AstroandMe

15 – Northern lights

astroandme — Fri, 19 Jun 2009 16:14:57 +0000

I grew up in a part of the world where people came from afar to see colours dancing in the sky. Northern lights, or Aurora Borealis, is an astonishing sight, that was first believed to be some kind of reflected moonlight. There is an old folk tale of a fox running in the snow, sweeping up snow in the air with its tail, that reflects light from the moon. In reality, northern lights is an effect of the Earth’s magnetic field and interactions with the so called solar wind.

The sun is continuously blowing away charged particles from its outer atmosphere out into space. This flow of particles, the solar wind, is blowing with speeds between 400 and 800 kilometres per second! This wind exerts a push on Earth’s magnetic field, distorting it. Instead of having a spherical shape, the field is pushed towards the earth on the side facing the sun and away from the earth on the other side.

The blue lines represent the Sun’s magnetic field lines, and the yellow are the Earth’s. The magnetic field protects the Earth from the steady shower of charged particles, but it is not a perfect shield. Particles comes in through the gaps near the poles, as visualised in the picture, and it is these particles who are responsible for the auroral lights. That is why auroral lights only can be seen near the poles.

When a charged particle enters a region with a magnetic field, the particle feels a force. The direction of motion of the particle is always perpendicular to both the direction of the field and the direction of the force. This means that a particle moving with right angles to a magnetic field will be deflected sideways, so that it undergoes spiral motion.

Hence the particles entering the Earth’s magnetic field will spiral in towards the atmosphere. What the particles really do is spiral back and forth between the poles, until they come sufficiently close to the Earth to collide with atoms high up in the atmosphere, mainly oxygen and nitrogen. The energy of the colliding particles excites electrons from inner shells in the atoms, to outer shells. When these excited electrons jump back to inner shells, the excess energy is released by emitting visible light. This is the northern light.

Depending on how high up in the atmosphere the collision occurs, the element decides the colour of the light.

Because auroral light is an effect of the solar wind drawn by a magnetic field to collide with an atmosphere, Saturn is the only planet besides the Earth that has auroral light.

14 – Update on Lulin

astroandme — Thu, 26 Feb 2009 23:39:52 +0000

I’ve still not had a chance to see the comet Lulin! It’s near impossible in a city, you have to go to the countryside where there is no light pollution. It can be a bit tricky to bring a telescope, especially if you don’t have one of your own, but a pair of binoculars should do just fine.

Just go to a place where there are no lights, and try to find Saturn which is fairly easy, and Lulin will be somewhere between Saturn and Regulus in Leo. You will easily find Leo by locating the Big Dipper and then searching for a reversed question mark beneath it. The dot in the question mark is the bright star Regulus. On the 27th Lulin will be right next to Regulus!

Go to this website for more information:
http://www.skyandtelescope.com/observing/home/35992534.html

While you are out there with your binoculars, take a look at the Orion Nebula as well! I am sure you are familiar with Orion’s belt; three distinct stars in a row. Right underneath the belt is the sword which consists of three other stars in a row but with a different slope. The star in the middle of the sword is actually the nebula!

However the nebula will rather reveal itself as a tiny, fuzzy grey cloud as opposed to the beautiful colours seen in pictures like this:

I’m going to the countryside tomorrow! Fingers crossed for perfect weather!

13 – The comet Lulin

astroandme — Tue, 24 Feb 2009 23:43:00 +0000

This week the comet Lulin is as close as it ever gets to Earth, and therefore the brightest and easiest to see from here. I was at the observatory this evening, working, and hoped I would be able to look at it in one of our telescopes, but no I was disappointed. The observatory is located in the outskirts of the city, and though Lulin and Saturn were above the horizon, they were right above the other end of town, AND the sky was a bit misty, so there was too much disturbing light.

What a shame!

Picture from http://www.skyandtelescope.com/observing/home/35992534.html
where there is lots of more information!

My fellow workers at the observatory is going to try again tomorrow and on Thursday, so they will phone me in the case of success. Fingers crossed!

