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Whether it feels or looks like spring or like winter outside your home today, spring is officially here. It slipped under my pillow while I was still asleep this morning at 6:28 am ET here in the Northern Hemisphere.
Our ancestors my not have understood what was happening to our planet from a celestial viewpoint, but they were more careful observers of the world around them and definitely marked today as something significant. Ancient observers built devices, buildings and places like Stonehenge to measure and mark changes in the Sun’s movements. Of course, that was what they thought was happening – that the Sun was moving closer or further from Earth. They may have been wrong on that part, but they were able to mark that today was midway between the sun’s lowest path across the sky in winter and highest path across the sky in summer.
Though we visualize an equinox as occurring on the imaginary dome of Earth’s sky, it is a very real point on Earth’s orbit that is halfway between the two extremes of the sun’s path in your sky. “Your sky” because though the equinox occurs at the same time for all of us. The seasons are based on whether you are in the Northern or Southern Hemisphere.
One thing you can observe easily at each equinox (no Stonehenge required) is that the sun rises due east and sets due west from where you live. An equinox happens when the ecliptic – or sun’s path – intersects the celestial equator, that imaginary line above Earth’s equator.
Go outside around sunset and sunrise and notice the location of the sun on the horizon with respect to local landmarks. You can then use those landmarks to find those cardinal directions in the months ahead and observe how the sunrise and sunset points move southward or northward. I showed my young sons this many years ago by crudely tracking the sunrise moving from window to window during the year from the vantage point of our East-facing family room. It was a pretty interesting lesson in science.
Today the sun is on the celestial equator. It may be springlike outside or it may still seem like winter, but the new season has arrived.
The year just started but just a moment ago (22:49 Universal Time, 5:49 p.m. EST) Earth reached its closest point to the Sun for this year. We are at Earth’s perihelion (Greek peri “near” + helios “sun”).
Nothing extraordinary about this. Earth is closest to the sun every year in early January. This is isn’t why we moved into winter in the Northern Hemisphere. That is from the tilt of the planet, not the distance. In fact, we will be farthest away from the sun in early July, during our summer.
How much closer? About 3 million miles (5 million kilometers) closer. Big numbers but relatively not a big change in distance. Still, it wouldn’t be a bad idea to acknowledge the big star’s presence today. It’s already dark here in Paradelle, but the Sun is out there keeping us alive even on these wintry and cloudy days. Thanks, Helios!
A paper by a team of astronomers has folks talking about aliens – even though the paper never really discusses aliens. I find it intriguing, but, for me, the real thought experiment is something I will conclude with here.
These astronomers found an odd star that behaves in a way that is difficult to explain. The star is boringly called KIC 8462852. (Astronomers need to work on their naming conventions. “Death Star” would have been much better.) NASA’s Kepler mission has found this and many other stars. The brightness of this star dips, as do many stars. There is a slight dimming when a star has planets that orbit it and pass directly in front of the star as seen from Earth or the telescope. That is called a transit. The brightness dips about one percent or less. It is a way that exoplanets have been found. The dip will be periodic, repeating every few days, weeks, or months, depending on the size of the planet’s orbit.
KIC 8462852 is bigger, hotter and brighter than our Sun, but too faint to see with the naked eye. The dips in the light from it are not periodic but arbitrary and sometimes drop by 15 or 22 percent.
That’s not from a planet. Even a big Jupiter-sized one would only knock out that 1 percent of the starlight. But whatever it is, it’s big – maybe half the size of the star. I remember from elementary science class that you could fit more than a thousand Earths inside the Sun. Very big something out there.
The scientists probably suspected the furor and buzz this would get in the press and included obvious causes that can be eliminated. It’s not a flaw in the telescope, or debris from a planetary collision or a series of comets orbiting the star.
Physicist Freeman Dyson popularized the Dyson Sphere (not a fancy rolling ball vacuum cleaner) which speculated that we (or some aliens) might build thousands of gigantic solar panels and put them in orbit around their Sun to power the planet. This could expand until you had a gigantic sphere that completely enclosed the star.
It sounds like something from sci-fi (and it was in an episode of Star Trek: The Next Generation). This sphere would be dark in visible light but emit a lot of infrared light.
Have we observed an advanced alien civilization building a huge solar collectors?
