# The Universe Is Expanding, But How Fast Is Up For Debate (Physics)

In the 1920s, astronomer Edwin Hubble brought about the modern age of cosmology when he discovered that the universe is expanding at a predictable rate, which has since been called the Hubble constant. Nearly 100 years later, more precise measurements have sharpened his accuracy — but may also put our current understanding of physics in limbo.

At the turn of the 20th century, the hot topic in cosmological circles was nebulae. We could see them with telescopes, but we didn’t know how far away they were — were they interstellar clouds within the Milky Way, or were they far-off galaxies of their own? If you’ve ever wondered whether a light in the night sky is a satellite or a star, you know how difficult it is to tell the distance of things in space. In the early 1900s, Henrietta Swan Leavitt discovered what became known as Cepheid variables, a type of star whose brightness varied at a rate that could be used to calculate their absolute luminosity, or intrinsic brightness. That’s important because astronomers can use a star’s luminosity to measure its distance from us. A decade or so later, Edwin Hubble realized that many nebulae contained these variable stars, and could, therefore, make the important discovery that nebulae weren’t located in our own galaxy, but far beyond it, existing as galaxies in their own right.

Oh, but that’s not all. Next, Hubble compared these distance measurements with each galaxy’s velocity and found that the further away the galaxy was, the faster it was moving away from us. That led to the bombshell of the century: the universe was expanding. (To understand why more distant galaxies are moving faster, imagine a loaf of raisin-bread dough. When you put it in the oven, all of the raisins are evenly distributed, but as it rises in the oven, the raisins near the edges move outward faster than those in the center.) Hubble’s formula to determine the speed of a galaxy, called Hubble’s law, is v = H0d. H0 is, you guessed it, the Hubble constant, which astronomers have used ever since to judge the rate at which the universe is expanding.

When Hubble made this discovery, technology was not what it is today, to put it mildly. As a result, Hubble’s estimate for the value of the Hubble constant was pretty imprecise. One big reason for launching the Hubble Space Telescope in the 1980s was to get a more precise estimate for a number that at that time was somewhere between 50 and 100 km/sec/Mpc (kilometers per second per Megaparsec) — they wanted to whittle the accuracy down to at least 10 percent, which is still a wildly imprecise margin for science. Fast forward 30 years, and even more precise instruments such as the Wilkinson Microwave Anisotropy Probe (WMAP) honed the number to 69.3 km/sec/Mpc. Then in 2013, the expansion rate of the universe put on the brakes when the Planck satellite used background radiation from the Big Bang to find that the Hubble constant was closer to 67 km/sec/Mpc.

But in December 2016, a group called H0 Lenses in COSMOGRAIL’s Wellspring, or H0liCOW (get it?), used Einstein’s theory of general relativity to determine that the Hubble constant was a much faster 72 km/sec/Mpc. Despite its name, improved technology means that the Hubble constant keeps changing. What does that mean? A lot. It could mean that there are yet discovered elementary particles at play. It could mean that dark energy, which was previously blamed for shifts in the expansion rate, isn’t there at all, and is instead a theoretical form called phantom energy. This all would mean new physics and a drastic change in our understanding of the universe. But for now? It’s too soon to tell.

# Time Maybe Slowing Down – And Will Eventually Stop (Physics)

The universe is expanding at an ever-accelerating rate. At least, that’s what the vast majority of scientists would have you believe. But according to a team of Spanish physicists, it may not be the expansion of the universe that’s changing rate, but time itself. Time might be slowing down, and that means that it could eventually stop altogether.

To illustrate what José Senovilla and his team at the University of the Basque Country in Bilbao, Spain are getting at, think about what it sounds like when an ambulance passes you on the street, sirens blazing. As it drives away from you, the siren begins to drop in pitch. This is known as the Doppler effect, and it happens because the sound waves ever so slightly stretch as the ambulance drives away from you, meaning they reach you at a slower rate (i.e. a lower frequency).

But what if the laws of physics changed when that ambulance passed, and instead of its speed causing that drop in frequency, it was the passage of time? If time were slowing down, that would also make the sound waves reach you at a lower frequency. That’s essentially what Senovilla’s team is suggesting. We “know” the universe is expanding at an accelerating rate because galaxies further away from us have a greater redshift — light’s version of that ambulance Doppler effect — than galaxies closer to us, meaning they’re moving faster. But if time were slowing down, the light would just reach us at a lower frequency. We’d see the redshift, but it would be for a different reason.

