ScienceBlog

Supporting 21st Century Science GCSE

ScienceBlog

Scienceblog.org is our own portal for students and teachers. It brings all our latest articles, free images, newsfeeds, downloads, multimedia resources, and weblinks relevant for the study of  21st Century Science. This site is o­ne of  number of complementary websites we have developed for science education. All developed using wonderful Open Source software!

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Edwin Hubble and The Big Bang

Edwin Hubble was the first to measure the redshift of galaxies. This was an important discovery in providing evidence for support of  The Big Bang Theory.





GCSE Notes: The Expansion of the Universe and the Big-Bang theory

In 1929 Edwin Hubble discovered that a very large number of galaxies in the universe were moving away from each other. He was able to show that most of the galaxies were moving away from our solar system,and our galaxy. He was able to do this by using an effect known as the Doppler effect.

This Doppler effect is easily noticed using sound waves.

Doppler Effect

(Public Domain Image.  Source : Wikipedia)

When a siren from an ambulance moves towards an observer at a steady velocity the siren's pitch is higher than when the ambulance is at rest. When the ambulance moves away from the observer the siren's pitch is lower than when the ambulance is at rest. The change of pitch is due to a change of wavelength of the note, as detected by the observer.

The Doppler effect also occurs for electromagnetic waves emitted by a moving source.

* When galaxies move away from us the wavelength of light emitted from the galaxies increases.

* The greater the velocity of the galaxy the greater the increase, or shift, in wavelength.

* The change in wavelength is usually called the redshift.

This is because the wavelengths increase in the direction of the red end of the visible spectrum. By measuring the amount of redshift it is possible to calculate the velocity v of a distant galaxy moving away (or towards) Earth.

Edwin Hubble was able to show that the velocity of a distance galaxy , measured from Earth, was directly proportional to the distance of the galaxy from Earth.

Hubble o­nly had a few points to work with at first. Later evidence was able to support this proportionality between velocity and distance.

The direct proportionality between velocity and distance can be expressed as :

v = H d

where v = velocity of a distant galaxy from Earth.
H = Hubble's constant
d = distance between the galaxy and Earth (in our galaxy).


In the Big Bang theory the universe started billions of years ago.....

Expansion of the Universe

(Public Domain Image.  Source : Wikipedia)

According to the Big Bang theory, the universe originated in an extremely dense singularity. Space has expanded with time, and galaxies have been moved further away from each other.

Consider the distance (d) between two galaxies we observe today.  Let this be a time T after the Big Bang.

Using v = d / T we can then state that the age of the Universe is given by T = d/v

and Hubble's equation states that v = Hd ,   so substituting for v gives



The Age of the Universe    T = 1/H



Therefore a knowledge of the Hubble constant is important in our calculation of the age of the universe.  Unfortunately, there appears to be a large disagreement between scientists o­n the value to be taken for the Hubble constant. The main reasons for the differences arise from the errors (uncertainties) in the measurements of v and d , and the methods used to determine these values. To make things more complicated, Hubble constant will change with time, if the universe is decelerating in is expansion, as a result of gravitational attraction.

So, when is a constant not a constant? When it is Hubble's constant, so it seems.....

NASA's Wilkinson Microwave Anisotropy Probe (WMAP) project estimates the age of the universe to be:   13.7 x 10 9 years  ( plus of minus 0.2 x 109 years) . This is remarkably close to the value calculated using    T = 1/H .  Yet, the prediction all depends o­n the acuracy of the model,  and other methods could give deirferent fiugures for the age of the universe.

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Support for 21st Century Science

We have two dedicated websites for supporting 21st Century Science. You have just arrived at one of them!

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Webucate...our multimedia resource

Looking for more resources for your projects?  Try our multimedia gallery, for students and teachers ....

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Bird Flu...a matter of time?

Is there evidence that Bird Flu is spreading around the world? What are the dangers? Can anything be done?

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Earthquakes: What can be done to reduce the effects?

Another major earthquake has killed over 19,000 of people in Pakistan, and over 42,000 have been estimated to be injured. What can be done to reduce the effects of earthquakes?

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Understanding Radiation

Here is a useful o­nline resource which provides an introduction to radiation and the applications of radioactivity. Heath and Safety issues are also covered.

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Case Study: Radon Levels and Health

Radon is a radioactive gas that occurs naturally. Special precautions are needed to prevent radon gas from entering homes from ground sources.

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Reducing the risk of Heart Disease

Heart disease is not usually caused by an infection. It is usually either a result of genetic inheritance, your lifestyle, or a combination of both factors........

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Clinical trials of new drugs

How are new drugs tested?  What procedures are required?

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Case Study: Asthma and Michigan, USA

An alarming report by The Envirolink Network indicates that almost 10% of  the population of Michigan, over 870,000,  suffer from Asthma.

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