Re: Space and The wonders/mysteries of The Universe

by halfwise Mon Feb 15, 2016 10:07 pm

No, gravity is NOT waves. It is the curvature of space caused by mass (according to the most recent fully accepted theory dating to 1916). If you wiggle the mass, the space will wiggle, causing waves. But you don't have to wiggle the mass. You'll still have gravity, but no waves.

by halfwise Mon Feb 15, 2016 10:16 pm

Why I couldn't have just said that from the beginning beats me...

by David H Mon Feb 15, 2016 10:20 pm

but what I mean is, they didn't know what gravity was, even though it fit theories, and now they know its waves

Gravity still is exactly what it always has been, a force that pulls objects with mass towards each other.

What Sir Isaac didn't suspect is that gravity's force isn't always exactly the same. Under certain conditions it "vibrates" a little, making a "sound" that can be "heard" across great distances if you know how to "listen" for it.

Now that we've "heard" it for the first time, the next job is to learn to understand it's "language".

by Mrs Figg Tue Feb 16, 2016 2:26 pm

its not waves then. its the word gravity in gravitational that foxdmuldered me.

by halfwise Tue Feb 16, 2016 3:30 pm

Saying gravity is waves is sort of like saying water is waves. Both can make waves, but water is not made of waves.

You jiggle your finger in water, you make water waves. You take an electric charge and jiggle it around, you make waves in the electric field which is light (often called electro-magnetic waves). You take a mass and jiggle it around, you make waves in the gravitational field which are gravity waves.

We've detected the gravitational equivalent of light.

by Mrs Figg Tue Feb 16, 2016 5:54 pm

so we still don't know what gravity is?

by halfwise Tue Feb 16, 2016 7:07 pm

I think nearly everyone is satisfied with saying it's the curvature of space (and time) caused by the presence of mass. You really can't go any deeper than the very fabric of the universe!

If it ever gets merged with quantum mechanics this simple vision will be distorted, but General Relativity is one of those theories that is so beautiful and fundamental it will never be abandoned - at the very least it will continue to be used side-by-side with any newer theories, just like Newton's mathematically simpler theory still is. Our most advanced theory of all the other forces (fantastically precise!) has nothing close to the elegance and conceptual simplicity of Einstein's theory of gravity.

After the pivotal measurements of starlight bending around the sun that led everyone to accept general relativity, someone asked Einstein how he'd feel if the experiment proved him wrong:

"Then I'd feel sorry for the good Lord, for nonetheless the theory is correct."

Most physicists these days would agree.

by David H Tue Feb 16, 2016 10:38 pm

Mrs Figg wrote:so we still don't know what gravity is?

{{{I do, but I'm not telling Razz

}}

by Mrs Figg Tue Feb 16, 2016 11:03 pm

how come theres no gravity in empty space? does it need mass to work? so what about gas, does that have mass? thinking about gas planets.

Question

by halfwise Wed Feb 17, 2016 1:45 am

There IS gravity in space. But you don't notice your own weight when falling, and orbits etc are all falling. What does this mean? If you are falling (maybe in an elevator which starts to fall so you don't have to worry about air blowing past you), and you take a coin out of your pocket and let go, it falls WITH YOU. So it seems to be floating beside you like there's no gravity. But of course there is gravity, it's just a trick of the situation.

So it SEEMS like there's no gravity in space when you are cooped up inside a spaceship and can't see how you are moving. To anybody watching you moving from outside it's obvious there IS gravity.

The fact that you don't feel gravity when falling (even though gravity obviously is making you fall) struck Einstein like a thunderbolt, and led him to his theory of gravity. It's such a fundamental experience that he realized gravity had to affect the fundamental nature of time and space.

All mass produces gravity (ie, curves space). But less massive things curve space less, so you may not notice it. Gas is made of atoms, so has mass. But they are spread out so the same volume of gas has less mass than you. Gas giants have the gas compressed, so much of the gas is more of a liquid.

by David H Wed Feb 17, 2016 6:47 am

Yeah you only feel gravity when you bump into something else. Remember the whale in Hitchhiker's Guide to the Galaxy? Space and The wonders/mysteries of The Universe - Page 9 18ua72i2ub6eijpg

Space and The wonders/mysteries of The Universe - Page 9 18ua72i2ub6eijpg

Each atom is a large gas body makes a small bit of gravity of its own that calls to other atoms, and slowly over billions of years they've pulled in more and more lost atoms from space, rather like sheep huddling into a flock.

As the flock gets bigger, the gravity of all the little atoms adds up, pulling in more and more sheep and making more and more pressure in the center of the flock until the sheep in the middle are getting crushed. At a certain point the sheep in the middle explode, and the flock becomes a star!

