UFO'S of UAP'S, ASTRONOMIE, RUIMTEVAART, ARCHEOLOGIE, OUDHEIDKUNDE, SF-SNUFJES EN ANDERE ESOTERISCHE WETENSCHAPPEN

Star trails over GMT summit by Yuri Beletsky Nightscapes.

Star trails over the planned site of the Giant Magellan Telescope in the Atacama Desert in Chile. Image via Yuri Beletsky Nightscapes.

Star trails are the continuous paths created by stars, produced during long-exposure photographs, as shown on this page. In other words, the camera doesn’t track along with the stars’ apparent motion as night passes. Instead, the camera stays fixed, while, as the hours pass, the stars move. The resulting photos show the nightly movement of stars on the sky’s dome.

Star trails reflect Earth’s rotation, or spin, on its axis. The Earth rotates full circle relative to the backdrop stars in a period of about 23 hours and 56 minutes. So, as seen from Earth, all the stars go full circle and return to the same place in sky after this period of time, which astronomers call a sidereal (stellar) day.

View larger. | Star trails (plus meteor) photo taken by Guy Livesay. Thank you, Guy! If you aim your camera northward in a long-exposure photo, the star trails will be seen to track around the north celestial pole. In fact, the stars move counter-clockwise around the sky’s north pole in the course of every night.

Montauk Point lighthouse. Photo: Neeti Kumthekar

Montauk Point lighthouse. Photo via Neeti Kumthekar.

What this means is that, if you’re standing out under the stars, you see them move across the sky as night passes. Stars rise in the east, arc across the sky and set in the west, just as the sun does.

Stars near the celestial poles produce the smallest circles while those near the celestial equator produce the largest. The stars – like the sun during the daytime – move from east to west across the sky each and every night. Each and every star moves 15 degrees westward in one hour.

Star trails are really arcs, or partial circles, whose ever-circling motions forever tabulate the great passage of time.

Sometimes you can get cool non-star effects into your photo, as Michael A. Rosinski did in this August 2014 photo.

Sometimes you can get cool non-star effects into your shot, as Michael A. Rosinski did in this photo.

Ken Christison captured these glorious around Polaris, the North Star, on February 15, 2013. He wrote,

Ken Christison captured these glorious star trails around Polaris, the North Star. He wrote, “For the most common and often the most spectacular star trails, you want to locate Polaris and compose the image so it is centered horizontally and hopefully you can have a bit of foreground for reference.”

EarthSky Facebook friend Ken Christison has some wonderful photos of star trails. He said the equipment needed for making startrails is pretty simple:

First, a camera that allows manual settings so you can set your f/stop and shutter speeds, as well as ISO.

Next, a wide angle lens, the wider the better.

A good steady tripod is a must.

Some cameras will have a built in intervalometer which can be set to shoot the desirable number of frames. In some cases the intervalometer has a bit of lag between shots, which is the reason I use a separate, remote attached to the camera that holds the shutter down and when the camera is set in continuous shooting mode will shoot 100 frames in succession with very little gap.

The remote I use is a simple one that can be found on eBay and uses a couple AAA batteries that last quite a while. I just use the remote controller attached to the 10 pin connector. There is no need to use the wireless receiver in this case.

I use a shutter speed of 30 seconds, ISO of 400 to 800, and with my 14-24mm lens at 14mm, shoot it wide open at f/2.8.

Next, he said, you’re ready to capture your star trail:

Make sure the camera is level, and after focusing on a star, make sure the autofocus is turned off. Then, using the settings mentioned above, click the shutter and stay around long enough to know that the shutter is actually actuating. I normally go back in the house, set the timer on our kitchen stove for 45 minutes, and do other things while the camera does its work.

When the timer sounds, go back out and reset the remote by turning it off, waiting for the shutter to close, then reset quickly.

Finally, you’ll want to process your photo. Ken said:

This is one of the most important elements in making star trail images. The program I use is free, works well and is simple to use: http://www.startrails.de/html/software.html.

