andrew s

All scientific theories are subject to revision on the basis of new observations and JWST should provide many new insights just as the discovery of the CMB favoured the BB theory over the SS theory. In the meantime it is wise, in my opinion, to be clear what is the accepted best theory and which are more speculative or fringe. Regards Andrew

Well it was thought that was a possibility but the expansion is now dominated by dark energy that does not dilute as the Universe expands so the current view is it will go on expanding for ever. Regards Andrew

Since we have no evidence for any theory of everything I will pass on this debate. Regards Andrew

Yes it's a convention it has no physical meaning it could have been chosen differently. I was commenting on your big bang point. There was always gravity it did not need to wait for the Higgs mechanisms to switch on. Regards Andrew

Gravity does not just come from mass. In GR it comes from both the flow and density of energy (which includes mass). The almost perfect uniformity of the CMB shows it was very evenly spread out at the beginning. Regards Andrew

@Zermelo any place in physics you see "potential" it means a difference e.g. potential energy or potential difference in voltage. In which case the zero point is totally arbitrary and has no physical meaning. I suspect the sum of mass / energy in the Universe was done prior to the discovery of dark energy and dark matter. I am not sure where that leaves us. In reality I don't think we know if there is a net balance. In GR energy is not even conserved as you don't have time reversal symmetry. Indeed the current best cosmological model is not time reversible either. Regards Andrew

Ok so here is the results of a quick search. Gravitational potential energy is not just a property of the raised mass but one between it and what is creating the gravitational field. So to simplify, assume two masses M and m initially together and you do work from outside the system to separate them then the total mass of the system of masses M and m will have increased by the small amount equivalent to the work done. However, if M is the earth and it includes you and you throw a brick m upwards into orbit it won't have changed ! All you will have done is rearrange the internal energy of the system. Regards Andrew

Simple answer is I don't know. Clearly, moving the object changes the gravitational field so it might be stored in the gravitational field changes. I will do some research and get back to you unless someone answers before hand. Regards Andrew

No they are mutually equivalent ways of saying the same thing. The increase in chemical energy is the the mass increase. It's normally too small to bother about and only becomes significant with the strong nuclear force where it leads to nuclear power and weapons. Regards Andrew PS Try this

That's where you and nature disagree. In the standard model all "stuff" is just excitations in the various quantum fields. The more energy the more stuff. Regards Andrew

No the number of iron atoms remains the same. What does change is the energy stored in the " bonds" holding the spring together. Remember mass and energy are two faces of the same thing. Unfortunately, nature does not always fit our mental models of the world. Regards Andrew

To be honest I don't know if this is a good model or not. It seems plausible for something like Uranium 235 but for Helium it has a lower rest mass than its components but still has qluons holding it together. Regards Andrew

On reflection that is not correct it depends on if the bound entity has higher or lower energy than the components. If energy is given out when they form it will have less energy and lower rest rest mass and if it takes energy to form them then it will have more energy and higher rest mass than the components. In atomic nuclei lead is at the cross over point. Sorry for the mistake. Regards Andrew

I think this is a little confusing. The rest mass of a Uranium 235 atom is greater than the sum of the rest masses of its fission products. Binding energy of nuclei, atoms or molecules increases their rest masses. Regards Andrew PS see correction post below.

They are two ways of expressing the same thing the amount of stored energy. See the example above on a Uranium nucleus. In general relativity it is the total "stress energy tensor" that creates spacetime curvature. Regards Andrew

Ok take a nucleus of an atom of Uranium 235 it is bound by the strong nuclear force. It has potential energy as if you it in a nuclear reactor the fission products have less rest mass energy than the original atom. The excess goes into the kinetic energy of the fission products which is captured to eventually make electricity. It's the same with energy stored in chemical bonds or in separated charges as in a capacitor. Regards Andrew

The extra mass is in the battery' or more specifically in the chemical potential energy stored in its charged state. Regards Andrew

I have had several sx cameras and still have one guide camera. I have bought 2 new main cameras recently but found the sx range of CCD cameras could not compete in Quantum Efficiency, Read Noise or down load time compared to the latest CMOS cameras for the high cadence spectroscopy I was going to do. It's a pity but I hope they do manage to make the transition. The more options the better in my opinion . Regards Andrew

It's all to easy to get bogged down in negativity about the way our sense limit out inputs and our brains limit our insights. However, just look around you. While the ancient world achieved much the introduction of the scientific method (in which experiment is key) has revolutionised our understanding and ability to predict and transform the world. We have technology that rest on both classical and quantum physics and while gravity is not yet under our control we can detect its waves and use it to image galaxies that otherwise would be unreachable. My only fear is the attempt by some theorists to try to escape the harsh judgment of experimental tests. Regards Andrew

You might find this helpful. Regards Andrew PS see section 3 on the impact of moving the secondary on the optical correction of the system

One option would be to use a transfer lens to reimagine the focal plane out side of the body of the scope. Orion Optics do this with their ODK range. Regards Andrew

This is often stated in pop science but it is just a unit of measure. Test at the Planck scale don't show any effects. Here is an example using cosmic gamma rays. If space had become discrete at the Planck length then Lorentz invariance would not have held. It may not be continuous but if it isn't it will most likely be so well below the Planck scale. Regards Andrew PS This is a simple discussion on Planck length.

QM is a generalised probability theory. The simplest is the one where the "amplitudes " or probabilities sum to one. The next is where the sum of the squares of the "amplitudes " sum to one. This is QM. What Bell showed is that it can't be replicated by a local hidden variable theory with the first type of probability. An example would be a red and green sock each put in a box and separated. On opening one you box know instantly what the result of opening the other would be. You can't do this for QM systems. There are not hidden variables like sock colour. I am not arguing time evolution does not happen in a continuous way. All I am maintaining is that predictions of probability is not the same as being deterministic. Saying a coin will land 50/50 heads/tails is not being deterministic. Being correct 100% of the time in saying the next tossing will give a head and it does or tail and it does is. Regards Andrew

Which supports what I said it only predicts probabilities. To be deterministic it has to predict when it will decay. As mentioned previously not all quantum systems have a wave function and so Schrodingers equation can't be used you need a more general theory. The Pauli matrices for electron spin are an example. Schrodingers cat is a nonsense no macroscopic object can be in such a superposition the interaction with the air it needs to breathe will almost instantaneously decohere it to one state or the other. (Or failing that the CMB will do it just as quickly.) Schrodinger proposed it because it was a nonsense in his view. Regards Andrew PS all the interesting things in QM happen at the point of "measurement " when Schrodingers equation no longer applies. It is still a mystery - the measurement problem is one outstanding problem in the foundations of physics.

Off to play badminton and I predict I will lose most of my matches to much younger opponents. 😊 Regards Andrew