Bell Ringer 8/25

You may write this week’s bell ringers on the same paper as last week’s bell ringers, just be sure to include the correct DATE!!

• In your own words, describe the Big Bang Theory.

30.3 Big Bang Theory

Review

Scientific methods• State a problem• Gather information• Form a hypothesis• Test hypothesis• State a conclusion

Hypothesis to Theory

• Once a hypothesis is tested and generally accepted, the development of a theory begins

• Theory = a hypothesis or set of hypotheses that is supported by a result of experimentation and observation

Theory

• A theory provides a general explanation, consistent with known fact

• A theory is tested many times….if it is proven correct every time it becomes scientific law

Scientific Law

• A rule that correctly describes a natural phenomenon

• Law of gravity– Proven every time it is tested

Light

• Isaac Newton – observed sunlight passing through a glass prism

Spectrum

• Display of colors– ROY G. BIV

• R = Red• O = Orange• Y = Yellow• G = Green• B = Blue• I = Indigo• V = Violet

Light & Color• Light travels in waves, like the

ocean waves• Wavelength = distance between

crest of one wave to the crest of the next wave

Wavelength

Wavelength & Color

• We see different colors because they have different wavelengths

• Red has the longest wavelength• Violet has the smallest wavelength• Prism = get a band of colors

because each wavelength bends differently

Bright-line spectrum

• 19th century – scientists learned that chemical elements produce spectra– When heated elements produce a series

of colored lines

• Bright-line spectrum = series of colored lines– Each element has a unique bright-line

spectrum, like a fingerprint

Doppler effect

• When light source moves toward you, the wavelengths produced appear shorter

• When the light is move away from you, the wavelengths seem longer

• Doppler effect = the apparent shift in wavelength energies emitted by a moving energy source

Example of Doppler Effect

• Fire engine siren• As the fire engine is driving closer

to you, the pitch of the siren seems higher

• Once the fire engine passes you and is driving away, the pitch of the siren seems to fall

• http://www.walter-fendt.de/ph11e/dopplereff.htm

Homework

• Chapter 1 Review Questions

• Page 23-25

• #6-12, 17, 20, 25, 30

Bell Ringer 8/26

• What is the Doppler effect?

• Draw a picture to describe it!

30.3 B Notes

Red Shift & Big Bang Theory

Doppler Effect

• Doppler effect = apparent shift in the wavelengths of energy emitted by an energy source moving away from or towards an observer

Spectroscope

• Scientists used a spectroscope to study what elements were in stars– Spectroscope = instrument that splits

white light into a band of colors

• Scientists were able to determine chemical make-up of stars

Red Shift

• Scientists soon found that the spectra of many galaxies were shifted toward the red end of the spectra

• Showed that almost all the galaxies were moving away from the Earth

• That means the solar system is still expanding

Theory

• Observing the red shift led scientists to form a hypothesis about the expanding universe– Billons of years ago, all matter and

energy was compressed into a small volume

– Sudden event = BIG BANG = sent all the matter and energy outward

– Some matter gathered in clumps and formed galaxies

Big Bang Model

• The theory that the universe began as a point and has been expanding since is the Big Bang theory.

Big Bang Model

• In the Big Bang model, the momentum of the outward expansion of the universe is opposed by the inward force of gravity acting on the matter of the universe to slow that expansion.

Big Bang Model

Outward Expansion• When the rate of expansion of the universe

is known, it is possible to calculate the time since the expansion started and determine the age of the universe.

• Based on data from the Hubble Space Telescope and the data on the cosmic background radiation, the age of the universe can be pinpointed to 13.7 billion years.

Bell Ringer 8/27

• What is Red Shift? How is it related to our universe?

Big Bang Model

Based on the Big Bang theory, there are three possible outcomes for the universe.

1. The universe could be an open universe and continues to expand forever.

Possible Outcomes

2. The universe could be a closed universe where the expansion stops and all of the mass is pulled back to the original point of origin

3. or it could be a flat universe where the expansion becomes so slow that it seems to stop.

Closed universe

Flat universe

Critical Density

• All three outcomes are based on the premise that the rate of expansion has slowed since the beginning of the universe, but the density of the universe is what is unknown.

Cosmic Background Radiation

• In 1965, scientists discovered a persistent background noise in their radio antenna.

• Persistent background noise was caused by weak radiation, called the cosmic background radiation, that appeared to come from all directions of space and corresponded to an emitting object having a temperature of about 2.735 K (–270C).

Cosmic Background Radiation

• The temperature was very close to the temperature predicted by the Big Bang theory, and the radiation was interpreted to be from the beginning of the Big Bang.

• Earth’s atmosphere blocks much of the cosmic background radiation, so it is best observed from high-altitude balloons or satellites. – An orbiting observatory called the Wilkinson

Microwave Anisotropy Probe (WMAP), launched by NASA in 2001, mapped the radiation in greater detail.

Quick Recap

• Background radiation = low levels of energy evenly distributed throughout the universe– Scientists used radio telescopes to

find background radiation

• Most scientists accepted Big Bang Theory as the origin of the universe

Quick Recap

• Red shift = spectra of galaxies on red end of spectra– Means the galaxies are moving away

from the Earth

• Big Bang Theory = matter and energy was compressed in small volume and hurled outward in the universe

In-class Assignment/Homework

• Worksheet: Big Bang Theory• Turn into folder when finished or

tomorrow during bell ringer

Bell Ringer 8/28

• What is Background Radiation? Why do scientists connect it to the big bang theory?