Theia and Luna

We are now going to deal with the most commonly accepted hypothesis that would answer several questions. Why is the Earth's axis tilted? Why do we have the seasons? Why we have climate differences? Why do we have a moon? Now you will know why.

Many different theories have been put forward for how the Moon formed, but only the Giant impact hypothesis is widely accepted today. The giant impact hypothesis states that the Moon was formed out of the debris left over from a collision between the Earth and a body the size of Mars, approximately four and a half billion years ago. The colliding body is sometimes called Theia, for the mythical Greek Titan who was the mother of Selene, the goddess of the Moon*.

Consequences of the Impact**

The cataclysmic impact between Theia and the proto-Earth, together with its result, the Moon, had some profound effects on Earth and its subsequent history. 

a.) The collision knocked the proto-Earth out of its position, producing the tilt in the Earth's axis, which is the cause of the seasons. 

b.) The moon's presence also helped stabilize this tilt, which is likely to have smoothed out climatic conditions over the whole course of Earth's history.

c.) When the Moon was first formed, the Moon was closer to Earth than it is today and these forces were more pronounced. Their strength may have triggered the development of Eart's system of tectonic plates.

d.) The Moon's gravitational pull produces the tides in our planet's oceans. By subjecting organisms that lived in tidal zones to daily (or twice-daily) fluctuations in their living conditions, the Moon may have influenced the pace at which life on Earth evolved.





* http://en.wikipedia.org/wiki/Giant_impact_hypothesis
** Robert Dinwiddle, Bite-Size Science. p.67

Size does matter

I will let you guys and gals watch a few videos first:

The one above is a bit dramatic, here is another more factual:

The one abvove was based on facts gathered about the cosmos.  Remember why they said that there are more stars in the Universe than grains of sand in all of the beaches of the world. The vast scope of the cosmos is very huge. 

This one is different, it also shows the world of the very small and very tiny.

By watching those videos, I would think that you already have some idea about the scope of our cosmos. Not just the cosmos but also our "inner cosmos". Well, you might ask, why am I viewing this, and why should I care? The answer is simple. It is mind-boggling and awesome to think about how large and I mean LARGE this place is.

You can visit http://scaleofuniverse.com/ created by Cary Huang to see their version of this scale of things that are large and small.

Here are some of the screenshots of that site:

Remember, the purpose of this blog is to learn and I am hopeful you are learning more about our Universe and everything inside it! Have fun learning!

Grains of Sand

What does Carl Sagan, Neil DeGrasse Tyson, Jim Al-Khalili, and Morgan Freeman have in common? 

They have mentioned in documentaries this powerful, thought provoking statement:

"There are more stars in the Universe than grains of sand in all of the beaches in the world."

Why are they saying this? We know for sure that we cannot count the actual number of grains of sand in the beaches where we live. But all the beaches in world? That would be an enormous figure if that is achieved. But we know it's impossible. So what is this with stars and sand?

It turns out, we need a thought experiment to grasp this idea. Let's just say that you are in a spaceship, and you are outside the Milky way galaxy - our home galaxy. Your ships computer scanned the galaxy and tried to count the number of stars. And the computer figured that the Milky way has approximately 300 billion stars. 

Now imagine your spaceship is capable of travelling to the very depths of the cosmos and the computer was able to get an estimate on the total number of galaxies in the known, observable universe. And that estimate is close to 100 billion galaxies. If each galaxy has around 100 billion stars for example, and there are 100 billion galaxies (estimates from the Hubble Telescope in 1999 puts it around 125 billion and it is slowly increasing as new technologies are invented), then how many stars there might be in the known universe? The numbers would be so, so huge we cannot even comprehend how large the numbers would be.

Jim Al Khalili 

 Morgan Freeman

 Carl Sagan

Neil DeGrasse Tyson

Ancient Astronomer : Aristarchus of Samos

I first heard of this astronomer in a documentary about Astronomy (though I forgot what documentary that is sadly). He is actually a pioneer in his time for his revolutionary ideas, particularly about the idea that the Sun is the center of the Universe, and that the planet Earth, as with other planets, are revolving around it.  

Aristarchus of Samos was an ancient Greek astronomer and Mathematician, who presented  a model, the very first of its kind, that actually placed the Sun at the center of the known universe with the Earth revolving around it. Born around 310 B.C.E.  (or Before Common Era commonly known as B.C.), that is around 2,300 years ago.  

His works unfortunately did not survive but his ideas are known from references by Greek mathematician Archimedes, the Greek biographer Plutarch, and the Greek philosopher Sextus Empiricus. His ideas were rejected at that time in favor of the Geocentric model, which explains that the Earth is the center of the Universe and the Sun and all the planets are circling around it. Ptolemy’s calculation based on this theory was used as the basis for this belief for the next 1,500 years until Nicolaus Copernicus re-ignited the interest for the Heliocentric model which is now a known fact today.

