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Amare Abebe
Works at North-West University
Attended University of Cape Town
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Amare Abebe

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In a simulation of the universe without commonly made simplifications, galaxy profiles float atop a grid representing the spacetime background shaped by the distribution of matter. Regions of blue colour contain more matter, which generates a deeper gravitational potential.
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"there are two kinds of things that can either entice or repel us. The enticing ones are wealth, pleasures, beauty, ambition, and everything else that is seductive and pleasing. We are repelled by hard physical work, death, pain, public disapproval, and an austere diet. Hence we should train ourselves neither to fear the latter things nor to desire the former. We should contend against our inclinations, resisting the attractive things and advancing against those that assail us"

Seneca, Letters 123.13
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“Every time we witness an injustice and do not act, we train our character to be passive in its presence and thereby eventually lose all ability to defend ourselves and those we love.” -Julian Assange
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Michael Sandel explores the philosophical justifications made for national borders.
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"The Universe has been accelerating for the past six billion years, and if we had come along sooner than that, we might never have considered an option beyond the three possibilities our intuition would have led us to. Instead, we get to perceive and draw conclusions about the Universe exactly as it is, and that’s perhaps the greatest reward of all."

One of the biggest surprises in our understanding of the Universe came at the end of the 20th century, when we discovered that the Universe wasn’t just expanding, but that the expansion was accelerating. That means the fate of our Universe is a cold, lonely and isolated one, but it’s a fate that we wouldn’t have uncovered if we were born when the Universe was just half its current age. By understanding the Universe’s expansion history and determining what the different components are that it’s made of, we can figure out exactly how long the Universe has been accelerating. We find that dark energy rose to prominence some 7.8 billion years ago, and the Universe has been accelerating for the last 6 billion years. As the acceleration continues, more and more galaxies become unreachable from our perspective, even at the speed of light; that number’s already up to 97% of the galaxies in our visible Universe.
Dark energy dominates both the energy density and the expansion rate of the Universe, causing it to accelerate. But it wasn't always so.
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15 May is reserved to Johannes Kepler
On this day 1618 Johannes Kepler rediscovered his 3rd Law of Planetary Motion.

After I had discovered true intervals of the orbits by ceaseless labor over a very long time and with the help of Brahe’s observations, finally the true proportion of the orbits showed itself to me. On the 8th of March of this year 1618, if exact information about the time is desired, it appeared in my head. But I was unlucky when I inserted it into the calculation, and rejected it as false. Finally, on May 15, it came again and with a new onset conquered the darkness of my mind, whereat there followed such an excellent agreement between my seventeen years of work at the Tychonic observations and my present deliberation that I at first believed that I had dreamed and assumed the sought for in the supporting proofs. But it is entirely certain and exact that the proportion between the periodic times of any two planets is precisely one and a half times the proportion of the mean distances.”
With these words Johannes Kepler announced, in his usual overblown flowery style, his third law of planetary motion in the fifth book of his Harmonices Mundi.

While Kepler published his first two laws in 1609, the third law was published ten years later in 1619. Now it was known that the orbital period, the time taken by the planet to make one complete orbit around the sun, was lower for the planets closer to the sun than those farther away from the sun. Planet mercury, for example, is named after the Roman God Mercury who was the messenger of the Gods. Mercury circles around the sun in a mere 88 (Earth) days. Pluto, on the other hand, revolves around the sun in 246 years!

Kepler's third law finds the underlying pattern in these orbital periods and states:

The square of the orbital period of a planet is proportional to the cube of the semi-major axis of its orbit.

In other words, if T is the orbital period of the planet and D be its distance, T2 ∝ D3.

To explain simply, consider Earth. Earth is at a distance of 1 a.u. (1 a.u. = roughly 150 million km) from the sun and revolves in 1 year around the sun. Jupiter is about 5.2 a.u. from the sun.
If T is the orbital period of Jupiter, then...
T2 should be close to the 5.23 ≈ 140.
And what number squared is roughly 140? 11.8. And sure enough, Jupiter's orbital time is 11.8 years.

References:
http://www.physicsclassroom.com/class/circles/Lesson-4/Kepler-s-Three-Laws
http://www.mayankacademy.com/sci101/keplers_laws_of_planetary_motion/
http://csep10.phys.utk.edu/astr161/lect/history/kepler.html

#history   #physics   #astronomy   #kepler   #lawsofplanetarymotion  
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Monty Python’s Philosopher’s Football Match: The Epic Showdown Between the Greeks & Germans (1972)

If you like comedy and philosophy, then this is gold.
Last year, we witnessed a very tense, unpleasant showdown between Germany and Greece as the topmost nation in the European Union drove its most indebted country to make painful, perhaps punishing compromises.
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"it is better to help the bad because of the good, than to fail the good because of the bad"

- Seneca, On Benefits, IV.28.1
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Have them in circles
530 people
Martin Vermeer's profile photo
minasse geberemariam's profile photo
Himmy Jones (Himanot)'s profile photo
Tiri Chinyoka's profile photo
Lakachew Wubale's profile photo
Habtom Kassiye's profile photo
Ronald Mahomane's profile photo
Genaye Eshetu's profile photo
hlina belachew's profile photo
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Education
  • University of Cape Town
    (PhD, MSc) Cosmology, 2008 - 2013
  • Addis Ababa University
    (BSc) Physics, 2003 - 2007
  • Mekelle University
    Freshman, 2002 - 2003
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http://amexnett.blogspot.com/|http://amareabebe.blogspot.com/
Introduction
Memoria vitae bene actae iucunda est.
Work
Occupation
Cosmologist
Employment
  • North-West University
    Senior Lecturer, 2015 - present
  • North-West University
    Postdoctoral Fellow, 2014 - 2015
  • University of Cape Town
    2009 - 2014