A Spaceplane is any vehicle that operates as a spacecraft in space and as an aircraft within Earth’s atmosphere. The experimental X-15 was the first operational spaceplane after its flight in 1963 when pilot Joseph Walker exceeded 100km in altitude. Another notable group of spaceplanes are the space shuttles, both the American space shuttle program which flew 135 mission over 30 years and the Soviet Buran shuttle program which flew one unmanned test flight in 1988 before being cancelled in 1993. Both the X-15 and the 2004 SpaceShipOne, the first commercial spaceplane, took off horizontally from a “mother ship” which took them high into Earth’s atmosphere. The Space Shuttle, Buran shuttle, and the 2010 Boeing X-37 took off vertically with rocket assistance, reentering by gliding through the atmosphere.
Monthly Archives: August 2012
If there is a doomsday, this is it. A major aspect of cosmology and astronomy is that the universe is expanding. “Expanding” in this sense doesn’t necessarily mean that the universe it getting bigger, but that everything is accelerating away from everything else. Everything is accelerating from everything else. EVERYTHING. Planets that make up the solar system, the rocks that make up the rocky planets and asteroids, the chemicals that make up the rocks, the atoms that make up the chemicals and the fundamental particles that make up the atoms. Everything is getting farther apart, and is moving away from everything else faster and faster every second. The Big Rip hypothesis was postulated in 2003 and relies on the value of a variable, w, to determine the time the universe has left. In an example where w=-1.5, the universe has about 22 billion years left before it starts to get ripped apart. So how long do we really have? w is probably, according to the authors, closer to -1, and if w is exactly -1 the Big Rip will never happen. So, you have at least 22 billion years, and probably far longer, to worry.
A neutron star is the collapsed remains of a massive star, between 8 and 40 times more massive than the sun. They are comprised, as their name implies, almost entirely of neurons. Neutron stars are extremely small, but contain between about 1.5 to 3 solar masses, so they are extremely dense. Neutron stars are so dense that one cubic millimeter of neutron star material can weigh upwards of 80,000 metric tons, or about as much as the population of Helsinki, Finland. There are also many varieties of neutron star, such as magnetars, which have magnetic fields strong enough to destroy human tissue (due to the magnetic properties of water) from 1000km away. Finally there are the hypothetical quark stars, which are made mostly of a quark plasma created from neutron matter under heavy pressure.
If Earth were to be replaced by an Earth-mass black hole, almost nothing in the universe would change. It wouldn’t start sucking things up, there would be no major gravitational disturbances, nothing. All that would happen is that anything that passed through a region the size of a peanut would be absorbed into the black hole, and anything that passed nearby would be distorted. All objects have an event horizon (the surface of a black hole), but most objects are far larger than their event horizon (a black hole with Earth’s mass is about the size of a peanut). Black holes also have something called a photon sphere, where photons (light waves/particles) orbit the black hole. Finally, if you were to try and fall into a black hole (for science of course) you would experience a process known as spaghettification. Since, as you approach the black hole, the parts of your body closest to the black hole are being pulled harder by gravity than those far away, you will be stretched, slowly are first but then more quickly, until all of your body is within the event horizon. What happens then? Nobody knows. The current mathematical models used in physics cannot describe what happens within the event horizon of the black hole.
…Neptune was discovered in 1846, and there seemed to be no more reason to worry. Then a guy named Clyde came along. In 1930 Clyde Tombaugh discovered a rocky body beyond the orbit of Neptune. Named Pluto late in March 1930, the planet was originally thought to have a mass similar to that of the Earth, but eventually more accurate estimate revised this to smaller and smaller amounts, until a mass of .2% of Earth’s was settled upon. Again, as with the “forgotten four”, Vesta, Juno, Ceres and Pallas, more and more bodies in Pluto’s region of space were found. Some of these bodies were given special names like Eris, Makemake, Haumea, Sedna, Chaos, Varuna, Quaoar and Typhon, among many other trans-Neptunian “planets”. In August 2006 the International Astronomical Union (IAU) put together a definition of a planet as an object that 1) orbits the sun, 2) has a nearly spherical shape and 3) has cleared its neighborhood of debris. The “demotion” of Pluto from planet to dwarf planet was simply the result of not having a formal definition of what a planet is. The five official dwarf planets are: Ceres, Pluto, Haumea, Makemake and Eris. Finally, nineteen moons are large enough to be classified as planets or dwarf planets, should they orbit the sun. They are: Ganymede, Titan, Callisto, Io, the Moon, Europa, Triton, Titania, Rhea, Oberon, Iapetus, Charon, Umbriel, Ariel, Dione, Tethys, Enceladus, Miranda and Proteus.
Planet comes from the ancient Greek astēr planētēs, or wandering star. Back in that period of time it would have been reasonable to call them this, since the only way to observe them was with the naked eye. This method of observation, the Hellenistic astronomer (among other things) Ptolemy created a list of the seven planets, which then included (in order of closest to furthest away) the Moon, Mercury, Venus, the Sun, Mars, Jupiter and Saturn. As the heliocentric model gained favor the Sun and Moon stopped being planets and the Earth became one, thus, a planet became a body that orbited the Sun. As astronomers looked, they found more planets (thanks to telescopes). Eventually, Uranus and four other, forgotten, planets were discovered. Those four planets were Vesta, Juno, Ceres and Pallas, and they were found in the gap between Mars and Jupiter. In the mid-1800’s, more and more “planets” like the “forgotten four” had been found. They all, including the “forgotten four”, were substantially smaller than any other planet that had been observed, and were removed from the list of planets and were classified as asteroids. Neptune was discovered in 1846, and there seemed to be no more reason to worry.