Today we will conclude the astronomical tale of how the motion of Mars arguably sparked the origin of modern astronomy and science.  Last week we discussed how Nicolaus Copernicus presented a heliocentric, or Sun-centered, model of the universe with the all the planets, including Earth and Mars, orbiting the Sun.  But Copernicus’ model was not well received because it did not predict the positions of the planets much better than Ptolemy’s geocentric, or Earth-centered, model, and religious influences during the time period also wanted to maintain that the Earth was the center of the univer

This week let’s continue the astronomical tale of how the motion of Mars arguably sparked the origin of modern astronomy and science.  Last week we discussed how Claudius Ptolemy presented in about 150 AD a sophisticated mathematical model to explain why Mars and the other planets, moving around Earth, periodically moved retrograde relative to the background stars.  This Earth-centered model of the universe presented what was imagined to be a true representation of the motion of Mars and the rest of the planets for over a millennium.  As time went on, though, the model was not able to accu

Last week we discussed how Mars periodically exhibits retrograde motion, where the planet moves east to west relative to the background stars instead of its more typical west to east motion. Understanding why Mars undergoes this motion has been a challenge for hundreds of years. One of the first people to present a mathematical theory for the motions of the Sun, Moon, and planets was Claudius Ptolemy, who was thought to have lived from 85 – 165 AD.

The Motion of Mars

Apr 19, 2018

This coming summer in 2018, Mars will be spectacular in our night sky as it outshines all the stars and planets except Venus. It won’t be quite as bright as it was in 2003, but nearly! In honor of this, the next few discussions will be about various topics connected to Mars.

Today let’s conclude our visualization of the size and scale of space by trying to imagine our place in the Universe. To begin, let’s complete our “cosmic address” by noting that we our located in the Milky Way galaxy which is part of a local cluster of galaxies called, unimaginatively, “The Local Group”. There are about 54 galaxies in the Local Group, which also contains the Andromeda Galaxy, a galaxy that is much like our Milky Way galaxy and can be seen with the naked eye in the constellation of Andromeda.

Let’s continue trying to visualize the size and scale of our universe with a discussion about our Milky Way galaxy.  Galaxies are large collections of stars, on average about 100 billion stars, that come in different shapes and compositions.  There are elliptical galaxies (which have basic shapes of spheres or eggs), spiral and barred spiral galaxies (which have a basic shape of a disc), and peculiar galaxies (which have, as their name suggests, irregular shapes).  The galaxy our Sun is part of is a barred spiral galaxy, which means that as you look down on it from above, it sort of looks

This week, let’s continue discussing the size and scale of things in astronomy.  Our Solar System has one Sun, 8 planets, 5 dwarf planets, hundreds of natural satellites, thousands of comets, and hundreds of thousands of minor planets.  It has a basic shape of disc and the Sun at the center.  For this discussion, we are just going to focus on the Sun and the planets.

Last week we began a discussion about the scale of things by talking about how big the Earth is and our size on the Earth.  Today, let’s talk about the Earth and Moon.  The Moon, our companion in space, has a diameter of about 2,100 miles, which means it is about one-fourth the size of the Earth.  Now while the Moon is smaller than the Earth, that is actually big compared to other moons in the Solar System relative to the planets they orbit.  Most of the moons in the Solar System are only about one-hundredth the size of their planet.  Our Moon is so big that it actually stabilizes the rota

The Scale of Space

Mar 15, 2018

I find that when I talk to people about astronomy and space, one of the hardest concepts to understand is the actual scale of things in our Solar System, galaxy, and universe. But this is not wholly unexpected because just every astronomical picture found in the media is depicted with a scale that is either incorrect or not understandable by the viewer. So let's go ahead and talk about the scale of things. First, let's start with the Earth.

The Equinox

Mar 8, 2018

You may have noticed that it is getting more and more difficult to drive east in the morning and west in the evening. The reason is because we are approaching what is called the spring, or vernal, equinox. This year the vernal equinox is March 20th. On the calendar, this is noted as the first day of spring, but this day is special because of what is going on astronomically. As the Earth orbits the Sun in a near perfect circle, it also rotates. This rotation of the Earth is what provides us with day and night, and the time it takes for the Earth to orbit the Sun is our year.