A Mountaintop in Hawaii

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Photo credit: Chris Amos


I’m writing this on a plane from Honolulu to Los Angeles having enjoyed the first few days of my book tour in the paradise on Earth that is the Hawaiian archipelago. Most memorable for me was the expertly guided tour of the Keck Observatory on the “big” island of Hawaii – on a 14,000 foot mountain – high enough for them to offer me oxygen. I tried it, hoping for some sort of metaphorical as well as literal high, but I couldn’t detect any difference from ordinary air and soon discarded it.

There are lots of big telescopes on the mountain. The Keck Observatory has two of them: identical reflecting telescopes side by side on the bare mountain, connected by a corridor laden with complicated infrastructure. My first surprise was the discovery that astronomers themselves seldom need to go up the mountain. You might expect that of theoretical astrophysicists, but I’m talking about observational astronomers making real measurements of real stars and galaxies. When you think about it, it’s not so surprising. A giant reflecting telescope with its 34 foot parabolic mirror has to be controlled by accurate computer, not clumsy human hand. Almost as obviously, the measurements it takes are destined to be fed straight into a computer: no human eye actually “looks” into an eyepiece of a big telescope. Indeed, I doubt that the word “eyepiece” has any applicability to leviathans such as the Keck reflectors. So why would the astronomers need to stir themselves up the mountain? Instead, they are cosily ensconced at “ base camp”, staring at banks of computer screens under a commonplace ceiling. On the mountain itself the personnel are mainly engineers, ceaselessly engaged in the round-the-clock business of maintaining the giant instruments in precision working order.

When I heard the learn’d astronomer,

When the proofs, the figures, were ranged in columns before me,

When I was shown the charts, the diagrams, to add, divide and measure them,

When I sitting heard the astronomer where he lectured with much applause in the lecture room,

How soon unaccountable I became sick and tired,

Till rising and gliding out I wander’d off by myself,

In the mystical moist night air, and from time to time,

Look’d up in perfect silence at the stars.

No scientist could really go along fully with Walt Whitman, but we might have a little more sympathy given the fact I have just told you, that the learn’d astronomers, far from gazing rapt at the night sky, don’t even go near a telescope. The sympathy should not last long, however. And even Walt Whitman might have been inspired by the poetry of the laser beam that shoots into the sky, straight as a . . . well, similes are superfluous, for what in the world is straighter than a laser beam?

What is the laser for? This is where the story becomes truly wonderful. It is a story of which I had known nothing, and I was grateful to be enlightened by one of the learn’d astronomers, Dr Roy Gal of the University of Hawaii Institute of Astronomy. Before I tell the story, a brief preamble . . .

The resolving power of a reflecting telescope is directly proportional to the diameter of the mirror at its back. Moreover, the bigger the mirror, the greater the number of photons, speeding along parallel paths, that can be examined to give us information about the distant star or galaxy which is their source. Mirrors larger than a certain size inevitably sag, so giant mirrors have to be assembled by jigsawing a number of smaller hexagonal mirrors, each one precisely curved to its place in the giant parabola. The two Keck mirrors each have 36 hexagonal components. The 36 are swapped in and out, two at a time at bimonthly intervals, following a careful regimen of cleaning and polishing. Indeed the sheer perfectionism of the cleaning and polishing rituals, to say nothing of the minuscule tolerances of the milling procedures by which the hexagons are made in the first place, took my breath away.

But however large the mirror, and however exquisitely machined, cleaned, polished, fitted and adjusted, there is an additional limit on the quality of the image it can serve up.  Unlike the Hubble telescope (of which more in a moment) and unlike any projected telescope built on the moon (maybe one day) Earth-bound telescopes are smothered beneath the thick blanket which is the atmosphere. Air refracts – bends the light rays. This wouldn’t matter if the air were perfectly uniform and still, but it isn’t. The refractive index of air varies with temperature; and winds and turbulence constantly mess about with the refraction of the light rays coming from any star. If only we could park our telescope outside the atmosphere!

