Antimatter interacts with regular matter in more ways than just annihilation. Annihilation just happens to be a process that’s uniquely available to antiparticles and has a high probability of occurring. This is because antiparticles have both opposite electric charges to standard particles and opposite color charge, so annihilation between particle/anti particle pairs conserves these quantities.

It’s unlikely that there’s an anti-matter equivalent of dark matter. If there was, we’d expect to see annihilation radiation, such as the 511 keV photons emitted when positron+electron pairs annihilate.

Yep. In fact there’s a process called inverse Compton scattering that essentially works this way. In ordinary Compton scattering, a photon scatters off a stationary electron and typically leaves with less energy (since the electron gets a kinetic kick). In inverse Compton scattering, a photon collides with a moving electron which can cause the photon to gain energy.

One application of this is to produce gamma-ray beams. You take a beam of light (often from a laser) and collide it head on with a beam of relativistic electrons traveling in the opposite direction. In the electron rest frame, the photon has gamma-ray energy, while in the lab frame it might only be visible light. The back-scattered photon can then be boosted to the gamma regime in the lab frame, and now you’ve got a gamma-ray beam.

A black hole is believed to contain a singularity with all of the mass as a single point. So this is well past the point of baryonic matter and in a region where our physics models break down.

If you just take the total mass of a black hole and divide it by the volume of the Schwarzschild radius (aka event horizon) you get a density MUCH greater than a neutron star. This isn’t a useful measure of the black hole density though, since all of the mass is at a single point of presumably infinite density.

Neutron stars are the most compact form of matter that we know about; they’re even denser than the nucleus of an atom.

Neutrons, protons and electrons are fermions, meaning they must obey the Pauli exclusion principle. No two neutrons (or protons or electrons) can be in the same quantum mechanical state. If you take ordinary star matter (plasma made of dissociated protons and electrons) and squeeze it, eventually the electrons will nearly overlap in their states. You’d have two electrons with nearly the same energy, spin and location. They cannot overlap though, so this creates a repulsive force that prevents the matter from further compression; this is called the electron degeneracy pressure.

If the compressive force overcomes this pressure, then the electrons can capture on the protons to form neutrons. Neutrons and protons also have degeneracy pressures, but they can be packed much more densely than electrons. This is because their wavelength is shorter. The wavelength of a massive particle is inversely proportional to its mass, and protons and electrons are about 2000 times the mass of electrons. So compressed ordinary matter will inevitably become pure neutrons, simply because this is the most compact form.

A pure electron or pure proton star wouldn’t be as compact because both are charged particles so there would be Coulomb repulsion (this isn’t an issue in ordinary matter since the number of electrons and protons is roughly equal). You’d also need to somehow separate the electrons from the protons, and this isn’t a process that would naturally occur in a collapsing star.

They would die immediately.

Breaking atomic and molecular bonds is what ionizing radiation such as gamma rays or neutrons does to a human body, so this scenario would be sort of like an extreme, unrealistically high dose of radiation.

Immediately after all bonds are broken, atoms would react and start to form new bonds. In some cases these bonds would reform correctly- for example, water being remade as H2O. In many cases alternative bonds would form which could make substances incompatible with life- say H2O2, aka hydrogen peroxide. Basic cellular and nerve function wouldn’t work, hence the instant death.

Lepton number is an observationally conserved quantity. As far as I know there’s no fundamental reason for it to be conserved (and indeed there are searches for physics beyond the standard model that would violate it) but it’s been found to generally be conserved in reactions so far. Lepton particles have a lepton number of +1, lepton antiparticles have -1.

There’s a similar conserved quantity known as the baryon number, with a similar definition. Protons and neutrons (baryons) have values of +1, anti-protons and anti-neutrons are -1.

An example: consider the beta- decay of a neutron, baryon number +1 and lepton number 0. It emits a proton (baryon number +1), an electron (lepton +1), and an electron anti-neutrino (lepton -1). Total lepton number of the decay products is 1-1=0, so the value is conserved.

Locking because the discussion isn’t consistent with community rules.

While /c/askscience doesn’t have a rule against soliciting medical advice, I’d strongly recommend against trusting the comments from random internet strangers. Especially those without authoritative sources to back them up.

Unfortunately the only way to get a reliable answer to your question is to speak to a medical professional.

I’ll echo the other replies that the gravitational waves from black hole mergers have been detected by LIGO. In fact, the 2017 Nobel Prize in physics was awarded to members of this collaboration specifically for this feat.

We haven’t (yet) seen a pair of black holes collide using light directly, but the gravitational waves have been perfectly consistent with general relativity calculations. Here’s a video from LIGO that shows what one of these simulations looks like, for a simulation that reproduces a detected gravitational wave.