An article published in The Atlantic by Wright and Boyajian is what has Internet-popularized this topic.
This is the dream of those who use radio telescopes to look for signals from out there and SETI (Search for Extraterrestrial Intelligence) and all the alien watchers and those who hope to make contact. (Yeah, watch the movie or read the book by that name.)
Here’s my big takeaway. The light we are seeing is 1500 light years away. If they were building 1500 years ago, I suspect that they are done by now. And if they are watching us, they are seeing us in about 505 A.D. We certainly look like a bunch of dopes who could easily be conquered, on a nice planet with water and resources. Do we really want to find them or have them find us?
It’s quite hot on this summer day here in Paradelle, but the Earth is just reaching its most distant point from the sun for 2015 as I type this line.
July 6, at 19:41 Universal Time or 3:41 p.m. Eastern Daylight Time in Paradelle is when our home planet is farthest from the sun. This happens every year in early July.
But it’s a hot day as I walked outside today to get lunch. We may be at our furthest distance (called aphelion) now, but, like most things, it is temporary.
Our journey around that precious star is not quite circular, so we are farther away from the sun in early July than at other times of the year. It’s five million kilometers farther from the sun than we will be in January but in the numbers of space and time that’s not a lot.
Look up at the ball of fire. It is 94,506,507 miles away (that’s 152,093,480 kilometers to most Earthlings) away. Not so far away; not too close. A nice cosmic distance.
We have circled the Sun once again.
Today we’re as far away as possible.
Apo – away – from Helios, Greek Sun god.
A summer-hot day, an imperfect circular journey.
Aphelion and 3,000,000 miles doesn’t matter much.
I have always had a sundial in my garden. It keeps you in touch with the movement of the Sun during the day and during the seasons.
My basic horizontal sundial shows a shadow from its style onto a surface marked with lines indicating the hours of the day. The style is the time-telling edge of the gnomon, the straight edge. As the sun moves across the sky, the shadow-edge aligns with hour-lines.
Sundials that directly measure the sun’s hour/angle must have that edge parallel to the axis of the Earth’s rotation to tell the correct time throughout the year. The style’s angle from the horizontal should equal the sundial’s geographical latitude, but in most inexpensive sundials the hour angles are off and cannot be adjusted. There are many other types of sundials.
Isaac Newton developed a convenient and inexpensive reflection sundial using a small mirror placed on the sill of a south-facing window. The mirror casts a single spot of light on the ceiling and, depending on the geographical latitude and time of year, the light-spot on the ceiling was drawn large enough to be accurate.
Most mass-produced sundials are not the most accurate timekeepers, but in mid-April time by the sun and time by my clocks agrees. Noon is noon in both places.
I adjust my sundial as the months move past me, but I suppose that is a bit of a cheat. This weekend the length of the day as measured by the midday sun is slightly less than 24 hours long. This discrepancy between my watch and the Sun accumulates until mid-May when noon on my sundial will be a few minutes earlier than the clock. After that the sundial middays will become slightly more than 24 hours long and by mid-June, they will match up again.
Cycles. Very much a part of our lives, whether we pass attention to them or not.
Our nearest star, the Sun, seems to move, rising and setting. But most people think of it as fixed at the center of our solar system as Earth and the other planets orbit around it. We have this model in our head from a textbook or animation of them clustered like a children’s crib mobile.
Our Sun is moving. Everything in space moves. It circumnavigates the Milky Way galaxy that is made up of several hundred billion stars.
Numbers for calculating the sun’s journey aren’t very exact. The Milky Way has a diameter of about 100,000 light-years. Can you imagine that? I can’t.
The Sun is traveling through the galaxy at about 140 miles per second. At that equally unimaginable speed, it would take about 230 million years for the sun to complete one circuit of the galaxy.
That’s what I am trying grasp today. A cosmic year – the length of the sun’s orbit around the Milky Way’s center
Where is the sun headed on this incredible journey? Astronomers say that our sun (and Earth and our little family of planets) are moving toward the star Vega and away from that brightest star, Sirius.
Poor Sun. It doesn’t even have a proper name like the other stars. Capitalize Sun to show some respect.
I can see Vega appearing over the northwest horizon in the early evening. I look at it and then at Sirius towards the southeast during winter.
I try to imagine the path between them. It runs through me, but it is like imagining infinity.