Space and The wonders/mysteries of The Universe - Page 9 Star

(OK, so maybe the analogy breaks down at a certain point..... Embarassed

)

by Lancebloke Wed Feb 17, 2016 7:53 am

But where did all the bits come from in the first place?

by Mrs Figg Wed Feb 17, 2016 1:38 pm

good question Lance. Very Happy

also how come there is more gravity on Earth then on the Moon? does it depend on size?

by halfwise Wed Feb 17, 2016 2:08 pm

It depends on mass and distance from the center (for a sphere). If you get far enough away from the earth (with a larger mass than the moon) you will feel the same gravity you would on the moon. If you could build a platform about 1.5 earth radii above the earth's surface, you could bounce around on there like on the moon.

Where did all the bits come from in the first place? That's almost in the realm of metaphysics. We do know since everything is currently flying apart that about 14.8 billion years ago it must have all been smashed together, and much of the current mass was probably in the form of pure energy. But where that smashed together ball of stuff came from in the first place? scratch

Pour yourself 4 or 5 strong drinks and start speculating.

by Mrs Figg Wed Feb 17, 2016 3:36 pm

its weird isn't it? the ball of stuff must have started sometime, but what started it, was there literally nothing before it? and how did stuff come from nothing, or has it always been there, as in infinite, but our brains cant get round infinite, and why did the stuff have to be molecules? what made it go bang. oh my brain is goggling. cyclops

by halfwise Wed Feb 17, 2016 3:56 pm

It definitely wasn't molecules when it started. Too hot - not even protons/neutrons!! It was all ripped up into quarks, gluons, and things like electrons and neutrinos. Probably even more ripped up into stuff we don't even know about yet.

by halfwise Sat Feb 20, 2016 9:20 pm

http://www.huffingtonpost.com/entry/apollo-10-astronauts-reported-unexplained-music-at-moon_us_56c80662e4b0928f5a6c0679?

by Mrs Figg Sun Feb 21, 2016 1:31 pm

you see, Mulder was right, there is heavenly music.

by chris63 Mon Mar 07, 2016 4:59 am

Space and The wonders/mysteries of The Universe - Page 9 Nh-northpolerotatedcontrast

You've never seen Pluto like this before! New enhanced color image shows ethereal scene with frozen canyons. Located in the north polar region, these canyons show researchers yet another story of the dwarf planet’s diversity of geological and compositional features. Some of the canyons also appear to represent evidence for an ancient period of tectonics. Details: http://go.nasa.gov/1QhGWVy

by David H Tue Mar 22, 2016 2:14 am

Hang on folks, we're dodging comets Shocked

Space and The wonders/mysteries of The Universe - Page 9 Two-comets

Meet comet 252P/LINEAR and comet P/2016 BA14: They may not sound like harbingers of doom that could devastate life on Earth, and that’s because they aren’t.

NASA and its grandly named Planetary Defense Office are being super chill about the comets, even though one is passing closer to Earth than all but two comets in recorded history.

Comet 252P/LINEAR will come within 3.3 million miles (5.2 million km) on Monday, March 21, and comet P/2016 BA14 will come a bit closer, passing within 2.2 million miles (3.5 million kilometers) on Tuesday, March 22.

That makes P/2016 BA14 the third-closest comet fly-by ever, after comet D/1770 L1 (Lexell) in 1770 and comet C/1983 H1 (IRAS-Araki-Alcock) in 1983, NASA said, in a statement that used the words “safe” or “safely” no less than five times.

Because the comets are in remarkably similar orbits, it’s possible that they are related. Comet P/2016 BA14 is about half the size of 252P/LINEAR, which is about 750 feet (230 meters) in size. That means it may be a fragment that was “calved” some time in the past. Astronomers thought the smaller sibling was an asteroid until they picked up a faint tail.

Both comets are too small to be seen with the naked eye, but can be spotted with powerful, professional-grade telescopes, NASA said.

http://qz.com/643269/twin-comets-are-passing-close-by-this-week-and-nasa-planetary-defense-is-not-concerned/

by azriel Tue Mar 22, 2016 8:19 am

by Mrs Figg Tue Mar 22, 2016 12:01 pm

by Pettytyrant101 Sun Apr 10, 2016 11:01 pm

{{Photo taken from a high altitude aircraft about 6 miles up of a rocket leaving earth}}}

Space and The wonders/mysteries of The Universe - Page 9 12919670_1148308315188166_2780715003945621002_n_zpssxmdcosd

Space and The wonders/mysteries of The Universe - Page 9 12919670_1148308315188166_2780715003945621002_n_zpssxmdcosd

by Eldorion Sun Apr 10, 2016 11:04 pm

Looks like a microscopic picture of a hair sticking up out of a carpet.

Pretty incredible, though.

by Bluebottle Mon Apr 11, 2016 7:59 am