Time travel

[DarkLight 0]

Then I start to think: "What the hell are we doing here anyways, and if this all wouldn't exist then there would be nothing at all" It's just impossible to imagine "nothing at all", just...nothing. It's hard to explain, but if you get what I mean, and start thinking about it you're gonna get confused.

Same when thinking of death. Is there just 'nothing' when you die? Think of that 'nothing.' It wouldn't be 'nothing' as in lying and not hearing, feeling or seeing anything, it would be less than that. Hard to imagine.

Most ppl experience this "nothing" once in a while, sometimes it happens when you try to sleep. When you wake up the next day you won't remember any dreams. You have the feeling that you closed your eyes at night, and then right after that opened them. And then it was the next day.

The part where you were asleep is that nothing...

You remember nothing of it, no feelings, no thought, nothing...

[DarkLight 0]

Black Holes are a mystery that I would very much like to solve.

They are already solved, i've seen a documentary about it about one year ago. The documentary explained exactly what they were and how they work. Or at least, it explained most of it. Of course we cannot know everything. But a lot is already known about it...

They do exist, they absorb everything that's close to them, maybe with some luck, you can find a pic of a black hole absorbing something. Yes, those exist too!

[DarkLight 0]

About the black holes: http://science.howstuffworks.com/black-hole.htm

SHould help you, i didn't read it, not enough time.

[Postduifje 0]

They do exist, they absorb everything that's close to them, maybe with some luck, you can find a pic of a black hole absorbing something.  Yes, those exist too!

Hmm, I thought they existed only theoretical, and there was also a theory the centre of the universe was a black hole. But pictures...hmm, I doubt it

-Post

[DarkLight 0]

Read the link, i've sene pics of black holes absorbing stars and stuff like that. Dunno if you can fidn those on the link too...

[Tex -USMC- 0]

Well, you can't see a black hole, because- well, it's really really black. Of course everyone knows that not even light can escape from a blackhole worthy of the name. But what you can see is the stuff being sucked into a blackhole, so that allows you to make an accurate assumption as to where the black hole is.

[DarkLight 0]

@ July 10 2003,20:44)]Well, you can't see a black hole, because- well, it's really really black. Of course everyone knows that not even light can escape from a blackhole worthy of the name. But what you can see is the stuff being sucked into a blackhole, so that allows you to make an accurate assumption as to where the black hole is.

Hmmm, i seem to remember that you can see a black hole, of course you can't just see them when you look out of your window but with the right equipement i think it's possible!

Because they absorb the light they will look like a huge black dot, everything behind the dot is invisible for you because the light of that is being absorbed by the black hole. Result: The light won't make it to mother earth and all you see is a black dot.

[Tex -USMC- 0]

I think with an infrared telescope you could see it- with all that mass in such a small area, it must have a massive heat signature.

[Tamme 0]

Quote[/b] ]Most ppl experience this "nothing" once in a while, sometimes it happens when you try to sleep. When you wake up the next day you won't remember any dreams. You have the feeling that you closed your eyes at night, and then right after that opened them. And then it was the next day.

The part where you were asleep is that nothing...

You remember nothing of it, no feelings, no thought, nothing...

That has happened to me often. It's funny when I'm reading something and I just close my eyes for a second and wake up in the morning with the pages glued to my head..

[ran 0]

Most ppl experience this "nothing" once in a while, sometimes it happens when you try to sleep.  When you wake up the next day you won't remember any dreams.  You have the feeling that you closed your eyes at night, and then right after that opened them.  And then it was the next day.

The part where you were asleep is that nothing...

You remember nothing of it, no feelings, no thought, nothing...

that happens when you're given complete anesthesics

[Renagade 0]

@ July 11 2003,19:56)]I think with an infrared telescope you could see it- with all that mass in such a small area, it must have a massive heat signature.

If it captures heat wouldn`t it also suck in heat ??

Could a blackhole convert energy into matter?

What was the theory about going through the centre of a black hole?

[SPQR 0]

In the basis theory, any objet has to reach a certain velocity to escape from a planet, star, ... gravitic object. Not enough, you fall back to the ground, enough and you get to the stars.

