Why Explore Space? . Specifically, she asked how he could suggest spending billions of dollars on such a project at a time when so many children were starving on Earth. Stuhlinger soon sent the following letter of explanation to Sister Jucunda, along with a copy of "Earthrise," the iconic photograph of Earth taken in 1968 by astronaut William Anders, from the Moon (also embedded in the transcript). Computer program ‘evolves’ music from noise Evolutionary processes in DarwinTunes. Songs are represented as tree-like structures of code. Each generation starts with 100 songs; however, for clarity, it only follows one-fifth of them.
Charlatan A charlatan (also called swindler or mountebank) is a person practicing quackery or some similar confidence trick in order to obtain money, fame or other advantages via some form of pretense or deception. The word comes from French charlatan, a seller of medicines who might advertise his presence with music and an outdoor stage show. The best known of the Parisian charlatans was Tabarin, who set up a stage in the Place Dauphine, Paris in 1618, and whose commedia dell'arte inspired skits and whose farces inspired Molière. Basics of Space Flight: Orbital Mechanics Orbital mechanics, also called flight mechanics, is the study of the motions of artificial satellites and space vehicles moving under the influence of forces such as gravity, atmospheric drag, thrust, etc. Orbital mechanics is a modern offshoot of celestial mechanics which is the study of the motions of natural celestial bodies such as the moon and planets. The root of orbital mechanics can be traced back to the 17th century when mathematician Isaac Newton (1642-1727) put forward his laws of motion and formulated his law of universal gravitation. The engineering applications of orbital mechanics include ascent trajectories, reentry and landing, rendezvous computations, and lunar and interplanetary trajectories. Conic Sections
El Patrón de los Números Primos: Prime Number Patterns by Jason Davies. For each natural number n, we draw a periodic curve starting from the origin, intersecting the x-axis at n and its multiples. The prime numbers are those that have been intersected by only two curves: the prime number itself and one. Below the currently highlighted number, we also show its sum of divisors σ(n), and its aliquot sum s(n) = σ(n) - n, which indicate whether the number is prime, deficient, perfect or abundant. Based on Sobre el patrón de los números primos by Omar E.
Geostationary orbit Geostationary orbits (top view). To an observer on the rotating Earth, both satellites appear stationary in the sky at their respective locations. Geostationary orbits (side view) A 5 × 6 degree view of a part of the geostationary belt, showing several geostationary satellites. Brain Workshop - a Dual N-Back game Introduction - Download - Tutorial - Details & Options - Donate Dual N-Back exercise featured in Brain Workshop was the subject of an April 2008 peer-reviewed scientific study which shows that practicing the Dual N-Back task for 20 minutes 4-5 days per week will improve your working memory (short term memory) and fluid intelligence. This Wired article has a good summary of its benefits.
Lagrange Points of the Earth-Moon System A mechanical system with three objects, say the Earth, Moon and Sun, constitutes a three-body problem. The three-body problem is famous in both mathematics and physics circles, and mathematicians in the 1950s finally managed an elegant proof that it is impossible to solve. However, approximate solutions can be very useful, particularly when the masses of the three objects differ greatly. For the Sun-Earth-Moon system, the Sun's mass is so dominant that it can be treated as a fixed object and the Earth-Moon system treated as a two-body system from the point of view of a reference frame orbiting the Sun with that system. 18th century mathematicians Leonhard Euler and Joseph-Louis Lagrange discovered that there were five special points in this rotating reference frame where a gravitational equilibrium could be maintained.
Tweets vs. Likes: What gets shared on Twitter vs. Facebook? It always strikes me as curious that some posts get a lot of love on Twitter, while others get many more shares on Facebook: What accounts for this difference? Some of it is surely site-dependent: maybe one blogger has a Facebook page but not a Twitter account, while another has these roles reversed. But even on sites maintained by a single author, tweet-to-likes ratios can vary widely from post to post. So what kinds of articles tend to be more popular on Twitter, and which spread more easily on Facebook?
Moon Fact Sheet Bulk parameters Moon Earth Ratio (Moon/Earth) Mass (1024 kg) 0.07342 5.9726 0.0123 Volume (1010 km3) 2.1958 108.321 0.0203 Equatorial radius (km) 1738.1 6378.1 0.2725 Polar radius (km) 1736.0 6356.8 0.2731 Volumetric mean radius (km) 1737.1 6371.0 0.2727 Ellipticity (Flattening) 0.0012 0.00335 0.36 Mean density (kg/m3) 3344 5514 0.606 Surface gravity (m/s2) 1.62 9.80 0.165 Surface acceleration (m/s2) 1.62 9.78 0.166 Escape velocity (km/s) 2.38 11.2 0.213 GM (x 106 km3/s2) 0.0049 0.3986 0.0123 Bond albedo 0.11 0.306 0.360 Visual geometric albedo 0.12 0.367 0.330 Visual magnitude V(1,0) +0.21 -3.86 - Solar irradiance (W/m2) 1367.6 1367.6 1.000 Black-body temperature (K) 270.7 254.3 1.064 Topographic range (km) 16 20 0.800 Moment of inertia (I/MR2) 0.394 0.3308 1.191 J2 (x 10-6) 202.7 1082.63 0.187 Orbital parameters (for orbit about the Earth) Lunar Atmosphere For information on the Earth, see the Earth Fact Sheet. Planetary Fact Table - metric units