This theory sounds outlandish, but it fixes some nagging problems. For the universe’s expansion to be accelerating, you need to come up with something to cause it. That’s where so-called “dark energy” comes in. This mysterious force is supposed to make up 68 percent of the universe, but we’ve never actually observed it. If time is slowing down instead, you don’t need dark energy at all. The mystery of dark energy is fixed since it never existed in the first place.

This theory sounds outlandish, but it fixes some nagging problems. For the universe’s expansion to be accelerating, you need to come up with something to cause it. That’s where so-called “dark energy” comes in. This mysterious force is supposed to make up 68 percent of the universe, but we’ve never actually observed it. If time is slowing down instead, you don’t need dark energy at all. The mystery of dark energy is fixed since it never existed in the first place.

But this theory gets weirder. That’s because it’s based on a principle in string theory that says our universe exists on the surface of a membrane — a “brane,” in string-theory speak — that itself exists inside a higher-dimensional space called the “bulk,” aka hyperspace. All branes can have different numbers of dimensions; ours happens to have three spatial dimensions and one time dimension, but others could have no time dimensions or multiple time dimensions. Dimensions in those other branes could even swing between different versions: space could become time and vice versa. That’s what the researchers think might be happening to our time dimension: It’s slowly turning into a space dimension. If it succeeded, our universe would be frozen in time and exist in four-dimensional space.

We’d experience this as a gradual slowing of time — so gradual, in fact, that for the first billion years or so, we’d only see its evidence in grand scales, like the movement of faraway galaxies. “Our calculations show that we would think that the expansion of the universe is accelerating,” Senovilla told New Scientist. “[Any] observation of dark energy could be evidence that our brane is changing signature and that time is disappearing.”

But if this sounds alarming, don’t worry: This won’t happen for billions of years. In the meantime, buck up! Life is longer than you thought.

# Time Crystals Break The Continuity Of Time (Quantum Mechanics)

In September 2016, a team of researchers from the University of Maryland announced that they had experimentally confirmed the existence of time crystals. That is, crystals that break the continuity of time. In March 2017, it was made official: time crystals are a new state of matter. Confused? Let’s break this down.

In physics, “spatial symmetry” refers to the way a feature stays the same no matter which way you observe it. If you were to walk all the way around a sphere, it would look the same at each point in your journey. That’s because it has continuous spatial symmetry. A cube, on the other hand, would look slightly different as you passed from one face to the next, but would look identical at each face. This means it “breaks” continuous spatial symmetry and instead has discrete spatial symmetry: you can only see the same thing from specific directions. That’s the essence of a crystal: it breaks continuous spatial symmetry.

Symmetry also applies to laws of physics like gravity (you’d see an apple fall the same way no matter how you were watching it) and, importantly, time. The gears on a clock, for example, move continuously at any given rate as they spin on an axis of rotation, so they have a kind of continuous temporal symmetry. Just as a crystal breaks continuous spatial symmetry, a time crystal would break continuous temporal symmetry: its “gears” spin on an axis, but only with specific rates of rotation.

The University of Maryland scientists successfully created a time crystal by using very low temperatures, a magnetic field, and lasers to trap a ring of positively-charged ions. “If this combination is put together just right, then this ion ring will enter its lowest energy state, also known as a ground state,” physicist Matt Lowry tells Curiosity. “It ends up that this ion ring time crystal actually rotates while in its ground state.” A system in its ground state shouldn’t be able to move, but time crystals do—in that symmetry-breaking way. Moving in a ground state means that the crystal could rotate forever without heating up or requiring additional energy — something the researchers say is an entirely “new phase of matter.”

# Could A Time Traveler Able To Kill Their Own Grandfather? (Science And Technology)

You’ve seen it in “Back To The Future.” You’ve seen it in “Futurama.” You’ve seen it in the 2009 reboot of “Star Trek.” It’s the grandfather paradox (or variations upon it), where somebody goes back in time and changes something so big that it causes an impossible scenario. But what is the grandfather paradox, how would it work, and what would happen if somebody actually pulled it off?

