Aleksandar Janjic

Aleksandar Janjic
Technische Universität München | TUM · School of Life Sciences Weihenstephan

About

17
Publications
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Introduction
Trained in bioecology and astronomy at Technical University of Munich. Working on evolutionary ecology and astrobiology. Contact via aleksandar.janjic@tum.de

Publications

Publications (17)
Book
Full-text available
Dieses Buch führt in Fragestellungen der Astrobiologie und Exoökologie ein und vermittelt einen umfassenden Überblick über die aktuellsten Forschungsergebnisse, vergangenen Rückschläge und zukünftigen Missionen der führenden Raumfahrtorganisationen. Unter astrophysikalischen, geo- und bioökologischen Gesichtspunkten werden dem Leser exotische Welte...
Article
The growing scientific interest in the “virus first hypothesis” (VFH) as an early step in the origin of life has practical implications for searches and life detection on future Mars missions. The suite of life-detection methods on future missions could miss important biosignatures because instrument designs currently follow a biased definition of...
Chapter
In diesem Kapitel wird für die breite Leserschaft erörtert, ob und wie die Thermodynamik dazu beitragen kann, das Leben grundlegend zu beschreiben. Statt einzelne Merkmale des Lebens aufzuzählen, werden hier zunächst die Begriffe der Entropie, Emergenz und Komplexität allgemein verständlich herangezogen. Wesentliche Bestandteile dieses Kapitels sin...
Chapter
Bei der klassischen Beschreibung des Lebens werden oft einzelne oder mehrere „Merkmale des Lebens“ aufgezählt, die alle Lebewesen eindeutig von Nicht-Leben abgrenzen sollen (z. B. Stoffwechsel, Vervielfältigung, Wachstum…). In diesem Kapitel wird für die breite Leserschaft erörtert, welche Merkmale besonders häufig in Konzepten anzutreffen sind und...
Chapter
Der Wunsch nach vereinheitlichten Beschreibungen ist insbesondere in der theoretischen Physik anzutreffen, während in der Biologie und bei der Beschreibung des Lebens Vereinheitlichungen meistens nicht angewandt werden. In diesem Kapitel wird allgemein verständlich für eine breite Leserschaft erläutert, was unter einer erweiterten und vereinheitlic...
Book
Das Leben mag uns vertraut erscheinen - eine Ameise lebt, ein Stein nicht, basta! Doch ausgerechnet in der Naturwissenschaft fehlt es bis heute an einer allgemeingültigen Beschreibung, die Lebewesen eindeutig von nicht-lebender Materie abgrenzt. Für jedermann verständlich erläutert dieses kleine Buch, welche Herausforderungen es bei den mittlerweil...
Article
In ecology and conservation biology, the concept of assisted evolution aims at the optimization of the resilience of organisms and populations to changing environmental conditions. What has hardly been considered so far is that this concept is also relevant for future astrobiological research, since in artificial extraterrestrial habitats (e.g., pl...
Chapter
Leben verändert abiotische Bedingungen und hinterlässt mitunter massive Spuren in der Umwelt – sei es durch Bakterien vor Milliarden von Jahren oder durch uns Menschen heute. Die Suche nach solchen Ökosignaturen auf fernen Welten hat bereits begonnen. Doch welche Indikatoren für Leben sind besonders aufschlussreich und welche Welten sollen zuerst u...
Chapter
Viele Wege führen zum Leben – Reaktion für Reaktion werden die abiotischen Grundlagen der allerersten ökologischen Interaktion und ihrer evolutionären Entfaltung entschlüsselt. Doch wie sieht dieses Leben aus und ist es überhaupt möglich, Leben widerspruchsfrei zu definieren? Das kleinstmögliche Leben birgt das Potenzial, alles, was wir über unsere...
Chapter
Raumsonden können verschiedenste Körper unseres Sonnensystems ansteuern und auch mit Erfolg auf ihnen landen. Dabei steht vor allem ihre elektronische Grundausstattung vor gewaltigen Herausforderungen, etwa wegen starker Temperaturschwankungen, den Verhältnissen der Schwerelosigkeit oder hochenergetischer Strahlung unserer Sonne und anderer kosmisc...
Poster
Full-text available
In accordance with Friedmann-Lemaitre-Equation there are three different possibilities of space curvature which can be described mathematically and imparted graphically or analogously (Closed, Openend or Flat Universe). In the attached poster a fourth graphic representation is shown, which is however only graphically derived. Is this sketch descr...
Book
Sollte es Leben in unserem Sonnensystem geben, wird es in diesem Jahrhundert gefunden werden. Mit diesem Buch wird dem Leser der aktuellste Stand der Astrobiologie verständlich vermittelt und über die heutigen und anstehenden Missionen der Raumfahrtbehörden berichtet. Kommen Sie mit auf die Reise von der Entstehung des Lebens, über die Möglichkeite...
Chapter
Extremophile Organismen bewohnen die unwirtlichsten Orte unseres Planeten, und einige könnten extraterrestrische Aufenthalte oder gar interplanetare Reisen erfolgreich überdauern. Sind Sie selbst überhaupt ein Erdling?
Chapter
Viele Wege führen zum Leben – Reaktion für Reaktion werden die abiotischen Grundlagen der allerersten ökologischen Interaktionen entschlüsselt. Das kleinstmögliche Leben birgt indes das Potential, alles, was wir über unsere Erde und ferne Welten zu wissen glauben, größtmöglich zu verändern.
Chapter
Leben verändert abiotische Bedingungen und hinterlässt mitunter massive Spuren in der Umwelt – sei es durch Bakterien vor Milliarden von Jahren oder durch uns Menschen heute. Die Suche nach solchen Ökosignaturen auf fernen Welten hat bereits begonnen.

