About 3.26 billion years ago there were no animals as we know them today.  There were no dinosaurs.  There were no fish.  Basically, there was some land, lots of water, and lots of bacteria floating around in that water.  Earth was formed only 1.34 billion years before this, and evolution takes time, so the bacteria were doing a pretty good job at evolving into what would become multicellular life (but that was going to take more than another billion years).  

Anyway, all the bacteria were floating around in the water when something pretty serious occurred. 

A massive asteroid measuring about 36 miles across smashed into the young Earth.  We've known for a while that this happened but we didn't know how bad it was.  Geologists, geophysicists, and other awesome intellectuals have done some outstanding research into the event.  We now know what happened when this asteroid struck the Earth. 

The impactor was the size of Rhode Island and four or five times larger than the asteroid that is believed to have wiped out the dinosaurs.  It was moving about 12 miles per second (over 40,000 mph).  

When you take something that big and smash it into_ something else, it hurts.  Earth didn't like it.  The impact was so great that the ENTIRE earth experienced a quake of about 10.8 on the Richter Scale.  This earthquake caused more earthquakes and in all, the Earth shook for about a half hour.  Mountains literally collapsed.  

Remember all that water I was talking about?  Yep, you guessed it, tsunamis were everywhere.  In fact, it's projected the tsunamis were up to 3,000 feet high. 

As with most asteroid strikes, a bunch of red hot Earth was thrown into the atmosphere that eventually scorched the surface of the Earth.  Oceans boiled (well at least the tops boiled), the sky turned to fumes, and everything was just not very nice.

But some pretty amazing things happened when this asteroid (and other struck the Earth).  No one really knows how or why Earth ended up with tectonic plates that slide under, over, and past each other. Some geologists believe that impacts like the one I just discussed essentially started the process of plate tectonics on Earth.  Think about that.  Giant rocks smashing Earth eventually caused the crust to fracture enough to become massive islands.  These islands float around and collide on top of an ocean of magma. Pretty cool.  

Furthermore, and this is conjecture but I'm certain many would agree, this impact probably changed the course of evolution.  How?  I'm not sure.  Maybe we would have twelve fingers instead of ten if the asteroid did not hit.  That's the beauty of it!  Every little thing in history shaped who we are today.  Again, pretty cool. 

Anyway, thanks for reading.  

Here are some sources: 
http://blogs.kqed.org/science/2014/04/10/new-study-examines-geologic-impact-of-a-massive-asteroid-collision-on-ancient-earth/

http://geosociety.wordpress.com/2013/04/28/when-did-plate-tectonics-begin-on-earth-and-what-came-before/

In 2005, when I was a senior in high school and didn't know much about science, I was staring at the night sky and came to a realization:

If the Universe is infinite, then why isn't the whole night sky full of stars?  

Think about it:  If the Universe is infinite there there are infinite stars in infinite angles in relation to Earth.  Therefore, the entire night sky should appear at least as bright as our own Star during the day.  Don't understand what I mean?  Look at this image, which represents what I'm talking about:

I asked my 12th grade astronomy teacher if was I was thinking was right.  She said that theoretically yes, but distance plays a role in brightness.  I accepted that answer and moved on, until recently, when I thought about it again.  

There is a proper name for this phenomena, it's called Olbers' Paradox.   It is named after the German astronomer Heinrich Wilhelm Olbers and also called the "dark night sky paradox."  It is the argument that the darkness of the night sky conflicts with the assumption of an infinite and eternal static universe.  A static universe is a universe not expanding or contracting, but remaining the same.  

So why isn't the night sky as bright as our Sun?  Two theories when combined make sense.  

• The Universe is expanding, so light from distant stars is pushed out of the visible spectrum as the wavelength increases.

• The Universe is young and light from distant stars hasn't reached us yet.

The first reason essentially means that the Universe is not static, it's expanding (which is what I believe) and that light emitted from distant stars is slowly increased in wavelength down the visible spectrum to red and then out of the visible spectrum, making the light invisible to our eyes.  It doesn't mean we can't pick up the energy through other means (infrared, radio, etc.) but we just can't see it with our eyes.  So, in that sense, my teacher in 12th grade was very correct.

The second reason means that the Universe is not infinite, it's finite- it has an age, a size, and a finite amount of stars.  However, even if there are so many stars in the Universe we still could not escape seeing ALL of their light, therefore making the night sky much brighter than it is.   So what's the catch?  

Estimates are that the Universe is somewhere around 13.7 billion years old.  The catch is that light from stars that are more than 13.7 billion light years away (due to expansion) hasn't reached us yet and when it does the night sky will get brighter.  

Honestly the whole concept is confusing but I hope I was able to explain it a little bit.  The most important thing you should take away from this is that when someone says the Universe is infinite, you can ask them why, then, is the night sky not as bright as our own star.  Something to think about!

Thanks for reading, and trying to understand.