The distances between the stars are so vast that they can make your brain melt. Take for example the Voyager 1 probe, which has been traveling at 35,000 miles per hour for more than 40 years and was the first human object to cross into interstellar space. That sounds wonderful except, at its current speed, it will still take another 40,000 years to cross the typical distance between stars.
Worse still, if you are thinking about interstellar travel, nature provides a hard limit on acceleration and speed. As Einstein showed, it's impossible to accelerate any massive object beyond the speed of light. Since the galaxy is more than 100,000 light-years across, if you are traveling at less than light speed, then most interstellar distances would take more than a human lifetime to cross. If the known laws of physics hold, then it seems a galaxy-spanning human civilization is impossible.
Unless of course you can build a warp drive.
Ah, the warp drive, that darling of science fiction plot devices. So, what about a warp drive? Is that even a really a thing?
Let's start with the "warping" part of a warp drive. Without doubt, Albert Einstein's theory of general relativity ("GR") represents space and time as a 4-dimensional "fabric" that can be stretched and bent and folded. Gravity waves, representing ripples in the fabric of spacetime, have now been directly observed. So, yes spacetime can be warped. The warping part of a warp drive usually means distorting the shape of spacetime so that two distant locations can be brought close together — and you somehow "jump" between them.
This was a basic idea in science fiction long before Star Trek popularized the name "warp drive." But until 1994, it had remained science fiction, meaning there was no science behind it. That year, Miguel Alcubierre wrote down a solution to the basic equations of GR that represented a region that compressed spacetime ahead of it and expanded spacetime behind to create a kind of traveling warp bubble. This was really good news for warp drive fans.
The problems with a warp drive
There were some problems though. Most important was that this "Alcubierre drive" required lots of "exotic matter" or "negative energy" to work. Unfortunately, there's no such thing. These are things theorists dreamed up to stick into the GR equations in order to do cool things like make stable open wormholes or functioning warp drives.
It's also noteworthy that researchers have raised other concerns about an Alcubierre drive — like how it would violate quantum mechanics or how when you arrived at your destination it would destroy everything in front of the ship in an apocalyptic flash of radiation.
Warp drives: A new hope
Credit: Primada / 420366373 via Adobe Stock
Recently, however, there seemed to be good news on the warp drive front with the publication this April of a new paper by Alexey Bobrick and Gianni Martre entitled "Introducing Physical Warp Drives." The good thing about the Bobrick and Martre paper was it was extremely clear about the meaning of a warp drive.
Understanding the equations of GR means understanding what's on either side of the equals sign. On one side, there is the shape of spacetime, and on the other, there is the configuration of matter-energy. The traditional route with these equations is to start with a configuration of matter-energy and see what shape of spacetime it produces. But you can also go the other way around and assume the shape of spacetime you want (like a warp bubble) and determine what kind of configuration of matter-energy you will need (even if that matter-energy is the dream stuff of negative energy).
Warp drives are simpler and much less mysterious objects than the broader literature has suggested.
What Bobrick and Martre did was step back and look at the problem more generally. They showed how all warp drives were composed of three regions: an interior spacetime called the passenger space; a shell of material, with either positive or negative energy, called the warping region; and an outside that, far enough away, looks like normal unwarped spacetime. In this way they could see exactly what was and was not possible for any kind of warp drive. (Watch this lovely explainer by Sabine Hossenfelder for more details). They even showed that you could use good old normal matter to create a warp drive that, while it moved slower than light speed, produced a passenger area where time flowed at a different rate than in the outside spacetime. So even though it was a sub-light speed device, it was still an actual warp drive that could use normal matter.
That was the good news.
The bad news was this clear vision also showed them a real problem with the "drive" part of the Alcubierre drive. First of all, it still needed negative energy to work, so that bummer remains. But worse, Bobrick and Martre reaffirmed a basic understanding of relativity and saw that there was no way to accelerate an Alcubierre drive past light speed. Sure, you could just assume that you started with something moving faster than light, and the Alcubierre drive with its negative energy shell would make sense. But crossing the speed of light barrier was still prohibited.
So, in the end, the Star Trek version of the warp drive is still not a thing. I know this may bum you out if you were hoping to build that version of the Enterprise sometime soon (as I was). But don't be too despondent. The Bobrick and Martre paper really did make headway. As the authors put it in the end:
"One of the main conclusions of our study is that warp drives are simpler and much less mysterious objects than the broader literature has suggested"
That really is progress.
How do these little beasties detect light anyway?
When it comes to senses like ours, tiny single-celled organisms floating in the ocean don't have much going on. And yet, as Sacha Coesel, the lead author of a new study from University of Washington researchers, puts it: "If you look in the ocean environment, all these different organisms have this day-night cycle. They are very in tune with each other, even as they get moved around. How do they know when it's day? How do they know when it's night?"
The answer, according to Coesel and her colleagues, is four previously unknown groups of photoreceptors that may help these organisms detect day, night, and each other.
