The age of the universe can be estimated using Hubble constant. Using elementary mathematical reasoning, it can be shown that an estimate of the age of the universe is just 1 divided by the value of the Hubble constant. The result will comes out in years, when the Hubble constant is converted to units of km/year per km. (review the Hubble worksheet and the constant measurement)
Study the example below to under the conversion process.
Hubble constant value is 20 km/sec per million light years. This number converted to km/year per km is about 6.7 X10-11 km/year per km. The age of the universe is
| age = 1/6.7 X10-11
= 1.5 X 1010 years = 15 billion years |
The value of Hubble constant are between 15 km/sec per million light years and 30 km/sec per million light years. Practice using Hubble constant with extreme values. It should be noted that we are assuming the expansion is at a uniform rate. In reality, it is not. It is thought that is was expanding much faster during its early existence.
When working with redshift equation, makes
ure that the results of radial velocities are small compared to the speed
of light. Otherwise, we would need have in clude the relativistic version
of the redshift equation.
| radial velocity = redshift + 1)2 - 1 X 300,000
km/sec
redshift + 1)2 + 1 |
adapted from Mark Twain Media, Inc., Publishers