Earth’s Age: How old is the Earth?

Summary: The age of Earth has been estimated by analyzing how long it takes for the radioactive elements of uranium to decay into lead. How old is the sun and how long will it last?


Well, the universe itself is thought to have had its beginnings with the Big Bang which occurred anywhere from six to fifteen billion years ago. The Big Bang was a gigantic explosion which catapulted enormous amounts of matter rocketing through space. Eventually the matter was pulled by gravity into the beginnings of present day galaxies and solar systems. Many believe the formation of the earth began at least 4.5 billion years ago, that’s 4,500 million years. This age has been estimated by analyzing how long it takes for the radioactive elements of uranium to decay into lead. The fossil record also backs up this estimate of our planet’s age.

And just how much is a million? Well, if you start counting now and count one number every second for eight hours a day seven days a week in just over a month you may have counted to a million.

Earth rocks as old as 3.6 to 3.9 billion years old have been discovered around Greenland and the Northwest Territories of Canada. The first animal life on earth is relatively new. It occurred only at the end of the Precambrian Period a little over 500 million years ago.

And how old is the sun?

The sun is also believed to be about four and a half billion years old which means it is about middle-aged as most scientists believe it will burn out in another 5 billion years. How does a star that is about 900,000 miles across (that’s more than 100 times the width of the earth) burn out?

Wait, wait, you say the sun is a star?

That’s right, the sun is a star just like the little twinkly ones we wish on at night. It’s just a lot closer to earth, so close in fact that we can feel the warmth of its enormous heat. At its center the sun has a temperature of more than 10 million degrees. The sun’s surface, the part we see, is about 5,800 degrees but the outer reaches of its atmosphere heat back up toward two million degrees. And, oh yes, in another 5 billion years or so it is expected that the sun will begin to expand by about 100 times turning it into what is scientifically knows as a red giant. At that time the sun will have burned up all of its helium and will collapse in on itself and become just a white dwarf.

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