SUMMARY: Theoretical physicist Dr. Lawrence M. Krauss from Case Western University and author of Hiding in the Mirror: The Mysterious Allure of Extra Dimensions, from Plato to String Theory and Beyond has agreed to answer questions from the Bad Astronomy/Universe Today forum. If you've got puzzling questions about physics, multiple dimensions, or any of his books, follow this link to the forum and post a question. We'll gather up the best questions and pass them along to Dr. Krauss to answer. I'll post his answers back in Universe Today when I get them.

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Dr. Krauss,

I attended your lecture at the Cleveland Museum on November 10, and wanted to ask this question during the book signing. I know you don't totally agree with String Theory, but my question has to due with that and multiple dimensions. If I am not mistaken String theory states that there needs to be an additional 11 dimensions. My question is; Why 11 dimensions? Why not 7 or 30 or 400?

--> Sam DiRocco

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http://firstlight.mvobservatory.com/

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Language Is A Virus From Outer Space, And When You Talk, You Just Make Sounds That, more or Less, Sync Up With Your Lips.

If there are multiple branes in the universe, in particular the two boundary branes in the ekpyrotic model, can the compactified dimensions in the two branes differ? The paper From Big Bang to Big Crunch by Khoury, Ovrut, Seiberg, Steinhardt and Turok (http://xxx.lanl.gov/PS_cache/hep-th/...08/0108187.pdf) seems to allow for the set of compactified dimensions to change in a collision between the end branes, but would the resulting metric in both end branes be identical?

Do you expect there are causal actions for probability's explanations, probably?

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Lighten up! This is a stellar board! Author: duh.

"The Sun, with all the planets revolving around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the universe to do..." Author: Galileo supposedly.

What are your thoughts on gravity being robust in other dimensions?

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Lighten up! This is a stellar board! Author: duh.

"The Sun, with all the planets revolving around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the universe to do..." Author: Galileo supposedly.

Dr. Krauss,

If cosmic strings exist, how would they effect the expansion of the universe? Could they be a major contributer of mass to Dark Matter? Thankyou.

Clear Skies,
SilverWing

Dr. Krauss, with tongue just a bit in cheek, why can't we say that an undetected photon (say, from cosmic microwave background radiation) is a perpetual motion machine? How much more than 13.7 billion years or so do we need to be called perpetual? :-)

Do atoms have memory?

Three dimensions through time I like. I can imagine how a mathematical discription of dimensions going from one to two to three leads arithmetically to infinite dimensions, but how to understand these dimensions in a real world way escapes me. Is there any help?

Dr. Krauss. I understand that the string theory is an attempt to understand
the structure of matter on a level more basic than the quark structure of the
proton and the neutron. Is the string theory now well established or is it still
just speculation?

Igor

Dr Krauss,

Can String Theory be tested and proved/disproved? If not, can we hope to have such tests by the end of the 21st century?

Hello, I saw a programme on Channel 4 (British T.V. channel) a while back about string theory. Now in it there was the question about why gravity was much weaker than the other 3 forces and a possible answer was that the gravity string was either a closed string or an open string (i.e. either a circle or a line) - I can't remember which way round it was and was different from the other forces in that they were of the other sort. Now the upshot of this difference was that gravity leaked from our universe into other universes and hence the reason was a lot weaker.

Well that got me thinking, if that was true then why couldn't gravity leak into our universe from other unoverses and if it did that's what dark matter was?

Of course there's always to chance that I picked up the what was said on the Channel 4 prog. wrongly and what I've said above is total rubbish? If not is it possible

Forgive me if I have this wrong. I have been reading about cosmology for 15 years and feel I still know precious little about it.

Anyway, if I am correct, equivalence tells us that gravity and acceleration are indistinguishable. As gravity is thought to be the consequence of the curvature of space-time, does that mean that accelerating objects cause space-time to curve? If so, is that what "frame dragging" is all about?

Dr. Krauss. I have friends who own an SUV that gets absurdly low mileage. I would like to know where I can get a gallon of inflationary spacetime, so that I can add a tiny bit to their gas tank, ...like drygas, with each fill-up. That way, since it expands carrying the matter along with it, indefinitely, and at superluminal velocity,..they can get about a million miles a gallon. (They drive a lot.).Thanks. Ciao. Pete.

P.S. When I asked this question while a visiting scientist at MIT, they laughed so hard they couldn't talk and tears came to their eyes in the particle physics labs. If you climb out on a limb,...somebody will saw it off. Pete.

