Friday, December 4, 2009

thought experiment - how big is space.

Here is some good clean educational fun about space (my favorite subject). For me, those huge measurements like '1 billion light years' are very hard to grasp.. It makes it easier if you start from where we live.

It takes the earth 24 hours to make a circle on it’s axis
It takes the moon one month to go once around the earth
It takes the earth (and moon) one year to go around the sun
It takes Pluto (the farthest micro-planet so far) 247.9 earth YEARS to make one trip around the sun

Now.. Think about this..

The sun is orbiting something too.. Our sun is ONE of the BILLIONS of stars in the milky way galaxy.. The sun (and its planets AND all the other stars in the milky way) are orbiting the super-massive black hole in the center of the galaxy.

It takes the Sun (and us) 200 MILLION years to make one rotation around the big black hole.. We aren’t even on the edge of the milky way like Pluto is on the edge of our solar system. We are in the middle of the disk of things orbiting the black hole.. That means that some of the outside stars may take a BILLION years just for one rotation!!!

Now that you know how big the milky way is.. Our galaxy is only one of billions of galaxies that are out there.. They are all moving around space too although no one knows where from or where to.. Now that you know how big just our galaxy is, think about how big space must be for those galaxies to move around and not be smacking into each other all the time... Now you can see why light takes BILLIONS of years to get to us.. Space is just that big!! Our absolute nearest neighbor galaxy is still 2.2 MILLION light years away..

Light years are mainly about distance.. But because the distances are so big, it takes a lot of time to travel - Even for light.. The distance light can travel in one year is 6,000,000,000,000 (6 trillion) miles.. So if something is JUST 4 light years away, that is 24 trillion miles..

Now think about that newest neighbor being 2.2 million light years away!!  If someone near that star turned on a flashlight, it would take that light 2.2 million years to make it to us. At the end of it's journey, it will have travelled this many miles 18,200,000,000,000,000,000.

To get a visual idea of how big space is.. This is a photo taken by Voyager 1 which was launched in 1977 the year after I was born. In the 30 years, it has only gotten to the edge of the solar system (pretty close to Pluto).. You know how big Earth is right? This is what Earth looks like from the half-way point or, where Voyager 1 was in 1991.. So this is what the Earth looks like from half way to pluto. 

Here is another REALLY cool site for space that is geared more for kids for more information.

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