I always phrase it as “some of us need to roll a 20 to think critically.”

Kind sir or madam, may I remind you that this is slashdot.

Ive had two dogs that would refuse to eat too much dog food, they weren’t the eat now ask questions never type. I always refilled a large bowl and they always had food but neither were overweight. They both were very picky and preferred human food and on the rare occasions they got some or stole some they didn’t have the sense not to stop eating when full and kept eating stuff that made them sick because there are so many things dogs can’t tolerate that we can. One of them even ate American toads despite having to immediately barf them up in a bath of foam because they are mildly toxic, though after maybe the 20th time it learned. So the problem could be in that todays food is highly unnatural in that it’s incredibly nutrient and calorie dense, is extremely tasty, is cheap and available almost instantly everywhere and people just aren’t equipped to deal with that.

Just to add, I have the opposite problem in that I have metabolism issues where I can eat insane amounts of calories and not gain weight. Right now I always am trying to eat more than I’m hungry for, probably around 3k+ calories per day and I’m old and moderately active certainly not some kind of professional athlete. My body fat is around 7-10% (it makes me look grotesque and bizarre) and I have a bmi of about 19 which is very close to underweight. When I was younger I used to make people very angry by eating 5-6k calories per day with the same body fat though I was a bit more active then and had more muscle but not some kind of extreme athlete where its justified. Not being able to gain weight and needing to eat extra food is not a good thing, it makes me look very different and gaining muscle is harder for me than it probably should be. There are likely all kinds of things this puts me at risk for, not to mention that our ancestors didn’t exactly live through rough times if they have metabolism issues like that.

Yes, that’s wrong everything goes in. I was trying to emphasize that originally mass and energy were simply less distinct because of how the boundary to the problem was approached. Put simply the energy intrinsic to the particle or system itself wasn’t thought of any differently than particles whose energy is completely relative like photons. The only difference to today is just how the math is arranged.

E=mc^2 is a special case where the relative velocity of target and observable or two points is zero. You need to introduce an energy term for apparent mass gain from velocity just like you want to create the stress energy tensor in two parts one with light speed momentum particles and one for mass based relativistic particles. It’s not wrong to just not care which is which if you account for it correctly, but separating them into parts depending on if they are intrinsic to themselves at least in part or purely relative is useful for intuitive understanding and keeping things neat in terms of energy and momentum.

100% as long as you don’t suddenly change your mind about taking full responsibility for your actions when suddenly what all the statistics say is likely to happen, happens. With a for profit insurance medical care system this means saying too bad and letting you suffer or die. Without a home because you can’t work anymore you get thrown to the streets where we all have to deal with you for up to several years before our problem goes away. If we had a system of say medical care for all, very modest but safe public housing for free in the same area you are from, and a very modest basic income to cover some things with actual robust food shelves providing adequate amounts of basic nutrition like beans and rice for free this would not only allow you to make those choices with less severe repercussions on average and at the same time, remove our problem in having to clean up a pound of mess when the cure was just a pinch.

There is no edge, every point is at the precise center including your two eyes. Because light, gravity waves, and causality travel at a single fixed speed, the further something is the farther back in time it is until you reach a point where you cannot see beyond because it is too far back in time and approaches the Big Bang. Gravity waves from the Big Bang will be rippling through all points always just as you can look in any direction and see the microwave background which is the Big Bang but stretched out to the point it’s far cooler and of longer wavelengths.

Gravity waves are fundamentally undetectable, even in principle. If you want a nearly exact example you are probably familiar with think of two floating bits on a still lake. Perception only occurs along the surface of the water, they cannot see or measure or perceive up and down. When a ripple passes the two bits move toward and away from each other as the surface stretches and shrinks to accommodate the wave and that is the distortion that is measured not the wave itself. It boils down to the second derivative of the mass quadrupole moment tensor and it falls off linearly with distance so is not like other directly measured waves that fall off exponentially.

