# What is Spacetime?

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Nobody, Oct 22, 2011.

1. ### hansdaValued Senior Member

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How 'lightyear' can describe time ?

Consider two stars are at a lightyear distance apart . Two events can happen simultaneously at these two locations or there will be some time-delay between these two events . What idea of time-delay between these two events ; you can make out from lightyear ?

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3. ### NietzscheHimselfBannedBanned

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Like most units do. With a number.

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5. ### KilljoyKlownWhateverValued Senior Member

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A light-year, also light year or lightyear (symbol: ly) is a unit of length, equal to just under 10 trillion kilometres (10×1015 metres, 10 petametres or about 6 trillion miles). As defined by the International Astronomical Union (IAU), a light-year is the distance that light travels in a vacuum in one Julian year.

The light-year is often used to measure distances to stars and other distances on a galactic scale, especially in non-specialist and popular science publications. The preferred unit in astrometry is the parsec, because it can be more easily derived from, and compared with, observational data. The parsec is defined as the distance at which an object will appear to move one arcsecond of parallax when the observer moves one astronomical unit perpendicular to the line of sight to the observer, and is equal to approximately 3.26 light-years.

One light-year is equal to:
exactly 9,460,730,472,580.8 km (about 9.5 Pm)
about 5,878,625,373,183.608 miles (about 6 trillion miles)
about 63,241.1 astronomical units
exactly 31,557,600 light-seconds

The figures above are based on a Julian year (not Gregorian year) of exactly 365.25 days (each of exactly 86,400 SI seconds, totalling 31,557,600 seconds) and a defined speed of light of 299,792,458 m/s, both included in the IAU (1976) System of Astronomical Constants, used since 1984.

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7. ### hansdaValued Senior Member

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So, lightyear only tells us about distance and tells nothing about time .

8. ### NietzscheHimselfBannedBanned

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Time only exists in your mind.(space-time exists physically) The consequences of this observation is a number that represents the movement of every object in the universe in that duration. So instead of imagining all that you say an hour.

We measure this aspect with a distance, because it is easy for your mind to understand the concept. (and to stress how far things have spread out since it was all one object.) Which would be a measurement of "space", Which happens to only be acessable physically if we include some sort of motion (time).

Oooo circular...

What is time? What is space? What is the universe? What is energy?

Ask the light. He knows.

9. ### KilljoyKlownWhateverValued Senior Member

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Yes, How far can light travel during the time it takes the earth to make one revolution around the sun.

But, the fact that movement from A to B can be measured in units we call time, does tell us something about time.

10. ### parulRegistered Senior Member

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space-time is other dimension other than the 3 we know, i assume lol

11. ### hansdaValued Senior Member

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true. I agree .
Space has a unit . We can measure space(distance) through some means , say a tape .

Time has a unit . We can measure time through some means , say a clock .

What is the unit of space-time ? ... How space-time can be measured ? ... Is it through 'lightyear' ?

12. ### hansdaValued Senior Member

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Perhaps the literal unit of space-time can be ' light-year square ' .

I think GP-B experiment was carried out to measure space-time .

So, no way lightyear can measure space-time .

13. ### hansdaValued Senior Member

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NASA carried out an experiment to measure spacetime . http://science.nasa.gov/science-news/science-at-nasa/2011/04may_epic/ .

In this experiment gyros were used as probes to measure spacetime .

We know that gyro can only respond to force or force-field .

So, this experiment also confirms that ; spacetime , basically is a force-field .

14. ### wellwisherBannedBanned

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Space-time is a mental construct used to help us model physical observations. If we wanted to, we could model space-time using spherical coordinates. This system would have one distance variable=r, one time variable=t and two angular variables, say alpha and beta. This would make it harder, but it is possible.

In this hypothetical spherical model for space-time, we would need to come up with a way to explain the conceptual meaning of the two angles, alpha and beta, as it relates to time. Although harder to use, mathematically it will come up with the same results. This approach might lead to speculation of how time is connected to angles, or whatever. The final image of the angular nature of space-time, would still be all in the mind, based on whatever will give us a useful way to model reality. But it is in the head, based on a type of human creationism, where we create the universe (perception) in our own image.

There are many ways to do the same thing, with each way, like using spherical coordinates, requiring its own assumptions and speculations. Reality can quite different for different space-time construct, such as the unique meaning of the angles alpha versus beta in the light of time? Science was brooding over the deep and it said. " let there be x,y,z instead of r and 2 angles ".

That being said, my approach for constructing a new space-time was, why not compress this even more. Who decides how far we need to fluff the mental construct. Is it done by committee?

15. ### NietzscheHimselfBannedBanned

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If you can show how much mass this force field has, then people might actually let you call it a force field.

16. ### hansdaValued Senior Member

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How much mass our universe is having ? ... All of them are responsible for this force-field . All these masses are distributed throughout the space of our universe . So , the force-field is also present at every location of our universe .

Last edited: Dec 10, 2011
17. ### hansdaValued Senior Member

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NASA experiment confirms Einstein's space-time .

NASA experiment also confirms that , space-time basically is a force-field ; because gyros were used in these experiments and we know that , gyro can only measure force .

So , space-time is neither space nor time but force-field . This force-field exists throughout space and time ; where mass also exists .

18. ### Aqueous Idflat Earth skepticValued Senior Member

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NASA confirms a gyrating conclusion indeed. :runaway:

19. ### Pincho PaxtonBannedBanned

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Force is a variable word. I can push a door open, I can kick a door open, I can blow a door open, I can open it with a hose pipe, I could put an iron bar on it, and open it with a magnet.

Force-field is therefore not a scientific use of words. It could mean anything.

I know which force it is though.

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20. ### hansdaValued Senior Member

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Force can be generated by various ways . But the effect of various forces is same --- it causes a change in movement of a mass .
These are various examples of gravitational-force .

This is an example of magnetic-force .
Force-field doesnt mean magnetic-field or electrical-field . Is there any other type of field , which generates force ?

Is there any fifth type of force ?

21. ### Pincho PaxtonBannedBanned

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The fact that there is more than 1 kind of force makes most of your force-field posts nonsensical. Nobody knows which force you are referring to.

22. ### hansdaValued Senior Member

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Till now there are only four types of forces ; namely 1) Gravitational , 2) electromagnetic , 3) nuclear force strong and 4) nuclear force weak .

Out of these four types of forces , only electromagnetic-force is due to magnetism and electrical charge .

Rest types of forces are due to the mass . So, these types of forces can be considered as due to their force-fields .

23. ### AlexGLike nailing Jello to a treeValued Senior Member

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hansda makes up his own terms and definitions. I guess he likes the way they sound.