Williams News Logo
Grand Canyon News Logo

Trusted local news leader for Williams AZ and the Grand Canyon

The age of the Earth and other astronomical measurements

The scientific method – hypotheses, theories and laws

Science is a way to understand the world, utilizing well described consistent methods and principles. Unlike a belief system where someone makes a statement and others follow it without question, the principles and theories of science have been established over the last four centuries, employing and applying repeated experimentation and observation. The results of these experiments are then refereed through peer review before being accepted by the scientific community. Science is also flexible in that as new data become available, previous scientific explanations may be revised and improved, or sometimes occasionally replaced. There is a regular progression from making a hypothesis (an idea or proposition that can be tested by observations or experiment), to becoming a theory using testable, scientific laws. To the general public, the term “theory” is often assumed to imply mere speculation. However, in science, something is not classified a theory until it has been confirmed over many independent experiments. Only a few scientific facts are considered natural laws, and many hypotheses must be tested before they are considered acceptable theory. Therefore, theories must be compatible with the observed evidence and consistently tested against a wide range of phenomena, and re-tested as new information arises.

How scientists date things

Before modern science was developed, people thought that Earth was about 6,000 years old. As scientific thinking advanced through the 17th, 18th, 19th and 20th centuries, scientists needed to understand and more accurately determine when events had occurred in the past. In varying scientific disciplines , new methods and techniques were developed to enable accurate dating. Dendrochronology, the measurement of the pattern changes in the growth thicknesses of tree rings because of annual changes in temperature and rainfall has been used in Archaeology. Where wooden structures survive, dates can be determined to the year the wood was harvested, and is now accurate back to about 26,000 years in some parts of the world. Radio-carbon dating, using the known rate of degeneration of carbon-14 within organic materials, is reliable to dates as far back as 50,000 years. There are also many other types of radioactive decay measurements that are used in certain geologic applications, such as uranium-yhorium (accurate to 500,000 years ago), and uranium-lead (accurate as far back as 4.5 billion years.) There are now dozens of different dating techniques available to scientists in most of the disciplines, and when dating samples, he, or she, will use many available methods, and not rely on only one, so they can be assured that the results are well supported.

The age of the Earth and astronomical measurements

A different, and more direct, method of determining some very large ages of geologic activity on Earth has been made by correlating the corresponding shapes of the continents of Europe with North America, and Africa with South America. The latter two of these large land masses especially appear as if they are separated pieces of a jigsaw puzzle. It has also been noted that the lower geologic layers on each pair of continents are identical. In fact, we now know that continents actually drift on what are called tectonic plates, and that in the middle of the Atlantic Ocean there is an area of up-flowing magma that is slowly pushing the continents apart. Using current satellite technology, scientists are able to determine that the continents are separating at a rate of about one inch per year. Since Africa and South America are currently separated by about 2,000 miles, at one inch per year, the two continents would have begun separating about 140 million years ago, which corresponds in time to the time when the lower geologic layers would have been together.

Let us consider the age of the Earth. As scientists studied the many geologic features on Earth, they noticed deposited layers that held fossils from ancient sea creatures and coral located at the tops of mountains. These, and other natural phenomena that would require very long time frames to occur, led them to begin thinking that the time scales must be decidedly greater than those previously thought. One recent method for determining the age of the Earth has been by determining the known rates of radioactive decay of a form of the element potassium (K) which degenerates into another element, argon (Ar). By studying the oldest and least disturbed meteorites such as those found at Meteor Crater in Arizona, as well as the oldest of Earth’s geologic layers with respect to this K-Ar transformation, the varying geologic strata have been found to range from about 400 million years to around 4.5 billion years. Using other techniques, geologists now mark the Earth’s age at 4.55 billion years.

Looking beyond Earth, astronomers, using data from the Hubble Space Telescope, stellar parallax, and the knowedge that the speed of light is a constant, are able to directly measure distances to objects in space out to 20,000 light years (i.e. it has taken the light 20,000 years to reach Earth). Through observing variable stars, measurements have shown that the distance to the nearest major galaxy, Andromeda, is about 2.5 Million light years away, while using other measurement techniques, distances to much further galaxies have been measured in distances of billions of light years from us. Up through the 20th century the universe was believed to be 13.8 billion years old. However, with new and more accurate data being acquired and new measurement techniques being created, it may be found to be many times that old.


Donate Report a Typo Contact