Well we can, and this is why the Hubble telescope is so good. This is why the Hubble can compete with the largest Earthbound telescopes, even though its mirror is a fraction of their size. But there is a cunning trick by which an Earthbound telescope such as the Keck pair can achieve the equivalent of getting outside the atmosphere. The trick is known as Adaptive Optics.

Think about it. Atmospheric turbulence is a known phenomenon. If we could only measure it, from moment to moment and from place to place, we could compute the effect of turbulence on the image of a star or galaxy, compensate for it, and reconstruct what the starlight would tell us if only there was no atmosphere. How to do it? This is where the laser enters the story.

The laser points in exactly the same direction as the telescope and slightly to the side. It is pure sodium light, with the known spectral lines characteristic of sodium. High above the atmosphere is a layer of “sky” where the beam excites sodium atoms. The reflected light shoots straight back to the observatory, where it is picked up by sensitive and fast-responding instruments. Do you see the elegant cunning of this? The reflected sodium light has been  subjected to exactly the same atmospheric turbulence as the light from the distant star or galaxy we are studying. Since we know the precise quality and intensity of the sodium light, the fluctuations in the reflected light tell us exactly what must also be happening to the incoming starlight. And our Earthbound instruments therefore have all the information needed to reconstruct what the starlight would look like if only there was no atmospheric turbulence to distort it.

You might think that the compensation could be done by adjusting the big hexagonal mirrors that constitute the giant reflector. Indeed the hexagons can be adjusted, and they are precisely lined up before the evening’s observations begin, by means of delicately refined measurements of beams reflected by them. But the hexagons are massive. Any attempt to move them would inevitably be too slow.  The correcting adjustments couldn’t be fast enough to keep up with the fluctuations in the turbulent atmosphere. Instead, the adjustments are made to smaller mirrors downstream from the main mirror in the chain of light transmission. The result of all this ingenious precision engineering and computational wizardry is that a large Earthbound telescope can closely approach the optimal performance theoretically allowed by the diameter of its mirror.

One strange coda to this lovely story. The only person on the strength who actually does what Walt Whitman would wish – at least in a professional capacity – is a man in a thick fleece sleeping bag, lying flat on his back on an electrically operated turntable outside the telescope.  Armed only with a pair of binoculars, he passes the hours gazing up at stars and Milky Way. His job is to watch for aircraft which might stray into the airspace above the observatory. Why? Laser beams of the power needed are extremely dangerous: more than 2,000 times the power of an ordinary classroom pointer laser. They would instantly blind anybody who happened to look down from a plane, with especially drastic consequences in the case of the pilots. The task of the lonely sentinel in the sleeping bag is to keep a vigil for planes, and cut the laser off if one should stray dangerously close to the beam.

The master plane-spotter to whom we spoke had been doing the job for eight years. He had only once thrown the emergency switch, and even then it turned out that there was no danger. The risk has been calculated as 1-in10,000. Scientists calculate that automated instruments could do the job with greater reliability than even the most conscientious human observer. Yet the Federal Aviation Authority has decreed that only the human eye should be trusted with such a responsible job. That’s what happens when non-scientists terrified of lawyers are allowed to take decisions that are in the proper domain of scientists. It’s reminiscent of the exaggerated respect given to eye-witness testimony in courts of law, despite frightening – in some cases comical – demonstrations of the unreliability of the human eye and memory.

