1

Physics, Astronomy & Cosmology / Re: How do galactic jets form?

« on: Yesterday at 22:41:28 »

Here is the link.
https://eps.leeds.ac.uk/maths-astrophysical-geophysical-fluid-dynamics/doc/relativistic-astrophysics

2

Physics, Astronomy & Cosmology / Re: Is time travel possible?

« on: 06/04/2021 06:44:32 »

The trouble with the idea of time travel to the past is, there is nothing to go back to. We invented time as a way of measuring change. You could argue that time dilation shows time is real. However, that is only a slowing down of physical processes. The slowing down of the change of states.

3

Physics, Astronomy & Cosmology / Re: Is time travel possible?

« on: 30/03/2021 22:54:06 »

Say you had a rival in business. You send an assassin back in time to kill your rivals grandfather. Now the rival is never born so you don't have the reason to send the assassin in the first place.

You have invented Schrödinger's grandfather. Alive and dead at the same time.

4

Physics, Astronomy & Cosmology / Re: How can conformal cyclic cosmology exist?

« on: 27/03/2021 10:10:36 »

Sir Roger Penrose says since mc^2 = hf clocks require mass, and his operation of squashing infinity requires it. Therefore his Conformal Cyclic Cosmology depends on it. Yet the very same mathematics says E = hf, so just energy also implies clocks. This undermines his theory.

There is a mass/energy equivalence. Also there are various types of energy. Rest energy, kinetic energy, potential energy etc etc. His theory involves the concept of the end of one universe initiating the next big bang. If the universe experiences heat death and all the black hole evaporate you have a situation where time has no meaning. Much like before the big bang. In this theory there is also no big crunch.

When you have heat death there is no more useful energy available to do work. So it is not possible to construct a clock. it doesn't matter which energy equation you cite.

5

General Science / Re: What is a black hole?

« on: 22/03/2021 10:58:54 »

One of the reasons that QM does not fit with general relativity is the information paradox. This involves the loss of quantum states. Many states can devolve into the same state. The wave equation should, in principle, be able to determine the state of a system at any point in time if the initial state is known. This is violated when things fall into the black hole. Information is no longer available to determine a systems state. This is information loss.

6

Physics, Astronomy & Cosmology / Re: Which stars by name or type emit polarised light?

« on: 21/03/2021 16:40:33 »

You mention dust in regard to this. Brian May's thesis, which has been published in book form is about dust. See https://spiral.imperial.ac.uk/handle/10044/1/1333

While this is not directly related to your post it is of interest generally.

7

Physics, Astronomy & Cosmology / Re: Does light have mass?

« on: 03/05/2020 12:04:35 »

Again, since the m here refers to proper mass, it doesn't apply to a photon.  Instead, the momentum for a photon is found by
p = hf/c
And the general equation ends up giving you E= hf for the photon.

I understand both equations (surprise!), but am not clear as to how p = hf/c becomes E= hf.

Energy is momentum times velocity. Here it is pc. Since hf/c times c cancels out the speed of light you are left with E = hf.

8

General Science / Re: When do YOU die in a many worlds interpretation?

« on: 08/12/2019 12:56:21 »

The problems begin when people try to add philosophy to quantum mechanics. They feel shocked that the results of experiments seem weird. They don't fit with their rational world view. That is not a shortcoming of quantum mechanics. It is a result of our limited perspective.

It isn't a problem that quantum mechanics is counter intuitive. It is the most interesting aspect of it.

9

General Science / Re: When do YOU die in a many worlds interpretation?

« on: 07/12/2019 12:38:15 »

You die. If you are buried then other lifeforms feed on you. They consume your energy for their own use. If you are cremated all your energy goes up a chimney. This continuous cycle continues until all species become extinct, the planet loses its atmosphere and water. Then the sun expands to consume the planet. Ultimately many worlds are consumed this way until the ultimate heat death of the universe. And they all lived happily ever after.

10

Physics, Astronomy & Cosmology / Re: Does information have mass?

« on: 08/11/2019 19:50:30 »

The sky is blue. That is information about the sky. Does it have mass? No, it is descriptive. The photons have energy, which has an equivalent relativistic mass. Define your interpretation of information.

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Physics, Astronomy & Cosmology / Re: What happens when both slits are observed by in the double slit experiment?

« on: 07/11/2019 21:40:57 »

Relativity is a classical and deterministic theory. Quantum mechanics introduces probability, which is not deterministic.

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Physics, Astronomy & Cosmology / Re: Does information have mass?

« on: 07/11/2019 21:20:31 »

Define your interpretation of information.

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Physics, Astronomy & Cosmology / Re: What happens when both slits are observed by in the double slit experiment?

« on: 06/11/2019 23:32:06 »

Also worth viewing

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Physics, Astronomy & Cosmology / Re: What happens when both slits are observed by in the double slit experiment?

« on: 06/11/2019 23:19:07 »

@Lloyd Quantum mechanics is just weird. That's the way it is. Probability is the key. It wasn't chosen to be that way by physicists. Look into polarised light and filters.
https://www.khanacademy.org/science/physics/light-waves/introduction-to-light-waves/v/polarization-of-light-linear-and-circular

This is where we eventually get to Bell's inequality. Go read up on it!

15

Physics, Astronomy & Cosmology / Re: What is the energy of a red-shifted photon?

« on: 04/08/2019 09:35:37 »

Where does the energy go, (approximately) inertial version. Say you are standing still and a bowler throws a cricket ball at you. It hurts! Now say you are riding a moped past the bowler and he throws the cricket ball at you. Since you are almost matching the speed of the ball it hurts a lot less. So where did the energy go? It was relative to the velocity of the victim and the bowler.

16

Physics, Astronomy & Cosmology / How well do laymen understand Bell's theorem?

« on: 03/08/2019 12:20:17 »

I just watched this video

. It may well help others to understand better. It is a difficult concept to grasp. Let me know if it helped.

17

Physics, Astronomy & Cosmology / Re: Does this equation mean anything?

« on: 18/07/2019 22:32:37 »

Has anyone done the dimensional analysis? 

18

Geology, Palaeontology & Archaeology / Re: SPAM.COM

« on: 18/07/2019 16:30:43 »

Well this user's particular machine is in Clifton, New Jersey. It may well be a compromised PC in a botnet.

19

New Theories / Re: Are all photons mediated in the same way through the quantum vacuum

« on: 16/07/2019 00:01:52 »

Now some food for thought. From here https://www.physicsforums.com/insights/misconceptions-virtual-particles/

"States involving virtual particles cannot be created since quantum field theory has creation operators only for observable particles whose 4-momentum satisfies the mass-shell constraint. For lack of a state, virtual particles have none of the usual physical characteristics of real particles: They cannot be said to exist in space and time, have no position, no meaningful probabilities to be created or destroyed anywhere, no life-time, cannot cause anything, interact with anything or affect anything. Therefore there is also no dynamics, speed of motion, or world lines. (In physics, dynamics is always tied to states and an equation of motion. Neither exists for virtual particles.)"

That sums it up in a nutshell, or off-shell if you prefer. If you wish to argue otherwise feel free to but in new theories.

20

The Environment / Re: How much effect does water vapour have as a proportion of global warming ?

« on: 08/07/2019 23:09:35 »

Maybe it's the fact that once again, the democtatic system fails by popular consensus overriding the the sane conclusion, majority decision on the side of the wrong tangent.

You appear to be arguing just for the sake of it. Taking up an opposite position to prolong a confrontation. I don't see what benefit you are getting from it