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Author Topic: A question! (Astronomy and Physics)  (Read 3166 times)

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Offline VekseidTopic starter

A question! (Astronomy and Physics)
« on: November 29, 2007, 05:12:35 PM »
But darn it ask me History or Science questions and I bet I get THOSE right :P

Explain why, if an external observer will never see something fully cross the event horizon of a black hole, such an object exists?

Edit: Having been informed I worded the question badly, "How can a black hole exist if we don't see anything ever cross the event horizon?" is probably a better question.
« Last Edit: December 03, 2007, 07:57:21 AM by Vekseid »

Offline Sherona

Re: A question!
« Reply #1 on: November 29, 2007, 08:10:14 PM »
Ok great God of Elliquiy, Vekseid. You have stumped me with your vast intelligence, thus proving your far superior intellect. Please grace this poor ignorant person with the answer to this question that has been the cause of many google hits, and some pretty odd finds, filling her browser history.


Simple post:

I give up :P How do you know a black hole exists if you cant see something cross the event horizon?

Offline RubySlippers

Re: A question!
« Reply #2 on: November 29, 2007, 08:27:20 PM »
Well it is true one an object passes trhough a Black Holes event horizon it leaves our universe as far as anyone can tell. But we can see effects of a Black Hole such as when a star collapses into one the jet of energy being released and the gravitational forces at work on nearby objects. In fact as far as we can tell all large galaxies have a black hole in the center, a rather large one, we know we see their effects in neighboring galaxies in every case if they are large galaxies. So one can deduce they have some natural law effect in the balance of large steller events like galaxies perhaps similar to a star in a solar system since these are proportional to the galaxy size.

Offline Sherona

Re: A question!
« Reply #3 on: November 29, 2007, 08:30:21 PM »
Well it is true one an object passes trhough a Black Holes event horizon it leaves our universe as far as anyone can tell. But we can see effects of a Black Hole such as when a star collapses into one the jet of energy being released and the gravitational forces at work on nearby objects. In fact as far as we can tell all large galaxies have a black hole in the center, a rather large one, we know we see their effects in neighboring galaxies in every case if they are large galaxies. So one can deduce they have some natural law effect in the balance of large steller events like galaxies perhaps similar to a star in a solar system since these are proportional to the galaxy size.

already tried the answer of seeing the effects of the black hole and in essence 'seeing' the black hole...(been bouncing answers off him via private messages all evening..)

Offline VekseidTopic starter

Re: A question!
« Reply #4 on: November 29, 2007, 08:44:40 PM »
Okay, that was uncalled for :-p

How can black holes exist if you don't see anything fall into them?

If you look that sort of question up on Google you'll get a lot of mention about that last, final, insanely redshifted image of anything and everything that falls into a black hole actually being an illusion.  That is to say, what you are seeing is not actually the object itself, but the last photons it emitted, struggling to escape.

In slightly more complex terms, if you are shining a flashlight onto a mirror as it falls into the horizon, for a time, you will see the reflected light of the flashlight.  Eventually, however, the mirror gets too close to the event horizon, and photons are not physically capable of reaching the mirror any longer. They no longer bounce back, they just vanish into the hole.

This means that there is a definite point at which it is no longer possible to interact with an object falling into a black hole - at best, you can see its shadow.

Offline Sherona

Re: A question!
« Reply #5 on: November 30, 2007, 12:32:04 PM »
198 licks before I tasted Chocolate. This is direct licking, and not inserting (yes get the grins over with) so that no other direct temperature increase can be taken as a variable.


If the sun continues to burn up its fuel at a constant rate of speed, how long before it uses up all its fuel source?

Offline VekseidTopic starter

Re: A question! (Astronomy and Physics)
« Reply #6 on: November 30, 2007, 01:13:44 PM »
The answer depends on your definition of 'fuel' - the sun would run out of hydrogen in 80 billion years at its present rate. If it somehow kept consuming mass-energy, it would last over ten trillion years.

The Sun will eventually swell past Earth's orbit when it reaches the red giant phase. Why will Earth and Venus still survive?
« Last Edit: December 03, 2007, 07:57:05 AM by Vekseid »

Offline Sherona

Re: A question!
« Reply #7 on: November 30, 2007, 01:57:15 PM »
Answer to Vekseid's question:


http://www.dawn.com/2002/04/06/int17.htm

Simple answer, the earths orbit will not stay the same. As the sun swells it will continue to lose surface mass,

The pertinent results are these. In about 7.5bn years, the solar radius will grow to about 167m kms (compared to the present 0.7m). If the Earth remained at its present distance it would be enveloped, but a gradual migration to 185m kms will have occurred due to the solar mass loss.

That is the first red giant phase. Itís interesting to note that while the Earth will remain outside the sun, the latter will fill about half the sky.

The sun will then shrink before again fattening about 120m years later. In that epoch its radius will maximize at 172m kms, but our planet will have shifted outwards to 220m. The closest call is therefore in the first instance.


this is a copy paste, I am trusting this site's equations and mathematical calculations. I am Lazy.

A new Question to come.

