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Category: physics – Page 94

How do we know how much dark matter there is in the Universe?

AD — Go to https://ground.news/drbecky to stay fully informed with the latest Space and Science news. Subscribe through my link to get 40% off the Vantage plan for unlimited access this month only. | I often get asked how do we know dark matter exists? Which is why I’ve made a video on all the observational evidence we have before (linked below)! But occasionally I’ll get asked how do we know how much dark matter there is, which is a really fun question. There’s many different ways we can calculate this, including the ratio between normal (baryonic) and dark matter, but in this video I just wanted to highlight three different ways astrophysicists calculate this.

Here’s my previous video on all the evidence we have for dark matter — • All the evidence we have for dark mat…
My previous video on whether dark matter could be made of black holes — • Is dark matter made of black holes?
My previous video on whether black holes contain dark matter — • Do black holes contain dark matter?
My previous video on why galaxies merge if the universe is expanding — • If the Universe is expanding, then wh…

Allen, Evrard \& Mantz (2011; review on galaxy clusters observations) — https://arxiv.org/pdf/1103.4829
Zwicky (1933; first virial theorem paper in German) — https://articles.adsabs.harvard.edu/p…
Zwicky (1937; virial theorem applied to the Coma cluster) — https://articles.adsabs.harvard.edu/p…
Alpher, Bethe, \& Gamow (1948; big bang nucleosynthesis; behind paywall) — https://journals.aps.org/pr/abstract/.…
Alpher \& Herman (1950; more BBN work; behind paywall) — https://journals.aps.org/rmp/abstract…
Planck collaboration (2015; cosmological parameter results for our best model of the Universe) — https://arxiv.org/pdf/1502.

00:00 Introduction.
02:04 Ground News AD
03:54 Method 1 — Galaxy Clusters and the virial theorem.
08:49 Method 2 — Big Bang Nucleosynthesis.
11:39 Method 3 — Cosmic Microwave Background.
14:35 Outro.
15:24 Bloopers.

Video filmed on a Sony ⍺7 IV

🎧 Royal Astronomical Society Podcast that I co-host: podfollow.com/supermassive.

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Can mirrors facing each other create infinite reflections?

A new article explores the physics behind the popular party trick of infinite mirrors, explaining why it may not actually create infinite reflections. While it may seem like a never-ending loop, the reality is that the reflections eventually become too faint to see. This phenomenon is a result of the way light behaves and can be explained by the laws of physics.

Two Astrophysicists Debate Free Will

Does free will exist? Neil deGrasse Tyson and Chuck Nice sit down with astrophysicist Charles Liu sit down to discuss the existence of free will and whether physics allows for choice in our lives.

We explore cause and effect: how does uncertainty and chaos in the universe factor into free will? How important is the illusion of free will to society? What does a society that acknowledges a lack of free will look like?

Check out our second channel, @StarTalkPlus.

Get the NEW StarTalk book, ‘To Infinity and Beyond: A Journey of Cosmic Discovery’ on Amazon: https://amzn.to/3PL0NFn.

Support us on Patreon: / startalkradio.

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Scientists Bring Star Matter Closer to Earth With Creation of 5 New Isotopes

An international research team at the Facility for Rare Isotope Beams (FRIB) at Michigan State University has successfully created five new isotopes, bringing the stars closer to Earth.

The isotopes — known as thulium-182, thulium-183, ytterbium-186, ytterbium-187, and lutetium-190 — were reported Feb. 15 in the journal Physical Review Letters.

These represent the first batch of new isotopes made at FRIB, a user facility for the U.S. Department of Energy Office of Science, or DOE-SC, supporting the mission of the DOE-SC Office of Nuclear Physics. The new isotopes show that FRIB is nearing the creation of nuclear specimens that currently only exist when ultradense celestial bodies known as neutron stars crash into each other.

Venus May Have Once Hosted Seas Like Earth, But Is Bone Dry Today

The find, simulated with computer modeling, might explain what happens to liquid water across the universe.

“Water is really important for life,” said Eryn Cangi, co-author and a research scientist at the Laboratory for Atmospheric and Space Physics, in a press release. “We need to understand the conditions that support liquid water in the universe, and that may have produced the very dry state of Venus today.”

At one point, Venus might have hosted seas like Earth. So, what happened? The study’s scientists suspect that Venus underwent a powerful greenhouse event that raised temperatures to 900 degrees Fahrenheit. After this happened, all the planet’s water evaporated, leaving some droplets behind. Even the few drops that were left over might have vanished because of an ion, HCO+, in the planet’s atmosphere.

Gravitational waves and the inflation of certainty

A team of scientists, astrophysicists and physicists, in an experiment called BICEP2 (Background Imaging of Cosmic Extragalactic Polarisation 2), carried out over nine years at an astronomical observatory at the South Pole, reported that they had discovered undeniable traces of a much sought-after phenomenon in astrophysics: gravitational waves. It was also announced that the method used to make the discovery had provided an important confirmation of the theoretical model of Big Bang cosmology, and would allow the first moments after this primordial explosion—the moment of creation for modern astrophysics—to be studied experimentally.

When you don’t find gravitational waves…

If we imagine space and time as the surface of an ocean, gravitational waves can be thought of as ripples in that ocean. More precisely, gravitational waves are theoretical ripples in space-time, first predicted by Albert Einstein in 1916 on the basis of his general theory of relativity. Like electromagnetic waves, which are produced by the oscillation of an electric charge, it is thought that a sufficiently strong oscillation of a very massive object should produce gravitational waves, which carry energy in the form of gravitational energy.

Venus Unveiled: The Mystery of Water Loss Revealed

“Water is really important for life,” said Dr. Eryn Cangi. “We need to understand the conditions that support liquid water in the universe, and that may have produced the very dry state of Venus today.”

How did the planet Venus lose its water? This debate has rage on for some time and something a recent study published in Nature hopes to address as a team of researchers from the University of Colorado Boulder (UCB) and the University of Arizona (UoA) as they have potentially conducted a groundbreaking study that could help explain the processes responsible for making Venus the hellish world it is today, whereas scientists have long hypothesized that the second planet from the Sun was much more hospitable billions of years ago.

“Water is really important for life,” said Dr. Eryn Cangi, who is a research scientist at the Laboratory for Atmospheric and Space Physics (LASP) at UCB and a co-author of the study. “We need to understand the conditions that support liquid water in the universe, and that may have produced the very dry state of Venus today.”

For the study, the researchers used a series of computer models to challenge previous studies regarding the mechanisms and speed that Venus lost its water. In the end, the team attributed Venus’ water loss to a process called “dissociative recombination”, which occurs when molecules are broken down and other molecules form as a result. While this process does not naturally occur on Earth and has been found difficult to replicate in the lab, it is a fundamental process in space physics and understanding how the rest of universe works.

Deep space collision 650 million light-years away sends gravitational-wave signal

Astronomers have picked up a gravitational-wave signal originating from a dramatic collision deep in the cosmos. The event, dubbed GW230529, was recorded by the LIGO Livingston detector in May 2023.

Gravitational waves are caused by the acceleration of massive objects, such as merging black holes or neutron stars. According to Albert Einstein’s theory of general relativity, massive objects like planets, stars, and black holes distort the fabric of spacetime around them.

When these massive objects accelerate or change speed, they create waves that propagate outward at the speed of light. The detection of gravitational waves opens up a new window for observing the universe, allowing scientists to study phenomena that were previously inaccessible, such as the mergers of black holes and neutron stars, as well as the nature of gravity itself.

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