Presentation on theme: "How far is far? How fast is fast? What Is It? A light year is the DISTANCE that light DISTANCE that light will travel, through a will travel, through."— Presentation transcript:
How far is far? How fast is fast?
What Is It? A light year is the DISTANCE that light DISTANCE that light will travel, through a will travel, through a vacuum, in one year. vacuum, in one year. Vacuum is space that is devoid of matter
How many seconds are in a year? 31,557,600 s/yr
The Speed of Light
c = 299,792,458 meters per second or 186,000 miles per second
To get an idea of how fast this is... light can travel about seven times around Earth in one second!
One light year is approximately 5.880 trillion miles or 9.5 trillion km. The symbol for light year is “ly”.
Light years are used to measure the vast distances in space. In the universe, the kilometer measure is too small to use.
The distance to the next nearest big galaxy, the Andromeda Galaxy, is 21 quintillion km. That's 21,000,000,000,000,000,000 km. This is a number so large that it becomes hard to write, to relate to, and to use in calculations. Astronomers use other units of distance.
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 eight 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 eight years ago. The light left the star eight years ago.
Proxima Centauri lies in the constellation of Centaurus (The Centaur), it is 4.22 light years away from our Earth, and Sun Its average luminosity is very low, and it is quite small compared to other stars Proxima is what is known as a flare star," meaning that convection processes within the star’s body make it prone to random and dramatic changes in brightness.