Quantum Gravity’s Time Problem

The effort to unify quantum mechanics and general relativity means reconciling totally different notions of time.

Theoretical physicists striving to unify quantum mechanics and general relativity into an all-encompassing theory of quantum gravity face what’s called the “problem of time.”

In quantum mechanics, time is universal and absolute; its steady ticks dictate the evolving entanglements between particles. But in general relativity (Albert Einstein’s theory of gravity), time is relative and dynamical, a dimension that’s inextricably interwoven with directions x, y and z into a four-dimensional “space-time” fabric. The fabric warps under the weight of matter, causing nearby stuff to fall toward it (this is gravity), and slowing the passage of time relative to clocks far away. Or hop in a rocket and use fuel rather than gravity to accelerate through space, and time dilates; you age less than someone who stayed at home.

Unifying quantum mechanics and general relativity requires reconciling their absolute and relative notions of time. Recently, a promising burst of research on quantum gravity has provided an outline of what the reconciliation might look like — as well as insights on the true nature of time.

As described in an article this earlier week on a new theoretical attempt to explain away dark matter, many leading physicists now consider space-time and gravity to be “emergent” phenomena: Bendy, curvy space-time and the matter within it are a hologram that arises out of a network of entangled qubits (quantum bits of information), much as the three-dimensional environment of a computer game is encoded in the classical bits on a silicon chip. “I think we now understand that space-time really is just a geometrical representation of the entanglement structure of these underlying quantum systems,” said Mark Van Raamsdonk, a theoretical physicist at the University of British Columbia.

In a new paper, Erik Verlinde of the University of Amsterdam argues that dark matter is an illusion caused by the holographic emergence of space-time from quantum entanglement.

Researchers have worked out the math showing how the hologram arises in toy universes that possess a fisheye space-time geometry known as “anti-de Sitter” (AdS) space. In these warped worlds, spatial increments get shorter and shorter as you move out from the center. Eventually, the spatial dimension extending from the center shrinks to nothing, hitting a boundary. The existence of this boundary — which has one fewer spatial dimension than the interior space-time, or “bulk” — aids calculations by providing a rigid stage on which to model the entangled qubits that project the hologram within. “Inside the bulk, time starts bending and curving with the space in dramatic ways,” said Brian Swingle of Harvard and Brandeis universities. “We have an understanding of how to describe that in terms of the ‘sludge’ on the boundary,” he added, referring to the entangled qubits.

The states of the qubits evolve according to universal time as if executing steps in a computer code, giving rise to warped, relativistic time in the bulk of the AdS space. The only thing is, that’s not quite how it works in our universe.

Here, the space-time fabric has a “de Sitter” geometry, stretching as you look into the distance. The fabric stretches until the universe hits a very different sort of boundary from the one in AdS space: the end of time. At that point, in an event known as “heat death,” space-time will have stretched so much that everything in it will become causally disconnected from everything else, such that no signals can ever again travel between them. The familiar notion of time breaks down. From then on, nothing happens.

On the timeless boundary of our space-time bubble, the entanglements linking together qubits (and encoding the universe’s dynamical interior) would presumably remain intact, since these quantum correlations do not require that signals be sent back and forth. But the state of the qubits must be static and timeless. This line of reasoning suggests that somehow, just as the qubits on the boundary of AdS space give rise to an interior with one extra spatial dimension, qubits on the timeless boundary of de Sitter space must give rise to a universe with time — dynamical time, in particular. Researchers haven’t yet figured out how to do these calculations. “In de Sitter space,” Swingle said, “we don’t have a good idea for how to understand the emergence of time.”

One clue comes from theoretical insights arrived at by Don Page and William Wootters in the 1980s. Page, now at the University of Alberta, and Wootters, now at Williams, discovered that an entangled system that is globally static can contain a subsystem that appears to evolve from the point of view of an observer within it. Called a “history state,” the system consists of a subsystem entangled with what you might call a clock. The state of the subsystem differs depending on whether the clock is in a state where its hour hand points to one, two, three and so on. “But the whole state of system-plus-clock doesn’t change in time,” Swingle explained. “There is no time. It’s just the state — it doesn’t ever change.” In other words, time doesn’t exist globally, but an effective notion of time emerges for the subsystem.

