Greetings!
Hope everyone is having a good 2010. And welcome to the many new subscribers; not sure how you found out about this list, but thanks for joining. Before we turn to the space (and math) news, a quick note about events:
* Boston Area readers: I will be giving a public talk at Harvard on Thursday, Sept. 16, 7:30pm; more info and directions at their Monthly Observatory Nights page. Hope to see you there.
* Elementary teachers and parents: I’ve now visited more than 100 elementary schools (see list), but I still have openings for this Fall if anyone is interested. See how you can get a “free visit” on my events page; note that I’ve revamped my policy for out-of-Colorado visits, so it should now be easier for those to be free as well.
Now, on to our news. The contents for this e-mail:
1. THIS WEEK: Planets and Perseids
2. Kepler Mission Update
3. Global Warming Still in the News
4. Video Math Reviews
5. Please Support the Nation Center for Earth and Space Science Education
As always, I welcome comments!
Best wishes,
Jeff
1. THIS WEEK: Planets and Perseids
On Thursday evening (Aug. 12), we have a rare sky “double treat”: An early evening alignment of the crescent moon with the planets Venus, Saturn, and Mars in the western sky, followed by the annual Perseid meteor shower. No equipment needed to see these events — just your eyes and clear skies. For more information, see this NASA Science News piece, or Larry Sessions’ North American Skies e-mails, or the EarthSky 2010 meteor shower guide.
2. Kepler Mission Update
Thanks to the amazing discoveries of the past 15 years, we now know of more than 400 planets orbiting stars besides our Sun. So far, however, all of these planets are considerably larger than Earth. Do planets the size of Earth exist? Do they have Earth-like orbits that could be indicative of habitability? The answers to these questions should be forthcoming over the next few years from the Kepler mission. Kepler’s first planet discoveries were announced in January. Since that time, word has leaked out of hundreds of planet “candidates,” including some the size of Earth or smaller. However, these “candidates” still need to be confirmed, which you can understand as follows: Kepler searches for planets by looking for “transits” in which an orbiting planet passes in front of its star, causing a tiny drop in the star’s brightness. A typical transit lasts only a few hours, and occurs only once per orbit; thus, for example, an alien civilization looking at our solar system (from just the right angle) would see a dip in the Sun’s brightness only once a year as Earth passed in front of it. Because other things besides planets can cause small changes in a star’s brightness, scientists can be confident of a planet detection only after observing at least three, perfectly timed dips. The “candidates” have not yet been seen these three (or more) times, which is why they are not yet confirmed. Moreover, a planet in a year-long orbit will take at least 3 years to confirm, which is why we need a bit of patience. Still, it seems almost inevitable that, within the next 3 to 5 years, we will finally know for sure whether there are other Earth-size planets in Earth-like orbits. I’m betting the answer will be yes…
For Classroom Discussion:
* What is a transit? Do we ever see transits in our own solar system? (Answer: A transit is when a planet passes in front of its star as seen from our vantage point on Earth. We see occasional transits of Mercury and Venus; the next Venus transit will be in 2012. We cannot see transits of any other planets in our solar system, since they orbit beyond us and therefore never pass in front of the Sun from our vantage point.)
* Can we see transits for all planets around other stars? (Answer: No; a planet’s orbit must be aligned just right in order for it to pass in front of its star as seen by us. The vast majority of planets will be in orbits that are inclined relative to our line-of-sight, and hence cannot produce transits.)
* If transits are rare, how can Kepler detect them? (Answer: By watching a LOT of stars. Kepler is monitoring the brightnesses of approximately 100,000 stars. Therefore, even if only 1 in 1000 has a planet oriented the right way for us to detect it, we’d find 100 planets. The actual number will likely be much higher, for a variety of reasons you can read about on the Kepler web site.)*. What will it mean to detect Earth-like planets around other stars? (Answer: This is a philosophical question, well worth discussion. Here is a useful quote for discussion: “Do there exist many worlds, or is there but a single world? This is one of the most noble and exalted questions in the study of Nature.” — Saint Albertus Magnus (1206-1280); he was almost certainly using the word “world” to mean a place like Earth.)
3. Global Warming Still in the News
A few months ago, the unusually cold weather in the eastern U.S. caused many people to claim it was proof that global warming wasn’t real. Now, in the hot summer, other people are making the opposite argument. Both are equally wrong, because a single season tells us nothing about a long-term trend. So I’ll just state it again: Despite all the manufactured controversy you hear in the news, the basic science of this issue comes down to this: Earth is livable only because of a natural form of global warming — caused by naturally occurring carbon dioxide in our atmosphere — that makes Earth about 54°F warmer than it would be otherwise. In other words, without this natural “greenhouse effect” caused by atmospheric carbon dioxide, our planet would be a frozen wasteland. Venus also has a natural greenhouse effect — but there, because Venus has so much more atmospheric carbon dioxide than Earth, the greenhouse effect raises the temperature to an astonishing 880°F. Clearly, while the greenhouse effect is a very good thing for Earth, Venus is proof that it is possible to have too much of a good thing. So as we continue to add carbon dioxide to the atmosphere, ask yourself: What level of risk are you willing to take with the system that makes our lives possible? For more details, please see my global warming primer.
For Classroom Discussion:
* What is the difference between weather and climate? (Answer: Weather refers to the ever-varying combination of winds, clouds, temperature, and pressure that we live with day-to-day. Climate is the long-term average of weather over many years — typically, scientists think of climate only over periods of at least a couple of decades.)
* What can the weather during a single year tell us about climate change? (Answer: Nothing; a single year is not climate, so you must look at many years to see if there is any noticeable climate change.)
4. Video Math Reviews
For those of you teaching high school or college courses in math or science, Megan Donahue and I have just completed a set of video tutorials on basic math topics, which you’ll find posted on the BigKidScience YouTube site. (We also have fully developed tutorials based on these videos, but those are available only to instructors using the Mastering Astronomy web site.)
5. Please Support the National Center for Earth and Space Science Education
If you are interested in supporting great educational programs related to the topics I discuss in these e-mails, please consider supporting the National Center for Earth and Space Science Education. Among many other projects, this organization is responsible for the building of the Voyage scale model solar systems that you’ve heard me talk about many times. It is led by my friend Jeff Goldstein, a master educator who has won numerous prestigious awards. In these difficult economic times, your help would be very much appreciated. (Please note that I have absolutely no financial interest in this organization whatsoever, other than offering my own support to it.)
Thanks so much for your time!