A great observatory like the Keck is one of those human achievements which, like the Large Hadron Collider, the Human Genome Project, William Shakespeare and Franz Schubert – render me tearful with pride at belonging to the species Homo sapiens. After nearly four billion years of evolution, our species awoke from a sub-intelligent stupor, saw the stars and wondered. Within a few millennia, we had worked out that they wheel around the sky in a way that could sensibly be explained only on the hypothesis that we are sitting on a spinning ball of tiny dimensions compared to the distances between the stars. Within centuries we knew the awe-inspiring truth that the stars visible to the naked eye are all near neighbours, clustered in one galaxy, the Milky Way, which is but one among 100 billion galaxies. Within decades we knew that space itself is expanding, and the galaxies receding from us and each other, at ever increasing velocities until they outpace their own light and disappear, beyond the faintest hope of detection, over the unbridgeable Event Horizon.

We know all this because of precise, quantitative data gathered by instruments such as the twin Keck telescopes. These giant, staring eyes are honed and adjusted to a perfection which allows us to leap the parsecs – to escape the home planet and spring across literally billions of light years toward the far reaches of forever and wherever. And to me perhaps most moving of all is the fact that no one man or woman could even begin to achieve such feats. This is a cooperative enterprise, bringing together the finest that our remarkable species has to offer: not just astronomers but mathematicians, engineers, physicists, computer scientists, spectral chemists – one day, who knows, maybe even biologists. We climbed the high mountain on the island of Hawaii and broke through the cloud layer to the summit: a metaphor, perhaps, for one of the loftiest pinnacles of human achievement.

I am indeed proud to celebrate humanity. And surely Walt Whitman – who celebrated himself as a man – would do the same. On reflection . . .

 

 

Written By: Richard Dawkins
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46 COMMENTS

  1. Religious people are so poorly served by their puny little gods, who cannot compete with the magic of reality being revealed by the rapidly accumulating efforts of freethinking human inquiry, ingenuity & dexterity.

    Thanks Professor Dawkins for this beautiful explanation about one of our best cosmic knowledge expanders.

    The slope has been stunningly long and gentle, but the height of our Mount Improbable is ever increasing.

    Enjoy the rest of your tour, doing great work on behalf of Reason and Science, bringing light to those in shadow.

  2. Excellent evocative article.
    I find an exquisite frisson  when understanding a particularly cunning, but usually quite simple to understand,  solution to a scientific or technological problem. It often involves eliminating  confounding factors using some particularly ingenious device. Coming up with something like that must be  a real eureka moment.

    Very minor point but it might help some not familiar with reading poetry. There is, I think, some punctuation missing from the quoted poem:

    WHEN I heard the learn’d astronomer; 

    When the proofs, the figures, were ranged in columns before me; 

    When I was shown the charts and the diagrams, to add, divide, and measure them; 

    When I, sitting, heard the astronomer, where he lectured with much applause in the lecture-room, 

    How soon, unaccountable, I became tired and sick;         5

    Till rising and gliding out, I wander’d off by myself, 

    In the mystical moist night-air, and from time to time, 

    Look’d up in perfect silence at the stars.
    Note:  I don’t have an original printed copy of the poem and I found various versions online including the one quoted by RD but I think this version is probably accurate – Some may also be interested in this analysis of the poem http://poemsunpacked.blogspot….

  3. What a lovely piece. Thank you for sharing.

    And it was bashed out on a plane, where lesser members of this ‘remarkable species’ might spend their time gazing out of the window, quaffing the Champagne, and attempting to chat-up the stewardesses in the absurd belief that they haven’t heard it all before.

    Whenever one ‘Look[s] up in perfect silence at the stars,’ consider how much more meaningful it has become now those learn’d astronomers, having looked down at their computer screens, ensconced under starless ceilings, have explained so much.

    And yet. There is so much left to explain.  Homo sapiens has travelled so far in a few short centuries: the huge collaborative projects Richard mentions fill us with pride and admiration, yet what wonders are still to come?

    After billions of years, life on Earth has only very lately woken up and begun to explore. How sad that Walt Whitman cannot see what we see today, that we cannot explain molecular genetics to Charles Darwin, that our ephemeral generation can hardly imagine what our grandchildren might see, let alone what wonders will be savoured by our distant descendents.

