Tag: space

Temporo-Spatial Synesthesia

Carol Steen / American Synesthesia Association

Synesthesia of the Day – Temporo-Spatial Synesthesia

Temporo-Spatial Synesthesia, also known as Time-Space Synesthesia, mixes the senses of space and time. People with this form of synesthesia see time as having a visible form. When thinking about the year, they might see it as a circle wrapped around them. A week or a month might be a sequence of rectangles laid out in a consistent pattern. A day is often a circle. Whatever form it takes for them, it does so consistently. For some, in addition to the shape, different parts can have different colors.

Credit Dankonikolic – CC-BY-SA – tap for larger

For as long as I can remember my year has been egg-shaped, with the pointy end centered on the last week in December and the broad end comprising the summer, particularly July and August. I know that makes the oval asymmetrical, with the spring side being longer than the autumn side, but that’s my egg. Depending on where I am looking in the year, I might see the months stretching out ahead and curving to the right, or behind and curving to the left. The winter end is darker and the summer lighter. The spring side is greener and bluer, while autumn is yellower and redder. There are many more details that show themselves under closer looking, and everything looks different depending on where on the year I am. I did not know that this was a form of synesthesia. If I had thought about it, I would have assumed that it was the same for everyone. Neither of these images looks like my year.

My months are graduated segments of the track of my year. My weeks are straight pieces with humps for the weekends. They can be parts of a month, or they can be isolated. My days are two twelve hour circles, bright or dark depending on the time. It seems obvious that these shapes are the result of how time was depicted in the culture I grew up in. I’m glad I grew up with analog clocks.-)

Here are a couple of links. This one is by a woman who tells a story clearly and well. This one is for people who like and understand phrases like projector-associator distinction and visual salience.

Does your year have a shape?

rjb

Will Pluto Be a Planet Again?

And will the Moon soon be one too? As mentioned in my post Size – Solar System, Pluto lost its planetary designation over ten years ago. In 2006, the International Astronomical Union demoted Pluto from planet status to that of Kuiper belt object. Pluto didn’t meet all of their criteria to be called a planet. While it orbits the Sun without being the moon of another object, and it has enough gravity to form itself into a spherical shape, without having so much that it ignites a fusion reaction like a star — two of their criteria — it hasn’t cleared its orbital zone of most other bodies — their third criterion. There are a lot of other trans-Neptunian bodies out there, especially in the region called the Kuiper Belt. Pluto was relegated to the status of just another Kuiper Belt object (KBO). I agreed with them. Even though their criteria are incomplete and somewhat arbitrary, I think Pluto should be grouped with the other KBOs, rather than with the major planets. Rather than having a nearly circular orbit on or near the plane of the ecliptic, it has a very elliptical orbit canted at 17.16 degrees to the orbits of the planets. I think it should be called a minor (dwarf) planet, like Eris, another trans-Neptunian object, or Ceres, the largest asteroid belt object.  Many people disagree with me, though.  When the International Astronomical Union demoted Pluto, a great howl went up in defence of the little planetoid.  Now there is a movement afoot to change the definition of planet so Pluto can regain its previous status.  If they are successful, then there could be more than a hundred more planets added to the Solar System.

The key change the team is hoping to get approved is that cosmic bodies in our Solar System no longer need to be orbiting the Sun to be considered planets — they say we should be looking at their intrinsic physical properties, not their interactions with stars.

They want each body to be assessed on its own attributes, and not its relationship with other bodies. So what it orbits or how it does so would not come into it. Based on this, the Moon could become a planet, as could many of the moons of other planets. Here is their definition:

A planet is a sub-stellar mass body that has never undergone nuclear fusion and that has sufficient self-gravitation to assume a spheroidal shape adequately described by a triaxial ellipsoid regardless of its orbital parameters.

Put simply, anything massive enough to be round, but not as massive as a star. Anything up to and including what were formerly called brown dwarf stars (About 15-75 times as massive as Jupiter. See my post Size – Stars.) This would include a large and growing number of objects in the Solar System, and in other extrasolar systems, as well as any qualifying bodies that are not associated with any star. Those so-called “rogue” planets.

