Determining the size of the universe

Measuring the enormity of space is a task best left to the professionals – and even they don’t know!

Image source: Pixabay

The universe is a vast space that is simply incomprehensible to the human mind. The distance between London and New York is considered a large distance by many, but it pales in comparison when you think that it would take 2.5 million years to get to our closest galaxy while travelling at the speed of light.

Astronomers have spent decades trying to determine the size and age of the universe, and their closest estimate to the size of the observable universe is 46 billion light years across. This is just the area that astronomers can observe, and in fact they think it could even be double that size. The way they have managed to estimate such a number is through the use of astronomical distance measuring beacons that are known as ‘standard candles’.

The premise is simple. In the same way that you know what the brightness of a candle is while you hold it in front of you, it will gradually appear dimmer the farther it is from you. By measuring the difference in actual and perceived brightness, the distance between you and the candle can be determined. Astronomers use the same method on astronomical objects, and in the case of this research, a group of stars known as Cepheid variables are used. They have been studied for a long time using telescopes such as NASA and ESA’s Hubble Space Telescope, and provided help in deducing this mind-boggling figure.

Putting the universe into scale

From the Solar System to the Cosmic Microwave Background, the observable universe is filled with majesty

Image credit: © NASA; NASA/JPL-Caltech/R. Hurt (IPAC); PABLO CARLOS BUDASSI

This article was originally published in How It Works issue 123 


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