12 – Importance of language in science

astroandme — Sun, 22 Feb 2009 18:42:19 +0000

Post number 11 tried to justify why science is important. This got me thinking of the importance of other areas of knowledge to science. Not only am I very fond of the natural sciences, I am also very humble, so I would like to acknowledge the fact that the natural sciences would not make progress without language.

In Natural Sciences, scientists perform experiments to understand nature and its components, and they develop theories and models that try to explain how nature behaves. Since the theories can never be proven to be true, but only resist falsification (see post no. 9), experiments in Natural Sciences have to be repeatable in order for the theories and results to be accepted as truth. Language is then important to be able to compare the results from independent experiments. Otherwise scientists could only rely on the results from their own experiments which might not at all coincide with true nature.

Without language, scientists would not have access to earlier established and accepted theories which means they would all have to start from the very beginning, the very basic ideas in their science. There would be no progress whatsoever in the discoveries of natural sciences, considering it would be impossible for one single scientist to discover and understand all the mysteries in nature in one lifetime. Even if he did, the knowledge would die with him once he dies, because without language he would not be able to pass on the knowledge to the next generation. Hence the natural sciences cannot simply rely on the inductive way of learning, but deduction is also important; scientists depend on other scientists, which makes communication, and therefore also language, crucial.

Another aspect in the Natural Sciences that increases the importance of language is the size and distance to objects or pieces of nature being described, the complexity of nature and restrictions of the human brain, that ultimately demands the use of mathematics. Mathematics can be considered a language on its own, and is vital in many branches of the natural sciences, physics as an example. In order to gain knowledge from experiments, data needs to be collected, interpreted and processed. This is done with the aid of numbers and formulas, and through mathematics, conclusions can be drawn from the phenomena observed. Because mathematical errors then affect the results of the experiments, knowledge in physics relies on knowledge in mathematics.

Then of course, one can discuss whether or not mathematics is a language of its own. What do you think?

11 – Why science is important

astroandme — Sat, 21 Feb 2009 02:30:26 +0000

As an advocate for science and especially space science, you often encounter the question: “Why do we need science?”, or the more common wording: “Why should we spend so much money on space research when it can be used for so much good on Earth instead?”

This question has always been a tough one to answer, because the people asking have already made up their mind about science.

I think people take todays technology for granted. They don’t pay much attention to how it came into being, so instead of showing gratitude for science, they complain about unnecessary resources being spent on it.

I have always believed that we might find solutions to problems here on earth by gaining more knowledge about the universe, but I also believe that we cannot predict how or when these solutions will show up. They will probably reveal themselves as a by-product of some other discovery in astrophysics or quantum physics or any other science.

Like the example in the video below, the global positioning system, GPS, would not work without Einstein’s theory of relativity. Scientists back then had no idea that Einsteins discovery would solve the problem of navigation on Earth, just like scientists today cannot immediately see how new cosmic discoveries can solve problems closer to home.

We just need to stay open-minded.

Now enjoy the video of Phil Plait, also known as the bad astronomer, explaining why science is important.

Never forget.

10 – My tuesday

astroandme — Tue, 10 Feb 2009 21:15:20 +0000

Tonight was my tuesday off work. Probably the only tuesday outside the observatory for a long time. Instead, I have been busy calculating a lot of values and uncertainties by hand from a simple experiment. Quite tedious. I think I’m off to bed now, so that I am fresh for yet another day at university tomorrow. We are doing multivariable calculus and C-programming, oh I really look forward to next year when I get to do much more interesting things. I am going to a whole new university, in a totally different country! Yay!

More science tomorrow! Good night!

9 – The theory of Everything?

astroandme — Mon, 09 Feb 2009 21:57:30 +0000

Today I had quite an interesting discussion with a polish mathematician about theories in physics and mathematics.

Most people think that what is “scientifically proven” means ultimate truth, but the fact is that theories in physics can never be proven to be correct. This might sound odd, but theories that are believed to be true today, are only thought of as truth because no one has managed to prove them false yet. It is just like the old saying, “innocent until proven guilty”.