Offline strangely made

Re: A question! (Astronomy and Physics)
« Reply #8 on: December 05, 2007, 07:21:12 PM »
Ok, posting this here because I was daft and put a question forward in the wrong section *facepalm*


In String theory is is possible to construct a string where the left-moving excitations think they live on a bosonic string propagating in D = 26 dimensions and the right-moving excitations think they belong to a superstring in D = 10 dimensions.

The mismatched 16 dimensions must be compactified on an even, self-dual lattice
How ever there are two possible even self-dual lattices in 16 dimensions, and it leads to two types of the heterotic string.

What are they?

Offline VekseidTopic starter

Re: A question! (Astronomy and Physics)
« Reply #9 on: December 06, 2007, 06:25:19 PM »
You know string theory?

I honestly have no idea, I can research terms but I've no real understanding of what they're talking about since I can never find the damned math.

Offline strangely made

Re: A question! (Astronomy and Physics)
« Reply #10 on: December 06, 2007, 06:36:52 PM »
I know the basics, I'm no Hawkins by any stretch of the imagination but I do like String theory. (He gets very rude when he drinks btw)

Do you want me to put the answer up? or wait to see if any one gets it?

Offline Sherona

Re: A question! (Astronomy and Physics)
« Reply #11 on: December 06, 2007, 06:46:54 PM »
I would put the answers up :D string theory is interesting but complex (for me atleast) ...*sighs* I guess I cant be considered a Hawkins either :P

Offline strangely made

Re: A question! (Astronomy and Physics)
« Reply #12 on: December 06, 2007, 07:09:50 PM »
Okey cokey,

There are two gauge groups and differ by 10 dimnesions. One gauge group is SO(32) (the HO string) (Special orthogonal group)
The other is E8◊E8 (the HE string) ( E8 being a simple Lie algebra formulated by Wilhelm Killing)
These two gauge groups also happen to be the only two anomaly-free gauge groups that can be coupled to the N = 1 supergravity in 10 dimensions other than U(1)496 and E8 ◊ U(1)248, which is suspected to lie in the swampland ( consistent-looking semiclassical effective field theories, which are actually inconsistent.) that surround the vast vacua of the string theory landscape .

Basically that's it...

Offline Sherona

Re: A question! (Astronomy and Physics)
« Reply #13 on: December 06, 2007, 07:10:41 PM »
Nice :) Really nice Question S. :)

Offline VekseidTopic starter

Re: A question! (Astronomy and Physics)
« Reply #14 on: December 06, 2007, 08:57:13 PM »
Well I was hoping for an answer I didn't have to look up every other word for... >_>

Aanyway, lessee.

Some theories about the expansion of the Universe run into a problem where this continued expansion must inevitably violate a fundamental law, if it were to continue unchecked. What is this fundamental law and what are some of the proposed solutions, either permitting the law's breaking or keeping in terms with the law?

Offline Question Mark

Re: A question! (Astronomy and Physics)
« Reply #15 on: March 10, 2008, 01:50:04 AM »
I think I can answer this without any research.  Here goes.

...

I got nothin'.  :/

Offline Mindhazingsquid

Re: A question! (Astronomy and Physics)
« Reply #16 on: March 19, 2008, 04:35:41 PM »
It's entropy, man.  The energy of the universe will eventually run out.  When that happens everything will collapse back in on itself and we'll have "the big crunch" and everything will start over again.

The cool (scuse the pun) thing is that while everything is collapsing in on itself, it's speculated time will reverse itself.  We could be in the middle of a big crunch RIGHT NOW, and we'd never know.

Offline VekseidTopic starter

Re: A question! (Astronomy and Physics)
« Reply #17 on: March 19, 2008, 04:38:17 PM »
To be more specific, in a Big Rip analysis of the Universe, eventually you have situations where regions with no entropy (ie, a single photon) occur, violating the laws of thermodynamics.

Offline Mindhazingsquid

Re: A question! (Astronomy and Physics)
« Reply #18 on: March 19, 2008, 08:33:07 PM »
Hmm, that must be new.

Offline Paradox

Re: A question! (Astronomy and Physics)
« Reply #19 on: June 13, 2008, 02:15:13 PM »
The intensity of light varies inversely as the square of the distance from the light source. If the distance from a light source is doubled, what will happen to the intensity of the light?

Offline Caeli

Re: A question! (Astronomy and Physics)
« Reply #20 on: June 13, 2008, 02:23:12 PM »
It's 4 times weaker. O.o

(1/2) squared = (1/2) x (1/2) = (1/4)

1/4 strength = 4 times weaker.

Offline Paradox

Re: A question! (Astronomy and Physics)
« Reply #21 on: June 13, 2008, 02:38:21 PM »
The corona of our Sun is the hottest layer, yet it is the farthest layer from the Sun's superheated core. With this in mind, how is it possible for it to be the hottest layer?

Offline Caeli


Offline Paradox

Re: A question! (Astronomy and Physics)
« Reply #23 on: June 13, 2008, 02:50:10 PM »
I already knew the answer Caeli. The point was for someone else to answer, then add a question of their own.

Offline Sherona

Re: A question! (Astronomy and Physics)
« Reply #24 on: June 13, 2008, 02:52:29 PM »
*weeees for more questions* Thankees Paradox :D Once I finish my housework and my tylenol kicks in I will work on providing an answer :)