Here’s the most straightforward version of the paradox. Jim Bob III builds a time machine and goes back about 60 years, to when his grandfather, Jim Bob I, is a childless 20-year-old. He then shoots his grandpa dead in the street (Jim Bob III has some problems), meaning Jim Bob II is never born. But if Jim Bob II is never born, then Jim Bob III is never born. And if Jim Bob III is never born, then he never goes back in time and Jim Bob I is able to live a long and happy life. But then Jim Bob I goes on to have a messed-up grandson intent on causing paradoxes, and we’re right back at the beginning.

There’s one solution to this paradox that theorists keep coming back to, although it has some problems of its own. It’s called the Novikov self-consistency principle, and it basically states that any events that occur while traveling to the past are consistent with and identical to the events that occurred the “first time around.” In other words, there’s only one past, and if you end up traveling back there, then you were already there to begin with.

Confused? Actually, you’ve probably seen this the self-consistency principle play out already. In “Harry Potter and the Prisoner of Azkaban,” Harry is saved when a mysterious figure summons the Patronus of a stag to drive off a group of attacking Dementors. One trip through time later, he finds out that it was him who summoned that Patronus. And in “Game of Thrones” [spoiler alert for season six], Bran discovers that his acts in the present were responsible for Hodor’s unique speech impediment forming in the past (we won’t go into “how” since we’re trying not to break down at work today).

These pop culture examples don’t fix any paradoxes, per se, but they still show how the paradox would be fixed. The Patronus that saved Harry was there the first time Harry experienced it, and Hodor became Hodor because Bran had gone back in time all along. In other words, you can’t go back in time and kill your grandfather, because your grandfather was never killed in the first place. If you try, then you’ll fail, because your grandfather never died in the past.

Here’s the thing about the Grandfather Paradox: It’s only a paradox in certain versions of the space-time continuum. And until we actually succeed in going back, we’re not going to know exactly how our continuum works. But here are a few possibilities.

Fixed timeline

This is how the timeline shaped up in that episode of “Futurama,” and it’s the version that Novikov’s principle most clearly addresses. In this version, what’s past is past. “The ink is dry.” So when Fry thought that he had altered the timeline forever by leading his grandfather to his death, he was actually just playing out how the timeline had already went … which happened to mean that he turns out to be his own grandpa. Ick. Moving on …

Dynamic timeline

This is probably the most popular conception of how timelines work, even though it doesn’t really make a lot of sense when you think about it. It’s the kind of time travel that Marty McFly had to deal with. For him, the changes he made to the past were reflected in the present, which is how he nearly erased himself from existence by being more charming than his youthful father. But if the present changes when you change the past, then won’t you change too? And if you accidentally erase yourself from existence, then you won’t really have a chance to set it right. This is where paradoxes thrive, and where sci-fi writers just have to shrug and admit it’s more dramatic that way.

Multiverse timeline

This is the kind of timeline that goes down in the “Star Trek” reboot, and it conveniently sidesteps any potential paradoxes by saying that every trip to the past creates a new reality wherein that trip to the past occurred. The past of the reality you left behind is still set in stone, like a fixed timeline, but the new reality you’ve created can play out in any number of different ways. So Eric Bana’s villainous Nero didn’t have to worry about causing any paradoxes since the universe he was affecting didn’t have anything to do with the universe he came from. Sort of a “what happens in Vegas, stays in Vegas,” but with even more lasers.

# Phone Calls Create Stronger Bonds Than Text-Based Communications (Psychology)

New research from the University of Texas at Austin suggests people too often opt to send email or text messages when a phone call is more likely to produce the feelings of connectedness they crave.

They carried out an experiment on 200 people in which they asked those people to make predictions about what it would be like to reconnect with an old friend either via email or phone, and then they randomly assigned them to actually do it. Even though participants intuited that a phone call would make them feel more connected, they still said they would prefer to email because they expected calling would be too awkward.

But the phone call went much better than an email, researchers found.

In one another experiment, researchers randomly assigned strangers to connect either by texting during a live chat, talking over video chat, or talking using only audio. Participants had to ask and answer a series of personal questions such as, “Is there something you’ve dreamed of doing for a long time? Why haven’t you done it?” or “Can you describe a time you cried in front of another person?”

Participants didn’t expect that the media through which they communicated would matter, and in this case they also predicted that they would feel just as connected to the stranger via text as by phone.

But the researchers found when they really interacted, people felt significantly more connected when they communicated by talking than by typing. And, again, they found it wasn’t more awkward to hear each other’s voices.