Questions

Questions (14)
Question
Hi there,
my question concerns a situation in which the law of free fall and the relativity of simultaneity come into play simultaneously.
The general assumptions are as follows:
1. if we let two objects fall at the same time, they will reach the surface at the same time, regardless of their mass (although gravity has a stronger effect on larger masses, inertia is also greater to the same extent).
2. the relativity of simultaneity shows impressively that different observers moving relatively to each other do not have to agree on whether two events really happen at the same time, depending on their reference system.
My question now is, what happens, if we combine both things. A person is standing in a space ship and lets two objects with different masses fall simultaneously through a technical apparatus (atomic clock). In his frame of reference this person has no problem - he sees that both objects arrive at the floor at the same time. But what does an external observer see when the space ship passes? Does he now have the impression that the objects no longer fall onto the surface at the same time, even though the law of free fall implies uniform acceleration? Or must all external observers agree that both objects reach the floor at the same time, because the law of free fall cannot be circumvented? Or is it the case that the external observer could observe that the person in the space ship does not drop the objects at the same time, although the person in the space ship observes that the objects are dropped at the same time?
Question
Dear all,
in accordance with Friedmann-Lemaitre-Equation there are three different possibilities of space curvature which can be described mathematically and imparted graphically or analogously (Closed, Openend or Flat Universe). In the attached poster a fourth graphic representation is shown, which is however only graphically derived.
Is this sketch describable within Friedmann-Lemaitre-Equations? How can we interpret this sketch? A Universe that is truly infinite, although it has a defined start and a defined end point?
What would be a 3-Dimensional mathematical object to describe the plot (closed hypertorus, while closed means without a connection in the center?). And what numbers for curvature parameter k and density Parameter Ω make sense for this sketch?
I have created this plot purely graphically and wonder whether a mathematical interpretation of such a shaped space-time is possible, or whether it inevitably leads to paradoxes and is thus a graphic that can be drawn abstractly, but ultimately makes no mathematical sense.
Thank you!
Question
Black holes cause event horizons, depending on the mass compressed into a narrow space (point?). From this analogy, could the quantity (mass?) of information in a narrow space lead to an insight horizon, which is why we cannot see into it from the outside and therefore no 100 percent simulation of a real system filled with a lot of information can succeed?
The more factors we use to model a system, the closer we get to reality (e.g. ecosystems) - but this process is asymptotic (reality is asymptotically approximated with every additional correct factor). Interestingly, it also seems to us that an object red-shifts into infinity when it approaches a black hole (also asymptotically).
Can we learn anything from this analogy? And if so, what?
Question
Hey there,
i just edited some random empiric dataset and i saw that the number 396 induces interesting percent-outcomes.
I set 396 as 100% and every other number - thats the observation - leads to a periodic percentage after comma (in relation to 396).
Examples (396 = 100%).
1 = 0,25252525period % (of 396)
2 = 0,5050505period %
...
8 = 2,02020202period %
....
35 = 8,83838383period %
...
59 = 14,898989period %
...
...
...
206 = 52,020202period %
What is the reason for this - always periodic - outcomes or how is this called in mathematics? And can you give me other numbers which show this effect?
Greets
Aleks
Question
Dear All,
not only in all known to me textbooks, but also in my academic environment, plants are only discussed as carbon sinks and therefore planting forests is said to be one of the main strategies to reverse or reduce some effects of climate change.