Light is made of massless particles (and is also a wave) which has a velocity of 300.000 km/s.

So A black hole is in theory a so strong, heavt, gravitic object that even light can't escape.

We can see only light-reflective objects. If all light is absorbed, we can't see it directly.

There are several means to detect a black hole ; X-ray created from the destruction of matter by the black hole, the disk of matter spiraling around the gravitic monster accelerating and so getting hot, an abnormal velocity of systems around (using doppler effect),....

Now you have to know that in each galaxy (ours too) exists in its center hyper massive giant black hole, that helped a long time ago (life even wasn't a protein), to concentrate matters and gases around it in a reduced volume, then helping creating solar and planetary systems.

A black hole appears when a dying massive star crushing into itself, beyond its Schwarztshild radius.

[Tex -USMC- 0]

shit, forgot that infrared is simply a spectrum of light- and since light can't escape a black hole period, then that means that I'm an idiot

[denoir 0]

@ July 11 2003,19:44)]Well, you can't see a black hole, because- well, it's really really black. Of course everyone knows that not even light can escape from a blackhole worthy of the name.

Actually there have been measurements of radiation coming from a black hole. Steven Hawkins has done his main research on that. A black hole by definition has an infinite denisty so it's a singularity in the space time continuum. (It's like a sloped hole with infinite depth - things that get near it fall down the hole - and should not be able to bounce back off the bottom - since there is no bottom). So there should be no radiation, but there is.

To circumvent this Hawkins introduced the concept of imaginary time (imaginary as in imaginary number in mathematics). The imaginary time line is perpendicular to our normal time line.

His reasoning was quite simple: to escape the event horizon of the black hole, particles must travel faster than the speed of light. Time contractions/expansions are calculated through the usual relativistic factor: 1/sqrt(1-(v/c)^2). Now, if v (velocity) is greater than c (speed of light) we get that v/c>1 so 1- (v/c)^2 < 1 i.e a negative number. The square root of a negative number is an imaginary number and volia, you have imaginary time.

IMO this is a complete load of horseshit that has no physical relevance at all. For one thing the assumption that a black hole truly has infinite density i.e that it's a real singularity is very questionable.

Quote[/b] ]But what you can see is the stuff being sucked into a blackhole, so that allows you to make an accurate assumption as to where the black hole is.

I think the standard procedure for mapping black holes is by looking at the bending of light from stars with known positions. When the light passes in the neighbourhood of a black hole it bends towards it (well, actually it goes in a straight line but the black hole deforms space-time and light travels through space).

[Tex -USMC- 0]

IMO this is a complete load of horseshit that has no physical relevance at all. For one thing the assumption that a black hole truly has infinite density i.e that it's a real singularity is very questionable.

Maybe they aren't infinitely dense- just really really really dense (I know I'm getting all technical, but bear with me ). Isn't that good enough to cause a singular-ish effect in space-time?

[denoir 0]

That's what I think it is. It does have a huge density but not infinite. So it would be a very deep hole, but not endlessly deep. And then there is no problem with occasional high energy particles escaping it.

This is btw how it folds space:

The time deformation has an interesting effect. From the time reference of the black hole, objects that get within the event horizon are more or less instantaneously crash into it and get compressed almost infinitely. From the outside frame of reference however it looks like the objects is traveling towards the black horizon, slower and slower. At the limit of it, time will stand still (or almost still, depending if you believe that it's a true singularity or not).

[Tex -USMC- 0]

Which means that if you get sucked into a black hole, it will either be forever or nearly forever before you're finally sucked in.

[Schoeler 0]

@ July 11 2003,19:44)]Well, you can't see a black hole, because- well, it's really really black. Of course everyone knows that not even light can escape from a blackhole worthy of the name.

Actually there have been measurements of radiation coming from a black hole. Steven Hawkins has done his main research on that. A black hole by definition has an infinite denisty so it's a singularity in the space time continuum. (It's like a sloped hole with infinite depth - things that get near it fall down the hole - and should not be able to bounce back off the bottom - since there is no bottom). So there should be no radiation, but there is.

To circumvent this Hawkins introduced the concept of imaginary time (imaginary as in imaginary number in mathematics). The imaginary time line is perpendicular to our normal time line.