In fact, the voice itself—even without visual cues—seemed to be integral to bonding, the researchers found.

Confronting another myth about voice-based media, researchers timed participants reconnecting with their old friend. They found the call took about the same amount of time as reading and responding to email.

According to researchers, the results both reveal and challenge people’s assumptions about communication media at a time when managing relationships via technology is especially important.

References: Amit Kumar et al. It’s surprisingly nice to hear you: Misunderstanding the impact of communication media can lead to suboptimal choices of how to connect with others., Journal of Experimental Psychology: General (2020). DOI: 10.1037/xge0000962

# Carbide Planets May Be Made Of Silica and Diamonds (Astronomy)

Extrasolar planets hosted by stars with sufficiently high carbon-to-oxygen ratios could be made of diamonds and silica, according to new research by Arizona State University and the University of Chicago.

When stars and planets are formed, they do so from the same cloud of gas, so their bulk compositions are similar.

A star with a lower carbon to oxygen ratio will have planets like Earth, comprised of silicates and oxides with a very small diamond content.

But exoplanets around stars with a higher carbon to oxygen ratio than our Sun are more likely to be carbon-rich.

Arizona State University researcher Dr. Harrison Allen-Sutter and colleagues hypothesized that these carbide exoplanets could convert to diamond and silicate, if water were present, creating a diamond-rich composition.

To test this hypothesis, the scientists needed to mimic the interior of carbide exoplanets using high heat and high pressure.

To do so, they used high pressure diamond-anvil cells in a lab.

First, they immersed silicon carbide in water and compressed the sample between diamonds to a very high pressure.

Then, to monitor the reaction between silicon carbide and water, they conducted laser heating, taking X-ray measurements while the laser heated the sample at high pressures.

As they predicted, with high heat and pressure, the silicon carbide reacted with water and turned into diamonds and silica.

Therefore, if water can be incorporated into carbide planets during their formation or through later delivery, they could be oxidized and have mineralogy dominated by silicates and diamond in their interiors.

The reaction could produce CH4 at shallower depths and H2 at greater depths that could be degassed from the interior, causing the atmospheres of the converted carbon planets to be rich in reducing gases. Excess water after the reaction can be stored in dense silica polymorphs in the interiors of the converted carbon planets.

Such conversion of mineralogy to diamond and silicates would decrease the density of carbon-rich planet, making the converted planets distinct from silicate planets in mass–radius relations for the 2–8 Earth mass range.

While Earth is geologically active, the team’s results show that carbide planets are too hard to be geologically active and this lack of geologic activity may make atmospheric composition uninhabitable.

References: Allen-Sutter et al. 2020. Oxidation of the Interiors of Carbide Exoplanets. Planet. Sci. J 1, 39; doi: 10.3847/PSJ/abaa3e

# An Hour In A Conference Room Produces Enough CO2 To Impair Your Brain (Biology)

Have you ever been in a meeting where you just can’t stay focused on anything that’s being said? You try like crazy to snap out of your daydreaming, but all you come back to is your boss jabbering on about who-knows-what, so you can’t help but let your mind wander again. As it turns out, you may not have yourself to blame for your short attention span.

See, according to a 2016 study from the international environmental design firm Gensler, after just one hour of meeting with others in a conference room, the level of carbon dioxide reaches 1,400 parts per million, or ppm. The human brain evolved in an atmosphere around 200 to 300 ppm of CO2, but nowadays, we’re regularly dealing with outdoor levels of 400 ppm or more. That’s bad for the environment, but it’s also bad for your brain.

As a 2015 Harvard study published in the journal Environmental Health Perspectives found, as CO2 concentrations rise, cognitive abilities fall. At a level of 945 ppm, brain functions decrease by 15 percent. At the 1,400 ppm level that the Gensler study found, the air becomes so polluted that cognitive performance can be stunted by as much as 50 percent.

What exactly did the study mean by “cognitive abilities”? They tested people over nine different domains and found that CO2 exposure at those levels can especially affect the areas of strategizing, focus, decisionmaking, and the capacity to understand new information. Or just about all of the reasons you’re in a meeting in the first place.

Oh, and here’s the kicker: That Gensler study measured the air quality when just three people were in the conference room.Three! So, you can expect the air to be even more polluted when more people are present in the room.