One other program that I have heard works well and is also free is StarStax: http://www.markus-enzweiler.de/software/software.html.

Thank you, Ken!

Visit Ken Christison’s Flickr page.

A 2-hour-and-15-minute star trail image from March 21, 2014. Our friend Ken Christison in North Carolina captured this image. He wrote,

A 2-hour-and-15-minute star trail image from March 21, 2014. Our friend Ken Christison in North Carolina captured this image. Want to see what a single frame of this image looked like? See the photo below.

A single frame of the star trail image above, with the elements labeled. Thank you, Ken Christison of Conway, North Carolina!

Composite image of star trails over Baja, California, from EarthSky Facebook friend Sergio Garcia Rill. This image is the product of 80 separate photographs. Thank you, Sergio!

You can also create a star trail of sorts with our local star, the sun. EarthSky Facebook friend Matthew Chin in Hong Kong created this sun trail on October 5, 2013. Thank you, Matthew!

View larger. | Star trails over Monument Valley on September 27, 2013 from Victor Goodpasture. The bright object is the moon. Thank you, Victor!

View larger. | Or you can create a moon trail. Star trails and moon trail over Monument Valley from Victor Goodpasture. The bright object is the moon. See more from Victor at Professional Digital Photography on Facebook.

Bottom line: Star trails are the continuous paths created by stars, produced during long time exposure photographs, as shown in the photos on this page.

A reasonably realistic simulation of falling into a black hole shows how space and time are distorted, and how light is blue shifted as you approach the inner or Cauchy horizon, where most physicists think you would be annihilated. However, a UC Berkeley mathematician argues that you could, in fact, survive passage through this horizon.

By Robert Sanders/Berkeley News

In the real world, your past uniquely determines your future. If a physicist knows how the universe starts out, she can calculate its future for all time and all space.

But a UC Berkeley mathematician has found some types of black holes in which this law breaks down. If someone were to venture into one of these relatively benign black holes, they could survive, but their past would be obliterated and they could have an infinite number of possible futures.

Such claims have been made in the past, and physicists have invoked strong cosmic censorship to explain it away. That is, something catastrophic – typically a horrible death – would prevent observers from actually entering a region of spacetime where their future was not uniquely determined. This principle, first proposed 40 years ago by physicist Roger Penrose, keeps sacrosanct an idea – determinism [cause and effect] – key to any physical theory.

That is, given the past and present, the physical laws of the universe do not allow more than one possible future.

But, says UC Berkeley postdoctoral fellow Peter Hintz, mathematical calculations show that for some specific types of black holes in a universe like ours, which is expanding at an accelerating rate, it is possible to survive the passage from a deterministic world into a non-deterministic black hole.

What life would be like in a space where the future was unpredictable is unclear. But the finding does not mean that Einstein’s equations of general relativity, which so far perfectly describe the evolution of the cosmos, are wrong, said Hintz. He said:

No physicist is going to travel into a black hole and measure it. This is a math question. But from that point of view, this makes Einstein’s equations mathematically more interesting. This is a question one can really only study mathematically, but it has physical, almost philosophical implications, which makes it very cool.

Hintz and his colleagues published a paper describing these unusual black holes in January 2018 in the journal Physical Review Letters.

Beyond the Event Horizon

Black holes are bizarre objects that get their name from the fact that nothing can escape their gravity, not even light. If you venture too close and cross the so-called event horizon, you’ll never escape.

For small black holes, you’d never survive such a close approach anyway. The tidal forces close to the event horizon are enough to spaghettify anything: that is, stretch it until it’s a string of atoms.

Still image taken from an animation by Andrew Hamilton, based on supercomputer simulation by John Hawley.

But for large black holes, like the supermassive objects at the cores of galaxies like the Milky Way, which weigh tens of millions if not billions of times the mass of a star, crossing the event horizon would be, well, uneventful.

Because it should be possible to survive the transition from our world to the black hole world, physicists and mathematicians have long wondered what that world would look like, and have turned to Einstein’s equations of general relativity to predict the world inside a black hole. These equations work well until an observer reaches the center, or singularity, where in theoretical calculations the curvature of spacetime becomes infinite.

