Common sense tells us that effect of gravity moves at the speed of light

This appears to be an open question; it wasn't until 2002 that they were fairly sure and very recently (2017) that they established that, "assuming a delay of zero to ten seconds, the difference between the speeds of gravitational and electromagnetic waves, vGW − vEM, is constrained to between −3×10−15 and +7×10−16 times the speed of light."

I would have thought it was easier to apply common sense.

The light we see from the sun arrives from where the sun was 8 minutes 20 seconds ago (assuming for simplicity the earth is stationary and the sun moves round it).

If you measure the direction in which the earth is being pulled by the sun, you'd establish that it is being pulled towards where the sun was 8 minutes 20 seconds ago.

The light meter and gravity meter will be pointing in exactly the same direction; if not, there'd be all sorts of apparent weird wobbles (which would make measuring distances and so on a lot easier, as it happens).

And well done to these chaps, while we're on the topic. Instead of chasing non-existent Dark Matter, they are actually measuring and observing exciting stuff that actually happens.

"A Star Is Born"

From Wiki and Wiki

Jackson Maine, a protostellar cloud privately battling gravitational collapse and an alcohol and drug addiction, plays a concert in California to try and lose some excess energy through radiation. His main support is gas pressure Bobby, whose kinetic energy balances out the potential energy of Jackson's internal gravitational force.

After the show, the dust within Jackson becomes heated to temperatures of 60–100 K when he witnesses a performance by Ally, a waitress and singer-songwriter whose particles radiate at wavelengths in the far infrared where Jackson is transparent.

They spend the night speaking to each other, where Ally discloses to him that the dust is mediating his further collapse. Jackson invites Ally to his next phase of contraction. During the collapse she sings on stage with him. Jackson invites Ally to go on tour with him, and his density increases towards the center.

In Arizona, his middle region becomes optically opaque first. Ally and Jackson visit the ranch where his father is buried and where Jackson’s density reaches about 10−13 g /cm3, only to discover that a core region, called the First Hydrostatic Core, has formed where Jackson's collapse is essentially halted.

Angered at this betrayal, Jackson continues to increase in temperature and punches Bobby, who subsequently reveals that Jackson’s core temperature has reached about 2000 K, but the latter was too inebriated to notice.

"Asteroid capable of destroying London properties will pass within 17,000 miles of earth on Friday"

From The Daily Mail:

An asteroid capable of destroying family homes in London will skim past the Earth on Friday, approaching closer than many satellites.

Scientists say they are sure there is no chance of the 150ft (45.7m) wide space rock hitting the planet - but it could disrupt the housing market. That’s because investors are unwilling to put their money into land and buildings which could be wiped out in the coming days.

The asteroid, 2012 DA14, has been closely tracked since its discovery a year ago. It is predicted to reach its nearest point to the booming London property market at around 7.30pm UK time on Friday. Experts have calculated it will stay at least 17,200 miles (27,681km) away - easily far enough to be safe, but a very close shave in estate agent's terms.

Property market professionals have never observed such a narrow miss before. The object should be visible as a tiny downards blip in the prices of prime central London selling prices.

Astronomer and buy-to-let landlord Dr Dan Brown, from Nottingham Trent University, said: "The brief hiatus in transactions will be too faint for the naked eye but with access to the internet it should be visible if you know where to look on Rightmove. It will be low to the south-eastern horizon and moving quite quickly. You’ll be able to see it pass from Richmond to roughly the Docklands area from more or less from anywhere in the UK with broadband access, and it will be noticeable for about a week."

DA14 belongs to dangerous family of near-Earth objects (NEOs) that are small enough to be missed but large enough to cause serious damage to the housing market.

"What'chu talkin' 'bout, Willis?"

"Funnily enough, and don't take this the wrong way, I was talking about a brown dwarf."

I'm surprised they didn't blame "catastrophic sea level rises"

From the BBC:

A South Pacific island, shown on marine charts and world maps as well as on Google Earth and Google Maps, does not exist, Australian scientists say.

The supposedly sizeable strip of land, named Sandy Island on Google maps, was positioned midway between Australia and French-governed New Caledonia.

