Category Archives: Terrestrials
includes Mercury, Venus, Earth, Mars
During class today, I talked about tides and how there is a great deal of misinformation out there.
My favorite websites for the astronomical explanation of tides are:
- A rigorously correct but a tiny bit snarky treatment – it’s my favorite: Tidal Misconceptions by Dr. Donald E. Simanek
- One of the links from the page above is a much more mathematically rigorous treatment with equations and animations: Tides and centrifugal force by Paolo Sirtoli
- National Oceanic and Atmospheric Administration (NOAA) Ocean Service Education Tides and Water Levels page
- Dr. Sten Odenwald’s Ask an Astronomer :: 10 FAQ about Lunar Tides
The YouTube videos of the awesome spring and neap tides in Clovelly.
In class today (Wednesday), I showed some of the lunar landing footage available to we, denizens of the Internet, for FREE! NASA is a public entity and as such, happily will show us many awesome things and has given us the Apollo Lunar Surface Journal (ALSJ). Much of the text was written by former astronauts from the missions themselves and many of the best/crowd-favorite clips provide some context.
Whilst meandering the internet last summer looking for great astronaut videos to use in outreach, I came across this great website: Top 10: Videos From the Moon Landings (from How It Works Magazine). I’d already found some of them in browsing the COPIOUS video clips in the ALSJ but this website really does have some of the very best :) My favorites almost always involve the Apollo 17 mission it seems (this is a FANTASTIC Wikipedia page – check out the multimedia at the end!!)… But I suppose that one was the one with the geologist and he seems a bit more jovial than the others sometimes :)
In the end, don’t let anyone tell you we didn’t land on the Moon. You can find “Bad Astronomer” Dr. Phil Plait’s debunking here along with a page of several links to debunkers (and deniers!). You can find the Mythbusters episode debunking here (never mind – you have to find that yourself, they keep taking the versions I know down). You can find an excellent debunking website called clavius.org here.
So I read this article and I had to share it with you – I think it’s very good :)
Article: Spring Arrives With Equinox Tuesday, Earliest in Over a Century
by Joe Rao, SPACE.com Skywatching Columnist
As an introduction, here in Nashville, we’ve been experiencing a really mild spring – personally, I’m pretty happy about it because I go observing with the lab students a lot and it’s been so nice to not have to bundle up ;) Thus we’ve been having an early spring meteorologically.
But let’s think about what the start of spring means ASTRONOMICALLY. The start of spring is technically the date of the vernal equinox which technically is when the Sun’s position in the sky goes from being in the southern celestial hemisphere to being in the northern celestial hemisphere. You can see this with Stellarium!! Plus you can see how the actual location of the equinox in the sky (comparing it to the constellations) changes over time – this is called the precession of the equinoxes and it is why we are entering the Age of Aquarius!
Here’s a lovely graph from Wolfram Alpha that shows the date of the vernal (spring) equinox for certain time periods (see axes ;) ):
Note that we’re bottoming out for our cycle in the left graph (stupid axes if you ask me so it is kinda hard to see). The short-period cyclic nature on the left shows the “resetting” every leap year and then the big jumps on the right plot show the effect of not having a leap year during century years (i.e., 1800, 1900, 2100, 2200) unless those years are divisible by 400 (i.e., 2000). To learn more about this (and to see a better graph), go to Wikipedia :) Dudes, on Wikipedia, I learned about the Iranian calendar which has 8 leap days in every 33 year time period – it’s more accurate :)
Anyway, the aforementioned article is a good article – Dr. G approved! ;)
It’s unfortunate that these days, “global warming” is such a dirty word; tis a fascinating topic and one we’ll be investigating a bit during our course (in Unit 3 when we talk about the rocky planets). Despite the fact we’ll be looking at this more later, I HAVE to post about two things that I found yesterday that remind me of global warming issues.
1. A Bad Astronomy blog post about new research about the cause of the Little Ice Age also linked to some new data put out by NASA stating the Sun cannot be the cause of global warming. This claim that the Sun’s natural increase in temperature over time (increase is true) is the cause of what we are calling “global warming” is one of the big drums that climate change deniers keep beating on. But it’s simply not true. We just go to the data (like the folks at NASA did in the above article). We’ll talk about it more in class.
2. One of my sisters is a landscape designer and she provided a link to the newly updated “Plant Hardiness” map published by the USDA. It shows that the hardiness zones (basically what kinds of plants you can put outdoors) are shifting northerly a bit.
However, they are careful to put this statement on their website:
“Climate changes are usually based on trends in overall average temperatures recorded over 50-100 years. Because the USDA PHZM represents 30-year averages of what are essentially extreme weather events (the coldest temperature of the year), changes in zones are not reliable evidence of whether there has been global warming.”
There are other factors in the shift, like better data (more coverage, more accurate) available now, but regardless, it seems mighty interesting to me :)