Some Thoughts on the Movie, Gravity

astronaut floating in spaceBy: Michael Watson, LLB

Helen and I went to see this much-reviewed and much-discussed 3D extravaganza last night.  No, this note is not going to be an astronomer’s sourpuss picking away at the movie’s scientific flaws, although I will point out a few things.  Here are some thoughts:

1.    I may be really dense, but I don’t understand the title.  It really doesn’t have anything to do with the content of the film.

2.    The 3D really works well most of the time, and the glasses that you have to wear are much more fashionable than the huge comic glasses that we had to wear in the old days of primitive red-green 3D.  You feel that you can reach out and grab the floating loose screws and water droplets right from your seat.

3.    More generally, the effects are really good.  Weightlessness – or “zero G”, as even astronomers inaptly call it – is very difficult to simulate, so much so that for past space movies the producers have hired NASA training aircraft that climb to a high altitude and then fall ballistically (i.e. on a free-fall elliptical path), giving the occupants a few minutes of true weightlessness where they float around inside the aircraft just as in space.  The producers of Gravity have done a really good job in simulating this effect.  I don’t buy headline-grabbing astronomer Neil deGrasse Tyson’s picayune complaint about Sandra Bullock’s hair not floating properly.  I thought that her hair was great.

4.    On a related point:  The depictions of the motions of objects in space are quite good.  Every moment there is a decent display of Newton’s First and Third Laws of Motion.  It’s really nice to see a space movie that respects how objects actually move.

5.    The plot is pretty lame and contrived to me, as well as being, well, pretty much impossible from an orbital mechanics point of view.  Lots of things also are just not true to life.  As entertaining as it may be to watch George Clooney flitting around a space shuttle orbiter in a 1980s-style self-propelled backpack, tossing off anecdotes and humorous bon mots while scientist Bullock tries to concentrate on replacing a panel on the Hubble Space Telescope, that’s just not the way astronauts work and conduct themselves on a mission.  I thought I was watching Dan Aykroyd and John Belushi (RIP) Meet the Space Age.  Clooney-style cut-ups don’t make astronaut grade, and certainly don’t get assigned to missions.

6.    This is more a matter of technical interest:  The movie plot is based on the premise that (i) the Hubble Space Telescope, (ii) the International Space Station, and (iii) the imaginary Chinese space station, all share essentially the same orbit.  This means that when one of them is destroyed by swarms of deadly satellite debris that whiz by every 90 minutes (inexplicably in the same orbit too, by the way), astronauts can conveniently move to one of the others nearby in an effort to save themselves.  This is the biggest departure from reality in the movie (although I certainly wouldn’t say that it ruins the movie – that’s not really possible with Bullock and Clooney in it …).  The HST is in an orbit about 570 km above Earth, inclined 28.5 degrees to the equator.  The ISS, on the other hand, is in a much lower orbit (~420 km), with an orbital inclination of about 52 degrees.  The result is that they never get anywhere close to each other, and it’s impossible to move from one to the other without enormous quantities of fuel.

All in all, Gravity is an interesting and entertaining film for a space enthusiast to see, but I must say that I’m a little surprised at the rave reviews and four-star ratings that I’ve been seeing.  I think that they must be mainly for the considerable technical achievements rather than for the plot.

Waiting on the Moon

Milky Way

By: Michael Watson, LLB

People on our street love to stop by and take a look through the telescope at the Moon, when it is in its waxing phase in the southern or western sky in the evening.  A 9-year-old asked me the other night, “Have you ever looked at the Full Moon through your telescope?”  The answer is yes, of course, but then I had to explain to him that the Full Moon is probably the least interesting object to observe in the sky.

… which leads me to the more general topic:  the Moon as the enemy of serious astronomers.  Although it is one of the darkest objects in the solar system, reflecting only about 18% of the sunlight that falls on it, when it is above the horizon the Moon floods the sky with so much light that it is impossible for astronomers to see the faint galaxies, nebulae and star clusters that we are almost always aiming for when we get out our observing instruments – whether binoculars or telescopes.  That is why astronomers love those weekends – which arrive every four weeks – when the Moon is at or close to its new phase.  At these times the Moon sets around the same time as the Sun, and we get an entire night with no pesky light polluting orb in the sky.

