Thread: Relativity? Can you guys please teach me?

Hello.
If the special relativity primer, the sticky in this forum, answers all my questions, please excuse my stupidity for posting this thread but it appeared to me as if it didn't or I'm simply not capable of applying the sticky to my problems. Therefore it'd be very kind if you could lend me a hand and explain the answers.

Also, please note that I've posted those questions in a different forum before but I decided to try and post them here since I didn't get any answers even after waiting for 5 hours.(it was the science forum on 4chan)Therefore, please excuse the bad formating, the [quote] tags arn't working for me.


This was my first post. I bumped the topic with questions, I find the latter questions more interesting.
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Hey.

I once read that our solarsystem travels at about 270km/s inside the milkway and the milkyway itself is heading towards another galaxy at about 300km/s and the earth travels around the sun at 30km/s.

Currently, I measure a year with the help of the sun. If I orbit the sun once, a year has passed, I'll have traveled about 970000000km or something.

Here is my first question.
Let's assume somebody invents a anti-gravity device. The only thing that keeps my feet on this planet is gravity. If I use this anti-gravity device on myself, will I see the earth vanishing below my feet at some point?

Next question.
Assuming the earth does vanish below my feet at some point, will I be traveling around the universe at 600km/s?

Next question.
Assuming this anti-gravity device has some kind of mechanism that allows me to freeze i.e. stopping completly and not moving anymore and assuming I'm carrying some super powerful telescope., what will the earth look like if i look through this telescope onto the earth?(will it be slowmotion like?)

Next question.
Assuming I've stopped completly and I do now see the earth moving at 600km/s and since previously I measured one year by traveling 970000000km, what time is passing for me and what time is passing for the earth?

Next question.
Any chance one year is only gonna take 20 days?


This is the first bump with more questions.
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Bump
I know that according to relativity, it won't make a noticable difference time-wise.
I'm mostly curious because the earth would look/be very strange as far as I can tell.

For example, take a guy that's throwing a basketball 10 meters. I see two things when looking at him through my telescope:
1) he's throwing it 10 meters
2) he's throwing it 600kilometers+10 meters

What's true?

Also;
For me who's standing still, the energy required to accelerate a ball to 600km/s is tremdous yet for him, he does it with only one hand although he has the very same body.

Also;
I read that the fastest manmade machine travels at 21km/s(some scouting device in space). Isn't it, in reality, traveling at 621km/s?


2nd bump.
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Just to get back to the basketball, by any chance, is the answer that it's the guy who's throwing it 10 meters but the galaxy that's throwing it 600km? Can we use the power of this galaxy?


3rd bump
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It must be true that he's only throwing it 10 meters while the galaxy throws it 600km.

Else I'd have to imply that if I reach 600km/s, I'd be in some sort of frame in wich I'm traveling at 0km/s while traveling at 600km/s but since I'm only traveling at 0km/s, the required energy to accelerate to 1200km/s is the same as the energy I previously used to reach 600km/s wich would mean that accelerating a spaceship with shocks would require less energy and be faster.

Assuming I'm on a planet that's traveling at 3000km/s, is the sonic barrier also at 1000km/h?


Here are some questions people asked and my answers, can you tell me if they're correct? If they're wrong, can you please explain?
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Q:Have you ever jumped off the ground?
A:Yes but I got pulled back by gravity. I suppose that if gravity wouldn't affect me, I would just keep on going up and in the direction the earth is going until the orbit of the earth becomes a problem?

Q:If you are looking at him through a telescope on earth, you see him throwing a ball 10 meters relative to himself. If you are not on earth, where are you? Are you still? What would you be still relative to?
A:I am somewhere where I can watch the earth traveling at 600km/s. Ofcourse I can never tell if I'm really not moving anymore but I can get to a point where the earth travels at 600km/s relative to me, is this not correct?


More questions I didn't ask because nobody answered.
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-Is the quantum world not relative? At what point arn't you relative anymore?
-If we'd travel back from the point where we watched the earth travel at 600km/s, is there any chance we will get ripped apart by gravity?
-The mass of the basketball player must be gigantic, he must have the same mass as a human traveling at 600km/s. Does that mean that gravity isn't as weak as everybody keeps saying? Gravity must be super huge!
-Is gravity relative like light and electromagnetism non-relative?
-Can you connect gravity and electromagnetism this way?

One last little thing.
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Some guy said:""anti gravity"

this is nonsensical
you need to at least attempt a mechanism, or else a lot of this shit becomes pointless"

While the first few questions imply that you have an anti-gravity device, the latter don't I guess because you could use a spaceship and reach a place where you could watch the earth traveling at 600km/s. You would just have to slow down, alot.


Thanks alot for your input.

You use speeds in an absolute term because you assume things having no speed. For onstance the universe has speed zero and you define speed earth relative to that. But how did you het to a point where the universe has speed zero ? What is that speed zero ?
It,s rubbish to assume such things. Speed is relative : thus it is not a property of something. It is relative.

