We discussed the seasonal change of summer to winter when I was in school and the years required to make the seasonal change from summer to winter and back to summer was 27,000 years.
Is this the number of years for this change and is this the same time period for a polarity shift of the poles?
Sam, the phenomenon you are referring to is known as precession, where the axis of rotation “wobbles” with a specific interval.
You are correct in that this cycle is in the neighborhood of 26,000 – 27,000 years.
Keep in mind, not only does the Earth’s rotational axis “wobble”, the amount of tilt also varies in a cyclic pattern from around 22 degrees to almost 25 degrees.
There are some theories that use the axial tilt and axial precession (along with a few other orbital factors) to explain such phenomenon as “Ice Ages” – however, there is no known correlation (that I’m aware of) between these cycles and magnetic pole reversals.
While Geology isn’t my specialty, if I remember correctly, the last magnetic pole reversal was almost 800,000 years ago, and the reversal before that was around a million years ago. Some magnetic reversals took place over many years, and there are some magnetic reversals theorized to have taken place during a decade or less!
What is interesting to know is currently, the North Magnetic Pole is drifting over thirty miles per year from it’s current location in northern Canada, towards Siberia. Another interesting tidbit, is that while the North Magnetic Pole is geographically “North”, electrically, it is a south magnetic pole, in that it attracts the north “pole” of a bar magnet!
…the basic idea is, each planet you see is the size it would appear in the sky if it shared an orbit with the moon,
380,000 kms from earth. I created this video in After Effects, and because of certain technical considerations had to keep the field of view at 62 degrees.
That means the foreground element is not precisely to scale. I realized this after the fact and may update the video at some point in the future. All planets are to correct scale with one another in any case.
Fifty years ago, a young President facing mounting pressure at home propelled a fledgling space agency on a bold, new course that would push the frontiers of exploration to new heights. Today, on this Day of Remembrance when NASA reflects on the mighty sacrifices made to push those frontiers, Americaâ€™s space agency is working to achieve even greater goals. NASAâ€™s new 21st Century course will foster new industries that create jobs, pioneer technology innovation, and inspire a new generation of explorers through education â€“ all while continuing its fundamental missions of exploring our home planet and the cosmos.
Throughout history, however, we have seen that achieving great things sometimes comes at great cost and we mourn the brave astronauts who made the ultimate sacrifice in support of NASA missions throughout the agencyâ€™s storied history. We pause to reflect on the tragic loss of the Apollo 1 crew, those who boarded the space shuttle Challenger in search of a brighter future, and the brave souls who perished on the space shuttle Columbia.
Through triumph and tragedy, each of us has benefited from their courage and devotion, and we honor their memory by dedicating ourselves to a better tomorrow. Despite the challenges before us today, let us commit ourselves and continue their valiant journey toward a more vibrant and secure future.
At NASA’s Johnson Space Center in Houston, Center Director Michael L. Coats will be joined by astronaut family members to lay a wreath at the Astronaut Memorial Tree Grove at 11:30 a.m. on Jan. 27.
Friday, Jan. 28, marks the 25th anniversary of the Challenger accident. At 9 a.m. EST, the Astronauts Memorial Foundation will hold a remembrance service honoring the STS-51L crew members at the Kennedy Space Center Visitor Complex in Florida.
NASA Television will provide live coverage of the event, which will take place at the visitor complex’s Space Mirror Memorial.Speakers at the event include Bill Gerstenmaier, NASA associate administrator for Space Operations; June Scobee Rodgers, widow of STS-51L Commander Dick Scobee; Robert Cabana, former astronaut and director of NASA’s Kennedy Space Center; and Michael McCulley, former astronaut and chairman of the Astronauts Memorial Foundation.
Challenger’s seven astronauts died shortly after launch on Jan. 28, 1986. The crew consisted of Commander Scobee, Pilot Michael J. Smith, Mission Specialists Judith A. Resnik, Ellison S. Onizuka, and Ronald E. McNair, and Payload Specialists Gregory B. Jarvis and Sharon Christa McAuliffe.Upon reentering the atmosphere on February 1, 2003, the Columbia orbiter (STS-107) suffered a catastrophic failure due to a breach that occurred during launch when falling foam from the External Tank struck the Reinforced Carbon Carbon panels on the underside of the left wing. The orbiter and its seven crewmembers (Rick D. Husband, William C. McCool, David Brown, Laurel Blair Salton Clark, Michael P. Anderson, Ilan Ramon, and Kalpana Chawla) were lost approximately 15 minutes before Columbia was scheduled to touch down at Kennedy Space Center.
The Astronauts Memorial Foundation, a private, not-for-profit organization, built and maintains the Space Mirror Memorial. The memorial was dedicated in 1991 to honor all astronauts who lost their lives on missions or during training. It since has been designated a National Memorial by Congress.
To view an online tribute, including photographs, videos and information about the crew members on Apollo 1 and shuttle Challenger and Columbia, visit: http://www.nasa.gov/externalflash/dor11/
Nancy Atkinson at Universe Today writes:
How often have you heard (or thought) the sentiment that all NASA really needs is a President who will issue a bold challenge for the space agency, like Kennedy did in 1961, initiating the Apollo program to the Moon? Can we ever expect to witness such a call to action again?
â€œIt is very unlikely,â€ said space historian and author Andrew Chaikin, who believes Apollo was an historical anomaly. â€œI think for many decades people saw Apollo as a model for how to do a space program; that you get a President to get up and make a challenge and the country follows along and does great things. But that was only true that one time in the context of the Cold War.â€
We went to the Moon when we did not because we were a nation devoted to exploration, Chaikin believes, but because it seemed a politically important course of action in the context of our Cold War with the Soviet Union. â€œOnce that was accomplished, then that political imperative evaporated,â€ he said.
Likely, we wonâ€™t hear any bold space-related challenge in tonightâ€™s State of the Union Address by President Obama. Given the state of the economy, NASA might be facing a cut or freeze on their budget, a fact which might emphasize how unique an event the Apollo program ended up to be.
â€œWhat is required now is the development of technologies that will allow us to explore space in a sustainable way,â€ said Chaikin, author of â€œA Man on the Moon: The Voyages of the Apollo Astronauts,â€ who I interviewed for the NASA Lunar Science Institute podcast, â€œa way that wonâ€™t break the bank and will allow us to do more and more with reliable transportation systems that get us up into low Earth orbit. Then perhaps we can build the machines that can actually be stored in space to allow us to venture beyond low Earth orbit to the Moon and even further, to Mars and other destinations in the solar system.â€