Читать книгу Universe: The story of the Universe, from earliest times to our continuing discoveries - Peter Grego - Страница 29

From our impossible perspective, viewing a cube of space 10 billion light years to each side, most of the objects in the visible Universe can be seen. Each dot represents a cluster of galaxies.

As we look further out into space, we are looking backwards in time. Light from the nearest galaxies in our local group takes a few hundred thousand to several million years to reach us, and we are seeing them as they appeared before homo sapiens sapiens walked the Earth. Galactic clusters and superclusters are arranged in filaments and sheets surrounding huge empty voids. Astronomers work out the distance of far away galaxies by measuring how much light is shifted towards the red end of the spectrum or redshifted. The greater the observed redshift, the greater a galaxy’s distance. Telescopic deep field images have revealed faint galaxies so distant that we see them as they appeared several billion years ago – before life itself developed on Earth.

Our picture of the wider Universe is based on redshift measurements.

Want to know more?

Take it to the next level . . .

Stellar distances 63

Galactic redshifts 64

Expanding Universe 66

The Big Bang 66

Other sources. . .

Computer software – some programs give detailed data and images about near and deep space

Go observe! Invest in a pair of 7x50 binoculars and begin exploring the skies

Weblinks. . .

Learn about the Solar System www.nineplanets.org Astronomy Picture of the Day – discover the cosmos http://antwrp.gsfc. nasa.gov/apod/astropix.html

NASA’s Imagine the Universe http://imagine.gsfc. nasa.gov