# Space-Time Concepts, Gravity, Units, Models of the Universe, the Multiverse, ToE

**Concepts of Time:**

A defense of the reality of time

A look into the fourth dimension

Bell's theorm for temporal order

Timelapse of the entire universe

Carlo Rovelli on the physics of time

Physicists find signs of a time crystal

Keeping time with highly charged ions

Einstein says: It's 309.7-meter o'clock

Testing Einstein's E=mc2 in outer space

BoBar experiment confirms time asymmetry

FOAM: the importance of time synchronization

Inquiry into the nature of time with A. H. Almaas

Forget everything you think you know about time

The new thermodynamic understanding of clocks

A rock is a clock: physicist uses matter to tell time

Perfectly accurate clocks turn out to be impossible

In a 'rainbow' universe time may have no beginning

Light from galaxy clusters confirm theory of relativity

Physics explains why time passes faster as you age

Cosmic triangles open a window to the origin of time

The most accurate optical single-ion clock worldwide

The simple idea behind Eistein's greatest discoveries

Eva Silvastein: Other observations on history of science

Paradigm shift offers a new look at the beginning of time

Leap second: French time lords add one second to 2015

An inexpensive crystal makes a fine quantum time machine

Researchers explain why the Greenwich prime meridian moved

Superradiant laser may boost atomic clocks, create 'rulers' for sp

Scientists create time crystals, a rule-bending new form of matter

The discrete-time physics hiding inside our continuous-time world

The history of time and frequency from antiquity to the present day

1400km of optical fibre connect optical clocks in France and Germany

Quantum paradox experiment may lead to more accurate clocks and sensors

Does time really flow? New clues come freom a century-old approach to math

**Gravity:**

Testing theories of modified gravity

Why gravity is not like the other forces

The long path to understanding gravity

Emergent gravity and the dark universe

Maybe 'dark matter' doesn't exist after all

How gravity is a double copy of other forces

A molecular clock for testing fundamental forces

New math bridges holography and twistor theory

Gravity recovery and climate experiment (GRACE)

Attractive force arises from black-body radiation, says physicists

Strategy for the International Gravity Reference System and Frame IGRS/IGRF

Development of a displacement sensor to measure gravity of smallest source mass ever

A simple view of gravity does not fully explain the distribution of stars in crowded clusters

High-resolution data demonstrate gravitational lensing of the cosmic microwave background

**Quantum Gravity:**

Quantum gravity limits from planet observations

How holography could help solve quantum gravity

Researchers find quantum gravity has no symmetry

Physicists find a way to see the 'grin' of quantum gravity

One lab's quest to build space-time out of quantum particles

Understanding how quantum gravity affects low-energy physics

An ultra-precise clock shows how to link the quantum world with gravity

Understanding of complex networks could help unify gravity and quantum mechanics

**Physical Units , weights, measures and constants**:

Political union through science

The sounds of weights and measures

The future of the kilo: a weighty matter

Universal units reflect their Earthly origins

A more fundamental International System of Units

Galileo, krypton, and how the Metric Standard came to be

Largest overhaul of scientific units since 1875 wins approval

Important milestone reached on road to a redefined kilogram

An atomic physics perspective on the kilogram's new definition

New measurement of Universe's expansion rate is 'stuck in the middle'

Gravitational constant appears universally constant, pulsar study suggests

Kilogram to be based on physical absolute instead of single, physical object

**Space-Time:**

Space-time vortex around Earth

Simulating extreme space-times

Spacetime has no time dimension

Cosmography of the local Universe

The fall and rise of the Doppler Effect

What is the geometry of the Universe?

Spacetime: a smoother brew than we knew

New discovery about the fabric of space-time

How our Universe could emerge as a hologram

How spacetime is built by quantum entanglement

New mathrmatical model links space-time theories

Superfluid turbulence through the lens of black holes

Astronomers discover new way to measure Universe

Bringing time, space together for universal symmetry

Simulating four-dimensional physics in the laboratory

First signs of weird quantum property of empty space

Shape from sound - new methods to probe the Universe

Symmetries reveal clues about the holographic Universe

Scientists discover a jewel at the heart of quantum physics

Quantum computer as detector shows space is not squeezed

How space and time could be a quantum error-correcting code

Is nature continuous or discrete? How the atomist error was born

Is it possible to travel the span of the Universe at the speed of light?