As an aside, right around the time the LIGO team was awarded the Nobel prize, they detected the collision of a pair of neutron stars. They alerted the astronomy community to the direction they saw the signal from, and within a day there were telescope observations of light from the kilonova that resulted from the collision. Ultimately various sensors recorded optical light, infrared, ultraviolet, gamma rays, and radio waves being emitted from the explosion. The hope is that someday we’ll get lucky enough to see similar photon signatures from a black hole merger!

For physics specifically, a bachelor’s degree probably won’t be enough to get a job in physics.

You might be able to get a job as a technician in a lab, but they typically will look for people with a master’s degree for those roles. With just a bachelor’s , you’d need to get your foot in the door by already having some relevant experience, which is a possibility if you get some research experience in college and pivot that into an internship or something. But it would definitely require effort and luck.

I’m not sure that’s a good comparison. The kill mechanism from a neutron bomb is the deposition of ionizing radiation in the body, but the microwave radiation is non-ionizing.

You’ve gotten some good answers explaining that heat changes the density, and therefore the index of refraction of air.

Fun fact: Schlieren Imaging allows one to photograph shockwaves by relying on the same effect. As a shockwave travels through air, it creates a region of high density, which can be imaged with this technique.

in the photon’s frame of reference

There are no valid inertial frames for an object moving at the speed of light. The idea that “a photon doesn’t experience time” is a common, but misleadingly incorrect statement, since we can’t define a reference frame for it. Sometimes this misconception can be useful for conveying some qualitative ideas (photons don’t decay), but often it leads to contradictions like your question about Hawking Radiation for black holes.

Yes, the wavelength of photons will be preserved if they travel through non-expanding space. If the photon is emitted by a source that’s in motion with respect to a detector, there could still be redshift or blueshift from the relativistic Doppler effect. This would only depend on the relative velocity between the emitter and observer, and not on the distance the photon traveled between them.

Unfortunately for me, there is no community at Lemmy dedicated to the history of science

I agree! The history of science is often even more interesting since you get both the science and the personalities of all the people involved, plus the occasional world war in the mix. It’s a shame there isn’t an “askhistorians” type community here.

how people very knowledgeable on the current paradigm cannot see (most of times historicaly) that a paradigm shift is about to happen ?

I’m not sure I’d agree with that assessment. Generally a new model or understanding of physics arises because of known shortcomings in the current model. Quantum physics is the classic example that resolved a number of open problems at the time: the ultraviolet catastrophe in black body radiation, the photoelectric effect, and the interference pattern of the double slit experiment, among others. In the years leading up to the development of quantum theory, it was clear to everyone active in physics that something was missing from the current understanding of Newtonian/classical physics. Obviously it wasn’t clear what the solution was until it came about, but it was obvious that a shift was coming.

The same thing happened again with electroweak unification%20and%20the%20weak%20interaction.) and the standard model of particle physics. There were known problems with the previous standard model Lagrangian, but it took a unique mathematical approach to resolve many of them.

Generally research focuses on things that are unknown or can’t be explained by our current understanding of physics. The review article you linked, for example, details open questions and contradictory observations/predictions in the state of the art.

Haha it’s in the title: “Cosmological Particle Production: A Review”. Also the journal it was published in is for review articles: Reports on Progress in Physics. Mostly though the abstract promises to give a review of the subject.

Another indication is its lengthy (28 pages) with tons of citations throughout. If someone is doing new work, citations will mostly be in the introduction and discussion sections.

So unfortunately the article they reference by Parker is paywalled. I have access but can’t share it easily. The article is essentially the foundation of quantum field theory in curved space time - in other words the genesis of the standard cosmological model. Cosmological particle production in an expanding universe isn’t an alternative to the Big Bang, it’s an essential part of it.

Leonard Parker’s work is summarized on his Wikipedia page. You can also read an interview with him on the arxiv

There isn’t a link in your post, but it looks like you’re referring to this preprint. The article has been published in a peer reviewed journal paywall warning.

This is a review article, so it isn’t proposing anything new and is instead giving a summary of the current state of the field. These sorts of articles are typically written by someone who is deeply familiar with the subject. They’re also super useful if you’re learning about a new area - think of them as a short, relatively up-to-date textbook.

I’m not sure how you’re interpreting this review as an alternative to the standard model of cosmology and the Big Bang. Everything is pretty standard quantum field theory. The only mention of the CMB is in regards to the possibility that gravitons in the early universe would leave detectable signatures (anisotropies and polarization). They aren’t proposing an alternative production mechanism for the CMB.

This falls a bit outside my wheelhouse but I believe the answer is no. The established symmetries in particle physics are all associated with the quantum mechanical state of a particle (charge, parity, etc) and to my knowledge there isn’t an “information” quantum number.

The closest you might get to this is quantum information theory, where information is encoded in other physical characteristics (spin, parity, energy, etc). In this sense information is more of an emergent phenomenon than a fundamental property.