All fired up on the sun
QUESTION
What causes sunspot cycles? The sunspot cycle, also known as the solar magnetic activity cycle, Schwabe or solar cycle, is an 11-year change in the sun’s activity driven by the flipping of the magnetic field.
During the cycle, the sun’s magnetic field becomes increasingly erratic, its activity reaches a maximum and it reverses. The sun settles back down before it begins again. The current cycle began in December 2019.
The cycle was identified in 1843 when German astronomer Samuel heinrich Schwabe recorded the periodic variation in the average number of sunspots after 17 years of solar observation.
The sun’s core consists of dense, ionised (electrically charged) gas. This roiling, boiling plasma generates a powerful magnetic field.
Like the earth’s magnetic field, the sun has north and south poles. Its magnetic field is much more powerful but also messier and more changeable. Our magnetic field flips only every 200,000 to 300,000 years.
As it approaches solar maximum, just before the flip, its magnetic fields become increasingly complex and the fields loop around and cross each other, cutting each other off and reconnecting.
This can cause a variety of changes on the photosphere, the sun’s outer shell from which light is radiated.
There are an increased number of sunspots, dark areas of particularly strong magnetic forces.
Sunspots are regions of reduced surface temperature caused by concentrations of magnetic flux that inhibit convection.
They are indicators of overall increased solar irradiance — during solar maximum, this output grows by about 0.07 per cent.
Large numbers of sunspots suggest the onset of further mass ejection phenomena such as solar flares and coronal mass ejections. These phenomena involve gigantic explosions of energy.
A solar flare is a tremendous explosion on the sun that happens when energy stored in twisted magnetic fields above the sunspots is expelled into space.
Coronal mass ejection is when a large cloud of energetic and highly magnetised plasma spews from the solar corona into space.
Astronomers use the analogy of firing a cannon to distinguish the two events. The solar flare is a diffuse release of energy like the muzzle flash; the coronal mass ejection is the cannonball, propelled forward in a targeted direction, which can cause significant radio and magnetic disturbances on earth.
Max Farrier, Lowestoft, Suffolk.
QUESTION Why do we say ‘many happy returns’ on a birthday?
THIS phrase means to wish someone a long life — that your birthday will return many more times — and dates back to Roman times.
The Latin phrase appears in Joseph Addison’s 1752 political discourse The Freeholder: ‘The usual salutation to a man upon his birthday among the Ancient Romans was Multos et Foelices; in which they wished him many happy returns of it.’
The english rendition is first recorded in 1789 in a letter from Lady Newdigate to her husband Sir Roger Newdigate, 5th Baronet: ‘Many happy returns of ye day to us, my Dr Love.’
Jancis Hill, Stratford-upon-Avon, Warks.
QUESTION If you sent a letter in 19th-century London, could you expect a reply within two hours?
My THS abound about the historical speed of the post. While it once was theoretically possible for a letter to have been delivered within two hours of posting, it required a particular set of circumstances.
The only way to guarantee sending a message and receiving a reply within two hours would be with a telegram, which meant a visit to a main Post Office.
It would be delivered to the recipient’s front door and they could dispatch a reply via the delivery boy.
Before World War I, there were several postal collections each day from London pillar boxes.
As well as morning and late afternoon, there were collections in the late morning and early afternoon. Most towns had a late collection from the central Post Office and sorting office.
It was possible to post a letter on a mail train at one of London’s mainline stations. This was common at euston on Friday evenings when people would post their pools coupons to Littlewoods in Liverpool.
Postal deliveries in the capital were made in the early morning, mid-morning and early afternoon.
So, it is feasible that a letter could be posted first thing in the morning, be collected, sorted and be back out of the sorting office in time for the midmorning delivery — provided it was being delivered within the same town or city postal district.
Mail was transported on the railways, not by road, with almost every train carrying bags of mail in the guard’s van.
So it was feasible for an employee working in Central London to post a letter home when they arrived for work and for it to be delivered in the suburbs later that day.
however, mail travelling between more distant towns and cities wasn’t usually delivered until the next day.
Rural areas have always had less frequent collections and deliveries because of the large areas covered.
World War I changed postal services. With so many postal workers serving in the Armed Forces and women being needed to work in more important industries, the number of collections and deliveries were reduced. They weren’t reinstated when the war ended.
There were further erosions to mail services during World War II.
Bob Cubitt, Northampton.