hubble constant measurement

A sculptor shapes mountains from magnetic fields and heat, but the stone resists. A neutron star, the ultra-dense remnant of a supernova explosion, in a binary system pulls matter from its companion star. This infalling matter heats the star's crust unevenly, while the magnetic field tugs from within.

In the heart of an old city stands a clock tower whose hands have never been adjusted since it was built. By how far it runs slow, you can calculate how much time has stretched since then. In space, the role of such towers is played by relic galaxies — dense stellar systems that formed in the first few billion years and have since neither merged with neighbors nor given birth to new stars.

Six runners sprint down the track, and officials time their speed without noticing a tailwind. The wind blows at their backs, and the stopwatches show a better result than the truth. Roughly this is how six megamasers — natural cosmic lasers in distant galaxies — misled astronomers measuring the expansion rate of the universe.

Measuring distances in the universe is no easy task. Almost all methods rely on light, which can be absorbed by dust, scattered, or distorted along the way. It's like trying to spot a distant lighthouse through fog and haze. Neutrinos are a different story. These ghostly particles pass through anything without noticing obstacles.

The cosmic dawn is hidden behind a dense veil of time. To see beyond it, you need to catch the radio signal from clouds of neutral hydrogen — the so-called global 21 cm signal. But it is so faint that the receiver's own noise drowns it out.

Right after the Big Bang, space cooled unevenly. In some places, folds could have formed — threads of energy as thin as a hair but incredibly dense. Physicists call them cosmic strings. They oscillate, collide, and emit gravitational waves — ripples in the fabric of space itself.

Predicted by Albert Einstein, gravitational waves are like beacons in the dark ocean of space. They flare up when black holes collide, sending ripples through the fabric of the Universe.

The cosmological debate is like two craftsmen measuring the same wall but getting different lengths. One uses a tape measure, applying it to nearby landmarks — Cepheids (pulsating beacon stars) and Type Ia supernovae (flashes of dying stars). He finds the wall is stretching at 73.5 arbitrary units.

A drama is brewing in cosmology: two principal musical instruments, the orchestra of the early Universe and the chamber ensemble of the modern cosmos, play the same symphony of expansion at different tempos.

Half a century ago, Fritz Zwicky noticed that the visible matter in galaxy clusters was catastrophically insufficient to explain gravity.

Imagine a cosmic orchestra performing a symphony from the Big Bang to the present day. The conductor, dark energy, long seemed an impassive metronome: the cosmological constant Λ motionless, like a baton frozen in mid-air.

In a recent study, astrophysicists showed how pre-recombination physics, particularly early dark energy, affects the spectral running $$α_s$$ and, consequently, the viability of scenarios forming primordial black holes from an ultra-slow-roll (USR) phase during inflation.

The cosmological orchestra doesn't tune to a single tuning fork. There are two groups of instruments: one listens to the hum of the young universe — the cosmic microwave background, while the other reads notes from mature galaxies and supernovae.

The universe is a vast orchestra playing the score of expansion. Galaxies race apart to the beat of inaudible music of dark energy. But here's the trouble: the conductor's baton held by Edwin Hubble, Adam Riess, and Vera Rubin sets two incompatible tempos.

The Universe has a rate at which it expands — called the Hubble constant. The problem is that the two most precise ways to measure it give different numbers. One method, using the early light of the Universe (the cosmic microwave background), gives one value.

The Universe resembles a dense forest: up close, individual galaxy-trees are visible, gathered into groves, but from a distance everything merges into a solid green canopy. The boundary beyond which the cosmos becomes homogeneous is called the angular scale of homogeneity: it's the size of a patch of sky from which galaxies are distributed evenly.

Cosmology is the music of the spheres, and the Hubble constant once seemed like a reliable metronome.

Cosmology resembles a courtroom where two witnesses give irreconcilable testimonies. The first — the analysis of the cosmic microwave background by the Planck satellite — claims: the expansion of the universe proceeds at 67 (km/s)/Mpc.

It was Edwin Hubble who discovered that galaxies are rushing apart, and Georges Lemaître linked this to the expansion of space. Today, the ΛCDM model, relying on dark energy and dark matter, asserts that the Universe is flat as a perfectly stretched canvas.

Cosmology is experiencing a tectonic rift. Cepheid-calibrated supernovae, measured by Adam Riess’s team, point to a rate of about 73 km/s per megaparsec.

Two clocks tell different times. One sits on our desk, the other lies far in the past, in the glow left over from the Big Bang. The first, looking at nearby galaxies, ticks off the expansion rate of the universe — about 73 kilometers per second per megaparsec of distance. The second, peering into ancient light, gives a noticeably lower value — roughly 67.

The Universe is expanding, but at what speed? Astronomers have been arguing for decades about the precise value of the Hubble constant. Two classic methods give slightly different results. Now there's a third — using mysterious radio bursts.

The universe is expanding, and galaxies are flying apart like raisins in rising dough. The rate of this expansion, the Hubble constant, is a key number in cosmology.

The Higgs boson lives an unimaginably short life — less than a billionth of a second. It cannot be caught directly, so physicists look at what remains after its decay: jets of particles, muons, neutrinos. But some information is lost if you consider only the explicit decay traces rather than the whole event.

In the standard cosmological model ΛCDM, galaxies recede under the pressure of dark energy — an invisible spring. However, different methods of measuring the expansion rate give different numbers, as if the ruler's scale is off.

The universe is expanding, but at what rate is a question that has been troubling astronomers for decades. Two methods of measurement give different answers, and this discrepancy is called the Hubble tension. Some look at the early universe through the cosmic microwave background, others at nearby supernovae and Cepheid variables.

The visible edge of the universe is a holographic screen that, like a black hole, obeys laws discovered by Bekenstein and Hawking. Normally, information is preserved on it, but calculations show that if a few bits are lost, energy is released that accelerates expansion.

The merger of two neutron stars is like a strike on a gong: a ripple in space, a gravitational wave, spreads through the universe. Detectors on Earth catch this ripple and, from its strength, calculate the distance to the source.

Measuring the universe’s expansion is like timing a race when the track stretches. Neutron star mergers act as standard sirens: their gravitational waves ring out with a known “volume,” so fainter signals mean greater distance.

Each merger of black holes produces gravitational waves — ripples in the fabric of the universe — predicted by Einstein and first detected with key contributions from Kip Thorne.

Modern telescopes see distant galaxies flying apart faster and faster. The cause is called dark energy, but its nature has been a mystery. On top of that, calculations of the expansion rate in the early and late Universe don't match. The answer might lie in an event much like a falling pencil.

The universe is a pie baked from a single recipe, but the teaspoon and the kitchen scale stubbornly show different amounts of sugar. That’s how it is with the expansion of the universe: measurements from nearby stars (the spoon) give one number, while those from the ancient light of the Big Bang (the scale) give a completely different one.

The Universe is expanding, and every galaxy cluster takes part in a grand dance. The tempo of this dance is set by the Hubble constant, first measured by Edwin Hubble nearly a century ago. Pinpointing the number is tough because you need a ruler that spans billions of light-years.

The cosmological community has been living in a state of quiet civil war for several years. Two camps measure the expansion rate of the Universe and get different answers. Planck, peering at the cosmic microwave background, says 67.4 km/s/Mpc. SH0ES, climbing the distance ladder from Cepheids to supernovae, insists on 73.2.