What do you think? Is it worth all that just to get Pluto its planetary status back?

Source: NASA scientists have proposed a new definition of planets, and Pluto could soon be back – ScienceAlert

rjb

Milankovitch Cycles – Other


See the previous posts on Milankovitch cycles: orbital eccentricity, axial obliquity and axial precession.

There are two more cycles to consider in this increasingly complex story of the astronomical cycles affecting Earth’s long-term climate. The first is another form of precession. Similarly to the precession of Earth’s axis, which marks out a circle on the star field every 26,000 years, the ellipse of Earth’s orbit around the Sun also precesses. That is, the orbit itself revolves, with the apsides of the orbital ellipse — the points of nearest and farthest approach — revolving about every 112,000 years relative to the fixed stars. Combining orbital precession with axial precession means that on average it takes about 23,000 years for the equinoxes to go through one cycle and return to the same calendar date. This affects climate by changing where on the orbit the seasons occur.

Credit Krishnavedala – CC-BY-SA – Tap for larger.

The other cycle, and the last one we will look at, is orbital inclination. It turns out that the plane of Earth’s orbit around the Sun is tilted relative to the Sun’s equator, and also relative to the Solar System’s so-called invariable plane. The invariable plane can be thought of as the rotational plane of the whole Solar System, mostly defined by the big gas giants: Jupiter, Saturn, Uranus and Neptune. The plane of Earth’s orbit is tilted relative to that by 1.57 degrees. The tilt of our orbit rocks up and down on about a 100,000 year cycle. That is, our tilt relative to the Sun and the rest of the Solar System is not constant, but changes over time. This affects climate by changing the apparent tilt of our axis relative to the Sun, affecting seasonal variation. Depending on the tilt of our orbit relative to the Sun, the same axial orientation relative to the fixed stars results in varying tilt relative to the Sun.

Credit Lasunncty – CC-BY-SA – Tap for larger.

The Milankovitch cycles, and the others that weren’t known in his time, are well understood, and their effect on Earth’s climate is well accepted by climatologists. That doesn’t mean that we’ve got it all sewed up. There is the matter of the well established 100,000 year cycle in glaciation matching the 100,000 year orbital cycles, while those cycles have the weakest effect on climate. Then there’s an unexplained change from a 41,000 year ice age cycle that lasted for two million years, to the 100,000 year one that’s been in force for the last million. And there are others. There is still plenty of work for climatologists.

To recap: We have looked at the astronomical events that Milutin Milankovitch considered to be implicated in Earth’s Ice Ages. We began with a brief look at his life, then followed up with the three main cycles examined by him: orbital eccentricity, axial obliquity, and axial precession. And now we have tacked on orbital precession and orbital tilt. All of these things, and possibly others not yet discovered, interact in a complicated dance that results in the recurring cycles of glaciation. Milankovitch pointed out that the most important effect is the amount and intensity of insolation at the mid-latitudes, particularly in the northern hemishpere’s summer. Warmer summers tend to prevent the buildup of snow and ice on the big continental land masses.

A note of caution: the Milankovitch cycles are seized upon as an example of natural forces that affect climate change, often with the hope that they will negate the reality of our current climate change, or at least absolve us of our responsibility for it. This is a false hope. If it were true, then the cycles should be trending toward warmer, but they’re not. Orbital eccentricity is increasing, which should promote a cooling trend. Axial tilt is decreasing, also normally leading to cooling. If anything, Earth should be cooling. The fact that it’s warming should make it clear that something else is counteracting the astronomical effects. The most economical hypothesis would seem to be that we are releasing the solar energy captured and buried by plants hundreds of millions of years ago, by burning the resulting fossil fuels. Compounding this is the insulating effect of the carbon dioxide released in the process, leading to a warming of the atmosphere. Don’t blame Milutin.