Dr. Krauss. As a physics and chemistry teacher, I have given talks at American Association of Physics Teacher's Meetings, sometimes jointly held with the American Physical Society Meetings at Vassar College(92), Williams College(93), Harvard University(94), Norwich University(99), and Hartford, Pratt&Whitney Aircraft(2004). (Also talks at local Astronomy clubs in New England)Most of these have involved supernova theory in some capacity or other....their energetics, morphological characteristics of remnants, parity effects, pulsar characteristics, a solution to the Supernova Problem, neutrino forward-scattering, gravity waves, prompt neutrino bursts, galactic escape velocities for pulsars. Subliminal to these talks has been my hints at an underlying mechanism for pulsar ejections which is involved in a unified field theory I wrote some 23 years ago. ...simple, but valid. I would like to give a talk on that idea at Fermilab. Leon Lederman personally pushed for high school science teachers, and particularly physics teachers to be more collaborative with industrial-academic coalitions. Been there, done that. Boston College asked us to conduct a little piece of research ourselves to stay current. Been there,too,done that. This little talk will show the merits of encouraging such things...a high school physics teacher will reveal the only valid quantum theory of gravity yet to predict physical effects seen at six different major labs or institutions in the world. It's posted in these forums piecemeal, and you will note. I do not violate the precepts of SR or GR. I do not violate the Hierarchy of Conservation Laws. I obey Lorentz invariance, and hold others to it too. Gracious Bill Bertozzi, who ran the worlds largest particle physics group..the Nuclear Interaction Group...at MIT, said of my off-the-cuff talk ( I had 15 minutes to prepare)..on the relation of the results of the He-3 parity experiments at Bates to the parity effects in type-2 supernova pulsar ejections.."that's the kind of thinking we need going on around here(Bldg 26 lecture hall). So, I'm putting you on the spot, "Can you open the doors of Fermilab to the patient, genuine, radical thinking,near-solitary thinker, who has confounded them all? "
P.S.My letter to Leon Lederman went unanswered. My dad used to say ( I wish he was here for this as he used to letter the stalls for Man-O-War, Citation, etc..), put your money where your mouth is. Pick a horse. Buy a ticket. Go down to the rail. Feel the thundering herd go by. Watch the clods of dirt flying from their hooves. Listen to the heavy breathing of the steeds, and the cursing of the jockeys, the leather saddles creaking, and groaning. Watch the steaming, flaring nostrils....and scream em home! When you win at the track. It's simple. You cash your ticket. When you win in physics, it's not so clearcut. Ciao. Pete

PPS. In the New England forum I will give similar talk locally, as a memory to Al Rosenburg of Keene State for his help as chair of the Williams event.

What's beyond the Universe ? And what about the inner side ?

How is time "percieved" by a photon? Does time come to a halt in its frame of reference? How many dimensions would it move in?

Thanks

Doctor Krauss,

My question may seem a bit whacky.

Is there a simple experiment or observation to prove that the following scenario is not possible?

Rather than the current belief that gravity is an attractive force - gravity is actually a repulsive force.

Consider the following possibility:

There is a repulsive force (per unit volume) in the whole universe and/or possibly external.

This force interacts weakly with matter and is also weakly attenuated as it passes through matter.

Rather than objects being pulled to each other because of their inherent mass, they are actually pushed together. This happens because as the force interacts with matter and is attenuated by it, a “shadow effect” is created between objects causing an unequal “Push” in the volume between the objects. The “push” between the objects is smaller than the “push” from all other directions. Thus the objects come together.

Depending on the degree of interaction and attenuation between this “force” and matter, this “force” could possibly be extremely large.

Sound whacky? Sure, but is there an obvious way to show that it IS whacky?

Richard Dils

At the Big Bang, the three spatial dimensions “suddenly” began their explosive expansion. Was time also undergoing an explosive expansion of its own? Is this explosive expansion merely what we call the passage of time? Or was time not simply passing but changing the pace at which it passed? Scientists speculate that the universe underwent a period of rapid expansion and then slowed; would it mean anything different to say that time proceeded at a very lethargic pace and then sped up? Or it more than just definitional that time is viewed as a constant?

It seems to me that we only recognize spatial expansion because it is counteracted by gravity (keeping large things like galaxies and solar systems from expanding) and the other forces (keeping atoms, molecules and perhaps me from expanding). Is time similarly constrained by local forces?

Would it be correct to say that at the "moment" of the Big Bang a near-infinite mass was compressed into a single point, and, if so, wouldn’t that produce a nearly infinite warping of space? Is expansion the same as the un-warping of space as mass disperses? Or does the rapid dispersion of mass quickly pass the point where space is (at least with regard to its warping by gravity) for all intents and purposes flat, so that from here on the universe's expansion is independent of the lessening of the warping effect? Is this point reached in microseconds after the Big Bang... seconds... minutes... millions of years? Or is the Universe's expansion merely an eternal un-warping? (And could this be true of time as well?)

Finally, do you remember Kurt Vonnegut's "Slaughterhouse Five," where he suggests that the dimension of time's apparent uniqueness only exists because we are "stuck" in it, like a person tied to the front of a locomotive is stuck moving in one direction through space. Is it a reasonable conjecture that the uncontrollable passage of time is an artifact of our subjective perspective? Further, could the singular direction of entropy be due to our position with respect to the Big Bang, just as the singular direction of gravity is due to our position with respect to the center of the Earth? (Of course, the fact that the Big Bang has no location in space but only in time -- that the universe has no center but does have a beginning -- does mean that time is objectively unique in some ways.)

In short:
1. In the moment of the Big Bang, were time and space almost infinitely warped by the gravitational effect of this concentration of near-infinite mass, and was/is the expansion of the universe partly or completely the process of space (and perhaps time) un-warping and flattening out?
2. The idea that the universe underwent a phase of rapid expansion, which then slowed, seems to imply that spatial expansion is variable but that time proceeds at a constant rate. Is that in fact the case?
3. We only recognize expansion because it is not uniform; gravity and the other forces keep galaxies, atoms and me from expanding along with the universe. Is the expansion/passage of time similarly inhibited by these forces?
4. Time is certainly unique in that the Big Bang has a unique location in time but not in space. However, is it possible that part of time's apparent uniqueness -- the way it passes -- is a product of subjectivity.?

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"Now therefore, behold, the LORD hath put a lying spirit in the mouth of all these thy prophets" (1 Kings 22:23)

Dr. Krauss,

The second law of thermodynamics indicates that heat/energy flows from greater to lesser potential, ie increased entropy. Indicative of this is that stars and planets emit heat. Does this mean the ambient background energy content of the universe is increasing? If so, can the change be estimated/measured?

If the rate that the universe is expanding is accilerating is there a formula that describes the rate of expansion and does it resemble gravitational accileration?