h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

There's a great book I read in high school titled "White Holes." I don't remember the author. He proposed that black holes in other universes would appear as white holes in our universe. It makes sense - all that light has to go somewhere.

I think the jury's still out on the existence of White Holes. The general feling now (as I gather, but I could be wrong) is that they don't exist.

When light (or any energy, be it a blob of jello, a person, even a PC) gets sucked into a BH, then it just adds to the mass of the BH. Once it's in there, you can't tell what the energy looked like before it fell in.

How would light add mass? Photons?

I think the whole white hole thing comes from "well that matter and things has to go somewhere". But the question is can we actually see enough of the universe to make sense of where it might go? After all we haven't even found out where all the matter we think there should be has gone, or definitively decided whether the universe is acclerating, decelerating, standing still, or simply waiting for a bus.

Light has mass, which is carried (as you say) by photons.

Seems to me that a white hole couldn't exist. A black hole is just a VERY dense moderatly sized pebble, (about the size of one's fist) and as a result of it's density, it has an incredible amount of gravity, thus pulling things (such as light, and a large cow) into it. So far, no duh, right? Well then it is impossible for a "white hole" to exist because light cannot escape it to tell us that it is white. The only way to "see" a black hole is to look for a place where there is nothing. Such as on a radio telescope, the only evidence of a black hole would be a sudden gap in the picture.

A white hole - as earlier stated - is only a theory. But a white hole would be the opposite of a black hole (in theory), therefore we should have no problem seeing it. It'd be spouting out all the matter that the black hole in the other universe sucked in.

Black holes can be any size - not necessarily the size of one's fist. I've heard that they've actually found black holes at the molecular level.

Can the "white hole" theroy exist if we belive in local energy consavation(the fact that no energy can be made or destroid). Does consavation of energy apply for interactinon between different universes?

There's all sorts of ways to look at it - I've spent many late nights arguing/discussing black holes, white holes, and why does bread fall butter side down? Presumably, matter IS energy: e=mc2, right? So all this matter falling in the black hole emerges from the white hole as energy in this supposed other universe. So we presume that this other universe has black holes as well, which suck in matter and squirt it out on our side as energy. Or maybe, because energy becomes matter at twice the speed of light, they squirt it out as matter. Who knows? It's fun to talk about, though!

Oh, scuse me - energy becomes matter at the speed of light squared. Well, you know what I mean!

I agree that the existence of White Holes is facinating. I would like to point out, however, that Einstein proposed that a particular value of energy is equal to its mass multiplied by the speed of light. Energy, in simplified scientific jargon, is the amount of work required (whether realized or potentential) to cause change. Mass, of course, relates to the amount of matter that is actually measurable (or energy, as proven in the laboratory that photons have a consistent mass under the same stimuli). The speed of light of course, is C-squared (or 299,792,458 (m/s) meters per second multiplied by 299,792,458 (m/s) meters per second). So why didn't he use a constant value of 89,875,517,873,681,764.00 (plus some odd change)? Because C-squared represents acceleration - where the amount of work required (aka energy or force)is equal to the (nearly inconsequential mass) multiplied by 299,792,458 (m/s) in the very first second of that unit's (quark) existence, and should, by scientific convention, increase exponentially until it reaches critical mass/velocity.

So, what does this all really mean?

Only that, ultimately, it was Sir Isaac Newton's encounter with a falling apple (f=ma: force equals mass times acceleration) that originated the theory of relativity.

P.S, After all, when the apple drops, but no one is in the orchard to hear it fall; does it make a sound?

Of course it makes a sound, as a young boy I often recorded music from the radio with a microphone, even if I left the house and walked to the shops...it still recorded. Odd eh

But whether it's you or the recorder doing the listening, SOMETHING is still listening, and that makes the question moot. It's the Schrodinger's Cat thing--that the act of observing causes changes in the thing observed, no matter how you observe it--with your ears or with a recorder. Either way, we have no way of knowing whether an unobserved falling apple would make a noise because observing it to see would defeat the purpose.
-Rivaine

I've always thought that question was sort of zenny, and without an answer. Like 'what is the sound of one hand clapping?' The smart-a** answer is 'Cla.'

The scientific answer that is that sound is just our way of describing a waveform that falls within our decibel range. The waveform happens whether humans are there to perceive it or not.

So let's rephrase the question: If a tree falls in the forest, and the universe in which it falls in is devoid of lifeforms that would perceive the waveform the tree creates as it hits the ground as sound, would it make a sound? Then the answer would be no, but only if we're going to restrict ourselves to one universe of possibilities!

(In reply to post 9)

If the idea of a black hole is that nothing can escape from it, why would the fact that it exists in two or more universes change this fact? Near-infinite gravity is exactly that, regardless of what universe the observer is in, so wouldn't the matter would stay in a singularity regardless of its location?

The only answer I have (gleaned from reading science fiction) is that gravity and space-time and light are all tied in together and are part of the same thing. The higher the gravity, the slower the time goes. The faster you go, the slower the time goes. I think the White Hole guy was thinking that at the center of a black hole, gravity pressures would be more than this universe could comfortably hold, and would form an entrance into another galaxy - an anti-universe. Perhaps the place where tachyons come from. It's a neat idea - I'm not sure how much of it holds together when you apply real theory to it.

I've always thought that Einstein had it right - you can't go faster than light in this universe. What happens if you do? Well, you pop out in another universe.

But that theory assumes that the speed of light is only a constant for this universe. While I suppose it's possible, it wouldn't be much of a constant then, would it?

As with all the other laws of the universe - which aren't really laws, they're observations of the way things usually work and explanations for how they fit together - they're only applicable to our known universe. It's entirely plausible to me that in another universe, time/entropy runs backward.

Good point.
*walks off to contemplate*

In response to the Tree or apple falling and there are no lifeforms in the universe to percieve this event then there would be no sound. Sound is indeed a wave form. A wave that is formed when the gravitational kinetic energy turns into "heat" and "sound" energy. So yes, if there is nothing around to percieve the incident of the object smashing into the ground it would still make a "sound" because it is still emitting sound waves weather anything is there to hear it or not.

As for White Holes - There is no evidence to suggest that such things exist.

As for Black Holes - Yes, black holes do exist in extremely small sizes (perhaps molecular) but those are so small that they have virtually no impact on the nearest objects if any at all. Now think about this, once a person has passed beyond the even horizon time farther away from the event horizon will pass by INCREDIBLY fast, so it would be possible perhaps to view the end of the universe in a few minutes if it were possible to withstand the difference in gravitational forces acting on different parts of your body hence ripping your body into atomic dust.