Geocentric Model of the Universe 

Picture source: http://outreach.atnf.csiro.au/education/senior/cosmicengine/images/cosmoimg/aristarchus.gif

Astrotalk

My fascination for the heavens started during the time I learned to look up in the sky one night and wonder to myself what these tiny blinking lights are.  I started to read books about these and that started my fascination for the stars. Due to the light polluted sky in Manila at night, I was not able to appreciate much of the stars when I look at them at night and I could only recognize a few patterns like the constellation of Orion (which is my favorite).  When we went to a place far from the city that is when I appreciate the night sky more. I can see a strip of light, much like a splatter of milk in the sky. Try it, look into a cloudless night sky and look at those lights until you can see that milky band.

What you are looking is actually one of the spiral arms of the Milky Way galaxy – our home galaxy:

Imagine that map at the top there is actually something that says “Our Solar System”. That means that is basically the calculated place where we live. Where our Sun could be found, and where the planet Earth is located. Isn’t it mind-boggling to think that we live in a place so huge. Actually so huge that you need to travel a distance of 100,000 light years to get from one end of the galaxy to the other!  Other sources say that the diameter of the Milky Way is between 100,000 to 120,000. 

Let me give you an idea how large are we dealing with here:

Light year – distance a ray of light takes to travel in a year. As defined by the International Astronomical Union (IAU), a light-year is the distance that light travels in a vacuum in one Julian year. That is around 10 Trillion Kilometers. And that is 10,000,000,000,000!!

So even if you have a spaceship that could travel the speed of light, It would take you 100,000 or 120,000 Earth years to travel from one end to another. Give it some thought about the vastness of our galaxy. 

Floating around...

Even since I was a kid, I was fascinated with anything that's 10,000 kilometers above my head - Outer Space that is. I used to go to libraries and check out Astronomy books and see some pictures of stars and planets, and those people who go there and explore! Floating above the earth, doing experiments, those who went to the moon, and now those who plans to go to Mars. Sometimes you can sense this envy, what lucky men or women they must have been. 

And fascinates me more is when they are floating in their space stations and rockets, looking like magicians that can float anything they wish to float to, except it is not magic. Weightlessness or Free Fall is the result of having 0 gravity forces acting on your body or an object. You may think of it as there is no gravity around but as Tega Jessa mentioned here: "Gravity actually exists anywhere two quantities of matter exist side by side." Eveything exert a gravitational force on another thing so to speak. But why float if that is the case?

It seems that the reason an astronaut floats because he is actually in a "free-fall" state. Imagine yourself inside a closed box and that box suddenly was released to fall into the earth. Inside the box, you will start to float around, since you cannot feel the pressure exerted outside the box. That is also the same thing astronauts face in space, only difference is they are not falling to earth but rather they are orbiting or circling the earth. It is also said that you also get zero gravity conditions in space flights which are literally explorations to the far corners of our solar system and hopefully beyond.

Enjoy watching some clips by Astronauts and Space Tourists floating around :

 A fascinating video of water floating at free fall:

Here is former BBC Science Chief and Popularizer of Science Mr. James Burke explaining Weightlessness training:

You can also do your own research. It's fun!

More information about Weightlessness:

Wikipedia

Britannica

Meteorite!

It was amazing what happened just 9 days ago in Russia. If you haven't heard of it, here it is:

Good news no one was hurt. Well, what is it? It is a rock, alien in origin and it comes from outer space. It is a meteorite! 

Meteorites are rocky objects from space that strike Earth. When meteorites pass through Earth’s atmosphere, they get heated and their surfaces become ionized, causing them to glow brightly, forming a streak moving across the atmosphere known as a shooting star or fireball. 

If the meteorite is large enough, it may not burn up in the atmosphere and will then strike Earth. Small meteorites may just crash on the surface, but the rare, large object can excavate a large impact crater, or do worse damage. 

At certain times of the year Earth passes through parts of the solar system that are rich in meteorites, and the night skies become filled with shooting stars and fireballs, sometimes as frequent as several per minute. Examples of these high-frequency meteorite encounters, known as meteor showers, include the Perseid showers that appear around August 11 and the Leonid showers that appear about November 14.

Here is a Nasa video something about the Perseids:

Meteor showers are way cool! But in case a meteor hits the ground, one for sure is, that it would create a big hole in the ground. And that is scary. A Crater shown below. This one is called the Barringer Crater in Arizona.

From: http://apod.nasa.gov/apod/ap971117.html

If ever a meteorite happens again I would certainly hope that in my lifetime it would only be to give us a good aerial lights show. :-)

Referrence:

Encyclopedia of Earth and Space Science. p. 59.