swansont

You wrote what was in your post. I quoted it and I moved it; I did not edit it. You were notified because it was a hijack of the discussion.

This makes sense to you. The absence of light - literally no photons - is a physical object. The dirt in a hole is a physical object, and not having that dirt is also a physical object. Defining everything as a physical object makes it simple, I guess. Gravity is an interaction, not an object. Same with magnetism.

That’s circular reasoning. it’s physical because I can measure it, and I can measure it because it’s physical. I can measure a shadow or a hole. Are these physical objects? It’s a simple, independent criterion. Because concepts are not physical objects.

Yes, I can give you a photon. Just one would be difficult for technical reasons, not philosophical ones. Length and time can be measured. Neither is a physical object.

Can you hand me a volume of space? Geometry is not a physical thing, and when we say spacetime has a geometry, it’s saying there’s a particular coordinate system that is best suited to describe it. e.g. the shortest distance between two points is a straight line or a specific curve.

It doesn’t, if the scale works by measuring the normal force.

Unless you define that to be up. It’s a label and it’s arbitrary. (with the caveat that one needs to label in a consistent fashion)

But these are not physical things unto themselves.

I’m giving a scenario which maximizes the CoM motion, to show how your explanation can’t be correct. The momentum is taken up by the earth, not the scale (to first order). The scale does compress, and more than if you were just standing on it - that part is correct. But if it compresses more, the reading has to go up.

So if you’re 60 kg, and the scale is 1 kg, you’re saying the scale mechanism is moving 60x faster than you are. Does that seem reasonable? You bend your knees and then we start the exercise: you straighten up, moving ~1m, in 2 seconds. How can the scale compress at 30 m/s for 2 seconds?

There is no F=ma exception for flesh or bone

! Moderator Note This not your thread. Split from https://www.scienceforums.net/topic/120896-a-mass-can-be-be-lifted-with-force-less-than-its-weight/

But does math exist?

Concepts don’t exist?

Then you can put it anywhere you like, but I think it needs to be rigid If it’s glass there’s no compression. The glass provides the force on the water. But you can observe what 20m of water would do to visibility, since we have situations like this. Things would be very blue https://www.researchgate.net/figure/Penetration-of-Light-of-Various-Wavelengths-through-Water-Blue-Light-is-the-Strongest_fig3_220785640 http://oceanography-leahmoore.blogspot.com/2010/10/light-attenuation-for-various-colors-of.html

That amount of water, as vapor, is my take. I'm going to answer a slightly different question, to start (there are so many ways the scenario is just impossible). Let's assume we have 1 square cm of surface. 10 meters of water is 1000 cm, so we have 1000 cm^3, or 1 liter (mass of 1 kg). We're going to vaporize this by raising the temperature and then boiling it. To heat it up to boiling requires 4184 J/kg per ºC. If we start at 20ºC, that's 3.35 x 10^5 J. That's the easy part. To vaporize this water requires 2260 kJ of energy (2260 kJ/kg) (i.e. 2.26 MJ) Result: ~2.6 MJ. For every square centimeter of surface. And double that, because you wanted ~20m. More than 5 MJ/cm^2 That energy must be released when you go back to a liquid. This has an effect on temperature, to be sure. 2 bars of water is going to make for pretty difficult breathing. You've now tripled atmospheric pressure, assuming you can get this much vapor in the air (I don't think you can) and what you're breathing is mostly water vapor. Oxygen has dropped from ~20% to less than 7%

! Moderator Note Yes. Posting this evidence is required for further discussion. Otherwise, the response is “good for you” and thread closure, because we’re a science discussion site.

less divergence.

Blessed are the cheesemakers (really, any makers of dairy products)

All of these can probably be looked at with an historical lens. Humans from 5k years ago and isolated from other populations show, at most, minor physical differences. They were around different animal species, and so different diseases, so they would likely be susceptible to each others’ diseases. Just like “old world” and “new world” populations. Language would also have diverged.

Thank you. Never noticed that (each time we update the software, I am less interested in poking around to explore all the features). Looks like blocking followers is all or nothing.

All lasers eventually diverge; most can be described by gaussian profiles, so they have a minimum spot size (“waist”) at some distance from the laser. Making the beam fat actually improves the divergence issues. The laser used for the moon ranging measurement diverged to be ~2 km across by the time it got to the moon (the atmosphere’s changing density played a part in this); the beam started out several meters wide https://tmurphy.physics.ucsd.edu/apollo/basics.html We use the telescope as a gigantic (3.5 meter wide) laser pointer and also as a signal receiver. Staying close to 10 cm over 1 km would seem to be possible with good optics+optomechanics and the right laser (for example, laser diodes, such as ones found in laser pointers, have horrible inherent divergence issues)

I’m not sure how to find the list of people following me.

Laser implies a certain source (stimulated emission). There may be issues of coherence of the light and beam quality with beams, but I’ve used 50mm beams without any issues. Still able to do laser cooling and trapping. We expanded the beams using lenses. I can’t see your embedded image Vision impairment is an intensity issue, which is made worse by having a collimated beam The eye is most sensitive in the green (555 nm), ~5x more sensitive in green than red (~650 nm). this shifts a little toward shorter wavelengths if your eye is dark-adjusted https://www.ncbi.nlm.nih.gov/books/NBK11513/figure/ch24psych1.F10/ The effective range is going to depend on the beam’s divergence. If it’s 10 cm at the target, a few mW should be visible.

JohnSSM has been suspended to see if he can get rid of the chip on his shoulder. Stirring the pot because you’re bored isn’t an acceptable exercise