Light and dark are vital to these organisms. When the sun is up, they become energized and grow. Cell division occurs at night when the darkness' ultraviolet wavelengths are less damaging to their DNA.
"Daylight is important for ocean organisms," says senior author Virginia Armbrust, "we know that, we take it for granted. But to see the rhythm of genetic activity during these four days, and the beautiful synchronicity, you realize just how powerful light is."
Photoreceptors and optogenetics
Credit: ktsdesign/Adobe Stock
This combination of optical technologies and genetics is giving researchers new insights into the workings of the brain, allowing them to, for example, turn on and off single neurons as they explore the brain's myriad pathways and interactions. Optogenetics also holds promise for better management of pain, and has cast new light on brain motor decision-making.
These new-found, naturally occurring photoreceptors may substitute for, or complement, human-made photoreceptors currently used in optogenetics. It's hoped that these newcomers will prove more sensitive and better equipped to respond to particular light wavelengths. Possibly because water filters out red light—the reason the ocean looks blue—the new photoreceptors are sensitive to blue and green wavelengths of light.
"This work dramatically expanded the number of photoreceptors — the different kinds of those on-off switches — that we know of," offers Armbrust.
Finding the new photoreceptors
Credit: Dror Shitrit/Simons Collaboration on Ocean Processes and Ecology/University of Washington
The researchers identified the previously undiscovered groups of photoreceptors by analyzing RNA they'd filtered from seawater samples taken far from shore. The samples were collected every four hours over the course of four days from the Northern Pacific Ocean near Hawaii. One set of samples was collected from currents running about 15 meters beneath the surface. A second set sampled deeper down, gathering water from between 120 and 150 meters, in the "twilight zone" where organisms get by with little sunlight.
Filtering the samples produced protists—single-celled organisms with a nucleus—measuring from 200 nanometers to one tenth of a millimeter across. Among these were light-activated algae as well as simple plankton that derive their energy from the organisms they consume.
Under-appreciated, tiny drivers of sea health
The new photoreceptors help fill in at least one of the blanks in our knowledge of the countless floating communities of microscopic creatures in our seas, communities that have a far greater impact on our planet than many people realize.
Says Coesel, "Just like rainforests generate oxygen and take up carbon dioxide, ocean organisms do the same thing in the world's oceans. People probably don't realize this, but these unicellular organisms are about as important as rainforests for our planet's functioning."
Using modern tools, a team of astronomers uses celestial sleuthing to figure out when Vermeer painted his masterpiece "View of Delft."
- The origin of Vermeer's acclaimed landscape has long puzzled historians.
- The painting is of the artist's home town, but exactly when it was made is a mystery.
- A team of astronomers have uncovered clues hidden in the artwork.
Just 35 paintings done by Johannes Vermeer survive.
The best-known among these is his captivating "Girl with a Pearl Earring." Part of what makes it so arresting is Vermeer's masterful use of light — his model's eyes practically glow with life and intelligence, staring straight back into your own. You may not be as familiar with "View of Delft," a landscape that writer Marcel Proust declared "the most beautiful painting in the world." Vermeer's genius here makes viewing this masterpiece feel as if you're actually there, warmed by the morning sun that illuminates the scene across the water.
Or is it the afternoon sun? Not much is known about Vermeer's life, and people have puzzled over this landscape for years, trying to identify exactly the view it depicts and when Vermeer could have painted it. Some experts had tagged its source of light as coming from the west, while others felt that it must've been directly overhead.
Now a team of researchers from Texas State University led by astronomer Donald Olsen have solved the riddle, thanks in part to the uncanny manner in which Vermeer was able to capture the play of light and shadow. When was it painted? According to the study, it was September 3 or 4, 1659 at 8 a.m. from a second-story inn window.
The research is published in the March 2020 issue of astronomy magazine Sky & Telescope.
What did Vermeer paint?
Delft today, a bit to the right of the painter's view and closer-in
Image source: Hit1912/Shutterstock
Olson, along with fellow astronomer Russell Doescher and three students — Charles Condos, Michael Sánchez, and Tim Jenison — took a multidisciplinary approach to their sleuthing.
The first question to be resolved was the location from which Vermeer painted the picture, and what he was painting.
Says Olson, "The students and I worked for about a year on this project. We spent a lot of time studying the topography of the town, using maps from the 17th and 19th centuries and Google Earth."
They concluded that Vermeer was looking northward from the second story of an inn across the triangular Kolk harbor, located at the southern end of his hometown. The students mapped out the painting's landmarks with Google Earth and calculated the angles and distances to reveal that it represented a 42-degree-wide view of the harbor from Vermeer's vantage point. "Google Earth is spectacularly accurate when it comes to distances and angles, so we used it as our measuring stick," Sánchez says.
The online research was followed up with a physical visit to Delph by Olson and Droescher, during which the retired professors took their own measurements and an array of photographs to confirm and expand on the students' conclusions.
