I Battery life on VERY fast moving object

[davidjoe]

Someone in free fall (and reasonably nearby) will find that the Empire State Building, foundations and all, is accelerating at 1g while they are at rest and their accelerometer is reading zero, no force because they’re free-falling. On what basis do you justify the claim that your perspective (no movement relative to you and the surface of the earth) is more “real” then the free-faller’s perspective (earth and building are moving towards them?

Before you answer, I’m going to add one more thing: the person you are trying to convince is an astronomer on Mars, sitting peacefully in their easy chair and watching through a telescope - so as far as they are concerned the free-faller and the surface of the earth are both moving.

It’s not that one is more real than the other.

Someone in free fall, in a vacuum, never stops accelerating, right? So, there is always more gravity “forcing” them to go faster, wherever they are in the fall, until they pass its source. Unlike floating in space you are being accelerated in free fall. By this, perhaps the accelerometer at highest sensitivity will never read zero. I have understood their function to follow their name.

If the Zero G airplane doesn’t keep its downward speed going, the occupants no longer experience zero G. It’s simply removing wind resistance. I could be wrong but what we call weightless, in water, free fall, or the zero G plane, is not the same as weightless where there is truly minuscule or no gravity.

 

[jbriggs444]

It’s not that one is more real than the other.

Someone in free fall, in a vacuum, never stops accelerating, right?

In the Newtonian model under constant gravity, yes. That is unrealistic. There is no such thing as an infinite constant gravity well.

The relativistic model of gravity is something else again. Someone in free fall is not accelerating at all. It is just that some choices of coordinate system accelerate upward relative to freely falling objects.

Unlike floating in space you are being accelerated in free fall. By this, perhaps the accelerometer at highest sensitivity will never read zero.

I have no idea why you think that a coordinate acceleration is detectable by a sufficiently sensitive physical accelerometer. It cannot be. Coordinates are things that are conjured with pencil and paper. They are not physical.

 

[davidjoe]

It does not. Mass (in the modern accepted meaning) does not increase with velocity at all. We do not use relativistic mass. We use rest mass. Also known as invariant mass. And call it "mass". See our Insight article here.

In the modern terminology, "mass" is the energy (divided by c²) of an object in a frame of reference where it is at rest.

A slightly more general definition is that the "mass" of an object is the magnitude of its energy-momentum four-vector. That is to say, $m^2 = E^2c^4 - p^2c^2$. In the case of anything moving at light speed, $E^2 = p^2c^2$ and $m=0$.


Yes. If mass is constant, energy increases without bound as speed increases without bound.


Common people who have not taken a course in real analysis have a rather lacking understanding of infinite quantities.

Are not on topic in this thread.

More generally, if your mission is to kvetch about physics, you need to find some scholarly references. Or another forum.

I will read that. It can’t be overstated how much I appreciate someone saying that mass does not go to infinity.

 

[PeterDonis]

I think an accelerometer does not detect force, just movement.

It detects proper acceleration, which is produced by a force. Proper acceleration is not the same thing as movement.

If I attached one to the base of the Empire State Building

It would read nonzero because the Empire State Building has nonzero proper acceleration, because it is being pushed on by the Earth's surface. Or, to put it another way, it has weight.

and then shoved on it, there’s force but no movement.

Yes, but the accelerometer, if it were sensitive enough, would detect the force you exerted as a change from the force (weight) that it was being subjected to before. And that would be the case even if the building itself did not move at all relative to you.

 

[PeterDonis]

Mass going to infinity

"Relativistic mass" is an outdated concept. If you search PF on that term you will find plenty of previous threads explaining why.

 

[PeterDonis]

Someone in free fall, in a vacuum, never stops accelerating, right?

No. Someone in free fall has zero proper acceleration.

That someone might have nonzero coordinate acceleration relative to some other object, such as the Earth (for example, the International Space Station in its free-fall orbit), but coordinate acceleration is a frame-dependent quantity, not an invariant. Proper acceleration--what an accelerometer measures--is the invariant.

 

[PeterDonis]

there is always more gravity “forcing” them to go faster

Gravity is not a force in GR.

 

[PeterDonis]

I could be wrong

You are. See below.

As an observation: an awful lot of what you think you know about physics appears to be wrong.

but what we call weightless, in water, free fall, or the zero G plane

Are already not all the same. "Weightless" floating in water is not actually weightless; an accelerometer attached to you does not read zero. Free fall, such as the International Space Station in orbit, or being in the zero G plane during the weightless part of its trajectory, are weightless; an accelerometer attached to you reads zero.

is not the same as weightless where there is truly minuscule or no gravity.

Wrong. Free fall/zero G plane are the same "weightless" (accelerometer reads zero) as "where there is truly miniscule or no gravity".

 

[Drakkith]

A true outsider’s perspective is interesting sometimes, maybe in my case concerning what is or isn’t as difficult to accept, or to grasp.

Don't take this the wrong way, as I'm not trying to insult you, but we get people like you every day here at PF. Our goal is literally to help people who don't understand science (you and 99% of everyone who comes to PF) learn about science. Most of us long-time members are well aware of what is and isn't easy to grasp in various subjects.

I think the YouTube sound bites by about 5-10 physicists or pop physics personas are for views yes, but also possibly an “inside baseball” pump the brakes message to academia saying hey, look where this is leading, especially in the logical extreme of this or that, subject.

Not really. These kinds of videos or sound bites are for keeping the public up to speed in what is happening in various fields, generating general interest in science, and possibly many other reasons. But I don't think that anyone is seriously trying to send 'academia' or other scientists a message using them. There are plenty of other ways to do that, like conferences, lectures, professional meetings, publications, etc.

Theories that support infinite universes, again, I would wonder what being observed can lead one to think there are infinite universes. 10 to the 500th power of string theories. As an outsider, one thing I don’t see is much public criticism of another’s ideas, in the field. Not saying it doesn’t happen. I’m just wondering how they get the momentum they do, such as string theory did.

Criticism outside of professional avenues is generally something to be avoided, as it tends to be viewed as petty and unprofessional. Besides, a good critique of a field generally requires advanced knowledge and explanation using math and everything else to show that the critique is valid. This doesn't lend itself well to podcasts, videos, or other avenues of talking to the public since the public wouldn't understand any of it anyways unless it is vastly simplified. And if it's vastly simplified then it isn't useful to the person(s) being critiqued. They're better off just reading the full article critiquing them and responding in kind.