But when scientists from the University of Sydney went to the area, they found only the blue ocean of the Coral Sea. The phantom island has featured in publications for at least a decade.

You can still see it on Google Maps, go to New Caledonia and head north-west, but no doubt in a few days' time it will disappear for ever.
All a bit sad really. No doubt the nearby Katrina Shoals will be deleted shortly as well. It's like when they decided that Pluto was no longer a planet.

"Stars and strippers: Swingers complain lay-by used for dogging is blighted by star-gazers"

From The Daily Mail:

Police are staking out a lay-by after local swingers claimed it is being used as an "astronomy" site - causing queues of traffic waiting to get "a slot".

They claim dozens of cars are often seen trying to get into a lay-by big enough for just three couples, with weekends being the ‘busiest time’. The complaints from members of Croydon Kinky Couples, which uses a sheltered lay-by just a short walk from the main road in Kenley, south London, has prompted the police to set up a stake out at the lay-by...

One member of Croydon Kinky Couples, who only wanted to be known as AstroJohn, said: "They turn up with their telescopes in the night time with the excuse that they are star-gazing. Funnily enough, the same people turn up in the day time with the same telescopes and binoculars and claim to be ornithologists. The fact is, they are just weirdos who want to spy on us instead of bringing their wives along and joining in the fun."

The sex sessions are normally in the secluded lay-by area in Waterhouse Lane, just off Hayes Lane in Kenley.

Local resident Simon Lawson, 43, said: "Every time you drive past that lay-by you see cars queuing up to get a turn at voyeuring. Sometimes there are more Peeping Toms than actual toms, if you see what I mean. You can only get three couple in, at a push four if they're feeling very frisky, and sometimes the cars queuing up to watch cause quite a problem for other drivers, who just want to get to home.

He added: "The police need to go there on a Saturday night and just nick everyone there - it won’t be hard to catch them, they’ll be struggling to dismantle and hide their precious viewing equipment."

The Transit of Venus

Inspired by.

"Dark Sky Consultant"

From the FT:

The International Dark Skies Association, which has designated 16 areas in North America and Europe, will on Thursday unveil proposals to focus on some of England’s darkest skies as it creates a reserve in the Kielder area of Northumberland. The association reports increased interest from locations wanting dark sky designation to help reduce light pollution and encourage public awareness and tourism.

“We’re now becoming inundated with applications,” says Steve Owens, a Glasgow-based dark sky consultant who is chairman of the IDA’s development committee. “In the UK, astronomy tourism has become mainstream. It’s just caught the imagination,” he adds.

Light pollution means that more than 85 per cent of the UK’s population has never seen a truly dark sky. In fact, fewer people than ever can hope to step outside their front door at night and see the Milky Way. Kielder Water and Forest Park Development Trust and Northumberland National Park Authority will propose covering nearly 400 square miles of wild countryside. According to the Campaign to Protect Rural England, Northumberland has more dark skies than anywhere else in England.

Sounds like my kind of job! I also note that there are at least four organisations in on the act here, so plenty of jobs for my mates doing a bit of inter-agency co-ordination.

As to the 85% of the UK population, well duh, 85% of people live on the 5% of land that is towns and suburbs, which are lit up at night, the statistic is meaningless.

More NIMBY insanity

From the BBC:

Half of the UK's population cannot see many stars because the night skies are still "saturated" with light pollution, campaigners have warned. Some 53% of those who joined a recent star count failed to see more than 10 stars in the Orion constellation...

The problem remained despite attempts to curb street lighting, they said. They said that in 2010, local authorities collectively spent more than £500m on street lighting, accounting for 5% to 10% of each council's carbon emissions.

£500m = £8 per person, seems like splendid value to me. Of course, the cost per person of lighting up rural areas is far higher and the cost per person of lighting up urban areas, so if they want to turn off the street lights in rural areas, then great. I can't be bothered to do the workings, but I don't think you get much "carbon emissions" for £8 a year, do you?

UPDATE: Kj in the comments has done the workings. Street lighting causes about 0.4% of total CO2 emissions (to the extent that you worry about them), i.e. 35 kg out of 9 tonnes per person per year.