This past weekend the weather forecast was that Thursday and Friday’s cloud cover would lift rather sharply just before midnight on Friday evening.  The Moon was near First Quarter, and would set around 01.30 on Saturday morning.  I drove up to our family cottage in Muskoka after work on Friday, had a quick supper, then went to bed for three hours, getting up around 22.00.  Then I drove 90 km to the Torrance Barrens Deep Sky Preserve about 35 km southwest of Gravenhurst, set up the telescope and my photo equipment, and waited for the Moon to set and the sky to darken.  Just after 1.30, with the temperature hovering at 6 degrees, I started making photos of the Milky Way.  But then came the curse of late summer and fall: fog.  At this time of year the combination of temperature changes and water vapour in the atmosphere often produces ground fog around and after midnight.  At about 02.00, within one minute the entire sky filled with fog, and made continued observing impossible.  So I reluctantly dismantled the telescope, loaded all of the gear into the car, and headed back to Toronto.

At least I got one set of photos that I was able to do something with.  Here is a wide-angle photo of our Milky Way galaxy, consisting of three stacked 5-minute exposures (*see description below).

Milky Way

*The Milky Way – our home galaxy of billions of stars in a spiral disk – blazes across the late summer sky as seen from Torrance Barrens Dark Sky Preserve, Ontario, Canada. The three brightest stars of the “Summer Triangle” are Vega (upper edge, left of centre), Deneb (bottom left) and Altair (just above centre, toward right edge). Free hydrogen gas appears as reddish-magenta patches. The winding dark lanes are clouds of cold foreground gas that obscure the light from millions of stars that lie beyond.

The Moon will rule out the next two weekends for astronomy, so it’s time to go canoeing in Algonquin Park.  The next good astronomy weekend will be Oct. 4-6, near New Moon.

 

 

 

The Solstice…

sun

By: Michael Watson, LLB

… arrived early this morning at 05.04 GMT (01.04 EDT).  In the northern hemisphere we call it the summer solstice, and south of the equator it’s the winter solstice, so astronomers tend to call it simply the June solstice.  It is the instant during the year when planet Earth is tilted on its axis most directly in the direction of the Sun, so that the Sun appears highest in the sky at local noon in the northern hemisphere, and lowest in the sky at local noon in the southern hemisphere.

It also marks the day in the year when the Sun is above the horizon for the longest duration of the 24-hour day.  For Toronto, the Sun will be above the horizon for 15 hr, 27 min.  For Edmonton, the duration of sunlight increases to 17 hr, 3 min.  At and north of the Arctic Circle, the Sun never sets and there is 24 hours of sunlight.

The date of the June solstice is June 21 for three years in a row, and then it’s June 20 for one year, before returning to June 21 for another three years.  This is caused by the extra day that we insert into the calendar once every four years during Leap Year, in order to keep our annual calendar aligned as closely as possible to Earth’s position in its annual orbital motion around the Sun.

So what’s the etymology of the word “solstice“?  From the Online Etymology Dictionary:

mid-13c., from Old French solstice, from Latin solstitium “point at which the sun seems to stand still,” from sol “sun” (see sol) + past participle stem of sistere “to come to a stop, make stand still”

What does it mean to say that “the Sun seems to stand still”?  What this refers to is that between December and January, the Sun appears to move progressively northward in the sky, until at the solstice it reaches the most northerly point in the sky for the year (exactly on the border between the constellations Taurus and Gemini).  On June 21 the Sun comes to a stop in its northward motion, reverses direction, and from then on moves south in the sky until it reaches its most southerly point in the constellation Sagittarius on December 21.  So the “standing still” refers to the Sun ciming to a stop in its northward motion and reversing its motion from north to south in the sky.

Enjoy the start of summer, everyone!

The Moon, on a new mount

Toward the end of last night’s Great Leafs Collapse, the waxing crescent Moon was gliding down the north-western sky just above the bright planet Jupiter.  This was the first chance that I had to try photographing through the telescope on a new computerized telescope mount that arrived two weeks ago, rather than using only a long telephoto lens mounted on a stationary tripod.  The advantage of using a proper telescope mount is that a motor turns the telescope and therefore the camera very precisely to counteract Earth’s rotation, meaning that you can use long time exposures, and the stars remain pinpoints of light, rather than appearing as streaks across the photograph.
 
This is one of last night’s first photos using a Nikon D800 camera body through the telescope.  In effect the telescope acts as a 1000 mm, f/8 super-telephoto lens.  This is a 6-second exposure at ISO 100.  A first glance at the photo, in comparison with previous photos of the Moon made through a telephoto lens, shows how much greater the resolution is through a large piece of astronomical glass than through even a good telephoto lens.  In the original image dozens of stars can be seen.  Earthshine is very strong.
waxing crescent moon
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