Theories that have so far resisted falsification, and that are hence thought of as truth, might anytime be falsified. This is because theories in physics always seem to just be useful to a certain extent. They might fit a specific situation, while they do not hold from a more general point of view.

Therefore, all the laws and theories in physics, that has resisted falsification as of today, might crash as soon as scientist are able to zoom out even more. This leads to the question of the theory of Everything. A theory that would combine all other theories to explain all of the universe, and that would not have any contradictions.

The problem is, how do we know when we have found this universal theory? If theories are only true as long as they resist falsification, such a theory would have to resist being proved wrong for an infinite amount of time to be seen as the ultimate truth. Surely this is an impossibility.

What do you think? Will we ever find such a theory? And if we do, will we ever know it is the ultimate truth?

8 – Gravity in terms of Spacetime

astroandme — Sun, 08 Feb 2009 18:13:34 +0000

I found a video on youtube that explains gravity as the warping of spacetime. It is not very detailed, and the animations shows spacetime as a two-dimensional fabric, while real spacetime is four-dimensional, but it can help to understand the idea.

Enjoy!

7 – Spacetime

astroandme — Fri, 06 Feb 2009 00:22:31 +0000

The speed of light is the ultimate speed limit in the universe, like explained in post number 6. Because of this, the speed of light is constant to any observer. All observers measures the same value for the speed of light in all events, independently of the speed of the source of light.

Speed is the distance travelled in a certain time period. Because the speed of light is constant, something must happen to the time and space, and this was first discovered by Einstein.

Think of a spacecraft travelling at 0.8 times the speed of light. The light sent out from that spacecraft cannot have 1.8 times the speed of light, so someone estimating the speed must either underestimate the distance or overestimate the time.

Actually for an observer, time seems to slow down for the object in motion, while the distance shrinks, and it does so in the exact way needed for the speed of light to always be measured as 300 000 kilometres per second. This means that time and space are not the constant things we view them as in everyday life. It is only the speed of light that is constant.

This has another important implication. Think of a person being positioned right in the middle of two bombs and this person sees the bombs detonate at the exact same time. If someone moving at high speed from one bomb towards the other passes by the person standing still at the time when the bombs detonate, this someone will be moving TOWARDS the light sent out from one of the bombs, and AWAY from the light from the other. This means that the person in motion will se the light sent out from the bomb in front of him BEFORE he sees the light from the bomb behind him. Simultaneous events for one observer is not simultaneous to another moving observer!

What this means is that, the time does not only slow down while the space shrinks, but time can appear as space and space can appear as time, for two different observers moving relative to each other!

The true nature of time is that it is actually intertwined with space! They are both merged into some kind of union called Spacetime. This has been hidden for us for a long time, since the effects of time dilation and space contraction are only noticeable at speeds close to the speed of light!

More about Spacetime another spacetime, it is already past bedtime. Night!

6 – The ultimate speed limit

astroandme — Wed, 28 Jan 2009 22:04:22 +0000

Continuing on the track set out in post number 5, about the true nature of time:

Light does not travel at infinite speed, but at 300 000 kilometres per second. This is the ultimate speed limit in the universe. Only 16 years of age, Einstein posed the question: “What would a beam of light look like if you could catch up with it?” To understand his question, imagine you are driving a car along a highway, and looking at another car beside you that is driving at the same speed. If you disregard the changing scenery in the background of the car, the car appears to be stationary!
Einstein reasoned, that if it was possible to catch up with a light beam, it would seem stationary. However, the findings of Scottish physicist Maxwell showed that light is an electromagnetic wave, and there is no such thing as a stationary electromagnetic wave. Hence a stationary beam of light is an impossibility, which ultimately means that ever catching up with light is also an impossibility!

Because the speed of light is the ultimate speed limit, it is independent of the speed of the source. No matter how fast a lamp or a star travels through space, the speed of the emitted light is still 300 000 kilometres per second!

In the next episode of AstroandMe, the mysteries about the true nature of time will be revealed! Don’t go anywhere!