So what can be done about this nasty, brain-debilitating air quality? Luckily, the Gensler study found those results as part of a larger, three-year project studying air quality. That specific result was found when measuring a traditional conference room versus an identical one with an added “green wall.” A green wall is pretty much exactly what it sounds like; it’s a literal wall that is basically full of live greenery from floor to ceiling. In the green conference room, the CO2 level stayed below 1,200 ppm after two whole hours. That’s not a huge fix, but it’s not nothing.

But, assuming your company isn’t going to shell out the cash to convert your conference room into a Rainforest Café, would a few well-placed plants make a difference? Unfortunately, as this piece at The Atlantic explains, house plants do little to nothing to improve air quality. So you’re left with the traditional options: crack a window if it’s warm enough outside, use an electric fan if it’s not. If you don’t, you’ll be back to mindlessly nodding your way through those long company meetings and just hoping that you never get called on.

# Washing Your Hands With Cold Water Is Just As Effective (Biology)

If health PSAs have taught us anything, it’s that the only way to wash your hands is to make the water scalding hot, scrub, scrub, scrub with plenty of antibacterial soap, and sing “Twinkle Twinkle Little Star” to achieve the requisite 20 seconds of washing time. Well, science has spoken, and that means we have news for you: The water temperature doesn’t matter, and just 10 seconds will do the trick.

In May 2017, a Rutgers University study changed what we knew about washing your hands. Multiple times over a six-month period, the researchers put “high levels of a harmless bacteria” on the hands of 21 participants. Each time, they were asked to wash their hands in water at a temperature of 60 degrees, 79 degrees, or 100s degrees Fahrenheit (that’s 16, 26, and 38 degrees Celsius) using varying amounts of soap.

The results? The volunteers removed roughly the same amount of bacteria, regardless of water temperature. However, there was a marked difference in energy usage. Lead author Donald Schaffner says in a press release, “This study may have significant implications towards water energy since using cold water saves more energy than warm or hot water.” Schaffner also notes that “even washing for 10 seconds significantly removed bacteria from the hands.” You hear that? There’s no need to sing “Twinkle Twinkle Little Star” in public … unless you feel so inclined.

And what about those “varying amounts of soap” we mentioned? While researchers found no significant difference in bacteria reduction between regular and antimicrobial soap, they emphasize that there’s more research to be done. In the name of public health, scientists would love to pinpoint which soap to use and exactly how much to optimally remove harmful bacteria. Until then, just make sure you’re using soap and washing your hands for at least 10 seconds. As for water temperature, you do you! Schaffner insists that “people need to feel comfortable when they are washing their hands.”

# Drinking Hot Drinks Can Cool You Down (Biology)

There’s nothing quite like a long run on a sweltering summer day to make you thirst for a big ole’ mug of hot tea. Huh? Believe it or not, research has found that (under the right conditions) a hot drink after exercise can actually cool you down better than a cold one.

It sounds like something Snopes would shoot down. How could chugging some chai post-run possibly cool your body? There’s scientific evidence, we promise.

In a 2012 study, Dr. Ollie Jay from the University of Sydney examined the effectiveness of drinking both hot and cold drinks when it comes to lowering the amount of heat stored by your body. Volunteers were asked to ride bikes for 75 minutes at 75 degrees Fahrenheit (24 degrees Celsius) with 23 percent relative humidity — the equivalent of a nice summer day. Five minutes before the workout and every 15 minutes after, they drank water at one of four different temperatures: 34 degrees, 50 degrees, 98.6 degrees, or 122 degrees Fahrenheit (1.5 degrees, 10 degrees, 37 degrees, or 50 degrees Celsius).

The results? Those who drank the hottest drinks ended up cooling down the most. How is that possible? It has to do with your sweat and how it’s influenced by drink temperature. Sweat (or, more importantly — the evaporation of sweat) is key for helping your body come back to a temperature baseline. When you drink a hot drink, your body bumps up its sweat production, leading to more cooling. You might think that wouldn’t be enough to counteract the hot drink, but the sweat output actually outweighs any internal heating.

But here’s the slight catch — this study was performed under conditions where the volunteers’ sweat was able to evaporate completely. If you were to try the hot drink trick somewhere with poor airflow and/or high humidity, the results would likely be much different (i.e., cold drinks would probably win out). Would you ever reach for a post-workout hot chai?