Astro 102 Equation

[Mariam Obregon]

Mathis the engine of the universe, driving and dictating all actions, interactions, transformations, and appearances, including yours. Equation-based laws underlie physical systems, and the physical systems astronomers care about are ones composed of stars, planets, galaxies, gases, plasma, strange subatomic particles, dark matter, dark energy, and anything else you might find if you ventured to space. Although all equations are beloved and have their own fan bases, some equations are more fundamental and wide-reaching than others.

Any object with a temperature (which means all objects) emits radiation. The Rayleigh-Jeans Law says that if you know the temperature of the star, planet, or human being, you can find out how much electromagnetic energy it is putting out at any given wavelength. This law explains why the Sun appears yellowish: Its peak radiance is in the yellow-orange part of the visible spectrum. You, on the other hand, peak in the infrared.

Mathematics is the universe's engine, driving and dictating all actions, interactions and transformations. Equation-based laws underlie physical systems. Physical systems astronomers investigate include stars, planets, galaxies, gases, plasma, subatomic particles, dark matter and anything else you might find if you ventured to space.

Astronomy for me is an incredibly fascinating field of study, a challenging subject I love to photograph and one that I am passionate about. To get the best out of my hobby, I have invested in some quality astronomy equipment, completed a number of courses and a diploma of higher education in astronomy. My love for astronomy started in 2005 when I decided to photograph the lunar eclipse. Along with the eclipse I captured a few photos of the Pleiades star cluster which opened my eyes to the wonders in the night sky.

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Scientists expect that, if we discover life on Mars, it will most likely be simple bacterial life and not humanoid aliens like most of the martians you have seen in movies. This does not mean that scientists have completely ruled out the possibility of intelligent life in the Milky Way Galaxy, though. One of the tools that you can use to consider this topic is known as the Drake Equation, after astronomer Frank Drake who proposed it in the early 1960s. With this equation, you can estimate the number of communicating, intelligent civilizations that currently exist in the Milky Way.

Several of these terms have values that we can estimate with some degree of accuracy. For example, we can estimate R* from our observations of star forming regions in the Galaxy. That number appears to be very close to 1 star per year. Also, from our observations of stars with protoplanetary disks and with extrasolar planets, we think that f p is likely 1 or close to 1, too. The rest of the values in the equation require you to either extrapolate using limited information or outright guess.

For n e , we can use the Solar System as a guide. The Earth is in the CHZ. Venus and Mars are either close or in the CHZ depending on the model used. Europa, Ganymede, and Titan are outside of the CHZ, but may have environments that can support life. So, in the Solar System there is definitely one, and maybe more than one, planet (or moon) capable of supporting life. What we still do not know is if our Solar System is common or rare. If it is common, you might estimate say 2 objects per Solar System for n e . For f l , you have to make an educated guess. Scientists studying the origin of life think that, given the right conditions (temperature, presence of water, etc.), life may develop on every Earth-like world, or f l =1 . However, that may be too optimistic, so you might expect that 1 in 10, 1 in 100, or 1 in 1,000,000 develop life. However, if you think that Earth is alone in this regard, it might be as low as 1 in 100,000,000,000. The arguments for assigning values for f i and f c are identical. If you are optimistic, you would assign f i or f c =1 . If you are pessimistic, you would assign f i or f c =1 in 100,000,000,000, or anywhere in between.

The final term, L, is the lifetime of an intelligent, communicating civilization. How do you estimate this value? If you consider Earth, we have only had the technology to communicate using light (e.g., radio or TV) for about 100 years. To estimate L, though, you have to decide how long our civilization will retain this capability. Will civilization end because of war, disease, or some other catastrophe in a few generations? If not, will our civilization last as long as the Sun remains on the Main Sequence? Your estimate may be anywhere from 1,000 years to 5,000,000,000 years. If you fill in values of 1 for all of the parameters for R* through f c , then the equation simplifies to N = L. So, in the optimistic case, your estimate for N will be equal to your estimate for the lifetime of a typical intelligent, communicating civilization.

Given the extent of the Milky Way, if the number N is small, the expected distance between Earth and any communicating civilization will be large. If N is large, the average separation between Earth and any communicating civilization may be small.

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I am currently converting some AstroPy-based Python libraries to Julia and one of them (which is the most important one) is used to calculate the positions of astronomical objects for a given (detector) location and observatory site. I cannot wrap AstroPy because the main purpose of the Julia-port is to make it fast (AstroPy is very slow, at least in this context).

We describe a Bayesian neural network architecture that can accurately learn to predict dynamical (chaotic) instability in compact planetary systems. The network demonstrates surprisingly robust generalization to 5-planet systems.

We describe a technique for converting a deep learning model into an analytic equation, focusing on graph networks. We validate it on injected force laws and Hamiltonians, and then discover a new equation to accurately predict the overdensity of dark matter from its environment.

How striking to think that the first discovery of life elsewhere may come from the light of a distant exoplanet rather than from an object in our own Solar System! But ponder: Seager is talking about a possible biosignature detection within a mere ten years. Are we likely to have unambiguous evidence of life on Mars, Europa or any other nearby object as soon as that?

This puts a lie to those who suggest intelligent aliens would not know the Earth had life because our radio signals are only out to about a 70 light year radius. (With the assumption that the nearest ETI would be much more distant than that).

Earlier, others had made several suggestions for revising the original Drake equation. Ward and Brownlee introduced new factors affecting the probability of life and intelligence. Papagiannis and Mauldin argued separately that the original equation neglects the factor of time, assuming that all factors are relatively unchanged. Dyson emphasized the effect of interstellar expansion and colonization, which could establish technological civilizations in new locations; Shostak and Barnett acknowledged that one star system could seed others. Viewing added that colonies could establish other colonies. Brin proposed three new factors including the velocity of expansion, the lifetimes of the colonies, and the probability of approach or avoidance.

Yes! The Drake equation is simply a means of asking a question. Finding 1,000 other ways of asking the question is perhaps interesting but still worth less than a single datum. We need data, not more questions.

I find it useful to consider that there are two basic hypotheses here, which we may call the Steady State and the Big Bang hypotheses of civilisations around the Galaxy. The Drake equation is based on the Steady State concept: for a long time in the past, and for a long time to come, civilisations have been and will continue to be coming into existence, persisting for a while and then vanishing again. The locations at which they are found are always the same as those at which they originally evolved.

Opposing this is the Big Bang concept: for a long time the Galaxy is devoid of intelligent life, but then one civilisation appears and spreads throughout the Galaxy in a relatively brief period of time (on the order of 100 Myr, or 1% of the age of the Galaxy to date). Thereafter, the locations at which intelligent life is found are almost all colonies, and that life is ubiquitous and permanent.

The pattern therefore suggests not only that our own kind of life (technological civilisation) will produce some kind of successor at a higher level of complexity, but also that there is no reason for industrial civilisation to die out once it has become properly established. Which, I suggest, is once it has become established at a variety of different points in the Solar System, thus is no longer a monoculture.

I wonder here if we can imagine biomasking signals as plausible options, as well. Nick Nielsen, in his blog entry on the session, noted that if we can conceive of a trivial way to mask signals in the small, then this strategy could be imposed in the large by the first civilization advanced enough to develop The Great Silencer as it were.

While masking biosignatures would be more complex, we could envision an advanced civilization taking the liberty of at least obfuscating them on a large scale if there were an ethical reason to do so. In other words, if an advanced enough civilization determined that independent evolution were a moral or ethical imperative, and were certain enough of the finding, they could impose silence on the perceiving cosmos in order to enforce it.

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