Relativity

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Re: Relativity

Post by mistermack » Mon Mar 26, 2018 6:34 pm

laklak wrote:If you're talking about a Mars flight then the sun, earth, mars, and the spacecraft would be in the same frame of reference, IIRC. It's physics, Jim, but not as we know it.
The equations of special relativity work for ANY inertial frame of reference.
General relativity includes the effect of gravity of curving space time. In general relativity, the solar system is in free fall, in curved space time around the milky way. So it's not actually accelerating at all in GR, it's following the curvature of space time.
It just so happens that at the the speed of an orbiting body in a stable orbit around a bigger body, the space time around the big body is curved so that the satellite continues in an ellipse, in the same way that it would travel straight, in non-curved space time.
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Re: Relativity

Post by JimC » Mon Mar 26, 2018 9:02 pm

mistermack wrote:I think the acceleration towards the centre of the galaxy is actually incredibly tiny.
If you consider that we only rotate around 360 degrees, and it takes 250 million years, compare that to the child on the roundabout, who does the same rotation in a few seconds.
So for practical purposes, I would say that it can be safely ignored.
I'm fairly certain you are right. In this context, centripetal acceleration of the solar system as it orbits the centre of the galaxy would be absolutely minute.
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Re: Relativity

Post by pErvinalia » Tue Mar 27, 2018 1:04 am

mistermack wrote:
pErvinalia wrote:We are talking about relativity, not a space flight to Mars.
I don't think you have much of a clue about either.
Oh here we go again. The science conspiracy theorist thinks he is in a position to lecture anyone about science. :bored:

You've made a claim, and you can't back it up. Either back it up, or go back to the conspiracy threads.
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Re: Relativity

Post by pErvinalia » Tue Mar 27, 2018 1:07 am

laklak wrote:If you're talking about a Mars flight then the sun, earth, mars, and the spacecraft would be in the same frame of reference, IIRC. It's physics, Jim, but not as we know it.
But they are not in an inertial frame, because they are accelerating. SR deals with inertial frames. MM has yet to tell us the effect that acceleration has on SR calculations, other than to offer speculation.
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Re: Relativity

Post by Forty Two » Tue Mar 27, 2018 4:26 pm

pErvinalia wrote:
mistermack wrote:
pErvinalia wrote:We are talking about relativity, not a space flight to Mars.
I don't think you have much of a clue about either.
Oh here we go again. The science conspiracy theorist thinks he is in a position to lecture anyone about science. :bored:

You've made a claim, and you can't back it up. Either back it up, or go back to the conspiracy threads.
....says the guy who thinks his unsupported declarations constitute automatic default positions, which need not be supported, and which everyone else has the obligation to prove wrong....

You demanding someone "back up" a position is quite humorous.... lol. I'm sure mistermack will get right on it and comply tootsweet with your demand, given how often you respond with clear, non-evasive, back up for your own positions....
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Re: Relativity

Post by mistermack » Tue Mar 27, 2018 11:14 pm

It's quite a stunning illustration of just how brief our lives are.

In the last million years, the change in direction of the Sun around the Milky Way is about 1.44 degrees.

The last time we were in this position in the Galaxy, the Earth was devastated by the Permian–Triassic extinction event when about 95% of seas species and 70% of land species died out.
It was still millions of years before the first mammals evolved. That's how slow the galaxy rotates.

It's just mind boggling to imagine what the Earth will be like the next time it's back here. Will humans be extinct? We certainly won't be anything like the humans you see today.
We evolved from typical apes over the last 7 million years. What will another 250 million do to us?
The odds are that there will be another mass extinction event. In fact, probably more like five, over that period.
That's why we need to get out into space on a permanent basis.
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Re: Relativity

Post by pErvinalia » Wed Mar 28, 2018 1:02 am

Forty Two wrote:
pErvinalia wrote:
mistermack wrote:
pErvinalia wrote:We are talking about relativity, not a space flight to Mars.
I don't think you have much of a clue about either.
Oh here we go again. The science conspiracy theorist thinks he is in a position to lecture anyone about science. :bored:

You've made a claim, and you can't back it up. Either back it up, or go back to the conspiracy threads.
....says the guy who thinks his unsupported declarations constitute automatic default positions, which need not be supported, and which everyone else has the obligation to prove wrong....

You demanding someone "back up" a position is quite humorous.... lol. I'm sure mistermack will get right on it and comply tootsweet with your demand, given how often you respond with clear, non-evasive, back up for your own positions....
That's nice and all, but it doesn't change the fact that he made a claim that he won't support. :bored:
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Re: Relativity

Post by pErvinalia » Wed Mar 28, 2018 1:07 am

mistermack wrote:It's quite a stunning illustration of just how brief our lives are.

In the last million years, the change in direction of the Sun around the Milky Way is about 1.44 degrees.

The last time we were in this position in the Galaxy, the Earth was devastated by the Permian–Triassic extinction event when about 95% of seas species and 70% of land species died out.
It was still millions of years before the first mammals evolved. That's how slow the galaxy rotates.
That still doesn't answer the question. And don't forget, orbiting around the galaxy isn't the only source of acceleration. I only chose it as I mistakenly assumed that it would be by far the largest. But with further understanding I see that both the yearly orbit and the daily spin of the Earth are greater levels of acceleration. The fact is that SR deals with inertial frames. A body accelerating (no matter how much it is) isn't in an inertial frame. You've suggested that when it's small (relative to what objective standard?) it doesn't matter and can be disregarded. I'm waiting for you to back this claim up with something. A feeling in your guts, isn't a reputable source..
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Re: Relativity

Post by mistermack » Wed Mar 28, 2018 9:17 am

God you're acting the clown. You have very little understanding of relativity, as you've shown already, but you keep trying to pretend. Why don't you actually say something, instead of bullshitting?
Answer, because as soon as you do, you get it wrong.