    I believe we are born at a hugely unfortunate time: at the start of a great exploratory voyage, which will proceed via some stunning discoveries we’ll not be awake to see.

    Coming events cast their shadows before them. On reflection, it’s bloody annoying.

    ps. I defy Richard’s final ellipsis. There is hope: Pandora’s gift endures.

  4.  Which of the about five thousand invented ones, including various middle eastern ones featuring allah and yahweh, would you figure are laughing…oh, I forgot, as inventions of the human mind a human would have to write about their laughing.

    The article you are linking to is about as convincing of an afterlife as the reports of alien abductions are.
    If they contained anything but the emanations of an oxygen deprived brain, a brain that constantly processes information, and invents circumstances to account for uncommon or novel experiences – especially if that experience is the absence of any information input.

    http://near-death.com/experien
    “God – The category with the highest percentage
    of NDErs who reported seeing a divine being were those in
    the new age (80%) category. The category with the lowest
    percentage is the non-religious (27%) category. The lower
    percentage suggests that fewer non-religious NDErs see a
    divine being. This may be an example of non-religious NDErs
    “getting what they expect.” A divine being was seen by (75%)
    of those in the atheist category. This high percentage may
    reflect the possibility that these atheists, in general,
    are “getting what they need.” The same percentage of Christian
    and non-Christian NDErs (63%) saw a divine being. This suggests
    that a NDEr doesn’t have to be a Christian to see God.

    Hmm, I wonder what kind of god the non christians saw?
    There are so many option in which god to believe in, I rather choose to cast them all out and to believe in none.

  5. Hello Jag Pop,

    I had difficulty trying to understand your comment about human conceit – can you please expand on this for me?

    Also, since I have no experience of supernatural deities, maybe you can explain how you know what the gods are thinking or doing?

    I’ve followed the ‘news’ you linked to, at several locations.  The best explanation is on the Sam Harris Blog, where Sam explains the neural & chemical reality of what the doctor experienced while in a coma – which is not brain death – then recalling various details about a place he had not been to.

  6. @OP:twitter  – A great observatory like the Keck is one of those human achievements which, like the Large Hadron Collider, the Human Genome Project, William Shakespeare and Franz Schubert – render me tearful with pride at belonging to the species Homo sapiens

    Here’s another one in process!

    http://finance.yahoo.com/news/… – Ball Aerospace & Technologies Corp. began the process of shipping the finished NASA James Webb Space Telescope mirrors to Goddard Space Flight Center, Greenbelt, Md., on Friday, September 14, 2012.

    Ball Aerospace, under contract to Northrop Grumman, is responsible for the Webb’s optical technology and lightweight mirror system.
    Two of the 18 beryllium primary mirror segments that comprise NASA’s sophisticated Webb Telescope were shipped from Boulder in custom containers designed specifically for the multiple trips the mirrors made through eight U.S. states while completing their manufacturing.
    The remaining 16 mirrors will make their way from Boulder to Goddard over the next 12 months as they await telescope integration in 2015.

    The Webb is on track for an October 2018 liftoff.

    “Ball and its subcontractors have spent eight years tackling the rigorous requirements associated with JWST’s optical design,” said David L. Taylor, president and CEO of Ball Aerospace.
    “We are very proud to have answered the challenge posed by James Webb and look forward to this ground-breaking NASA science mission.”

    The Webb Telescope will be the first civilian space-based observatory to use an actively controlled, segmented mirror architecture. Each of the 18 hexagonal-shaped mirror assemblies that make up the 21.3-foot (6.5 m) primary mirror measures more than 1.3 meters across, and weighs approximately 40 kilograms, or 88 pounds, after light-weighting.

    There is a picture of the mirror containers here:

    http://l2.yimg.com/bt/api/res/

  7. I thought that was a great article. I hope this doesn’t sound patronising, but I think Richard writes about astronomy extremely well for a biologist (I say that as an ex-astronomer).

