What is the deepest level of reality? In this Quanta explainer, Vijay Balasubramanian, a physicist at the University of Pennsylvania, takes us on a journey through space-time to investigate what it’s made of, why it’s failing us, and where physics can go next.

Explore black holes, holograms, “alien algebra,” and more space-time geometry: https://www.quantamagazine.org/the-un…

00:00 — The Planck length, an intro to space-time.
1:23 — Descartes and Newton investigate space and time.
2:04 — Einstein’s special relativity.
2:32 — The geometry of space-time and the manifold.
3:16 — Einstein’s general relativity: space-time in four dimensions.
3:35 — The mathematical curvature of space-time.
4:57 — Einstein’s field equation.
6:04 — Singularities: where general relativity fails.
6:50 — Quantum mechanics (amplitudes, entanglement, Schrödinger equation)
8:32 — The problem of quantum gravity.
9:38 — Applying quantum mechanics to our manifold.
10:36 — Why particle accelerators can’t test quantum gravity.
11:28 — Is there something deeper than space-time?
11:45 — Hawking and Bekenstein discover black holes have entropy.
13:54 — The holographic principle.
14:49 — AdS/CFT duality.
16:06 — Space-time may emerge from entanglement.
17:44 — The path to quantum gravity.

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In today’s world, the fight against counterfeiting is more critical than ever. Counterfeiting affects about 3% of global trade, posing significant risks to the economy and public safety. From fake pharmaceuticals to counterfeit currency, the need for secure and reliable authentication methods is paramount. Authentication labels are commonly used—such as holograms on bank notes and passports—but there is always a need for new unfalsifiable technologies.

This is where research recently published in Applied Sciences comes into play. Led by a team of scientists from Oxford University, the University of Southampton, and Diamond Light Source, the UK’s national synchrotron, the work focuses on developing a new technology for writing and reading covert information on authentication labels.

This technology leverages the unique properties of Ge₂Sb₂Te₅ thin films, which can change their structure when exposed to specific types of laser light. By using circularly or linearly polarized laser light, the researchers can encode hidden information in these thin films. This information can then be revealed using a simple reading device, making the technology both advanced and accessible.

Thus, when one looks back in time, say by looking at light from a distant galaxy that has traveled billions of years to reach us, this is akin to “zooming out” on the hologram and making its details fuzzier in the process. This zooming out can continue until all the details of the hologram disappear altogether, which in the model of the universe suggested by Hawking and Hertog, would be the origin of time at the Big Bang.

“The crux of our hypothesis is that when you go back in time, to this earliest, violent, unimaginably complicated phase of the universe, in that phase you find a deeper level of evolution, a level in which even the laws of physics co-evolve with the universe that is taking shape,” Hertog said. “And the consequence is that if you push everything even further backward, into the Big Bang, so to speak, even the laws of physics disappear.”

A pioneering technique shows how sound can be used to create entire objects quickly and at once. Researchers at Concordia have developed a novel method of 3D printing that uses acoustic holograms. And they say it’s quicker than existing methods and capable of making more complex objects.

The process, called holographic direct sound printing (HDSP), is described in a recent article in the journal Nature Communications. It builds on a method introduced in 2022 that described how sonochemical reactions in microscopic cavitations regions — tiny bubbles — create extremely high temperatures and pressure for trillionths of a second to harden resin into complex patterns.

Now, by embedding the technique in acoustic holograms that contain cross-sectional images of a particular design, polymerization occurs much more quickly. It can create objects simultaneously rather than voxel-by-voxel.

A 1930s-era breakthrough is helping physicists understand how quantum threads could weave together into a holographic space-time fabric.

Researchers at Concordia have developed a novel method of 3D printing that uses acoustic holograms. And they say it’s quicker than existing methods and capable of making more complex objects.

Following the accelerated expansion discovery of the Universe, scientists introduced dark energy concepts, which faced issues like the cosmological constant problem.

Researchers at IKBFU developed a holographic dark energy model based on quantum gravity, which views the Universe as a hologram. This model, initially unstable, was refined to treat dark energy as perturbations, stabilizing it. It is now being tested against observational data for accuracy.

Discovery of Accelerated Universe Expansion.

Back in August 2021, LA-based Portl launched a 7-ft-tall hologram projection box for life-like remote communications. Now renamed Proto, the company has revealed that its Epic technology is allowing cancer patients to consult life-size virtual specialists.

Proto was founded in 2018 by David Nussbaum, who took his experience working on huge holograms for arena gigs, movie premieres and fashion shows to produce a hologram in a box called the Epic. The idea is to plonk the machine in a venue, university, boardroom, medical facility and so on, and allow folks to chat with a life-like 3D hologram of a person who might be thousands of miles away.

So instead of a tiny image on a smartphone screen, the viewer essentially gets to interact with someone as if they’re actually in the room for a more natural communications experience. LED lighting inside the box helps with shadows and reflections for added realism, the front of the unit is touch-enabled, microphones and speakers are cooked in, and there are AI-powered cameras onboard too.

Researchers have developed a new smartphone-based digital holographic microscope that enables precision 3D measurements. The highly portable and inexpensive microscope could help bring 3D measurement capabilities to a broader range of applications, including educational uses and point-of-care diagnostics in resource-limited settings.

Entangled particles of light can transmit holographic images that can be selectively erased, allowing for secure communications that can also be deleted.

By Karmela Padavic-Callaghan