His reasoning was quite simple: to escape the event horizon of the black hole, particles must travel faster than the speed of light. Time contractions/expansions are calculated through the usual relativistic factor: 1/sqrt(1-(v/c)^2). Now, if v (velocity) is greater than c (speed of light) we get that v/c>1 so 1- (v/c)^2 < 1 i.e a negative number. The square root of a negative number is an imaginary number and volia, you have imaginary time.

IMO this is a complete load of horseshit that has no physical relevance at all. For one thing the assumption that a black hole truly has infinite density i.e that it's a real singularity is very questionable.

Quote[/b] ]But what you can see is the stuff being sucked into a blackhole, so that allows you to make an accurate assumption as to where the black hole is.

I think the standard procedure for mapping black holes is by looking at the bending of light from stars with known positions. When the light passes in the neighbourhood of a black hole it bends towards it (well, actually it goes in a straight line but the black hole deforms space-time and light travels through space).

Scientists look for bending light in the vicinity of black holes from what my brother told me. He was an astro-physicist, so he should know.

Oh, and light does have mass, its just insignificant in human terms, unless focused of course.

[Necromancer- 0]

Oh, and light does have mass, its just insignificant in human terms, unless focused of course.

of course.. or else gravity has no effect on it...

[Tamme 0]

I have this book about black holes. It's a good book with loads of pictures. It has everything about them, but I thought that most of it is just speculation that's why I asked.

[denoir 0]

@ July 12 2003,05:12)]Which means that if you get sucked into a black hole, it will either be forever or nearly forever before you're finally sucked in.

Nope. From your frame of reference it happens instantly.

Quote[/b] ]

Quote[/b] ]Oh, and light does have mass, its just insignificant in human terms, unless focused of course.

of course.. or else gravity has no effect on it...

No, no. Light does not have a mass. If it had even the smallest imaginable mass, it would require infinite energy to move it at the speed of light. Photons have energy, but not mass.

You are perhaps thinking of their relativistic mass. It's not mass however. Relativistic mass is just expressing the kinetic energy of a particle as a mass instead of energy. But it's not real classical mass in any way. Their rest mass is zero.

Gravity affects light because gravity is not an ordinary force. It deforms space-time. When light or anything else travels throught that deformed region of space, it will look as it's being affected by a force. It's not however. It's just taking a different route.

Edit: What is tha mass of a photon (explains better than I did)

[Phleep 0]

Photons have a momentum but not a mass (as with all null particles).

What is going to be interesting is that in the near future the first solar sail will be unfurled and several theories put to the test. There are many people who strongly believe it will work and many who strongly believe it won't. (ref. latest New Scientist).

I don't think it would be wise of me to continue at present being 0300 local time here and I'll say something dumb.

[DarkLight 0]

@ July 11 2003,05:19)]

IMO this is a complete load of horseshit that has no physical relevance at all. For one thing the assumption that a black hole truly has infinite density i.e that it's a real singularity is very questionable.

Maybe they aren't infinitely dense- just really really really dense (I know I'm getting all technical, but bear with me   ). Isn't that good enough to cause a singular-ish effect in space-time?

It's very strange that the word "infinite" exists, they say the space is neverending. But for us humans it's just impossible to understand.

How can something be infinite? Don't even try to think about that. I bet if you spend more than 10 minutes thinking about this, you'll feel the urge to bang your head into your computer...

Maybe some things are beyond what we think is possible, probable the same for black holes.

[Harnu 0]

How does a black hole 'fold' space, when it's just space.  There's nothing to fold  

Ohh or are we going into all the dimension crap when you mean that it 'folds' space? uhhhh

[Tamme 0]

@ July 12 2003,05:12)]Which means that if you get sucked into a black hole, it will either be forever or nearly forever before you're finally sucked in.

If you get sucked into a black hole. Time will seem normal to you, but your friends watching you from the spaceship will never see you cross the event horizon. Because in the event horizon time seems to stop and it will look like you will stay there floating forever.

If you want to survive the ride in to the black hole, you'd better choose one with 10 million suns mass. You would only feel some weak stretching that wouldn't be lethal. (sorry for the bad english)