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Category Archives: Short Questions

Sometimes you have a question that has a simple answer, and you’re not interested in all the extra background info. This page is full of short no-nonsense answers, for researchers on the go. Any extra background info will be referenced by a link. I guarantee, not one single answer will take more than a single paragraph!

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What is a Nebula?

Urban Astronomer avatarPosted on 6 May, 2013 by Allen Versfeld

“Nebula” is the Latin word for cloud.  It was originally used to describe anything in the night sky that had a cloudy or diffuse appearance, and that wasn’t a comet.  Early in the 20th Century, however, it was discovered that some of these nebulae were actually “island universes” (galaxies or globular clusters).  Since then, the word refers to specific types of objects: Planetary nebulae are usually spherical and are the expanding shells of material ejected from dying stars.  They get … Continue reading →

Posted in Astronomy, Questions and Answers, Short Questions | Leave a reply

Why don’t scientists believe in UFO’s?

Urban Astronomer avatarPosted on 30 Apr, 2013 by Allen Versfeld4 Jun, 2016

A lack of any convincing evidence, mainly.  There have been countless thousands of reports of UFO’s over the last century, but most can be easily explained by natural phenomena or known human activity.  For example, the sighting of a mysterious spinning spiral in the sky above Norway turned out to be a malfunctioning rocket spinning out of control.  Other cases turn out to be the planet Venus (“There’s something hovering above the horizon, as bright as an aeroplane’s landing lights”), … Continue reading →

Posted in Astronomy, Bad Science, UFO's and Modern Myths, Questions and Answers, Short Questions | Leave a reply

What is gravity?

Urban Astronomer avatarPosted on 30 Apr, 2013 by Allen Versfeld

Gravity is the force that attracts objects with mass towards each other.  On Earth, it is what brings us back to the ground if we jump upwards.  In space, it is what makes the Moon orbit the Earth, what makes the Earth and other planets orbit the Sun, and what makes the Sun and stars orbit the centre of the galaxy.  According to physicists, there are only four forces in the universe, and gravity is the weakest by a ridiculously … Continue reading →

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What is a supernova?

Urban Astronomer avatarPosted on 30 Apr, 2013 by Allen Versfeld

  A supernova explosion is one of the most powerful releases of energy in the universe.  When the largest stars run out of fuel and collapse, the implosion of their core rebounds with such power that the resulting explosion outshines entire galaxies for several weeks.  All that remains is a tiny dense neutron star, surrounded by an expanding cloud of ultra-hot glowing gas which we see as a beautiful nebula.  If the star was particularly massive, then the remains of … Continue reading →

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What is dark matter?

Urban Astronomer avatarPosted on 30 Apr, 2013 by Allen Versfeld

  Dark matter is the name used for the material out in the universe which we cannot see, but can detect through it’s gravitational influence.  When we look at galaxies, we can see a lot of matter in the form of stars, gas and dust.  We can also see how the stars within those galaxies are moving in their orbits around the galactic core.  The laws of physics tell us that these orbits should be at certain speeds, depending on … Continue reading →

Posted in Astronomy, Questions and Answers, Short Questions | Leave a reply

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