"The Big Bang Theory" and the Doppler Effect.

Yesterday I discovered a chapter of "The Big Bang Theory" absolutely awesome. Real Fun!

In this episode,  Sheldom Cooper is disguised as a "Doppler Effect", a very well-known effect in Physics.  It has to do with some original features of waves, such as sound or light: it is the change in frequency of a wave for an observer moving relative to its source.

I will try to give you a simple example: 

Think about a train coming in our direction: the sound we hear  is more piercing than usual (we say the wavelength is getting shorter). But once the train passes us and starts moving away, the sound we hear gets  deeper (and then we say the wavelength is getting longer).  This simple experience is what we physicists label  as a "Doppler Effect". And it is surprisingly useful, since for example you can prove the expansion of the Universe with it...

If you haven´t heard about it before this post, perhaps now you  can enjoy this:

In English

En español

That is all, just have fun!

How many dimensions are there in our Universe?

                                 
When we think about an object, we are talking about  how long, wide and high it is.
 In Mathematics we would say that  three dimensions are required to describe it. (3D). Furthermore, if we consider time as an additional dimension, then it would be easy to   admit   that we are living  in a 4D Universe.

Everything had seemed quite logical and made sense...at least until some physicists started to work very hard  on  an incredibly complex theory, known as String Theory. This principle tries to explain our Universe as it is, and it  must be said  that with much success. But in case this Theory is on the money, then...ok, it is weird...but our Universe should be 11 dimensional  (!!!!!!)
11-D?  but we can for sure  "feel" just  four dimensions, can´t we? where are the  other  ones? how can we figure out what it is like  to live in such a Universe?
I will do my best  to throw some light on this craziness: try to think of a civilization living in a Flatworld,  a very far away place  in which everything is plain, so things and life forms are wide / long but  they are not endowed with any height at all. what would happen in case we got to Flatworld? How would  their inhabitants see us?  and how would we see them? In the following clip Dr. Quantum sets out  such a peculiar world. Real Fun!

After watching the clip, please give this some thought: maybe we are living in our familiar 4 dimension  world, without noticing  the 11 dimension beings around  us;  and may be some of them   can see  us but we just can´t detect them ... does it make any sense?

Next clip (below)  Carl Sagan explains  in a very  simple way a  world beyond three dimensions:

And that is it. I hope you will find it interesting , and perhaps you change your mind (a little bit?)  about  what "reality" means.

PS: There is not a definitive proof for  String Theory, so maybe this is all just a weird theory...or maybe not?

¿Qué caerá antes al suelo, una pluma o un martillo?

  Esta es la pregunta que se hacía Galileo a principios del s.XVII, y llegó a la sorprendente conclusión  de que, si se lanzan simultáneamente una pluma y un martillo desde una misma altura y al mismo tiempo, ambas deberán caer al suelo a la vez. Y que si esto no ocurría exactamente era por efecto de la atmósfera terrestre, que producía un rozamiento que afectaba de manera diferente al martillo y a la pluma. Por lo tanto, un experimento que a Galileo le hubiera gustado seguramente  muchísimo hacer es el de hacer caer una pluma y un martillo pero QUITANDO LA ATMÓSFERA. Aunque claro,  no pudo hacerlo ¡una lástima!

Hoy en día sabemos que Galileo tenía razón. En notación moderna (si por "moderno" aceptamos mediados del s. XVII)   diremos que la fuerza o peso P  con que la tierra atrae a un cuerpo de masa m es:

                                 P = m x g

y que por tanto todos los cuerpos, independientemente de la masa, están sometidos a la misma aceleración g=9,8 m/s2. Y al estar sometidos a la misma aceleración, deberán caer al mismo tiempo.

Lo cierto es que si preguntas a un estudiante en pleno s.XXI qué caería antes, seguramente diría que el martillo, por lo que llevamos 4 siglos sin asimilar el concepto...

Volviendo a Galileo,  lo cierto es que en la Luna no hay atmósfera prácticamente, así que seguramente al genial científico  hubiera dado mucho por poder ir a nuestro satélite y hacer su famoso experimento,  y eso es exactamente lo que hizo el  astronauta David Scott en el transcurso de su misión en la Luna (Apolo XV), en el año 1971, a modo de homenaje a Galileo.

Creo que este vídeo debería ser obligatorio en cualquier sitio en el que se enseñe gravitación, por favor no os lo perdáis porque es una joya de la historia de la Ciencia. Que lo disfrutéis!!!