Light Years and Our Universe STAAR th Grade

How far is far? (think of the furthest place) How fast is fast? (think of the fastest you can travel?

How do they measure that far? 9.46 trillion kilometers Light Year – the distance that light travels in 1 year which is equal to 9.46 trillion kilometers (in a vacuum) The symbol for light year is “ly”.

So, if Jupiter is 620 million kilometers away from Earth can light get from here to Jupiter in less than a year? Yes it can Monoceros Nebula is 1000 trillion kilometers from Earth. How many light years is this? Approximately 106

How many seconds are in a year? How many seconds are in a year?  31,557,600 s/yr

c = 299,792,458 meters per second  or 186,000 miles per second

The Speed of Light

One light year is approximately trillion miles (mi). Light travels 9.46 trillion kilometers (km) a year.

Light years are used to measure the vast distances in space. In the universe, the kilometer measure is too small to use.

Every time you look at objects in the night sky or the Sun, the light from that object is old. You are looking at history.

It takes 8 light minutes for light leaving the Sun to reach the Earth. To put this in perspective, if you could drive from the surface of the Sun to the surface of the Earth, it would take you 180 years driving nonstop at 60 mph.

Sirius, in the constellation Canis Major, is the sky’s brightest star. It is easy to find on winter and spring evenings. When you look at Sirius, you are looking back in time to see how Sirius looked 8 years ago. The light left the star 8 years ago.  So how many light years away is Sirius?  8 ly

Big Bang Theory (not the t.v. show) A theory that the universe started from a single atom! Georges Lemaitre – First suggested the “Big Bang Theory” This theory was made because scientist discovered that other galaxies are moving away from ours at a great speed (the universe is expanding)

Big Bang Theory With the Big Bang, space itself began expanding like the surface of an inflating balloon and all the matter moved along with it. The Big Bang is NOT like an explosion of matter, in otherwise empty space. Space itself began with the Big Bang and carried matter with it as it expanded. There was no explosion! there was, and continues to be, an expansion. It was an EXPANSION.

The Big Bang Scientist think that all matter was tightly compressed or squeezed into a hot, dense ball a few millimeters across. After the Big Bang the universe has continued to expand and as matter cooled more atoms developed as did galaxies and stars

Big Bang Evidence: what scientist use 1. The universe has to have a beginning 2. The galaxies are still moving away from each other (suggest that the universe was once much smaller) 3. If the universe was once hot there should be proof, and scientist found cosmic radiation readings that showed this. 4. The abundance of “light elements” such as helium and hydrogen.

Big Bang Scientist Albert Einstein – added to the Big Bang Theory with his own theory of relativity. Edwin Hubble – Discovered that the galaxies are moving away from our own at a great speed. (Hubble Law) Arno Penzias and Robert Wilson – discovered cosmic radiation