  8. Beautifully crafted article on a beautifully crafted ‘eye’. Just read in Scientific American that an eye has been grown from stem cells, and that the LHC ‘eye’ is looking deeper and deeper into matter. Science sees in so many directions.

  9. Not been there myself, but since I did the fabrication drawings back in the 80s for the components that comprise the housings for the telescopes, and the jig that was needed to assemble the panels on site, it is a place I really want to visit.

  10. What is not to like about the scientific endeavor?

    The sad truth though seems to be predictable human lethargy and lack of curiosity.

    The splendor of science and the spectacular achievements of technology mostly languish unknown to ‘most’ of our species. After all, when Richard talks about our species, he surely means all seven billion plus members of it. And how many of them have a layman’s understanding about the great astronomy or particle physics happening in our time.

    When I consider where the envelope of science is and where the horizon of the average citizen of the world lies, it’s like we humans are simultaneously living in the 21st and 15th centuries. What a shame, isn’t it?

    Twitter: @sachi_bbsr:disqus 

  11. “The trick is known as Adaptive Optics”.

    Religios proably don’t have any issue with scientists who consider, analyse and solve problems like how to overcome atmospheric distortion. It’s uncontroversial. But given the evident thought and brain power which went into solving this problem, how, on earth, can they then complain that other scientists don’t know the age of the earth. It’s mindboggling. But as my Dad used to say “There’s none so blind as them that don’t want to see”.

  12. Superb article Richard!
    Your meetings and observations with both pieces of exotic scientific equipment and the scientists concerned are immensely illuminating.
    The one one you had filmed with JCraig Venter and his tackle was just the same(I emailed it to a lot of people)
    It’s just more “Magical Reality”.

  13. Here is some of the latest news from the Keck Telescope:

     
    Planet with four suns discovered by volunteers – http://www.bbc.co.uk/news/scie… 

    Astronomers have found a planet whose skies are illuminated by four different suns – the first known of its type.

    The distant world orbits one pair of stars which have a second stellar pair revolving around them.

    The discovery was made by volunteers using the Planethunters.org website along with a team from UK and US institutes; follow-up observations were made with the Keck Observatory.

    A report on the Arxiv server has been submitted to the Astrophysical Journal.

    The planet, located just under 5,000 light-years away, has been named PH1 after the Planet Hunters site.

    It is thought to be a “gas giant” slightly larger than Neptune – more than six times the radius of the Earth.

    “You don’t have to go back too far before you would have got
    really good odds against one of these systems existing,” Dr Chris Lintott, from the University of Oxford, told BBC News.

    “All four stars pulling on it creates a very complicated environment. Yet there it sits in an apparently stable orbit.

    “That’s really confusing, which is one of the things which
    makes this discovery so fun. It’s absolutely not what we would have expected.”

    Binary stars – systems with pairs of stars – are not
    uncommon. But only a handful of known exoplanets (planets that circle other stars) have been found to orbit such binaries. And none of these binary systems are known to have another pair of stars circling them. 

    Asked how this planet remained in a stable orbit whilst being pulled on by the gravity of four stars, Dr Lintott said: “There are six other well-established planets around double stars, and they’re all pretty close to those stars.

    PH1 was discovered by two US volunteers using the Planethunters.org website: Kian Jek of San Francisco and Robert Gagliano from Cottonwood,
    Arizona.

    The new planet – a gas giant – is about six times the size of Earth – http://news.bbcimg.co.uk/media

    Follow-up observations were made with the Keck facility on Mauna Kea -  http://news.bbcimg.co.uk/media

  14. I had a chance to visit Mauna Kea a couple years ago. Unfortunately, I wasn’t able to go to the top but nightsky from the Onizuka visitor center is still the most awe inspiring sight I can remember.

