We see them as they were 13 billion years ago. The elements hydrogen and helium make up 98 percent of the matter we can see in the Universe. As a result, astronomers think galaxies contain dark matter, which we cannot see. There is also an unknown force making the Universe expand, known as dark energy.
In this series of pictures, each stage represents a microscopic speck of the image to its right. Instead, astronomers use the speed of light as a yardstick. Light is so fast it can travel around the Earth 7.
One light year is the distance light travels in a year: nearly 6 trillion miles 10 trillion km. Do you like this book? Please share with your friends, let's read it!! Disclaimer : BooksWarrior does not own this book pdf, neither created nor scanned. We just provide the link already available on the internet and in google drive.
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Big ideas simply explained Item Preview. EMBED for wordpress. Want more? Advanced embedding details, examples, and help! Topics dorling kindersley , DK Publishing , DK , Big ideas simply explained , History , sociology , psychology , crime , business , literature , science , philosophy , religion Collection opensource Language English.
The psychology-book DK publishing.
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