Emma Marrington, a rural policy campaigner for the CPRE, says: "When we saturate the night sky with unnecessary light, it damages the character of the countryside and blurs the distinction between town and country. But this isn't just about a spectacular view of the stars; light pollution can also disrupt wildlife and affect people's sleeping patterns."

WTF?

According to the ONS, only 19% of people live in rural areas and 81% of us live in urban areas. So if 47% of us can see enough stars, then the chances are that nearly everybody in the countryside can, as well as one-third of people in urban areas; that's the price you pay for better safety at night.

And how does street lighting at night "damage the character of the countryside"? It's a safety thing for pedestrians and motorists. Like I said, they're free to turn the lights off if they want, so all they'd see at night time would be... absolutely nothing, pitch blackness (I quite like the appearance of streetlights threading their way across the hills and valleys, but maybe that's just me). Would do that do enough to unblur "the distinction between town and country" for her?

The wildlife can managed just fine and if she has problem sleeping, then she might try buying thicker curtains, they're good for thermal insulation as well, so win-win.

Goldilocks

From The University Corporation for Atmospheric Research:

The Goldilocks Principle can be summed up neatly as "Venus is too hot, Mars is too cold, and Earth is just right." The fact that Earth has an average surface temperature comfortably between the boiling point and freezing point of water, and thus is suitable for our sort of life, cannot be explained by simply suggesting that our planet orbits at just the right distance from the sun to absorb just the right amount of solar radiation.

Our moderate temperatures are also the result of having just the right kind of atmosphere. A Venus-type atmosphere would produce hellish, Venus-like conditions on our planet; a Mars atmosphere would leave us shivering in a Martian-type deep freeze.


Instead, parts of our atmosphere act as an insulating blanket of just the right thickness, trapping sufficient solar energy to keep the global average temperature in a pleasant range. The Martian blanket is too thin, and the Venusian blanket is way too thick! The 'blanket' here is a collection of atmospheric gases called 'greenhouse gases' based on the idea that the gases also 'trap' heat like the glass walls of a greenhouse do.

*ahem*

From elsewhere on their site:

Venus - average distance from Sun 67 million miles
Earth - average distance from Sun 93 million miles
Mars - average distance from Sun 226 million miles

As the intensity of light received from an object is inversely proportional to the square of the distance, it'd be reasonable to expect the Sun's rays on Venus to be 193% as intensive as on Earth, and on Mars to be only be 17% as intensive on Earth. Which might have something to do with the temperature differences.

*/ahem*

What detracts from my argument is that the Moon's average temperature is about -36 C, 50 C colder than Earth*, despite it being the same average distance from the Sun, which I'd put down to a mixture of the Moon being paler in colour (so reflects more light) and not having a giant molten iron core, as well as it not having an atmosphere.

UPDATE: further to comments to this post, I have done a bit more reading and wish to retract and re-write that last paragraph, which I will cover in a later post.

* 21 C warmer than Mars, despite having no atmosphere at all.

Lunar quandary

Here's a photo of the Moon, which I took a few minutes ago, when it stood more or less due east from where I was standing. As you can see, it's not quite a full moon yet, and the bottom right hand corner is still in darkness, i.e. not lit by the Sun. What baffles me is that the Sun is somewhere behind, beneath and to the left of me (having set in the west) - so why is the bottom right hand corner still dark and not the top right hand corner? NB, the dark bit is not due to cloud cover, just ignore that.
Answers on a postcard.

UPDATE: As Stringersbeer points out in the comments,
it was a partial lunar eclipse. D'oh!

Those long December evenings ...

As we all well know, the winter solstice, the shortest day of the year is usually a couple of days before Xmas, so you'd expect the sun to rise later and set earlier every day until the solstice; and then to start rising earlier and setting later every day thereafter.

That turns out to be not quite true. According to this fine article, the earliest sunset is much earlier - around 13 December, and the latest sunrise is much later - 6 January. It's just that until the winter solstice, you are losing more in the morning than you gain in the evening; and thereafter you are losing less in the morning that you are gaining in the evening.

We live and learn. I'm sure that'll come in handy in a pub quiz one day.