International collaboration replicates amplification of cosmic magnetic fields

A robust constraint on cosmic textures from the cosmic microwave background

Maximum and minimum values, cosmology, a conjecture and Beckenstein bound

NASA's gravity probe spacecraft confirms Einstein's 'Warping of spacetime & frame-dragging'

**Dimension:**

The journey to define dimension

Lasers and ultracold atoms for a changing Earth

Structure in the fabric of space - the African Arrow

How many numbers exist? Infinity proof moves math closer to an answer

Strategy for the realisation of the International Height Reference System (IHRS)

Why our universe was born with 3 dimensions: a puzzle of superstring theory solved by supercomputer

**Time Crystals:**

Space-time crystals on the horizon

Space-time crystals of trapped ions

Time crystals realize new order of space-time

Eternal change for no energy: a time crystal finally made real

**Expansion of the Universe:**

What is the Universe expanding into?

Universe expanding faster than expected

Expansion of space measurement improved

Big bounce simulations challenge the Big Bang

Cosmologists debate how fast the Universe is expanding

Universe's expansion may not be the same in all directions

How (relatively) simple symmetries underlie our expanding universe

Could gravitational waves reveal how fast our universe is expanding?

The universe's rate of expansion is in dispute - and we may need new physics to solve it

**Worm-holes:**

Magnetic wormhole created for the first time

Travel through wormholes is possible, but slow

Newfound wormhole allows information to escape black holes

How to tell the shape of a wormhole by its quasinormal modes

'Spooky action' builds a wormhole between 'entangled' particles

Wormholes reveal a way to manipulate black hole information in the lab

**Energy:**

Boosting of force from empty space

Quantum vacuum: less than zero energy

**Entropy:**

How Maxwell's Demon continues to startle scientists

**String Theory:**

String Theory: a simple way to understand the universe

Some physicists see signs of cosmic strings from the Big Bang

**Alternative Models of the Universe:**

How order arises in the cosmos

Is the Universe a bubble? Let's check

Misconceptions about the Universe

Beyond the horizon of the Universe

How we escaped from the Big Bang

Universe is older than previously thought

Getting the math of the Universe to cancel out

Collapse of the Universe is closer than ever before

Planck mission explores the history of our Universe

Estimating cosmological parametters from the dark matter distribution

Paradoxes of cosmological physics in the beginning of the 21st Century

New findings bring physicists closer to understanding the formation of planets and stars

**Multi-verse:**

Could a multiverse be hospitable to life?

Physicists study how our Universes might bubble up and collide

Experimental limits on neutron disappearance into another braneworld

We are one of a vast Universe of new universes constantly being created

Scientists are searching for a mirror universe: it could besitting right in front of you

**Hologramic Universe:**

The Universe is really a hologram, according to new simulations

**Light and Matter**:

Dead star warps light of red star

Quest to test Einstein's speed limit

Special relativity induced by granular space

A better understanding of how the Sun bends light

Researchers shine a light on 150-year old mystery

Teaching general relativity to undergraduates

Precise test confirms speed of light is constant

Extending Einstein's theory beyond light speed

Speed of light: the history of a physical constant

A journey of light through space and time (video)

5-dimensional black hole could 'break' general relativity

Bizarre binary star system pushes study of relativity to new limits

Scientists discover how to turn light into matter after 80-year quest

Left-handed cosmic magnetic field could explain missing antimatter

Researchers develop way to control speed of light, send it backwards

First successful test of Einstein's General Relativity near supermassive black hole

Simulation shows that dark energy and matter can reproduce the Universe

Flashes from faster-than-light spots may help illuminate astronomical secrets

NIST pair of aluminum atomic clocks reveal Eistein's relativity at a personal scale

Transfer of atomic mass with a photon solves the momentum paradox of light

Newly discovered 3-star system to challenge Einstein's theory of General Relativity

Can strongly lensed Type 1a supernovae resolve one of cosmologies biggest controversies?

A heavy weight for Einstein: observations of the most massive neutron star confirms Eistein's theory

Detection of the cosmic gamma ray horizon measures all the light in the universe since the Big Bang

**Theory of Everything (ToE):**