know about the universe around us?