Summer Solstice

Today is the Summer Solstice. This is not, as some think, the day when the Earth is closest to the sun, that's almost six months away. This is the day when the Northern Hemisphere has the sun highest in the sky.

This is due to the tilt of the Earth's axis with respect to the orbital plane of the Earth's orbit around the sun. Though this tilt doesn't change, and (to a first approximation) the direction of the tilt doesn't change compared to the background stars. The direction of the tilt compared to the sun does change. This is due to the Earth's motion around the sun.

Today, the axis is tilted toward the sun (as viewed from the north) and so we have the longest day. The sun passes overhead at its 'highest'. From now on, the sun will rise and set further to the south, and it won't get as high in the sky. The days will begin to draw in.

The weather will still get a bit hotter though, as a rule, this is because a lot of the heat in the atmosphere is trapped (if it weren't we'd all freeze at night). This means it takes time to warm the earth up and cool it down again, so the hottest time tends to be after summer solstice, and the coolest after winter solstice.

I used the word 'tends' as local geography can change things, and weather is chaotic anyway!

Above, I used the phrase 'to a first approximation'. This is because the Earth's axis doesn't always point the same way, it wobbles like a top. This is an effect called precession, and is quite complicated, but very familiar. It's the same effect that causes a child's spinning top to wobble.

In the case of the Earth the period of the wobble is some 44000 years (from memory) - this is why on human timescales we don't have to worry about it too much!

Astronomy Picture of the Day

Today's Astronomy Picture of the Day is striking. However, should I be concerned that I spotted which of the two pictures was Earth without a moment of hesitation? It does make the point quite nicely that Earth is a varied planet and that it is unreasonable to categorise any other planet from one or two shots (Ice Planet Hoth or Forest Moon of Endor, anyone?).

Stargate SG1 once showed this very well by having Carter and O'Neill wind up in Antarctica, and Carter reports back 'Colonel? It's an ice planet. That's all there is as far as the eye can see. No chance.'. (Season 9 of SG1 is now filming).

Indian Moon Mission

As seen on slashdot, the Indian moon mission in 2-3 years time will have a component which will impact the surface in a trial for future soft landings. It'd be wonderful to aim for the moon, it's hard to believe that we're some 35 years after Apollo 11 and we have only visited the moon a handful of times. What's really odd is that by Apollo 13 the world had lost interest, until the accident, that is. To go to another world, that's something to fire the spirit!

ISRO has been busy recently with disaster management programmes as well as commercial satellites.

Yes, there are plenty of problems 'on earth' - but that should not prohibit research and exploration. Indeed, life wasn't perfect in Europe when Columbus sailed West. One never knows where the new discoveries which will help solve the 'at home' problems will come from. Indeed, one might argue that space research in India is providing much know-how and expertise which can provide jobs in related industries in a trickle down way.

Transit of Venus

Venus transitted the sun today. This means that the planet Venus passed in front of the face of the sun. This is a rare event, it happens in pairs a little over a century apart (the second of this pair is in 2012, and the one after that is in 2117).

A transit is not, it has to be said, visually spectacular. One would not know it was happening unless special steps were taken.

Historically, a transit is an important event as observations from a variety of positions, accompanied by accurate timing information allows us to measure the distances in the Earth/Venus/Sun system, and hence obtain the size of the solar system.

Today, the transit I am told, will be used to give information about volcanism on venus. In any event, it is a humbling thing to see Venus dwarfed by the sun, given that Venus is not dissimilar in size to the Earth.

I used a refracting telescope in a darkened room to view the transit. The telescope projected an image which was getting on for half a metre across. A screen was constructed so that sunlight which missed the telescope would be blocked.

There were a few minor sunspots visible, but one had to look hard.

Though I've only shown the telescope images, reasonable results were also obtained with binoculars, the image so formed was about 10cm in diameter.

A closeup of Venus in Transit
This is a close up image of Venus in transit across the sun.

The whole face of the sun
This picture shows the entire face of the sun projected onto a screen. The horizontal line is a join in the paper where we constructed the screen.

A comparison to the pinhole camera method
As the sun moved through the sky, we had to keep adjusting the alignment of the scope. This is a picture taken just before such an adjustment.

Here I am....
This picture shows me next to the projected image of the sun.

In one of the above pictures, there is a bright dot on the screen. The dot is an image of the sun formed when some light sneaked past a small chink in our screen. It's actually, several images overlapping. This is effectively forming a pinhole camera, or rather several pinhole cameras. It shows how inadequate the pinhole camera is compared to a lens based effort.

Insat Launch

Following yesterday's delay, InSat has been launched and is looking good. This story appears in many places online.

ISRO has just awarded two more launch contracts as a result.

Interestingly, India has it's own launch vehicle programme, yet it is relying on other agencies for it's recent launches, and is in talks with Lockheed. India has launched it's own satellites before, and is looking to enter the commercial launcher market.

Ariane Launch Delayed

Due to technical difficulties, the launch of Insat, an Indian Satellite, has been postponed due to problems with the telemetry.

ISRO was to launch Insat-3A on Ariane-5, of the ESA

Both ISRO and ESA have webpages, and ESA have just issued a media invitation about their imminent mission to mars, the Mars Express.

Mars Express is so called as in August the Earth and Mars will be in perihelic opposition. The mission will involve landing the Beagle 2 on the surface of the planet.

Personally, I'm quite fond of the Ariane series of rockets used by the ESA, they're vaguely reminiscent of something I've seen before....

Mapping the Moon

The ESA have released more information about their mission to map the moon. The mission, smart 1 will map The Moon (Luna) with X rays, and this should provide information about the formation of The Moon.

Quite frankly, this time I hope that things don't stall for 30 years, and we see the natural progression through the manned landings to a permanent base, of course, what we really need is a low cost way of leaving the planet. Yes, there are plenty of problems here to sort out (the common excuse), but that does not preclude exploring elsewhere.... after all, there were problems in Portugal before Columbus set out to find a new route to the East Indies. Exploration and pushing back the frontiers can't wait until everything is right 'at home', as it never will be.