    I must say I’m kind of surprised that the professor didn’t mention the conflict with the natives regarding the observatories on Mauna Kea (and I think Haleakala to a lesser extent). It saddens me to think of the scientific discoveries that would have been made if we hadn’t respected the superstitions of these people.

    One little nit…the Keck’s are Ritchey-Chretien designs, which means the primary mirrors are hyperboloidal (not paraboloidal).

  15. Schubert underrated? Not by me! He’s up there with Bach, Beethoven and Mozart. Over 600 songs, symphonies, chamber music, piano pieces etc . and all before he died aged 31! I think Schubert would have appreciated the poetry of Richard’s prose!

    And so do I!

  16. >> Within decades we knew that space itself is expanding, and the galaxies receding from us and each other, at ever increasing velocities until they outpace their own light and disappear, beyond the faintest hope of detection, over the unbridgeable Event Horizon.

    N00b science question here: how would a distant star outpace it’s own light from moving away from us, presumably this would mean relatively moving faster than the speed of light from Earth?

  17. It’s just a reference to the expanding universe compared with the speed of light.  The light of a distant star emitted 13.4 billion years ago, say, would take 13.4 billion years to reach us, by which time the star itself would be outside the observable universe.  You couldn’t see it because of the lag time between the moment when light is emitted and the time it takes to reach us, and in the meantime, the expanding space-time would carry the star further away.  It doesn’t literally mean the star is travelling faster than light.

  18. This is a beautiful piece.  Your enthusiasm really shines through, and I learned one or two things from reading it as well.  Now I wish I could go to Hawaii and see the observatories myself.

    I was quite surprised to learn how much of it was automated.  Until now, I assumed the telescopes were still used manually even if computers were recruited for aligning the ‘scope.  It makes more sense with automation, however, as with the image enhancements, corrections, and the ability to photograph sections for later analysis.

    The part about the laser was familiar with me; I was part of an amateur astronomer’s society, and we used handheld lasers to point out stars and clusters of interest (we were based on the university campus, hence why we had such resources).  We even got our own automated telescope that auto-aligned itself once you gave it the current time and date, manually triangulated it with certain stars, and set it to auto-track. Thing was a devil to set-up, though, so we still used manually operated telescopes on the side.

  19. This was really good, Richard. Now I hope you can expand it to a book’s length, blending science and poetry as you’ve done above. I previously suggested the same thing on a separate thread. Maybe, as you did in The Magic of Reality, you can collaborate with an expert (in poetry this time) and write something that draws the sciences and poetry together. That would be truly magical. There are any number of poets who made “poetic guesses” as to the real nature of the universe. These guesses were and are often beautiful and awe-inspiring, but they pale when contrasted to the poetry of reality: science. I, for one, look forward to a book that brings these two worlds together… and there’s hardly a person more qualified than one who is a member of two of the most prestigious literary and scientific societies in the world.

  20. A magical piece Richard.I had the Jehova’s Witnesses at the door yesterday.Not the usual little man in milk bottle glasses and greasy mac, but 2 attractive young women,so I didn’t slam the door as I usually would, but engaged them.We had a long rather one sided conversation, where they constantly tried to assert the truth of the buybull, but eventually we got to the cosmos.I asked them if they agreed there were billions of galaxies containing trillions of stars? They agreed.We talked about the Goldilocks zone, which they had not heard of and the likelihood of carbon based life on other planets(they did not know what Carbon based life meant).Eventually i asked them if they REALLY believed that of all the unimaginable number of worlds there are in the universe and potentially other universes, that their little  jesus chose to show himself to a bunch of shepherds and fisherman in a backward region of the middle east in the mid Roman period.And the reason he did was to get himself nailed to a plank because we don’t all do good things.Their yesses were more than a little timid and they suddenly remembered an appointment elsewhere! Enjoy the rest of the tour.

  21. “That’s what happens when non-scientists
    terrified of lawyers are allowed to take decisions that are in the proper
    domain of scientists.”