Earth has speed relative to the sun ? The ocppsite it,s the same. Things move relative to other things. We are not used to think that way maybe but in fysiscs that, how it is.

Someone who would say that an atlethic court has a speed of hundred meters per ten seconds to a runner is just as right or wrong as someone saying that the athlete runs with hundred meters per ten sec. There is no preferred point of view in nature. So speed as property is nonsense.

People come to such ideas becaue they assume "things" having speed zero.
The only thing that has speed zero for anyone is the fysical being of that person (and within that there is movement also offcourse, arms move relative to legs and blood runs through you,re vessels).

If that person sits on a tribune at the athletics stadium the tribune doesn,t move, the track doesn,t move and hence (as there obviously is movement) the athlete moves with the speed becoming a property of the athlete.

It,s always a specific point of view from which things are supposed to have a specific speed beit zero or not zero (which automatically implies something else with speed zero). Because specific it is made absolute to a subjektiv point of view.

For instance if you say that a person has a speed of five km,s/hour relative to you

I don,t know much. You can be running or the other person. How would I know ?

Now you say that you sit in a chair and see another one move at that speed. He will see you move as he moves himself. Allthough I know more if I stand still or sit in a chair the speed is still not a property of something it,s relative. If I by accident would be reading such in a train that moves with a speed in the same or another direction. You,re speed will be different and the persons speed also.

Same way with the sun and earth.

You assume all readers will be in rest with the earth. Hence see the sun move. Turn it round and say the earth moves relative to the sun (the sun not move) but the sun moves also. An astronaut on the moon will see the earth move but also the sun.

So speed is never a propertie of something it,s relative. And as there may be preverred standpoints, points of view in daily life, in fysics the standpoint of the man on the moon or anybody elses standpoint is ecqual. Nature, the universe whatever doesn,t give us any preferred standpoint.

Well as far as I understand, there are only 2 scenarios in wich you can see the earth traveling at 600km/s.
A) You're moving at 1200km/s
B) You're moving at 0km/s
I assume that you need a point of reference to tell in wich scenario you're in right? An immovable oject would help?

Can't we just assume that we have an immovable object right by us? That way we'd now if we're in scenario A or B.

Also, does it even matter what scenario we're in?

Originally Posted by 881tob

Well as far as I understand, there are only 2 scenarios in wich you can see the earth traveling at 600km/s.
A) You're moving at 1200km/s
B) You're moving at 0km/s
I assume that you need a point of reference to tell in wich scenario you're in right? An immovable oject would help?

Can't we just assume that we have an immovable object right by us? That way we'd now if we're in scenario A or B.

Also, does it even matter what scenario we're in?

I will find a way!

Originally Posted by 881tob

Well as far as I understand, there are only 2 scenarios in wich you can see the earth traveling at 600km/s.
A) You're moving at 1200km/s
B) You're moving at 0km/s
I assume that you need a point of reference to tell in wich scenario you're in right? An immovable oject would help?

Can't we just assume that we have an immovable object right by us? That way we'd now if we're in scenario A or B.

Also, does it even matter what scenario we're in?

There are an infinite number of scenarios, depending on what you choose as a reference frame. You moving 300 km/s in one direction and the Earth moving 300 km/s in the, You moving 100 km/s in one direction and the Earth moving 700 km/s in the same direction, You moving at .0001 km/s and the Earth moving at 600.0001 km/s...

The point being that each is based on an arbitrary choice of the reference frame you choose to call "at rest". And that's all your choice can be, arbitrary. There is no such thing as an immovable object, because every object moves relative to some frame, just as every object can be said to be at rest relative to some frame. There is no one "right" answer. Every reference frame is equally valid and none can be said to be better than any other other than for the sake of which is more convenient.

Originally Posted by Janus

Originally Posted by 881tob

Well as far as I understand, there are only 2 scenarios in wich you can see the earth traveling at 600km/s.
A) You're moving at 1200km/s
B) You're moving at 0km/s
I assume that you need a point of reference to tell in wich scenario you're in right? An immovable oject would help?

Can't we just assume that we have an immovable object right by us? That way we'd now if we're in scenario A or B.

Also, does it even matter what scenario we're in?

There are an infinite number of scenarios, depending on what you choose as a reference frame. You moving 300 km/s in one direction and the Earth moving 300 km/s in the, You moving 100 km/s in one direction and the Earth moving 700 km/s in the same direction, You moving at .0001 km/s and the Earth moving at 600.0001 km/s...

The point being that each is based on an arbitrary choice of the reference frame you choose to call "at rest". And that's all your choice can be, arbitrary. There is no such thing as an immovable object, because every object moves relative to some frame, just as every object can be said to be at rest relative to some frame. There is no one "right" answer. Every reference frame is equally valid and none can be said to be better than any other other than for the sake of which is more convenient.

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