Such as :
pErvinalia wrote:
mistermack wrote:
pErvinalia wrote:Acceleration is m/s/s, not degrees/s/s.
Acceleration is change in velocity over time.
As velocity has both magnitude and direction, in the case of rotation around the centre of the Milky way, it's the change of direction that's relevant, not the speed at any instant.
Good point.
I've already answered your dumb question, when I posted about general relativity and the curvature of space time being responsible for the "apparent" acceleration towards the centre of the Milky Way. You obviously didn't read it, or didn't understand it.

You went on to waffle :
pErvinalia wrote: But still, both station and train are accelerating. Is the effect of acceleration/gravity linearly related to its effect on the Special Relativity equations? What I mean by that is, is the fact that it's only a small amount of acceleration/gravity mean that it only introduces a small variance into the Special Relativity equations?
You only need to know a tiny basic bit to know the answer :
wikipedia wrote: The theory is "special" in that it only applies in the special case where the curvature of spacetime due to gravity is negligible.[6][7]
pErvinalia wrote:
laklak wrote:If you're talking about a Mars flight then the sun, earth, mars, and the spacecraft would be in the same frame of reference, IIRC. It's physics, Jim, but not as we know it.
But they are not in an inertial frame, because they are accelerating. SR deals with inertial frames. MM has yet to tell us the effect that acceleration has on SR calculations, other than to offer speculation.
This is absolute bollocks. Everything is in an inertial frame. You can of course accelerate in an inertial frame.
Why the fuck do you blog on when you don't know what you are talking about?
The point about general relativity is that it's a model that handles gravity and accelerating frames more easily.
wikipedia wrote: The theory is "special" in that it only applies in the special case where the curvature of spacetime due to gravity is negligible.[6][7] In order to include gravity, Einstein formulated general relativity in 1915. Special relativity, contrary to some outdated descriptions, is capable of handling accelerations as well as accelerated frames of reference.[8][9]
I've made the point in different ways that the curvature of space time in our location due to the Milky Way is negligible. That's perfectly relevant, as stated above.
It's not negligible, if you are talking about timeframes of 250 million years, again as I pointed out.
If you had had the slightest clue what you were talking about, you would have understood all that.
As it is, your input is a waste of space. Literally.
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Re: Relativity

Post by pErvinalia » Wed Mar 28, 2018 10:35 am

We are talking about SR, not GR. And there are greater accelerations going on than orbiting the galaxy. As I said, orbiting the sun, and spinning on our axis. And at least three times by two posters you've been asked to quantify "negligible" (or the like). That should be easy for someone of your obvious genius.

Moving on to inertial frames. The point of inertial frames is that an OBSERVER in one measures the same laws of physics as another OBSERVER in a different inertial frame. If the observer is accelerating, he's categorically NOT in an inertial frame.

Regarding SR handling accelerated frames of reference... Ok, I can accept that now. However, it specifically doesn't deal with gravitational "acceleration". SR is actually "special" because it is a special case of GR (it wasn't named "Special Relativity" until after GR was formulated) in flat spacetime. Not "negligible" gravity. And the references of the wiki article refer to flat spacetime, not "negligible" gravity fields. Even your own bloody link makes this perfectly clear:
The only sense in which special relativity is an approximation when there are accelerating bodies is that gravitational effects...are being ignored.
....
Special relativity gives a completely self-consistent description of the mechanics of accelerating bodies neglecting gravitation, just as newtonian mechanics does.
.....
In special relativity space-time is always flat.
http://math.ucr.edu/home/baez/physics/R ... ation.html

So SR technically can't apply to a real world twins paradox (or train relativity of simultaneity) experiment. You would need to use GR.
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Re: Relativity

Post by mistermack » Wed Mar 28, 2018 10:48 am

You're so full of shit it's oozing out of you.
Everything you write shows how little you understand, but you don't get it for the same reason.

What is "flat space time" Einstein? How is it different from "negligible gravity fields"
And where will you find it?????
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Re: Relativity

Post by pErvinalia » Wed Mar 28, 2018 10:51 am

Flat spacetime is absence of gravity (which is curvature of space; i.e. NOT FLAT). As I said, YOUR OWN LINK REFUTES YOU! :lol:
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Re: Relativity

Post by pErvinalia » Wed Mar 28, 2018 10:55 am

What you are yet to answer is:

How is "negligible" quantified?
How it is accounted for in the SR equations?
And how does this hold given that SR specifically doesn't deal with gravitation fields?
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Re: Relativity

Post by mistermack » Wed Mar 28, 2018 11:00 am

pErvinalia wrote:Flat spacetime is absence of gravity (which is curvature of space; i.e. NOT FLAT). As I said, YOUR OWN LINK REFUTES YOU! :lol:
And where will you find it, Einstein????
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Re: Relativity

Post by pErvinalia » Wed Mar 28, 2018 11:26 am

Nowhere. But that has absolutely nothing to do with your unsupported claims.
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