Observing the Universe

                
 
  The main tool in Astronomy is LIGHT! And it is a powerful tool.

  Light travels at a speed C =300,000 km/sec.

  In time T it covers a distance L = C x T

  In one year, light covers a distance of ONE LIGHT YEAR = 10¹³km.

  We use many different forms of light: visible, X-rays, radio waves...

From Tiny to Huge

In Astronomy, we observe many objects, some small, other bigger, yet other much, much bigger.

To measure distances and the time to travel them, we use physical UNITS.

Distance is measured in meters, or kilometers (1 km = 1,000 m), or light years.

Time is mesured in seconds, days, years,...

  A square 10,000 km = 10⁷m covers nearly the entire Earth.

   Light covers this distance in a fraction of a second.

  The distance from the Earth to the Sun is 10,000 times larger, 10¹¹km.

  Light covers this distance in 5.5 minutes.

  A distance a 1,000 times larger,  10¹⁴km = 10 light-years is that to the nearby stars.

  Light covers this distance in 10 years!

   Our galaxy, the Milky Way is another 10,000 times larger,  10²¹km

   Light covers this distance in 100,000 years.

As we can see from these examples, distances in Astronomy are so huge, as are the times to cover them, that we simply
cannot use ordinary numbers to describe them.

This is why we must learn and use the SCIENTIFIC NOTATION, i.e. express numbers using POWERS OF TEN.

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To appreciate all this in more detail, go ahead and PLAY on your own with many scales of the universe using this

JAVA ANIMATION.

Page last updated on August 29, 2005 by V. Dobrosavljevic