The Basics of the Big Bang

The Basics of the Big Bang Theory

Cosmology: The Study of the Universe

Cosmology is the scientific study of the large scale properties of the universe as a whole. It endeavors to use the scientific method to understand the origin, evolution and ultimate fate of the entire Universe. Like any field of science, cosmology involves the formation of theories or hypotheses about the universe which make specific predictions for phenomena that can be tested with observations. Depending on the outcome of the observations, the theories will need to be abandoned, revised or extended to accommodate the data. The prevailing theory about the origin and evolution of our Universe is the so-called Big Bang theory.

Multiple Select

What is Cosmology? Check all that apply

• Scientific study of the large scale properties of the universe as a whole

• It endeavors to use the scientific method to understand the origin, evolution and ultimate fate of the entire Universe.

• The study of cosmetics and application of makeup to the face

Multiple Choice

In the text, the term 'endeavor' most likely means...

• Works hard to

• Doesn't want

• Finds it easy

Big Bang Cosmology

The Big Bang Model is a broadly accepted theory for the origin and evolution of our universe. It postulates that 12 to 14 billion years ago, the portion of the universe we can see today was only a few millimeters across. It has since expanded from this hot dense state into the vast and much cooler cosmos we currently inhabit. We can see remnants of this hot dense matter as the now very cold cosmic microwave background radiation which still pervades the universe and is visible to microwave detectors as a uniform glow across the entire sky.

Multiple Choice

The Big Bang Model suggests that the universe has....

• Expanded, was once hot and dense and now cool

• Shrunk, was once cool and is increasing in temp

• The same as it was billions of year ago

Multiple Choice

What is the relationship between 'hot, dense matter' and the 'cold,cosmic radiation'?

• The hot, dense matter was created by the cold cosmic radiation

• The cold cosmic radiation is what is left of the hot,dense matter

• They both include references to temperature

• Matter and radiation are the same thing

Big Bang Theory #1. General Relativity

Einstein's theory generalizes Isaac Newton's original theory of gravity, c. 1680, in that it is supposed to be valid for bodies in motion as well as bodies at rest. Newton's gravity is only valid for bodies at rest or moving very slowly compared to the speed of light. A key concept of General Relativity is that gravity is no longer described by a gravitational "field" but rather it is supposed to be a distortion of space and time itself. Physicist John Wheeler put it well when he said "Matter tells space how to curve, and space tells matter how to move." Originally, the theory was able to account for peculiarities in the orbit of Mercury and the bending of light by the Sun, both unexplained in Isaac Newton's theory of gravity. In recent years, the theory has passed a series of rigorous tests.

Multiple Select

Check all that apply-A key concept of 'relativity' is that...

• gravity only applies to bodies at rest

• gravity is not a 'field' but a distortion of space and time

• gravity only applies to bodies in motion

• 'matter tells space how to curve, space tells matter how to move'

Big Bang Theory #2: The Cosmological Principle

After the introduction of General Relativity a number of scientists, including Einstein, tried to apply the new gravitational dynamics to the universe as a whole. At the time this required an assumption about how the matter in the universe was distributed. The simplest assumption to make is that if you viewed the contents of the universe with sufficiently poor vision, it would appear roughly the same everywhere and in every direction. That is, the matter in the universe is homogeneous and isotropic when averaged over very large scales. This is called the Cosmological Principle.

Multiple Choice

From the context of the reading, what do you think the term 'isotropic' means?

• Uniform in all orientations

• Physical property has the same value when measured in all directions

• Properties are identical in all directions

• Any of the descriptions given

Multiple Choice

From the context of the reading, what do you think 'homogeneous' means?

• Different

• The same

• Scattered

• Rare

The Cosmological Principle continued...

This assumption is being tested continuously as we actually observe the distribution of galaxies on ever larger scales. The accompanying picture shows how uniform the distribution of measured galaxies is over a 70° swath of the sky. In addition the cosmic microwave background radiation, the remnant heat from the Big Bang, has a temperature which is highly uniform over the entire sky. This fact strongly supports the notion that the gas which emitted this radiation long ago was very uniformly distributed.

Cosmological Principle

-The matter in the universe is homogeneous (the same) and isotropic (properties are equal in all directions)

-The cosmic microwave background radiation has a temperature that is mostly uniform across the entire sky

-So, the gas (which emitted this radiation long ago) was most likely very uniformly distributed

Open Ended

Does this information fit in with what you thought you already knew about the Big Bang Theory? EXPLAIN why or why not, using specific evidence from the reading

Open Ended

How does this information relate to the phenomena videos that we watched?