Can Aliens Watch TV?

Assume you're an alien civilization flying through space in your fancy high-tech rocket ship, and you stumble upon the solar system. You decide to cruise through, passing each planet searching for signs of "alien life". Your space ship is equipped with a radio telescope, and you point it at all the planets as you fly by. You figure that radio waves are good at carrying information, so any sort of advanced civilization would have figured out how to use them to transmit signals and therefore their planet would glow with radio waves. As you fly by Earth, you point your telescope towards the atmosphere and change any incoming signal to sound waves. What do you hear?

You would probably get a jumbled noisy message of clips from your favorite TV show  mixed with blips from songs on XM radio and search results from Google. Right? Wrong! (Even I though you'd get some radio signals from Earth, so don't feel bad!) The reason Aliens won't be able to listen to XM radio and watch TV is because of Earth's Ionosphere. The ionosphere is the very upper layer of Earth's atmosphere , and is basically a mixture of molecules in a gaseous/plasma state.  When the sun's rays and the solar wind hit the Earth, it ionizes molecules in the ionosphere. When this happens, radio signal is emitted, and the northern lights are created. This happens so often that the amount of radio signal emitted way overpowers any signal produced by humans that leaks out into space. So if you turned this radio signal into sound waves, you wouldn't hear beautiful music…. you'd hear some pretty awful screeching. Astronomers have actually recorded the noise Earth makes. You can listen to it here: http://www.space.com/10296-earth-alien-sounds.html

Einstein's Theory of General Relativity Proved True!

A huge breakthrough in theoretical astrophysics was announced last week, proving Einstein's theory of general relativity true! In a nutshell, Einstein said that the 3-D space we live in plus a fourth dimension of time is linked together as one entity called spacetime. Heavy objects such as stars, planets and galaxies distort spacetime; basically space bends around these objects. Think about putting a bowling ball on a trampoline. The Sun is the bowling ball and the trampoline is spacetime. The bowling ball is so heavy that sapcetime bends around it. Now roll a marble, which signifies the Earth, around the outside of the trampoline. The Earth revolves around the sun because it's essentially trapped in the funnel of spacetime caused by the Sun. That's why all the planets revolve around the Sun.

 

Artist conception of frame dragging due to a black hole

The big discovery that was made was the proof of what Einstein called frame dragging. The theory of frame dragging can be understood using the following example. The sun rotates on it's axis and as it does so, it drags spacetime with it. This slight dragging of spacetime causes the precession of planets. So instead of the Earth following the exact same oval every time it orbits the sun, the oval moves slightly. (Kind of like how you make a flowery pattern using the old spirograph toys.) Until very recently, scientists did not know the origin of this precession, and frame dragging was one of many theories behind it. With the help of a telescope called Gravity Probe B, they were able to prove that large objects like the sun do drag spacetime with them as they rotate, and this causes the precession of other small objects that orbit it.  The details about this experiment are a bit over my head, but the fact that we observationally proved general relativity true is a big step forward in astronomy!