WHAT CAME BEFORE THE BIG BANG?
There was no before the Big Bang—the Big Bang created both time and space as we know it. At the moment of the Big Bang, everything in the physical universe expanded from a singularity: a point of infinite heat and…
WHAT THE ORIGIN OF THE UNIVERSE? WHAT HAPPENED DURING THE BIG BANG?
When we look up at a starry sky on a clear night, we can’t help but ask ourselves: Where did it all come from? How did it all begin? What’s the origin of the universe? Modern cosmologists attempt to answer…
IF ASTEROID 99942 APOPHIS EVER STRIKES EARTH, HOW BIG WOULD THE CRATER BE?
If the near-Earth asteroid 99942 Apophis ever strikes Earth, how big would the crater be? Apophis (formerly 2004 MN4) ranks at the top of the worrisome-asteroid list. On April 13, 2029 (yes, that will be a Friday the 13th), it…
HOW MUCH SPACE DEBRIS FALLS INTO EARTH ATMOSPHERE EVERY YEAR?
Has anyone ever calculated the combined tonnage of meteroids and space debris falling into our atmosphere yearly? Yes, but it’s hard because different methods are needed for different particle sizes. Ground radar and exposed spacecraft surfaces are best for detecting…
HOW LARGE AN ASTEROID COULD A PERSON JUMP OFF?
How large an asteroid could a person jump off? This interesting question goes back to 1952 or even earlier. It turns out that the asteroid must be no bigger than 3.9 v(ρe / ρ) kilometers in diameter, where ρ is…
WHY ARE KUIPER BELT DISCOVERIES MADE AT APHELION?
Why is it that so many of the recent Kuiper Belt discoveries — including the “10th planet,” 2003 UB313 — have been made while the objects are at aphelion? Timing and luck. Objects that orbit the Sun spend most of their…
WHY DO COMETS HAVE TAILS?
WHY DO COMETS HAVE TAILS? Comets develop tails as they approach perihelion—the place in their orbits when they are closest to the Sun. The Sun’s heat vaporizes some of the comet’s material, releasing dust particles that were trapped in the ice.…
WHAT IS A METEOR SHOWER?
Meteoroids are rocky or metallic objects that can range in size from small grains to several-kilogram bodies. Most meteoroids are pieces that have been blown or knocked off larger objects, such as comets and asteroids. Therefore, it is not uncommon…
WHAT ARE THEY AND WHERE DO THEY COME FROM?
WHAT ARE THEY? Asteroids are rocky objects primarily found in the asteroid belt, a region of the solar system that lies more than 2 ½ times as far from the Sun as Earth does, between the orbits of Mars and Jupiter.…
COMETS: WHAT ARE THEY? WHERE DO THEY COME FROM?
WHAT ARE COMETS? Like asteroids, comets are suspected to be remnants of planet formation in the Solar System about 4.6 billion years ago. But while asteroids are generally comprised of rock and metal, comets are more akin to dirty snowballs. They…