Even before reaching the center, however, a black hole explorer – who would never be able to communicate what she found to the outside world – could encounter some weird and deadly milestones. Hintz studies a specific type of black hole – a standard, non-rotating black hole with an electrical charge – and such an object has a so-called Cauchy horizon within the event horizon.

The Cauchy horizon is the spot where determinism breaks down, where the past no longer determines the future. Physicists, including Penrose, have argued that no observer could ever pass through the Cauchy horizon point because they would be annihilated.

As the argument goes, as an observer approaches the horizon, time slows down, since clocks tick slower in a strong gravitational field. As light, gravitational waves and anything else encountering the black hole fall inevitably toward the Cauchy horizon, an observer also falling inward would eventually see all this energy barreling in at the same time. In effect, all the energy the black hole sees over the lifetime of the universe hits the Cauchy horizon at the same time, blasting into oblivion any observer who gets that far.

You Can’t See Forever in an Expanding Universe

Hintz realized, however, that this may not apply in an expanding universe that is accelerating, such as our own. Because spacetime is being increasingly pulled apart, much of the distant universe will not affect the black hole at all, since that energy can’t travel faster than the speed of light.

A spacetime diagram of the gravitational collapse of a charged spherical star to form a charged black hole. An observer traveling across the event horizon will eventually encounter the Cauchy horizon, the boundary of the region of spacetime that can be predicted from the initial data. Hintz and his colleagues found that a region of spacetime, denoted by a question mark, cannot be predicted from the initial data in a universe with accelerating expansion, like our own. This violates the principle of strong cosmic censorship.

Image via APS/Alan Stonebraker.

In fact, the energy available to fall into the black hole is only that contained within the observable horizon: the volume of the universe that the black hole can expect to see over the course of its existence. For us, for example, the observable horizon is bigger than the 13.8 billion light-years we can see into the past, because it includes everything that we will see forever into the future. The accelerating expansion of the universe will prevent us from seeing beyond a horizon of about 46.5 billion light-years.

In that scenario, the expansion of the universe counteracts the amplification caused by time dilation inside the black hole, and for certain situations, cancels it entirely. In those cases – specifically, smooth non-rotating black holes with a large electrical charge, so-called Reissner-Nordström-de Sitter black holes – an observer could survive passing through the Cauchy horizon and into a non-deterministic world. Hintz said:

There are some exact solutions of Einstein’s equations that are perfectly smooth, with no kinks, no tidal forces going to infinity, where everything is perfectly well behaved up to this Cauchy horizon and beyond.

Hintz noted that the passage through the horizon would be painful but brief.

After that, all bets are off; in some cases, such as a Reissner-Nordström-de Sitter black hole, one can avoid the central singularity altogether and live forever in a universe unknown.

Admittedly, he said, charged black holes are unlikely to exist, since they’d attract oppositely charged matter until they became neutral. However, the mathematical solutions for charged black holes are used as proxies for what would happen inside rotating black holes, which are probably the norm. Hintz argues that smooth, rotating black holes, called Kerr-Newman-de Sitter black holes, would behave the same way. Hintz said:

That is upsetting, the idea that you could set out with an electrically charged star that undergoes collapse to a black hole, and then Alice travels inside this black hole and if the black hole parameters are sufficiently extremal, it could be that she can just cross the Cauchy horizon, survives that and reaches a region of the universe where knowing the complete initial state of the star, she will not be able to say what is going to happen. It is no longer uniquely determined by full knowledge of the initial conditions. That is why it’s very troublesome.

Hintz’s paper has already sparked other papers, one of which purports to show that most well-behaved black holes will not violate determinism. But Hintz insists that one instance of violation is one too many. He said:

People had been complacent for some 20 years, since the mid ‘90s, that strong cosmological censorship is always verified. We challenge that point of view.

Bottom line: A UC Berkeley mathematician suggests that there are some types of black holes in which the law of determinism breaks down.