JPL: Defenders against Near Earth Objects

I’m writing up our first reader request!  Among several questions I received was who is watching out for asteroids/meteors/meteorites?  As you all are aware from the Russian meteorite in March of 2013, these things still come flying at us and pose a legitimate threat (just ask the dinosaurs).

So what kind of programs do we have to watch out for these objects seeking to slam into our home?

The Future of Spaceflight: Part 5: Militarization of Space

We are, I hope, entering into a new era of space travel and exploration: private, commercial spaceflight. Space travel was always the domain of governments: mainly the United States and the Russians, but others are now joining the club. For this series of articles, I thought we would take a look at where we’ve been, where we are, and where we are going, both near-term and a little bit longer out.  Here, we discuss the potential for the militarization of space.

Parallel Universes: Coda

Not too long after writing my posts about different possible parallel universes, I read an article about a paper challenging the very premises of both level I parallel universes and the many-worlds interpretation of quantum theory.  I wanted to bring this article up to show just how speculative this particular subject is and to illustrate that the idea of parallel universes is still debated in the scientific community.

Parallel Universes: Part Three

You hear about parallel universes all the time in science fiction (see Fringe, probably a billion episodes of Star Trek, Stephen King’s Dark Tower series, etc.). But did you know that scientists take parallel universes seriously and consider them possible. There are several types of possible parallel universes.  This is the third post in a series of five posts.  The first can be found here and the second here.

Inflationary Bubbles

Up till now, we’ve dealt with universes that followed the same laws of physics and are much like our own universe.  Both the parallel observable universes and the many worlds interpretation of quantum mechanics started with the same initial conditions (what the universe was like in the instants after the big bang) and have the same laws of physics.  Now we start getting into universes that have different initial conditions and different laws of physics.

Everyone knows that the universe began with a big bang and has been expanding ever since. Fewer people know about the theory of inflation, which refined the big bang to explain some of its quirks.  Under the theory of inflation, the universe in its very, very, very, very early stages (specifically between 10^-36 to 10^-32 [a fraction that has 32 zeroes between the period and the number] seconds after the big bang) experienced a repulsive force so strong that it expanded 10^78 (a one with 78 zeros after it) times its initial size.  That is a ridiculously fast expansion given how huge the universe got in that ludicrously small amount of time.

Overall, the inflationary model is highly successful.  But, as with everything in science, there is still debate about some of the finer aspects of inflation.  So there are several inflationary models.  One of the most popular models right now is called chaotic inflation.  The idea is pretty simple: the universe is still undergoing inflation; but within that inflation, there are regions where the inflation stops and creates universes, including our own.  Each of these bubble universes would be another type of parallel universe.  However, the space between our universe and these bubble universes is growing exponentially and could never be crossed.  The chaotic inflation continues infinitely and generates an infinity of universes, and the “big bang” is only the start of each universe and does not correspond to the beginning of everything.  Max Tegmark calls these types of parallel universes Level II parallel universes in his taxonomy.

These bubble universes, unlike the other universes we’ve looked at, can be wildly different places from our own.  Some may have more dimensions, which is impossible for us to even wrap our head around (try watching this video about 4-dimensional hypercubes as an example; it’s boring and poorly shot, but it explains the concepts beautifully).  There could also be different types of subatomic particles, leading to strange, different states of matter.  Further still, these bubble universes could have different physical constants from our own, which would lead to matter interacting differently.  For example, one of the main physical constants is the cosmological constant, which determines the rate of expansion of the universe.  Too high and the universe will fly apart too quickly for galaxies and us to form; too low and the universe just collapses back in on itself before it even has a chance to get started.

Parallel Universes: Part One

You hear about parallel universes all the time in science fiction (see Fringe, probably a billion episodes of Star Trek, Stephen King’s Dark Tower series, etc.). But did you know that scientists take parallel universes seriously and consider them possible? There are several types of possible parallel universes.  In this series of articles, we are going to look at each of these different types.

Really, Really, Really, Really Far Away

Our universe is huge.  Mind-bogglingly, eye-poppingly, throat-stoppingly huge.  It is so huge that we are not even sure yet if it is infinite or not.  Regardless, the universe is so huge that we can only see a part it.

This is where we need to look at definitions.  When we say the universe, we generally mean everything in existence: the entire universe.  However, when scientists say “the universe,” they mean all the stuff we can see: the observable universe.  The observable universe is smaller than the entire universe.  Our range of vision is about 46 billion lightyears in any given direction.  So the observable universe is a bubble about 92 billion lightyears across.  For scale, the Milky Way is only 100,000 lightyears across, so the observable universe is 92,000 Milky Ways across.  Once again: huge.

So, where do the parallel universes come in?  Cosmologist Max Tegmark created a taxonomy of possible parallel universes.  One type is the stuff outside of the observable universe.  The idea is that, in a given volume of space (i.e., something the size of the observable universe), there are only so many possible configurations of matter.

Think of it like K’Nex: there are lots of different pieces, but they only fit together in a certain number of ways.  If you build a rollercoaster with your K’Nex, it’s not very likely that somebody else would build the exact same rollercoaster, but there is a small chance.  So if enough people build K’Nex rollercoasters, someone else would eventually make almost the exact same thing as you made.  It’s the same with observable universes.  If there are enough of them, the matter in them can only be arranged in a finite number of ways and you are bound to have near-duplicates.

The issue is, how many parallel observable universes do you need to have a duplicate of our observable universe?  As you can expect, it’s a lot.  Like, a lot a lot.  Like, the next closest duplicate universe is about 10^10^115 meters away from us.  That number is even bigger than a googolplex of meters, which I’ll leave to Carl to explain:

If you translate that into lightyears, it shaves a couple zeros off, but it’s not very much.  It’s hundreds and hundreds of observable universes away.  Tegmark even went so far as to say how far would have to go to find a duplicate of the solar system and its surrounding stars: 10^10^91 meters away.  A duplicate of just yourself: 10^10^29 meters away.  Much closer, but it still might as well be an infinity away.  Even if you allowed for slight variances in the arrangement of matter (like perhaps a blade of grass is missing here or there, or a few letters are missing from some books), it wouldn’t affect the distance calculation that much because those tiny differences don’t amount to the same scale of the total amount of matter.  A drop in an ocean doesn’t affect the ocean that much.

Suppose we invented some awesome new technology that allowed us to travel to these parallel universes, despite the absolutely, positively, massively massive distances.  What would we find there?  Well, pretty much the same thing we have here.  Since it involves the exact same entire universe, the laws of physics would be the same. If I were to travel to my duplicate’s house in that universe, I’d find him sitting in his den on his day off of work, typing this very article in his pajamas, while intermittently cleaning his dog hair-filled house.  And you would find your duplicate reading this very article, wherever you had been just before you traveled to the parallel universe.  Meta, huh?