Saturday, March 25, 2017

The Scale of the Universe Boggles

Environmental & Science Education
Mathematics Education
by Edward Hessler

On February 15, 2017 I posted some comments about light speed in an attempt to help in thinking about large, really big numbers.

Deep time is another way of conceiving space (and thinking about large numbers) — the cosmos from one end to another. It takes lots of time to get from here to there.

When I wrote the first post I considered including a comment made by the late Stephen Jay Gould in a lovely book he wrote, Time's Arrow, Time's CycleSo, here it is:
An abstract, intellectual understanding of deep time comes easily enough — I know how many zeros to place after the 10 when I mean billions. Getting it into the gut is quite another matter. Deep time is so alien we can really only comprehend it as a metaphor.

So I come at the idea of thinking about big numbers again, thanks to Michael Strauss, an astrophysicist at Princeton who made these observations in a great essay in Aeon.

A flight from Dubai to San Francisco is about 8000 miles (12874.75 km).

That distance is roughly equal to the diameter of the Earth.

The sun's diameter is just over 100 times Earth's (1287475.2 km).

The distance between the Earth and the Sun is some 100 times larger than this or some 100 million miles. (12874752 km)

That distance represents the radius of the Earth's orbit around the Sun and is used as a fundamental unit in astronomy, the Astronomical Unit (AU).

The spacecraft, Voyager 1, was launched in 1977. It has been zipping along ever since at 7 miles per second. It is now 137 AU from the sun after 40 years. I doubt very much that I would have been close had I been asked to make an estimate.

Voyager's journey [Wikimedia]

NASA's Jet Propulsion Laboratory
 maintains an odometer in kilometers and astronomical units which can be checked anytime.  This seems a good place and time to stop using kilometers and use AUs. The nearest star is Proxima Centauri, about 270000 AU out there. 270000 AU is ~4.25 light years.

This number provides a reference point for thinking about cosmic distances. The average distance between stars in the Milky Way galaxy is about 4 light years.

Professor Strauss's essay may be found here.  He notes that the universe always escapes even the most-imaginative science fiction. He also makes a plea for a cosmic perspective.

This is another way, a delightful way, to consider the solar system, the galaxy and the universe from Monty Python.

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