The universe is the same everywhere at the largest scales including being at the exact temperature despite not being casually connected if you look at how causality works on our scales, times, and energy levels. The most reasonable thing is that the universe was once all touching in close contact, even points 90 billion light years away from each other. The universe is also expanding the same everywhere on the largest scales so if you rewind time everything goes back to one point even if there isn’t a “center”. So the crazy thing is to look at all the evidence for it (many other examples of measurement also confirm this is how it looks) and say it’s all wrong because it does not meet personal expectations. That’s not how science works.

Well then, you’ll probably also miss out on the underwear running on a blockchain with a camera to verify the person is the right age and with the right gonads to be wearing it. Once the video is uploaded, it disables the high voltage circuits that will put a stop to indecency.

Forgot to add above that similar to a contained gas having increased rest mass with increased temperature if you have a 100% reflective box and put even one photon in it the box is said to have increased rest mass while if you release it from the box it is not said to have rest mass. Clearly the photon is unaltered and the difference is the box isolates it from the greater system although this is an arbitrary distinction it clarifies how the problem is framed and that’s why its convention.

Take an insanely energetic photon, well above the gamma ray cutoff, for ease of experimentation, with respect to the test mass and have it travel through space. Place a known test mass just off to the side of the path such that the interaction chance like absorbing or reflecting is nearly zero. Observe the two from a distance arbitrarily far away and start with the test mass at a relative velocity of 0. As the single photon flies past, the test mass is accelerated toward the photon and the photon path is bent slightly. Without a gravitational field associated with the photon, this is hard to explain and it’s well established photons carry a relative gravitational potential as well as the original formulation of relativity and physics in general did not distinguish between rest mass creating gravitation and light speed particles generating gravitation yet conveyed the same accuracy as today. All the formulas describing rest mass and light speed particles were about how you draw the boundary of the problem and not about any other real difference. Heat a contained gas and its internal energy and thus rest mass increases. Leave the same kinetic energy and free the gas and now it’s not the actual particle that has increased rest mass, nor are any changes relevant from its own perspective, it’s energy lies tangled with the greater system even though the same test as above would in fact measure free gas molecules as having greater gravitation.

We already have demonstrated solar sails and even proposed using a magnetic field with them as a sort of keel to get more energy from the solar wind environment. We also have some basic demonstrations on laser propelled sails. No one has actually used or tested laser sails in space as far as I know due to costs but the physics behind it is solid and well known

| was referring to self contained light sources which all are so heavy resulting in weak thrust to mass of the ship, we don't even have concepts of a plan yet. The cool thing is with a lost energy (lower output than input) fusion drive, something like 1-3% of the thrust would be from photon momentum transfer making it at least in slight part the first demonstration of a self contained photon assisted mass driver engine.

In an abstract sense photons have mass, but it is not the same as rest mass and so the convention is to call it massless. This is an important distinction not because equations can’t be made accurately and precisely but because it’s useful to break down the thinking of energy from mass to be intrinsic to the particle or intrinsic to the larger system as a whole. They have _momentum_ which they transfer by absorption or reflection causing a corresponding momentum change in the particle(s) but the mass is precisely zero for all photon energies.

The practical problem is the fact dense clouds are on the order of milligrams per cubic mile and it’s not just one isotope or element that might be collected it’s the scale of the magnetic field. In the case where the field acts as an external fusion reactor, this does not work because of all the dead mass you would try to heat but also it’s not plausible to craft a ship with that scale of magnetic field not even counting a design also isn’t so fragile the act of traveling alone will cause it to rapidly self destruct from impacts.

Even carrying antimatter as a large percentage of your ships mass (again not plausible due to magnetic fields able to completely contain it) won’t get you to even nearby stars in a reasonable number of years much less sci-fi levels of speed. Part of the reason we might not see life everywhere is interstellar travel is incredibly difficult, delays communication, and is dangerous so it takes place on extremely long timeframes while advanced life moves at breakneck speed and relies heavily on quick communication.