A team of Italian researchers experimentally demonstrated this phenomenon in 2013. In summarizing their work, the group wrote: “We show how a static, entangled state of two photons can be seen as evolving by an observer that uses one of the two photons as a clock to gauge the time-evolution of the other photon. However, an external observer can show that the global entangled state does not evolve.”

Other theoretical work has led to similar conclusions. Geometric patterns, such as the amplituhedron, that describe the outcomes of particle interactions also suggest that reality emerges from something timeless and purely mathematical. It’s still unclear, however, just how the amplituhedron and holography relate to each other.

The bottom line, in Swingle’s words, is that “somehow, you can emerge time from timeless degrees of freedom using entanglement.”

Time will tell.


anonymous asked:

Hi. What is white feminism? And why do I always hear it with a bad connotation? Is it contradictory to be white and a feminist? It just makes me so angry because I'm both?

white feminism is a fake, or very surface level concept of feminism that does not take into account the struggles of other marginalized groups and treats all women as completely synonymous and assumes they all have exactly the same experiences.

feminism is an all encompassing movement, because women are an all-encompassing group. if your feminism isn’t intersectional, then it’s not feminism at all. white feminism is just a term for sectionalist feminism, which, in this case, comes in the form of white women being racist and refusing to acknowledge their white privilege, and speaking over/erasing the issues of women of color.

it doesn’t mean that white women aren’t oppressed or that they can’t be feminists. it just means that if you’re racist you’re not a feminist at all.

There is no one way to be a goth. There is no “correct” way to be a goth. 

Do you like spooky things? Do you have an appreciation for the strange and unusual? Do you look for beauty in dark and unexpected places? Do you like the fashion, the music, the literature, the art? Congratulations, any one of those things means you have goth tendencies, and you can call yourself a goth.

You do not have to be thin.

You do not have to be pale.

You do not have to be over or under a certain age.

You do not have to have a specific hair color, own a certain pair of boots, like a particular band, or have read That One Book.

You are a goth if you say you are.

The only thing you MUST be (IMHO) is accepting of others. Do not be an elitist gatekeeper. And try to be kind.

Goth is as goth does. Don’t ever worry that you aren’t meeting some imaginary checklist. Just be yourself.

Reasons to love Jackson Wang
  • befriended a donkey like could your fave even
  • got rly sad when he couldn’t buy said donkey
  • loves animals SO MUCH
  • name should be Bluffy the Vampire Slayer tbh
  • shows off so much but is never serious about it
  • is hardly ever shy so when he gets shy IT’S ADORABLE????
  • wants to be best friends with everyone i mean everyone
  • his feelings get easily hurt bless
  • thinks he’s close w/ everyone and gets hurt when they say otherwise ACTUAL PUPPY
  • big gay chicken
  • talks about how hairy he is all the time jackson pls
  • sweaty so much sweat i feel u bro
  • if something even looks spicy he’ll start to sweat i feel u bro
  • thinks he’s hilarious and to be fair 9 out of 10 times he is like someone is literally always laughing around him
  • the rest of the time he’s just embarrassing
  • v affectionate and v aggressive with his affections
  • gets attached to ppl so easily like his capacity for love is BOUNDLESS
  • knows 5 different languages and probably more wtf even is he
  • says he’s into hip hop and stuff but he is way too nerdy to actually pull it off
  • thighs thicker than the bible
  • shameless
  • has 0 shame
  • if shame were clothes he’d rip them off and strike a pose

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The folklore among knitters is that everything handmade should have at least one mistake so an evil sprit will not become trapped in the maze of perfect stitches. A missed increase or decrease, a crooked seam, a place where the tension is uneven - the mistake is a crack left open to let in the light. The evil sprit I want to usher out of my knitting and my life is at once a spirit of laziness and of over-achieving. It’s that little voice in my head that says, I won’t even try this because it doesn’t come naturally to me and I won’t be very good at it.

Kyoko Mori, ‘Yarn’

That last phrase especially - “I won’t even try this because it doesn’t come naturally to me and I won’t be very good at it.” It really is like some kind of all-encompassing evil sprit sometimes. 


Diapsida: The Cladogram

Version 1.11 · 20 March 2016

Attention: This post will be updated should someone here correct a mistake I made. Please consider reblogging from the original post to get the latest update.