When did Vermeer paint it?
Image source: Mauritshuis, The Hague/Big Think
Important clues can be found in the Nieuwe Kerk tower, located to the right of landscape's center. Some experts concluded, for example, that the painting had been done in 1660, but the tower rules out that possibility. While Vermeer's rendering shows the openings in the belfry as being empty, carillon bells — still present today — were installed there starting in April 1660. This would still leave the early months of 1660, except that in Delft there would be no leaves on the painting's trees before late April or early May. So much for 1660.
As for the time, look at the clock in the picture. To many, the clock has two hands that show a time just after 7 a.m. The authors of the new research noticed in other paintings from the period that the two hands of a clock were always lined up. Further research revealed, however, that clocks of this period didn't actually have two hands — they had just one, an hour hand. With this in mind, Vermeer's clock looks a lot more like 8 a.m.
Finding the date was a bit trickier, but again the octagonal Nieuwe Kerk tower provided an answer. Each of the tower's eight corners has its own stone column. The right side of the center-most column is lit, while its left is in shadow. On the next column to the left, however, is a thin sliver of light not blocked by the center column. Trusting Vermeer's careful depiction of light and shadow, the team was able to use this subtle detail to deduce the precise angle of sunlight shown in the painting. "That's our key," says Olson. "That's the sensitive indicator of where the sun has to be to do that, to just skim the one projection and illuminate the other. The pattern of light and shadows was a sensitive indicator of the position of the sun."
The team used astronomical software to identify any days on which the sun was at precisely that angle around 8 in the morning. The software returned two periods, one in April 1660, which was discarded for the reasons noted above, and the other around September 3-4, 1659.
Art takes time
The days identified by the Texas State researchers are most likely those on which Vermeer made the preliminary observations from which he executed the painting. Says Olson, "Vermeer is known to have worked slowly. Completing all the details on the large canvas of his masterpiece may have taken weeks, months or even years."
Still, "His remarkably accurate depiction of the distinctive and fleeting pattern of light and shadows on the Nieuwe Kerk suggests that at least this detail was inspired by direct observation of the sunlit tower rising above the wall and roofs of Delft."
And now we know when.
Olive oil leads to the discovery of a law that applies to atoms, superconductors, and even high energy physics.
- Physicists at the Dutch research institute AMOLF used olive oil in an experiment on light phase transitions.
- The scientists found that light would behave the same way in atoms, superconductors, and high energy physics.
- The discovery can lead to applications in new computing and sensing systems.
The dressing in your salad might redefine science if you look carefully enough. Researchers in the Netherlands used a drop of olive oil to discover a new universal law of phase transitions.
The research was carried out by the Interacting Photons group of the AMOLF institute, which focuses on fundamental physics. The experiment involved dropping olive oil into an optical cavity system of photons bouncing back and forth between two mirrors. It was set up to explore how light goes through phase transitions the way it would in boiling water, for example.
What's fascinating, this system had "memory" in how the oil made photons interact with themselves, as the group leader Said Rodriguez explained. "We created a system with memory by placing a drop of olive oil inside the cavity", said Rodriguez. "The oil mediates effective photon-photon interactions, which we can see by measuring the transmission of laser light through this cavity."
The research team, which also included Rodriguez's PhD students Zou Geng and Kevin Peters, increased and decreased the distances between the mirrors at different speeds and noted how light transmitted through the cavity was affected. They saw that the direction in which the mirrors moved influenced how much light got through the cavity, finding that "the transmission of light through the cavity is non-linear." This behavior of light, called hysteresis, is present in the phase transitions of boiling water or magnetic materials.
The scientists also increased the speed with which the oil-filled cavity opened and closed, observing that under such conditions the hysteresis was not always present. This allowed them to extrapolate a universal law. "The equations that describe how light behaves in our oil-filled cavity are similar to those describing collections of atoms, superconductors and even high energy physics," elaborated Rodriguez, adding: "Therefore, the universal behavior we discovered is likely to be observed in such systems as well."
An optical cavity formed by two mirrors used in the experiment. Light going through the cavity bounces between the mirrors until leaving to where the transmission is measured. The scientists filled this cavity with olive oil and moved the mirrors at varying speeds.
Credit: Henk-Jan Boluijt (AMOLF)
The researchers think their discovery may have potential applications in computing or sensing systems.
Check out their new study in Physical Review Letters.
A mind-blowing explanation of the speed of light
We have arrived: Big Think's most popular video of 2019 tells us light exists outside of time.
- Taking the #1 spot on Big Think's 2019 top 10 countdown, NASA's Michelle Thaller reminds us the only things that travel at the speed of light are photons.
- Nothing with any mass at all can travel at the speed of light because as it gets closer and closer to the speed of light, its mass increases. And if it were actually traveling at the speed of light, it would have an infinite mass.
- Light does not experience space or time. It's not just a speed going through something. All of the universe shifts around this constant, the speed of light. Time and space itself stop when you go that speed.