Thousands of years ago, ancient Greek astronomers calculated that the track of the Earth’s axis is constantly, even if in a very slow way, shifting in a uniform pattern. The variation is very similar to the manner a spinning top slowly leans one way and then another as it slows down. It is a wobble that happens as its axis alters direction.
This odd movement of the planet is due to a couple of factors, the most important of which is something called ‘precession’. Precession arises from the fact that the Earth is not a perfect sphere. It is in fact about twenty-seven miles longer around the Equator that it is around the Poles. The Earth then is oblate, or fat around the middle like middle-aged spread, but it is due to the rotation not to its age.
If you imagine the Earth with its Poles off centre. Then rotate that image and you will find that any point, except the exact centre of the axis, will move in a circle. But very, very gradually. So slowly that it takes 26,000 years to go full circle and get back to where it started from.
This point then, any point you choose, is very gradually shifting its position in relation to the stars because the axis is rotating too. The result of this is that, what we call the North Star (formally known as Polaris, which is in fact one degree off true North) will not be over our North Pole one day. In fact, by about 15,000 AD, Vega will be almost over the North Pole, although it will be about four degrees off true North. But even this will not endure, and by 28,000 AD, Polaris will be back above where it is nowadays.
One of the effects of the precession is that seasons change. They change the dates that they occur, so that Summer could come earlier or later. The remarkable thing about our calendar is that it is corrected for that (with the leap year). If it were not, the vernal or Spring equinox would move over 13,000 years from March 21st to September 21st., which is the date of the autumnal equinox, precisely half a year later.
It is for this reason that the precession of the Earth is generally referred to as the “Precession of the Equinoxes”. Although the precession of the equinoxes is very slow, it can be readily observed. The correct year of 325.25 days is the length of time from one vernal equinox to the next vernal equinox, however, it takes 20 minutes and 24 seconds longer for the Sun to appear in precisely the same place with relation to the stars behind it over the same period. This is why accurate star maps have to be stamped with the exact time and date to which they refer.
Owen Jones, the writer of this article, writes on many topics, but is currently involved with researching Franklin planner pages. If you have an interest in calendars, organizers or promotional calendars, please go over to our website now at Promotional Desk Calendars
Hybrid cars are on everyone’s lips. Twenty, forty, or fifty dollars for a full tank of petrol? Who in their right mind wants to pay that sort of money? However, frustrated, the gas customer sighs, but pays up. However, hybrid vehicles are applauded for the small amount of gas they need to operate, and they are flying off the lots of car dealerships each and everyday in increasing numbers.
But what about a plug-in hybrid? Most consumers have heard that these cars are great too. Then, a person might be asking him or herself, what exactly a plug-in hybrid is? How do they work, and what the difference between a plug-in hybrid and a regular hybrid is?
Plug-in hybrids are able to run solely on batteries, but they use petrol also. These kinds of hybrid cars have some of the characteristics of hybrid vehicles. They are also are very similar to electric vehicles.
Plug-in hybrid cars need to be recharged externally by connecting a plug to an electrical power source. The combustion engine in plug-in hybrid vehicles is used only as a back up. These cars can run only on batteries if desired, but it is expected that these kinds of hybrid cars be plugged in daily.
Hybrid cars can go just as many miles as a conventional car. Designed to go the extra mile where gas-mileage is concerned, hybrids can be driven on the motorway, in cities, or wherever else a person wants to travel.
On the other hand, plug-in hybrids are designed to handle commuter-type distances, meaning about twenty to sixty miles between destinations. This way, the plug-in hybrid does not have to use its back up combustion engine, but plug-in hybrids can go further using fuel too.
Hybrids help to reduce pollution, but they do still pollute the atmosphere. Compared with plug-in hybrids, hybrid cars still have a long way to go as far as pollution is concerned. Because plug-in hybrid cars can run solely on their battery power, they don’t have to emit waste fuel emissions at all.
Plug-in hybrids really do cut total greenhouse gas emissions and plug-in hybrids use virtually no oil at all, imported or not. Studies have revealed that electric hybrids emit at least 67% less greenhouse gases than gasoline cars. Since the product used to power plug-in hybrids is completely renewable, the difference in greenhouse gas emissions may be even greater than the study showed.
And so there you have it. Those are the main differences between plug-in hybrids and regular hybrid cars. It makes a big difference, but you would be surprised how little that matters at the current moment. And that’s only because plug-in hybrids are not being marketed to consumers at this present time. But this article should get you excited about the wonderful plug-in hybrid car, coming soon to a forecourt near you.
And it’s going to be a great debut too, since people already like the regular hybrid car models, but they haven’t seen anything yet until they see the new plug-in hybrid cars. However, for now, maybe we should just be satisfied with what we already have, because who knows? Before plug-in hybrid cars are brought out onto the forecourts, something even better might be introduced onto the market.
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