Thursday, November 13, 2008

What's Up? Space isn't so empty after all

Welcome back to What's Up?

Last month, the Hubble Space Telescope was scheduled to be serviced for the fourth time in its eighteen-year history.

Just a few weeks before this mission was due to leave, one of Hubble's main computers failed. That computer controls the majority of communications with Earth. On October 16, engineers working with the telescope successfully rebooted the backup system. They were about to resume normal scientific operations when problems with the backup system caused it to suddenly go into "safe mode".

The mission to repair Hubble has been delayed until February 2009 or maybe longer, depending on whether the backup system can be up-and-running. If not, they may replace it with a spare that has been in storage for over 20 years.

Everyone will have to hold their breath and see how this turns out.

Since no science is currently being done with the Hubble, let's look at the vacuum of empty space. Is it really empty?

At first glance it may seem like that's the case, but it actually isn't. Let us take a closer look.

Flying in every direction through the universe are photons (particles of light) emitted from stars, quasars, and supernovae, just to name a few. Some photons have been flying through space since nearly the beginning of time. These early photons form what is called the Cosmic Microwave Background (CMB).

The CMB was created about 380,000 years after the universe was created in the Big Bang. The reason all these photons were released at that time is because that's when the universe became transparent to light. Before that time, the universe was so dense that as soon as a photon was given off it hit another particle and was absorbed. The moment the universe became transparent to light was when all this light was released and it now flies through space at the speed of light in all directions.

The CMB has been mapped just to see what the brightness differences in different parts of the sky is like. It was found that it is nearly completely smooth. This shows that the universe was nearly perfectly smooth when it formed. Thankfully there were some small, very slightly denser regions. These regions ended up forming galaxies which allowed us to form over 13 billion years later.

Also shooting through "empty" space are weird little particles called neutrinos. Neutrinos are nearly weightless and rarely interact with other matter. They are mainly formed in nuclear reactions within stars. In fact, you have billions of neutrinos pass through your body every second.

Neutrinos are detected using special neutrino detectors. Neutrino detectors are essentially giant containers of a dense liquid filled with very sensitive light detectors. Every time a neutrino hits one of the liquid particles in the container a flash is given off, and this is detected by one of the light detectors. These neutrino detectors are buried deep below the ground to prevent them from interference with cosmic rays (particles that fly through space and sometimes make it through the atmosphere and would cause a false detection). There is one of these detectors in Canada. It is buried 6800 feet below ground and is located near Sudbury, Ontario.

Imagine an empty box that is impervious to photons and neutrinos. Would it be empty? No. Gravitons are still everywhere.

Gravitons are particles that carry the force of gravity. At this point they're still hypothetical, since they have never been detected. It is impossible to find an area of space where there are no gravitons when we are contained within a universe full of matter (all matter emits gravitons).

Let's imagine that box again except in a universe where there is no matter or anything else mentioned so far. It appears to be finally empty. But it's not yet empty! How can this be?

In the vacuum of space, there is something called vacuum energy. Within every cubic inch of space are millions of particles popping in and out of existence. It is composed of pairs of particles that form because of quantum fluctuations in space. These pairs of particles usually consist of one particle and one antiparticle (made of antimatter - essentially particles that have charges exactly opposite to that in normal matter).

Antimatter and normal matter annihilate themselves when they get near each other. In other words, the two particles vanish, in a flash of energy. This energy is so small that it is nearly undetectable. This was proven in the lab back in 1948 by Dutch physicists Hendrik B. G. Casimir and Dirk Polder. The two scientists placed two small metal plates next to each other and there was a small force of attraction between the two plates. This was caused by vacuum energy.

If all of this doesn't make much sense, don't worry, very few scientists actually understand how this works. Just remember: particles are popping in and out of existence everywhere.

Let's take a look at what is happening with some of the objects among all this "empty space".

On Nov. 13 there will be a full moon and on Nov. 27 will be a new moon.

Space Shuttle Endeavor is scheduled for launch on Nov. 14. It will carry various equipment to the International Space Station.

Until next month, just look up!

Hey Kids...

Did you know that other planets have different amounts of gravity than the Earth? If you were able to stand on Jupiter's surface you would weigh over two times what you weigh on Earth. If you stood on the surface of the moon, you would weigh six times less than what you weigh on Earth. The denser (density is the amount of mass in a certain amount of space) the planet you're standing on, the heavier you will feel. This is because denser objects have a stronger gravitational pull. Go to to see what you would weigh on other worlds. Just enter your weight in the box provided and click the "calculate" button. Then scroll down and it will say what you weigh on other planets and even what you would weigh on a few stars!