Interesting science facts - Space & astronomy

Term "spacetime" was first used by Albert Einstein in his paper on a "Special theory of relativity", in which he proposed that space and time should be combined into a single construct known as "spacetime".

Word astronomy comes from two Greek words "astron" meaning star and "nomos" meaning law, and would basically mean law of the stars.

The defining feature of every black hole is the so called "event horizon". Event horizon is a surface in spacetime that marks a point of no return, and once an object crosses this surface, it cannot return to the other side.

In theory, there is no smallest size for a black hole.

Almost 90% of all the incoming cosmic ray particles are protons.

Dark matter is matter that is undetectable by its emitted radiation, and its presence can be inferred from gravitational effects on visible matter. The dark matter component has much more mass than the "visible" component of the universe.

Each galaxy consists of stars and stellar remnants, an interstellar medium of gas and dust, and dark matter. Dark matter account for around 90% of the mass of most galaxies.

There are probably more than 100 billion galaxies in the observable universe. Galaxies come in three main types: ellipticals, spirals, and irregulars.

Nebula is an interstellar cloud of dust, hydrogen gas and plasma. Some nebulae are formed as the result of supernova explosions.

Extrasolar planets, or sometimes called exoplanets are planets beyond our solar system, orbiting a star other than our Sun.

Big bang theory is the most common theory of Universe origin. According to this theory universe has expanded some 12-14 billions years ago from a primordial hot and dense initial condition at some finite time in the past, and continues to expand to this day.

Asteroids are space bodies primarily found in the inner Solar System — that are smaller than planets but larger than meteoroids, with the exclusion of comets.

Comets are small Solar System Bodies that orbit the Sun and once close enough to the Sun, exhibit a visible coma (atmosphere) or a tail — as a result of solar radiation upon the comet's nucleus.

Meteor is visible part of the meteoroid that enters Earth's atmosphere. Once meteor reaches the ground it is called a meteorite.

Jupiter is the largest planet within our Solar system, primarily composed of hydrogen with a small proportion of helium.

Saturn is the second largest planet in Solar system. It has unique system of surrounding rings, consisting mostly of ice particles with a smaller amount of rocky debris and dust.

Evidence suggests that planet Mars was once significantly more habitable than it is today, but whether living organisms ever existed there is still unclear.

Venus is the hottest planet in our solar system with surface temperatures of over 460 °C.

Until 2006 Pluto was considered as one of our solar system's planets, but since 2006 it is classified into new category called "dwarf planets".

Mercury is the smallest planet in our solar system, it is also planet the closest to Sun.

There are There are three main types of telescopes:

* The refracting telescope which uses lenses to form an image.
* The reflecting telescope which uses an arrangement of mirrors to form an image.
* The catadioptric telescope which uses mirrors combined with lenses—either in front of the mirror or somewhere within the optical path—to form an image.

Moon is the Earth's only natural satellite and the fifth largest natural satellite in the Solar System.

Millions of people worldwide believe they have seen UFOs, and tens of thousands of UFO reports have been cataloged.

Popular phrase "Houston we have a problem" comes from the words of Commander James A. Lovell, commanding officer at the infamous Apollo 13 who during the radio transmission with NASA said: "Houston, we've had a problem".

NASA (National Aeronautics and Space Administration) was established on July 29, 1958. NASA's headquarters is located in Washington, D.C.