Leaving Earth cover

In 2019 I obtained from my former publisher the last 30 copies of the now out-of-print hardback of Leaving Earth. I sold about half of these, and with only a handful left in stock I have raised the price. To get your own autographed copy of this rare collector's item please send a $75 check (includes $5 shipping) payable to Robert Zimmerman to

Behind The Black, c/o Robert Zimmerman
P.O.Box 1262
Cortaro, AZ 85652

I will likely raise the price again when only ten books are left, so buy them now at this price while you still can!

Also available as an inexpensive ebook!

Leaving Earth: Space Stations, Rival Superpowers, and the Quest for Interplanetary Travel, can be purchased as an ebook everywhere for only $3.99 (before discount) at amazon, Barnes & Noble, all ebook vendors, or direct from my ebook publisher, ebookit.


Winner of the 2003 Eugene M. Emme Award of the American Astronautical Society.

"Leaving Earth is one of the best and certainly the most comprehensive summary of our drive into space that I have ever read. It will be invaluable to future scholars because it will tell them how the next chapter of human history opened." -- Arthur C. Clarke

Sunspot update May 2019: The long ramp down

NOAA yesterday released its May update for the Sun’s sunspot cycle. The graph is posted below, annotated by me to give it some context.

The Sun in May continued to show the exact same amount of activity as it had shown for March and April. This steady uptick in sunspot activity once again shows that the ramp down to full solar minimum will be long and extended.

May 2019 sunspot activity

The graph above has been modified to show the predictions of the solar science community for the previous solar maximum. The green curves show the community’s two original predictions from April 2007, with half the scientists predicting a very strong maximum and half predicting a weak one. The red curve is their revised May 2009 prediction, extended in November 2018 four years into the future.

That we are definitely ramping downward to minimum, even with the slight increase in the past three months, is shown by the fact that the Sun has shown no sunspots for the past fifteen days. In fact, all the activity shown in May comes from the first half of the month. This pattern is actually a reflection of the Sun’s 27-day rotation period. As I noted in my February 2017 update,

January’s activity however illustrated a statistical phenomenon that is typical of the sunspot count. That count is determined not by the numbers of sunspots on the entire surface of the Sun, but on the sunspots visible on the side of the Sun facing the Earth. Since it is not unusual for one face to be more active than the other, as we transition from maximum to minimum the sunspot counts will often show a more pronounced up-and-down curve reflecting this fact. Since the Sun’s day equals about 27 Earth days, this means that about every two weeks the active side will dominate our view until it rotates away and the inactive side reveals itself for two weeks.

In 2017 the number of spots were greater, so the period of inactivity was generally less. Now, it is not unusual for the Sun to be blank for weeks at a time. When it does become active, it is also not unusual for that activity to be confined to one hemisphere, so we get two weeks or less of activity, followed by two weeks or more of blankness.

So far there have been no sunspots in June. Expect that to continue for at least another week, when the more active hemisphere of the Sun returns to face us. I would not be surprise however if that other hemisphere arrives with its sunspots gone, so that the present streak of blankness continues unabated.

Meanwhile, solar scientists struggle to figure out what is going to happen next. Unlike climate scientists, who know as little about the climate, the solar science community admits to its ignorance about the Sun, and the uncertainty of its solar models.

Pioneer cover

From the press release: From the moment he is handed a possibility of making the first alien contact, Saunders Maxwell decides he will do it, even if doing so takes him through hell and back.

Unfortunately, that is exactly where that journey takes him.

The vision that Zimmerman paints of vibrant human colonies on the Moon, Mars, the asteroids, and beyond, indomitably fighting the harsh lifeless environment of space to build new societies, captures perfectly the emerging space race we see today.

He also captures in Pioneer the heart of the human spirit, willing to push forward no matter the odds, no matter the cost. It is that spirit that will make the exploration of the heavens possible, forever, into the never-ending future.

Available everywhere for $3.99 (before discount) at amazon, Barnes & Noble, all ebook vendors, or direct from the ebook publisher, ebookit.


  • Max

    Space weather (on May,30th.) noted that a brief cycle 25 reversal occurred for a few hours. It barely registered so it may have been a fluke.

    Jupiter has got problems.

  • Alex

    Mr. Z.,
    Your postings regarding the “Solar Weather” over the past, intrigued me greatly.
    So much so that I began researching and reading, learning.
    I now subscribe to the “Space Weather Woman” site, as well as ‘other down to earth’ sites.
    Truly amazing stuff this solar weather.
    Thank you for your work, and perspective into the many mysteries of Creation.


  • Andi

    Has anyone considered placing two probes in Earth’s orbit around the Sun, leading and lagging us by 120 degrees, so that the entire Sun can be observed?

  • Andi: This has already been done. Stereo-A and Stereo-B were launched in 2006. See: https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2006-047A

    Stereo-B failed in 2014, but Stereo-A still functions.

    For consistency with more than almost three hundred years of sunspot data, solar scientists continue to base their sunspot count on the visible face of the Sun.

  • wodun

    Jupiter has got problems.

    Maybe they are ready to reveal themselves.

  • Max

    Wodun, just a dude;
    Jupiters great eye is closing, if anything they’re hiding themselves.
    The red spot was once greater than three earths across and now it’s as small as one earth.
    I never did find out if the storm was/is the other magnetic South Pole.

    I made a mistake in another thread on the 11 year planetary alignment causing the solar cycle. (I shouldn’t post after several 13 hour graveyard shifts, I keep making mistakes)
    Jupiter is in retrograde from April to August with our closest approach in June. Watching it in the sky, moving towards Scorpius I mistakenly said it already passed over Sagittarius. (All planets move around the sun in the same direction, towards the east. A amateurs mistake)
    The 11.6 year Jupiter cycle passing in front of Sagittarius, the center of our galaxy, is happening “now” until next year. Is it Just a coincidence with the low in the sunspot cycle?
    ( I’m too lazy to look up past sunspot history)

    I just read something on a NASA website that makes me feel better about being an amateur. A statement that the magnetic poles flip during solar maximum.
    (The statement that the suns magnetic field comes from electrical currents fascinates me)

    ” It is widely believed that the Sun’s magnetic field is generated by electrical currents acting as a magnetic dynamo inside the Sun. These electrical currents are generated by the flow of hot, ionized gases in the Sun’s convection zone.
    We know a lot about the Sun’s magnetic dynamo. It has a 22 year cycle. During the first half of the cycle, the Sun’s magnetic north pole is in the northern hemisphere while the magnetic south pole is in the southern hemisphere. Right around the peak of the sunspot cycle (solar maximum), the magnetic poles flip or exchange places so that magnetic north is now located in the southern hemisphere. This flip occurs about every 11 years at solar maximum.
    The 22 year magnetic cycle greatly influences the most prominent manifestation of the dynamo, sunspots and active regions, which migrate towards the solar equator from high latitudes over the course of the solar 11 year “sunspot cycle”…

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