What is gravity?
For those interested in the study of our universe, this video-based online course gives an introduction to the basics of astrophysics, including concepts such as gravity and its far-reaching influence.
The course offers learners an insight into the physical phenomena produced from stars and planets to galaxies including our own Milky Way. It offers an understanding of how the universe works by using the only information it provides – light.
The course is led by the experienced astrophysicist Professor Frédéric Courbin and his team at Swiss university EPFL (École Polytechnique Fédérale de Lausanne).
We interviewed Professor Courbin and he explained more about his MOOC (massive open online course) – and why Dark Energy and Dark Matter are still unknown forces in the universe.
"Gravity is the Force That Shapes the Universe Itself"
Edukatico: Professor Courbin, is it true that gravity is the dominant force in the universe? Will participants of your MOOC be able to understand gravity?
Professor Courbin: Gravity is everywhere and acts on infinite distances. Gravity is responsible for the shape objects have in the universe, for their motion and for their evolution with time. It is the force that in fact shapes the universe itself.
As an introduction to astrophysics, this MOOC presents simple Newtonian gravity rather than the more complex gravitation theory involving Einstein's General Relativity. But this is enough to understand many of the celestial bodies around us, either nearby or billions of light years away.
Edukatico: What about Dark Energy and Dark Matter: What´s the biggest obstacle so far to really understand these phenomena?
Professor Courbin: Only 4% of the universe is composed of "ordinary matter", also known as Baryonic matter. The rest of the energy is Dark Matter (about 25%) and Dark Energy (about 71%).
The problem with the former is that we don't see it and we don't know its nature, but it is sensitive to gravity and produces gravity, so we can have a hint of its distribution through its effect on celestial bodies or even on light through the phenomenon of gravitational lensing.
The latter is thought to be responsible for the observed accelerated expansion of the universe and acts as a repulsive force that counterbalances gravity. However, we know even less about Dark Energy than Dark Matter and only indirect observations help understand it. In fact, if Einstein's description of gravity on cosmological distances is not fully correct, there is no need to invoke the existence of Dark Energy to explain the accelerated expansion of the universe.
The main obstacle in cosmology is currently that many different and poorly known components of the universe act on observations in similar ways. As a consequence, it is very hard to sort out what physical phenomenon is responsible for what observation.
It's like trying to guess the shape of an object from the shape of its shade: if you don't know where the sun is, you can't answer the question.
Intro to the Astrophysics Online Course
"Students Can Understand the Main Principles Without Going Through Complex Calculations"
Edukatico: What are some other key topics that are covered in your online course?
Professor Courbin: The course covers a very broad range of topics, from the formation of stars, planets and galaxies to the interaction between light and matter and it also introduces some elements of cosmology.
Each topic is addressed in a simplified but still realistic way so that the student can get the main principles without having to go through long and complex calculations, aside from a few videos that are more technical.
In many cases, the course also makes the link between theoretical predictions and observations with telescopes over a broad range of wavelengths from X-ray to optical and then radio.
Edukatico: Who can participate in your course? Is it designed for university students or for the general public?
Professor Courbin: Basic math and physics are needed, and the course is indeed a university class, but is presented in a simplified way.
In some places the math and physics level may go beyond what's available in the general public, but overall, 50% of the course can be understood with a good high school level or a first year of university.
Edukatico: Your course is available in French and in English. Is the content the same? Are there further languages to come?
Professor Courbin: Yes, the content is the same. In fact, the English version is a dubbing rather than a genuine English version (which would require re-recording everything in the studio again).
I also speak Spanish so, in principle, I could do it in this language as well, but again this requires re-recording everything again. Dubbing in any language remains possible however.
Edukatico: Thank you for this overview and all the best for your MOOC!
The astrophysics online course is offered as a MOOC (massive open online course) on the edX platform.
The course is free for learners and has already had 14,000 participants from 130 countries (8,000 in the French version and 6,000 in the English version, which was published a year ago). Students are, on average, 25 years old and 30% of learners are women.
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