Now that I’ve put you through all this, here’s a link to a nine minute video that brings it all together.

rjb

Milankovitch Cycles – Precession


In the two previous posts on Milankovitch cycles — Eccentricity and Obliquity — we looked at the changing shape of Earth’s orbit around the Sun, and the changing tilt of Earth’s axis respectively. In this post we look at the other axial cycle: precession. In addition to changes in the tilt of the axis relative to the plane of our orbit, the direction that the axis is pointing in space changes over time. Over a period of about 26,000 years, it draws a circle on the star field. Presently the north end of the axis is pointing almost directly at Polaris, the pole star. About 13,000 years ago, near the end of the last great glaciation, it was pointing at the star Vega. The spinning planet is wobbling like a spinning top.


The effect of precession on climate is to continuously change where on our orbit the seasons occur. You can imagine that if we were on the opposite side of our wobble’s circle, then our summers and winters would be on the opposite sides of our orbit. Instead of winter in the northern hemisphere occuring during the part of the orbit when we are closest to the Sun, it would be at the farthest away. Northern hemisphere winters would be colder, but summers would be warmer, perhaps preventing the accumulation of ice and snow from season to season. Precession doesn’t affect the tilt of the axis, only where it’s pointing, so we still have seasons and they’re still affected by the obliquity cycle.

Now we have three cycles interacting: eccentricity at about 100,000 years, obliquity at about 41,000 years, and precession at about 26,000 years. You can see how complex this interaction is, and appreciate the work it took for Milankovitch to untangle it. He was doubted for a time, but these astronomical cycles are now accepted as important drivers of Earth’s climate. They came together to pull us out of the last glaciation, and now they are conspiring to push us into the next one. If we follow the established cycles, we should see a large part of the northern hemisphere’s continents covered in gigantic glaciers in the future.

Next up: some bonus extras.

rjb

Milankovitch Cycles – Obliquity


This is the second of the three main Milankovitch cycles that I said we’d cover in my original post on Milutin Milankovitch. The first cycle was Earth’s orbital eccentricity, or how elliptical the orbit is. We found that this changing eccentricity lays down a base cycle of about 100,000 years. In this post we’ll look at the first of two cycles involving Earth’s axis — obliquity, or axial tilt. It turns out that, while orbital eccentricity might be the dominant cycle, its actual effect on our climate is not the strongest.

Credit Dennis Nilsson – CC-BY.  Tap for slightly larger image.

Everyone knows from their early school years that the tilt of Earth’s axis, 23.5 degrees relative to the plane of our orbit around the Sun, is the cause of our seasons. But how would this affect the climate? Surely it would just continue to put us through the seasons wherever we are on the other cycles, and not contribute anything to the great climatic cycles. That might be the case were it not for the fact that the tilt is continuously changing, oscillating between 22.1 and 24.5 degrees. We are currently about midway, and progressing toward the low end with the least tilt. The entire obliquity cycle takes about 41,000 years.

The effect of axial tilt on long term climate is somewhat complex, but the final outcome is that decreasing tilt leads to a cooler climate. In more detail, a greater angle means that summers are hotter due to more intense insolation, while winters are cooler because the Sun’s rays are more oblique. This effect is strongest at higher latitudes. That’s important because it’s at the higher latitudes where snow and ice accumulation can lead to glaciation, and hotter summers can prevent that. When summers are cooler, snow cover can persist and build up from season to season. That’s especially true in the northern hemisphere where most of the continental land masses are, where snow can increase the albedo.

The amount of tilt to the axis can either add to the effect of the shape of the orbit, or subtract from it. When high tilt (warmer summers) combines with lower eccentricity (generally warmer,) we are at our warmest. When low tilt combines with high eccentricity, we are at our coolest. Tilt was maximum just under 11,000 years ago, when we firmly left the last great glaciation behind. It will reach minimum just under 10,000 years from now, when we should be well into the next glaciation. As we are still very close to the least eccentric, and therefore warmest, part of our orbital oscillation, the deepest part of the next ice age should be one or two obliquities in the future. Even so, these two cycles alone can’t account for Earth’s long term climate, or its ice ages.

We’ll look at the third main Milankovitch cycle, axial precession, in the next post.

rjb

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