After one exhausting week and tons of feedback from paleonerds and graphic designers, the cladograms are finally here! These cladograms explain the relationships between notable genera within the group Diapsida which encompasses all modern reptiles including birds.

The PDF version is downloadable by donation here, and merchandises such as posters and stickers are now available from my store.

- - -

Will Art for Science · Shop · Patreon

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once more with feeling:

there are no latinx names. there are no latinx features. there is no “latinx” race.

latinx is an ethnicity that encompasses all the people whose familiar history is tied to the pre and post colonial and/or diasporic experience of latin america. 

latinx includes indigenous latin americans who have different features, stories, cultures and languages. there are hundreds of different indigenous people across latin america.

latinx includes afro latin americans whose ancestors were brought to latin america by slavers, as well as africans who emigrated to latin america later.

latinx includes europeans who’ve been here since colonial times and europeans who emigrated later, both white and non-white. for example, spanish, italian and portuguese people of arab heritage, jewish people, rromani people; all are non-white europeans. not all europeans who immigrated to latin america were/are white.


latinx includes people of all races. just as an example, in the past half-century, south america has become the largest south-east-asian diaspora in all of the western world. there are plenty of second or third generation asians living in latin america who are as latinx as spaniards who emigrated during wwii or italians who came escaping fascism. 

latinx names can be hispanic, asian, indigenous or anglosaxon names. latinx features can be the features of any race. latinx culture is the intersection of every person’s individual culture with their country’s culture, and the many cultural variations that have been and are created by diasporic latinxs living outside of latin america.

we have a shared history, we have shared traits and a couple languages that are more or less spoken across most of our communities, there are certain cultural factors that most latinxs share. but that doesn’t mean all latinxs look, behave, speak or are named in similar ways.

so, repeat with me:

latinx is not an homogenous identity. 

latinx is not a race. 

latinx is an ethnicity.


“Blue was perfectly aware that it was possible to have a friendship that wasn’t all-encompassing, that wasn’t blinding, deafening, maddening, quickening. It was just that now that she’d had this kind, she didn’t want the other.”

Maggie Stiefvater

Maggie Stiefvater orders a drink composed of long-forgotten ingredients found in the darkest reaches of the Starbucks store room, perhaps left there long ago by Stiefvater herself. The barista asks for her name to write on the cup. “Maggie,” says the author. “Just Maggie?” asks the barista. “That’s all there is,” says Stiefvater.

After the author leaves, the barista makes herself another one of the drinks and downs the whole thing. It seems made of impossible dreams. The barista is perfectly aware that it is possible to have a coffee that isn’t all-encompassing, that isn’t blinding, deafening, maddening, quickening. It’s just that now that she’s had this kind, she doesn’t want the other.

Off on another film expedition today to test our our new Leica bodies and lenses, along with putting our Sony, Nikon and @gopro to work.
It’s enticing to be such a big part of a growing community in film, @indiefilmlab and I are in close relation working on several things all at once to encompass the idea: process is better.
We are heading out to Tahkenitch instead of Crater and are excited as ever to explore new places. Oregon’s built for that.
So, we’re ready. Film in hand, cameras to test and play with, camping gear at the ready and coffee in hand.
Thanks to everyone who supports the @1924us crew. Thanks for making our efforts at preserving history a good one.

If you had to describe your best friend(s) in one word, what would it be. Tag them and let them know!
@burtoo - sociopathic
@paintinginpurgatory - apathetic
HAHHAA I love you guys, let’s go on this adventure already.
#travel #1924us #ventureonward #go #explore #oldmen #laughing #coffee #adventure #film #leica #cameras #gopro #leather #boots #expedition #mountains #home #oregon by 1924us


fave music angels ♡ brendon urie (panic! at the disco)

“In the last five years I’ve felt less resentful about where I came from, my roots in religion, in spirituality. I wanted to touch on that and make it a point to recognize our fans and just how much of my work, my job, is my religion. Touring is my religion. Music is all-encompassing—my religion. So, I wanted to celebrate that.”

The Houses: An Extended Guide

I’ve been getting lots of questions about what houses are and how they contribute to an astrological chart. I admit, houses were the hardest thing in astrology for me to initially understand. So here is my guide on the houses for you. If you have any specific questions, let me know!

