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# Scientific Notation

## Writing and reading scientific notation

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Visiting Our Neighbors

Credit: robin_24
Source: http://www.flickr.com/photos/robin24/5468858841/

How long would it take humans to reach the closest star? Would we be able to send astronauts to explore it? If someone journeyed to another solar system, would she ever see Earth again? The distances between stars are mind-bogglingly big. In sci-fi movies, space ships are able to jump between stars in an instant. In real life, space travel takes a lot longer.

#### Our Farthest Voyage

Before we can even think about visiting another star, we have to leave our own solar system. Launched in 1977, the Voyager 1 space probe (depicted in the image below) left the solar system on August 25, 2012. It took 35 years to enter interstellar space, and it’s traveled 1.2×1010\begin{align*}1.2 \times 10^{10}\end{align*} miles since its launch. The closest star, Proxima Centauri, is 2.5×1013\begin{align*}2.5 \times 10^{13}\end{align*} miles away, which means that Voyager 1 has only traveled less than 11,000\begin{align*}\frac{1}{1,000}\end{align*} of the way to the nearest star. If we sent people into space using the same technology, it would take them 19,000 years to reach Proxima Centauri. That’s the amount of time that’s passed from the Stone-Age era of cavemen until today. For a ship of humans to reach another solar system at those speeds, entire civilizations would rise and fall without ever seeing another planet or sun.

Credit: NASA
Source: http://commons.wikimedia.org/wiki/File:Voyager_spacecraft.jpg

Voyager 1 is the fastest space object we’ve ever built. However, some scientists believe it could be possible to create nuclear-powered space ships capable of traveling at half the speed of light. It would take them only 89 years to reach Proxima Centauri. That means that only a couple of generations of humans would have to spend their lives hurtling through space. Unfortunately, we can’t build or test these ships. International law forbids the dumping of nuclear waste in space, and a nuclear-powered ship would leave a trail of waste behind it. Unless we find a new way to power space ships, we might be stuck in this solar system forever.

See for yourself: http://www.abc.net.au/catalyst/stories/3785366.htm

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1. [1]^ Credit: robin_24; Source: http://www.flickr.com/photos/robin24/5468858841/; License: CC BY-NC 3.0
2. [2]^ Credit: NASA; Source: http://commons.wikimedia.org/wiki/File:Voyager_spacecraft.jpg; License: CC BY-NC 3.0

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