Catégorie : Physics

How do big telescopes look through the atmosphere – Adaptative Optics 101

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Continuing my series of post covering my talk from last Christmas about the use of lasers in space and astronomy. The topic today is adaptative optics. I’ll explain the reason why we need it, and how it works in simple terms. Enjoy. No surprise: telescopes are the main tool of astronomers. Since Newton, we have built countless telescopes of various sizes and shapes. And lately, we even send them to space. We have Hubble, the JSWT for the more famous, and a lot of other space telescopes less known. But why sending them to space? After all, space is difficult. …

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What is the difference between a regular lamp and a laser? A brief history of Optics and Lasers

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So this post and a bunch after this one are from a talk I presented at the end December on the topic of lasers in space and astronomy. The target the audience was members from astronomy groups in the region with some knowledge of optics but not necessarily lasers and the curious people that might be interested but have a physics background from high school. I tried to make it interesting for a wide audience, and I would say that it is accessible to some degree to someone in high school, maybe earlier? Anyway, the goal was to be entertaining, …

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Diffraction patterns in astronomical imaging

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The first image from the James Webb Space Telescope (JWST) was uncover a few days ago [1]. This is truely an incredible image, showing the galactic cluster SMACS 0723, which is slowly becoming the de-facto target for newly deployed space telescopes as it was imaged by Hubble, Planck and Chandra before JWST. This image in particular took the JWST 12.5 hours of exposure to be able to see these objects as they are so dim in the sky. The best way to see how much of an achievement this is, is to compare it to the previous picture, taken by …

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Digital photonics and laser lightning rods from AKL22

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I was at AKL 22 a couple of weeks ago: the international laser technology congress at Aachen, Germany. I was present for the interesting technology conference and the live presentations at Fraunhofer ILT. I have to say that after 2 years of Covid and only being able to assist to virtual conferences if available was a breath of fresh air. Virtual events are nice and you can still learn a few things, but physical events are something else. You are invested in what you hear and there is less distraction than in the office. The best part is that you …

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SpaceX lost 38 Starlink Satellites due to a CME

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I wrote last year about the effect of CME on the thermospheric density and what are the effects on satellites inside the thermosphere, typically at the altitude of the Starlink satellites. You can find this post here. Solar cycle 25 is well underway now, and from the look of it, it looks like the sun is in a strong unrest. It might be a very active solar cycle, that some predictions made put it at the same level than the cycle 20, which peaked in the 70’s. Little known fact about the 20th solar cycle: one of the strongest storm …

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Laser physics: gain medium and population inversion

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Continuing the series on lasers. In the first part, I went fast over plenty of concepts and left others on the side because they were not necessary to get a global understanding of lasers. Here, I want to get a little deeper in some specific concepts. I want to talk more in details about the gain medium of a laser and why population inversion is a vital concept. For now, I have been relatively simple on the gain medium characteristics… I have considered a simple material with two atomic energy levels, and I have been assuming that the transition is …

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Checking dimensions in equations

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Short post this week. I want to talk about a simple concept that is extremely useful in physics and other fields of applied science. Especially those fields working with equations to calculate anything that has a physical meaning to it, like a speed, a voltage, a weight.. As a physics student, our teachers would usually spend a few minutes talking about how it is extremely important to check dimensions. Back then, I was listening and not really thinking how that would help me concretely to find the answer to the problem they were giving us. I would always be puzzled …

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An introduction on laser physics

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So I want to start a series of posts that will focus mostly on lasers, what they are, how they work, what are the most important elements, etc… It can still evolve. Some prerequisites first: To fully understand what I will write, here, it definitely helps to be familiar with a few concepts and bases from electromagnetism and optics, obviously. I’ll try to explain these concepts along the way of course. Nevertheless, even if you don’t have the necessary background, keep reading. I’ll try to keep it simple and limit the mathematics to a minimum. It’s no surprise that lasers …

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Comment diriger la foudre avec un laser...

Mario Tonin0 commentaire

Climate change is a mess. It’s hotter in some places, colder in other, and in general, severe weather is intensifying with longer droughts, heavier rainfalls and stronger storms. This problem, caused mostly by our method of generation of energy relying on burning fuel and releasing carbon dioxide in the air has a few solutions, among them: the wind turbine to harvest wind energy and generate clean electricity. But, here is a slight problem. A few days ago, I stumbled upon an article[1] explaining how wind turbines are actually at risk of severe damages when thunderstorms occur. The issue here is …

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