What is a house?

Astronomically, the positions of the houses in a natal chart are calculated using the person’s time of birth and geographical birth location. While the zodiac signs and the planets in the zodiac signs are based on the earth and the other planet’s revolution around the sun, the houses and the planets in the houses are based on the earth’s own rotation about its axis.

Astrologically, each house represents a different function of your life, and all the houses together encompass all the parts of a human’s full life.

What do the houses represent?

Here are the life functions each of the houses represent:

  • House I: Identity, expression
  • House II: Possessions, money
  • House III: Communication
  • House IV: Family, your roots and home
  • House V: Creativity, children, sex
  • House VI: Service, health
  • House VII: Relationships, marriage
  • House VIII: Death, transformation
  • House IX: Travel, philosophy
  • House X: Career, reputation
  • House XI: Friends, dreams
  • House XII: Secrets, self-undoing

So what does this mean for my chart?

Every planet in your chart is in a house the same way it is in a sign. There are two wheels in your chart as depicted below. There is the zodiac wheel which contain the signs (traced in purple) and the wheel of houses which contain the houses (traced in black). Houses can be uneven in size.

For example: look at the chart above, and find the moon symbol towards the top of the chart. It’s in the black division designated for the 9th house (you can see the tiny number 9 towards the center of the circle) and the purple division designated for Gemini (you can see the yellow glyph for Gemini at the edge of the chart above the moon).

The sign (Aries…Pisces) a planet is in shows HOW the planet is manifest in the person’s personality. The house (I…XII) a planet is in shows WHERE in the person’s life the planet’s energy is displayed. To read what the different positions for your planets mean, look at this site and find the position you’d like to learn more about.

How do I find the positions of my houses and what houses my planets are in?

To pull up a chart similar to the one above, go to Hover over “Free Horoscopes”, and select “Natal Chart, Ascendant.” You can enter in your birth  information and pull up your chart.

Also, to easily find what sign each of your houses start in (i.e. the cusp of each house) go to cafeastrology’s chart generator here. You can pull a table similar to the below.

Under “Placidus Orb: 0″ is a listing of which sign each house begins in. For example, in the table above, the 3rd House (House III) starts 22º in Scorpio. Note that “ascendant” is the same as your rising, which is the same as the sign in which your 1st House starts, and your “midheaven” is the same as the sign in which your 10th House starts. 

What if I have empty houses? Did I do something wrong?

You did nothing wrong! Everybody has a few empty houses since there are 10 planets and 12 houses, and they are not necessarily bad. They simply mean that the part of your life that empty house rules won’t be too consciously prominent in your life. Of course an empty 7th house won’t mean you won’t get married and an empty 5th house won’t mean you won’t have children. It simply means your relationships or children won’t be a consciously prominent part of your life.

What are stelliums?

A stellium is when you have 4 or more planets or luminaries (i.e. Mercury…Pluto or sun or moon; nodes, asteroids, and points like Vertex or rising or midheaven aren’t counted) in one house or one sign. It is also debated that a stellium could also consist of 3 personal planets or luminaries (sun, moon, Mercury, Venus, Mars) as well. The sign or house in which the stellium is present will be very prominent in your life.

What are the different kinds of houses?

The twelve houses are divided into three groups: the angular houses (1st house, 4th house, 7th house, 10th house), the succedent houses (2nd house, 5th house, 8th house, 11th house), and the cadent houses (3rd house, 6th house, 9th house, 12th house). The three groups of houses are similar to the qualities or modalities of the zodiac signs. The angular houses (which are accepted as the most important) are similar in quality to the cardinal signs, the succedent houses are similar in quality to the fixed signs, and the cadent houses are similar in quality to the mutable signs.

The twelve houses are also divided into four other separate groups: the houses of life (1st house, 5th house, 9th house), the houses of wealth (2nd house, 6th house, 10th house), the houses of relationships (3rd house, 7th house, 11th house), and the houses of endings (4th house, 8th house, 12th house). These classifications are similar to the elements for the signs. The houses of life correspond with fire, the houses of wealth correspond with earth, the houses of relationships correspond with air, and the houses of endings correspond with water.