     

    It is true that many lawyers are “risk
    adverse”, and extremely so, particularly those practicing in civil litigation,
    as often too are public officials and politicians who will seek advice from
    lawyers before making a decision. The criticism is a reasonable one. However, I
    think that the official or politician making such a decision will consider the
    media coverage and how you and I (the all important voter) will react if that
    less than 1 in 10,000 chance were to occur.

     

    Can you imagine the headlines and front page
    photographs? Can you hear the typical media interview with the relevant Minister and
    the CEO of the public authority responsible, as well as the opposition member
    of parliament stating that this would never have happened if they had been in power? Can you hear the
    howls for a public inquiry asking why the automated system was not watched over
    or second guessed by that imperfect of beings – us?

     

    These are the things; the publicity, the
    reaction of the public whipped up by the media, the costs of a public inquiry
    and the costs of potential litigation that are forefront in their minds when
    making such a decision.

     

    All of this over a risk that is far, far less
    than that of being involved in a fatal road vehicle accident. The risk on the
    road is taken for granted, or rather ignored by us. It is an “acceptable risk”.

     

    Why? It cannot be the calculable risk that
    affects our decision, as this is inverse in this example. Perhaps it is, more
    likely, the lack of familiarity with the science or connection with
    our day to day lives, and the perceived lack of importance and usefulness of
    what is being done by the scientists that result in the poor decision making of
    the public official.

     

    Better public education about science and its
    importance to us, it can be hoped would lessen the fear of the public official or
    politician in making such a decision. 
    Might it outweigh the affect of the fear of public
    reaction? I fear we have a long way to go before it does.

  22. I agree it is all about educating people in the Sciences and rational thought.
     However, our Civil Servants who are appointed to make decisions on behalf of an undereducated public should be “qualified ” and expected to make rational decisions, and not decisions based on emotion, their own ignorance, or pandering to public ignorance. If they can’t do that they  are unqualified to be in such a decision making position in the first place.It would be a case of the “blind leading the blind  or the tail wagging the dog” for which there really is no excuse.jcw

  23. I also recently saw on TV that we take ridiculously precise measurments of the distance to the moon by bouncing laser beams from the earth from mirrors left on the moon’s surface by one of the Apollo missions. This taught me three awesome things
    i) the moon is getting gradually further and further away as time passes, in a billion years the earth will be much less stable on its axis as the effect of the moons gravity is reduced.
    ii) you can have a job where what you do is FIRE LASERS AT THE MOON, I blame my careers teacher for not telling me about that one.
    iii) You can shut up people who say Apollo was a hoax by asking where the mirrors came from.

  24. Roy72
    I also recently saw on TV that we take ridiculously precise measurments of the distance to the moon by bouncing laser beams from the earth from mirrors left on the moon’s surface by one of the Apollo missions.

    Lunar Laser Ranging Experiment with the stereo camera in the background (NASA image number AS11-40-5952).
    This Retroreflector was left on the Moon by astronauts on the Apollo 11 mission. 20 July 1969
    Astronomers all over the world have reflected laser light off the reflectors to measure precisely the Earth-Moon distance.
    http://upload.wikimedia.org/wi

    ..and along with the later ones is still working today!

    A portion of the Apollo 15 lunar laser ranging retroreflector array, as placed on the Moon and photographed by D. Scott. Credit: NASA/D. Scott –
    It was placed on the Moon by astronaut David Scott on 1971 July 31.
    http://www.nasa.gov/images/con

  25. The telescope with the open dome in the picture, though, is the Caltech Submillimeter Observatory, and there are two astronomers directly inside there! So Walt Whitman need not be so depressed.

  26. Very nice article.  RD please note that ‘event horizon’ is to do with the edge of a black hole.   The edge of the observable universe is usually termed the cosmic horizon or the particle horizon.   I wanted to be an astronomer when I was a boy. 

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