The Fate of the Universe

 Astronomers can use telescopes to look deep into space, where essentially we are looking back in time, and try to understand how the universe began. We know from observations that the universe is about 14.5 billion years old, and that it's currently expanding due to some Big Bang or moment of Inflation sometime in the past. Based on the current structure of our universe, and the theories behind how it began, astronomers are trying to predict the fate of our universe. What will eventually happen to the universe billions of years from now?  Below are four current theories.

 

 

1. Infinite Expansion: The universe will expand forever. We will survive, but eventually loose contact with places that are too far away and ultimately be isolated in darkness.
2. The Big Rip: The expansion of the universe will continue to increase until it expands so fast that spacetime itself is ripped to shreds. The fate of humanity is unknown.
3. The Big Chill: The universe will expand and continue to cool until it reaches absolute zero. At this temperature, all movement will cease and black holes will evaporate into the vacuum of space. Essentially we will freeze to death.
4. The Big Crunch: gravitational pull from black holes  will cause the expansion of the universe to stop, and the universe will collapse back onto itself. We will not survive, but a new universe may be created in a second big bang after the crunch. 

As time goes by we hope to learn more about the structure of our universe and be able to accurately predict which one of the above (or a completely different scenario) will be true. Sadly, none of these scenarios are "happy endings".  I guess our best hope lies in the bubble universe theory. This says that other universes have budded off of ours and are completely separate and now unbound to ours.  If we are in trouble in the future, maybe we will have the technology to travel to a more stable bubble universe and continue to live there!

Image credit: LSST

Flowing Water On Mars!

The above image was taken back in May by the Mars Reconnaissance Orbiter, a satellite orbiting Mars that takes photos of the Martian surface. First released last Friday, the image depicts dark brown streaks  on the edge of a crater. These streaks appear during the Martian summer, then fade away during the winter months, and reappear again the next summer. It's believed that these streaks are actually flowing  liquid salt water on Mars! That's right, I said flowing liquid water! Over the past decade or so, astronomers have found much evidence that water flowed on Mars sometime in the past, but they believed that conditions on Mars today are too harsh to support liquid water. I guess they were wrong!

The main thing preventing liquid water from flowing on other planets is temperature. Planets closer to the sun than Earth are too hot; any water would evaporate. Planets farther away from the sun than earth are too cold; any water would freeze. Temperatures on Mars range from 68 F during the summer, to -124 F in the winter, with an average of -81F. So in the summer months Mars can get warm enough to have flowing liquid water! One thing that also helps is the fact that the Martian surface is very salty. This salt gets dissolved in any surface water, lowering the freezing point of water and preventing it from turning to ice. (This is why we throw salt on the roads in the winter, it lowers the waters freezing point preventing ice from forming.) Any water on Mars will be very salty, allowing it to be in liquid form at fairly cold temperatures. Water that has dissolved as much salt as it can possibly handle has a freezing point of -4 F.

This discovery  of this water on Mars has once again peaked interest in astronomers minds about searching for life on Mars. Maybe there are some microbes or bacteria that live in the water during the summer months? We will have to wait for the next round of Mars rovers to find out!

Image Credit:HiRISE, MRO, LPL (U. Arizona), NASA