But: About 10 years ago a german team from MPI published - and that seemed to be a shock for some climate researchers - that plants (especially forests) are able to produce tremendous amounts of methane under "normal" aerobic conditions autonomously (1). There were even attempts to link the ending phase of the ice ages with forest growth in the way that besides volcanic or solar activity forests were responsible for the warm up (and not vice versa).
Still in any lectures at my institution only common methane sources (microbes, anaerobic environments as bogs and swamps, cattles, humans,...) are discussed with students while - as said - plants are only considered as carbon sinks.
How so? Do you know something about the latest discoveries in this field (maybe i missed some relevant publications)? Are plants excluded as methane sources because of new investigations? Or is it an open (and not well known) problem that is not recognized broadly by environmental scientists?
Thank you
(1) Keppler F, Hamilton JTG, Brass M et al (2006) Methane emissions from terrestrial plants under aerobic conditions. Nature 439, 187-191.
Question
Dear All,
not only in our university, but almost in all well known to me lectures about Dark Matter, MACHOs (Massive Astrophysical Compact Halo Objects) are rather incidentally discussed while candidates as WIMPs, Axions or Sterile Neutrinos dominate the talks.
Is this - with nowadays knowledge and theoretical assumptions - justified?
With the description of a great abundance of primordial black holes MACHOs do serve a hypothetical answer for almost any questions like rotation curves, radial velocitiy, intermediate black holes, missing-satellite-problem, too-big-to-fail-problem, ...
Of course it is a highly speculative topic. BUT the WIMPs are too (if not even more). So shouldn't we - in accordance with the Principle of Occam's razor - favor MACHOs instead, because they are able to solve a lot of problems at once and at the same time we don't need to extend the Standard Model for introducing them?
Why do WIMPs and particle-like entities dominate? Did i miss a hint (for example some fundamental advantages of this models?). Or is it a general problem ultimately based on ignorance to a great extent?
Thank you
Question
Our knowledge from direct observations about far away regions of the universe is limited due to the observation horizon. If the Universe expands and the acceleration gets faster and faster, isn't it a inevitably consequence that everywhere and in every direction subuniverses are arising from the view of hypothetical observers in any space-time-region (so that every subsystem is not causally connected to another subsystem for an observer, because he just cannot gain information about the other system)?
I tried to imagine it with the analogy of black holes: If i could sit in one of them, and you in another, our observations would again be limited by the event horizon of our black hole - we couldn't know anything about each other or even about the existence of the other just from observations. Isn't this a proper definition of a disconnected system from the view of an observer? And in the case of expansion and the observation horizon: a disconnected universe?
Lastly, another question: What is the connection between the nature of time and our observation horizon? If we look deep in space our look in the past is limited. But if space expands in all directions with time shouldn't the same be true for the future? Is our look into the future limited, because the acceleration of speed expansion is already greater than the speed of light? Or is this thought a logical fault?
Thanks 

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Projects

Project (1)
Project
The terms of self-organisation and self-ordering are used either synonymously or as qualitatively different terms, depending on the author. In this project we use a computer simulation to investigate whether self-organizing structures can emerge from self-ordering ones, if the latter are complex enough. We hope for a more precise interpretation of these terms in the context of the Origin of Life debate. Purely intuitively, we would assume that self-organization does not represent a qualitative difference to self-order, but is an inevitable consequence above a certain complexity threshold. We are aware that this hypothesis is difficult to falsify, since one could always claim that there is not yet enough complexity in the respective system. A solution to this conceptual problem and a corresponding implementation are therefore the focus of our attention at the beginning of this project.